From b0d60bfbb60cef1efd699a65e29a94487f8c7b1f Mon Sep 17 00:00:00 2001
From: Jonathan Corbet <corbet@lwn.net>
Date: Fri, 24 May 2019 14:52:01 -0600
Subject: kernel-doc: always name missing kerneldoc sections

The "no structured comments found" warning is not particularly useful if
there are several invocations, one of which is looking for something
wrong.  So if something specific has been requested, make it clear that
it's the one we weren't able to find.

Signed-off-by: Jonathan Corbet <corbet@lwn.net>
---
 scripts/kernel-doc | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

(limited to 'scripts')

diff --git a/scripts/kernel-doc b/scripts/kernel-doc
index 3350e498b4ce..c0cb41e65b9b 100755
--- a/scripts/kernel-doc
+++ b/scripts/kernel-doc
@@ -285,7 +285,7 @@ use constant {
     OUTPUT_INTERNAL     => 4, # output non-exported symbols
 };
 my $output_selection = OUTPUT_ALL;
-my $show_not_found = 0;
+my $show_not_found = 0;	# No longer used
 
 my @export_file_list;
 
@@ -435,7 +435,7 @@ while ($ARGV[0] =~ m/^--?(.*)/) {
     } elsif ($cmd eq 'enable-lineno') {
 	    $enable_lineno = 1;
     } elsif ($cmd eq 'show-not-found') {
-	$show_not_found = 1;
+	$show_not_found = 1;  # A no-op but don't fail
     } else {
 	# Unknown argument
         usage();
@@ -2163,12 +2163,14 @@ sub process_file($) {
     }
 
     # Make sure we got something interesting.
-    if ($initial_section_counter == $section_counter) {
-	if ($output_mode ne "none") {
-	    print STDERR "${file}:1: warning: no structured comments found\n";
+    if ($initial_section_counter == $section_counter && $
+	output_mode ne "none") {
+	if ($output_selection == OUTPUT_INCLUDE) {
+	    print STDERR "${file}:1: warning: '$_' not found\n"
+		for keys %function_table;
 	}
-	if (($output_selection == OUTPUT_INCLUDE) && ($show_not_found == 1)) {
-	    print STDERR "    Was looking for '$_'.\n" for keys %function_table;
+	else {
+	    print STDERR "${file}:1: warning: no structured comments found\n";
 	}
     }
 }
-- 
cgit v1.2.3


From 44f42165177e6c32f3a6aaceeaf7d9cd1c95595f Mon Sep 17 00:00:00 2001
From: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Date: Wed, 29 May 2019 20:09:24 -0300
Subject: scripts/sphinx-pre-install: make activate hint smarter

It is possible that multiple Sphinx virtualenvs are installed
on a given kernel tree. Change the logic to get the latest
version of those, as this is probably what the user wants.

Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
---
 scripts/sphinx-pre-install | 22 ++++++++++++++--------
 1 file changed, 14 insertions(+), 8 deletions(-)

(limited to 'scripts')

diff --git a/scripts/sphinx-pre-install b/scripts/sphinx-pre-install
index 8c2d1bcf2e02..11239eb29695 100755
--- a/scripts/sphinx-pre-install
+++ b/scripts/sphinx-pre-install
@@ -1,7 +1,7 @@
 #!/usr/bin/perl
 use strict;
 
-# Copyright (c) 2017 Mauro Carvalho Chehab <mchehab@kernel.org>
+# Copyright (c) 2017-2019 Mauro Carvalho Chehab <mchehab@kernel.org>
 #
 # This program is free software; you can redistribute it and/or
 # modify it under the terms of the GNU General Public License
@@ -15,6 +15,7 @@ use strict;
 
 my $conf = "Documentation/conf.py";
 my $requirement_file = "Documentation/sphinx/requirements.txt";
+my $virtenv_prefix = "sphinx_";
 
 #
 # Static vars
@@ -28,7 +29,8 @@ my $need_symlink = 0;
 my $need_sphinx = 0;
 my $rec_sphinx_upgrade = 0;
 my $install = "";
-my $virtenv_dir = "sphinx_";
+my $virtenv_dir = "";
+my $min_version;
 
 #
 # Command line arguments
@@ -229,7 +231,6 @@ sub get_sphinx_fname()
 
 sub check_sphinx()
 {
-	my $min_version;
 	my $rec_version;
 	my $cur_version;
 
@@ -255,7 +256,7 @@ sub check_sphinx()
 
 	die "Can't get recommended sphinx version from $requirement_file" if (!$min_version);
 
-	$virtenv_dir .= $rec_version;
+	$virtenv_dir = $virtenv_prefix . $rec_version;
 
 	my $sphinx = get_sphinx_fname();
 	return if ($sphinx eq "");
@@ -612,18 +613,23 @@ sub check_needs()
 		       which("sphinx-build-3");
 	}
 	if ($need_sphinx || $rec_sphinx_upgrade) {
-		my $activate = "$virtenv_dir/bin/activate";
-		if (-e "$ENV{'PWD'}/$activate") {
+		my $min_activate = "$ENV{'PWD'}/${virtenv_prefix}${min_version}/bin/activate";
+                my @activates = glob "$ENV{'PWD'}/${virtenv_prefix}*/bin/activate";
+
+                @activates = sort {$b cmp $a} @activates;
+
+		if (scalar @activates > 0 && $activates[0] ge $min_activate) {
 			printf "\nNeed to activate virtualenv with:\n";
-			printf "\t. $activate\n";
+			printf "\t. $activates[0]\n";
 		} else {
+			my $rec_activate = "$virtenv_dir/bin/activate";
 			my $virtualenv = findprog("virtualenv-3");
 			$virtualenv = findprog("virtualenv-3.5") if (!$virtualenv);
 			$virtualenv = findprog("virtualenv") if (!$virtualenv);
 			$virtualenv = "virtualenv" if (!$virtualenv);
 
 			printf "\t$virtualenv $virtenv_dir\n";
-			printf "\t. $activate\n";
+			printf "\t. $rec_activate\n";
 			printf "\tpip install -r $requirement_file\n";
 
 			$need++ if (!$rec_sphinx_upgrade);
-- 
cgit v1.2.3


From c4c562defedb7634a717293a5192071983e79781 Mon Sep 17 00:00:00 2001
From: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Date: Wed, 29 May 2019 20:09:25 -0300
Subject: scripts/sphinx-pre-install: get rid of RHEL7 explicity check

RHEL8 was already launched. This test won't get it, and will
do the wrong thing. Ok, we could fix it, but now we check
Sphinx version to ensure that it matches the minimal (1.3),
so there's no need for an explicit check there.

Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
---
 scripts/sphinx-pre-install | 13 -------------
 1 file changed, 13 deletions(-)

(limited to 'scripts')

diff --git a/scripts/sphinx-pre-install b/scripts/sphinx-pre-install
index 11239eb29695..ded3e2ef3f8d 100755
--- a/scripts/sphinx-pre-install
+++ b/scripts/sphinx-pre-install
@@ -581,19 +581,6 @@ sub check_needs()
 		print "Unknown OS\n";
 	}
 
-	# RHEL 7.x and clones have Sphinx version 1.1.x and incomplete texlive
-	if (($system_release =~ /Red Hat Enterprise Linux/) ||
-	    ($system_release =~ /CentOS/) ||
-	    ($system_release =~ /Scientific Linux/) ||
-	    ($system_release =~ /Oracle Linux Server/)) {
-		$virtualenv = 1;
-		$pdf = 0;
-
-		printf("NOTE: On this distro, Sphinx and TexLive shipped versions are incompatible\n");
-		printf("with doc build. So, use Sphinx via a Python virtual environment.\n\n");
-		printf("This script can't install a TexLive version that would provide PDF.\n");
-	}
-
 	# Check for needed programs/tools
 	check_sphinx();
 	check_perl_module("Pod::Usage", 0);
-- 
cgit v1.2.3


From 9b88ad5464af1bf7228991f1c46a9a13484790a4 Mon Sep 17 00:00:00 2001
From: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Date: Wed, 29 May 2019 20:09:26 -0300
Subject: scripts/sphinx-pre-install: always check if version is compatible
 with build

Call the script every time a make docs target is selected, on
a simplified check mode.

With this change, the script will set two vars:

$min_version - obtained from `needs_sphinx` var inside
	       conf.py (currently, '1.3')

$rec_version - obtained from sphinx/requirements.txt.

With those changes, a target like "make htmldocs" will do:

1) If no sphinx-build/sphinx-build3 is found, it will run
   the script on normal mode as before, checking for all
   system dependencies and providing install hints for the
   needed programs and will abort the build;

2) If no sphinx-build/sphinx-build3 is found, but there is
   a sphinx_${VER}/bin/activate file, and if
   ${VER} >= $min_version (string comparation), it will
   run in full mode, and will recommend to activate the
   virtualenv. If there are multiple virtualenvs, it
   will string sort the versions, recommending the
   highest version and will abort the build;

3) If Sphinx is detected but has a version lower than
   $min_version, it will run in full mode - with will
   recommend creating a virtual env using sphinx/requirements.txt,
   and will abort the build.

4) If Sphinx is detected and version is lower than
   $rec_version, it will run in full mode and will
   recommend creating a virtual env using sphinx/requirements.txt.

   In this case, it **won't** abort the build.

5) If Sphinx is detected and version is equal or righer than
   $rec_version it will return just after detecting the
   version ("quick mode"), not checking if are there any
   missing dependencies.

Just like before, if one wants to install Sphinx from the
distro, it has to call the script manually and use `--no-virtualenv`
argument to get the hints for his OS:

    You should run:

	sudo dnf install -y python3-sphinx python3-sphinx_rtd_theme

While here, add a small help for the three optional arguments
for the script.

Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
---
 Documentation/Makefile     |  5 +++++
 scripts/sphinx-pre-install | 40 +++++++++++++++++++++++++++-------------
 2 files changed, 32 insertions(+), 13 deletions(-)

(limited to 'scripts')

diff --git a/Documentation/Makefile b/Documentation/Makefile
index e889e7cb8511..380e24053d6f 100644
--- a/Documentation/Makefile
+++ b/Documentation/Makefile
@@ -70,12 +70,14 @@ quiet_cmd_sphinx = SPHINX  $@ --> file://$(abspath $(BUILDDIR)/$3/$4)
 	$(abspath $(BUILDDIR)/$3/$4)
 
 htmldocs:
+	@./scripts/sphinx-pre-install --version-check
 	@+$(foreach var,$(SPHINXDIRS),$(call loop_cmd,sphinx,html,$(var),,$(var)))
 
 linkcheckdocs:
 	@$(foreach var,$(SPHINXDIRS),$(call loop_cmd,sphinx,linkcheck,$(var),,$(var)))
 
 latexdocs:
+	@./scripts/sphinx-pre-install --version-check
 	@+$(foreach var,$(SPHINXDIRS),$(call loop_cmd,sphinx,latex,$(var),latex,$(var)))
 
 ifeq ($(HAVE_PDFLATEX),0)
@@ -87,14 +89,17 @@ pdfdocs:
 else # HAVE_PDFLATEX
 
 pdfdocs: latexdocs
+	@./scripts/sphinx-pre-install --version-check
 	$(foreach var,$(SPHINXDIRS), $(MAKE) PDFLATEX="$(PDFLATEX)" LATEXOPTS="$(LATEXOPTS)" -C $(BUILDDIR)/$(var)/latex || exit;)
 
 endif # HAVE_PDFLATEX
 
 epubdocs:
+	@./scripts/sphinx-pre-install --version-check
 	@+$(foreach var,$(SPHINXDIRS),$(call loop_cmd,sphinx,epub,$(var),epub,$(var)))
 
 xmldocs:
+	@./scripts/sphinx-pre-install --version-check
 	@+$(foreach var,$(SPHINXDIRS),$(call loop_cmd,sphinx,xml,$(var),xml,$(var)))
 
 endif # HAVE_SPHINX
diff --git a/scripts/sphinx-pre-install b/scripts/sphinx-pre-install
index ded3e2ef3f8d..f001fc2fcf12 100755
--- a/scripts/sphinx-pre-install
+++ b/scripts/sphinx-pre-install
@@ -38,6 +38,7 @@ my $min_version;
 
 my $pdf = 1;
 my $virtualenv = 1;
+my $version_check = 0;
 
 #
 # List of required texlive packages on Fedora and OpenSuse
@@ -277,20 +278,22 @@ sub check_sphinx()
 
 	die "$sphinx didn't return its version" if (!$cur_version);
 
-	printf "Sphinx version %s (minimal: %s, recommended >= %s)\n",
-		$cur_version, $min_version, $rec_version;
-
 	if ($cur_version lt $min_version) {
-		print "Warning: Sphinx version should be >= $min_version\n\n";
+		printf "ERROR: Sphinx version is %s. It should be >= %s (recommended >= %s)\n",
+		       $cur_version, $min_version, $rec_version;;
 		$need_sphinx = 1;
 		return;
 	}
 
 	if ($cur_version lt $rec_version) {
+		printf "Sphinx version %s\n", $cur_version;
 		print "Warning: It is recommended at least Sphinx version $rec_version.\n";
-		print "         To upgrade, use:\n\n";
 		$rec_sphinx_upgrade = 1;
+		return;
 	}
+
+	# On version check mode, just assume Sphinx has all mandatory deps
+	exit (0) if ($version_check);
 }
 
 #
@@ -575,14 +578,18 @@ sub check_distros()
 
 sub check_needs()
 {
+	# Check for needed programs/tools
+	check_sphinx();
+
 	if ($system_release) {
-		print "Detected OS: $system_release.\n";
+		print "Detected OS: $system_release.\n\n";
 	} else {
-		print "Unknown OS\n";
+		print "Unknown OS\n\n";
 	}
 
+	print "To upgrade Sphinx, use:\n\n" if ($rec_sphinx_upgrade);
+
 	# Check for needed programs/tools
-	check_sphinx();
 	check_perl_module("Pod::Usage", 0);
 	check_program("make", 0);
 	check_program("gcc", 0);
@@ -601,13 +608,14 @@ sub check_needs()
 	}
 	if ($need_sphinx || $rec_sphinx_upgrade) {
 		my $min_activate = "$ENV{'PWD'}/${virtenv_prefix}${min_version}/bin/activate";
-                my @activates = glob "$ENV{'PWD'}/${virtenv_prefix}*/bin/activate";
+		my @activates = glob "$ENV{'PWD'}/${virtenv_prefix}*/bin/activate";
 
-                @activates = sort {$b cmp $a} @activates;
+		@activates = sort {$b cmp $a} @activates;
 
-		if (scalar @activates > 0 && $activates[0] ge $min_activate) {
-			printf "\nNeed to activate virtualenv with:\n";
+		if ($need_sphinx && scalar @activates > 0 && $activates[0] ge $min_activate) {
+			printf "\nNeed to activate a compatible Sphinx version on virtualenv with:\n";
 			printf "\t. $activates[0]\n";
+			exit (1);
 		} else {
 			my $rec_activate = "$virtenv_dir/bin/activate";
 			my $virtualenv = findprog("virtualenv-3");
@@ -646,8 +654,14 @@ while (@ARGV) {
 		$virtualenv = 0;
 	} elsif ($arg eq "--no-pdf"){
 		$pdf = 0;
+	} elsif ($arg eq "--version-check"){
+		$version_check = 1;
 	} else {
-		print "Usage:\n\t$0 <--no-virtualenv> <--no-pdf>\n\n";
+		print "Usage:\n\t$0 <--no-virtualenv> <--no-pdf> <--version-check>\n\n";
+		print "Where:\n";
+		print "\t--no-virtualenv\t- Recommend installing Sphinx instead of using a virtualenv\n";
+		print "\t--version-check\t- if version is compatible, don't check for missing dependencies\n";
+		print "\t--no-pdf\t- don't check for dependencies required to build PDF docs\n\n";
 		exit -1;
 	}
 }
-- 
cgit v1.2.3


From 9e78e7fc0b20bcc0d5599f71d297b6fa1a2e7c5f Mon Sep 17 00:00:00 2001
From: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Date: Wed, 29 May 2019 20:09:27 -0300
Subject: scripts/documentation-file-ref-check: better handle translations

Only seek for translation renames inside the translation
directory.

Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
---
 scripts/documentation-file-ref-check | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

(limited to 'scripts')

diff --git a/scripts/documentation-file-ref-check b/scripts/documentation-file-ref-check
index 63e9542656f1..6b622b88f4cf 100755
--- a/scripts/documentation-file-ref-check
+++ b/scripts/documentation-file-ref-check
@@ -141,6 +141,10 @@ print "Auto-fixing broken references. Please double-check the results\n";
 foreach my $ref (keys %broken_ref) {
 	my $new =$ref;
 
+	my $basedir = ".";
+	# On translations, only seek inside the translations directory
+	$basedir  = $1 if ($ref =~ m,(Documentation/translations/[^/]+),);
+
 	# get just the basename
 	$new =~ s,.*/,,;
 
@@ -161,18 +165,18 @@ foreach my $ref (keys %broken_ref) {
 	# usual reason for breakage: file renamed to .rst
 	if (!$f) {
 		$new =~ s/\.txt$/.rst/;
-		$f=qx(find . -iname $new) if ($new);
+		$f=qx(find $basedir -iname $new) if ($new);
 	}
 
 	# usual reason for breakage: use dash or underline
 	if (!$f) {
 		$new =~ s/[-_]/[-_]/g;
-		$f=qx(find . -iname $new) if ($new);
+		$f=qx(find $basedir -iname $new) if ($new);
 	}
 
 	# Wild guess: seek for the same name on another place
 	if (!$f) {
-		$f = qx(find . -iname $new) if ($new);
+		$f = qx(find $basedir -iname $new) if ($new);
 	}
 
 	my @find = split /\s+/, $f;
-- 
cgit v1.2.3


From aeaacbfed853c17b8ac5e73c21f54d7f0805d899 Mon Sep 17 00:00:00 2001
From: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Date: Wed, 29 May 2019 20:09:28 -0300
Subject: scripts/documentation-file-ref-check: exclude false-positives

There are at least two cases where a documentation file was gone
for good, but the text still mentions it:

1) drivers/vhost/vhost.c:
   the reference for Documentation/virtual/lguest/lguest.c is just
   to give credits to the original work that vhost replaced;

2) Documentation/scsi/scsi_mid_low_api.txt:
   It gives credit and mentions the old Documentation/Configure.help
   file that used to be part of Kernel 2.4.x

As we don't want to keep the script to keep pinpoint to those
every time, let's add a logic at the script to allow it to ignore
valid false-positives like the above.

Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
---
 scripts/documentation-file-ref-check | 13 +++++++++++++
 1 file changed, 13 insertions(+)

(limited to 'scripts')

diff --git a/scripts/documentation-file-ref-check b/scripts/documentation-file-ref-check
index 6b622b88f4cf..05235775cc71 100755
--- a/scripts/documentation-file-ref-check
+++ b/scripts/documentation-file-ref-check
@@ -8,6 +8,14 @@ use warnings;
 use strict;
 use Getopt::Long qw(:config no_auto_abbrev);
 
+# NOTE: only add things here when the file was gone, but the text wants
+# to mention a past documentation file, for example, to give credits for
+# the original work.
+my %false_positives = (
+	"Documentation/scsi/scsi_mid_low_api.txt" => "Documentation/Configure.help",
+	"drivers/vhost/vhost.c" => "Documentation/virtual/lguest/lguest.c",
+);
+
 my $scriptname = $0;
 $scriptname =~ s,.*/([^/]+/),$1,;
 
@@ -122,6 +130,11 @@ while (<IN>) {
 			next if (grep -e, glob("$path/$ref $path/$fulref"));
 		}
 
+		# Discard known false-positives
+		if (defined($false_positives{$f})) {
+			next if ($false_positives{$f} eq $fulref);
+		}
+
 		if ($fix) {
 			if (!($ref =~ m/(scripts|Kconfig|Kbuild)/)) {
 				$broken_ref{$ref}++;
-- 
cgit v1.2.3


From 4904aeed9f686c90dba72980f0067ac1a7dbbfb6 Mon Sep 17 00:00:00 2001
From: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Date: Wed, 29 May 2019 20:09:29 -0300
Subject: scripts/documentation-file-ref-check: improve tools ref handling

There's a false positive on perf/util:

	tools/perf/util/s390-cpumsf.c: Documentation/perf.data-file-format.txt

The file is there at tools/perf/Documentation/, but the logic
with detects relative documentation references inside tools is
not capable of detecting it.

So, improve it.

Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
---
 scripts/documentation-file-ref-check | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

(limited to 'scripts')

diff --git a/scripts/documentation-file-ref-check b/scripts/documentation-file-ref-check
index 05235775cc71..5d775ca7469b 100755
--- a/scripts/documentation-file-ref-check
+++ b/scripts/documentation-file-ref-check
@@ -127,7 +127,7 @@ while (<IN>) {
 		if ($f =~ m/tools/) {
 			my $path = $f;
 			$path =~ s,(.*)/.*,$1,;
-			next if (grep -e, glob("$path/$ref $path/$fulref"));
+			next if (grep -e, glob("$path/$ref $path/../$ref $path/$fulref"));
 		}
 
 		# Discard known false-positives
-- 
cgit v1.2.3


From 0ca862e6f1c7e58e4eb9758fdb09255e6104d6a0 Mon Sep 17 00:00:00 2001
From: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Date: Wed, 29 May 2019 20:09:30 -0300
Subject: scripts/documentation-file-ref-check: teach about .txt -> .yaml
 renames

At DT, files are being renamed to jason. Teach the script how to
handle such renames when used in fix mode.

Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
---
 scripts/documentation-file-ref-check | 19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)

(limited to 'scripts')

diff --git a/scripts/documentation-file-ref-check b/scripts/documentation-file-ref-check
index 5d775ca7469b..ff16db269079 100755
--- a/scripts/documentation-file-ref-check
+++ b/scripts/documentation-file-ref-check
@@ -165,13 +165,22 @@ foreach my $ref (keys %broken_ref) {
 
 	# usual reason for breakage: DT file moved around
 	if ($ref =~ /devicetree/) {
-		my $search = $new;
-		$search =~ s,^.*/,,;
-		$f = qx(find Documentation/devicetree/ -iname "*$search*") if ($search);
+		# usual reason for breakage: DT file renamed to .yaml
 		if (!$f) {
-			# Manufacturer name may have changed
-			$search =~ s/^.*,//;
+			my $new_ref = $ref;
+			$new_ref =~ s/\.txt$/.yaml/;
+			$f=$new_ref if (-f $new_ref);
+		}
+
+		if (!$f) {
+			my $search = $new;
+			$search =~ s,^.*/,,;
 			$f = qx(find Documentation/devicetree/ -iname "*$search*") if ($search);
+			if (!$f) {
+				# Manufacturer name may have changed
+				$search =~ s/^.*,//;
+				$f = qx(find Documentation/devicetree/ -iname "*$search*") if ($search);
+			}
 		}
 	}
 
-- 
cgit v1.2.3


From b1663d7e3a7961fc45262fd68a89253f2803036c Mon Sep 17 00:00:00 2001
From: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Date: Tue, 4 Jun 2019 09:26:27 -0300
Subject: docs: Kbuild/Makefile: allow check for missing docs at build time

While this doesn't make sense for production Kernels, in order to
avoid regressions when documents are touched, let's add a
check target at the make file.

Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
---
 Documentation/Kconfig                | 13 +++++++++++++
 Documentation/Makefile               |  5 +++++
 Kconfig                              |  2 ++
 scripts/documentation-file-ref-check |  9 +++++++++
 4 files changed, 29 insertions(+)
 create mode 100644 Documentation/Kconfig

(limited to 'scripts')

diff --git a/Documentation/Kconfig b/Documentation/Kconfig
new file mode 100644
index 000000000000..66046fa1c341
--- /dev/null
+++ b/Documentation/Kconfig
@@ -0,0 +1,13 @@
+config WARN_MISSING_DOCUMENTS
+
+	bool "Warn if there's a missing documentation file"
+	depends on COMPILE_TEST
+	help
+	   It is not uncommon that a document gets renamed.
+	   This option makes the Kernel to check for missing dependencies,
+	   warning when something is missing. Works only if the Kernel
+	   is built from a git tree.
+
+	   If unsure, select 'N'.
+
+
diff --git a/Documentation/Makefile b/Documentation/Makefile
index 2df0789f90b7..e145e4db508b 100644
--- a/Documentation/Makefile
+++ b/Documentation/Makefile
@@ -4,6 +4,11 @@
 
 subdir-y := devicetree/bindings/
 
+# Check for broken documentation file references
+ifeq ($(CONFIG_WARN_MISSING_DOCUMENTS),y)
+$(shell $(srctree)/scripts/documentation-file-ref-check --warn)
+endif
+
 # You can set these variables from the command line.
 SPHINXBUILD   = sphinx-build
 SPHINXOPTS    =
diff --git a/Kconfig b/Kconfig
index 48a80beab685..990b0c390dfc 100644
--- a/Kconfig
+++ b/Kconfig
@@ -30,3 +30,5 @@ source "crypto/Kconfig"
 source "lib/Kconfig"
 
 source "lib/Kconfig.debug"
+
+source "Documentation/Kconfig"
diff --git a/scripts/documentation-file-ref-check b/scripts/documentation-file-ref-check
index ff16db269079..440227bb55a9 100755
--- a/scripts/documentation-file-ref-check
+++ b/scripts/documentation-file-ref-check
@@ -22,9 +22,16 @@ $scriptname =~ s,.*/([^/]+/),$1,;
 # Parse arguments
 my $help = 0;
 my $fix = 0;
+my $warn = 0;
+
+if (! -d ".git") {
+	printf "Warning: can't check if file exists, as this is not a git tree";
+	exit 0;
+}
 
 GetOptions(
 	'fix' => \$fix,
+	'warn' => \$warn,
 	'h|help|usage' => \$help,
 );
 
@@ -139,6 +146,8 @@ while (<IN>) {
 			if (!($ref =~ m/(scripts|Kconfig|Kbuild)/)) {
 				$broken_ref{$ref}++;
 			}
+		} elsif ($warn) {
+			print STDERR "Warning: $f references a file that doesn't exist: $fulref\n";
 		} else {
 			print STDERR "$f: $fulref\n";
 		}
-- 
cgit v1.2.3


From 54002b56b04bc83f8961c8751f6bfef07461d587 Mon Sep 17 00:00:00 2001
From: Bjorn Helgaas <bhelgaas@google.com>
Date: Thu, 30 May 2019 16:59:14 -0500
Subject: scripts/sphinx-pre-install: fix "dependenties" typo

Fix typo ("dependenties" for "dependencies").

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
---
 scripts/sphinx-pre-install | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

(limited to 'scripts')

diff --git a/scripts/sphinx-pre-install b/scripts/sphinx-pre-install
index f001fc2fcf12..158f522f12ed 100755
--- a/scripts/sphinx-pre-install
+++ b/scripts/sphinx-pre-install
@@ -632,7 +632,7 @@ sub check_needs()
 	}
 	printf "\n";
 
-	print "All optional dependenties are met.\n" if (!$optional);
+	print "All optional dependencies are met.\n" if (!$optional);
 
 	if ($need == 1) {
 		die "Can't build as $need mandatory dependency is missing";
-- 
cgit v1.2.3


From cd238effefa28fac177e51dcf5e9d1a8b59c3c6b Mon Sep 17 00:00:00 2001
From: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Date: Wed, 12 Jun 2019 14:52:48 -0300
Subject: docs: kbuild: convert docs to ReST and rename to *.rst

The kbuild documentation clearly shows that the documents
there are written at different times: some use markdown,
some use their own peculiar logic to split sections.

Convert everything to ReST without affecting too much
the author's style and avoiding adding uneeded markups.

The conversion is actually:
  - add blank lines and identation in order to identify paragraphs;
  - fix tables markups;
  - add some lists markups;
  - mark literal blocks;
  - adjust title markups.

At its new index.rst, let's add a :orphan: while this is not linked to
the main index.rst file, in order to avoid build warnings.

Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
---
 Documentation/admin-guide/README.rst               |    2 +-
 Documentation/kbuild/headers_install.rst           |   51 +
 Documentation/kbuild/headers_install.txt           |   50 -
 Documentation/kbuild/index.rst                     |   27 +
 Documentation/kbuild/issues.rst                    |   11 +
 Documentation/kbuild/kbuild.rst                    |  265 ++++
 Documentation/kbuild/kbuild.txt                    |  248 ----
 Documentation/kbuild/kconfig-language.rst          |  689 +++++++++
 Documentation/kbuild/kconfig-language.txt          |  669 ---------
 Documentation/kbuild/kconfig-macro-language.rst    |  247 ++++
 Documentation/kbuild/kconfig-macro-language.txt    |  242 ----
 Documentation/kbuild/kconfig.rst                   |  300 ++++
 Documentation/kbuild/kconfig.txt                   |  272 ----
 Documentation/kbuild/makefiles.rst                 | 1509 ++++++++++++++++++++
 Documentation/kbuild/makefiles.txt                 | 1369 ------------------
 Documentation/kbuild/modules.rst                   |  571 ++++++++
 Documentation/kbuild/modules.txt                   |  541 -------
 Documentation/kernel-hacking/hacking.rst           |    4 +-
 Documentation/process/coding-style.rst             |    2 +-
 Documentation/process/submit-checklist.rst         |    2 +-
 .../translations/it_IT/kernel-hacking/hacking.rst  |    4 +-
 .../translations/it_IT/process/coding-style.rst    |    2 +-
 .../it_IT/process/submit-checklist.rst             |    2 +-
 .../translations/zh_CN/process/coding-style.rst    |    2 +-
 .../zh_CN/process/submit-checklist.rst             |    2 +-
 Kconfig                                            |    2 +-
 arch/arc/plat-eznps/Kconfig                        |    2 +-
 arch/c6x/Kconfig                                   |    2 +-
 arch/microblaze/Kconfig.debug                      |    2 +-
 arch/microblaze/Kconfig.platform                   |    2 +-
 arch/nds32/Kconfig                                 |    2 +-
 arch/openrisc/Kconfig                              |    2 +-
 arch/powerpc/sysdev/Kconfig                        |    2 +-
 arch/riscv/Kconfig                                 |    2 +-
 drivers/auxdisplay/Kconfig                         |    2 +-
 drivers/firmware/Kconfig                           |    2 +-
 drivers/mtd/devices/Kconfig                        |    2 +-
 drivers/net/ethernet/smsc/Kconfig                  |    6 +-
 drivers/net/wireless/intel/iwlegacy/Kconfig        |    4 +-
 drivers/net/wireless/intel/iwlwifi/Kconfig         |    2 +-
 drivers/parport/Kconfig                            |    2 +-
 drivers/scsi/Kconfig                               |    4 +-
 drivers/staging/sm750fb/Kconfig                    |    2 +-
 drivers/usb/misc/Kconfig                           |    4 +-
 drivers/video/fbdev/Kconfig                        |   14 +-
 net/bridge/netfilter/Kconfig                       |    2 +-
 net/ipv4/netfilter/Kconfig                         |    2 +-
 net/ipv6/netfilter/Kconfig                         |    2 +-
 net/netfilter/Kconfig                              |   16 +-
 net/tipc/Kconfig                                   |    2 +-
 scripts/Kbuild.include                             |    4 +-
 scripts/Makefile.host                              |    2 +-
 scripts/kconfig/symbol.c                           |    2 +-
 .../tests/err_recursive_dep/expected_stderr        |   14 +-
 sound/oss/dmasound/Kconfig                         |    6 +-
 55 files changed, 3738 insertions(+), 3459 deletions(-)
 create mode 100644 Documentation/kbuild/headers_install.rst
 delete mode 100644 Documentation/kbuild/headers_install.txt
 create mode 100644 Documentation/kbuild/index.rst
 create mode 100644 Documentation/kbuild/issues.rst
 create mode 100644 Documentation/kbuild/kbuild.rst
 delete mode 100644 Documentation/kbuild/kbuild.txt
 create mode 100644 Documentation/kbuild/kconfig-language.rst
 delete mode 100644 Documentation/kbuild/kconfig-language.txt
 create mode 100644 Documentation/kbuild/kconfig-macro-language.rst
 delete mode 100644 Documentation/kbuild/kconfig-macro-language.txt
 create mode 100644 Documentation/kbuild/kconfig.rst
 delete mode 100644 Documentation/kbuild/kconfig.txt
 create mode 100644 Documentation/kbuild/makefiles.rst
 delete mode 100644 Documentation/kbuild/makefiles.txt
 create mode 100644 Documentation/kbuild/modules.rst
 delete mode 100644 Documentation/kbuild/modules.txt

(limited to 'scripts')

diff --git a/Documentation/admin-guide/README.rst b/Documentation/admin-guide/README.rst
index a582c780c3bd..cc6151fc0845 100644
--- a/Documentation/admin-guide/README.rst
+++ b/Documentation/admin-guide/README.rst
@@ -227,7 +227,7 @@ Configuring the kernel
      "make tinyconfig"  Configure the tiniest possible kernel.
 
    You can find more information on using the Linux kernel config tools
-   in Documentation/kbuild/kconfig.txt.
+   in Documentation/kbuild/kconfig.rst.
 
  - NOTES on ``make config``:
 
diff --git a/Documentation/kbuild/headers_install.rst b/Documentation/kbuild/headers_install.rst
new file mode 100644
index 000000000000..1ab7294e41ac
--- /dev/null
+++ b/Documentation/kbuild/headers_install.rst
@@ -0,0 +1,51 @@
+=============================================
+Exporting kernel headers for use by userspace
+=============================================
+
+The "make headers_install" command exports the kernel's header files in a
+form suitable for use by userspace programs.
+
+The linux kernel's exported header files describe the API for user space
+programs attempting to use kernel services.  These kernel header files are
+used by the system's C library (such as glibc or uClibc) to define available
+system calls, as well as constants and structures to be used with these
+system calls.  The C library's header files include the kernel header files
+from the "linux" subdirectory.  The system's libc headers are usually
+installed at the default location /usr/include and the kernel headers in
+subdirectories under that (most notably /usr/include/linux and
+/usr/include/asm).
+
+Kernel headers are backwards compatible, but not forwards compatible.  This
+means that a program built against a C library using older kernel headers
+should run on a newer kernel (although it may not have access to new
+features), but a program built against newer kernel headers may not work on an
+older kernel.
+
+The "make headers_install" command can be run in the top level directory of the
+kernel source code (or using a standard out-of-tree build).  It takes two
+optional arguments::
+
+  make headers_install ARCH=i386 INSTALL_HDR_PATH=/usr
+
+ARCH indicates which architecture to produce headers for, and defaults to the
+current architecture.  The linux/asm directory of the exported kernel headers
+is platform-specific, to see a complete list of supported architectures use
+the command::
+
+  ls -d include/asm-* | sed 's/.*-//'
+
+INSTALL_HDR_PATH indicates where to install the headers. It defaults to
+"./usr".
+
+An 'include' directory is automatically created inside INSTALL_HDR_PATH and
+headers are installed in 'INSTALL_HDR_PATH/include'.
+
+The command "make headers_install_all" exports headers for all architectures
+simultaneously.  (This is mostly of interest to distribution maintainers,
+who create an architecture-independent tarball from the resulting include
+directory.)  You also can use HDR_ARCH_LIST to specify list of architectures.
+Remember to provide the appropriate linux/asm directory via "mv" or "ln -s"
+before building a C library with headers exported this way.
+
+The kernel header export infrastructure is maintained by David Woodhouse
+<dwmw2@infradead.org>.
diff --git a/Documentation/kbuild/headers_install.txt b/Documentation/kbuild/headers_install.txt
deleted file mode 100644
index f0153adb95e2..000000000000
--- a/Documentation/kbuild/headers_install.txt
+++ /dev/null
@@ -1,50 +0,0 @@
-Exporting kernel headers for use by userspace
-=============================================
-
-The "make headers_install" command exports the kernel's header files in a
-form suitable for use by userspace programs.
-
-The linux kernel's exported header files describe the API for user space
-programs attempting to use kernel services.  These kernel header files are
-used by the system's C library (such as glibc or uClibc) to define available
-system calls, as well as constants and structures to be used with these
-system calls.  The C library's header files include the kernel header files
-from the "linux" subdirectory.  The system's libc headers are usually
-installed at the default location /usr/include and the kernel headers in
-subdirectories under that (most notably /usr/include/linux and
-/usr/include/asm).
-
-Kernel headers are backwards compatible, but not forwards compatible.  This
-means that a program built against a C library using older kernel headers
-should run on a newer kernel (although it may not have access to new
-features), but a program built against newer kernel headers may not work on an
-older kernel.
-
-The "make headers_install" command can be run in the top level directory of the
-kernel source code (or using a standard out-of-tree build).  It takes two
-optional arguments:
-
-  make headers_install ARCH=i386 INSTALL_HDR_PATH=/usr
-
-ARCH indicates which architecture to produce headers for, and defaults to the
-current architecture.  The linux/asm directory of the exported kernel headers
-is platform-specific, to see a complete list of supported architectures use
-the command:
-
-  ls -d include/asm-* | sed 's/.*-//'
-
-INSTALL_HDR_PATH indicates where to install the headers. It defaults to
-"./usr".
-
-An 'include' directory is automatically created inside INSTALL_HDR_PATH and
-headers are installed in 'INSTALL_HDR_PATH/include'.
-
-The command "make headers_install_all" exports headers for all architectures
-simultaneously.  (This is mostly of interest to distribution maintainers,
-who create an architecture-independent tarball from the resulting include
-directory.)  You also can use HDR_ARCH_LIST to specify list of architectures.
-Remember to provide the appropriate linux/asm directory via "mv" or "ln -s"
-before building a C library with headers exported this way.
-
-The kernel header export infrastructure is maintained by David Woodhouse
-<dwmw2@infradead.org>.
diff --git a/Documentation/kbuild/index.rst b/Documentation/kbuild/index.rst
new file mode 100644
index 000000000000..42d4cbe4460c
--- /dev/null
+++ b/Documentation/kbuild/index.rst
@@ -0,0 +1,27 @@
+:orphan:
+
+===================
+Kernel Build System
+===================
+
+.. toctree::
+    :maxdepth: 1
+
+    kconfig-language
+    kconfig-macro-language
+
+    kbuild
+    kconfig
+    makefiles
+    modules
+
+    headers_install
+
+    issues
+
+.. only::  subproject and html
+
+   Indices
+   =======
+
+   * :ref:`genindex`
diff --git a/Documentation/kbuild/issues.rst b/Documentation/kbuild/issues.rst
new file mode 100644
index 000000000000..9fdded4b681c
--- /dev/null
+++ b/Documentation/kbuild/issues.rst
@@ -0,0 +1,11 @@
+Recursion issue #1
+------------------
+
+ .. include:: Kconfig.recursion-issue-01
+    :literal:
+
+Recursion issue #2
+------------------
+
+ .. include:: Kconfig.recursion-issue-02
+    :literal:
diff --git a/Documentation/kbuild/kbuild.rst b/Documentation/kbuild/kbuild.rst
new file mode 100644
index 000000000000..e774e760522d
--- /dev/null
+++ b/Documentation/kbuild/kbuild.rst
@@ -0,0 +1,265 @@
+======
+Kbuild
+======
+
+
+Output files
+============
+
+modules.order
+-------------
+This file records the order in which modules appear in Makefiles. This
+is used by modprobe to deterministically resolve aliases that match
+multiple modules.
+
+modules.builtin
+---------------
+This file lists all modules that are built into the kernel. This is used
+by modprobe to not fail when trying to load something builtin.
+
+modules.builtin.modinfo
+--------------------------------------------------
+This file contains modinfo from all modules that are built into the kernel.
+Unlike modinfo of a separate module, all fields are prefixed with module name.
+
+
+Environment variables
+=====================
+
+KCPPFLAGS
+---------
+Additional options to pass when preprocessing. The preprocessing options
+will be used in all cases where kbuild does preprocessing including
+building C files and assembler files.
+
+KAFLAGS
+-------
+Additional options to the assembler (for built-in and modules).
+
+AFLAGS_MODULE
+-------------
+Additional module specific options to use for $(AS).
+
+AFLAGS_KERNEL
+-------------
+Additional options for $(AS) when used for assembler
+code for code that is compiled as built-in.
+
+KCFLAGS
+-------
+Additional options to the C compiler (for built-in and modules).
+
+CFLAGS_KERNEL
+-------------
+Additional options for $(CC) when used to compile
+code that is compiled as built-in.
+
+CFLAGS_MODULE
+-------------
+Additional module specific options to use for $(CC).
+
+LDFLAGS_MODULE
+--------------
+Additional options used for $(LD) when linking modules.
+
+HOSTCFLAGS
+----------
+Additional flags to be passed to $(HOSTCC) when building host programs.
+
+HOSTCXXFLAGS
+------------
+Additional flags to be passed to $(HOSTCXX) when building host programs.
+
+HOSTLDFLAGS
+-----------
+Additional flags to be passed when linking host programs.
+
+HOSTLDLIBS
+----------
+Additional libraries to link against when building host programs.
+
+KBUILD_KCONFIG
+--------------
+Set the top-level Kconfig file to the value of this environment
+variable.  The default name is "Kconfig".
+
+KBUILD_VERBOSE
+--------------
+Set the kbuild verbosity. Can be assigned same values as "V=...".
+
+See make help for the full list.
+
+Setting "V=..." takes precedence over KBUILD_VERBOSE.
+
+KBUILD_EXTMOD
+-------------
+Set the directory to look for the kernel source when building external
+modules.
+
+Setting "M=..." takes precedence over KBUILD_EXTMOD.
+
+KBUILD_OUTPUT
+-------------
+Specify the output directory when building the kernel.
+
+The output directory can also be specified using "O=...".
+
+Setting "O=..." takes precedence over KBUILD_OUTPUT.
+
+KBUILD_DEBARCH
+--------------
+For the deb-pkg target, allows overriding the normal heuristics deployed by
+deb-pkg. Normally deb-pkg attempts to guess the right architecture based on
+the UTS_MACHINE variable, and on some architectures also the kernel config.
+The value of KBUILD_DEBARCH is assumed (not checked) to be a valid Debian
+architecture.
+
+ARCH
+----
+Set ARCH to the architecture to be built.
+
+In most cases the name of the architecture is the same as the
+directory name found in the arch/ directory.
+
+But some architectures such as x86 and sparc have aliases.
+
+- x86: i386 for 32 bit, x86_64 for 64 bit
+- sh: sh for 32 bit, sh64 for 64 bit
+- sparc: sparc32 for 32 bit, sparc64 for 64 bit
+
+CROSS_COMPILE
+-------------
+Specify an optional fixed part of the binutils filename.
+CROSS_COMPILE can be a part of the filename or the full path.
+
+CROSS_COMPILE is also used for ccache in some setups.
+
+CF
+--
+Additional options for sparse.
+
+CF is often used on the command-line like this::
+
+    make CF=-Wbitwise C=2
+
+INSTALL_PATH
+------------
+INSTALL_PATH specifies where to place the updated kernel and system map
+images. Default is /boot, but you can set it to other values.
+
+INSTALLKERNEL
+-------------
+Install script called when using "make install".
+The default name is "installkernel".
+
+The script will be called with the following arguments:
+   - $1 - kernel version
+   - $2 - kernel image file
+   - $3 - kernel map file
+   - $4 - default install path (use root directory if blank)
+
+The implementation of "make install" is architecture specific
+and it may differ from the above.
+
+INSTALLKERNEL is provided to enable the possibility to
+specify a custom installer when cross compiling a kernel.
+
+MODLIB
+------
+Specify where to install modules.
+The default value is::
+
+     $(INSTALL_MOD_PATH)/lib/modules/$(KERNELRELEASE)
+
+The value can be overridden in which case the default value is ignored.
+
+INSTALL_MOD_PATH
+----------------
+INSTALL_MOD_PATH specifies a prefix to MODLIB for module directory
+relocations required by build roots.  This is not defined in the
+makefile but the argument can be passed to make if needed.
+
+INSTALL_MOD_STRIP
+-----------------
+INSTALL_MOD_STRIP, if defined, will cause modules to be
+stripped after they are installed.  If INSTALL_MOD_STRIP is '1', then
+the default option --strip-debug will be used.  Otherwise,
+INSTALL_MOD_STRIP value will be used as the options to the strip command.
+
+INSTALL_HDR_PATH
+----------------
+INSTALL_HDR_PATH specifies where to install user space headers when
+executing "make headers_*".
+
+The default value is::
+
+    $(objtree)/usr
+
+$(objtree) is the directory where output files are saved.
+The output directory is often set using "O=..." on the commandline.
+
+The value can be overridden in which case the default value is ignored.
+
+KBUILD_SIGN_PIN
+---------------
+This variable allows a passphrase or PIN to be passed to the sign-file
+utility when signing kernel modules, if the private key requires such.
+
+KBUILD_MODPOST_WARN
+-------------------
+KBUILD_MODPOST_WARN can be set to avoid errors in case of undefined
+symbols in the final module linking stage. It changes such errors
+into warnings.
+
+KBUILD_MODPOST_NOFINAL
+----------------------
+KBUILD_MODPOST_NOFINAL can be set to skip the final link of modules.
+This is solely useful to speed up test compiles.
+
+KBUILD_EXTRA_SYMBOLS
+--------------------
+For modules that use symbols from other modules.
+See more details in modules.txt.
+
+ALLSOURCE_ARCHS
+---------------
+For tags/TAGS/cscope targets, you can specify more than one arch
+to be included in the databases, separated by blank space. E.g.::
+
+    $ make ALLSOURCE_ARCHS="x86 mips arm" tags
+
+To get all available archs you can also specify all. E.g.::
+
+    $ make ALLSOURCE_ARCHS=all tags
+
+KBUILD_ENABLE_EXTRA_GCC_CHECKS
+------------------------------
+If enabled over the make command line with "W=1", it turns on additional
+gcc -W... options for more extensive build-time checking.
+
+KBUILD_BUILD_TIMESTAMP
+----------------------
+Setting this to a date string overrides the timestamp used in the
+UTS_VERSION definition (uname -v in the running kernel). The value has to
+be a string that can be passed to date -d. The default value
+is the output of the date command at one point during build.
+
+KBUILD_BUILD_USER, KBUILD_BUILD_HOST
+------------------------------------
+These two variables allow to override the user@host string displayed during
+boot and in /proc/version. The default value is the output of the commands
+whoami and host, respectively.
+
+KBUILD_LDS
+----------
+The linker script with full path. Assigned by the top-level Makefile.
+
+KBUILD_VMLINUX_OBJS
+-------------------
+All object files for vmlinux. They are linked to vmlinux in the same
+order as listed in KBUILD_VMLINUX_OBJS.
+
+KBUILD_VMLINUX_LIBS
+-------------------
+All .a "lib" files for vmlinux. KBUILD_VMLINUX_OBJS and KBUILD_VMLINUX_LIBS
+together specify all the object files used to link vmlinux.
diff --git a/Documentation/kbuild/kbuild.txt b/Documentation/kbuild/kbuild.txt
deleted file mode 100644
index 9c230ea71963..000000000000
--- a/Documentation/kbuild/kbuild.txt
+++ /dev/null
@@ -1,248 +0,0 @@
-Output files
-
-modules.order
---------------------------------------------------
-This file records the order in which modules appear in Makefiles. This
-is used by modprobe to deterministically resolve aliases that match
-multiple modules.
-
-modules.builtin
---------------------------------------------------
-This file lists all modules that are built into the kernel. This is used
-by modprobe to not fail when trying to load something builtin.
-
-modules.builtin.modinfo
---------------------------------------------------
-This file contains modinfo from all modules that are built into the kernel.
-Unlike modinfo of a separate module, all fields are prefixed with module name.
-
-
-Environment variables
-
-KCPPFLAGS
---------------------------------------------------
-Additional options to pass when preprocessing. The preprocessing options
-will be used in all cases where kbuild does preprocessing including
-building C files and assembler files.
-
-KAFLAGS
---------------------------------------------------
-Additional options to the assembler (for built-in and modules).
-
-AFLAGS_MODULE
---------------------------------------------------
-Additional module specific options to use for $(AS).
-
-AFLAGS_KERNEL
---------------------------------------------------
-Additional options for $(AS) when used for assembler
-code for code that is compiled as built-in.
-
-KCFLAGS
---------------------------------------------------
-Additional options to the C compiler (for built-in and modules).
-
-CFLAGS_KERNEL
---------------------------------------------------
-Additional options for $(CC) when used to compile
-code that is compiled as built-in.
-
-CFLAGS_MODULE
---------------------------------------------------
-Additional module specific options to use for $(CC).
-
-LDFLAGS_MODULE
---------------------------------------------------
-Additional options used for $(LD) when linking modules.
-
-HOSTCFLAGS
---------------------------------------------------
-Additional flags to be passed to $(HOSTCC) when building host programs.
-
-HOSTCXXFLAGS
---------------------------------------------------
-Additional flags to be passed to $(HOSTCXX) when building host programs.
-
-HOSTLDFLAGS
---------------------------------------------------
-Additional flags to be passed when linking host programs.
-
-HOSTLDLIBS
---------------------------------------------------
-Additional libraries to link against when building host programs.
-
-KBUILD_KCONFIG
---------------------------------------------------
-Set the top-level Kconfig file to the value of this environment
-variable.  The default name is "Kconfig".
-
-KBUILD_VERBOSE
---------------------------------------------------
-Set the kbuild verbosity. Can be assigned same values as "V=...".
-See make help for the full list.
-Setting "V=..." takes precedence over KBUILD_VERBOSE.
-
-KBUILD_EXTMOD
---------------------------------------------------
-Set the directory to look for the kernel source when building external
-modules.
-Setting "M=..." takes precedence over KBUILD_EXTMOD.
-
-KBUILD_OUTPUT
---------------------------------------------------
-Specify the output directory when building the kernel.
-The output directory can also be specified using "O=...".
-Setting "O=..." takes precedence over KBUILD_OUTPUT.
-
-KBUILD_DEBARCH
---------------------------------------------------
-For the deb-pkg target, allows overriding the normal heuristics deployed by
-deb-pkg. Normally deb-pkg attempts to guess the right architecture based on
-the UTS_MACHINE variable, and on some architectures also the kernel config.
-The value of KBUILD_DEBARCH is assumed (not checked) to be a valid Debian
-architecture.
-
-ARCH
---------------------------------------------------
-Set ARCH to the architecture to be built.
-In most cases the name of the architecture is the same as the
-directory name found in the arch/ directory.
-But some architectures such as x86 and sparc have aliases.
-x86: i386 for 32 bit, x86_64 for 64 bit
-sh: sh for 32 bit, sh64 for 64 bit
-sparc: sparc32 for 32 bit, sparc64 for 64 bit
-
-CROSS_COMPILE
---------------------------------------------------
-Specify an optional fixed part of the binutils filename.
-CROSS_COMPILE can be a part of the filename or the full path.
-
-CROSS_COMPILE is also used for ccache in some setups.
-
-CF
---------------------------------------------------
-Additional options for sparse.
-CF is often used on the command-line like this:
-
-    make CF=-Wbitwise C=2
-
-INSTALL_PATH
---------------------------------------------------
-INSTALL_PATH specifies where to place the updated kernel and system map
-images. Default is /boot, but you can set it to other values.
-
-INSTALLKERNEL
---------------------------------------------------
-Install script called when using "make install".
-The default name is "installkernel".
-
-The script will be called with the following arguments:
-    $1 - kernel version
-    $2 - kernel image file
-    $3 - kernel map file
-    $4 - default install path (use root directory if blank)
-
-The implementation of "make install" is architecture specific
-and it may differ from the above.
-
-INSTALLKERNEL is provided to enable the possibility to
-specify a custom installer when cross compiling a kernel.
-
-MODLIB
---------------------------------------------------
-Specify where to install modules.
-The default value is:
-
-     $(INSTALL_MOD_PATH)/lib/modules/$(KERNELRELEASE)
-
-The value can be overridden in which case the default value is ignored.
-
-INSTALL_MOD_PATH
---------------------------------------------------
-INSTALL_MOD_PATH specifies a prefix to MODLIB for module directory
-relocations required by build roots.  This is not defined in the
-makefile but the argument can be passed to make if needed.
-
-INSTALL_MOD_STRIP
---------------------------------------------------
-INSTALL_MOD_STRIP, if defined, will cause modules to be
-stripped after they are installed.  If INSTALL_MOD_STRIP is '1', then
-the default option --strip-debug will be used.  Otherwise,
-INSTALL_MOD_STRIP value will be used as the options to the strip command.
-
-INSTALL_HDR_PATH
---------------------------------------------------
-INSTALL_HDR_PATH specifies where to install user space headers when
-executing "make headers_*".
-The default value is:
-
-    $(objtree)/usr
-
-$(objtree) is the directory where output files are saved.
-The output directory is often set using "O=..." on the commandline.
-
-The value can be overridden in which case the default value is ignored.
-
-KBUILD_SIGN_PIN
---------------------------------------------------
-This variable allows a passphrase or PIN to be passed to the sign-file
-utility when signing kernel modules, if the private key requires such.
-
-KBUILD_MODPOST_WARN
---------------------------------------------------
-KBUILD_MODPOST_WARN can be set to avoid errors in case of undefined
-symbols in the final module linking stage. It changes such errors
-into warnings.
-
-KBUILD_MODPOST_NOFINAL
---------------------------------------------------
-KBUILD_MODPOST_NOFINAL can be set to skip the final link of modules.
-This is solely useful to speed up test compiles.
-
-KBUILD_EXTRA_SYMBOLS
---------------------------------------------------
-For modules that use symbols from other modules.
-See more details in modules.txt.
-
-ALLSOURCE_ARCHS
---------------------------------------------------
-For tags/TAGS/cscope targets, you can specify more than one arch
-to be included in the databases, separated by blank space. E.g.:
-
-    $ make ALLSOURCE_ARCHS="x86 mips arm" tags
-
-To get all available archs you can also specify all. E.g.:
-
-    $ make ALLSOURCE_ARCHS=all tags
-
-KBUILD_ENABLE_EXTRA_GCC_CHECKS
---------------------------------------------------
-If enabled over the make command line with "W=1", it turns on additional
-gcc -W... options for more extensive build-time checking.
-
-KBUILD_BUILD_TIMESTAMP
---------------------------------------------------
-Setting this to a date string overrides the timestamp used in the
-UTS_VERSION definition (uname -v in the running kernel). The value has to
-be a string that can be passed to date -d. The default value
-is the output of the date command at one point during build.
-
-KBUILD_BUILD_USER, KBUILD_BUILD_HOST
---------------------------------------------------
-These two variables allow to override the user@host string displayed during
-boot and in /proc/version. The default value is the output of the commands
-whoami and host, respectively.
-
-KBUILD_LDS
---------------------------------------------------
-The linker script with full path. Assigned by the top-level Makefile.
-
-KBUILD_VMLINUX_OBJS
---------------------------------------------------
-All object files for vmlinux. They are linked to vmlinux in the same
-order as listed in KBUILD_VMLINUX_OBJS.
-
-KBUILD_VMLINUX_LIBS
---------------------------------------------------
-All .a "lib" files for vmlinux. KBUILD_VMLINUX_OBJS and KBUILD_VMLINUX_LIBS
-together specify all the object files used to link vmlinux.
diff --git a/Documentation/kbuild/kconfig-language.rst b/Documentation/kbuild/kconfig-language.rst
new file mode 100644
index 000000000000..2bc8a7803365
--- /dev/null
+++ b/Documentation/kbuild/kconfig-language.rst
@@ -0,0 +1,689 @@
+================
+Kconfig Language
+================
+
+Introduction
+------------
+
+The configuration database is a collection of configuration options
+organized in a tree structure::
+
+	+- Code maturity level options
+	|  +- Prompt for development and/or incomplete code/drivers
+	+- General setup
+	|  +- Networking support
+	|  +- System V IPC
+	|  +- BSD Process Accounting
+	|  +- Sysctl support
+	+- Loadable module support
+	|  +- Enable loadable module support
+	|     +- Set version information on all module symbols
+	|     +- Kernel module loader
+	+- ...
+
+Every entry has its own dependencies. These dependencies are used
+to determine the visibility of an entry. Any child entry is only
+visible if its parent entry is also visible.
+
+Menu entries
+------------
+
+Most entries define a config option; all other entries help to organize
+them. A single configuration option is defined like this::
+
+  config MODVERSIONS
+	bool "Set version information on all module symbols"
+	depends on MODULES
+	help
+	  Usually, modules have to be recompiled whenever you switch to a new
+	  kernel.  ...
+
+Every line starts with a key word and can be followed by multiple
+arguments.  "config" starts a new config entry. The following lines
+define attributes for this config option. Attributes can be the type of
+the config option, input prompt, dependencies, help text and default
+values. A config option can be defined multiple times with the same
+name, but every definition can have only a single input prompt and the
+type must not conflict.
+
+Menu attributes
+---------------
+
+A menu entry can have a number of attributes. Not all of them are
+applicable everywhere (see syntax).
+
+- type definition: "bool"/"tristate"/"string"/"hex"/"int"
+  Every config option must have a type. There are only two basic types:
+  tristate and string; the other types are based on these two. The type
+  definition optionally accepts an input prompt, so these two examples
+  are equivalent::
+
+	bool "Networking support"
+
+  and::
+
+	bool
+	prompt "Networking support"
+
+- input prompt: "prompt" <prompt> ["if" <expr>]
+  Every menu entry can have at most one prompt, which is used to display
+  to the user. Optionally dependencies only for this prompt can be added
+  with "if".
+
+- default value: "default" <expr> ["if" <expr>]
+  A config option can have any number of default values. If multiple
+  default values are visible, only the first defined one is active.
+  Default values are not limited to the menu entry where they are
+  defined. This means the default can be defined somewhere else or be
+  overridden by an earlier definition.
+  The default value is only assigned to the config symbol if no other
+  value was set by the user (via the input prompt above). If an input
+  prompt is visible the default value is presented to the user and can
+  be overridden by him.
+  Optionally, dependencies only for this default value can be added with
+  "if".
+
+ The default value deliberately defaults to 'n' in order to avoid bloating the
+ build. With few exceptions, new config options should not change this. The
+ intent is for "make oldconfig" to add as little as possible to the config from
+ release to release.
+
+ Note:
+	Things that merit "default y/m" include:
+
+	a) A new Kconfig option for something that used to always be built
+	   should be "default y".
+
+	b) A new gatekeeping Kconfig option that hides/shows other Kconfig
+	   options (but does not generate any code of its own), should be
+	   "default y" so people will see those other options.
+
+	c) Sub-driver behavior or similar options for a driver that is
+	   "default n". This allows you to provide sane defaults.
+
+	d) Hardware or infrastructure that everybody expects, such as CONFIG_NET
+	   or CONFIG_BLOCK. These are rare exceptions.
+
+- type definition + default value::
+
+	"def_bool"/"def_tristate" <expr> ["if" <expr>]
+
+  This is a shorthand notation for a type definition plus a value.
+  Optionally dependencies for this default value can be added with "if".
+
+- dependencies: "depends on" <expr>
+  This defines a dependency for this menu entry. If multiple
+  dependencies are defined, they are connected with '&&'. Dependencies
+  are applied to all other options within this menu entry (which also
+  accept an "if" expression), so these two examples are equivalent::
+
+	bool "foo" if BAR
+	default y if BAR
+
+  and::
+
+	depends on BAR
+	bool "foo"
+	default y
+
+- reverse dependencies: "select" <symbol> ["if" <expr>]
+  While normal dependencies reduce the upper limit of a symbol (see
+  below), reverse dependencies can be used to force a lower limit of
+  another symbol. The value of the current menu symbol is used as the
+  minimal value <symbol> can be set to. If <symbol> is selected multiple
+  times, the limit is set to the largest selection.
+  Reverse dependencies can only be used with boolean or tristate
+  symbols.
+
+  Note:
+	select should be used with care. select will force
+	a symbol to a value without visiting the dependencies.
+	By abusing select you are able to select a symbol FOO even
+	if FOO depends on BAR that is not set.
+	In general use select only for non-visible symbols
+	(no prompts anywhere) and for symbols with no dependencies.
+	That will limit the usefulness but on the other hand avoid
+	the illegal configurations all over.
+
+- weak reverse dependencies: "imply" <symbol> ["if" <expr>]
+  This is similar to "select" as it enforces a lower limit on another
+  symbol except that the "implied" symbol's value may still be set to n
+  from a direct dependency or with a visible prompt.
+
+  Given the following example::
+
+    config FOO
+	tristate
+	imply BAZ
+
+    config BAZ
+	tristate
+	depends on BAR
+
+  The following values are possible:
+
+	===		===		=============	==============
+	FOO		BAR		BAZ's default	choice for BAZ
+	===		===		=============	==============
+	n		y		n		N/m/y
+	m		y		m		M/y/n
+	y		y		y		Y/n
+	y		n		*		N
+	===		===		=============	==============
+
+  This is useful e.g. with multiple drivers that want to indicate their
+  ability to hook into a secondary subsystem while allowing the user to
+  configure that subsystem out without also having to unset these drivers.
+
+- limiting menu display: "visible if" <expr>
+  This attribute is only applicable to menu blocks, if the condition is
+  false, the menu block is not displayed to the user (the symbols
+  contained there can still be selected by other symbols, though). It is
+  similar to a conditional "prompt" attribute for individual menu
+  entries. Default value of "visible" is true.
+
+- numerical ranges: "range" <symbol> <symbol> ["if" <expr>]
+  This allows to limit the range of possible input values for int
+  and hex symbols. The user can only input a value which is larger than
+  or equal to the first symbol and smaller than or equal to the second
+  symbol.
+
+- help text: "help" or "---help---"
+  This defines a help text. The end of the help text is determined by
+  the indentation level, this means it ends at the first line which has
+  a smaller indentation than the first line of the help text.
+  "---help---" and "help" do not differ in behaviour, "---help---" is
+  used to help visually separate configuration logic from help within
+  the file as an aid to developers.
+
+- misc options: "option" <symbol>[=<value>]
+  Various less common options can be defined via this option syntax,
+  which can modify the behaviour of the menu entry and its config
+  symbol. These options are currently possible:
+
+  - "defconfig_list"
+    This declares a list of default entries which can be used when
+    looking for the default configuration (which is used when the main
+    .config doesn't exists yet.)
+
+  - "modules"
+    This declares the symbol to be used as the MODULES symbol, which
+    enables the third modular state for all config symbols.
+    At most one symbol may have the "modules" option set.
+
+  - "allnoconfig_y"
+    This declares the symbol as one that should have the value y when
+    using "allnoconfig". Used for symbols that hide other symbols.
+
+Menu dependencies
+-----------------
+
+Dependencies define the visibility of a menu entry and can also reduce
+the input range of tristate symbols. The tristate logic used in the
+expressions uses one more state than normal boolean logic to express the
+module state. Dependency expressions have the following syntax::
+
+  <expr> ::= <symbol>                           (1)
+           <symbol> '=' <symbol>                (2)
+           <symbol> '!=' <symbol>               (3)
+           <symbol1> '<' <symbol2>              (4)
+           <symbol1> '>' <symbol2>              (4)
+           <symbol1> '<=' <symbol2>             (4)
+           <symbol1> '>=' <symbol2>             (4)
+           '(' <expr> ')'                       (5)
+           '!' <expr>                           (6)
+           <expr> '&&' <expr>                   (7)
+           <expr> '||' <expr>                   (8)
+
+Expressions are listed in decreasing order of precedence.
+
+(1) Convert the symbol into an expression. Boolean and tristate symbols
+    are simply converted into the respective expression values. All
+    other symbol types result in 'n'.
+(2) If the values of both symbols are equal, it returns 'y',
+    otherwise 'n'.
+(3) If the values of both symbols are equal, it returns 'n',
+    otherwise 'y'.
+(4) If value of <symbol1> is respectively lower, greater, lower-or-equal,
+    or greater-or-equal than value of <symbol2>, it returns 'y',
+    otherwise 'n'.
+(5) Returns the value of the expression. Used to override precedence.
+(6) Returns the result of (2-/expr/).
+(7) Returns the result of min(/expr/, /expr/).
+(8) Returns the result of max(/expr/, /expr/).
+
+An expression can have a value of 'n', 'm' or 'y' (or 0, 1, 2
+respectively for calculations). A menu entry becomes visible when its
+expression evaluates to 'm' or 'y'.
+
+There are two types of symbols: constant and non-constant symbols.
+Non-constant symbols are the most common ones and are defined with the
+'config' statement. Non-constant symbols consist entirely of alphanumeric
+characters or underscores.
+Constant symbols are only part of expressions. Constant symbols are
+always surrounded by single or double quotes. Within the quote, any
+other character is allowed and the quotes can be escaped using '\'.
+
+Menu structure
+--------------
+
+The position of a menu entry in the tree is determined in two ways. First
+it can be specified explicitly::
+
+  menu "Network device support"
+	depends on NET
+
+  config NETDEVICES
+	...
+
+  endmenu
+
+All entries within the "menu" ... "endmenu" block become a submenu of
+"Network device support". All subentries inherit the dependencies from
+the menu entry, e.g. this means the dependency "NET" is added to the
+dependency list of the config option NETDEVICES.
+
+The other way to generate the menu structure is done by analyzing the
+dependencies. If a menu entry somehow depends on the previous entry, it
+can be made a submenu of it. First, the previous (parent) symbol must
+be part of the dependency list and then one of these two conditions
+must be true:
+
+- the child entry must become invisible, if the parent is set to 'n'
+- the child entry must only be visible, if the parent is visible::
+
+    config MODULES
+	bool "Enable loadable module support"
+
+    config MODVERSIONS
+	bool "Set version information on all module symbols"
+	depends on MODULES
+
+    comment "module support disabled"
+	depends on !MODULES
+
+MODVERSIONS directly depends on MODULES, this means it's only visible if
+MODULES is different from 'n'. The comment on the other hand is only
+visible when MODULES is set to 'n'.
+
+
+Kconfig syntax
+--------------
+
+The configuration file describes a series of menu entries, where every
+line starts with a keyword (except help texts). The following keywords
+end a menu entry:
+
+- config
+- menuconfig
+- choice/endchoice
+- comment
+- menu/endmenu
+- if/endif
+- source
+
+The first five also start the definition of a menu entry.
+
+config::
+	"config" <symbol>
+	<config options>
+
+This defines a config symbol <symbol> and accepts any of above
+attributes as options.
+
+menuconfig::
+	"menuconfig" <symbol>
+	<config options>
+
+This is similar to the simple config entry above, but it also gives a
+hint to front ends, that all suboptions should be displayed as a
+separate list of options. To make sure all the suboptions will really
+show up under the menuconfig entry and not outside of it, every item
+from the <config options> list must depend on the menuconfig symbol.
+In practice, this is achieved by using one of the next two constructs::
+
+  (1):
+  menuconfig M
+  if M
+      config C1
+      config C2
+  endif
+
+  (2):
+  menuconfig M
+  config C1
+      depends on M
+  config C2
+      depends on M
+
+In the following examples (3) and (4), C1 and C2 still have the M
+dependency, but will not appear under menuconfig M anymore, because
+of C0, which doesn't depend on M::
+
+  (3):
+  menuconfig M
+      config C0
+  if M
+      config C1
+      config C2
+  endif
+
+  (4):
+  menuconfig M
+  config C0
+  config C1
+      depends on M
+  config C2
+      depends on M
+
+choices::
+
+	"choice" [symbol]
+	<choice options>
+	<choice block>
+	"endchoice"
+
+This defines a choice group and accepts any of the above attributes as
+options. A choice can only be of type bool or tristate.  If no type is
+specified for a choice, its type will be determined by the type of
+the first choice element in the group or remain unknown if none of the
+choice elements have a type specified, as well.
+
+While a boolean choice only allows a single config entry to be
+selected, a tristate choice also allows any number of config entries
+to be set to 'm'. This can be used if multiple drivers for a single
+hardware exists and only a single driver can be compiled/loaded into
+the kernel, but all drivers can be compiled as modules.
+
+A choice accepts another option "optional", which allows to set the
+choice to 'n' and no entry needs to be selected.
+If no [symbol] is associated with a choice, then you can not have multiple
+definitions of that choice. If a [symbol] is associated to the choice,
+then you may define the same choice (i.e. with the same entries) in another
+place.
+
+comment::
+
+	"comment" <prompt>
+	<comment options>
+
+This defines a comment which is displayed to the user during the
+configuration process and is also echoed to the output files. The only
+possible options are dependencies.
+
+menu::
+
+	"menu" <prompt>
+	<menu options>
+	<menu block>
+	"endmenu"
+
+This defines a menu block, see "Menu structure" above for more
+information. The only possible options are dependencies and "visible"
+attributes.
+
+if::
+
+	"if" <expr>
+	<if block>
+	"endif"
+
+This defines an if block. The dependency expression <expr> is appended
+to all enclosed menu entries.
+
+source::
+
+	"source" <prompt>
+
+This reads the specified configuration file. This file is always parsed.
+
+mainmenu::
+
+	"mainmenu" <prompt>
+
+This sets the config program's title bar if the config program chooses
+to use it. It should be placed at the top of the configuration, before any
+other statement.
+
+'#' Kconfig source file comment:
+
+An unquoted '#' character anywhere in a source file line indicates
+the beginning of a source file comment.  The remainder of that line
+is a comment.
+
+
+Kconfig hints
+-------------
+This is a collection of Kconfig tips, most of which aren't obvious at
+first glance and most of which have become idioms in several Kconfig
+files.
+
+Adding common features and make the usage configurable
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+It is a common idiom to implement a feature/functionality that are
+relevant for some architectures but not all.
+The recommended way to do so is to use a config variable named HAVE_*
+that is defined in a common Kconfig file and selected by the relevant
+architectures.
+An example is the generic IOMAP functionality.
+
+We would in lib/Kconfig see::
+
+  # Generic IOMAP is used to ...
+  config HAVE_GENERIC_IOMAP
+
+  config GENERIC_IOMAP
+	depends on HAVE_GENERIC_IOMAP && FOO
+
+And in lib/Makefile we would see::
+
+	obj-$(CONFIG_GENERIC_IOMAP) += iomap.o
+
+For each architecture using the generic IOMAP functionality we would see::
+
+  config X86
+	select ...
+	select HAVE_GENERIC_IOMAP
+	select ...
+
+Note: we use the existing config option and avoid creating a new
+config variable to select HAVE_GENERIC_IOMAP.
+
+Note: the use of the internal config variable HAVE_GENERIC_IOMAP, it is
+introduced to overcome the limitation of select which will force a
+config option to 'y' no matter the dependencies.
+The dependencies are moved to the symbol GENERIC_IOMAP and we avoid the
+situation where select forces a symbol equals to 'y'.
+
+Adding features that need compiler support
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+There are several features that need compiler support. The recommended way
+to describe the dependency on the compiler feature is to use "depends on"
+followed by a test macro::
+
+  config STACKPROTECTOR
+	bool "Stack Protector buffer overflow detection"
+	depends on $(cc-option,-fstack-protector)
+	...
+
+If you need to expose a compiler capability to makefiles and/or C source files,
+`CC_HAS_` is the recommended prefix for the config option::
+
+  config CC_HAS_STACKPROTECTOR_NONE
+	def_bool $(cc-option,-fno-stack-protector)
+
+Build as module only
+~~~~~~~~~~~~~~~~~~~~
+To restrict a component build to module-only, qualify its config symbol
+with "depends on m".  E.g.::
+
+  config FOO
+	depends on BAR && m
+
+limits FOO to module (=m) or disabled (=n).
+
+Kconfig recursive dependency limitations
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+If you've hit the Kconfig error: "recursive dependency detected" you've run
+into a recursive dependency issue with Kconfig, a recursive dependency can be
+summarized as a circular dependency. The kconfig tools need to ensure that
+Kconfig files comply with specified configuration requirements. In order to do
+that kconfig must determine the values that are possible for all Kconfig
+symbols, this is currently not possible if there is a circular relation
+between two or more Kconfig symbols. For more details refer to the "Simple
+Kconfig recursive issue" subsection below. Kconfig does not do recursive
+dependency resolution; this has a few implications for Kconfig file writers.
+We'll first explain why this issues exists and then provide an example
+technical limitation which this brings upon Kconfig developers. Eager
+developers wishing to try to address this limitation should read the next
+subsections.
+
+Simple Kconfig recursive issue
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Read: Documentation/kbuild/Kconfig.recursion-issue-01
+
+Test with::
+
+  make KBUILD_KCONFIG=Documentation/kbuild/Kconfig.recursion-issue-01 allnoconfig
+
+Cumulative Kconfig recursive issue
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Read: Documentation/kbuild/Kconfig.recursion-issue-02
+
+Test with::
+
+  make KBUILD_KCONFIG=Documentation/kbuild/Kconfig.recursion-issue-02 allnoconfig
+
+Practical solutions to kconfig recursive issue
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Developers who run into the recursive Kconfig issue have two options
+at their disposal. We document them below and also provide a list of
+historical issues resolved through these different solutions.
+
+  a) Remove any superfluous "select FOO" or "depends on FOO"
+  b) Match dependency semantics:
+
+	b1) Swap all "select FOO" to "depends on FOO" or,
+
+	b2) Swap all "depends on FOO" to "select FOO"
+
+The resolution to a) can be tested with the sample Kconfig file
+Documentation/kbuild/Kconfig.recursion-issue-01 through the removal
+of the "select CORE" from CORE_BELL_A_ADVANCED as that is implicit already
+since CORE_BELL_A depends on CORE. At times it may not be possible to remove
+some dependency criteria, for such cases you can work with solution b).
+
+The two different resolutions for b) can be tested in the sample Kconfig file
+Documentation/kbuild/Kconfig.recursion-issue-02.
+
+Below is a list of examples of prior fixes for these types of recursive issues;
+all errors appear to involve one or more select's and one or more "depends on".
+
+============    ===================================
+commit          fix
+============    ===================================
+06b718c01208    select A -> depends on A
+c22eacfe82f9    depends on A -> depends on B
+6a91e854442c    select A -> depends on A
+118c565a8f2e    select A -> select B
+f004e5594705    select A -> depends on A
+c7861f37b4c6    depends on A -> (null)
+80c69915e5fb    select A -> (null)              (1)
+c2218e26c0d0    select A -> depends on A        (1)
+d6ae99d04e1c    select A -> depends on A
+95ca19cf8cbf    select A -> depends on A
+8f057d7bca54    depends on A -> (null)
+8f057d7bca54    depends on A -> select A
+a0701f04846e    select A -> depends on A
+0c8b92f7f259    depends on A -> (null)
+e4e9e0540928    select A -> depends on A        (2)
+7453ea886e87    depends on A > (null)           (1)
+7b1fff7e4fdf    select A -> depends on A
+86c747d2a4f0    select A -> depends on A
+d9f9ab51e55e    select A -> depends on A
+0c51a4d8abd6    depends on A -> select A        (3)
+e98062ed6dc4    select A -> depends on A        (3)
+91e5d284a7f1    select A -> (null)
+============    ===================================
+
+(1) Partial (or no) quote of error.
+(2) That seems to be the gist of that fix.
+(3) Same error.
+
+Future kconfig work
+~~~~~~~~~~~~~~~~~~~
+
+Work on kconfig is welcomed on both areas of clarifying semantics and on
+evaluating the use of a full SAT solver for it. A full SAT solver can be
+desirable to enable more complex dependency mappings and / or queries,
+for instance on possible use case for a SAT solver could be that of handling
+the current known recursive dependency issues. It is not known if this would
+address such issues but such evaluation is desirable. If support for a full SAT
+solver proves too complex or that it cannot address recursive dependency issues
+Kconfig should have at least clear and well defined semantics which also
+addresses and documents limitations or requirements such as the ones dealing
+with recursive dependencies.
+
+Further work on both of these areas is welcomed on Kconfig. We elaborate
+on both of these in the next two subsections.
+
+Semantics of Kconfig
+~~~~~~~~~~~~~~~~~~~~
+
+The use of Kconfig is broad, Linux is now only one of Kconfig's users:
+one study has completed a broad analysis of Kconfig use in 12 projects [0]_.
+Despite its widespread use, and although this document does a reasonable job
+in documenting basic Kconfig syntax a more precise definition of Kconfig
+semantics is welcomed. One project deduced Kconfig semantics through
+the use of the xconfig configurator [1]_. Work should be done to confirm if
+the deduced semantics matches our intended Kconfig design goals.
+
+Having well defined semantics can be useful for tools for practical
+evaluation of depenencies, for instance one such use known case was work to
+express in boolean abstraction of the inferred semantics of Kconfig to
+translate Kconfig logic into boolean formulas and run a SAT solver on this to
+find dead code / features (always inactive), 114 dead features were found in
+Linux using this methodology [1]_ (Section 8: Threats to validity).
+
+Confirming this could prove useful as Kconfig stands as one of the the leading
+industrial variability modeling languages [1]_ [2]_. Its study would help
+evaluate practical uses of such languages, their use was only theoretical
+and real world requirements were not well understood. As it stands though
+only reverse engineering techniques have been used to deduce semantics from
+variability modeling languages such as Kconfig [3]_.
+
+.. [0] http://www.eng.uwaterloo.ca/~shshe/kconfig_semantics.pdf
+.. [1] http://gsd.uwaterloo.ca/sites/default/files/vm-2013-berger.pdf
+.. [2] http://gsd.uwaterloo.ca/sites/default/files/ase241-berger_0.pdf
+.. [3] http://gsd.uwaterloo.ca/sites/default/files/icse2011.pdf
+
+Full SAT solver for Kconfig
+~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Although SAT solvers [4]_ haven't yet been used by Kconfig directly, as noted
+in the previous subsection, work has been done however to express in boolean
+abstraction the inferred semantics of Kconfig to translate Kconfig logic into
+boolean formulas and run a SAT solver on it [5]_. Another known related project
+is CADOS [6]_ (former VAMOS [7]_) and the tools, mainly undertaker [8]_, which
+has been introduced first with [9]_.  The basic concept of undertaker is to
+exract variability models from Kconfig, and put them together with a
+propositional formula extracted from CPP #ifdefs and build-rules into a SAT
+solver in order to find dead code, dead files, and dead symbols. If using a SAT
+solver is desirable on Kconfig one approach would be to evaluate repurposing
+such efforts somehow on Kconfig. There is enough interest from mentors of
+existing projects to not only help advise how to integrate this work upstream
+but also help maintain it long term. Interested developers should visit:
+
+http://kernelnewbies.org/KernelProjects/kconfig-sat
+
+.. [4] http://www.cs.cornell.edu/~sabhar/chapters/SATSolvers-KR-Handbook.pdf
+.. [5] http://gsd.uwaterloo.ca/sites/default/files/vm-2013-berger.pdf
+.. [6] https://cados.cs.fau.de
+.. [7] https://vamos.cs.fau.de
+.. [8] https://undertaker.cs.fau.de
+.. [9] https://www4.cs.fau.de/Publications/2011/tartler_11_eurosys.pdf
diff --git a/Documentation/kbuild/kconfig-language.txt b/Documentation/kbuild/kconfig-language.txt
deleted file mode 100644
index 864e740811da..000000000000
--- a/Documentation/kbuild/kconfig-language.txt
+++ /dev/null
@@ -1,669 +0,0 @@
-Introduction
-------------
-
-The configuration database is a collection of configuration options
-organized in a tree structure:
-
-	+- Code maturity level options
-	|  +- Prompt for development and/or incomplete code/drivers
-	+- General setup
-	|  +- Networking support
-	|  +- System V IPC
-	|  +- BSD Process Accounting
-	|  +- Sysctl support
-	+- Loadable module support
-	|  +- Enable loadable module support
-	|     +- Set version information on all module symbols
-	|     +- Kernel module loader
-	+- ...
-
-Every entry has its own dependencies. These dependencies are used
-to determine the visibility of an entry. Any child entry is only
-visible if its parent entry is also visible.
-
-Menu entries
-------------
-
-Most entries define a config option; all other entries help to organize
-them. A single configuration option is defined like this:
-
-config MODVERSIONS
-	bool "Set version information on all module symbols"
-	depends on MODULES
-	help
-	  Usually, modules have to be recompiled whenever you switch to a new
-	  kernel.  ...
-
-Every line starts with a key word and can be followed by multiple
-arguments.  "config" starts a new config entry. The following lines
-define attributes for this config option. Attributes can be the type of
-the config option, input prompt, dependencies, help text and default
-values. A config option can be defined multiple times with the same
-name, but every definition can have only a single input prompt and the
-type must not conflict.
-
-Menu attributes
----------------
-
-A menu entry can have a number of attributes. Not all of them are
-applicable everywhere (see syntax).
-
-- type definition: "bool"/"tristate"/"string"/"hex"/"int"
-  Every config option must have a type. There are only two basic types:
-  tristate and string; the other types are based on these two. The type
-  definition optionally accepts an input prompt, so these two examples
-  are equivalent:
-
-	bool "Networking support"
-  and
-	bool
-	prompt "Networking support"
-
-- input prompt: "prompt" <prompt> ["if" <expr>]
-  Every menu entry can have at most one prompt, which is used to display
-  to the user. Optionally dependencies only for this prompt can be added
-  with "if".
-
-- default value: "default" <expr> ["if" <expr>]
-  A config option can have any number of default values. If multiple
-  default values are visible, only the first defined one is active.
-  Default values are not limited to the menu entry where they are
-  defined. This means the default can be defined somewhere else or be
-  overridden by an earlier definition.
-  The default value is only assigned to the config symbol if no other
-  value was set by the user (via the input prompt above). If an input
-  prompt is visible the default value is presented to the user and can
-  be overridden by him.
-  Optionally, dependencies only for this default value can be added with
-  "if".
-
- The default value deliberately defaults to 'n' in order to avoid bloating the
- build. With few exceptions, new config options should not change this. The
- intent is for "make oldconfig" to add as little as possible to the config from
- release to release.
-
- Note:
-	Things that merit "default y/m" include:
-
-	a) A new Kconfig option for something that used to always be built
-	   should be "default y".
-
-	b) A new gatekeeping Kconfig option that hides/shows other Kconfig
-	   options (but does not generate any code of its own), should be
-	   "default y" so people will see those other options.
-
-	c) Sub-driver behavior or similar options for a driver that is
-	   "default n". This allows you to provide sane defaults.
-
-	d) Hardware or infrastructure that everybody expects, such as CONFIG_NET
-	   or CONFIG_BLOCK. These are rare exceptions.
-
-- type definition + default value:
-	"def_bool"/"def_tristate" <expr> ["if" <expr>]
-  This is a shorthand notation for a type definition plus a value.
-  Optionally dependencies for this default value can be added with "if".
-
-- dependencies: "depends on" <expr>
-  This defines a dependency for this menu entry. If multiple
-  dependencies are defined, they are connected with '&&'. Dependencies
-  are applied to all other options within this menu entry (which also
-  accept an "if" expression), so these two examples are equivalent:
-
-	bool "foo" if BAR
-	default y if BAR
-  and
-	depends on BAR
-	bool "foo"
-	default y
-
-- reverse dependencies: "select" <symbol> ["if" <expr>]
-  While normal dependencies reduce the upper limit of a symbol (see
-  below), reverse dependencies can be used to force a lower limit of
-  another symbol. The value of the current menu symbol is used as the
-  minimal value <symbol> can be set to. If <symbol> is selected multiple
-  times, the limit is set to the largest selection.
-  Reverse dependencies can only be used with boolean or tristate
-  symbols.
-  Note:
-	select should be used with care. select will force
-	a symbol to a value without visiting the dependencies.
-	By abusing select you are able to select a symbol FOO even
-	if FOO depends on BAR that is not set.
-	In general use select only for non-visible symbols
-	(no prompts anywhere) and for symbols with no dependencies.
-	That will limit the usefulness but on the other hand avoid
-	the illegal configurations all over.
-
-- weak reverse dependencies: "imply" <symbol> ["if" <expr>]
-  This is similar to "select" as it enforces a lower limit on another
-  symbol except that the "implied" symbol's value may still be set to n
-  from a direct dependency or with a visible prompt.
-
-  Given the following example:
-
-  config FOO
-	tristate
-	imply BAZ
-
-  config BAZ
-	tristate
-	depends on BAR
-
-  The following values are possible:
-
-	FOO		BAR		BAZ's default	choice for BAZ
-	---		---		-------------	--------------
-	n		y		n		N/m/y
-	m		y		m		M/y/n
-	y		y		y		Y/n
-	y		n		*		N
-
-  This is useful e.g. with multiple drivers that want to indicate their
-  ability to hook into a secondary subsystem while allowing the user to
-  configure that subsystem out without also having to unset these drivers.
-
-- limiting menu display: "visible if" <expr>
-  This attribute is only applicable to menu blocks, if the condition is
-  false, the menu block is not displayed to the user (the symbols
-  contained there can still be selected by other symbols, though). It is
-  similar to a conditional "prompt" attribute for individual menu
-  entries. Default value of "visible" is true.
-
-- numerical ranges: "range" <symbol> <symbol> ["if" <expr>]
-  This allows to limit the range of possible input values for int
-  and hex symbols. The user can only input a value which is larger than
-  or equal to the first symbol and smaller than or equal to the second
-  symbol.
-
-- help text: "help" or "---help---"
-  This defines a help text. The end of the help text is determined by
-  the indentation level, this means it ends at the first line which has
-  a smaller indentation than the first line of the help text.
-  "---help---" and "help" do not differ in behaviour, "---help---" is
-  used to help visually separate configuration logic from help within
-  the file as an aid to developers.
-
-- misc options: "option" <symbol>[=<value>]
-  Various less common options can be defined via this option syntax,
-  which can modify the behaviour of the menu entry and its config
-  symbol. These options are currently possible:
-
-  - "defconfig_list"
-    This declares a list of default entries which can be used when
-    looking for the default configuration (which is used when the main
-    .config doesn't exists yet.)
-
-  - "modules"
-    This declares the symbol to be used as the MODULES symbol, which
-    enables the third modular state for all config symbols.
-    At most one symbol may have the "modules" option set.
-
-  - "allnoconfig_y"
-    This declares the symbol as one that should have the value y when
-    using "allnoconfig". Used for symbols that hide other symbols.
-
-Menu dependencies
------------------
-
-Dependencies define the visibility of a menu entry and can also reduce
-the input range of tristate symbols. The tristate logic used in the
-expressions uses one more state than normal boolean logic to express the
-module state. Dependency expressions have the following syntax:
-
-<expr> ::= <symbol>                             (1)
-           <symbol> '=' <symbol>                (2)
-           <symbol> '!=' <symbol>               (3)
-           <symbol1> '<' <symbol2>              (4)
-           <symbol1> '>' <symbol2>              (4)
-           <symbol1> '<=' <symbol2>             (4)
-           <symbol1> '>=' <symbol2>             (4)
-           '(' <expr> ')'                       (5)
-           '!' <expr>                           (6)
-           <expr> '&&' <expr>                   (7)
-           <expr> '||' <expr>                   (8)
-
-Expressions are listed in decreasing order of precedence. 
-
-(1) Convert the symbol into an expression. Boolean and tristate symbols
-    are simply converted into the respective expression values. All
-    other symbol types result in 'n'.
-(2) If the values of both symbols are equal, it returns 'y',
-    otherwise 'n'.
-(3) If the values of both symbols are equal, it returns 'n',
-    otherwise 'y'.
-(4) If value of <symbol1> is respectively lower, greater, lower-or-equal,
-    or greater-or-equal than value of <symbol2>, it returns 'y',
-    otherwise 'n'.
-(5) Returns the value of the expression. Used to override precedence.
-(6) Returns the result of (2-/expr/).
-(7) Returns the result of min(/expr/, /expr/).
-(8) Returns the result of max(/expr/, /expr/).
-
-An expression can have a value of 'n', 'm' or 'y' (or 0, 1, 2
-respectively for calculations). A menu entry becomes visible when its
-expression evaluates to 'm' or 'y'.
-
-There are two types of symbols: constant and non-constant symbols.
-Non-constant symbols are the most common ones and are defined with the
-'config' statement. Non-constant symbols consist entirely of alphanumeric
-characters or underscores.
-Constant symbols are only part of expressions. Constant symbols are
-always surrounded by single or double quotes. Within the quote, any
-other character is allowed and the quotes can be escaped using '\'.
-
-Menu structure
---------------
-
-The position of a menu entry in the tree is determined in two ways. First
-it can be specified explicitly:
-
-menu "Network device support"
-	depends on NET
-
-config NETDEVICES
-	...
-
-endmenu
-
-All entries within the "menu" ... "endmenu" block become a submenu of
-"Network device support". All subentries inherit the dependencies from
-the menu entry, e.g. this means the dependency "NET" is added to the
-dependency list of the config option NETDEVICES.
-
-The other way to generate the menu structure is done by analyzing the
-dependencies. If a menu entry somehow depends on the previous entry, it
-can be made a submenu of it. First, the previous (parent) symbol must
-be part of the dependency list and then one of these two conditions
-must be true:
-- the child entry must become invisible, if the parent is set to 'n'
-- the child entry must only be visible, if the parent is visible
-
-config MODULES
-	bool "Enable loadable module support"
-
-config MODVERSIONS
-	bool "Set version information on all module symbols"
-	depends on MODULES
-
-comment "module support disabled"
-	depends on !MODULES
-
-MODVERSIONS directly depends on MODULES, this means it's only visible if
-MODULES is different from 'n'. The comment on the other hand is only
-visible when MODULES is set to 'n'.
-
-
-Kconfig syntax
---------------
-
-The configuration file describes a series of menu entries, where every
-line starts with a keyword (except help texts). The following keywords
-end a menu entry:
-- config
-- menuconfig
-- choice/endchoice
-- comment
-- menu/endmenu
-- if/endif
-- source
-The first five also start the definition of a menu entry.
-
-config:
-
-	"config" <symbol>
-	<config options>
-
-This defines a config symbol <symbol> and accepts any of above
-attributes as options.
-
-menuconfig:
-	"menuconfig" <symbol>
-	<config options>
-
-This is similar to the simple config entry above, but it also gives a
-hint to front ends, that all suboptions should be displayed as a
-separate list of options. To make sure all the suboptions will really
-show up under the menuconfig entry and not outside of it, every item
-from the <config options> list must depend on the menuconfig symbol.
-In practice, this is achieved by using one of the next two constructs:
-
-(1):
-menuconfig M
-if M
-    config C1
-    config C2
-endif
-
-(2):
-menuconfig M
-config C1
-    depends on M
-config C2
-    depends on M
-
-In the following examples (3) and (4), C1 and C2 still have the M
-dependency, but will not appear under menuconfig M anymore, because
-of C0, which doesn't depend on M:
-
-(3):
-menuconfig M
-    config C0
-if M
-    config C1
-    config C2
-endif
-
-(4):
-menuconfig M
-config C0
-config C1
-    depends on M
-config C2
-    depends on M
-
-choices:
-
-	"choice" [symbol]
-	<choice options>
-	<choice block>
-	"endchoice"
-
-This defines a choice group and accepts any of the above attributes as
-options. A choice can only be of type bool or tristate.  If no type is
-specified for a choice, its type will be determined by the type of
-the first choice element in the group or remain unknown if none of the
-choice elements have a type specified, as well.
-
-While a boolean choice only allows a single config entry to be
-selected, a tristate choice also allows any number of config entries
-to be set to 'm'. This can be used if multiple drivers for a single
-hardware exists and only a single driver can be compiled/loaded into
-the kernel, but all drivers can be compiled as modules.
-
-A choice accepts another option "optional", which allows to set the
-choice to 'n' and no entry needs to be selected.
-If no [symbol] is associated with a choice, then you can not have multiple
-definitions of that choice. If a [symbol] is associated to the choice,
-then you may define the same choice (i.e. with the same entries) in another
-place.
-
-comment:
-
-	"comment" <prompt>
-	<comment options>
-
-This defines a comment which is displayed to the user during the
-configuration process and is also echoed to the output files. The only
-possible options are dependencies.
-
-menu:
-
-	"menu" <prompt>
-	<menu options>
-	<menu block>
-	"endmenu"
-
-This defines a menu block, see "Menu structure" above for more
-information. The only possible options are dependencies and "visible"
-attributes.
-
-if:
-
-	"if" <expr>
-	<if block>
-	"endif"
-
-This defines an if block. The dependency expression <expr> is appended
-to all enclosed menu entries.
-
-source:
-
-	"source" <prompt>
-
-This reads the specified configuration file. This file is always parsed.
-
-mainmenu:
-
-	"mainmenu" <prompt>
-
-This sets the config program's title bar if the config program chooses
-to use it. It should be placed at the top of the configuration, before any
-other statement.
-
-'#' Kconfig source file comment:
-
-An unquoted '#' character anywhere in a source file line indicates
-the beginning of a source file comment.  The remainder of that line
-is a comment.
-
-
-Kconfig hints
--------------
-This is a collection of Kconfig tips, most of which aren't obvious at
-first glance and most of which have become idioms in several Kconfig
-files.
-
-Adding common features and make the usage configurable
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-It is a common idiom to implement a feature/functionality that are
-relevant for some architectures but not all.
-The recommended way to do so is to use a config variable named HAVE_*
-that is defined in a common Kconfig file and selected by the relevant
-architectures.
-An example is the generic IOMAP functionality.
-
-We would in lib/Kconfig see:
-
-# Generic IOMAP is used to ...
-config HAVE_GENERIC_IOMAP
-
-config GENERIC_IOMAP
-	depends on HAVE_GENERIC_IOMAP && FOO
-
-And in lib/Makefile we would see:
-obj-$(CONFIG_GENERIC_IOMAP) += iomap.o
-
-For each architecture using the generic IOMAP functionality we would see:
-
-config X86
-	select ...
-	select HAVE_GENERIC_IOMAP
-	select ...
-
-Note: we use the existing config option and avoid creating a new
-config variable to select HAVE_GENERIC_IOMAP.
-
-Note: the use of the internal config variable HAVE_GENERIC_IOMAP, it is
-introduced to overcome the limitation of select which will force a
-config option to 'y' no matter the dependencies.
-The dependencies are moved to the symbol GENERIC_IOMAP and we avoid the
-situation where select forces a symbol equals to 'y'.
-
-Adding features that need compiler support
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-There are several features that need compiler support. The recommended way
-to describe the dependency on the compiler feature is to use "depends on"
-followed by a test macro.
-
-config STACKPROTECTOR
-	bool "Stack Protector buffer overflow detection"
-	depends on $(cc-option,-fstack-protector)
-	...
-
-If you need to expose a compiler capability to makefiles and/or C source files,
-CC_HAS_ is the recommended prefix for the config option.
-
-config CC_HAS_STACKPROTECTOR_NONE
-	def_bool $(cc-option,-fno-stack-protector)
-
-Build as module only
-~~~~~~~~~~~~~~~~~~~~
-To restrict a component build to module-only, qualify its config symbol
-with "depends on m".  E.g.:
-
-config FOO
-	depends on BAR && m
-
-limits FOO to module (=m) or disabled (=n).
-
-Kconfig recursive dependency limitations
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-If you've hit the Kconfig error: "recursive dependency detected" you've run
-into a recursive dependency issue with Kconfig, a recursive dependency can be
-summarized as a circular dependency. The kconfig tools need to ensure that
-Kconfig files comply with specified configuration requirements. In order to do
-that kconfig must determine the values that are possible for all Kconfig
-symbols, this is currently not possible if there is a circular relation
-between two or more Kconfig symbols. For more details refer to the "Simple
-Kconfig recursive issue" subsection below. Kconfig does not do recursive
-dependency resolution; this has a few implications for Kconfig file writers.
-We'll first explain why this issues exists and then provide an example
-technical limitation which this brings upon Kconfig developers. Eager
-developers wishing to try to address this limitation should read the next
-subsections.
-
-Simple Kconfig recursive issue
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-Read: Documentation/kbuild/Kconfig.recursion-issue-01
-
-Test with:
-
-make KBUILD_KCONFIG=Documentation/kbuild/Kconfig.recursion-issue-01 allnoconfig
-
-Cumulative Kconfig recursive issue
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-Read: Documentation/kbuild/Kconfig.recursion-issue-02
-
-Test with:
-
-make KBUILD_KCONFIG=Documentation/kbuild/Kconfig.recursion-issue-02 allnoconfig
-
-Practical solutions to kconfig recursive issue
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-Developers who run into the recursive Kconfig issue have two options
-at their disposal. We document them below and also provide a list of
-historical issues resolved through these different solutions.
-
-  a) Remove any superfluous "select FOO" or "depends on FOO"
-  b) Match dependency semantics:
-	b1) Swap all "select FOO" to "depends on FOO" or,
-	b2) Swap all "depends on FOO" to "select FOO"
-
-The resolution to a) can be tested with the sample Kconfig file
-Documentation/kbuild/Kconfig.recursion-issue-01 through the removal
-of the "select CORE" from CORE_BELL_A_ADVANCED as that is implicit already
-since CORE_BELL_A depends on CORE. At times it may not be possible to remove
-some dependency criteria, for such cases you can work with solution b).
-
-The two different resolutions for b) can be tested in the sample Kconfig file
-Documentation/kbuild/Kconfig.recursion-issue-02.
-
-Below is a list of examples of prior fixes for these types of recursive issues;
-all errors appear to involve one or more select's and one or more "depends on".
-
-commit          fix
-======          ===
-06b718c01208    select A -> depends on A
-c22eacfe82f9    depends on A -> depends on B
-6a91e854442c    select A -> depends on A
-118c565a8f2e    select A -> select B
-f004e5594705    select A -> depends on A
-c7861f37b4c6    depends on A -> (null)
-80c69915e5fb    select A -> (null)              (1)
-c2218e26c0d0    select A -> depends on A        (1)
-d6ae99d04e1c    select A -> depends on A
-95ca19cf8cbf    select A -> depends on A
-8f057d7bca54    depends on A -> (null)
-8f057d7bca54    depends on A -> select A
-a0701f04846e    select A -> depends on A
-0c8b92f7f259    depends on A -> (null)
-e4e9e0540928    select A -> depends on A        (2)
-7453ea886e87    depends on A > (null)           (1)
-7b1fff7e4fdf    select A -> depends on A
-86c747d2a4f0    select A -> depends on A
-d9f9ab51e55e    select A -> depends on A
-0c51a4d8abd6    depends on A -> select A        (3)
-e98062ed6dc4    select A -> depends on A        (3)
-91e5d284a7f1    select A -> (null)
-
-(1) Partial (or no) quote of error.
-(2) That seems to be the gist of that fix.
-(3) Same error.
-
-Future kconfig work
-~~~~~~~~~~~~~~~~~~~
-
-Work on kconfig is welcomed on both areas of clarifying semantics and on
-evaluating the use of a full SAT solver for it. A full SAT solver can be
-desirable to enable more complex dependency mappings and / or queries,
-for instance on possible use case for a SAT solver could be that of handling
-the current known recursive dependency issues. It is not known if this would
-address such issues but such evaluation is desirable. If support for a full SAT
-solver proves too complex or that it cannot address recursive dependency issues
-Kconfig should have at least clear and well defined semantics which also
-addresses and documents limitations or requirements such as the ones dealing
-with recursive dependencies.
-
-Further work on both of these areas is welcomed on Kconfig. We elaborate
-on both of these in the next two subsections.
-
-Semantics of Kconfig
-~~~~~~~~~~~~~~~~~~~~
-
-The use of Kconfig is broad, Linux is now only one of Kconfig's users:
-one study has completed a broad analysis of Kconfig use in 12 projects [0].
-Despite its widespread use, and although this document does a reasonable job
-in documenting basic Kconfig syntax a more precise definition of Kconfig
-semantics is welcomed. One project deduced Kconfig semantics through
-the use of the xconfig configurator [1]. Work should be done to confirm if
-the deduced semantics matches our intended Kconfig design goals.
-
-Having well defined semantics can be useful for tools for practical
-evaluation of depenencies, for instance one such use known case was work to
-express in boolean abstraction of the inferred semantics of Kconfig to
-translate Kconfig logic into boolean formulas and run a SAT solver on this to
-find dead code / features (always inactive), 114 dead features were found in
-Linux using this methodology [1] (Section 8: Threats to validity).
-
-Confirming this could prove useful as Kconfig stands as one of the the leading
-industrial variability modeling languages [1] [2]. Its study would help
-evaluate practical uses of such languages, their use was only theoretical
-and real world requirements were not well understood. As it stands though
-only reverse engineering techniques have been used to deduce semantics from
-variability modeling languages such as Kconfig [3].
-
-[0] http://www.eng.uwaterloo.ca/~shshe/kconfig_semantics.pdf
-[1] http://gsd.uwaterloo.ca/sites/default/files/vm-2013-berger.pdf
-[2] http://gsd.uwaterloo.ca/sites/default/files/ase241-berger_0.pdf
-[3] http://gsd.uwaterloo.ca/sites/default/files/icse2011.pdf
-
-Full SAT solver for Kconfig
-~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-Although SAT solvers [0] haven't yet been used by Kconfig directly, as noted in
-the previous subsection, work has been done however to express in boolean
-abstraction the inferred semantics of Kconfig to translate Kconfig logic into
-boolean formulas and run a SAT solver on it [1]. Another known related project
-is CADOS [2] (former VAMOS [3]) and the tools, mainly undertaker [4], which has
-been introduced first with [5].  The basic concept of undertaker is to exract
-variability models from Kconfig, and put them together with a propositional
-formula extracted from CPP #ifdefs and build-rules into a SAT solver in order
-to find dead code, dead files, and dead symbols. If using a SAT solver is
-desirable on Kconfig one approach would be to evaluate repurposing such efforts
-somehow on Kconfig. There is enough interest from mentors of existing projects
-to not only help advise how to integrate this work upstream but also help
-maintain it long term. Interested developers should visit:
-
-http://kernelnewbies.org/KernelProjects/kconfig-sat
-
-[0] http://www.cs.cornell.edu/~sabhar/chapters/SATSolvers-KR-Handbook.pdf
-[1] http://gsd.uwaterloo.ca/sites/default/files/vm-2013-berger.pdf
-[2] https://cados.cs.fau.de
-[3] https://vamos.cs.fau.de
-[4] https://undertaker.cs.fau.de
-[5] https://www4.cs.fau.de/Publications/2011/tartler_11_eurosys.pdf
diff --git a/Documentation/kbuild/kconfig-macro-language.rst b/Documentation/kbuild/kconfig-macro-language.rst
new file mode 100644
index 000000000000..35b3263b7e40
--- /dev/null
+++ b/Documentation/kbuild/kconfig-macro-language.rst
@@ -0,0 +1,247 @@
+======================
+Kconfig macro language
+======================
+
+Concept
+-------
+
+The basic idea was inspired by Make. When we look at Make, we notice sort of
+two languages in one. One language describes dependency graphs consisting of
+targets and prerequisites. The other is a macro language for performing textual
+substitution.
+
+There is clear distinction between the two language stages. For example, you
+can write a makefile like follows::
+
+    APP := foo
+    SRC := foo.c
+    CC := gcc
+
+    $(APP): $(SRC)
+            $(CC) -o $(APP) $(SRC)
+
+The macro language replaces the variable references with their expanded form,
+and handles as if the source file were input like follows::
+
+    foo: foo.c
+            gcc -o foo foo.c
+
+Then, Make analyzes the dependency graph and determines the targets to be
+updated.
+
+The idea is quite similar in Kconfig - it is possible to describe a Kconfig
+file like this::
+
+    CC := gcc
+
+    config CC_HAS_FOO
+            def_bool $(shell, $(srctree)/scripts/gcc-check-foo.sh $(CC))
+
+The macro language in Kconfig processes the source file into the following
+intermediate::
+
+    config CC_HAS_FOO
+            def_bool y
+
+Then, Kconfig moves onto the evaluation stage to resolve inter-symbol
+dependency as explained in kconfig-language.txt.
+
+
+Variables
+---------
+
+Like in Make, a variable in Kconfig works as a macro variable.  A macro
+variable is expanded "in place" to yield a text string that may then be
+expanded further. To get the value of a variable, enclose the variable name in
+$( ). The parentheses are required even for single-letter variable names; $X is
+a syntax error. The curly brace form as in ${CC} is not supported either.
+
+There are two types of variables: simply expanded variables and recursively
+expanded variables.
+
+A simply expanded variable is defined using the := assignment operator. Its
+righthand side is expanded immediately upon reading the line from the Kconfig
+file.
+
+A recursively expanded variable is defined using the = assignment operator.
+Its righthand side is simply stored as the value of the variable without
+expanding it in any way. Instead, the expansion is performed when the variable
+is used.
+
+There is another type of assignment operator; += is used to append text to a
+variable. The righthand side of += is expanded immediately if the lefthand
+side was originally defined as a simple variable. Otherwise, its evaluation is
+deferred.
+
+The variable reference can take parameters, in the following form::
+
+  $(name,arg1,arg2,arg3)
+
+You can consider the parameterized reference as a function. (more precisely,
+"user-defined function" in contrast to "built-in function" listed below).
+
+Useful functions must be expanded when they are used since the same function is
+expanded differently if different parameters are passed. Hence, a user-defined
+function is defined using the = assignment operator. The parameters are
+referenced within the body definition with $(1), $(2), etc.
+
+In fact, recursively expanded variables and user-defined functions are the same
+internally. (In other words, "variable" is "function with zero argument".)
+When we say "variable" in a broad sense, it includes "user-defined function".
+
+
+Built-in functions
+------------------
+
+Like Make, Kconfig provides several built-in functions. Every function takes a
+particular number of arguments.
+
+In Make, every built-in function takes at least one argument. Kconfig allows
+zero argument for built-in functions, such as $(fileno), $(lineno). You could
+consider those as "built-in variable", but it is just a matter of how we call
+it after all. Let's say "built-in function" here to refer to natively supported
+functionality.
+
+Kconfig currently supports the following built-in functions.
+
+ - $(shell,command)
+
+  The "shell" function accepts a single argument that is expanded and passed
+  to a subshell for execution. The standard output of the command is then read
+  and returned as the value of the function. Every newline in the output is
+  replaced with a space. Any trailing newlines are deleted. The standard error
+  is not returned, nor is any program exit status.
+
+ - $(info,text)
+
+  The "info" function takes a single argument and prints it to stdout.
+  It evaluates to an empty string.
+
+ - $(warning-if,condition,text)
+
+  The "warning-if" function takes two arguments. If the condition part is "y",
+  the text part is sent to stderr. The text is prefixed with the name of the
+  current Kconfig file and the current line number.
+
+ - $(error-if,condition,text)
+
+  The "error-if" function is similar to "warning-if", but it terminates the
+  parsing immediately if the condition part is "y".
+
+ - $(filename)
+
+  The 'filename' takes no argument, and $(filename) is expanded to the file
+  name being parsed.
+
+ - $(lineno)
+
+  The 'lineno' takes no argument, and $(lineno) is expanded to the line number
+  being parsed.
+
+
+Make vs Kconfig
+---------------
+
+Kconfig adopts Make-like macro language, but the function call syntax is
+slightly different.
+
+A function call in Make looks like this::
+
+  $(func-name arg1,arg2,arg3)
+
+The function name and the first argument are separated by at least one
+whitespace. Then, leading whitespaces are trimmed from the first argument,
+while whitespaces in the other arguments are kept. You need to use a kind of
+trick to start the first parameter with spaces. For example, if you want
+to make "info" function print "  hello", you can write like follows::
+
+  empty :=
+  space := $(empty) $(empty)
+  $(info $(space)$(space)hello)
+
+Kconfig uses only commas for delimiters, and keeps all whitespaces in the
+function call. Some people prefer putting a space after each comma delimiter::
+
+  $(func-name, arg1, arg2, arg3)
+
+In this case, "func-name" will receive " arg1", " arg2", " arg3". The presence
+of leading spaces may matter depending on the function. The same applies to
+Make - for example, $(subst .c, .o, $(sources)) is a typical mistake; it
+replaces ".c" with " .o".
+
+In Make, a user-defined function is referenced by using a built-in function,
+'call', like this::
+
+    $(call my-func,arg1,arg2,arg3)
+
+Kconfig invokes user-defined functions and built-in functions in the same way.
+The omission of 'call' makes the syntax shorter.
+
+In Make, some functions treat commas verbatim instead of argument separators.
+For example, $(shell echo hello, world) runs the command "echo hello, world".
+Likewise, $(info hello, world) prints "hello, world" to stdout. You could say
+this is _useful_ inconsistency.
+
+In Kconfig, for simpler implementation and grammatical consistency, commas that
+appear in the $( ) context are always delimiters. It means::
+
+  $(shell, echo hello, world)
+
+is an error because it is passing two parameters where the 'shell' function
+accepts only one. To pass commas in arguments, you can use the following trick::
+
+  comma := ,
+  $(shell, echo hello$(comma) world)
+
+
+Caveats
+-------
+
+A variable (or function) cannot be expanded across tokens. So, you cannot use
+a variable as a shorthand for an expression that consists of multiple tokens.
+The following works::
+
+    RANGE_MIN := 1
+    RANGE_MAX := 3
+
+    config FOO
+            int "foo"
+            range $(RANGE_MIN) $(RANGE_MAX)
+
+But, the following does not work::
+
+    RANGES := 1 3
+
+    config FOO
+            int "foo"
+            range $(RANGES)
+
+A variable cannot be expanded to any keyword in Kconfig.  The following does
+not work::
+
+    MY_TYPE := tristate
+
+    config FOO
+            $(MY_TYPE) "foo"
+            default y
+
+Obviously from the design, $(shell command) is expanded in the textual
+substitution phase. You cannot pass symbols to the 'shell' function.
+
+The following does not work as expected::
+
+    config ENDIAN_FLAG
+            string
+            default "-mbig-endian" if CPU_BIG_ENDIAN
+            default "-mlittle-endian" if CPU_LITTLE_ENDIAN
+
+    config CC_HAS_ENDIAN_FLAG
+            def_bool $(shell $(srctree)/scripts/gcc-check-flag ENDIAN_FLAG)
+
+Instead, you can do like follows so that any function call is statically
+expanded::
+
+    config CC_HAS_ENDIAN_FLAG
+            bool
+            default $(shell $(srctree)/scripts/gcc-check-flag -mbig-endian) if CPU_BIG_ENDIAN
+            default $(shell $(srctree)/scripts/gcc-check-flag -mlittle-endian) if CPU_LITTLE_ENDIAN
diff --git a/Documentation/kbuild/kconfig-macro-language.txt b/Documentation/kbuild/kconfig-macro-language.txt
deleted file mode 100644
index 07da2ea68dce..000000000000
--- a/Documentation/kbuild/kconfig-macro-language.txt
+++ /dev/null
@@ -1,242 +0,0 @@
-Concept
--------
-
-The basic idea was inspired by Make. When we look at Make, we notice sort of
-two languages in one. One language describes dependency graphs consisting of
-targets and prerequisites. The other is a macro language for performing textual
-substitution.
-
-There is clear distinction between the two language stages. For example, you
-can write a makefile like follows:
-
-    APP := foo
-    SRC := foo.c
-    CC := gcc
-
-    $(APP): $(SRC)
-            $(CC) -o $(APP) $(SRC)
-
-The macro language replaces the variable references with their expanded form,
-and handles as if the source file were input like follows:
-
-    foo: foo.c
-            gcc -o foo foo.c
-
-Then, Make analyzes the dependency graph and determines the targets to be
-updated.
-
-The idea is quite similar in Kconfig - it is possible to describe a Kconfig
-file like this:
-
-    CC := gcc
-
-    config CC_HAS_FOO
-            def_bool $(shell, $(srctree)/scripts/gcc-check-foo.sh $(CC))
-
-The macro language in Kconfig processes the source file into the following
-intermediate:
-
-    config CC_HAS_FOO
-            def_bool y
-
-Then, Kconfig moves onto the evaluation stage to resolve inter-symbol
-dependency as explained in kconfig-language.txt.
-
-
-Variables
----------
-
-Like in Make, a variable in Kconfig works as a macro variable.  A macro
-variable is expanded "in place" to yield a text string that may then be
-expanded further. To get the value of a variable, enclose the variable name in
-$( ). The parentheses are required even for single-letter variable names; $X is
-a syntax error. The curly brace form as in ${CC} is not supported either.
-
-There are two types of variables: simply expanded variables and recursively
-expanded variables.
-
-A simply expanded variable is defined using the := assignment operator. Its
-righthand side is expanded immediately upon reading the line from the Kconfig
-file.
-
-A recursively expanded variable is defined using the = assignment operator.
-Its righthand side is simply stored as the value of the variable without
-expanding it in any way. Instead, the expansion is performed when the variable
-is used.
-
-There is another type of assignment operator; += is used to append text to a
-variable. The righthand side of += is expanded immediately if the lefthand
-side was originally defined as a simple variable. Otherwise, its evaluation is
-deferred.
-
-The variable reference can take parameters, in the following form:
-
-  $(name,arg1,arg2,arg3)
-
-You can consider the parameterized reference as a function. (more precisely,
-"user-defined function" in contrast to "built-in function" listed below).
-
-Useful functions must be expanded when they are used since the same function is
-expanded differently if different parameters are passed. Hence, a user-defined
-function is defined using the = assignment operator. The parameters are
-referenced within the body definition with $(1), $(2), etc.
-
-In fact, recursively expanded variables and user-defined functions are the same
-internally. (In other words, "variable" is "function with zero argument".)
-When we say "variable" in a broad sense, it includes "user-defined function".
-
-
-Built-in functions
-------------------
-
-Like Make, Kconfig provides several built-in functions. Every function takes a
-particular number of arguments.
-
-In Make, every built-in function takes at least one argument. Kconfig allows
-zero argument for built-in functions, such as $(fileno), $(lineno). You could
-consider those as "built-in variable", but it is just a matter of how we call
-it after all. Let's say "built-in function" here to refer to natively supported
-functionality.
-
-Kconfig currently supports the following built-in functions.
-
- - $(shell,command)
-
-  The "shell" function accepts a single argument that is expanded and passed
-  to a subshell for execution. The standard output of the command is then read
-  and returned as the value of the function. Every newline in the output is
-  replaced with a space. Any trailing newlines are deleted. The standard error
-  is not returned, nor is any program exit status.
-
- - $(info,text)
-
-  The "info" function takes a single argument and prints it to stdout.
-  It evaluates to an empty string.
-
- - $(warning-if,condition,text)
-
-  The "warning-if" function takes two arguments. If the condition part is "y",
-  the text part is sent to stderr. The text is prefixed with the name of the
-  current Kconfig file and the current line number.
-
- - $(error-if,condition,text)
-
-  The "error-if" function is similar to "warning-if", but it terminates the
-  parsing immediately if the condition part is "y".
-
- - $(filename)
-
-  The 'filename' takes no argument, and $(filename) is expanded to the file
-  name being parsed.
-
- - $(lineno)
-
-  The 'lineno' takes no argument, and $(lineno) is expanded to the line number
-  being parsed.
-
-
-Make vs Kconfig
----------------
-
-Kconfig adopts Make-like macro language, but the function call syntax is
-slightly different.
-
-A function call in Make looks like this:
-
-  $(func-name arg1,arg2,arg3)
-
-The function name and the first argument are separated by at least one
-whitespace. Then, leading whitespaces are trimmed from the first argument,
-while whitespaces in the other arguments are kept. You need to use a kind of
-trick to start the first parameter with spaces. For example, if you want
-to make "info" function print "  hello", you can write like follows:
-
-  empty :=
-  space := $(empty) $(empty)
-  $(info $(space)$(space)hello)
-
-Kconfig uses only commas for delimiters, and keeps all whitespaces in the
-function call. Some people prefer putting a space after each comma delimiter:
-
-  $(func-name, arg1, arg2, arg3)
-
-In this case, "func-name" will receive " arg1", " arg2", " arg3". The presence
-of leading spaces may matter depending on the function. The same applies to
-Make - for example, $(subst .c, .o, $(sources)) is a typical mistake; it
-replaces ".c" with " .o".
-
-In Make, a user-defined function is referenced by using a built-in function,
-'call', like this:
-
-    $(call my-func,arg1,arg2,arg3)
-
-Kconfig invokes user-defined functions and built-in functions in the same way.
-The omission of 'call' makes the syntax shorter.
-
-In Make, some functions treat commas verbatim instead of argument separators.
-For example, $(shell echo hello, world) runs the command "echo hello, world".
-Likewise, $(info hello, world) prints "hello, world" to stdout. You could say
-this is _useful_ inconsistency.
-
-In Kconfig, for simpler implementation and grammatical consistency, commas that
-appear in the $( ) context are always delimiters. It means
-
-  $(shell, echo hello, world)
-
-is an error because it is passing two parameters where the 'shell' function
-accepts only one. To pass commas in arguments, you can use the following trick:
-
-  comma := ,
-  $(shell, echo hello$(comma) world)
-
-
-Caveats
--------
-
-A variable (or function) cannot be expanded across tokens. So, you cannot use
-a variable as a shorthand for an expression that consists of multiple tokens.
-The following works:
-
-    RANGE_MIN := 1
-    RANGE_MAX := 3
-
-    config FOO
-            int "foo"
-            range $(RANGE_MIN) $(RANGE_MAX)
-
-But, the following does not work:
-
-    RANGES := 1 3
-
-    config FOO
-            int "foo"
-            range $(RANGES)
-
-A variable cannot be expanded to any keyword in Kconfig.  The following does
-not work:
-
-    MY_TYPE := tristate
-
-    config FOO
-            $(MY_TYPE) "foo"
-            default y
-
-Obviously from the design, $(shell command) is expanded in the textual
-substitution phase. You cannot pass symbols to the 'shell' function.
-The following does not work as expected.
-
-    config ENDIAN_FLAG
-            string
-            default "-mbig-endian" if CPU_BIG_ENDIAN
-            default "-mlittle-endian" if CPU_LITTLE_ENDIAN
-
-    config CC_HAS_ENDIAN_FLAG
-            def_bool $(shell $(srctree)/scripts/gcc-check-flag ENDIAN_FLAG)
-
-Instead, you can do like follows so that any function call is statically
-expanded.
-
-    config CC_HAS_ENDIAN_FLAG
-            bool
-            default $(shell $(srctree)/scripts/gcc-check-flag -mbig-endian) if CPU_BIG_ENDIAN
-            default $(shell $(srctree)/scripts/gcc-check-flag -mlittle-endian) if CPU_LITTLE_ENDIAN
diff --git a/Documentation/kbuild/kconfig.rst b/Documentation/kbuild/kconfig.rst
new file mode 100644
index 000000000000..88129af7e539
--- /dev/null
+++ b/Documentation/kbuild/kconfig.rst
@@ -0,0 +1,300 @@
+===================
+Kconfig make config
+===================
+
+This file contains some assistance for using `make *config`.
+
+Use "make help" to list all of the possible configuration targets.
+
+The xconfig ('qconf'), menuconfig ('mconf'), and nconfig ('nconf')
+programs also have embedded help text.  Be sure to check that for
+navigation, search, and other general help text.
+
+General
+-------
+
+New kernel releases often introduce new config symbols.  Often more
+important, new kernel releases may rename config symbols.  When
+this happens, using a previously working .config file and running
+"make oldconfig" won't necessarily produce a working new kernel
+for you, so you may find that you need to see what NEW kernel
+symbols have been introduced.
+
+To see a list of new config symbols, use::
+
+	cp user/some/old.config .config
+	make listnewconfig
+
+and the config program will list any new symbols, one per line.
+
+Alternatively, you can use the brute force method::
+
+	make oldconfig
+	scripts/diffconfig .config.old .config | less
+
+----------------------------------------------------------------------
+
+Environment variables for `*config`
+
+KCONFIG_CONFIG
+--------------
+This environment variable can be used to specify a default kernel config
+file name to override the default name of ".config".
+
+KCONFIG_OVERWRITECONFIG
+-----------------------
+If you set KCONFIG_OVERWRITECONFIG in the environment, Kconfig will not
+break symlinks when .config is a symlink to somewhere else.
+
+`CONFIG_`
+---------
+If you set `CONFIG_` in the environment, Kconfig will prefix all symbols
+with its value when saving the configuration, instead of using the default,
+`CONFIG_`.
+
+----------------------------------------------------------------------
+
+Environment variables for '{allyes/allmod/allno/rand}config'
+
+KCONFIG_ALLCONFIG
+-----------------
+(partially based on lkml email from/by Rob Landley, re: miniconfig)
+
+--------------------------------------------------
+
+The allyesconfig/allmodconfig/allnoconfig/randconfig variants can also
+use the environment variable KCONFIG_ALLCONFIG as a flag or a filename
+that contains config symbols that the user requires to be set to a
+specific value.  If KCONFIG_ALLCONFIG is used without a filename where
+KCONFIG_ALLCONFIG == "" or KCONFIG_ALLCONFIG == "1", `make *config`
+checks for a file named "all{yes/mod/no/def/random}.config"
+(corresponding to the `*config` command that was used) for symbol values
+that are to be forced.  If this file is not found, it checks for a
+file named "all.config" to contain forced values.
+
+This enables you to create "miniature" config (miniconfig) or custom
+config files containing just the config symbols that you are interested
+in.  Then the kernel config system generates the full .config file,
+including symbols of your miniconfig file.
+
+This 'KCONFIG_ALLCONFIG' file is a config file which contains
+(usually a subset of all) preset config symbols.  These variable
+settings are still subject to normal dependency checks.
+
+Examples::
+
+	KCONFIG_ALLCONFIG=custom-notebook.config make allnoconfig
+
+or::
+
+	KCONFIG_ALLCONFIG=mini.config make allnoconfig
+
+or::
+
+	make KCONFIG_ALLCONFIG=mini.config allnoconfig
+
+These examples will disable most options (allnoconfig) but enable or
+disable the options that are explicitly listed in the specified
+mini-config files.
+
+----------------------------------------------------------------------
+
+Environment variables for 'randconfig'
+
+KCONFIG_SEED
+------------
+You can set this to the integer value used to seed the RNG, if you want
+to somehow debug the behaviour of the kconfig parser/frontends.
+If not set, the current time will be used.
+
+KCONFIG_PROBABILITY
+-------------------
+This variable can be used to skew the probabilities. This variable can
+be unset or empty, or set to three different formats:
+
+    =======================     ==================  =====================
+	KCONFIG_PROBABILITY     y:n split           y:m:n split
+    =======================     ==================  =====================
+	unset or empty          50  : 50            33  : 33  : 34
+	N                        N  : 100-N         N/2 : N/2 : 100-N
+    [1] N:M                     N+M : 100-(N+M)      N  :  M  : 100-(N+M)
+    [2] N:M:L                    N  : 100-N          M  :  L  : 100-(M+L)
+    =======================     ==================  =====================
+
+where N, M and L are integers (in base 10) in the range [0,100], and so
+that:
+
+    [1] N+M is in the range [0,100]
+
+    [2] M+L is in the range [0,100]
+
+Examples::
+
+	KCONFIG_PROBABILITY=10
+		10% of booleans will be set to 'y', 90% to 'n'
+		5% of tristates will be set to 'y', 5% to 'm', 90% to 'n'
+	KCONFIG_PROBABILITY=15:25
+		40% of booleans will be set to 'y', 60% to 'n'
+		15% of tristates will be set to 'y', 25% to 'm', 60% to 'n'
+	KCONFIG_PROBABILITY=10:15:15
+		10% of booleans will be set to 'y', 90% to 'n'
+		15% of tristates will be set to 'y', 15% to 'm', 70% to 'n'
+
+----------------------------------------------------------------------
+
+Environment variables for 'syncconfig'
+
+KCONFIG_NOSILENTUPDATE
+----------------------
+If this variable has a non-blank value, it prevents silent kernel
+config updates (requires explicit updates).
+
+KCONFIG_AUTOCONFIG
+------------------
+This environment variable can be set to specify the path & name of the
+"auto.conf" file.  Its default value is "include/config/auto.conf".
+
+KCONFIG_TRISTATE
+----------------
+This environment variable can be set to specify the path & name of the
+"tristate.conf" file.  Its default value is "include/config/tristate.conf".
+
+KCONFIG_AUTOHEADER
+------------------
+This environment variable can be set to specify the path & name of the
+"autoconf.h" (header) file.
+Its default value is "include/generated/autoconf.h".
+
+
+----------------------------------------------------------------------
+
+menuconfig
+----------
+
+SEARCHING for CONFIG symbols
+
+Searching in menuconfig:
+
+	The Search function searches for kernel configuration symbol
+	names, so you have to know something close to what you are
+	looking for.
+
+	Example::
+
+		/hotplug
+		This lists all config symbols that contain "hotplug",
+		e.g., HOTPLUG_CPU, MEMORY_HOTPLUG.
+
+	For search help, enter / followed by TAB-TAB (to highlight
+	<Help>) and Enter.  This will tell you that you can also use
+	regular expressions (regexes) in the search string, so if you
+	are not interested in MEMORY_HOTPLUG, you could try::
+
+		/^hotplug
+
+	When searching, symbols are sorted thus:
+
+	  - first, exact matches, sorted alphabetically (an exact match
+	    is when the search matches the complete symbol name);
+	  - then, other matches, sorted alphabetically.
+
+	For example: ^ATH.K matches:
+
+	    ATH5K ATH9K ATH5K_AHB ATH5K_DEBUG [...] ATH6KL ATH6KL_DEBUG
+	    [...] ATH9K_AHB ATH9K_BTCOEX_SUPPORT ATH9K_COMMON [...]
+
+	of which only ATH5K and ATH9K match exactly and so are sorted
+	first (and in alphabetical order), then come all other symbols,
+	sorted in alphabetical order.
+
+----------------------------------------------------------------------
+
+User interface options for 'menuconfig'
+
+MENUCONFIG_COLOR
+----------------
+It is possible to select different color themes using the variable
+MENUCONFIG_COLOR.  To select a theme use::
+
+	make MENUCONFIG_COLOR=<theme> menuconfig
+
+Available themes are::
+
+  - mono       => selects colors suitable for monochrome displays
+  - blackbg    => selects a color scheme with black background
+  - classic    => theme with blue background. The classic look
+  - bluetitle  => a LCD friendly version of classic. (default)
+
+MENUCONFIG_MODE
+---------------
+This mode shows all sub-menus in one large tree.
+
+Example::
+
+	make MENUCONFIG_MODE=single_menu menuconfig
+
+----------------------------------------------------------------------
+
+nconfig
+-------
+
+nconfig is an alternate text-based configurator.  It lists function
+keys across the bottom of the terminal (window) that execute commands.
+You can also just use the corresponding numeric key to execute the
+commands unless you are in a data entry window.  E.g., instead of F6
+for Save, you can just press 6.
+
+Use F1 for Global help or F3 for the Short help menu.
+
+Searching in nconfig:
+
+	You can search either in the menu entry "prompt" strings
+	or in the configuration symbols.
+
+	Use / to begin a search through the menu entries.  This does
+	not support regular expressions.  Use <Down> or <Up> for
+	Next hit and Previous hit, respectively.  Use <Esc> to
+	terminate the search mode.
+
+	F8 (SymSearch) searches the configuration symbols for the
+	given string or regular expression (regex).
+
+NCONFIG_MODE
+------------
+This mode shows all sub-menus in one large tree.
+
+Example::
+	make NCONFIG_MODE=single_menu nconfig
+
+----------------------------------------------------------------------
+
+xconfig
+-------
+
+Searching in xconfig:
+
+	The Search function searches for kernel configuration symbol
+	names, so you have to know something close to what you are
+	looking for.
+
+	Example:
+		Ctrl-F hotplug
+	or
+		Menu: File, Search, hotplug
+
+	lists all config symbol entries that contain "hotplug" in
+	the symbol name.  In this Search dialog, you may change the
+	config setting for any of the entries that are not grayed out.
+	You can also enter a different search string without having
+	to return to the main menu.
+
+
+----------------------------------------------------------------------
+
+gconfig
+-------
+
+Searching in gconfig:
+
+	There is no search command in gconfig.  However, gconfig does
+	have several different viewing choices, modes, and options.
diff --git a/Documentation/kbuild/kconfig.txt b/Documentation/kbuild/kconfig.txt
deleted file mode 100644
index 68c82914c0f3..000000000000
--- a/Documentation/kbuild/kconfig.txt
+++ /dev/null
@@ -1,272 +0,0 @@
-This file contains some assistance for using "make *config".
-
-Use "make help" to list all of the possible configuration targets.
-
-The xconfig ('qconf'), menuconfig ('mconf'), and nconfig ('nconf')
-programs also have embedded help text.  Be sure to check that for
-navigation, search, and other general help text.
-
-======================================================================
-General
---------------------------------------------------
-
-New kernel releases often introduce new config symbols.  Often more
-important, new kernel releases may rename config symbols.  When
-this happens, using a previously working .config file and running
-"make oldconfig" won't necessarily produce a working new kernel
-for you, so you may find that you need to see what NEW kernel
-symbols have been introduced.
-
-To see a list of new config symbols, use
-
-	cp user/some/old.config .config
-	make listnewconfig
-
-and the config program will list any new symbols, one per line.
-
-Alternatively, you can use the brute force method:
-
-	make oldconfig
-	scripts/diffconfig .config.old .config | less
-
-______________________________________________________________________
-Environment variables for '*config'
-
-KCONFIG_CONFIG
---------------------------------------------------
-This environment variable can be used to specify a default kernel config
-file name to override the default name of ".config".
-
-KCONFIG_OVERWRITECONFIG
---------------------------------------------------
-If you set KCONFIG_OVERWRITECONFIG in the environment, Kconfig will not
-break symlinks when .config is a symlink to somewhere else.
-
-CONFIG_
---------------------------------------------------
-If you set CONFIG_ in the environment, Kconfig will prefix all symbols
-with its value when saving the configuration, instead of using the default,
-"CONFIG_".
-
-______________________________________________________________________
-Environment variables for '{allyes/allmod/allno/rand}config'
-
-KCONFIG_ALLCONFIG
---------------------------------------------------
-(partially based on lkml email from/by Rob Landley, re: miniconfig)
---------------------------------------------------
-The allyesconfig/allmodconfig/allnoconfig/randconfig variants can also
-use the environment variable KCONFIG_ALLCONFIG as a flag or a filename
-that contains config symbols that the user requires to be set to a
-specific value.  If KCONFIG_ALLCONFIG is used without a filename where
-KCONFIG_ALLCONFIG == "" or KCONFIG_ALLCONFIG == "1", "make *config"
-checks for a file named "all{yes/mod/no/def/random}.config"
-(corresponding to the *config command that was used) for symbol values
-that are to be forced.  If this file is not found, it checks for a
-file named "all.config" to contain forced values.
-
-This enables you to create "miniature" config (miniconfig) or custom
-config files containing just the config symbols that you are interested
-in.  Then the kernel config system generates the full .config file,
-including symbols of your miniconfig file.
-
-This 'KCONFIG_ALLCONFIG' file is a config file which contains
-(usually a subset of all) preset config symbols.  These variable
-settings are still subject to normal dependency checks.
-
-Examples:
-	KCONFIG_ALLCONFIG=custom-notebook.config make allnoconfig
-or
-	KCONFIG_ALLCONFIG=mini.config make allnoconfig
-or
-	make KCONFIG_ALLCONFIG=mini.config allnoconfig
-
-These examples will disable most options (allnoconfig) but enable or
-disable the options that are explicitly listed in the specified
-mini-config files.
-
-______________________________________________________________________
-Environment variables for 'randconfig'
-
-KCONFIG_SEED
---------------------------------------------------
-You can set this to the integer value used to seed the RNG, if you want
-to somehow debug the behaviour of the kconfig parser/frontends.
-If not set, the current time will be used.
-
-KCONFIG_PROBABILITY
---------------------------------------------------
-This variable can be used to skew the probabilities. This variable can
-be unset or empty, or set to three different formats:
-	KCONFIG_PROBABILITY     y:n split           y:m:n split
-	-----------------------------------------------------------------
-	unset or empty          50  : 50            33  : 33  : 34
-	N                        N  : 100-N         N/2 : N/2 : 100-N
-    [1] N:M                     N+M : 100-(N+M)      N  :  M  : 100-(N+M)
-    [2] N:M:L                    N  : 100-N          M  :  L  : 100-(M+L)
-
-where N, M and L are integers (in base 10) in the range [0,100], and so
-that:
-    [1] N+M is in the range [0,100]
-    [2] M+L is in the range [0,100]
-
-Examples:
-	KCONFIG_PROBABILITY=10
-		10% of booleans will be set to 'y', 90% to 'n'
-		5% of tristates will be set to 'y', 5% to 'm', 90% to 'n'
-	KCONFIG_PROBABILITY=15:25
-		40% of booleans will be set to 'y', 60% to 'n'
-		15% of tristates will be set to 'y', 25% to 'm', 60% to 'n'
-	KCONFIG_PROBABILITY=10:15:15
-		10% of booleans will be set to 'y', 90% to 'n'
-		15% of tristates will be set to 'y', 15% to 'm', 70% to 'n'
-
-______________________________________________________________________
-Environment variables for 'syncconfig'
-
-KCONFIG_NOSILENTUPDATE
---------------------------------------------------
-If this variable has a non-blank value, it prevents silent kernel
-config updates (requires explicit updates).
-
-KCONFIG_AUTOCONFIG
---------------------------------------------------
-This environment variable can be set to specify the path & name of the
-"auto.conf" file.  Its default value is "include/config/auto.conf".
-
-KCONFIG_TRISTATE
---------------------------------------------------
-This environment variable can be set to specify the path & name of the
-"tristate.conf" file.  Its default value is "include/config/tristate.conf".
-
-KCONFIG_AUTOHEADER
---------------------------------------------------
-This environment variable can be set to specify the path & name of the
-"autoconf.h" (header) file.
-Its default value is "include/generated/autoconf.h".
-
-
-======================================================================
-menuconfig
---------------------------------------------------
-
-SEARCHING for CONFIG symbols
-
-Searching in menuconfig:
-
-	The Search function searches for kernel configuration symbol
-	names, so you have to know something close to what you are
-	looking for.
-
-	Example:
-		/hotplug
-		This lists all config symbols that contain "hotplug",
-		e.g., HOTPLUG_CPU, MEMORY_HOTPLUG.
-
-	For search help, enter / followed by TAB-TAB (to highlight
-	<Help>) and Enter.  This will tell you that you can also use
-	regular expressions (regexes) in the search string, so if you
-	are not interested in MEMORY_HOTPLUG, you could try
-
-		/^hotplug
-
-	When searching, symbols are sorted thus:
-	  - first, exact matches, sorted alphabetically (an exact match
-	    is when the search matches the complete symbol name);
-	  - then, other matches, sorted alphabetically.
-	For example: ^ATH.K matches:
-	    ATH5K ATH9K ATH5K_AHB ATH5K_DEBUG [...] ATH6KL ATH6KL_DEBUG
-	    [...] ATH9K_AHB ATH9K_BTCOEX_SUPPORT ATH9K_COMMON [...]
-	of which only ATH5K and ATH9K match exactly and so are sorted
-	first (and in alphabetical order), then come all other symbols,
-	sorted in alphabetical order.
-
-______________________________________________________________________
-User interface options for 'menuconfig'
-
-MENUCONFIG_COLOR
---------------------------------------------------
-It is possible to select different color themes using the variable
-MENUCONFIG_COLOR.  To select a theme use:
-
-	make MENUCONFIG_COLOR=<theme> menuconfig
-
-Available themes are:
-  mono       => selects colors suitable for monochrome displays
-  blackbg    => selects a color scheme with black background
-  classic    => theme with blue background. The classic look
-  bluetitle  => a LCD friendly version of classic. (default)
-
-MENUCONFIG_MODE
---------------------------------------------------
-This mode shows all sub-menus in one large tree.
-
-Example:
-	make MENUCONFIG_MODE=single_menu menuconfig
-
-
-======================================================================
-nconfig
---------------------------------------------------
-
-nconfig is an alternate text-based configurator.  It lists function
-keys across the bottom of the terminal (window) that execute commands.
-You can also just use the corresponding numeric key to execute the
-commands unless you are in a data entry window.  E.g., instead of F6
-for Save, you can just press 6.
-
-Use F1 for Global help or F3 for the Short help menu.
-
-Searching in nconfig:
-
-	You can search either in the menu entry "prompt" strings
-	or in the configuration symbols.
-
-	Use / to begin a search through the menu entries.  This does
-	not support regular expressions.  Use <Down> or <Up> for
-	Next hit and Previous hit, respectively.  Use <Esc> to
-	terminate the search mode.
-
-	F8 (SymSearch) searches the configuration symbols for the
-	given string or regular expression (regex).
-
-NCONFIG_MODE
---------------------------------------------------
-This mode shows all sub-menus in one large tree.
-
-Example:
-	make NCONFIG_MODE=single_menu nconfig
-
-
-======================================================================
-xconfig
---------------------------------------------------
-
-Searching in xconfig:
-
-	The Search function searches for kernel configuration symbol
-	names, so you have to know something close to what you are
-	looking for.
-
-	Example:
-		Ctrl-F hotplug
-	or
-		Menu: File, Search, hotplug
-
-	lists all config symbol entries that contain "hotplug" in
-	the symbol name.  In this Search dialog, you may change the
-	config setting for any of the entries that are not grayed out.
-	You can also enter a different search string without having
-	to return to the main menu.
-
-
-======================================================================
-gconfig
---------------------------------------------------
-
-Searching in gconfig:
-
-	There is no search command in gconfig.  However, gconfig does
-	have several different viewing choices, modes, and options.
-
-###
diff --git a/Documentation/kbuild/makefiles.rst b/Documentation/kbuild/makefiles.rst
new file mode 100644
index 000000000000..9274cdcc9bd2
--- /dev/null
+++ b/Documentation/kbuild/makefiles.rst
@@ -0,0 +1,1509 @@
+======================
+Linux Kernel Makefiles
+======================
+
+This document describes the Linux kernel Makefiles.
+
+.. Table of Contents
+
+	=== 1 Overview
+	=== 2 Who does what
+	=== 3 The kbuild files
+	   --- 3.1 Goal definitions
+	   --- 3.2 Built-in object goals - obj-y
+	   --- 3.3 Loadable module goals - obj-m
+	   --- 3.4 Objects which export symbols
+	   --- 3.5 Library file goals - lib-y
+	   --- 3.6 Descending down in directories
+	   --- 3.7 Compilation flags
+	   --- 3.8 Command line dependency
+	   --- 3.9 Dependency tracking
+	   --- 3.10 Special Rules
+	   --- 3.11 $(CC) support functions
+	   --- 3.12 $(LD) support functions
+
+	=== 4 Host Program support
+	   --- 4.1 Simple Host Program
+	   --- 4.2 Composite Host Programs
+	   --- 4.3 Using C++ for host programs
+	   --- 4.4 Controlling compiler options for host programs
+	   --- 4.5 When host programs are actually built
+	   --- 4.6 Using hostprogs-$(CONFIG_FOO)
+
+	=== 5 Kbuild clean infrastructure
+
+	=== 6 Architecture Makefiles
+	   --- 6.1 Set variables to tweak the build to the architecture
+	   --- 6.2 Add prerequisites to archheaders:
+	   --- 6.3 Add prerequisites to archprepare:
+	   --- 6.4 List directories to visit when descending
+	   --- 6.5 Architecture-specific boot images
+	   --- 6.6 Building non-kbuild targets
+	   --- 6.7 Commands useful for building a boot image
+	   --- 6.8 Custom kbuild commands
+	   --- 6.9 Preprocessing linker scripts
+	   --- 6.10 Generic header files
+	   --- 6.11 Post-link pass
+
+	=== 7 Kbuild syntax for exported headers
+		--- 7.1 no-export-headers
+		--- 7.2 generic-y
+		--- 7.3 generated-y
+		--- 7.4 mandatory-y
+
+	=== 8 Kbuild Variables
+	=== 9 Makefile language
+	=== 10 Credits
+	=== 11 TODO
+
+1 Overview
+==========
+
+The Makefiles have five parts::
+
+	Makefile		the top Makefile.
+	.config			the kernel configuration file.
+	arch/$(ARCH)/Makefile	the arch Makefile.
+	scripts/Makefile.*	common rules etc. for all kbuild Makefiles.
+	kbuild Makefiles	there are about 500 of these.
+
+The top Makefile reads the .config file, which comes from the kernel
+configuration process.
+
+The top Makefile is responsible for building two major products: vmlinux
+(the resident kernel image) and modules (any module files).
+It builds these goals by recursively descending into the subdirectories of
+the kernel source tree.
+The list of subdirectories which are visited depends upon the kernel
+configuration. The top Makefile textually includes an arch Makefile
+with the name arch/$(ARCH)/Makefile. The arch Makefile supplies
+architecture-specific information to the top Makefile.
+
+Each subdirectory has a kbuild Makefile which carries out the commands
+passed down from above. The kbuild Makefile uses information from the
+.config file to construct various file lists used by kbuild to build
+any built-in or modular targets.
+
+scripts/Makefile.* contains all the definitions/rules etc. that
+are used to build the kernel based on the kbuild makefiles.
+
+
+2 Who does what
+===============
+
+People have four different relationships with the kernel Makefiles.
+
+*Users* are people who build kernels.  These people type commands such as
+"make menuconfig" or "make".  They usually do not read or edit
+any kernel Makefiles (or any other source files).
+
+*Normal developers* are people who work on features such as device
+drivers, file systems, and network protocols.  These people need to
+maintain the kbuild Makefiles for the subsystem they are
+working on.  In order to do this effectively, they need some overall
+knowledge about the kernel Makefiles, plus detailed knowledge about the
+public interface for kbuild.
+
+*Arch developers* are people who work on an entire architecture, such
+as sparc or ia64.  Arch developers need to know about the arch Makefile
+as well as kbuild Makefiles.
+
+*Kbuild developers* are people who work on the kernel build system itself.
+These people need to know about all aspects of the kernel Makefiles.
+
+This document is aimed towards normal developers and arch developers.
+
+
+3 The kbuild files
+==================
+
+Most Makefiles within the kernel are kbuild Makefiles that use the
+kbuild infrastructure. This chapter introduces the syntax used in the
+kbuild makefiles.
+The preferred name for the kbuild files are 'Makefile' but 'Kbuild' can
+be used and if both a 'Makefile' and a 'Kbuild' file exists, then the 'Kbuild'
+file will be used.
+
+Section 3.1 "Goal definitions" is a quick intro, further chapters provide
+more details, with real examples.
+
+3.1 Goal definitions
+--------------------
+
+	Goal definitions are the main part (heart) of the kbuild Makefile.
+	These lines define the files to be built, any special compilation
+	options, and any subdirectories to be entered recursively.
+
+	The most simple kbuild makefile contains one line:
+
+	Example::
+
+		obj-y += foo.o
+
+	This tells kbuild that there is one object in that directory, named
+	foo.o. foo.o will be built from foo.c or foo.S.
+
+	If foo.o shall be built as a module, the variable obj-m is used.
+	Therefore the following pattern is often used:
+
+	Example::
+
+		obj-$(CONFIG_FOO) += foo.o
+
+	$(CONFIG_FOO) evaluates to either y (for built-in) or m (for module).
+	If CONFIG_FOO is neither y nor m, then the file will not be compiled
+	nor linked.
+
+3.2 Built-in object goals - obj-y
+---------------------------------
+
+	The kbuild Makefile specifies object files for vmlinux
+	in the $(obj-y) lists.  These lists depend on the kernel
+	configuration.
+
+	Kbuild compiles all the $(obj-y) files.  It then calls
+	"$(AR) rcSTP" to merge these files into one built-in.a file.
+	This is a thin archive without a symbol table. It will be later
+	linked into vmlinux by scripts/link-vmlinux.sh
+
+	The order of files in $(obj-y) is significant.  Duplicates in
+	the lists are allowed: the first instance will be linked into
+	built-in.a and succeeding instances will be ignored.
+
+	Link order is significant, because certain functions
+	(module_init() / __initcall) will be called during boot in the
+	order they appear. So keep in mind that changing the link
+	order may e.g. change the order in which your SCSI
+	controllers are detected, and thus your disks are renumbered.
+
+	Example::
+
+		#drivers/isdn/i4l/Makefile
+		# Makefile for the kernel ISDN subsystem and device drivers.
+		# Each configuration option enables a list of files.
+		obj-$(CONFIG_ISDN_I4L)         += isdn.o
+		obj-$(CONFIG_ISDN_PPP_BSDCOMP) += isdn_bsdcomp.o
+
+3.3 Loadable module goals - obj-m
+---------------------------------
+
+	$(obj-m) specifies object files which are built as loadable
+	kernel modules.
+
+	A module may be built from one source file or several source
+	files. In the case of one source file, the kbuild makefile
+	simply adds the file to $(obj-m).
+
+	Example::
+
+		#drivers/isdn/i4l/Makefile
+		obj-$(CONFIG_ISDN_PPP_BSDCOMP) += isdn_bsdcomp.o
+
+	Note: In this example $(CONFIG_ISDN_PPP_BSDCOMP) evaluates to 'm'
+
+	If a kernel module is built from several source files, you specify
+	that you want to build a module in the same way as above; however,
+	kbuild needs to know which object files you want to build your
+	module from, so you have to tell it by setting a $(<module_name>-y)
+	variable.
+
+	Example::
+
+		#drivers/isdn/i4l/Makefile
+		obj-$(CONFIG_ISDN_I4L) += isdn.o
+		isdn-y := isdn_net_lib.o isdn_v110.o isdn_common.o
+
+	In this example, the module name will be isdn.o. Kbuild will
+	compile the objects listed in $(isdn-y) and then run
+	"$(LD) -r" on the list of these files to generate isdn.o.
+
+	Due to kbuild recognizing $(<module_name>-y) for composite objects,
+	you can use the value of a `CONFIG_` symbol to optionally include an
+	object file as part of a composite object.
+
+	Example::
+
+		#fs/ext2/Makefile
+	        obj-$(CONFIG_EXT2_FS) += ext2.o
+		ext2-y := balloc.o dir.o file.o ialloc.o inode.o ioctl.o \
+			  namei.o super.o symlink.o
+	        ext2-$(CONFIG_EXT2_FS_XATTR) += xattr.o xattr_user.o \
+						xattr_trusted.o
+
+	In this example, xattr.o, xattr_user.o and xattr_trusted.o are only
+	part of the composite object ext2.o if $(CONFIG_EXT2_FS_XATTR)
+	evaluates to 'y'.
+
+	Note: Of course, when you are building objects into the kernel,
+	the syntax above will also work. So, if you have CONFIG_EXT2_FS=y,
+	kbuild will build an ext2.o file for you out of the individual
+	parts and then link this into built-in.a, as you would expect.
+
+3.4 Objects which export symbols
+--------------------------------
+
+	No special notation is required in the makefiles for
+	modules exporting symbols.
+
+3.5 Library file goals - lib-y
+------------------------------
+
+	Objects listed with obj-* are used for modules, or
+	combined in a built-in.a for that specific directory.
+	There is also the possibility to list objects that will
+	be included in a library, lib.a.
+	All objects listed with lib-y are combined in a single
+	library for that directory.
+	Objects that are listed in obj-y and additionally listed in
+	lib-y will not be included in the library, since they will
+	be accessible anyway.
+	For consistency, objects listed in lib-m will be included in lib.a.
+
+	Note that the same kbuild makefile may list files to be built-in
+	and to be part of a library. Therefore the same directory
+	may contain both a built-in.a and a lib.a file.
+
+	Example::
+
+		#arch/x86/lib/Makefile
+		lib-y    := delay.o
+
+	This will create a library lib.a based on delay.o. For kbuild to
+	actually recognize that there is a lib.a being built, the directory
+	shall be listed in libs-y.
+
+	See also "6.4 List directories to visit when descending".
+
+	Use of lib-y is normally restricted to `lib/` and `arch/*/lib`.
+
+3.6 Descending down in directories
+----------------------------------
+
+	A Makefile is only responsible for building objects in its own
+	directory. Files in subdirectories should be taken care of by
+	Makefiles in these subdirs. The build system will automatically
+	invoke make recursively in subdirectories, provided you let it know of
+	them.
+
+	To do so, obj-y and obj-m are used.
+	ext2 lives in a separate directory, and the Makefile present in fs/
+	tells kbuild to descend down using the following assignment.
+
+	Example::
+
+		#fs/Makefile
+		obj-$(CONFIG_EXT2_FS) += ext2/
+
+	If CONFIG_EXT2_FS is set to either 'y' (built-in) or 'm' (modular)
+	the corresponding obj- variable will be set, and kbuild will descend
+	down in the ext2 directory.
+	Kbuild only uses this information to decide that it needs to visit
+	the directory, it is the Makefile in the subdirectory that
+	specifies what is modular and what is built-in.
+
+	It is good practice to use a `CONFIG_` variable when assigning directory
+	names. This allows kbuild to totally skip the directory if the
+	corresponding `CONFIG_` option is neither 'y' nor 'm'.
+
+3.7 Compilation flags
+---------------------
+
+    ccflags-y, asflags-y and ldflags-y
+	These three flags apply only to the kbuild makefile in which they
+	are assigned. They are used for all the normal cc, as and ld
+	invocations happening during a recursive build.
+	Note: Flags with the same behaviour were previously named:
+	EXTRA_CFLAGS, EXTRA_AFLAGS and EXTRA_LDFLAGS.
+	They are still supported but their usage is deprecated.
+
+	ccflags-y specifies options for compiling with $(CC).
+
+	Example::
+
+		# drivers/acpi/acpica/Makefile
+		ccflags-y			:= -Os -D_LINUX -DBUILDING_ACPICA
+		ccflags-$(CONFIG_ACPI_DEBUG)	+= -DACPI_DEBUG_OUTPUT
+
+	This variable is necessary because the top Makefile owns the
+	variable $(KBUILD_CFLAGS) and uses it for compilation flags for the
+	entire tree.
+
+	asflags-y specifies options for assembling with $(AS).
+
+	Example::
+
+		#arch/sparc/kernel/Makefile
+		asflags-y := -ansi
+
+	ldflags-y specifies options for linking with $(LD).
+
+	Example::
+
+		#arch/cris/boot/compressed/Makefile
+		ldflags-y += -T $(srctree)/$(src)/decompress_$(arch-y).lds
+
+    subdir-ccflags-y, subdir-asflags-y
+	The two flags listed above are similar to ccflags-y and asflags-y.
+	The difference is that the subdir- variants have effect for the kbuild
+	file where they are present and all subdirectories.
+	Options specified using subdir-* are added to the commandline before
+	the options specified using the non-subdir variants.
+
+	Example::
+
+		subdir-ccflags-y := -Werror
+
+    CFLAGS_$@, AFLAGS_$@
+	CFLAGS_$@ and AFLAGS_$@ only apply to commands in current
+	kbuild makefile.
+
+	$(CFLAGS_$@) specifies per-file options for $(CC).  The $@
+	part has a literal value which specifies the file that it is for.
+
+	Example::
+
+		# drivers/scsi/Makefile
+		CFLAGS_aha152x.o =   -DAHA152X_STAT -DAUTOCONF
+		CFLAGS_gdth.o    = # -DDEBUG_GDTH=2 -D__SERIAL__ -D__COM2__ \
+				     -DGDTH_STATISTICS
+
+	These two lines specify compilation flags for aha152x.o and gdth.o.
+
+	$(AFLAGS_$@) is a similar feature for source files in assembly
+	languages.
+
+	Example::
+
+		# arch/arm/kernel/Makefile
+		AFLAGS_head.o        := -DTEXT_OFFSET=$(TEXT_OFFSET)
+		AFLAGS_crunch-bits.o := -Wa,-mcpu=ep9312
+		AFLAGS_iwmmxt.o      := -Wa,-mcpu=iwmmxt
+
+
+3.9 Dependency tracking
+-----------------------
+
+	Kbuild tracks dependencies on the following:
+	1) All prerequisite files (both `*.c` and `*.h`)
+	2) `CONFIG_` options used in all prerequisite files
+	3) Command-line used to compile target
+
+	Thus, if you change an option to $(CC) all affected files will
+	be re-compiled.
+
+3.10 Special Rules
+------------------
+
+	Special rules are used when the kbuild infrastructure does
+	not provide the required support. A typical example is
+	header files generated during the build process.
+	Another example are the architecture-specific Makefiles which
+	need special rules to prepare boot images etc.
+
+	Special rules are written as normal Make rules.
+	Kbuild is not executing in the directory where the Makefile is
+	located, so all special rules shall provide a relative
+	path to prerequisite files and target files.
+
+	Two variables are used when defining special rules:
+
+	$(src)
+	    $(src) is a relative path which points to the directory
+	    where the Makefile is located. Always use $(src) when
+	    referring to files located in the src tree.
+
+	$(obj)
+	    $(obj) is a relative path which points to the directory
+	    where the target is saved. Always use $(obj) when
+	    referring to generated files.
+
+	    Example::
+
+		#drivers/scsi/Makefile
+		$(obj)/53c8xx_d.h: $(src)/53c7,8xx.scr $(src)/script_asm.pl
+			$(CPP) -DCHIP=810 - < $< | ... $(src)/script_asm.pl
+
+	    This is a special rule, following the normal syntax
+	    required by make.
+
+	    The target file depends on two prerequisite files. References
+	    to the target file are prefixed with $(obj), references
+	    to prerequisites are referenced with $(src) (because they are not
+	    generated files).
+
+	$(kecho)
+	    echoing information to user in a rule is often a good practice
+	    but when execution "make -s" one does not expect to see any output
+	    except for warnings/errors.
+	    To support this kbuild defines $(kecho) which will echo out the
+	    text following $(kecho) to stdout except if "make -s" is used.
+
+	Example::
+
+		#arch/blackfin/boot/Makefile
+		$(obj)/vmImage: $(obj)/vmlinux.gz
+			$(call if_changed,uimage)
+			@$(kecho) 'Kernel: $@ is ready'
+
+
+3.11 $(CC) support functions
+----------------------------
+
+	The kernel may be built with several different versions of
+	$(CC), each supporting a unique set of features and options.
+	kbuild provides basic support to check for valid options for $(CC).
+	$(CC) is usually the gcc compiler, but other alternatives are
+	available.
+
+    as-option
+	as-option is used to check if $(CC) -- when used to compile
+	assembler (`*.S`) files -- supports the given option. An optional
+	second option may be specified if the first option is not supported.
+
+	Example::
+
+		#arch/sh/Makefile
+		cflags-y += $(call as-option,-Wa$(comma)-isa=$(isa-y),)
+
+	In the above example, cflags-y will be assigned the option
+	-Wa$(comma)-isa=$(isa-y) if it is supported by $(CC).
+	The second argument is optional, and if supplied will be used
+	if first argument is not supported.
+
+    cc-ldoption
+	cc-ldoption is used to check if $(CC) when used to link object files
+	supports the given option.  An optional second option may be
+	specified if first option are not supported.
+
+	Example::
+
+		#arch/x86/kernel/Makefile
+		vsyscall-flags += $(call cc-ldoption, -Wl$(comma)--hash-style=sysv)
+
+	In the above example, vsyscall-flags will be assigned the option
+	-Wl$(comma)--hash-style=sysv if it is supported by $(CC).
+	The second argument is optional, and if supplied will be used
+	if first argument is not supported.
+
+    as-instr
+	as-instr checks if the assembler reports a specific instruction
+	and then outputs either option1 or option2
+	C escapes are supported in the test instruction
+	Note: as-instr-option uses KBUILD_AFLAGS for $(AS) options
+
+    cc-option
+	cc-option is used to check if $(CC) supports a given option, and if
+	not supported to use an optional second option.
+
+	Example::
+
+		#arch/x86/Makefile
+		cflags-y += $(call cc-option,-march=pentium-mmx,-march=i586)
+
+	In the above example, cflags-y will be assigned the option
+	-march=pentium-mmx if supported by $(CC), otherwise -march=i586.
+	The second argument to cc-option is optional, and if omitted,
+	cflags-y will be assigned no value if first option is not supported.
+	Note: cc-option uses KBUILD_CFLAGS for $(CC) options
+
+   cc-option-yn
+	cc-option-yn is used to check if gcc supports a given option
+	and return 'y' if supported, otherwise 'n'.
+
+	Example::
+
+		#arch/ppc/Makefile
+		biarch := $(call cc-option-yn, -m32)
+		aflags-$(biarch) += -a32
+		cflags-$(biarch) += -m32
+
+	In the above example, $(biarch) is set to y if $(CC) supports the -m32
+	option. When $(biarch) equals 'y', the expanded variables $(aflags-y)
+	and $(cflags-y) will be assigned the values -a32 and -m32,
+	respectively.
+	Note: cc-option-yn uses KBUILD_CFLAGS for $(CC) options
+
+    cc-disable-warning
+	cc-disable-warning checks if gcc supports a given warning and returns
+	the commandline switch to disable it. This special function is needed,
+	because gcc 4.4 and later accept any unknown -Wno-* option and only
+	warn about it if there is another warning in the source file.
+
+	Example::
+
+		KBUILD_CFLAGS += $(call cc-disable-warning, unused-but-set-variable)
+
+	In the above example, -Wno-unused-but-set-variable will be added to
+	KBUILD_CFLAGS only if gcc really accepts it.
+
+    cc-ifversion
+	cc-ifversion tests the version of $(CC) and equals the fourth parameter
+	if version expression is true, or the fifth (if given) if the version
+	expression is false.
+
+	Example::
+
+		#fs/reiserfs/Makefile
+		ccflags-y := $(call cc-ifversion, -lt, 0402, -O1)
+
+	In this example, ccflags-y will be assigned the value -O1 if the
+	$(CC) version is less than 4.2.
+	cc-ifversion takes all the shell operators:
+	-eq, -ne, -lt, -le, -gt, and -ge
+	The third parameter may be a text as in this example, but it may also
+	be an expanded variable or a macro.
+
+    cc-cross-prefix
+	cc-cross-prefix is used to check if there exists a $(CC) in path with
+	one of the listed prefixes. The first prefix where there exist a
+	prefix$(CC) in the PATH is returned - and if no prefix$(CC) is found
+	then nothing is returned.
+	Additional prefixes are separated by a single space in the
+	call of cc-cross-prefix.
+	This functionality is useful for architecture Makefiles that try
+	to set CROSS_COMPILE to well-known values but may have several
+	values to select between.
+	It is recommended only to try to set CROSS_COMPILE if it is a cross
+	build (host arch is different from target arch). And if CROSS_COMPILE
+	is already set then leave it with the old value.
+
+	Example::
+
+		#arch/m68k/Makefile
+		ifneq ($(SUBARCH),$(ARCH))
+		        ifeq ($(CROSS_COMPILE),)
+		               CROSS_COMPILE := $(call cc-cross-prefix, m68k-linux-gnu-)
+			endif
+		endif
+
+3.12 $(LD) support functions
+----------------------------
+
+    ld-option
+	ld-option is used to check if $(LD) supports the supplied option.
+	ld-option takes two options as arguments.
+	The second argument is an optional option that can be used if the
+	first option is not supported by $(LD).
+
+	Example::
+
+		#Makefile
+		LDFLAGS_vmlinux += $(call ld-option, -X)
+
+
+4 Host Program support
+======================
+
+Kbuild supports building executables on the host for use during the
+compilation stage.
+Two steps are required in order to use a host executable.
+
+The first step is to tell kbuild that a host program exists. This is
+done utilising the variable hostprogs-y.
+
+The second step is to add an explicit dependency to the executable.
+This can be done in two ways. Either add the dependency in a rule,
+or utilise the variable $(always).
+Both possibilities are described in the following.
+
+4.1 Simple Host Program
+-----------------------
+
+	In some cases there is a need to compile and run a program on the
+	computer where the build is running.
+	The following line tells kbuild that the program bin2hex shall be
+	built on the build host.
+
+	Example::
+
+		hostprogs-y := bin2hex
+
+	Kbuild assumes in the above example that bin2hex is made from a single
+	c-source file named bin2hex.c located in the same directory as
+	the Makefile.
+
+4.2 Composite Host Programs
+---------------------------
+
+	Host programs can be made up based on composite objects.
+	The syntax used to define composite objects for host programs is
+	similar to the syntax used for kernel objects.
+	$(<executable>-objs) lists all objects used to link the final
+	executable.
+
+	Example::
+
+		#scripts/lxdialog/Makefile
+		hostprogs-y   := lxdialog
+		lxdialog-objs := checklist.o lxdialog.o
+
+	Objects with extension .o are compiled from the corresponding .c
+	files. In the above example, checklist.c is compiled to checklist.o
+	and lxdialog.c is compiled to lxdialog.o.
+
+	Finally, the two .o files are linked to the executable, lxdialog.
+	Note: The syntax <executable>-y is not permitted for host-programs.
+
+4.3 Using C++ for host programs
+-------------------------------
+
+	kbuild offers support for host programs written in C++. This was
+	introduced solely to support kconfig, and is not recommended
+	for general use.
+
+	Example::
+
+		#scripts/kconfig/Makefile
+		hostprogs-y   := qconf
+		qconf-cxxobjs := qconf.o
+
+	In the example above the executable is composed of the C++ file
+	qconf.cc - identified by $(qconf-cxxobjs).
+
+	If qconf is composed of a mixture of .c and .cc files, then an
+	additional line can be used to identify this.
+
+	Example::
+
+		#scripts/kconfig/Makefile
+		hostprogs-y   := qconf
+		qconf-cxxobjs := qconf.o
+		qconf-objs    := check.o
+
+4.4 Controlling compiler options for host programs
+--------------------------------------------------
+
+	When compiling host programs, it is possible to set specific flags.
+	The programs will always be compiled utilising $(HOSTCC) passed
+	the options specified in $(KBUILD_HOSTCFLAGS).
+	To set flags that will take effect for all host programs created
+	in that Makefile, use the variable HOST_EXTRACFLAGS.
+
+	Example::
+
+		#scripts/lxdialog/Makefile
+		HOST_EXTRACFLAGS += -I/usr/include/ncurses
+
+	To set specific flags for a single file the following construction
+	is used:
+
+	Example::
+
+		#arch/ppc64/boot/Makefile
+		HOSTCFLAGS_piggyback.o := -DKERNELBASE=$(KERNELBASE)
+
+	It is also possible to specify additional options to the linker.
+
+	Example::
+
+		#scripts/kconfig/Makefile
+		HOSTLDLIBS_qconf := -L$(QTDIR)/lib
+
+	When linking qconf, it will be passed the extra option
+	"-L$(QTDIR)/lib".
+
+4.5 When host programs are actually built
+-----------------------------------------
+
+	Kbuild will only build host-programs when they are referenced
+	as a prerequisite.
+	This is possible in two ways:
+
+	(1) List the prerequisite explicitly in a special rule.
+
+	Example::
+
+		#drivers/pci/Makefile
+		hostprogs-y := gen-devlist
+		$(obj)/devlist.h: $(src)/pci.ids $(obj)/gen-devlist
+			( cd $(obj); ./gen-devlist ) < $<
+
+	The target $(obj)/devlist.h will not be built before
+	$(obj)/gen-devlist is updated. Note that references to
+	the host programs in special rules must be prefixed with $(obj).
+
+	(2) Use $(always)
+
+	When there is no suitable special rule, and the host program
+	shall be built when a makefile is entered, the $(always)
+	variable shall be used.
+
+	Example::
+
+		#scripts/lxdialog/Makefile
+		hostprogs-y   := lxdialog
+		always        := $(hostprogs-y)
+
+	This will tell kbuild to build lxdialog even if not referenced in
+	any rule.
+
+4.6 Using hostprogs-$(CONFIG_FOO)
+---------------------------------
+
+	A typical pattern in a Kbuild file looks like this:
+
+	Example::
+
+		#scripts/Makefile
+		hostprogs-$(CONFIG_KALLSYMS) += kallsyms
+
+	Kbuild knows about both 'y' for built-in and 'm' for module.
+	So if a config symbol evaluates to 'm', kbuild will still build
+	the binary. In other words, Kbuild handles hostprogs-m exactly
+	like hostprogs-y. But only hostprogs-y is recommended to be used
+	when no CONFIG symbols are involved.
+
+5 Kbuild clean infrastructure
+=============================
+
+"make clean" deletes most generated files in the obj tree where the kernel
+is compiled. This includes generated files such as host programs.
+Kbuild knows targets listed in $(hostprogs-y), $(hostprogs-m), $(always),
+$(extra-y) and $(targets). They are all deleted during "make clean".
+Files matching the patterns "*.[oas]", "*.ko", plus some additional files
+generated by kbuild are deleted all over the kernel src tree when
+"make clean" is executed.
+
+Additional files can be specified in kbuild makefiles by use of $(clean-files).
+
+	Example::
+
+		#lib/Makefile
+		clean-files := crc32table.h
+
+When executing "make clean", the file "crc32table.h" will be deleted.
+Kbuild will assume files to be in the same relative directory as the
+Makefile, except if prefixed with $(objtree).
+
+To delete a directory hierarchy use:
+
+	Example::
+
+		#scripts/package/Makefile
+		clean-dirs := $(objtree)/debian/
+
+This will delete the directory debian in the toplevel directory, including all
+subdirectories.
+
+To exclude certain files from make clean, use the $(no-clean-files) variable.
+This is only a special case used in the top level Kbuild file:
+
+	Example::
+
+		#Kbuild
+		no-clean-files := $(bounds-file) $(offsets-file)
+
+Usually kbuild descends down in subdirectories due to "obj-* := dir/",
+but in the architecture makefiles where the kbuild infrastructure
+is not sufficient this sometimes needs to be explicit.
+
+	Example::
+
+		#arch/x86/boot/Makefile
+		subdir- := compressed/
+
+The above assignment instructs kbuild to descend down in the
+directory compressed/ when "make clean" is executed.
+
+To support the clean infrastructure in the Makefiles that build the
+final bootimage there is an optional target named archclean:
+
+	Example::
+
+		#arch/x86/Makefile
+		archclean:
+			$(Q)$(MAKE) $(clean)=arch/x86/boot
+
+When "make clean" is executed, make will descend down in arch/x86/boot,
+and clean as usual. The Makefile located in arch/x86/boot/ may use
+the subdir- trick to descend further down.
+
+Note 1: arch/$(ARCH)/Makefile cannot use "subdir-", because that file is
+included in the top level makefile, and the kbuild infrastructure
+is not operational at that point.
+
+Note 2: All directories listed in core-y, libs-y, drivers-y and net-y will
+be visited during "make clean".
+
+6 Architecture Makefiles
+========================
+
+The top level Makefile sets up the environment and does the preparation,
+before starting to descend down in the individual directories.
+The top level makefile contains the generic part, whereas
+arch/$(ARCH)/Makefile contains what is required to set up kbuild
+for said architecture.
+To do so, arch/$(ARCH)/Makefile sets up a number of variables and defines
+a few targets.
+
+When kbuild executes, the following steps are followed (roughly):
+
+1) Configuration of the kernel => produce .config
+2) Store kernel version in include/linux/version.h
+3) Updating all other prerequisites to the target prepare:
+   - Additional prerequisites are specified in arch/$(ARCH)/Makefile
+4) Recursively descend down in all directories listed in
+   init-* core* drivers-* net-* libs-* and build all targets.
+   - The values of the above variables are expanded in arch/$(ARCH)/Makefile.
+5) All object files are then linked and the resulting file vmlinux is
+   located at the root of the obj tree.
+   The very first objects linked are listed in head-y, assigned by
+   arch/$(ARCH)/Makefile.
+6) Finally, the architecture-specific part does any required post processing
+   and builds the final bootimage.
+   - This includes building boot records
+   - Preparing initrd images and the like
+
+
+6.1 Set variables to tweak the build to the architecture
+--------------------------------------------------------
+
+    LDFLAGS
+	Generic $(LD) options
+
+	Flags used for all invocations of the linker.
+	Often specifying the emulation is sufficient.
+
+	Example::
+
+		#arch/s390/Makefile
+		LDFLAGS         := -m elf_s390
+
+	Note: ldflags-y can be used to further customise
+	the flags used. See chapter 3.7.
+
+    LDFLAGS_vmlinux
+	Options for $(LD) when linking vmlinux
+
+	LDFLAGS_vmlinux is used to specify additional flags to pass to
+	the linker when linking the final vmlinux image.
+	LDFLAGS_vmlinux uses the LDFLAGS_$@ support.
+
+	Example::
+
+		#arch/x86/Makefile
+		LDFLAGS_vmlinux := -e stext
+
+    OBJCOPYFLAGS
+	objcopy flags
+
+	When $(call if_changed,objcopy) is used to translate a .o file,
+	the flags specified in OBJCOPYFLAGS will be used.
+	$(call if_changed,objcopy) is often used to generate raw binaries on
+	vmlinux.
+
+	Example::
+
+		#arch/s390/Makefile
+		OBJCOPYFLAGS := -O binary
+
+		#arch/s390/boot/Makefile
+		$(obj)/image: vmlinux FORCE
+			$(call if_changed,objcopy)
+
+	In this example, the binary $(obj)/image is a binary version of
+	vmlinux. The usage of $(call if_changed,xxx) will be described later.
+
+    KBUILD_AFLAGS
+	$(AS) assembler flags
+
+	Default value - see top level Makefile
+	Append or modify as required per architecture.
+
+	Example::
+
+		#arch/sparc64/Makefile
+		KBUILD_AFLAGS += -m64 -mcpu=ultrasparc
+
+    KBUILD_CFLAGS
+	$(CC) compiler flags
+
+	Default value - see top level Makefile
+	Append or modify as required per architecture.
+
+	Often, the KBUILD_CFLAGS variable depends on the configuration.
+
+	Example::
+
+		#arch/x86/boot/compressed/Makefile
+		cflags-$(CONFIG_X86_32) := -march=i386
+		cflags-$(CONFIG_X86_64) := -mcmodel=small
+		KBUILD_CFLAGS += $(cflags-y)
+
+	Many arch Makefiles dynamically run the target C compiler to
+	probe supported options::
+
+		#arch/x86/Makefile
+
+		...
+		cflags-$(CONFIG_MPENTIUMII)     += $(call cc-option,\
+						-march=pentium2,-march=i686)
+		...
+		# Disable unit-at-a-time mode ...
+		KBUILD_CFLAGS += $(call cc-option,-fno-unit-at-a-time)
+		...
+
+
+	The first example utilises the trick that a config option expands
+	to 'y' when selected.
+
+    KBUILD_AFLAGS_KERNEL
+	$(AS) options specific for built-in
+
+	$(KBUILD_AFLAGS_KERNEL) contains extra C compiler flags used to compile
+	resident kernel code.
+
+    KBUILD_AFLAGS_MODULE
+	Options for $(AS) when building modules
+
+	$(KBUILD_AFLAGS_MODULE) is used to add arch-specific options that
+	are used for $(AS).
+
+	From commandline AFLAGS_MODULE shall be used (see kbuild.txt).
+
+    KBUILD_CFLAGS_KERNEL
+	$(CC) options specific for built-in
+
+	$(KBUILD_CFLAGS_KERNEL) contains extra C compiler flags used to compile
+	resident kernel code.
+
+    KBUILD_CFLAGS_MODULE
+	Options for $(CC) when building modules
+
+	$(KBUILD_CFLAGS_MODULE) is used to add arch-specific options that
+	are used for $(CC).
+	From commandline CFLAGS_MODULE shall be used (see kbuild.txt).
+
+    KBUILD_LDFLAGS_MODULE
+	Options for $(LD) when linking modules
+
+	$(KBUILD_LDFLAGS_MODULE) is used to add arch-specific options
+	used when linking modules. This is often a linker script.
+
+	From commandline LDFLAGS_MODULE shall be used (see kbuild.txt).
+
+    KBUILD_ARFLAGS   Options for $(AR) when creating archives
+
+	$(KBUILD_ARFLAGS) set by the top level Makefile to "D" (deterministic
+	mode) if this option is supported by $(AR).
+
+    ARCH_CPPFLAGS, ARCH_AFLAGS, ARCH_CFLAGS   Overrides the kbuild defaults
+
+	These variables are appended to the KBUILD_CPPFLAGS,
+	KBUILD_AFLAGS, and KBUILD_CFLAGS, respectively, after the
+	top-level Makefile has set any other flags. This provides a
+	means for an architecture to override the defaults.
+
+
+6.2 Add prerequisites to archheaders
+------------------------------------
+
+	The archheaders: rule is used to generate header files that
+	may be installed into user space by "make header_install" or
+	"make headers_install_all".  In order to support
+	"make headers_install_all", this target has to be able to run
+	on an unconfigured tree, or a tree configured for another
+	architecture.
+
+	It is run before "make archprepare" when run on the
+	architecture itself.
+
+
+6.3 Add prerequisites to archprepare
+------------------------------------
+
+	The archprepare: rule is used to list prerequisites that need to be
+	built before starting to descend down in the subdirectories.
+	This is usually used for header files containing assembler constants.
+
+	Example::
+
+		#arch/arm/Makefile
+		archprepare: maketools
+
+	In this example, the file target maketools will be processed
+	before descending down in the subdirectories.
+	See also chapter XXX-TODO that describe how kbuild supports
+	generating offset header files.
+
+
+6.4 List directories to visit when descending
+---------------------------------------------
+
+	An arch Makefile cooperates with the top Makefile to define variables
+	which specify how to build the vmlinux file.  Note that there is no
+	corresponding arch-specific section for modules; the module-building
+	machinery is all architecture-independent.
+
+
+	head-y, init-y, core-y, libs-y, drivers-y, net-y
+	    $(head-y) lists objects to be linked first in vmlinux.
+
+	    $(libs-y) lists directories where a lib.a archive can be located.
+
+	    The rest list directories where a built-in.a object file can be
+	    located.
+
+	    $(init-y) objects will be located after $(head-y).
+
+	    Then the rest follows in this order:
+
+		$(core-y), $(libs-y), $(drivers-y) and $(net-y).
+
+	    The top level Makefile defines values for all generic directories,
+	    and arch/$(ARCH)/Makefile only adds architecture-specific
+	    directories.
+
+	    Example::
+
+		#arch/sparc64/Makefile
+		core-y += arch/sparc64/kernel/
+		libs-y += arch/sparc64/prom/ arch/sparc64/lib/
+		drivers-$(CONFIG_OPROFILE)  += arch/sparc64/oprofile/
+
+
+6.5 Architecture-specific boot images
+-------------------------------------
+
+	An arch Makefile specifies goals that take the vmlinux file, compress
+	it, wrap it in bootstrapping code, and copy the resulting files
+	somewhere. This includes various kinds of installation commands.
+	The actual goals are not standardized across architectures.
+
+	It is common to locate any additional processing in a boot/
+	directory below arch/$(ARCH)/.
+
+	Kbuild does not provide any smart way to support building a
+	target specified in boot/. Therefore arch/$(ARCH)/Makefile shall
+	call make manually to build a target in boot/.
+
+	The recommended approach is to include shortcuts in
+	arch/$(ARCH)/Makefile, and use the full path when calling down
+	into the arch/$(ARCH)/boot/Makefile.
+
+	Example::
+
+		#arch/x86/Makefile
+		boot := arch/x86/boot
+		bzImage: vmlinux
+			$(Q)$(MAKE) $(build)=$(boot) $(boot)/$@
+
+	"$(Q)$(MAKE) $(build)=<dir>" is the recommended way to invoke
+	make in a subdirectory.
+
+	There are no rules for naming architecture-specific targets,
+	but executing "make help" will list all relevant targets.
+	To support this, $(archhelp) must be defined.
+
+	Example::
+
+		#arch/x86/Makefile
+		define archhelp
+		  echo  '* bzImage      - Image (arch/$(ARCH)/boot/bzImage)'
+		endif
+
+	When make is executed without arguments, the first goal encountered
+	will be built. In the top level Makefile the first goal present
+	is all:.
+	An architecture shall always, per default, build a bootable image.
+	In "make help", the default goal is highlighted with a '*'.
+	Add a new prerequisite to all: to select a default goal different
+	from vmlinux.
+
+	Example::
+
+		#arch/x86/Makefile
+		all: bzImage
+
+	When "make" is executed without arguments, bzImage will be built.
+
+6.6 Building non-kbuild targets
+-------------------------------
+
+    extra-y
+	extra-y specifies additional targets created in the current
+	directory, in addition to any targets specified by `obj-*`.
+
+	Listing all targets in extra-y is required for two purposes:
+
+	1) Enable kbuild to check changes in command lines
+
+	   - When $(call if_changed,xxx) is used
+
+	2) kbuild knows what files to delete during "make clean"
+
+	Example::
+
+		#arch/x86/kernel/Makefile
+		extra-y := head.o init_task.o
+
+	In this example, extra-y is used to list object files that
+	shall be built, but shall not be linked as part of built-in.a.
+
+
+6.7 Commands useful for building a boot image
+---------------------------------------------
+
+    Kbuild provides a few macros that are useful when building a
+    boot image.
+
+    if_changed
+	if_changed is the infrastructure used for the following commands.
+
+	Usage::
+
+		target: source(s) FORCE
+			$(call if_changed,ld/objcopy/gzip/...)
+
+	When the rule is evaluated, it is checked to see if any files
+	need an update, or the command line has changed since the last
+	invocation. The latter will force a rebuild if any options
+	to the executable have changed.
+	Any target that utilises if_changed must be listed in $(targets),
+	otherwise the command line check will fail, and the target will
+	always be built.
+	Assignments to $(targets) are without $(obj)/ prefix.
+	if_changed may be used in conjunction with custom commands as
+	defined in 6.8 "Custom kbuild commands".
+
+	Note: It is a typical mistake to forget the FORCE prerequisite.
+	Another common pitfall is that whitespace is sometimes
+	significant; for instance, the below will fail (note the extra space
+	after the comma)::
+
+		target: source(s) FORCE
+
+	**WRONG!**	$(call if_changed, ld/objcopy/gzip/...)
+
+        Note:
+	      if_changed should not be used more than once per target.
+              It stores the executed command in a corresponding .cmd
+
+        file and multiple calls would result in overwrites and
+        unwanted results when the target is up to date and only the
+        tests on changed commands trigger execution of commands.
+
+    ld
+	Link target. Often, LDFLAGS_$@ is used to set specific options to ld.
+
+	Example::
+
+		#arch/x86/boot/Makefile
+		LDFLAGS_bootsect := -Ttext 0x0 -s --oformat binary
+		LDFLAGS_setup    := -Ttext 0x0 -s --oformat binary -e begtext
+
+		targets += setup setup.o bootsect bootsect.o
+		$(obj)/setup $(obj)/bootsect: %: %.o FORCE
+			$(call if_changed,ld)
+
+	In this example, there are two possible targets, requiring different
+	options to the linker. The linker options are specified using the
+	LDFLAGS_$@ syntax - one for each potential target.
+	$(targets) are assigned all potential targets, by which kbuild knows
+	the targets and will:
+
+		1) check for commandline changes
+		2) delete target during make clean
+
+	The ": %: %.o" part of the prerequisite is a shorthand that
+	frees us from listing the setup.o and bootsect.o files.
+
+	Note:
+	      It is a common mistake to forget the "targets :=" assignment,
+	      resulting in the target file being recompiled for no
+	      obvious reason.
+
+    objcopy
+	Copy binary. Uses OBJCOPYFLAGS usually specified in
+	arch/$(ARCH)/Makefile.
+	OBJCOPYFLAGS_$@ may be used to set additional options.
+
+    gzip
+	Compress target. Use maximum compression to compress target.
+
+	Example::
+
+		#arch/x86/boot/compressed/Makefile
+		$(obj)/vmlinux.bin.gz: $(vmlinux.bin.all-y) FORCE
+			$(call if_changed,gzip)
+
+    dtc
+	Create flattened device tree blob object suitable for linking
+	into vmlinux. Device tree blobs linked into vmlinux are placed
+	in an init section in the image. Platform code *must* copy the
+	blob to non-init memory prior to calling unflatten_device_tree().
+
+	To use this command, simply add `*.dtb` into obj-y or targets, or make
+	some other target depend on `%.dtb`
+
+	A central rule exists to create `$(obj)/%.dtb` from `$(src)/%.dts`;
+	architecture Makefiles do no need to explicitly write out that rule.
+
+	Example::
+
+		targets += $(dtb-y)
+		DTC_FLAGS ?= -p 1024
+
+6.8 Custom kbuild commands
+--------------------------
+
+	When kbuild is executing with KBUILD_VERBOSE=0, then only a shorthand
+	of a command is normally displayed.
+	To enable this behaviour for custom commands kbuild requires
+	two variables to be set::
+
+		quiet_cmd_<command>	- what shall be echoed
+		      cmd_<command>	- the command to execute
+
+	Example::
+
+		#
+		quiet_cmd_image = BUILD   $@
+		      cmd_image = $(obj)/tools/build $(BUILDFLAGS) \
+		                                     $(obj)/vmlinux.bin > $@
+
+		targets += bzImage
+		$(obj)/bzImage: $(obj)/vmlinux.bin $(obj)/tools/build FORCE
+			$(call if_changed,image)
+			@echo 'Kernel: $@ is ready'
+
+	When updating the $(obj)/bzImage target, the line:
+
+		BUILD    arch/x86/boot/bzImage
+
+	will be displayed with "make KBUILD_VERBOSE=0".
+
+
+--- 6.9 Preprocessing linker scripts
+
+	When the vmlinux image is built, the linker script
+	arch/$(ARCH)/kernel/vmlinux.lds is used.
+	The script is a preprocessed variant of the file vmlinux.lds.S
+	located in the same directory.
+	kbuild knows .lds files and includes a rule `*lds.S` -> `*lds`.
+
+	Example::
+
+		#arch/x86/kernel/Makefile
+		always := vmlinux.lds
+
+		#Makefile
+		export CPPFLAGS_vmlinux.lds += -P -C -U$(ARCH)
+
+	The assignment to $(always) is used to tell kbuild to build the
+	target vmlinux.lds.
+	The assignment to $(CPPFLAGS_vmlinux.lds) tells kbuild to use the
+	specified options when building the target vmlinux.lds.
+
+	When building the `*.lds` target, kbuild uses the variables::
+
+		KBUILD_CPPFLAGS	: Set in top-level Makefile
+		cppflags-y	: May be set in the kbuild makefile
+		CPPFLAGS_$(@F)  : Target-specific flags.
+				Note that the full filename is used in this
+				assignment.
+
+	The kbuild infrastructure for `*lds` files is used in several
+	architecture-specific files.
+
+6.10 Generic header files
+-------------------------
+
+	The directory include/asm-generic contains the header files
+	that may be shared between individual architectures.
+	The recommended approach how to use a generic header file is
+	to list the file in the Kbuild file.
+	See "7.2 generic-y" for further info on syntax etc.
+
+6.11 Post-link pass
+-------------------
+
+	If the file arch/xxx/Makefile.postlink exists, this makefile
+	will be invoked for post-link objects (vmlinux and modules.ko)
+	for architectures to run post-link passes on. Must also handle
+	the clean target.
+
+	This pass runs after kallsyms generation. If the architecture
+	needs to modify symbol locations, rather than manipulate the
+	kallsyms, it may be easier to add another postlink target for
+	.tmp_vmlinux? targets to be called from link-vmlinux.sh.
+
+	For example, powerpc uses this to check relocation sanity of
+	the linked vmlinux file.
+
+7 Kbuild syntax for exported headers
+------------------------------------
+
+The kernel includes a set of headers that is exported to userspace.
+Many headers can be exported as-is but other headers require a
+minimal pre-processing before they are ready for user-space.
+The pre-processing does:
+
+- drop kernel-specific annotations
+- drop include of compiler.h
+- drop all sections that are kernel internal (guarded by `ifdef __KERNEL__`)
+
+All headers under include/uapi/, include/generated/uapi/,
+arch/<arch>/include/uapi/ and arch/<arch>/include/generated/uapi/
+are exported.
+
+A Kbuild file may be defined under arch/<arch>/include/uapi/asm/ and
+arch/<arch>/include/asm/ to list asm files coming from asm-generic.
+See subsequent chapter for the syntax of the Kbuild file.
+
+7.1 no-export-headers
+---------------------
+
+	no-export-headers is essentially used by include/uapi/linux/Kbuild to
+	avoid exporting specific headers (e.g. kvm.h) on architectures that do
+	not support it. It should be avoided as much as possible.
+
+7.2 generic-y
+-------------
+
+	If an architecture uses a verbatim copy of a header from
+	include/asm-generic then this is listed in the file
+	arch/$(ARCH)/include/asm/Kbuild like this:
+
+		Example::
+
+			#arch/x86/include/asm/Kbuild
+			generic-y += termios.h
+			generic-y += rtc.h
+
+	During the prepare phase of the build a wrapper include
+	file is generated in the directory::
+
+		arch/$(ARCH)/include/generated/asm
+
+	When a header is exported where the architecture uses
+	the generic header a similar wrapper is generated as part
+	of the set of exported headers in the directory::
+
+		usr/include/asm
+
+	The generated wrapper will in both cases look like the following:
+
+		Example: termios.h::
+
+			#include <asm-generic/termios.h>
+
+7.3 generated-y
+---------------
+
+	If an architecture generates other header files alongside generic-y
+	wrappers, generated-y specifies them.
+
+	This prevents them being treated as stale asm-generic wrappers and
+	removed.
+
+		Example::
+
+			#arch/x86/include/asm/Kbuild
+			generated-y += syscalls_32.h
+
+7.4 mandatory-y
+---------------
+
+	mandatory-y is essentially used by include/(uapi/)asm-generic/Kbuild
+	to define the minimum set of ASM headers that all architectures must have.
+
+	This works like optional generic-y. If a mandatory header is missing
+	in arch/$(ARCH)/include/(uapi/)/asm, Kbuild will automatically generate
+	a wrapper of the asm-generic one.
+
+	The convention is to list one subdir per line and
+	preferably in alphabetic order.
+
+8 Kbuild Variables
+==================
+
+The top Makefile exports the following variables:
+
+    VERSION, PATCHLEVEL, SUBLEVEL, EXTRAVERSION
+	These variables define the current kernel version.  A few arch
+	Makefiles actually use these values directly; they should use
+	$(KERNELRELEASE) instead.
+
+	$(VERSION), $(PATCHLEVEL), and $(SUBLEVEL) define the basic
+	three-part version number, such as "2", "4", and "0".  These three
+	values are always numeric.
+
+	$(EXTRAVERSION) defines an even tinier sublevel for pre-patches
+	or additional patches.	It is usually some non-numeric string
+	such as "-pre4", and is often blank.
+
+    KERNELRELEASE
+	$(KERNELRELEASE) is a single string such as "2.4.0-pre4", suitable
+	for constructing installation directory names or showing in
+	version strings.  Some arch Makefiles use it for this purpose.
+
+    ARCH
+	This variable defines the target architecture, such as "i386",
+	"arm", or "sparc". Some kbuild Makefiles test $(ARCH) to
+	determine which files to compile.
+
+	By default, the top Makefile sets $(ARCH) to be the same as the
+	host system architecture.  For a cross build, a user may
+	override the value of $(ARCH) on the command line::
+
+	    make ARCH=m68k ...
+
+
+    INSTALL_PATH
+	This variable defines a place for the arch Makefiles to install
+	the resident kernel image and System.map file.
+	Use this for architecture-specific install targets.
+
+    INSTALL_MOD_PATH, MODLIB
+	$(INSTALL_MOD_PATH) specifies a prefix to $(MODLIB) for module
+	installation.  This variable is not defined in the Makefile but
+	may be passed in by the user if desired.
+
+	$(MODLIB) specifies the directory for module installation.
+	The top Makefile defines $(MODLIB) to
+	$(INSTALL_MOD_PATH)/lib/modules/$(KERNELRELEASE).  The user may
+	override this value on the command line if desired.
+
+    INSTALL_MOD_STRIP
+	If this variable is specified, it will cause modules to be stripped
+	after they are installed.  If INSTALL_MOD_STRIP is '1', then the
+	default option --strip-debug will be used.  Otherwise, the
+	INSTALL_MOD_STRIP value will be used as the option(s) to the strip
+	command.
+
+
+9 Makefile language
+===================
+
+The kernel Makefiles are designed to be run with GNU Make.  The Makefiles
+use only the documented features of GNU Make, but they do use many
+GNU extensions.
+
+GNU Make supports elementary list-processing functions.  The kernel
+Makefiles use a novel style of list building and manipulation with few
+"if" statements.
+
+GNU Make has two assignment operators, ":=" and "=".  ":=" performs
+immediate evaluation of the right-hand side and stores an actual string
+into the left-hand side.  "=" is like a formula definition; it stores the
+right-hand side in an unevaluated form and then evaluates this form each
+time the left-hand side is used.
+
+There are some cases where "=" is appropriate.  Usually, though, ":="
+is the right choice.
+
+10 Credits
+==========
+
+- Original version made by Michael Elizabeth Chastain, <mailto:mec@shout.net>
+- Updates by Kai Germaschewski <kai@tp1.ruhr-uni-bochum.de>
+- Updates by Sam Ravnborg <sam@ravnborg.org>
+- Language QA by Jan Engelhardt <jengelh@gmx.de>
+
+11 TODO
+=======
+
+- Describe how kbuild supports shipped files with _shipped.
+- Generating offset header files.
+- Add more variables to section 7?
diff --git a/Documentation/kbuild/makefiles.txt b/Documentation/kbuild/makefiles.txt
deleted file mode 100644
index d65ad5746f94..000000000000
--- a/Documentation/kbuild/makefiles.txt
+++ /dev/null
@@ -1,1369 +0,0 @@
-Linux Kernel Makefiles
-
-This document describes the Linux kernel Makefiles.
-
-=== Table of Contents
-
-	=== 1 Overview
-	=== 2 Who does what
-	=== 3 The kbuild files
-	   --- 3.1 Goal definitions
-	   --- 3.2 Built-in object goals - obj-y
-	   --- 3.3 Loadable module goals - obj-m
-	   --- 3.4 Objects which export symbols
-	   --- 3.5 Library file goals - lib-y
-	   --- 3.6 Descending down in directories
-	   --- 3.7 Compilation flags
-	   --- 3.8 Command line dependency
-	   --- 3.9 Dependency tracking
-	   --- 3.10 Special Rules
-	   --- 3.11 $(CC) support functions
-	   --- 3.12 $(LD) support functions
-
-	=== 4 Host Program support
-	   --- 4.1 Simple Host Program
-	   --- 4.2 Composite Host Programs
-	   --- 4.3 Using C++ for host programs
-	   --- 4.4 Controlling compiler options for host programs
-	   --- 4.5 When host programs are actually built
-	   --- 4.6 Using hostprogs-$(CONFIG_FOO)
-
-	=== 5 Kbuild clean infrastructure
-
-	=== 6 Architecture Makefiles
-	   --- 6.1 Set variables to tweak the build to the architecture
-	   --- 6.2 Add prerequisites to archheaders:
-	   --- 6.3 Add prerequisites to archprepare:
-	   --- 6.4 List directories to visit when descending
-	   --- 6.5 Architecture-specific boot images
-	   --- 6.6 Building non-kbuild targets
-	   --- 6.7 Commands useful for building a boot image
-	   --- 6.8 Custom kbuild commands
-	   --- 6.9 Preprocessing linker scripts
-	   --- 6.10 Generic header files
-	   --- 6.11 Post-link pass
-
-	=== 7 Kbuild syntax for exported headers
-		--- 7.1 no-export-headers
-		--- 7.2 generic-y
-		--- 7.3 generated-y
-		--- 7.4 mandatory-y
-
-	=== 8 Kbuild Variables
-	=== 9 Makefile language
-	=== 10 Credits
-	=== 11 TODO
-
-=== 1 Overview
-
-The Makefiles have five parts:
-
-	Makefile		the top Makefile.
-	.config			the kernel configuration file.
-	arch/$(ARCH)/Makefile	the arch Makefile.
-	scripts/Makefile.*	common rules etc. for all kbuild Makefiles.
-	kbuild Makefiles	there are about 500 of these.
-
-The top Makefile reads the .config file, which comes from the kernel
-configuration process.
-
-The top Makefile is responsible for building two major products: vmlinux
-(the resident kernel image) and modules (any module files).
-It builds these goals by recursively descending into the subdirectories of
-the kernel source tree.
-The list of subdirectories which are visited depends upon the kernel
-configuration. The top Makefile textually includes an arch Makefile
-with the name arch/$(ARCH)/Makefile. The arch Makefile supplies
-architecture-specific information to the top Makefile.
-
-Each subdirectory has a kbuild Makefile which carries out the commands
-passed down from above. The kbuild Makefile uses information from the
-.config file to construct various file lists used by kbuild to build
-any built-in or modular targets.
-
-scripts/Makefile.* contains all the definitions/rules etc. that
-are used to build the kernel based on the kbuild makefiles.
-
-
-=== 2 Who does what
-
-People have four different relationships with the kernel Makefiles.
-
-*Users* are people who build kernels.  These people type commands such as
-"make menuconfig" or "make".  They usually do not read or edit
-any kernel Makefiles (or any other source files).
-
-*Normal developers* are people who work on features such as device
-drivers, file systems, and network protocols.  These people need to
-maintain the kbuild Makefiles for the subsystem they are
-working on.  In order to do this effectively, they need some overall
-knowledge about the kernel Makefiles, plus detailed knowledge about the
-public interface for kbuild.
-
-*Arch developers* are people who work on an entire architecture, such
-as sparc or ia64.  Arch developers need to know about the arch Makefile
-as well as kbuild Makefiles.
-
-*Kbuild developers* are people who work on the kernel build system itself.
-These people need to know about all aspects of the kernel Makefiles.
-
-This document is aimed towards normal developers and arch developers.
-
-
-=== 3 The kbuild files
-
-Most Makefiles within the kernel are kbuild Makefiles that use the
-kbuild infrastructure. This chapter introduces the syntax used in the
-kbuild makefiles.
-The preferred name for the kbuild files are 'Makefile' but 'Kbuild' can
-be used and if both a 'Makefile' and a 'Kbuild' file exists, then the 'Kbuild'
-file will be used.
-
-Section 3.1 "Goal definitions" is a quick intro, further chapters provide
-more details, with real examples.
-
---- 3.1 Goal definitions
-
-	Goal definitions are the main part (heart) of the kbuild Makefile.
-	These lines define the files to be built, any special compilation
-	options, and any subdirectories to be entered recursively.
-
-	The most simple kbuild makefile contains one line:
-
-	Example:
-		obj-y += foo.o
-
-	This tells kbuild that there is one object in that directory, named
-	foo.o. foo.o will be built from foo.c or foo.S.
-
-	If foo.o shall be built as a module, the variable obj-m is used.
-	Therefore the following pattern is often used:
-
-	Example:
-		obj-$(CONFIG_FOO) += foo.o
-
-	$(CONFIG_FOO) evaluates to either y (for built-in) or m (for module).
-	If CONFIG_FOO is neither y nor m, then the file will not be compiled
-	nor linked.
-
---- 3.2 Built-in object goals - obj-y
-
-	The kbuild Makefile specifies object files for vmlinux
-	in the $(obj-y) lists.  These lists depend on the kernel
-	configuration.
-
-	Kbuild compiles all the $(obj-y) files.  It then calls
-	"$(AR) rcSTP" to merge these files into one built-in.a file.
-	This is a thin archive without a symbol table. It will be later
-	linked into vmlinux by scripts/link-vmlinux.sh
-
-	The order of files in $(obj-y) is significant.  Duplicates in
-	the lists are allowed: the first instance will be linked into
-	built-in.a and succeeding instances will be ignored.
-
-	Link order is significant, because certain functions
-	(module_init() / __initcall) will be called during boot in the
-	order they appear. So keep in mind that changing the link
-	order may e.g. change the order in which your SCSI
-	controllers are detected, and thus your disks are renumbered.
-
-	Example:
-		#drivers/isdn/i4l/Makefile
-		# Makefile for the kernel ISDN subsystem and device drivers.
-		# Each configuration option enables a list of files.
-		obj-$(CONFIG_ISDN_I4L)         += isdn.o
-		obj-$(CONFIG_ISDN_PPP_BSDCOMP) += isdn_bsdcomp.o
-
---- 3.3 Loadable module goals - obj-m
-
-	$(obj-m) specifies object files which are built as loadable
-	kernel modules.
-
-	A module may be built from one source file or several source
-	files. In the case of one source file, the kbuild makefile
-	simply adds the file to $(obj-m).
-
-	Example:
-		#drivers/isdn/i4l/Makefile
-		obj-$(CONFIG_ISDN_PPP_BSDCOMP) += isdn_bsdcomp.o
-
-	Note: In this example $(CONFIG_ISDN_PPP_BSDCOMP) evaluates to 'm'
-
-	If a kernel module is built from several source files, you specify
-	that you want to build a module in the same way as above; however,
-	kbuild needs to know which object files you want to build your
-	module from, so you have to tell it by setting a $(<module_name>-y)
-	variable.
-
-	Example:
-		#drivers/isdn/i4l/Makefile
-		obj-$(CONFIG_ISDN_I4L) += isdn.o
-		isdn-y := isdn_net_lib.o isdn_v110.o isdn_common.o
-
-	In this example, the module name will be isdn.o. Kbuild will
-	compile the objects listed in $(isdn-y) and then run
-	"$(LD) -r" on the list of these files to generate isdn.o.
-
-	Due to kbuild recognizing $(<module_name>-y) for composite objects,
-	you can use the value of a CONFIG_ symbol to optionally include an
-	object file as part of a composite object.
-
-	Example:
-		#fs/ext2/Makefile
-	        obj-$(CONFIG_EXT2_FS) += ext2.o
-		ext2-y := balloc.o dir.o file.o ialloc.o inode.o ioctl.o \
-			  namei.o super.o symlink.o
-	        ext2-$(CONFIG_EXT2_FS_XATTR) += xattr.o xattr_user.o \
-						xattr_trusted.o
-
-	In this example, xattr.o, xattr_user.o and xattr_trusted.o are only
-	part of the composite object ext2.o if $(CONFIG_EXT2_FS_XATTR)
-	evaluates to 'y'.
-
-	Note: Of course, when you are building objects into the kernel,
-	the syntax above will also work. So, if you have CONFIG_EXT2_FS=y,
-	kbuild will build an ext2.o file for you out of the individual
-	parts and then link this into built-in.a, as you would expect.
-
---- 3.4 Objects which export symbols
-
-	No special notation is required in the makefiles for
-	modules exporting symbols.
-
---- 3.5 Library file goals - lib-y
-
-	Objects listed with obj-* are used for modules, or
-	combined in a built-in.a for that specific directory.
-	There is also the possibility to list objects that will
-	be included in a library, lib.a.
-	All objects listed with lib-y are combined in a single
-	library for that directory.
-	Objects that are listed in obj-y and additionally listed in
-	lib-y will not be included in the library, since they will
-	be accessible anyway.
-	For consistency, objects listed in lib-m will be included in lib.a.
-
-	Note that the same kbuild makefile may list files to be built-in
-	and to be part of a library. Therefore the same directory
-	may contain both a built-in.a and a lib.a file.
-
-	Example:
-		#arch/x86/lib/Makefile
-		lib-y    := delay.o
-
-	This will create a library lib.a based on delay.o. For kbuild to
-	actually recognize that there is a lib.a being built, the directory
-	shall be listed in libs-y.
-	See also "6.4 List directories to visit when descending".
-
-	Use of lib-y is normally restricted to lib/ and arch/*/lib.
-
---- 3.6 Descending down in directories
-
-	A Makefile is only responsible for building objects in its own
-	directory. Files in subdirectories should be taken care of by
-	Makefiles in these subdirs. The build system will automatically
-	invoke make recursively in subdirectories, provided you let it know of
-	them.
-
-	To do so, obj-y and obj-m are used.
-	ext2 lives in a separate directory, and the Makefile present in fs/
-	tells kbuild to descend down using the following assignment.
-
-	Example:
-		#fs/Makefile
-		obj-$(CONFIG_EXT2_FS) += ext2/
-
-	If CONFIG_EXT2_FS is set to either 'y' (built-in) or 'm' (modular)
-	the corresponding obj- variable will be set, and kbuild will descend
-	down in the ext2 directory.
-	Kbuild only uses this information to decide that it needs to visit
-	the directory, it is the Makefile in the subdirectory that
-	specifies what is modular and what is built-in.
-
-	It is good practice to use a CONFIG_ variable when assigning directory
-	names. This allows kbuild to totally skip the directory if the
-	corresponding CONFIG_ option is neither 'y' nor 'm'.
-
---- 3.7 Compilation flags
-
-    ccflags-y, asflags-y and ldflags-y
-	These three flags apply only to the kbuild makefile in which they
-	are assigned. They are used for all the normal cc, as and ld
-	invocations happening during a recursive build.
-	Note: Flags with the same behaviour were previously named:
-	EXTRA_CFLAGS, EXTRA_AFLAGS and EXTRA_LDFLAGS.
-	They are still supported but their usage is deprecated.
-
-	ccflags-y specifies options for compiling with $(CC).
-
-	Example:
-		# drivers/acpi/acpica/Makefile
-		ccflags-y			:= -Os -D_LINUX -DBUILDING_ACPICA
-		ccflags-$(CONFIG_ACPI_DEBUG)	+= -DACPI_DEBUG_OUTPUT
-
-	This variable is necessary because the top Makefile owns the
-	variable $(KBUILD_CFLAGS) and uses it for compilation flags for the
-	entire tree.
-
-	asflags-y specifies options for assembling with $(AS).
-
-	Example:
-		#arch/sparc/kernel/Makefile
-		asflags-y := -ansi
-
-	ldflags-y specifies options for linking with $(LD).
-
-	Example:
-		#arch/cris/boot/compressed/Makefile
-		ldflags-y += -T $(srctree)/$(src)/decompress_$(arch-y).lds
-
-    subdir-ccflags-y, subdir-asflags-y
-	The two flags listed above are similar to ccflags-y and asflags-y.
-	The difference is that the subdir- variants have effect for the kbuild
-	file where they are present and all subdirectories.
-	Options specified using subdir-* are added to the commandline before
-	the options specified using the non-subdir variants.
-
-	Example:
-		subdir-ccflags-y := -Werror
-
-    CFLAGS_$@, AFLAGS_$@
-
-	CFLAGS_$@ and AFLAGS_$@ only apply to commands in current
-	kbuild makefile.
-
-	$(CFLAGS_$@) specifies per-file options for $(CC).  The $@
-	part has a literal value which specifies the file that it is for.
-
-	Example:
-		# drivers/scsi/Makefile
-		CFLAGS_aha152x.o =   -DAHA152X_STAT -DAUTOCONF
-		CFLAGS_gdth.o    = # -DDEBUG_GDTH=2 -D__SERIAL__ -D__COM2__ \
-				     -DGDTH_STATISTICS
-
-	These two lines specify compilation flags for aha152x.o and gdth.o.
-
-	$(AFLAGS_$@) is a similar feature for source files in assembly
-	languages.
-
-	Example:
-		# arch/arm/kernel/Makefile
-		AFLAGS_head.o        := -DTEXT_OFFSET=$(TEXT_OFFSET)
-		AFLAGS_crunch-bits.o := -Wa,-mcpu=ep9312
-		AFLAGS_iwmmxt.o      := -Wa,-mcpu=iwmmxt
-
-
---- 3.9 Dependency tracking
-
-	Kbuild tracks dependencies on the following:
-	1) All prerequisite files (both *.c and *.h)
-	2) CONFIG_ options used in all prerequisite files
-	3) Command-line used to compile target
-
-	Thus, if you change an option to $(CC) all affected files will
-	be re-compiled.
-
---- 3.10 Special Rules
-
-	Special rules are used when the kbuild infrastructure does
-	not provide the required support. A typical example is
-	header files generated during the build process.
-	Another example are the architecture-specific Makefiles which
-	need special rules to prepare boot images etc.
-
-	Special rules are written as normal Make rules.
-	Kbuild is not executing in the directory where the Makefile is
-	located, so all special rules shall provide a relative
-	path to prerequisite files and target files.
-
-	Two variables are used when defining special rules:
-
-    $(src)
-	$(src) is a relative path which points to the directory
-	where the Makefile is located. Always use $(src) when
-	referring to files located in the src tree.
-
-    $(obj)
-	$(obj) is a relative path which points to the directory
-	where the target is saved. Always use $(obj) when
-	referring to generated files.
-
-	Example:
-		#drivers/scsi/Makefile
-		$(obj)/53c8xx_d.h: $(src)/53c7,8xx.scr $(src)/script_asm.pl
-			$(CPP) -DCHIP=810 - < $< | ... $(src)/script_asm.pl
-
-	This is a special rule, following the normal syntax
-	required by make.
-	The target file depends on two prerequisite files. References
-	to the target file are prefixed with $(obj), references
-	to prerequisites are referenced with $(src) (because they are not
-	generated files).
-
-    $(kecho)
-	echoing information to user in a rule is often a good practice
-	but when execution "make -s" one does not expect to see any output
-	except for warnings/errors.
-	To support this kbuild defines $(kecho) which will echo out the
-	text following $(kecho) to stdout except if "make -s" is used.
-
-	Example:
-		#arch/blackfin/boot/Makefile
-		$(obj)/vmImage: $(obj)/vmlinux.gz
-			$(call if_changed,uimage)
-			@$(kecho) 'Kernel: $@ is ready'
-
-
---- 3.11 $(CC) support functions
-
-	The kernel may be built with several different versions of
-	$(CC), each supporting a unique set of features and options.
-	kbuild provides basic support to check for valid options for $(CC).
-	$(CC) is usually the gcc compiler, but other alternatives are
-	available.
-
-    as-option
-	as-option is used to check if $(CC) -- when used to compile
-	assembler (*.S) files -- supports the given option. An optional
-	second option may be specified if the first option is not supported.
-
-	Example:
-		#arch/sh/Makefile
-		cflags-y += $(call as-option,-Wa$(comma)-isa=$(isa-y),)
-
-	In the above example, cflags-y will be assigned the option
-	-Wa$(comma)-isa=$(isa-y) if it is supported by $(CC).
-	The second argument is optional, and if supplied will be used
-	if first argument is not supported.
-
-    as-instr
-	as-instr checks if the assembler reports a specific instruction
-	and then outputs either option1 or option2
-	C escapes are supported in the test instruction
-	Note: as-instr-option uses KBUILD_AFLAGS for $(AS) options
-
-    cc-option
-	cc-option is used to check if $(CC) supports a given option, and if
-	not supported to use an optional second option.
-
-	Example:
-		#arch/x86/Makefile
-		cflags-y += $(call cc-option,-march=pentium-mmx,-march=i586)
-
-	In the above example, cflags-y will be assigned the option
-	-march=pentium-mmx if supported by $(CC), otherwise -march=i586.
-	The second argument to cc-option is optional, and if omitted,
-	cflags-y will be assigned no value if first option is not supported.
-	Note: cc-option uses KBUILD_CFLAGS for $(CC) options
-
-   cc-option-yn
-	cc-option-yn is used to check if gcc supports a given option
-	and return 'y' if supported, otherwise 'n'.
-
-	Example:
-		#arch/ppc/Makefile
-		biarch := $(call cc-option-yn, -m32)
-		aflags-$(biarch) += -a32
-		cflags-$(biarch) += -m32
-
-	In the above example, $(biarch) is set to y if $(CC) supports the -m32
-	option. When $(biarch) equals 'y', the expanded variables $(aflags-y)
-	and $(cflags-y) will be assigned the values -a32 and -m32,
-	respectively.
-	Note: cc-option-yn uses KBUILD_CFLAGS for $(CC) options
-
-    cc-disable-warning
-	cc-disable-warning checks if gcc supports a given warning and returns
-	the commandline switch to disable it. This special function is needed,
-	because gcc 4.4 and later accept any unknown -Wno-* option and only
-	warn about it if there is another warning in the source file.
-
-	Example:
-		KBUILD_CFLAGS += $(call cc-disable-warning, unused-but-set-variable)
-
-	In the above example, -Wno-unused-but-set-variable will be added to
-	KBUILD_CFLAGS only if gcc really accepts it.
-
-    cc-ifversion
-	cc-ifversion tests the version of $(CC) and equals the fourth parameter
-	if version expression is true, or the fifth (if given) if the version
-	expression is false.
-
-	Example:
-		#fs/reiserfs/Makefile
-		ccflags-y := $(call cc-ifversion, -lt, 0402, -O1)
-
-	In this example, ccflags-y will be assigned the value -O1 if the
-	$(CC) version is less than 4.2.
-	cc-ifversion takes all the shell operators:
-	-eq, -ne, -lt, -le, -gt, and -ge
-	The third parameter may be a text as in this example, but it may also
-	be an expanded variable or a macro.
-
-    cc-cross-prefix
-	cc-cross-prefix is used to check if there exists a $(CC) in path with
-	one of the listed prefixes. The first prefix where there exist a
-	prefix$(CC) in the PATH is returned - and if no prefix$(CC) is found
-	then nothing is returned.
-	Additional prefixes are separated by a single space in the
-	call of cc-cross-prefix.
-	This functionality is useful for architecture Makefiles that try
-	to set CROSS_COMPILE to well-known values but may have several
-	values to select between.
-	It is recommended only to try to set CROSS_COMPILE if it is a cross
-	build (host arch is different from target arch). And if CROSS_COMPILE
-	is already set then leave it with the old value.
-
-	Example:
-		#arch/m68k/Makefile
-		ifneq ($(SUBARCH),$(ARCH))
-		        ifeq ($(CROSS_COMPILE),)
-		               CROSS_COMPILE := $(call cc-cross-prefix, m68k-linux-gnu-)
-			endif
-		endif
-
---- 3.12 $(LD) support functions
-
-    ld-option
-	ld-option is used to check if $(LD) supports the supplied option.
-	ld-option takes two options as arguments.
-	The second argument is an optional option that can be used if the
-	first option is not supported by $(LD).
-
-	Example:
-		#Makefile
-		LDFLAGS_vmlinux += $(call ld-option, -X)
-
-
-=== 4 Host Program support
-
-Kbuild supports building executables on the host for use during the
-compilation stage.
-Two steps are required in order to use a host executable.
-
-The first step is to tell kbuild that a host program exists. This is
-done utilising the variable hostprogs-y.
-
-The second step is to add an explicit dependency to the executable.
-This can be done in two ways. Either add the dependency in a rule,
-or utilise the variable $(always).
-Both possibilities are described in the following.
-
---- 4.1 Simple Host Program
-
-	In some cases there is a need to compile and run a program on the
-	computer where the build is running.
-	The following line tells kbuild that the program bin2hex shall be
-	built on the build host.
-
-	Example:
-		hostprogs-y := bin2hex
-
-	Kbuild assumes in the above example that bin2hex is made from a single
-	c-source file named bin2hex.c located in the same directory as
-	the Makefile.
-
---- 4.2 Composite Host Programs
-
-	Host programs can be made up based on composite objects.
-	The syntax used to define composite objects for host programs is
-	similar to the syntax used for kernel objects.
-	$(<executable>-objs) lists all objects used to link the final
-	executable.
-
-	Example:
-		#scripts/lxdialog/Makefile
-		hostprogs-y   := lxdialog
-		lxdialog-objs := checklist.o lxdialog.o
-
-	Objects with extension .o are compiled from the corresponding .c
-	files. In the above example, checklist.c is compiled to checklist.o
-	and lxdialog.c is compiled to lxdialog.o.
-	Finally, the two .o files are linked to the executable, lxdialog.
-	Note: The syntax <executable>-y is not permitted for host-programs.
-
---- 4.3 Using C++ for host programs
-
-	kbuild offers support for host programs written in C++. This was
-	introduced solely to support kconfig, and is not recommended
-	for general use.
-
-	Example:
-		#scripts/kconfig/Makefile
-		hostprogs-y   := qconf
-		qconf-cxxobjs := qconf.o
-
-	In the example above the executable is composed of the C++ file
-	qconf.cc - identified by $(qconf-cxxobjs).
-
-	If qconf is composed of a mixture of .c and .cc files, then an
-	additional line can be used to identify this.
-
-	Example:
-		#scripts/kconfig/Makefile
-		hostprogs-y   := qconf
-		qconf-cxxobjs := qconf.o
-		qconf-objs    := check.o
-
---- 4.4 Controlling compiler options for host programs
-
-	When compiling host programs, it is possible to set specific flags.
-	The programs will always be compiled utilising $(HOSTCC) passed
-	the options specified in $(KBUILD_HOSTCFLAGS).
-	To set flags that will take effect for all host programs created
-	in that Makefile, use the variable HOST_EXTRACFLAGS.
-
-	Example:
-		#scripts/lxdialog/Makefile
-		HOST_EXTRACFLAGS += -I/usr/include/ncurses
-
-	To set specific flags for a single file the following construction
-	is used:
-
-	Example:
-		#arch/ppc64/boot/Makefile
-		HOSTCFLAGS_piggyback.o := -DKERNELBASE=$(KERNELBASE)
-
-	It is also possible to specify additional options to the linker.
-
-	Example:
-		#scripts/kconfig/Makefile
-		HOSTLDLIBS_qconf := -L$(QTDIR)/lib
-
-	When linking qconf, it will be passed the extra option
-	"-L$(QTDIR)/lib".
-
---- 4.5 When host programs are actually built
-
-	Kbuild will only build host-programs when they are referenced
-	as a prerequisite.
-	This is possible in two ways:
-
-	(1) List the prerequisite explicitly in a special rule.
-
-	Example:
-		#drivers/pci/Makefile
-		hostprogs-y := gen-devlist
-		$(obj)/devlist.h: $(src)/pci.ids $(obj)/gen-devlist
-			( cd $(obj); ./gen-devlist ) < $<
-
-	The target $(obj)/devlist.h will not be built before
-	$(obj)/gen-devlist is updated. Note that references to
-	the host programs in special rules must be prefixed with $(obj).
-
-	(2) Use $(always)
-	When there is no suitable special rule, and the host program
-	shall be built when a makefile is entered, the $(always)
-	variable shall be used.
-
-	Example:
-		#scripts/lxdialog/Makefile
-		hostprogs-y   := lxdialog
-		always        := $(hostprogs-y)
-
-	This will tell kbuild to build lxdialog even if not referenced in
-	any rule.
-
---- 4.6 Using hostprogs-$(CONFIG_FOO)
-
-	A typical pattern in a Kbuild file looks like this:
-
-	Example:
-		#scripts/Makefile
-		hostprogs-$(CONFIG_KALLSYMS) += kallsyms
-
-	Kbuild knows about both 'y' for built-in and 'm' for module.
-	So if a config symbol evaluates to 'm', kbuild will still build
-	the binary. In other words, Kbuild handles hostprogs-m exactly
-	like hostprogs-y. But only hostprogs-y is recommended to be used
-	when no CONFIG symbols are involved.
-
-=== 5 Kbuild clean infrastructure
-
-"make clean" deletes most generated files in the obj tree where the kernel
-is compiled. This includes generated files such as host programs.
-Kbuild knows targets listed in $(hostprogs-y), $(hostprogs-m), $(always),
-$(extra-y) and $(targets). They are all deleted during "make clean".
-Files matching the patterns "*.[oas]", "*.ko", plus some additional files
-generated by kbuild are deleted all over the kernel src tree when
-"make clean" is executed.
-
-Additional files can be specified in kbuild makefiles by use of $(clean-files).
-
-	Example:
-		#lib/Makefile
-		clean-files := crc32table.h
-
-When executing "make clean", the file "crc32table.h" will be deleted.
-Kbuild will assume files to be in the same relative directory as the
-Makefile, except if prefixed with $(objtree).
-
-To delete a directory hierarchy use:
-
-	Example:
-		#scripts/package/Makefile
-		clean-dirs := $(objtree)/debian/
-
-This will delete the directory debian in the toplevel directory, including all
-subdirectories.
-
-To exclude certain files from make clean, use the $(no-clean-files) variable.
-This is only a special case used in the top level Kbuild file:
-
-	Example:
-		#Kbuild
-		no-clean-files := $(bounds-file) $(offsets-file)
-
-Usually kbuild descends down in subdirectories due to "obj-* := dir/",
-but in the architecture makefiles where the kbuild infrastructure
-is not sufficient this sometimes needs to be explicit.
-
-	Example:
-		#arch/x86/boot/Makefile
-		subdir- := compressed/
-
-The above assignment instructs kbuild to descend down in the
-directory compressed/ when "make clean" is executed.
-
-To support the clean infrastructure in the Makefiles that build the
-final bootimage there is an optional target named archclean:
-
-	Example:
-		#arch/x86/Makefile
-		archclean:
-			$(Q)$(MAKE) $(clean)=arch/x86/boot
-
-When "make clean" is executed, make will descend down in arch/x86/boot,
-and clean as usual. The Makefile located in arch/x86/boot/ may use
-the subdir- trick to descend further down.
-
-Note 1: arch/$(ARCH)/Makefile cannot use "subdir-", because that file is
-included in the top level makefile, and the kbuild infrastructure
-is not operational at that point.
-
-Note 2: All directories listed in core-y, libs-y, drivers-y and net-y will
-be visited during "make clean".
-
-=== 6 Architecture Makefiles
-
-The top level Makefile sets up the environment and does the preparation,
-before starting to descend down in the individual directories.
-The top level makefile contains the generic part, whereas
-arch/$(ARCH)/Makefile contains what is required to set up kbuild
-for said architecture.
-To do so, arch/$(ARCH)/Makefile sets up a number of variables and defines
-a few targets.
-
-When kbuild executes, the following steps are followed (roughly):
-1) Configuration of the kernel => produce .config
-2) Store kernel version in include/linux/version.h
-3) Updating all other prerequisites to the target prepare:
-   - Additional prerequisites are specified in arch/$(ARCH)/Makefile
-4) Recursively descend down in all directories listed in
-   init-* core* drivers-* net-* libs-* and build all targets.
-   - The values of the above variables are expanded in arch/$(ARCH)/Makefile.
-5) All object files are then linked and the resulting file vmlinux is
-   located at the root of the obj tree.
-   The very first objects linked are listed in head-y, assigned by
-   arch/$(ARCH)/Makefile.
-6) Finally, the architecture-specific part does any required post processing
-   and builds the final bootimage.
-   - This includes building boot records
-   - Preparing initrd images and the like
-
-
---- 6.1 Set variables to tweak the build to the architecture
-
-    LDFLAGS		Generic $(LD) options
-
-	Flags used for all invocations of the linker.
-	Often specifying the emulation is sufficient.
-
-	Example:
-		#arch/s390/Makefile
-		LDFLAGS         := -m elf_s390
-	Note: ldflags-y can be used to further customise
-	the flags used. See chapter 3.7.
-
-    LDFLAGS_vmlinux	Options for $(LD) when linking vmlinux
-
-	LDFLAGS_vmlinux is used to specify additional flags to pass to
-	the linker when linking the final vmlinux image.
-	LDFLAGS_vmlinux uses the LDFLAGS_$@ support.
-
-	Example:
-		#arch/x86/Makefile
-		LDFLAGS_vmlinux := -e stext
-
-    OBJCOPYFLAGS	objcopy flags
-
-	When $(call if_changed,objcopy) is used to translate a .o file,
-	the flags specified in OBJCOPYFLAGS will be used.
-	$(call if_changed,objcopy) is often used to generate raw binaries on
-	vmlinux.
-
-	Example:
-		#arch/s390/Makefile
-		OBJCOPYFLAGS := -O binary
-
-		#arch/s390/boot/Makefile
-		$(obj)/image: vmlinux FORCE
-			$(call if_changed,objcopy)
-
-	In this example, the binary $(obj)/image is a binary version of
-	vmlinux. The usage of $(call if_changed,xxx) will be described later.
-
-    KBUILD_AFLAGS		$(AS) assembler flags
-
-	Default value - see top level Makefile
-	Append or modify as required per architecture.
-
-	Example:
-		#arch/sparc64/Makefile
-		KBUILD_AFLAGS += -m64 -mcpu=ultrasparc
-
-    KBUILD_CFLAGS		$(CC) compiler flags
-
-	Default value - see top level Makefile
-	Append or modify as required per architecture.
-
-	Often, the KBUILD_CFLAGS variable depends on the configuration.
-
-	Example:
-		#arch/x86/boot/compressed/Makefile
-		cflags-$(CONFIG_X86_32) := -march=i386
-		cflags-$(CONFIG_X86_64) := -mcmodel=small
-		KBUILD_CFLAGS += $(cflags-y)
-
-	Many arch Makefiles dynamically run the target C compiler to
-	probe supported options:
-
-		#arch/x86/Makefile
-
-		...
-		cflags-$(CONFIG_MPENTIUMII)     += $(call cc-option,\
-						-march=pentium2,-march=i686)
-		...
-		# Disable unit-at-a-time mode ...
-		KBUILD_CFLAGS += $(call cc-option,-fno-unit-at-a-time)
-		...
-
-
-	The first example utilises the trick that a config option expands
-	to 'y' when selected.
-
-    KBUILD_AFLAGS_KERNEL	$(AS) options specific for built-in
-
-	$(KBUILD_AFLAGS_KERNEL) contains extra C compiler flags used to compile
-	resident kernel code.
-
-    KBUILD_AFLAGS_MODULE   Options for $(AS) when building modules
-
-	$(KBUILD_AFLAGS_MODULE) is used to add arch-specific options that
-	are used for $(AS).
-	From commandline AFLAGS_MODULE shall be used (see kbuild.txt).
-
-    KBUILD_CFLAGS_KERNEL	$(CC) options specific for built-in
-
-	$(KBUILD_CFLAGS_KERNEL) contains extra C compiler flags used to compile
-	resident kernel code.
-
-    KBUILD_CFLAGS_MODULE   Options for $(CC) when building modules
-
-	$(KBUILD_CFLAGS_MODULE) is used to add arch-specific options that
-	are used for $(CC).
-	From commandline CFLAGS_MODULE shall be used (see kbuild.txt).
-
-    KBUILD_LDFLAGS_MODULE   Options for $(LD) when linking modules
-
-	$(KBUILD_LDFLAGS_MODULE) is used to add arch-specific options
-	used when linking modules. This is often a linker script.
-	From commandline LDFLAGS_MODULE shall be used (see kbuild.txt).
-
-    KBUILD_ARFLAGS   Options for $(AR) when creating archives
-
-	$(KBUILD_ARFLAGS) set by the top level Makefile to "D" (deterministic
-	mode) if this option is supported by $(AR).
-
-    ARCH_CPPFLAGS, ARCH_AFLAGS, ARCH_CFLAGS   Overrides the kbuild defaults
-
-	These variables are appended to the KBUILD_CPPFLAGS,
-	KBUILD_AFLAGS, and KBUILD_CFLAGS, respectively, after the
-	top-level Makefile has set any other flags. This provides a
-	means for an architecture to override the defaults.
-
-
---- 6.2 Add prerequisites to archheaders:
-
-	The archheaders: rule is used to generate header files that
-	may be installed into user space by "make header_install" or
-	"make headers_install_all".  In order to support
-	"make headers_install_all", this target has to be able to run
-	on an unconfigured tree, or a tree configured for another
-	architecture.
-
-	It is run before "make archprepare" when run on the
-	architecture itself.
-
-
---- 6.3 Add prerequisites to archprepare:
-
-	The archprepare: rule is used to list prerequisites that need to be
-	built before starting to descend down in the subdirectories.
-	This is usually used for header files containing assembler constants.
-
-		Example:
-		#arch/arm/Makefile
-		archprepare: maketools
-
-	In this example, the file target maketools will be processed
-	before descending down in the subdirectories.
-	See also chapter XXX-TODO that describe how kbuild supports
-	generating offset header files.
-
-
---- 6.4 List directories to visit when descending
-
-	An arch Makefile cooperates with the top Makefile to define variables
-	which specify how to build the vmlinux file.  Note that there is no
-	corresponding arch-specific section for modules; the module-building
-	machinery is all architecture-independent.
-
-
-    head-y, init-y, core-y, libs-y, drivers-y, net-y
-
-	$(head-y) lists objects to be linked first in vmlinux.
-	$(libs-y) lists directories where a lib.a archive can be located.
-	The rest list directories where a built-in.a object file can be
-	located.
-
-	$(init-y) objects will be located after $(head-y).
-	Then the rest follows in this order:
-	$(core-y), $(libs-y), $(drivers-y) and $(net-y).
-
-	The top level Makefile defines values for all generic directories,
-	and arch/$(ARCH)/Makefile only adds architecture-specific directories.
-
-	Example:
-		#arch/sparc64/Makefile
-		core-y += arch/sparc64/kernel/
-		libs-y += arch/sparc64/prom/ arch/sparc64/lib/
-		drivers-$(CONFIG_OPROFILE)  += arch/sparc64/oprofile/
-
-
---- 6.5 Architecture-specific boot images
-
-	An arch Makefile specifies goals that take the vmlinux file, compress
-	it, wrap it in bootstrapping code, and copy the resulting files
-	somewhere. This includes various kinds of installation commands.
-	The actual goals are not standardized across architectures.
-
-	It is common to locate any additional processing in a boot/
-	directory below arch/$(ARCH)/.
-
-	Kbuild does not provide any smart way to support building a
-	target specified in boot/. Therefore arch/$(ARCH)/Makefile shall
-	call make manually to build a target in boot/.
-
-	The recommended approach is to include shortcuts in
-	arch/$(ARCH)/Makefile, and use the full path when calling down
-	into the arch/$(ARCH)/boot/Makefile.
-
-	Example:
-		#arch/x86/Makefile
-		boot := arch/x86/boot
-		bzImage: vmlinux
-			$(Q)$(MAKE) $(build)=$(boot) $(boot)/$@
-
-	"$(Q)$(MAKE) $(build)=<dir>" is the recommended way to invoke
-	make in a subdirectory.
-
-	There are no rules for naming architecture-specific targets,
-	but executing "make help" will list all relevant targets.
-	To support this, $(archhelp) must be defined.
-
-	Example:
-		#arch/x86/Makefile
-		define archhelp
-		  echo  '* bzImage      - Image (arch/$(ARCH)/boot/bzImage)'
-		endif
-
-	When make is executed without arguments, the first goal encountered
-	will be built. In the top level Makefile the first goal present
-	is all:.
-	An architecture shall always, per default, build a bootable image.
-	In "make help", the default goal is highlighted with a '*'.
-	Add a new prerequisite to all: to select a default goal different
-	from vmlinux.
-
-	Example:
-		#arch/x86/Makefile
-		all: bzImage
-
-	When "make" is executed without arguments, bzImage will be built.
-
---- 6.6 Building non-kbuild targets
-
-    extra-y
-
-	extra-y specifies additional targets created in the current
-	directory, in addition to any targets specified by obj-*.
-
-	Listing all targets in extra-y is required for two purposes:
-	1) Enable kbuild to check changes in command lines
-	   - When $(call if_changed,xxx) is used
-	2) kbuild knows what files to delete during "make clean"
-
-	Example:
-		#arch/x86/kernel/Makefile
-		extra-y := head.o init_task.o
-
-	In this example, extra-y is used to list object files that
-	shall be built, but shall not be linked as part of built-in.a.
-
-
---- 6.7 Commands useful for building a boot image
-
-	Kbuild provides a few macros that are useful when building a
-	boot image.
-
-    if_changed
-
-	if_changed is the infrastructure used for the following commands.
-
-	Usage:
-		target: source(s) FORCE
-			$(call if_changed,ld/objcopy/gzip/...)
-
-	When the rule is evaluated, it is checked to see if any files
-	need an update, or the command line has changed since the last
-	invocation. The latter will force a rebuild if any options
-	to the executable have changed.
-	Any target that utilises if_changed must be listed in $(targets),
-	otherwise the command line check will fail, and the target will
-	always be built.
-	Assignments to $(targets) are without $(obj)/ prefix.
-	if_changed may be used in conjunction with custom commands as
-	defined in 6.8 "Custom kbuild commands".
-
-	Note: It is a typical mistake to forget the FORCE prerequisite.
-	Another common pitfall is that whitespace is sometimes
-	significant; for instance, the below will fail (note the extra space
-	after the comma):
-		target: source(s) FORCE
-	#WRONG!#	$(call if_changed, ld/objcopy/gzip/...)
-
-        Note: if_changed should not be used more than once per target.
-              It stores the executed command in a corresponding .cmd
-        file and multiple calls would result in overwrites and
-        unwanted results when the target is up to date and only the
-        tests on changed commands trigger execution of commands.
-
-    ld
-	Link target. Often, LDFLAGS_$@ is used to set specific options to ld.
-
-	Example:
-		#arch/x86/boot/Makefile
-		LDFLAGS_bootsect := -Ttext 0x0 -s --oformat binary
-		LDFLAGS_setup    := -Ttext 0x0 -s --oformat binary -e begtext
-
-		targets += setup setup.o bootsect bootsect.o
-		$(obj)/setup $(obj)/bootsect: %: %.o FORCE
-			$(call if_changed,ld)
-
-	In this example, there are two possible targets, requiring different
-	options to the linker. The linker options are specified using the
-	LDFLAGS_$@ syntax - one for each potential target.
-	$(targets) are assigned all potential targets, by which kbuild knows
-	the targets and will:
-		1) check for commandline changes
-		2) delete target during make clean
-
-	The ": %: %.o" part of the prerequisite is a shorthand that
-	frees us from listing the setup.o and bootsect.o files.
-	Note: It is a common mistake to forget the "targets :=" assignment,
-	      resulting in the target file being recompiled for no
-	      obvious reason.
-
-    objcopy
-	Copy binary. Uses OBJCOPYFLAGS usually specified in
-	arch/$(ARCH)/Makefile.
-	OBJCOPYFLAGS_$@ may be used to set additional options.
-
-    gzip
-	Compress target. Use maximum compression to compress target.
-
-	Example:
-		#arch/x86/boot/compressed/Makefile
-		$(obj)/vmlinux.bin.gz: $(vmlinux.bin.all-y) FORCE
-			$(call if_changed,gzip)
-
-    dtc
-	Create flattened device tree blob object suitable for linking
-	into vmlinux. Device tree blobs linked into vmlinux are placed
-	in an init section in the image. Platform code *must* copy the
-	blob to non-init memory prior to calling unflatten_device_tree().
-
-	To use this command, simply add *.dtb into obj-y or targets, or make
-	some other target depend on %.dtb
-
-	A central rule exists to create $(obj)/%.dtb from $(src)/%.dts;
-	architecture Makefiles do no need to explicitly write out that rule.
-
-	Example:
-		targets += $(dtb-y)
-		DTC_FLAGS ?= -p 1024
-
---- 6.8 Custom kbuild commands
-
-	When kbuild is executing with KBUILD_VERBOSE=0, then only a shorthand
-	of a command is normally displayed.
-	To enable this behaviour for custom commands kbuild requires
-	two variables to be set:
-	quiet_cmd_<command>	- what shall be echoed
-	      cmd_<command>	- the command to execute
-
-	Example:
-		#
-		quiet_cmd_image = BUILD   $@
-		      cmd_image = $(obj)/tools/build $(BUILDFLAGS) \
-		                                     $(obj)/vmlinux.bin > $@
-
-		targets += bzImage
-		$(obj)/bzImage: $(obj)/vmlinux.bin $(obj)/tools/build FORCE
-			$(call if_changed,image)
-			@echo 'Kernel: $@ is ready'
-
-	When updating the $(obj)/bzImage target, the line
-
-	BUILD    arch/x86/boot/bzImage
-
-	will be displayed with "make KBUILD_VERBOSE=0".
-
-
---- 6.9 Preprocessing linker scripts
-
-	When the vmlinux image is built, the linker script
-	arch/$(ARCH)/kernel/vmlinux.lds is used.
-	The script is a preprocessed variant of the file vmlinux.lds.S
-	located in the same directory.
-	kbuild knows .lds files and includes a rule *lds.S -> *lds.
-
-	Example:
-		#arch/x86/kernel/Makefile
-		always := vmlinux.lds
-
-		#Makefile
-		export CPPFLAGS_vmlinux.lds += -P -C -U$(ARCH)
-
-	The assignment to $(always) is used to tell kbuild to build the
-	target vmlinux.lds.
-	The assignment to $(CPPFLAGS_vmlinux.lds) tells kbuild to use the
-	specified options when building the target vmlinux.lds.
-
-	When building the *.lds target, kbuild uses the variables:
-	KBUILD_CPPFLAGS	: Set in top-level Makefile
-	cppflags-y	: May be set in the kbuild makefile
-	CPPFLAGS_$(@F)  : Target-specific flags.
-	                  Note that the full filename is used in this
-	                  assignment.
-
-	The kbuild infrastructure for *lds files is used in several
-	architecture-specific files.
-
---- 6.10 Generic header files
-
-	The directory include/asm-generic contains the header files
-	that may be shared between individual architectures.
-	The recommended approach how to use a generic header file is
-	to list the file in the Kbuild file.
-	See "7.2 generic-y" for further info on syntax etc.
-
---- 6.11 Post-link pass
-
-	If the file arch/xxx/Makefile.postlink exists, this makefile
-	will be invoked for post-link objects (vmlinux and modules.ko)
-	for architectures to run post-link passes on. Must also handle
-	the clean target.
-
-	This pass runs after kallsyms generation. If the architecture
-	needs to modify symbol locations, rather than manipulate the
-	kallsyms, it may be easier to add another postlink target for
-	.tmp_vmlinux? targets to be called from link-vmlinux.sh.
-
-	For example, powerpc uses this to check relocation sanity of
-	the linked vmlinux file.
-
-=== 7 Kbuild syntax for exported headers
-
-The kernel includes a set of headers that is exported to userspace.
-Many headers can be exported as-is but other headers require a
-minimal pre-processing before they are ready for user-space.
-The pre-processing does:
-- drop kernel-specific annotations
-- drop include of compiler.h
-- drop all sections that are kernel internal (guarded by ifdef __KERNEL__)
-
-All headers under include/uapi/, include/generated/uapi/,
-arch/<arch>/include/uapi/ and arch/<arch>/include/generated/uapi/
-are exported.
-
-A Kbuild file may be defined under arch/<arch>/include/uapi/asm/ and
-arch/<arch>/include/asm/ to list asm files coming from asm-generic.
-See subsequent chapter for the syntax of the Kbuild file.
-
---- 7.1 no-export-headers
-
-	no-export-headers is essentially used by include/uapi/linux/Kbuild to
-	avoid exporting specific headers (e.g. kvm.h) on architectures that do
-	not support it. It should be avoided as much as possible.
-
---- 7.2 generic-y
-
-	If an architecture uses a verbatim copy of a header from
-	include/asm-generic then this is listed in the file
-	arch/$(ARCH)/include/asm/Kbuild like this:
-
-		Example:
-			#arch/x86/include/asm/Kbuild
-			generic-y += termios.h
-			generic-y += rtc.h
-
-	During the prepare phase of the build a wrapper include
-	file is generated in the directory:
-
-		arch/$(ARCH)/include/generated/asm
-
-	When a header is exported where the architecture uses
-	the generic header a similar wrapper is generated as part
-	of the set of exported headers in the directory:
-
-		usr/include/asm
-
-	The generated wrapper will in both cases look like the following:
-
-		Example: termios.h
-			#include <asm-generic/termios.h>
-
---- 7.3 generated-y
-
-	If an architecture generates other header files alongside generic-y
-	wrappers, generated-y specifies them.
-
-	This prevents them being treated as stale asm-generic wrappers and
-	removed.
-
-		Example:
-			#arch/x86/include/asm/Kbuild
-			generated-y += syscalls_32.h
-
---- 7.4 mandatory-y
-
-	mandatory-y is essentially used by include/(uapi/)asm-generic/Kbuild
-	to define the minimum set of ASM headers that all architectures must have.
-
-	This works like optional generic-y. If a mandatory header is missing
-	in arch/$(ARCH)/include/(uapi/)/asm, Kbuild will automatically generate
-	a wrapper of the asm-generic one.
-
-	The convention is to list one subdir per line and
-	preferably in alphabetic order.
-
-=== 8 Kbuild Variables
-
-The top Makefile exports the following variables:
-
-    VERSION, PATCHLEVEL, SUBLEVEL, EXTRAVERSION
-
-	These variables define the current kernel version.  A few arch
-	Makefiles actually use these values directly; they should use
-	$(KERNELRELEASE) instead.
-
-	$(VERSION), $(PATCHLEVEL), and $(SUBLEVEL) define the basic
-	three-part version number, such as "2", "4", and "0".  These three
-	values are always numeric.
-
-	$(EXTRAVERSION) defines an even tinier sublevel for pre-patches
-	or additional patches.	It is usually some non-numeric string
-	such as "-pre4", and is often blank.
-
-    KERNELRELEASE
-
-	$(KERNELRELEASE) is a single string such as "2.4.0-pre4", suitable
-	for constructing installation directory names or showing in
-	version strings.  Some arch Makefiles use it for this purpose.
-
-    ARCH
-
-	This variable defines the target architecture, such as "i386",
-	"arm", or "sparc". Some kbuild Makefiles test $(ARCH) to
-	determine which files to compile.
-
-	By default, the top Makefile sets $(ARCH) to be the same as the
-	host system architecture.  For a cross build, a user may
-	override the value of $(ARCH) on the command line:
-
-	    make ARCH=m68k ...
-
-
-    INSTALL_PATH
-
-	This variable defines a place for the arch Makefiles to install
-	the resident kernel image and System.map file.
-	Use this for architecture-specific install targets.
-
-    INSTALL_MOD_PATH, MODLIB
-
-	$(INSTALL_MOD_PATH) specifies a prefix to $(MODLIB) for module
-	installation.  This variable is not defined in the Makefile but
-	may be passed in by the user if desired.
-
-	$(MODLIB) specifies the directory for module installation.
-	The top Makefile defines $(MODLIB) to
-	$(INSTALL_MOD_PATH)/lib/modules/$(KERNELRELEASE).  The user may
-	override this value on the command line if desired.
-
-    INSTALL_MOD_STRIP
-
-	If this variable is specified, it will cause modules to be stripped
-	after they are installed.  If INSTALL_MOD_STRIP is '1', then the
-	default option --strip-debug will be used.  Otherwise, the
-	INSTALL_MOD_STRIP value will be used as the option(s) to the strip
-	command.
-
-
-=== 9 Makefile language
-
-The kernel Makefiles are designed to be run with GNU Make.  The Makefiles
-use only the documented features of GNU Make, but they do use many
-GNU extensions.
-
-GNU Make supports elementary list-processing functions.  The kernel
-Makefiles use a novel style of list building and manipulation with few
-"if" statements.
-
-GNU Make has two assignment operators, ":=" and "=".  ":=" performs
-immediate evaluation of the right-hand side and stores an actual string
-into the left-hand side.  "=" is like a formula definition; it stores the
-right-hand side in an unevaluated form and then evaluates this form each
-time the left-hand side is used.
-
-There are some cases where "=" is appropriate.  Usually, though, ":="
-is the right choice.
-
-=== 10 Credits
-
-Original version made by Michael Elizabeth Chastain, <mailto:mec@shout.net>
-Updates by Kai Germaschewski <kai@tp1.ruhr-uni-bochum.de>
-Updates by Sam Ravnborg <sam@ravnborg.org>
-Language QA by Jan Engelhardt <jengelh@gmx.de>
-
-=== 11 TODO
-
-- Describe how kbuild supports shipped files with _shipped.
-- Generating offset header files.
-- Add more variables to section 7?
-
-
-
diff --git a/Documentation/kbuild/modules.rst b/Documentation/kbuild/modules.rst
new file mode 100644
index 000000000000..24e763482650
--- /dev/null
+++ b/Documentation/kbuild/modules.rst
@@ -0,0 +1,571 @@
+=========================
+Building External Modules
+=========================
+
+This document describes how to build an out-of-tree kernel module.
+
+.. Table of Contents
+
+	=== 1 Introduction
+	=== 2 How to Build External Modules
+	   --- 2.1 Command Syntax
+	   --- 2.2 Options
+	   --- 2.3 Targets
+	   --- 2.4 Building Separate Files
+	=== 3. Creating a Kbuild File for an External Module
+	   --- 3.1 Shared Makefile
+	   --- 3.2 Separate Kbuild file and Makefile
+	   --- 3.3 Binary Blobs
+	   --- 3.4 Building Multiple Modules
+	=== 4. Include Files
+	   --- 4.1 Kernel Includes
+	   --- 4.2 Single Subdirectory
+	   --- 4.3 Several Subdirectories
+	=== 5. Module Installation
+	   --- 5.1 INSTALL_MOD_PATH
+	   --- 5.2 INSTALL_MOD_DIR
+	=== 6. Module Versioning
+	   --- 6.1 Symbols From the Kernel (vmlinux + modules)
+	   --- 6.2 Symbols and External Modules
+	   --- 6.3 Symbols From Another External Module
+	=== 7. Tips & Tricks
+	   --- 7.1 Testing for CONFIG_FOO_BAR
+
+
+
+1. Introduction
+===============
+
+"kbuild" is the build system used by the Linux kernel. Modules must use
+kbuild to stay compatible with changes in the build infrastructure and
+to pick up the right flags to "gcc." Functionality for building modules
+both in-tree and out-of-tree is provided. The method for building
+either is similar, and all modules are initially developed and built
+out-of-tree.
+
+Covered in this document is information aimed at developers interested
+in building out-of-tree (or "external") modules. The author of an
+external module should supply a makefile that hides most of the
+complexity, so one only has to type "make" to build the module. This is
+easily accomplished, and a complete example will be presented in
+section 3.
+
+
+2. How to Build External Modules
+================================
+
+To build external modules, you must have a prebuilt kernel available
+that contains the configuration and header files used in the build.
+Also, the kernel must have been built with modules enabled. If you are
+using a distribution kernel, there will be a package for the kernel you
+are running provided by your distribution.
+
+An alternative is to use the "make" target "modules_prepare." This will
+make sure the kernel contains the information required. The target
+exists solely as a simple way to prepare a kernel source tree for
+building external modules.
+
+NOTE: "modules_prepare" will not build Module.symvers even if
+CONFIG_MODVERSIONS is set; therefore, a full kernel build needs to be
+executed to make module versioning work.
+
+2.1 Command Syntax
+==================
+
+	The command to build an external module is::
+
+		$ make -C <path_to_kernel_src> M=$PWD
+
+	The kbuild system knows that an external module is being built
+	due to the "M=<dir>" option given in the command.
+
+	To build against the running kernel use::
+
+		$ make -C /lib/modules/`uname -r`/build M=$PWD
+
+	Then to install the module(s) just built, add the target
+	"modules_install" to the command::
+
+		$ make -C /lib/modules/`uname -r`/build M=$PWD modules_install
+
+2.2 Options
+===========
+
+	($KDIR refers to the path of the kernel source directory.)
+
+	make -C $KDIR M=$PWD
+
+	-C $KDIR
+		The directory where the kernel source is located.
+		"make" will actually change to the specified directory
+		when executing and will change back when finished.
+
+	M=$PWD
+		Informs kbuild that an external module is being built.
+		The value given to "M" is the absolute path of the
+		directory where the external module (kbuild file) is
+		located.
+
+2.3 Targets
+===========
+
+	When building an external module, only a subset of the "make"
+	targets are available.
+
+	make -C $KDIR M=$PWD [target]
+
+	The default will build the module(s) located in the current
+	directory, so a target does not need to be specified. All
+	output files will also be generated in this directory. No
+	attempts are made to update the kernel source, and it is a
+	precondition that a successful "make" has been executed for the
+	kernel.
+
+	modules
+		The default target for external modules. It has the
+		same functionality as if no target was specified. See
+		description above.
+
+	modules_install
+		Install the external module(s). The default location is
+		/lib/modules/<kernel_release>/extra/, but a prefix may
+		be added with INSTALL_MOD_PATH (discussed in section 5).
+
+	clean
+		Remove all generated files in the module directory only.
+
+	help
+		List the available targets for external modules.
+
+2.4 Building Separate Files
+===========================
+
+	It is possible to build single files that are part of a module.
+	This works equally well for the kernel, a module, and even for
+	external modules.
+
+	Example (The module foo.ko, consist of bar.o and baz.o)::
+
+		make -C $KDIR M=$PWD bar.lst
+		make -C $KDIR M=$PWD baz.o
+		make -C $KDIR M=$PWD foo.ko
+		make -C $KDIR M=$PWD ./
+
+
+3. Creating a Kbuild File for an External Module
+================================================
+
+In the last section we saw the command to build a module for the
+running kernel. The module is not actually built, however, because a
+build file is required. Contained in this file will be the name of
+the module(s) being built, along with the list of requisite source
+files. The file may be as simple as a single line::
+
+	obj-m := <module_name>.o
+
+The kbuild system will build <module_name>.o from <module_name>.c,
+and, after linking, will result in the kernel module <module_name>.ko.
+The above line can be put in either a "Kbuild" file or a "Makefile."
+When the module is built from multiple sources, an additional line is
+needed listing the files::
+
+	<module_name>-y := <src1>.o <src2>.o ...
+
+NOTE: Further documentation describing the syntax used by kbuild is
+located in Documentation/kbuild/makefiles.rst.
+
+The examples below demonstrate how to create a build file for the
+module 8123.ko, which is built from the following files::
+
+	8123_if.c
+	8123_if.h
+	8123_pci.c
+	8123_bin.o_shipped	<= Binary blob
+
+--- 3.1 Shared Makefile
+
+	An external module always includes a wrapper makefile that
+	supports building the module using "make" with no arguments.
+	This target is not used by kbuild; it is only for convenience.
+	Additional functionality, such as test targets, can be included
+	but should be filtered out from kbuild due to possible name
+	clashes.
+
+	Example 1::
+
+		--> filename: Makefile
+		ifneq ($(KERNELRELEASE),)
+		# kbuild part of makefile
+		obj-m  := 8123.o
+		8123-y := 8123_if.o 8123_pci.o 8123_bin.o
+
+		else
+		# normal makefile
+		KDIR ?= /lib/modules/`uname -r`/build
+
+		default:
+			$(MAKE) -C $(KDIR) M=$$PWD
+
+		# Module specific targets
+		genbin:
+			echo "X" > 8123_bin.o_shipped
+
+		endif
+
+	The check for KERNELRELEASE is used to separate the two parts
+	of the makefile. In the example, kbuild will only see the two
+	assignments, whereas "make" will see everything except these
+	two assignments. This is due to two passes made on the file:
+	the first pass is by the "make" instance run on the command
+	line; the second pass is by the kbuild system, which is
+	initiated by the parameterized "make" in the default target.
+
+3.2 Separate Kbuild File and Makefile
+-------------------------------------
+
+	In newer versions of the kernel, kbuild will first look for a
+	file named "Kbuild," and only if that is not found, will it
+	then look for a makefile. Utilizing a "Kbuild" file allows us
+	to split up the makefile from example 1 into two files:
+
+	Example 2::
+
+		--> filename: Kbuild
+		obj-m  := 8123.o
+		8123-y := 8123_if.o 8123_pci.o 8123_bin.o
+
+		--> filename: Makefile
+		KDIR ?= /lib/modules/`uname -r`/build
+
+		default:
+			$(MAKE) -C $(KDIR) M=$$PWD
+
+		# Module specific targets
+		genbin:
+			echo "X" > 8123_bin.o_shipped
+
+	The split in example 2 is questionable due to the simplicity of
+	each file; however, some external modules use makefiles
+	consisting of several hundred lines, and here it really pays
+	off to separate the kbuild part from the rest.
+
+	The next example shows a backward compatible version.
+
+	Example 3::
+
+		--> filename: Kbuild
+		obj-m  := 8123.o
+		8123-y := 8123_if.o 8123_pci.o 8123_bin.o
+
+		--> filename: Makefile
+		ifneq ($(KERNELRELEASE),)
+		# kbuild part of makefile
+		include Kbuild
+
+		else
+		# normal makefile
+		KDIR ?= /lib/modules/`uname -r`/build
+
+		default:
+			$(MAKE) -C $(KDIR) M=$$PWD
+
+		# Module specific targets
+		genbin:
+			echo "X" > 8123_bin.o_shipped
+
+		endif
+
+	Here the "Kbuild" file is included from the makefile. This
+	allows an older version of kbuild, which only knows of
+	makefiles, to be used when the "make" and kbuild parts are
+	split into separate files.
+
+3.3 Binary Blobs
+----------------
+
+	Some external modules need to include an object file as a blob.
+	kbuild has support for this, but requires the blob file to be
+	named <filename>_shipped. When the kbuild rules kick in, a copy
+	of <filename>_shipped is created with _shipped stripped off,
+	giving us <filename>. This shortened filename can be used in
+	the assignment to the module.
+
+	Throughout this section, 8123_bin.o_shipped has been used to
+	build the kernel module 8123.ko; it has been included as
+	8123_bin.o::
+
+		8123-y := 8123_if.o 8123_pci.o 8123_bin.o
+
+	Although there is no distinction between the ordinary source
+	files and the binary file, kbuild will pick up different rules
+	when creating the object file for the module.
+
+3.4 Building Multiple Modules
+=============================
+
+	kbuild supports building multiple modules with a single build
+	file. For example, if you wanted to build two modules, foo.ko
+	and bar.ko, the kbuild lines would be::
+
+		obj-m := foo.o bar.o
+		foo-y := <foo_srcs>
+		bar-y := <bar_srcs>
+
+	It is that simple!
+
+
+4. Include Files
+================
+
+Within the kernel, header files are kept in standard locations
+according to the following rule:
+
+	* If the header file only describes the internal interface of a
+	  module, then the file is placed in the same directory as the
+	  source files.
+	* If the header file describes an interface used by other parts
+	  of the kernel that are located in different directories, then
+	  the file is placed in include/linux/.
+
+	  NOTE:
+	      There are two notable exceptions to this rule: larger
+	      subsystems have their own directory under include/, such as
+	      include/scsi; and architecture specific headers are located
+	      under arch/$(ARCH)/include/.
+
+4.1 Kernel Includes
+-------------------
+
+	To include a header file located under include/linux/, simply
+	use::
+
+		#include <linux/module.h>
+
+	kbuild will add options to "gcc" so the relevant directories
+	are searched.
+
+4.2 Single Subdirectory
+-----------------------
+
+	External modules tend to place header files in a separate
+	include/ directory where their source is located, although this
+	is not the usual kernel style. To inform kbuild of the
+	directory, use either ccflags-y or CFLAGS_<filename>.o.
+
+	Using the example from section 3, if we moved 8123_if.h to a
+	subdirectory named include, the resulting kbuild file would
+	look like::
+
+		--> filename: Kbuild
+		obj-m := 8123.o
+
+		ccflags-y := -Iinclude
+		8123-y := 8123_if.o 8123_pci.o 8123_bin.o
+
+	Note that in the assignment there is no space between -I and
+	the path. This is a limitation of kbuild: there must be no
+	space present.
+
+4.3 Several Subdirectories
+--------------------------
+
+	kbuild can handle files that are spread over several directories.
+	Consider the following example::
+
+		.
+		|__ src
+		|   |__ complex_main.c
+		|   |__ hal
+		|	|__ hardwareif.c
+		|	|__ include
+		|	    |__ hardwareif.h
+		|__ include
+		|__ complex.h
+
+	To build the module complex.ko, we then need the following
+	kbuild file::
+
+		--> filename: Kbuild
+		obj-m := complex.o
+		complex-y := src/complex_main.o
+		complex-y += src/hal/hardwareif.o
+
+		ccflags-y := -I$(src)/include
+		ccflags-y += -I$(src)/src/hal/include
+
+	As you can see, kbuild knows how to handle object files located
+	in other directories. The trick is to specify the directory
+	relative to the kbuild file's location. That being said, this
+	is NOT recommended practice.
+
+	For the header files, kbuild must be explicitly told where to
+	look. When kbuild executes, the current directory is always the
+	root of the kernel tree (the argument to "-C") and therefore an
+	absolute path is needed. $(src) provides the absolute path by
+	pointing to the directory where the currently executing kbuild
+	file is located.
+
+
+5. Module Installation
+======================
+
+Modules which are included in the kernel are installed in the
+directory:
+
+	/lib/modules/$(KERNELRELEASE)/kernel/
+
+And external modules are installed in:
+
+	/lib/modules/$(KERNELRELEASE)/extra/
+
+5.1 INSTALL_MOD_PATH
+--------------------
+
+	Above are the default directories but as always some level of
+	customization is possible. A prefix can be added to the
+	installation path using the variable INSTALL_MOD_PATH::
+
+		$ make INSTALL_MOD_PATH=/frodo modules_install
+		=> Install dir: /frodo/lib/modules/$(KERNELRELEASE)/kernel/
+
+	INSTALL_MOD_PATH may be set as an ordinary shell variable or,
+	as shown above, can be specified on the command line when
+	calling "make." This has effect when installing both in-tree
+	and out-of-tree modules.
+
+5.2 INSTALL_MOD_DIR
+-------------------
+
+	External modules are by default installed to a directory under
+	/lib/modules/$(KERNELRELEASE)/extra/, but you may wish to
+	locate modules for a specific functionality in a separate
+	directory. For this purpose, use INSTALL_MOD_DIR to specify an
+	alternative name to "extra."::
+
+		$ make INSTALL_MOD_DIR=gandalf -C $KDIR \
+		       M=$PWD modules_install
+		=> Install dir: /lib/modules/$(KERNELRELEASE)/gandalf/
+
+
+6. Module Versioning
+====================
+
+Module versioning is enabled by the CONFIG_MODVERSIONS tag, and is used
+as a simple ABI consistency check. A CRC value of the full prototype
+for an exported symbol is created. When a module is loaded/used, the
+CRC values contained in the kernel are compared with similar values in
+the module; if they are not equal, the kernel refuses to load the
+module.
+
+Module.symvers contains a list of all exported symbols from a kernel
+build.
+
+6.1 Symbols From the Kernel (vmlinux + modules)
+-----------------------------------------------
+
+	During a kernel build, a file named Module.symvers will be
+	generated. Module.symvers contains all exported symbols from
+	the kernel and compiled modules. For each symbol, the
+	corresponding CRC value is also stored.
+
+	The syntax of the Module.symvers file is::
+
+		<CRC>	    <Symbol>	       <module>
+
+		0x2d036834  scsi_remove_host   drivers/scsi/scsi_mod
+
+	For a kernel build without CONFIG_MODVERSIONS enabled, the CRC
+	would read 0x00000000.
+
+	Module.symvers serves two purposes:
+
+	1) It lists all exported symbols from vmlinux and all modules.
+	2) It lists the CRC if CONFIG_MODVERSIONS is enabled.
+
+6.2 Symbols and External Modules
+--------------------------------
+
+	When building an external module, the build system needs access
+	to the symbols from the kernel to check if all external symbols
+	are defined. This is done in the MODPOST step. modpost obtains
+	the symbols by reading Module.symvers from the kernel source
+	tree. If a Module.symvers file is present in the directory
+	where the external module is being built, this file will be
+	read too. During the MODPOST step, a new Module.symvers file
+	will be written containing all exported symbols that were not
+	defined in the kernel.
+
+--- 6.3 Symbols From Another External Module
+
+	Sometimes, an external module uses exported symbols from
+	another external module. kbuild needs to have full knowledge of
+	all symbols to avoid spitting out warnings about undefined
+	symbols. Three solutions exist for this situation.
+
+	NOTE: The method with a top-level kbuild file is recommended
+	but may be impractical in certain situations.
+
+	Use a top-level kbuild file
+		If you have two modules, foo.ko and bar.ko, where
+		foo.ko needs symbols from bar.ko, you can use a
+		common top-level kbuild file so both modules are
+		compiled in the same build. Consider the following
+		directory layout::
+
+			./foo/ <= contains foo.ko
+			./bar/ <= contains bar.ko
+
+		The top-level kbuild file would then look like::
+
+			#./Kbuild (or ./Makefile):
+				obj-y := foo/ bar/
+
+		And executing::
+
+			$ make -C $KDIR M=$PWD
+
+		will then do the expected and compile both modules with
+		full knowledge of symbols from either module.
+
+	Use an extra Module.symvers file
+		When an external module is built, a Module.symvers file
+		is generated containing all exported symbols which are
+		not defined in the kernel. To get access to symbols
+		from bar.ko, copy the Module.symvers file from the
+		compilation of bar.ko to the directory where foo.ko is
+		built. During the module build, kbuild will read the
+		Module.symvers file in the directory of the external
+		module, and when the build is finished, a new
+		Module.symvers file is created containing the sum of
+		all symbols defined and not part of the kernel.
+
+	Use "make" variable KBUILD_EXTRA_SYMBOLS
+		If it is impractical to copy Module.symvers from
+		another module, you can assign a space separated list
+		of files to KBUILD_EXTRA_SYMBOLS in your build file.
+		These files will be loaded by modpost during the
+		initialization of its symbol tables.
+
+
+7. Tips & Tricks
+================
+
+7.1 Testing for CONFIG_FOO_BAR
+------------------------------
+
+	Modules often need to check for certain `CONFIG_` options to
+	decide if a specific feature is included in the module. In
+	kbuild this is done by referencing the `CONFIG_` variable
+	directly::
+
+		#fs/ext2/Makefile
+		obj-$(CONFIG_EXT2_FS) += ext2.o
+
+		ext2-y := balloc.o bitmap.o dir.o
+		ext2-$(CONFIG_EXT2_FS_XATTR) += xattr.o
+
+	External modules have traditionally used "grep" to check for
+	specific `CONFIG_` settings directly in .config. This usage is
+	broken. As introduced before, external modules should use
+	kbuild for building and can therefore use the same methods as
+	in-tree modules when testing for `CONFIG_` definitions.
diff --git a/Documentation/kbuild/modules.txt b/Documentation/kbuild/modules.txt
deleted file mode 100644
index 80295c613e37..000000000000
--- a/Documentation/kbuild/modules.txt
+++ /dev/null
@@ -1,541 +0,0 @@
-Building External Modules
-
-This document describes how to build an out-of-tree kernel module.
-
-=== Table of Contents
-
-	=== 1 Introduction
-	=== 2 How to Build External Modules
-	   --- 2.1 Command Syntax
-	   --- 2.2 Options
-	   --- 2.3 Targets
-	   --- 2.4 Building Separate Files
-	=== 3. Creating a Kbuild File for an External Module
-	   --- 3.1 Shared Makefile
-	   --- 3.2 Separate Kbuild file and Makefile
-	   --- 3.3 Binary Blobs
-	   --- 3.4 Building Multiple Modules
-	=== 4. Include Files
-	   --- 4.1 Kernel Includes
-	   --- 4.2 Single Subdirectory
-	   --- 4.3 Several Subdirectories
-	=== 5. Module Installation
-	   --- 5.1 INSTALL_MOD_PATH
-	   --- 5.2 INSTALL_MOD_DIR
-	=== 6. Module Versioning
-	   --- 6.1 Symbols From the Kernel (vmlinux + modules)
-	   --- 6.2 Symbols and External Modules
-	   --- 6.3 Symbols From Another External Module
-	=== 7. Tips & Tricks
-	   --- 7.1 Testing for CONFIG_FOO_BAR
-
-
-
-=== 1. Introduction
-
-"kbuild" is the build system used by the Linux kernel. Modules must use
-kbuild to stay compatible with changes in the build infrastructure and
-to pick up the right flags to "gcc." Functionality for building modules
-both in-tree and out-of-tree is provided. The method for building
-either is similar, and all modules are initially developed and built
-out-of-tree.
-
-Covered in this document is information aimed at developers interested
-in building out-of-tree (or "external") modules. The author of an
-external module should supply a makefile that hides most of the
-complexity, so one only has to type "make" to build the module. This is
-easily accomplished, and a complete example will be presented in
-section 3.
-
-
-=== 2. How to Build External Modules
-
-To build external modules, you must have a prebuilt kernel available
-that contains the configuration and header files used in the build.
-Also, the kernel must have been built with modules enabled. If you are
-using a distribution kernel, there will be a package for the kernel you
-are running provided by your distribution.
-
-An alternative is to use the "make" target "modules_prepare." This will
-make sure the kernel contains the information required. The target
-exists solely as a simple way to prepare a kernel source tree for
-building external modules.
-
-NOTE: "modules_prepare" will not build Module.symvers even if
-CONFIG_MODVERSIONS is set; therefore, a full kernel build needs to be
-executed to make module versioning work.
-
---- 2.1 Command Syntax
-
-	The command to build an external module is:
-
-		$ make -C <path_to_kernel_src> M=$PWD
-
-	The kbuild system knows that an external module is being built
-	due to the "M=<dir>" option given in the command.
-
-	To build against the running kernel use:
-
-		$ make -C /lib/modules/`uname -r`/build M=$PWD
-
-	Then to install the module(s) just built, add the target
-	"modules_install" to the command:
-
-		$ make -C /lib/modules/`uname -r`/build M=$PWD modules_install
-
---- 2.2 Options
-
-	($KDIR refers to the path of the kernel source directory.)
-
-	make -C $KDIR M=$PWD
-
-	-C $KDIR
-		The directory where the kernel source is located.
-		"make" will actually change to the specified directory
-		when executing and will change back when finished.
-
-	M=$PWD
-		Informs kbuild that an external module is being built.
-		The value given to "M" is the absolute path of the
-		directory where the external module (kbuild file) is
-		located.
-
---- 2.3 Targets
-
-	When building an external module, only a subset of the "make"
-	targets are available.
-
-	make -C $KDIR M=$PWD [target]
-
-	The default will build the module(s) located in the current
-	directory, so a target does not need to be specified. All
-	output files will also be generated in this directory. No
-	attempts are made to update the kernel source, and it is a
-	precondition that a successful "make" has been executed for the
-	kernel.
-
-	modules
-		The default target for external modules. It has the
-		same functionality as if no target was specified. See
-		description above.
-
-	modules_install
-		Install the external module(s). The default location is
-		/lib/modules/<kernel_release>/extra/, but a prefix may
-		be added with INSTALL_MOD_PATH (discussed in section 5).
-
-	clean
-		Remove all generated files in the module directory only.
-
-	help
-		List the available targets for external modules.
-
---- 2.4 Building Separate Files
-
-	It is possible to build single files that are part of a module.
-	This works equally well for the kernel, a module, and even for
-	external modules.
-
-	Example (The module foo.ko, consist of bar.o and baz.o):
-		make -C $KDIR M=$PWD bar.lst
-		make -C $KDIR M=$PWD baz.o
-		make -C $KDIR M=$PWD foo.ko
-		make -C $KDIR M=$PWD ./
-
-
-=== 3. Creating a Kbuild File for an External Module
-
-In the last section we saw the command to build a module for the
-running kernel. The module is not actually built, however, because a
-build file is required. Contained in this file will be the name of
-the module(s) being built, along with the list of requisite source
-files. The file may be as simple as a single line:
-
-	obj-m := <module_name>.o
-
-The kbuild system will build <module_name>.o from <module_name>.c,
-and, after linking, will result in the kernel module <module_name>.ko.
-The above line can be put in either a "Kbuild" file or a "Makefile."
-When the module is built from multiple sources, an additional line is
-needed listing the files:
-
-	<module_name>-y := <src1>.o <src2>.o ...
-
-NOTE: Further documentation describing the syntax used by kbuild is
-located in Documentation/kbuild/makefiles.txt.
-
-The examples below demonstrate how to create a build file for the
-module 8123.ko, which is built from the following files:
-
-	8123_if.c
-	8123_if.h
-	8123_pci.c
-	8123_bin.o_shipped	<= Binary blob
-
---- 3.1 Shared Makefile
-
-	An external module always includes a wrapper makefile that
-	supports building the module using "make" with no arguments.
-	This target is not used by kbuild; it is only for convenience.
-	Additional functionality, such as test targets, can be included
-	but should be filtered out from kbuild due to possible name
-	clashes.
-
-	Example 1:
-		--> filename: Makefile
-		ifneq ($(KERNELRELEASE),)
-		# kbuild part of makefile
-		obj-m  := 8123.o
-		8123-y := 8123_if.o 8123_pci.o 8123_bin.o
-
-		else
-		# normal makefile
-		KDIR ?= /lib/modules/`uname -r`/build
-
-		default:
-			$(MAKE) -C $(KDIR) M=$$PWD
-
-		# Module specific targets
-		genbin:
-			echo "X" > 8123_bin.o_shipped
-
-		endif
-
-	The check for KERNELRELEASE is used to separate the two parts
-	of the makefile. In the example, kbuild will only see the two
-	assignments, whereas "make" will see everything except these
-	two assignments. This is due to two passes made on the file:
-	the first pass is by the "make" instance run on the command
-	line; the second pass is by the kbuild system, which is
-	initiated by the parameterized "make" in the default target.
-
---- 3.2 Separate Kbuild File and Makefile
-
-	In newer versions of the kernel, kbuild will first look for a
-	file named "Kbuild," and only if that is not found, will it
-	then look for a makefile. Utilizing a "Kbuild" file allows us
-	to split up the makefile from example 1 into two files:
-
-	Example 2:
-		--> filename: Kbuild
-		obj-m  := 8123.o
-		8123-y := 8123_if.o 8123_pci.o 8123_bin.o
-
-		--> filename: Makefile
-		KDIR ?= /lib/modules/`uname -r`/build
-
-		default:
-			$(MAKE) -C $(KDIR) M=$$PWD
-
-		# Module specific targets
-		genbin:
-			echo "X" > 8123_bin.o_shipped
-
-	The split in example 2 is questionable due to the simplicity of
-	each file; however, some external modules use makefiles
-	consisting of several hundred lines, and here it really pays
-	off to separate the kbuild part from the rest.
-
-	The next example shows a backward compatible version.
-
-	Example 3:
-		--> filename: Kbuild
-		obj-m  := 8123.o
-		8123-y := 8123_if.o 8123_pci.o 8123_bin.o
-
-		--> filename: Makefile
-		ifneq ($(KERNELRELEASE),)
-		# kbuild part of makefile
-		include Kbuild
-
-		else
-		# normal makefile
-		KDIR ?= /lib/modules/`uname -r`/build
-
-		default:
-			$(MAKE) -C $(KDIR) M=$$PWD
-
-		# Module specific targets
-		genbin:
-			echo "X" > 8123_bin.o_shipped
-
-		endif
-
-	Here the "Kbuild" file is included from the makefile. This
-	allows an older version of kbuild, which only knows of
-	makefiles, to be used when the "make" and kbuild parts are
-	split into separate files.
-
---- 3.3 Binary Blobs
-
-	Some external modules need to include an object file as a blob.
-	kbuild has support for this, but requires the blob file to be
-	named <filename>_shipped. When the kbuild rules kick in, a copy
-	of <filename>_shipped is created with _shipped stripped off,
-	giving us <filename>. This shortened filename can be used in
-	the assignment to the module.
-
-	Throughout this section, 8123_bin.o_shipped has been used to
-	build the kernel module 8123.ko; it has been included as
-	8123_bin.o.
-
-		8123-y := 8123_if.o 8123_pci.o 8123_bin.o
-
-	Although there is no distinction between the ordinary source
-	files and the binary file, kbuild will pick up different rules
-	when creating the object file for the module.
-
---- 3.4 Building Multiple Modules
-
-	kbuild supports building multiple modules with a single build
-	file. For example, if you wanted to build two modules, foo.ko
-	and bar.ko, the kbuild lines would be:
-
-		obj-m := foo.o bar.o
-		foo-y := <foo_srcs>
-		bar-y := <bar_srcs>
-
-	It is that simple!
-
-
-=== 4. Include Files
-
-Within the kernel, header files are kept in standard locations
-according to the following rule:
-
-	* If the header file only describes the internal interface of a
-	  module, then the file is placed in the same directory as the
-	  source files.
-	* If the header file describes an interface used by other parts
-	  of the kernel that are located in different directories, then
-	  the file is placed in include/linux/.
-
-	  NOTE: There are two notable exceptions to this rule: larger
-	  subsystems have their own directory under include/, such as
-	  include/scsi; and architecture specific headers are located
-	  under arch/$(ARCH)/include/.
-
---- 4.1 Kernel Includes
-
-	To include a header file located under include/linux/, simply
-	use:
-
-		#include <linux/module.h>
-
-	kbuild will add options to "gcc" so the relevant directories
-	are searched.
-
---- 4.2 Single Subdirectory
-
-	External modules tend to place header files in a separate
-	include/ directory where their source is located, although this
-	is not the usual kernel style. To inform kbuild of the
-	directory, use either ccflags-y or CFLAGS_<filename>.o.
-
-	Using the example from section 3, if we moved 8123_if.h to a
-	subdirectory named include, the resulting kbuild file would
-	look like:
-
-		--> filename: Kbuild
-		obj-m := 8123.o
-
-		ccflags-y := -Iinclude
-		8123-y := 8123_if.o 8123_pci.o 8123_bin.o
-
-	Note that in the assignment there is no space between -I and
-	the path. This is a limitation of kbuild: there must be no
-	space present.
-
---- 4.3 Several Subdirectories
-
-	kbuild can handle files that are spread over several directories.
-	Consider the following example:
-
-	.
-	|__ src
-	|   |__ complex_main.c
-	|   |__ hal
-	|	|__ hardwareif.c
-	|	|__ include
-	|	    |__ hardwareif.h
-	|__ include
-	    |__ complex.h
-
-	To build the module complex.ko, we then need the following
-	kbuild file:
-
-		--> filename: Kbuild
-		obj-m := complex.o
-		complex-y := src/complex_main.o
-		complex-y += src/hal/hardwareif.o
-
-		ccflags-y := -I$(src)/include
-		ccflags-y += -I$(src)/src/hal/include
-
-	As you can see, kbuild knows how to handle object files located
-	in other directories. The trick is to specify the directory
-	relative to the kbuild file's location. That being said, this
-	is NOT recommended practice.
-
-	For the header files, kbuild must be explicitly told where to
-	look. When kbuild executes, the current directory is always the
-	root of the kernel tree (the argument to "-C") and therefore an
-	absolute path is needed. $(src) provides the absolute path by
-	pointing to the directory where the currently executing kbuild
-	file is located.
-
-
-=== 5. Module Installation
-
-Modules which are included in the kernel are installed in the
-directory:
-
-	/lib/modules/$(KERNELRELEASE)/kernel/
-
-And external modules are installed in:
-
-	/lib/modules/$(KERNELRELEASE)/extra/
-
---- 5.1 INSTALL_MOD_PATH
-
-	Above are the default directories but as always some level of
-	customization is possible. A prefix can be added to the
-	installation path using the variable INSTALL_MOD_PATH:
-
-		$ make INSTALL_MOD_PATH=/frodo modules_install
-		=> Install dir: /frodo/lib/modules/$(KERNELRELEASE)/kernel/
-
-	INSTALL_MOD_PATH may be set as an ordinary shell variable or,
-	as shown above, can be specified on the command line when
-	calling "make." This has effect when installing both in-tree
-	and out-of-tree modules.
-
---- 5.2 INSTALL_MOD_DIR
-
-	External modules are by default installed to a directory under
-	/lib/modules/$(KERNELRELEASE)/extra/, but you may wish to
-	locate modules for a specific functionality in a separate
-	directory. For this purpose, use INSTALL_MOD_DIR to specify an
-	alternative name to "extra."
-
-		$ make INSTALL_MOD_DIR=gandalf -C $KDIR \
-		       M=$PWD modules_install
-		=> Install dir: /lib/modules/$(KERNELRELEASE)/gandalf/
-
-
-=== 6. Module Versioning
-
-Module versioning is enabled by the CONFIG_MODVERSIONS tag, and is used
-as a simple ABI consistency check. A CRC value of the full prototype
-for an exported symbol is created. When a module is loaded/used, the
-CRC values contained in the kernel are compared with similar values in
-the module; if they are not equal, the kernel refuses to load the
-module.
-
-Module.symvers contains a list of all exported symbols from a kernel
-build.
-
---- 6.1 Symbols From the Kernel (vmlinux + modules)
-
-	During a kernel build, a file named Module.symvers will be
-	generated. Module.symvers contains all exported symbols from
-	the kernel and compiled modules. For each symbol, the
-	corresponding CRC value is also stored.
-
-	The syntax of the Module.symvers file is:
-		<CRC>	    <Symbol>	       <module>
-
-		0x2d036834  scsi_remove_host   drivers/scsi/scsi_mod
-
-	For a kernel build without CONFIG_MODVERSIONS enabled, the CRC
-	would read 0x00000000.
-
-	Module.symvers serves two purposes:
-	1) It lists all exported symbols from vmlinux and all modules.
-	2) It lists the CRC if CONFIG_MODVERSIONS is enabled.
-
---- 6.2 Symbols and External Modules
-
-	When building an external module, the build system needs access
-	to the symbols from the kernel to check if all external symbols
-	are defined. This is done in the MODPOST step. modpost obtains
-	the symbols by reading Module.symvers from the kernel source
-	tree. If a Module.symvers file is present in the directory
-	where the external module is being built, this file will be
-	read too. During the MODPOST step, a new Module.symvers file
-	will be written containing all exported symbols that were not
-	defined in the kernel.
-
---- 6.3 Symbols From Another External Module
-
-	Sometimes, an external module uses exported symbols from
-	another external module. kbuild needs to have full knowledge of
-	all symbols to avoid spitting out warnings about undefined
-	symbols. Three solutions exist for this situation.
-
-	NOTE: The method with a top-level kbuild file is recommended
-	but may be impractical in certain situations.
-
-	Use a top-level kbuild file
-		If you have two modules, foo.ko and bar.ko, where
-		foo.ko needs symbols from bar.ko, you can use a
-		common top-level kbuild file so both modules are
-		compiled in the same build. Consider the following
-		directory layout:
-
-		./foo/ <= contains foo.ko
-		./bar/ <= contains bar.ko
-
-		The top-level kbuild file would then look like:
-
-		#./Kbuild (or ./Makefile):
-			obj-y := foo/ bar/
-
-		And executing
-
-			$ make -C $KDIR M=$PWD
-
-		will then do the expected and compile both modules with
-		full knowledge of symbols from either module.
-
-	Use an extra Module.symvers file
-		When an external module is built, a Module.symvers file
-		is generated containing all exported symbols which are
-		not defined in the kernel. To get access to symbols
-		from bar.ko, copy the Module.symvers file from the
-		compilation of bar.ko to the directory where foo.ko is
-		built. During the module build, kbuild will read the
-		Module.symvers file in the directory of the external
-		module, and when the build is finished, a new
-		Module.symvers file is created containing the sum of
-		all symbols defined and not part of the kernel.
-
-	Use "make" variable KBUILD_EXTRA_SYMBOLS
-		If it is impractical to copy Module.symvers from
-		another module, you can assign a space separated list
-		of files to KBUILD_EXTRA_SYMBOLS in your build file.
-		These files will be loaded by modpost during the
-		initialization of its symbol tables.
-
-
-=== 7. Tips & Tricks
-
---- 7.1 Testing for CONFIG_FOO_BAR
-
-	Modules often need to check for certain CONFIG_ options to
-	decide if a specific feature is included in the module. In
-	kbuild this is done by referencing the CONFIG_ variable
-	directly.
-
-		#fs/ext2/Makefile
-		obj-$(CONFIG_EXT2_FS) += ext2.o
-
-		ext2-y := balloc.o bitmap.o dir.o
-		ext2-$(CONFIG_EXT2_FS_XATTR) += xattr.o
-
-	External modules have traditionally used "grep" to check for
-	specific CONFIG_ settings directly in .config. This usage is
-	broken. As introduced before, external modules should use
-	kbuild for building and can therefore use the same methods as
-	in-tree modules when testing for CONFIG_ definitions.
-
diff --git a/Documentation/kernel-hacking/hacking.rst b/Documentation/kernel-hacking/hacking.rst
index d824e4feaff3..5891a701a159 100644
--- a/Documentation/kernel-hacking/hacking.rst
+++ b/Documentation/kernel-hacking/hacking.rst
@@ -718,7 +718,7 @@ make a neat patch, there's administrative work to be done:
 -  Usually you want a configuration option for your kernel hack. Edit
    ``Kconfig`` in the appropriate directory. The Config language is
    simple to use by cut and paste, and there's complete documentation in
-   ``Documentation/kbuild/kconfig-language.txt``.
+   ``Documentation/kbuild/kconfig-language.rst``.
 
    In your description of the option, make sure you address both the
    expert user and the user who knows nothing about your feature.
@@ -728,7 +728,7 @@ make a neat patch, there's administrative work to be done:
 
 -  Edit the ``Makefile``: the CONFIG variables are exported here so you
    can usually just add a "obj-$(CONFIG_xxx) += xxx.o" line. The syntax
-   is documented in ``Documentation/kbuild/makefiles.txt``.
+   is documented in ``Documentation/kbuild/makefiles.rst``.
 
 -  Put yourself in ``CREDITS`` if you've done something noteworthy,
    usually beyond a single file (your name should be at the top of the
diff --git a/Documentation/process/coding-style.rst b/Documentation/process/coding-style.rst
index fa864a51e6ea..f4a2198187f9 100644
--- a/Documentation/process/coding-style.rst
+++ b/Documentation/process/coding-style.rst
@@ -686,7 +686,7 @@ filesystems) should advertise this prominently in their prompt string::
 	...
 
 For full documentation on the configuration files, see the file
-Documentation/kbuild/kconfig-language.txt.
+Documentation/kbuild/kconfig-language.rst.
 
 
 11) Data structures
diff --git a/Documentation/process/submit-checklist.rst b/Documentation/process/submit-checklist.rst
index c88867b173d9..365efc9e4aa8 100644
--- a/Documentation/process/submit-checklist.rst
+++ b/Documentation/process/submit-checklist.rst
@@ -39,7 +39,7 @@ and elsewhere regarding submitting Linux kernel patches.
 
 6) Any new or modified ``CONFIG`` options do not muck up the config menu and
    default to off unless they meet the exception criteria documented in
-   ``Documentation/kbuild/kconfig-language.txt`` Menu attributes: default value.
+   ``Documentation/kbuild/kconfig-language.rst`` Menu attributes: default value.
 
 7) All new ``Kconfig`` options have help text.
 
diff --git a/Documentation/translations/it_IT/kernel-hacking/hacking.rst b/Documentation/translations/it_IT/kernel-hacking/hacking.rst
index 7178e517af0a..24c592852bf1 100644
--- a/Documentation/translations/it_IT/kernel-hacking/hacking.rst
+++ b/Documentation/translations/it_IT/kernel-hacking/hacking.rst
@@ -755,7 +755,7 @@ anche per avere patch pulite, c'è del lavoro amministrativo da fare:
 -  Solitamente vorrete un'opzione di configurazione per la vostra modifica
    al kernel. Modificate ``Kconfig`` nella cartella giusta. Il linguaggio
    Config è facile con copia ed incolla, e c'è una completa documentazione
-   nel file ``Documentation/kbuild/kconfig-language.txt``.
+   nel file ``Documentation/kbuild/kconfig-language.rst``.
 
    Nella descrizione della vostra opzione, assicuratevi di parlare sia agli
    utenti esperti sia agli utente che non sanno nulla del vostro lavoro.
@@ -767,7 +767,7 @@ anche per avere patch pulite, c'è del lavoro amministrativo da fare:
 -  Modificate il file ``Makefile``: le variabili CONFIG sono esportate qui,
    quindi potete solitamente aggiungere una riga come la seguete
    "obj-$(CONFIG_xxx) += xxx.o". La sintassi è documentata nel file
-   ``Documentation/kbuild/makefiles.txt``.
+   ``Documentation/kbuild/makefiles.rst``.
 
 -  Aggiungete voi stessi in ``CREDITS`` se avete fatto qualcosa di notevole,
    solitamente qualcosa che supera il singolo file (comunque il vostro nome
diff --git a/Documentation/translations/it_IT/process/coding-style.rst b/Documentation/translations/it_IT/process/coding-style.rst
index a6559d25a23d..8995d2d19f20 100644
--- a/Documentation/translations/it_IT/process/coding-style.rst
+++ b/Documentation/translations/it_IT/process/coding-style.rst
@@ -696,7 +696,7 @@ nella stringa di titolo::
 	...
 
 Per la documentazione completa sui file di configurazione, consultate
-il documento Documentation/kbuild/kconfig-language.txt
+il documento Documentation/kbuild/kconfig-language.rst
 
 
 11) Strutture dati
diff --git a/Documentation/translations/it_IT/process/submit-checklist.rst b/Documentation/translations/it_IT/process/submit-checklist.rst
index 70e65a7b3620..ea74cae958d7 100644
--- a/Documentation/translations/it_IT/process/submit-checklist.rst
+++ b/Documentation/translations/it_IT/process/submit-checklist.rst
@@ -43,7 +43,7 @@ sottomissione delle patch, in particolare
 
 6) Le opzioni ``CONFIG``, nuove o modificate, non scombussolano il menu
    di configurazione e sono preimpostate come disabilitate a meno che non
-   soddisfino i criteri descritti in ``Documentation/kbuild/kconfig-language.txt``
+   soddisfino i criteri descritti in ``Documentation/kbuild/kconfig-language.rst``
    alla punto "Voci di menu: valori predefiniti".
 
 7) Tutte le nuove opzioni ``Kconfig`` hanno un messaggio di aiuto.
diff --git a/Documentation/translations/zh_CN/process/coding-style.rst b/Documentation/translations/zh_CN/process/coding-style.rst
index 5479c591c2f7..4f6237392e65 100644
--- a/Documentation/translations/zh_CN/process/coding-style.rst
+++ b/Documentation/translations/zh_CN/process/coding-style.rst
@@ -599,7 +599,7 @@ Documentation/doc-guide/ 和 scripts/kernel-doc 以获得详细信息。
 	depends on ADFS_FS
 	...
 
-要查看配置文件的完整文档，请看 Documentation/kbuild/kconfig-language.txt。
+要查看配置文件的完整文档，请看 Documentation/kbuild/kconfig-language.rst。
 
 
 11) 数据结构
diff --git a/Documentation/translations/zh_CN/process/submit-checklist.rst b/Documentation/translations/zh_CN/process/submit-checklist.rst
index 89061aa8fdbe..f4785d2b0491 100644
--- a/Documentation/translations/zh_CN/process/submit-checklist.rst
+++ b/Documentation/translations/zh_CN/process/submit-checklist.rst
@@ -38,7 +38,7 @@ Linux内核补丁提交清单
    违规行为。
 
 6) 任何新的或修改过的 ``CONFIG`` 选项都不会弄脏配置菜单，并默认为关闭，除非
-   它们符合 ``Documentation/kbuild/kconfig-language.txt`` 中记录的异常条件,
+   它们符合 ``Documentation/kbuild/kconfig-language.rst`` 中记录的异常条件,
    菜单属性：默认值.
 
 7) 所有新的 ``kconfig`` 选项都有帮助文本。
diff --git a/Kconfig b/Kconfig
index 990b0c390dfc..e10b3ee084d4 100644
--- a/Kconfig
+++ b/Kconfig
@@ -1,7 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0
 #
 # For a description of the syntax of this configuration file,
-# see Documentation/kbuild/kconfig-language.txt.
+# see Documentation/kbuild/kconfig-language.rst.
 #
 mainmenu "Linux/$(ARCH) $(KERNELVERSION) Kernel Configuration"
 
diff --git a/arch/arc/plat-eznps/Kconfig b/arch/arc/plat-eznps/Kconfig
index 2eaecfb063a7..a376a50d3fea 100644
--- a/arch/arc/plat-eznps/Kconfig
+++ b/arch/arc/plat-eznps/Kconfig
@@ -1,7 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0
 #
 # For a description of the syntax of this configuration file,
-# see Documentation/kbuild/kconfig-language.txt.
+# see Documentation/kbuild/kconfig-language.rst.
 #
 
 menuconfig ARC_PLAT_EZNPS
diff --git a/arch/c6x/Kconfig b/arch/c6x/Kconfig
index eeb0471268a0..c5e6b70e1510 100644
--- a/arch/c6x/Kconfig
+++ b/arch/c6x/Kconfig
@@ -1,7 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0
 #
 # For a description of the syntax of this configuration file,
-# see Documentation/kbuild/kconfig-language.txt.
+# see Documentation/kbuild/kconfig-language.rst.
 #
 
 config C6X
diff --git a/arch/microblaze/Kconfig.debug b/arch/microblaze/Kconfig.debug
index 3a343188d86c..865527ac332a 100644
--- a/arch/microblaze/Kconfig.debug
+++ b/arch/microblaze/Kconfig.debug
@@ -1,6 +1,6 @@
 # SPDX-License-Identifier: GPL-2.0-only
 # For a description of the syntax of this configuration file,
-# see Documentation/kbuild/kconfig-language.txt.
+# see Documentation/kbuild/kconfig-language.rst.
 
 config TRACE_IRQFLAGS_SUPPORT
 	def_bool y
diff --git a/arch/microblaze/Kconfig.platform b/arch/microblaze/Kconfig.platform
index 5bf54c1d4f60..7795f90dad86 100644
--- a/arch/microblaze/Kconfig.platform
+++ b/arch/microblaze/Kconfig.platform
@@ -1,6 +1,6 @@
 # SPDX-License-Identifier: GPL-2.0-only
 # For a description of the syntax of this configuration file,
-# see Documentation/kbuild/kconfig-language.txt.
+# see Documentation/kbuild/kconfig-language.rst.
 #
 # Platform selection Kconfig menu for MicroBlaze targets
 #
diff --git a/arch/nds32/Kconfig b/arch/nds32/Kconfig
index 3299e287a477..fd0d0639454f 100644
--- a/arch/nds32/Kconfig
+++ b/arch/nds32/Kconfig
@@ -1,7 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0-only
 #
 # For a description of the syntax of this configuration file,
-# see Documentation/kbuild/kconfig-language.txt.
+# see Documentation/kbuild/kconfig-language.rst.
 #
 
 config NDS32
diff --git a/arch/openrisc/Kconfig b/arch/openrisc/Kconfig
index 7cfb20555b10..bf326f0edd2f 100644
--- a/arch/openrisc/Kconfig
+++ b/arch/openrisc/Kconfig
@@ -1,7 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0
 #
 # For a description of the syntax of this configuration file,
-# see Documentation/kbuild/kconfig-language.txt.
+# see Documentation/kbuild/kconfig-language.rst.
 #
 
 config OPENRISC
diff --git a/arch/powerpc/sysdev/Kconfig b/arch/powerpc/sysdev/Kconfig
index e0dbec780fe9..d23288c4abf6 100644
--- a/arch/powerpc/sysdev/Kconfig
+++ b/arch/powerpc/sysdev/Kconfig
@@ -1,6 +1,6 @@
 # SPDX-License-Identifier: GPL-2.0
 # For a description of the syntax of this configuration file,
-# see Documentation/kbuild/kconfig-language.txt.
+# see Documentation/kbuild/kconfig-language.rst.
 #
 
 config PPC4xx_PCI_EXPRESS
diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 0c4b12205632..be713da93946 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -1,7 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0-only
 #
 # For a description of the syntax of this configuration file,
-# see Documentation/kbuild/kconfig-language.txt.
+# see Documentation/kbuild/kconfig-language.rst.
 #
 
 config 64BIT
diff --git a/drivers/auxdisplay/Kconfig b/drivers/auxdisplay/Kconfig
index c52c738e554a..dd61fdd400f0 100644
--- a/drivers/auxdisplay/Kconfig
+++ b/drivers/auxdisplay/Kconfig
@@ -1,7 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0
 #
 # For a description of the syntax of this configuration file,
-# see Documentation/kbuild/kconfig-language.txt.
+# see Documentation/kbuild/kconfig-language.rst.
 #
 # Auxiliary display drivers configuration.
 #
diff --git a/drivers/firmware/Kconfig b/drivers/firmware/Kconfig
index 9026df923542..35078c6f334a 100644
--- a/drivers/firmware/Kconfig
+++ b/drivers/firmware/Kconfig
@@ -1,7 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0-only
 #
 # For a description of the syntax of this configuration file,
-# see Documentation/kbuild/kconfig-language.txt.
+# see Documentation/kbuild/kconfig-language.rst.
 #
 
 menu "Firmware Drivers"
diff --git a/drivers/mtd/devices/Kconfig b/drivers/mtd/devices/Kconfig
index ef0e476b2525..49abbc52457d 100644
--- a/drivers/mtd/devices/Kconfig
+++ b/drivers/mtd/devices/Kconfig
@@ -48,7 +48,7 @@ config MTD_MS02NV
 
 	  If you want to compile this driver as a module ( = code which can be
 	  inserted in and removed from the running kernel whenever you want),
-	  say M here and read <file:Documentation/kbuild/modules.txt>.
+	  say M here and read <file:Documentation/kbuild/modules.rst>.
 	  The module will be called ms02-nv.
 
 config MTD_DATAFLASH
diff --git a/drivers/net/ethernet/smsc/Kconfig b/drivers/net/ethernet/smsc/Kconfig
index d1b6a78557ec..9e1c3752b200 100644
--- a/drivers/net/ethernet/smsc/Kconfig
+++ b/drivers/net/ethernet/smsc/Kconfig
@@ -49,7 +49,7 @@ config SMC91X
 	  This driver is also available as a module ( = code which can be
 	  inserted in and removed from the running kernel whenever you want).
 	  The module will be called smc91x.  If you want to compile it as a
-	  module, say M here and read <file:Documentation/kbuild/modules.txt>.
+	  module, say M here and read <file:Documentation/kbuild/modules.rst>.
 
 config PCMCIA_SMC91C92
 	tristate "SMC 91Cxx PCMCIA support"
@@ -86,7 +86,7 @@ config SMC911X
 
 	  This driver is also available as a module. The module will be
 	  called smc911x.  If you want to compile it as a module, say M
-	  here and read <file:Documentation/kbuild/modules.txt>
+	  here and read <file:Documentation/kbuild/modules.rst>
 
 config SMSC911X
 	tristate "SMSC LAN911x/LAN921x families embedded ethernet support"
@@ -121,6 +121,6 @@ config SMSC9420
 
 	  This driver is also available as a module. The module will be
 	  called smsc9420.  If you want to compile it as a module, say M
-	  here and read <file:Documentation/kbuild/modules.txt>
+	  here and read <file:Documentation/kbuild/modules.rst>
 
 endif # NET_VENDOR_SMSC
diff --git a/drivers/net/wireless/intel/iwlegacy/Kconfig b/drivers/net/wireless/intel/iwlegacy/Kconfig
index aa01c83e0060..e329fd7b09c0 100644
--- a/drivers/net/wireless/intel/iwlegacy/Kconfig
+++ b/drivers/net/wireless/intel/iwlegacy/Kconfig
@@ -32,7 +32,7 @@ config IWL4965
 
 	  If you want to compile the driver as a module ( = code which can be
 	  inserted in and removed from the running kernel whenever you want),
-	  say M here and read <file:Documentation/kbuild/modules.txt>.  The
+	  say M here and read <file:Documentation/kbuild/modules.rst>.  The
 	  module will be called iwl4965.
 
 config IWL3945
@@ -58,7 +58,7 @@ config IWL3945
 
 	  If you want to compile the driver as a module ( = code which can be
 	  inserted in and removed from the running kernel whenever you want),
-	  say M here and read <file:Documentation/kbuild/modules.txt>.  The
+	  say M here and read <file:Documentation/kbuild/modules.rst>.  The
 	  module will be called iwl3945.
 
 menu "iwl3945 / iwl4965 Debugging Options"
diff --git a/drivers/net/wireless/intel/iwlwifi/Kconfig b/drivers/net/wireless/intel/iwlwifi/Kconfig
index e5528189163f..235349a33a3c 100644
--- a/drivers/net/wireless/intel/iwlwifi/Kconfig
+++ b/drivers/net/wireless/intel/iwlwifi/Kconfig
@@ -40,7 +40,7 @@ config IWLWIFI
 
 	  If you want to compile the driver as a module ( = code which can be
 	  inserted in and removed from the running kernel whenever you want),
-	  say M here and read <file:Documentation/kbuild/modules.txt>.  The
+	  say M here and read <file:Documentation/kbuild/modules.rst>.  The
 	  module will be called iwlwifi.
 
 if IWLWIFI
diff --git a/drivers/parport/Kconfig b/drivers/parport/Kconfig
index 24189c3399e0..1791830e7a71 100644
--- a/drivers/parport/Kconfig
+++ b/drivers/parport/Kconfig
@@ -1,7 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0-only
 #
 # For a description of the syntax of this configuration file,
-# see Documentation/kbuild/kconfig-language.txt.
+# see Documentation/kbuild/kconfig-language.rst.
 #
 # Parport configuration.
 #
diff --git a/drivers/scsi/Kconfig b/drivers/scsi/Kconfig
index 61da513fc0ed..f31b6b780eaf 100644
--- a/drivers/scsi/Kconfig
+++ b/drivers/scsi/Kconfig
@@ -183,7 +183,7 @@ config CHR_DEV_SCH
 	
 	  If you want to compile this as a module ( = code which can be
 	  inserted in and removed from the running kernel whenever you want),
-	  say M here and read <file:Documentation/kbuild/modules.txt> and
+	  say M here and read <file:Documentation/kbuild/modules.rst> and
 	  <file:Documentation/scsi/scsi.txt>. The module will be called ch.o.
 	  If unsure, say N.
 
@@ -1474,7 +1474,7 @@ config ZFCP
 
           This driver is also available as a module. This module will be
           called zfcp. If you want to compile it as a module, say M here
-          and read <file:Documentation/kbuild/modules.txt>.
+          and read <file:Documentation/kbuild/modules.rst>.
 
 config SCSI_PMCRAID
 	tristate "PMC SIERRA Linux MaxRAID adapter support"
diff --git a/drivers/staging/sm750fb/Kconfig b/drivers/staging/sm750fb/Kconfig
index fb5a086bf9b1..8c0d8a873d5b 100644
--- a/drivers/staging/sm750fb/Kconfig
+++ b/drivers/staging/sm750fb/Kconfig
@@ -12,4 +12,4 @@ config FB_SM750
 
 	  This driver is also available as a module. The module will be
 	  called sm750fb. If you want to compile it as a module, say M
-	  here and read <file:Documentation/kbuild/modules.txt>.
+	  here and read <file:Documentation/kbuild/modules.rst>.
diff --git a/drivers/usb/misc/Kconfig b/drivers/usb/misc/Kconfig
index c97f270338bf..4a88e1ca25c0 100644
--- a/drivers/usb/misc/Kconfig
+++ b/drivers/usb/misc/Kconfig
@@ -16,7 +16,7 @@ config USB_EMI62
 	  This code is also available as a module ( = code which can be
 	  inserted in and removed from the running kernel whenever you want).
 	  The module will be called audio. If you want to compile it as a
-	  module, say M here and read <file:Documentation/kbuild/modules.txt>.
+	  module, say M here and read <file:Documentation/kbuild/modules.rst>.
 
 config USB_EMI26
 	tristate "EMI 2|6 USB Audio interface support"
@@ -67,7 +67,7 @@ config USB_LEGOTOWER
 	  inserted in and removed from the running kernel whenever you want).
 	  The module will be called legousbtower. If you want to compile it as
 	  a module, say M here and read
-	  <file:Documentation/kbuild/modules.txt>.
+	  <file:Documentation/kbuild/modules.rst>.
 
 config USB_LCD
 	tristate "USB LCD driver support"
diff --git a/drivers/video/fbdev/Kconfig b/drivers/video/fbdev/Kconfig
index 737b86328c9e..31ba91cb916a 100644
--- a/drivers/video/fbdev/Kconfig
+++ b/drivers/video/fbdev/Kconfig
@@ -289,7 +289,7 @@ config FB_ARMCLCD
 
 	  If you want to compile this as a module (=code which can be
 	  inserted into and removed from the running kernel), say M
-	  here and read <file:Documentation/kbuild/modules.txt>.  The module
+	  here and read <file:Documentation/kbuild/modules.rst>.  The module
 	  will be called amba-clcd.
 
 config FB_ACORN
@@ -1752,7 +1752,7 @@ config FB_PXA
 	  This driver is also available as a module ( = code which can be
 	  inserted and removed from the running kernel whenever you want). The
 	  module will be called pxafb. If you want to compile it as a module,
-	  say M here and read <file:Documentation/kbuild/modules.txt>.
+	  say M here and read <file:Documentation/kbuild/modules.rst>.
 
 	  If unsure, say N.
 
@@ -1833,7 +1833,7 @@ config FB_W100
 	  This driver is also available as a module ( = code which can be
 	  inserted and removed from the running kernel whenever you want). The
 	  module will be called w100fb. If you want to compile it as a module,
-	  say M here and read <file:Documentation/kbuild/modules.txt>.
+	  say M here and read <file:Documentation/kbuild/modules.rst>.
 
 	  If unsure, say N.
 
@@ -1862,7 +1862,7 @@ config FB_TMIO
 	  This driver is also available as a module ( = code which can be
 	  inserted and removed from the running kernel whenever you want). The
 	  module will be called tmiofb. If you want to compile it as a module,
-	  say M here and read <file:Documentation/kbuild/modules.txt>.
+	  say M here and read <file:Documentation/kbuild/modules.rst>.
 
 	  If unsure, say N.
 
@@ -1908,7 +1908,7 @@ config FB_S3C2410
 	  This driver is also available as a module ( = code which can be
 	  inserted and removed from the running kernel whenever you want). The
 	  module will be called s3c2410fb. If you want to compile it as a module,
-	  say M here and read <file:Documentation/kbuild/modules.txt>.
+	  say M here and read <file:Documentation/kbuild/modules.rst>.
 
 	  If unsure, say N.
 config FB_S3C2410_DEBUG
@@ -1945,7 +1945,7 @@ config FB_SM501
 	  This driver is also available as a module ( = code which can be
 	  inserted and removed from the running kernel whenever you want). The
 	  module will be called sm501fb. If you want to compile it as a module,
-	  say M here and read <file:Documentation/kbuild/modules.txt>.
+	  say M here and read <file:Documentation/kbuild/modules.rst>.
 
 	  If unsure, say N.
 
@@ -2288,7 +2288,7 @@ config FB_SM712
 
 	  This driver is also available as a module. The module will be
 	  called sm712fb. If you want to compile it as a module, say M
-	  here and read <file:Documentation/kbuild/modules.txt>.
+	  here and read <file:Documentation/kbuild/modules.rst>.
 
 source "drivers/video/fbdev/omap/Kconfig"
 source "drivers/video/fbdev/omap2/Kconfig"
diff --git a/net/bridge/netfilter/Kconfig b/net/bridge/netfilter/Kconfig
index c3ad90c43801..36a98d36d339 100644
--- a/net/bridge/netfilter/Kconfig
+++ b/net/bridge/netfilter/Kconfig
@@ -114,7 +114,7 @@ config BRIDGE_EBT_LIMIT
 	  equivalent of the iptables limit match.
 
 	  If you want to compile it as a module, say M here and read
-	  <file:Documentation/kbuild/modules.txt>.  If unsure, say `N'.
+	  <file:Documentation/kbuild/modules.rst>.  If unsure, say `N'.
 
 config BRIDGE_EBT_MARK
 	tristate "ebt: mark filter support"
diff --git a/net/ipv4/netfilter/Kconfig b/net/ipv4/netfilter/Kconfig
index 3e6494269501..69e76d677f9e 100644
--- a/net/ipv4/netfilter/Kconfig
+++ b/net/ipv4/netfilter/Kconfig
@@ -308,7 +308,7 @@ config IP_NF_RAW
 	  and OUTPUT chains.
 	
 	  If you want to compile it as a module, say M here and read
-	  <file:Documentation/kbuild/modules.txt>.  If unsure, say `N'.
+	  <file:Documentation/kbuild/modules.rst>.  If unsure, say `N'.
 
 # security table for MAC policy
 config IP_NF_SECURITY
diff --git a/net/ipv6/netfilter/Kconfig b/net/ipv6/netfilter/Kconfig
index f7c6f5be9f76..6120a7800975 100644
--- a/net/ipv6/netfilter/Kconfig
+++ b/net/ipv6/netfilter/Kconfig
@@ -241,7 +241,7 @@ config IP6_NF_RAW
 	  and OUTPUT chains.
 
 	  If you want to compile it as a module, say M here and read
-	  <file:Documentation/kbuild/modules.txt>.  If unsure, say `N'.
+	  <file:Documentation/kbuild/modules.rst>.  If unsure, say `N'.
 
 # security table for MAC policy
 config IP6_NF_SECURITY
diff --git a/net/netfilter/Kconfig b/net/netfilter/Kconfig
index 21025c2c605b..dd2af7be3eea 100644
--- a/net/netfilter/Kconfig
+++ b/net/netfilter/Kconfig
@@ -1056,7 +1056,7 @@ config NETFILTER_XT_TARGET_TRACE
 	  the tables, chains, rules.
 
 	  If you want to compile it as a module, say M here and read
-	  <file:Documentation/kbuild/modules.txt>.  If unsure, say `N'.
+	  <file:Documentation/kbuild/modules.rst>.  If unsure, say `N'.
 
 config NETFILTER_XT_TARGET_SECMARK
 	tristate '"SECMARK" target support'
@@ -1115,7 +1115,7 @@ config NETFILTER_XT_MATCH_ADDRTYPE
 	  eg. UNICAST, LOCAL, BROADCAST, ...
 
 	  If you want to compile it as a module, say M here and read
-	  <file:Documentation/kbuild/modules.txt>.  If unsure, say `N'.
+	  <file:Documentation/kbuild/modules.rst>.  If unsure, say `N'.
 
 config NETFILTER_XT_MATCH_BPF
 	tristate '"bpf" match support'
@@ -1160,7 +1160,7 @@ config NETFILTER_XT_MATCH_COMMENT
 	  comments in your iptables ruleset.
 
 	  If you want to compile it as a module, say M here and read
-	  <file:Documentation/kbuild/modules.txt>.  If unsure, say `N'.
+	  <file:Documentation/kbuild/modules.rst>.  If unsure, say `N'.
 
 config NETFILTER_XT_MATCH_CONNBYTES
 	tristate  '"connbytes" per-connection counter match support'
@@ -1171,7 +1171,7 @@ config NETFILTER_XT_MATCH_CONNBYTES
 	  number of bytes and/or packets for each direction within a connection.
 
 	  If you want to compile it as a module, say M here and read
-	  <file:Documentation/kbuild/modules.txt>.  If unsure, say `N'.
+	  <file:Documentation/kbuild/modules.rst>.  If unsure, say `N'.
 
 config NETFILTER_XT_MATCH_CONNLABEL
 	tristate '"connlabel" match support'
@@ -1237,7 +1237,7 @@ config NETFILTER_XT_MATCH_DCCP
 	  and DCCP flags.
 
 	  If you want to compile it as a module, say M here and read
-	  <file:Documentation/kbuild/modules.txt>.  If unsure, say `N'.
+	  <file:Documentation/kbuild/modules.rst>.  If unsure, say `N'.
 
 config NETFILTER_XT_MATCH_DEVGROUP
 	tristate '"devgroup" match support'
@@ -1473,7 +1473,7 @@ config NETFILTER_XT_MATCH_QUOTA
 	  byte counter.
 
 	  If you want to compile it as a module, say M here and read
-	  <file:Documentation/kbuild/modules.txt>.  If unsure, say `N'.
+	  <file:Documentation/kbuild/modules.rst>.  If unsure, say `N'.
 
 config NETFILTER_XT_MATCH_RATEEST
 	tristate '"rateest" match support'
@@ -1497,7 +1497,7 @@ config NETFILTER_XT_MATCH_REALM
 	  in tc world.
 
 	  If you want to compile it as a module, say M here and read
-	  <file:Documentation/kbuild/modules.txt>.  If unsure, say `N'.
+	  <file:Documentation/kbuild/modules.rst>.  If unsure, say `N'.
 
 config NETFILTER_XT_MATCH_RECENT
 	tristate '"recent" match support'
@@ -1519,7 +1519,7 @@ config NETFILTER_XT_MATCH_SCTP
 	  and SCTP chunk types.
 
 	  If you want to compile it as a module, say M here and read
-	  <file:Documentation/kbuild/modules.txt>.  If unsure, say `N'.
+	  <file:Documentation/kbuild/modules.rst>.  If unsure, say `N'.
 
 config NETFILTER_XT_MATCH_SOCKET
 	tristate '"socket" match support'
diff --git a/net/tipc/Kconfig b/net/tipc/Kconfig
index b93bb7bdb04a..b83e16ade4d2 100644
--- a/net/tipc/Kconfig
+++ b/net/tipc/Kconfig
@@ -17,7 +17,7 @@ menuconfig TIPC
 	  This protocol support is also available as a module ( = code which
 	  can be inserted in and removed from the running kernel whenever you
 	  want). The module will be called tipc. If you want to compile it
-	  as a module, say M here and read <file:Documentation/kbuild/modules.txt>.
+	  as a module, say M here and read <file:Documentation/kbuild/modules.rst>.
 
 	  If in doubt, say N.
 
diff --git a/scripts/Kbuild.include b/scripts/Kbuild.include
index f641bb0aa63f..ee58cde8ee3b 100644
--- a/scripts/Kbuild.include
+++ b/scripts/Kbuild.include
@@ -68,7 +68,7 @@ endef
 
 ######
 # gcc support functions
-# See documentation in Documentation/kbuild/makefiles.txt
+# See documentation in Documentation/kbuild/makefiles.rst
 
 # cc-cross-prefix
 # Usage: CROSS_COMPILE := $(call cc-cross-prefix, m68k-linux-gnu- m68k-linux-)
@@ -210,7 +210,7 @@ objectify = $(foreach o,$(1),$(if $(filter /%,$(o)),$(o),$(obj)/$(o)))
 # if_changed_dep  - as if_changed, but uses fixdep to reveal dependencies
 #                   including used config symbols
 # if_changed_rule - as if_changed but execute rule instead
-# See Documentation/kbuild/makefiles.txt for more info
+# See Documentation/kbuild/makefiles.rst for more info
 
 ifneq ($(KBUILD_NOCMDDEP),1)
 # Check if both arguments are the same including their order. Result is empty
diff --git a/scripts/Makefile.host b/scripts/Makefile.host
index b6a54bdf0965..a316d368b697 100644
--- a/scripts/Makefile.host
+++ b/scripts/Makefile.host
@@ -6,7 +6,7 @@
 #
 # Both C and C++ are supported, but preferred language is C for such utilities.
 #
-# Sample syntax (see Documentation/kbuild/makefiles.txt for reference)
+# Sample syntax (see Documentation/kbuild/makefiles.rst for reference)
 # hostprogs-y := bin2hex
 # Will compile bin2hex.c and create an executable named bin2hex
 #
diff --git a/scripts/kconfig/symbol.c b/scripts/kconfig/symbol.c
index 1f9266dadedf..09fd6fa18e1a 100644
--- a/scripts/kconfig/symbol.c
+++ b/scripts/kconfig/symbol.c
@@ -1114,7 +1114,7 @@ static void sym_check_print_recursive(struct symbol *last_sym)
 	}
 
 	fprintf(stderr,
-		"For a resolution refer to Documentation/kbuild/kconfig-language.txt\n"
+		"For a resolution refer to Documentation/kbuild/kconfig-language.rst\n"
 		"subsection \"Kconfig recursive dependency limitations\"\n"
 		"\n");
 
diff --git a/scripts/kconfig/tests/err_recursive_dep/expected_stderr b/scripts/kconfig/tests/err_recursive_dep/expected_stderr
index 84679b104655..c9f4abf9a791 100644
--- a/scripts/kconfig/tests/err_recursive_dep/expected_stderr
+++ b/scripts/kconfig/tests/err_recursive_dep/expected_stderr
@@ -1,38 +1,38 @@
 Kconfig:11:error: recursive dependency detected!
 Kconfig:11:	symbol B is selected by B
-For a resolution refer to Documentation/kbuild/kconfig-language.txt
+For a resolution refer to Documentation/kbuild/kconfig-language.rst
 subsection "Kconfig recursive dependency limitations"
 
 Kconfig:5:error: recursive dependency detected!
 Kconfig:5:	symbol A depends on A
-For a resolution refer to Documentation/kbuild/kconfig-language.txt
+For a resolution refer to Documentation/kbuild/kconfig-language.rst
 subsection "Kconfig recursive dependency limitations"
 
 Kconfig:17:error: recursive dependency detected!
 Kconfig:17:	symbol C1 depends on C2
 Kconfig:21:	symbol C2 depends on C1
-For a resolution refer to Documentation/kbuild/kconfig-language.txt
+For a resolution refer to Documentation/kbuild/kconfig-language.rst
 subsection "Kconfig recursive dependency limitations"
 
 Kconfig:32:error: recursive dependency detected!
 Kconfig:32:	symbol D2 is selected by D1
 Kconfig:27:	symbol D1 depends on D2
-For a resolution refer to Documentation/kbuild/kconfig-language.txt
+For a resolution refer to Documentation/kbuild/kconfig-language.rst
 subsection "Kconfig recursive dependency limitations"
 
 Kconfig:37:error: recursive dependency detected!
 Kconfig:37:	symbol E1 depends on E2
 Kconfig:42:	symbol E2 is implied by E1
-For a resolution refer to Documentation/kbuild/kconfig-language.txt
+For a resolution refer to Documentation/kbuild/kconfig-language.rst
 subsection "Kconfig recursive dependency limitations"
 
 Kconfig:60:error: recursive dependency detected!
 Kconfig:60:	symbol G depends on G
-For a resolution refer to Documentation/kbuild/kconfig-language.txt
+For a resolution refer to Documentation/kbuild/kconfig-language.rst
 subsection "Kconfig recursive dependency limitations"
 
 Kconfig:51:error: recursive dependency detected!
 Kconfig:51:	symbol F2 depends on F1
 Kconfig:49:	symbol F1 default value contains F2
-For a resolution refer to Documentation/kbuild/kconfig-language.txt
+For a resolution refer to Documentation/kbuild/kconfig-language.rst
 subsection "Kconfig recursive dependency limitations"
diff --git a/sound/oss/dmasound/Kconfig b/sound/oss/dmasound/Kconfig
index 12e42165b4a5..1a3339859840 100644
--- a/sound/oss/dmasound/Kconfig
+++ b/sound/oss/dmasound/Kconfig
@@ -11,7 +11,7 @@ config DMASOUND_ATARI
 	  This driver is also available as a module ( = code which can be
 	  inserted in and removed from the running kernel whenever you
 	  want). If you want to compile it as a module, say M here and read
-	  <file:Documentation/kbuild/modules.txt>.
+	  <file:Documentation/kbuild/modules.rst>.
 
 config DMASOUND_PAULA
 	tristate "Amiga DMA sound support"
@@ -25,7 +25,7 @@ config DMASOUND_PAULA
 	  This driver is also available as a module ( = code which can be
 	  inserted in and removed from the running kernel whenever you
 	  want). If you want to compile it as a module, say M here and read
-	  <file:Documentation/kbuild/modules.txt>.
+	  <file:Documentation/kbuild/modules.rst>.
 
 config DMASOUND_Q40
 	tristate "Q40 sound support"
@@ -39,7 +39,7 @@ config DMASOUND_Q40
 	  This driver is also available as a module ( = code which can be
 	  inserted in and removed from the running kernel whenever you
 	  want). If you want to compile it as a module, say M here and read
-	  <file:Documentation/kbuild/modules.txt>.
+	  <file:Documentation/kbuild/modules.rst>.
 
 config DMASOUND
 	tristate
-- 
cgit v1.2.3


From 4ca9bc225e46eb7bc040dd948be7cb68975d80d3 Mon Sep 17 00:00:00 2001
From: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Date: Wed, 12 Jun 2019 14:52:59 -0300
Subject: docs: target: convert docs to ReST and rename to *.rst

Convert the TCM docs to ReST format and add them to the
bookset.

This has a mix of userspace-faced and Kernelspace faced
docs. Still, it sounds a better candidate to be added at
the kernel API set of docs.

The conversion is actually:
  - add blank lines and identation in order to identify paragraphs;
  - fix tables markups;
  - add some lists markups;
  - mark literal blocks;
  - adjust title markups.

At its new index.rst, let's add a :orphan: while this is not linked to
the main index.rst file, in order to avoid build warnings.

Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
---
 Documentation/target/index.rst           |  19 ++
 Documentation/target/scripts.rst         |  11 +
 Documentation/target/tcm_mod_builder.rst | 149 ++++++++++++
 Documentation/target/tcm_mod_builder.txt | 145 -----------
 Documentation/target/tcmu-design.rst     | 405 +++++++++++++++++++++++++++++++
 Documentation/target/tcmu-design.txt     | 381 -----------------------------
 scripts/documentation-file-ref-check     |   2 +-
 7 files changed, 585 insertions(+), 527 deletions(-)
 create mode 100644 Documentation/target/index.rst
 create mode 100644 Documentation/target/scripts.rst
 create mode 100644 Documentation/target/tcm_mod_builder.rst
 delete mode 100644 Documentation/target/tcm_mod_builder.txt
 create mode 100644 Documentation/target/tcmu-design.rst
 delete mode 100644 Documentation/target/tcmu-design.txt

(limited to 'scripts')

diff --git a/Documentation/target/index.rst b/Documentation/target/index.rst
new file mode 100644
index 000000000000..b68f48982392
--- /dev/null
+++ b/Documentation/target/index.rst
@@ -0,0 +1,19 @@
+:orphan:
+
+==================
+TCM Virtual Device
+==================
+
+.. toctree::
+    :maxdepth: 1
+
+    tcmu-design
+    tcm_mod_builder
+    scripts
+
+.. only::  subproject and html
+
+   Indices
+   =======
+
+   * :ref:`genindex`
diff --git a/Documentation/target/scripts.rst b/Documentation/target/scripts.rst
new file mode 100644
index 000000000000..172d42b522e4
--- /dev/null
+++ b/Documentation/target/scripts.rst
@@ -0,0 +1,11 @@
+TCM mod builder script
+----------------------
+
+.. literalinclude:: tcm_mod_builder.py
+    :language: perl
+
+Target export device script
+---------------------------
+
+.. literalinclude:: target-export-device
+    :language: shell
diff --git a/Documentation/target/tcm_mod_builder.rst b/Documentation/target/tcm_mod_builder.rst
new file mode 100644
index 000000000000..9bfc9822e2bd
--- /dev/null
+++ b/Documentation/target/tcm_mod_builder.rst
@@ -0,0 +1,149 @@
+=========================================
+The TCM v4 fabric module script generator
+=========================================
+
+Greetings all,
+
+This document is intended to be a mini-HOWTO for using the tcm_mod_builder.py
+script to generate a brand new functional TCM v4 fabric .ko module of your very own,
+that once built can be immediately be loaded to start access the new TCM/ConfigFS
+fabric skeleton, by simply using::
+
+	modprobe $TCM_NEW_MOD
+	mkdir -p /sys/kernel/config/target/$TCM_NEW_MOD
+
+This script will create a new drivers/target/$TCM_NEW_MOD/, and will do the following
+
+	1) Generate new API callers for drivers/target/target_core_fabric_configs.c logic
+	   ->make_tpg(), ->drop_tpg(), ->make_wwn(), ->drop_wwn().  These are created
+	   into $TCM_NEW_MOD/$TCM_NEW_MOD_configfs.c
+	2) Generate basic infrastructure for loading/unloading LKMs and TCM/ConfigFS fabric module
+	   using a skeleton struct target_core_fabric_ops API template.
+	3) Based on user defined T10 Proto_Ident for the new fabric module being built,
+	   the TransportID / Initiator and Target WWPN related handlers for
+	   SPC-3 persistent reservation are automatically generated in $TCM_NEW_MOD/$TCM_NEW_MOD_fabric.c
+	   using drivers/target/target_core_fabric_lib.c logic.
+	4) NOP API calls for all other Data I/O path and fabric dependent attribute logic
+	   in $TCM_NEW_MOD/$TCM_NEW_MOD_fabric.c
+
+tcm_mod_builder.py depends upon the mandatory '-p $PROTO_IDENT' and '-m
+$FABRIC_MOD_name' parameters, and actually running the script looks like::
+
+  target:/mnt/sdb/lio-core-2.6.git/Documentation/target# python tcm_mod_builder.py -p iSCSI -m tcm_nab5000
+  tcm_dir: /mnt/sdb/lio-core-2.6.git/Documentation/target/../../
+  Set fabric_mod_name: tcm_nab5000
+  Set fabric_mod_dir:
+  /mnt/sdb/lio-core-2.6.git/Documentation/target/../../drivers/target/tcm_nab5000
+  Using proto_ident: iSCSI
+  Creating fabric_mod_dir:
+  /mnt/sdb/lio-core-2.6.git/Documentation/target/../../drivers/target/tcm_nab5000
+  Writing file:
+  /mnt/sdb/lio-core-2.6.git/Documentation/target/../../drivers/target/tcm_nab5000/tcm_nab5000_base.h
+  Using tcm_mod_scan_fabric_ops:
+  /mnt/sdb/lio-core-2.6.git/Documentation/target/../../include/target/target_core_fabric_ops.h
+  Writing file:
+  /mnt/sdb/lio-core-2.6.git/Documentation/target/../../drivers/target/tcm_nab5000/tcm_nab5000_fabric.c
+  Writing file:
+  /mnt/sdb/lio-core-2.6.git/Documentation/target/../../drivers/target/tcm_nab5000/tcm_nab5000_fabric.h
+  Writing file:
+  /mnt/sdb/lio-core-2.6.git/Documentation/target/../../drivers/target/tcm_nab5000/tcm_nab5000_configfs.c
+  Writing file:
+  /mnt/sdb/lio-core-2.6.git/Documentation/target/../../drivers/target/tcm_nab5000/Kbuild
+  Writing file:
+  /mnt/sdb/lio-core-2.6.git/Documentation/target/../../drivers/target/tcm_nab5000/Kconfig
+  Would you like to add tcm_nab5000to drivers/target/Kbuild..? [yes,no]: yes
+  Would you like to add tcm_nab5000to drivers/target/Kconfig..? [yes,no]: yes
+
+At the end of tcm_mod_builder.py. the script will ask to add the following
+line to drivers/target/Kbuild::
+
+	obj-$(CONFIG_TCM_NAB5000)       += tcm_nab5000/
+
+and the same for drivers/target/Kconfig::
+
+	source "drivers/target/tcm_nab5000/Kconfig"
+
+#) Run 'make menuconfig' and select the new CONFIG_TCM_NAB5000 item::
+
+	<M>   TCM_NAB5000 fabric module
+
+#) Build using 'make modules', once completed you will have::
+
+    target:/mnt/sdb/lio-core-2.6.git# ls -la drivers/target/tcm_nab5000/
+    total 1348
+    drwxr-xr-x 2 root root   4096 2010-10-05 03:23 .
+    drwxr-xr-x 9 root root   4096 2010-10-05 03:22 ..
+    -rw-r--r-- 1 root root    282 2010-10-05 03:22 Kbuild
+    -rw-r--r-- 1 root root    171 2010-10-05 03:22 Kconfig
+    -rw-r--r-- 1 root root     49 2010-10-05 03:23 modules.order
+    -rw-r--r-- 1 root root    738 2010-10-05 03:22 tcm_nab5000_base.h
+    -rw-r--r-- 1 root root   9096 2010-10-05 03:22 tcm_nab5000_configfs.c
+    -rw-r--r-- 1 root root 191200 2010-10-05 03:23 tcm_nab5000_configfs.o
+    -rw-r--r-- 1 root root  40504 2010-10-05 03:23 .tcm_nab5000_configfs.o.cmd
+    -rw-r--r-- 1 root root   5414 2010-10-05 03:22 tcm_nab5000_fabric.c
+    -rw-r--r-- 1 root root   2016 2010-10-05 03:22 tcm_nab5000_fabric.h
+    -rw-r--r-- 1 root root 190932 2010-10-05 03:23 tcm_nab5000_fabric.o
+    -rw-r--r-- 1 root root  40713 2010-10-05 03:23 .tcm_nab5000_fabric.o.cmd
+    -rw-r--r-- 1 root root 401861 2010-10-05 03:23 tcm_nab5000.ko
+    -rw-r--r-- 1 root root    265 2010-10-05 03:23 .tcm_nab5000.ko.cmd
+    -rw-r--r-- 1 root root    459 2010-10-05 03:23 tcm_nab5000.mod.c
+    -rw-r--r-- 1 root root  23896 2010-10-05 03:23 tcm_nab5000.mod.o
+    -rw-r--r-- 1 root root  22655 2010-10-05 03:23 .tcm_nab5000.mod.o.cmd
+    -rw-r--r-- 1 root root 379022 2010-10-05 03:23 tcm_nab5000.o
+    -rw-r--r-- 1 root root    211 2010-10-05 03:23 .tcm_nab5000.o.cmd
+
+#) Load the new module, create a lun_0 configfs group, and add new TCM Core
+   IBLOCK backstore symlink to port::
+
+    target:/mnt/sdb/lio-core-2.6.git# insmod drivers/target/tcm_nab5000.ko
+    target:/mnt/sdb/lio-core-2.6.git# mkdir -p /sys/kernel/config/target/nab5000/iqn.foo/tpgt_1/lun/lun_0
+    target:/mnt/sdb/lio-core-2.6.git# cd /sys/kernel/config/target/nab5000/iqn.foo/tpgt_1/lun/lun_0/
+    target:/sys/kernel/config/target/nab5000/iqn.foo/tpgt_1/lun/lun_0# ln -s /sys/kernel/config/target/core/iblock_0/lvm_test0 nab5000_port
+
+    target:/sys/kernel/config/target/nab5000/iqn.foo/tpgt_1/lun/lun_0# cd -
+    target:/mnt/sdb/lio-core-2.6.git# tree /sys/kernel/config/target/nab5000/
+    /sys/kernel/config/target/nab5000/
+    |-- discovery_auth
+    |-- iqn.foo
+    |   `-- tpgt_1
+    |       |-- acls
+    |       |-- attrib
+    |       |-- lun
+    |       |   `-- lun_0
+    |       |       |-- alua_tg_pt_gp
+    |       |       |-- alua_tg_pt_offline
+    |       |       |-- alua_tg_pt_status
+    |       |       |-- alua_tg_pt_write_md
+    |	|	`-- nab5000_port -> ../../../../../../target/core/iblock_0/lvm_test0
+    |       |-- np
+    |       `-- param
+    `-- version
+
+    target:/mnt/sdb/lio-core-2.6.git# lsmod
+    Module                  Size  Used by
+    tcm_nab5000             3935  4
+    iscsi_target_mod      193211  0
+    target_core_stgt        8090  0
+    target_core_pscsi      11122  1
+    target_core_file        9172  2
+    target_core_iblock      9280  1
+    target_core_mod       228575  31
+    tcm_nab5000,iscsi_target_mod,target_core_stgt,target_core_pscsi,target_core_file,target_core_iblock
+    libfc                  73681  0
+    scsi_debug             56265  0
+    scsi_tgt                8666  1 target_core_stgt
+    configfs               20644  2 target_core_mod
+
+----------------------------------------------------------------------
+
+Future TODO items
+=================
+
+	1) Add more T10 proto_idents
+	2) Make tcm_mod_dump_fabric_ops() smarter and generate function pointer
+	   defs directly from include/target/target_core_fabric_ops.h:struct target_core_fabric_ops
+	   structure members.
+
+October 5th, 2010
+
+Nicholas A. Bellinger <nab@linux-iscsi.org>
diff --git a/Documentation/target/tcm_mod_builder.txt b/Documentation/target/tcm_mod_builder.txt
deleted file mode 100644
index ae22f7005540..000000000000
--- a/Documentation/target/tcm_mod_builder.txt
+++ /dev/null
@@ -1,145 +0,0 @@
->>>>>>>>>> The TCM v4 fabric module script generator <<<<<<<<<<
-
-Greetings all,
-
-This document is intended to be a mini-HOWTO for using the tcm_mod_builder.py
-script to generate a brand new functional TCM v4 fabric .ko module of your very own,
-that once built can be immediately be loaded to start access the new TCM/ConfigFS
-fabric skeleton, by simply using:
-
-	modprobe $TCM_NEW_MOD
-	mkdir -p /sys/kernel/config/target/$TCM_NEW_MOD
-
-This script will create a new drivers/target/$TCM_NEW_MOD/, and will do the following
-
-	*) Generate new API callers for drivers/target/target_core_fabric_configs.c logic
-	   ->make_tpg(), ->drop_tpg(), ->make_wwn(), ->drop_wwn().  These are created
-	   into $TCM_NEW_MOD/$TCM_NEW_MOD_configfs.c
-	*) Generate basic infrastructure for loading/unloading LKMs and TCM/ConfigFS fabric module
-	   using a skeleton struct target_core_fabric_ops API template.
-	*) Based on user defined T10 Proto_Ident for the new fabric module being built,
-	   the TransportID / Initiator and Target WWPN related handlers for
-	   SPC-3 persistent reservation are automatically generated in $TCM_NEW_MOD/$TCM_NEW_MOD_fabric.c
-	   using drivers/target/target_core_fabric_lib.c logic.
-	*) NOP API calls for all other Data I/O path and fabric dependent attribute logic
-	   in $TCM_NEW_MOD/$TCM_NEW_MOD_fabric.c
-
-tcm_mod_builder.py depends upon the mandatory '-p $PROTO_IDENT' and '-m
-$FABRIC_MOD_name' parameters, and actually running the script looks like:
-
-target:/mnt/sdb/lio-core-2.6.git/Documentation/target# python tcm_mod_builder.py -p iSCSI -m tcm_nab5000
-tcm_dir: /mnt/sdb/lio-core-2.6.git/Documentation/target/../../
-Set fabric_mod_name: tcm_nab5000
-Set fabric_mod_dir:
-/mnt/sdb/lio-core-2.6.git/Documentation/target/../../drivers/target/tcm_nab5000
-Using proto_ident: iSCSI
-Creating fabric_mod_dir:
-/mnt/sdb/lio-core-2.6.git/Documentation/target/../../drivers/target/tcm_nab5000
-Writing file:
-/mnt/sdb/lio-core-2.6.git/Documentation/target/../../drivers/target/tcm_nab5000/tcm_nab5000_base.h
-Using tcm_mod_scan_fabric_ops:
-/mnt/sdb/lio-core-2.6.git/Documentation/target/../../include/target/target_core_fabric_ops.h
-Writing file:
-/mnt/sdb/lio-core-2.6.git/Documentation/target/../../drivers/target/tcm_nab5000/tcm_nab5000_fabric.c
-Writing file:
-/mnt/sdb/lio-core-2.6.git/Documentation/target/../../drivers/target/tcm_nab5000/tcm_nab5000_fabric.h
-Writing file:
-/mnt/sdb/lio-core-2.6.git/Documentation/target/../../drivers/target/tcm_nab5000/tcm_nab5000_configfs.c
-Writing file:
-/mnt/sdb/lio-core-2.6.git/Documentation/target/../../drivers/target/tcm_nab5000/Kbuild
-Writing file:
-/mnt/sdb/lio-core-2.6.git/Documentation/target/../../drivers/target/tcm_nab5000/Kconfig
-Would you like to add tcm_nab5000to drivers/target/Kbuild..? [yes,no]: yes
-Would you like to add tcm_nab5000to drivers/target/Kconfig..? [yes,no]: yes
-
-At the end of tcm_mod_builder.py. the script will ask to add the following
-line to drivers/target/Kbuild:
-
-	obj-$(CONFIG_TCM_NAB5000)       += tcm_nab5000/
-
-and the same for drivers/target/Kconfig:
-
-	source "drivers/target/tcm_nab5000/Kconfig"
-
-*) Run 'make menuconfig' and select the new CONFIG_TCM_NAB5000 item:
-
-	<M>   TCM_NAB5000 fabric module
-
-*) Build using 'make modules', once completed you will have:
-
-target:/mnt/sdb/lio-core-2.6.git# ls -la drivers/target/tcm_nab5000/
-total 1348
-drwxr-xr-x 2 root root   4096 2010-10-05 03:23 .
-drwxr-xr-x 9 root root   4096 2010-10-05 03:22 ..
--rw-r--r-- 1 root root    282 2010-10-05 03:22 Kbuild
--rw-r--r-- 1 root root    171 2010-10-05 03:22 Kconfig
--rw-r--r-- 1 root root     49 2010-10-05 03:23 modules.order
--rw-r--r-- 1 root root    738 2010-10-05 03:22 tcm_nab5000_base.h
--rw-r--r-- 1 root root   9096 2010-10-05 03:22 tcm_nab5000_configfs.c
--rw-r--r-- 1 root root 191200 2010-10-05 03:23 tcm_nab5000_configfs.o
--rw-r--r-- 1 root root  40504 2010-10-05 03:23 .tcm_nab5000_configfs.o.cmd
--rw-r--r-- 1 root root   5414 2010-10-05 03:22 tcm_nab5000_fabric.c
--rw-r--r-- 1 root root   2016 2010-10-05 03:22 tcm_nab5000_fabric.h
--rw-r--r-- 1 root root 190932 2010-10-05 03:23 tcm_nab5000_fabric.o
--rw-r--r-- 1 root root  40713 2010-10-05 03:23 .tcm_nab5000_fabric.o.cmd
--rw-r--r-- 1 root root 401861 2010-10-05 03:23 tcm_nab5000.ko
--rw-r--r-- 1 root root    265 2010-10-05 03:23 .tcm_nab5000.ko.cmd
--rw-r--r-- 1 root root    459 2010-10-05 03:23 tcm_nab5000.mod.c
--rw-r--r-- 1 root root  23896 2010-10-05 03:23 tcm_nab5000.mod.o
--rw-r--r-- 1 root root  22655 2010-10-05 03:23 .tcm_nab5000.mod.o.cmd
--rw-r--r-- 1 root root 379022 2010-10-05 03:23 tcm_nab5000.o
--rw-r--r-- 1 root root    211 2010-10-05 03:23 .tcm_nab5000.o.cmd
-
-*) Load the new module, create a lun_0 configfs group, and add new TCM Core
-   IBLOCK backstore symlink to port:
-
-target:/mnt/sdb/lio-core-2.6.git# insmod drivers/target/tcm_nab5000.ko
-target:/mnt/sdb/lio-core-2.6.git# mkdir -p /sys/kernel/config/target/nab5000/iqn.foo/tpgt_1/lun/lun_0
-target:/mnt/sdb/lio-core-2.6.git# cd /sys/kernel/config/target/nab5000/iqn.foo/tpgt_1/lun/lun_0/
-target:/sys/kernel/config/target/nab5000/iqn.foo/tpgt_1/lun/lun_0# ln -s /sys/kernel/config/target/core/iblock_0/lvm_test0 nab5000_port
-
-target:/sys/kernel/config/target/nab5000/iqn.foo/tpgt_1/lun/lun_0# cd -
-target:/mnt/sdb/lio-core-2.6.git# tree /sys/kernel/config/target/nab5000/
-/sys/kernel/config/target/nab5000/
-|-- discovery_auth
-|-- iqn.foo
-|   `-- tpgt_1
-|       |-- acls
-|       |-- attrib
-|       |-- lun
-|       |   `-- lun_0
-|       |       |-- alua_tg_pt_gp
-|       |       |-- alua_tg_pt_offline
-|       |       |-- alua_tg_pt_status
-|       |       |-- alua_tg_pt_write_md
-|	|	`-- nab5000_port -> ../../../../../../target/core/iblock_0/lvm_test0
-|       |-- np
-|       `-- param
-`-- version
-
-target:/mnt/sdb/lio-core-2.6.git# lsmod
-Module                  Size  Used by
-tcm_nab5000             3935  4
-iscsi_target_mod      193211  0
-target_core_stgt        8090  0
-target_core_pscsi      11122  1
-target_core_file        9172  2
-target_core_iblock      9280  1
-target_core_mod       228575  31
-tcm_nab5000,iscsi_target_mod,target_core_stgt,target_core_pscsi,target_core_file,target_core_iblock
-libfc                  73681  0
-scsi_debug             56265  0
-scsi_tgt                8666  1 target_core_stgt
-configfs               20644  2 target_core_mod
-
-----------------------------------------------------------------------
-
-Future TODO items:
-
-	*) Add more T10 proto_idents
-	*) Make tcm_mod_dump_fabric_ops() smarter and generate function pointer
-	   defs directly from include/target/target_core_fabric_ops.h:struct target_core_fabric_ops
-	   structure members.
-
-October 5th, 2010
-Nicholas A. Bellinger <nab@linux-iscsi.org>
diff --git a/Documentation/target/tcmu-design.rst b/Documentation/target/tcmu-design.rst
new file mode 100644
index 000000000000..a7b426707bf6
--- /dev/null
+++ b/Documentation/target/tcmu-design.rst
@@ -0,0 +1,405 @@
+====================
+TCM Userspace Design
+====================
+
+
+.. Contents:
+
+   1) TCM Userspace Design
+     a) Background
+     b) Benefits
+     c) Design constraints
+     d) Implementation overview
+        i. Mailbox
+        ii. Command ring
+        iii. Data Area
+     e) Device discovery
+     f) Device events
+     g) Other contingencies
+   2) Writing a user pass-through handler
+     a) Discovering and configuring TCMU uio devices
+     b) Waiting for events on the device(s)
+     c) Managing the command ring
+   3) A final note
+
+
+TCM Userspace Design
+====================
+
+TCM is another name for LIO, an in-kernel iSCSI target (server).
+Existing TCM targets run in the kernel.  TCMU (TCM in Userspace)
+allows userspace programs to be written which act as iSCSI targets.
+This document describes the design.
+
+The existing kernel provides modules for different SCSI transport
+protocols.  TCM also modularizes the data storage.  There are existing
+modules for file, block device, RAM or using another SCSI device as
+storage.  These are called "backstores" or "storage engines".  These
+built-in modules are implemented entirely as kernel code.
+
+Background
+----------
+
+In addition to modularizing the transport protocol used for carrying
+SCSI commands ("fabrics"), the Linux kernel target, LIO, also modularizes
+the actual data storage as well. These are referred to as "backstores"
+or "storage engines". The target comes with backstores that allow a
+file, a block device, RAM, or another SCSI device to be used for the
+local storage needed for the exported SCSI LUN. Like the rest of LIO,
+these are implemented entirely as kernel code.
+
+These backstores cover the most common use cases, but not all. One new
+use case that other non-kernel target solutions, such as tgt, are able
+to support is using Gluster's GLFS or Ceph's RBD as a backstore. The
+target then serves as a translator, allowing initiators to store data
+in these non-traditional networked storage systems, while still only
+using standard protocols themselves.
+
+If the target is a userspace process, supporting these is easy. tgt,
+for example, needs only a small adapter module for each, because the
+modules just use the available userspace libraries for RBD and GLFS.
+
+Adding support for these backstores in LIO is considerably more
+difficult, because LIO is entirely kernel code. Instead of undertaking
+the significant work to port the GLFS or RBD APIs and protocols to the
+kernel, another approach is to create a userspace pass-through
+backstore for LIO, "TCMU".
+
+
+Benefits
+--------
+
+In addition to allowing relatively easy support for RBD and GLFS, TCMU
+will also allow easier development of new backstores. TCMU combines
+with the LIO loopback fabric to become something similar to FUSE
+(Filesystem in Userspace), but at the SCSI layer instead of the
+filesystem layer. A SUSE, if you will.
+
+The disadvantage is there are more distinct components to configure, and
+potentially to malfunction. This is unavoidable, but hopefully not
+fatal if we're careful to keep things as simple as possible.
+
+Design constraints
+------------------
+
+- Good performance: high throughput, low latency
+- Cleanly handle if userspace:
+
+   1) never attaches
+   2) hangs
+   3) dies
+   4) misbehaves
+
+- Allow future flexibility in user & kernel implementations
+- Be reasonably memory-efficient
+- Simple to configure & run
+- Simple to write a userspace backend
+
+
+Implementation overview
+-----------------------
+
+The core of the TCMU interface is a memory region that is shared
+between kernel and userspace. Within this region is: a control area
+(mailbox); a lockless producer/consumer circular buffer for commands
+to be passed up, and status returned; and an in/out data buffer area.
+
+TCMU uses the pre-existing UIO subsystem. UIO allows device driver
+development in userspace, and this is conceptually very close to the
+TCMU use case, except instead of a physical device, TCMU implements a
+memory-mapped layout designed for SCSI commands. Using UIO also
+benefits TCMU by handling device introspection (e.g. a way for
+userspace to determine how large the shared region is) and signaling
+mechanisms in both directions.
+
+There are no embedded pointers in the memory region. Everything is
+expressed as an offset from the region's starting address. This allows
+the ring to still work if the user process dies and is restarted with
+the region mapped at a different virtual address.
+
+See target_core_user.h for the struct definitions.
+
+The Mailbox
+-----------
+
+The mailbox is always at the start of the shared memory region, and
+contains a version, details about the starting offset and size of the
+command ring, and head and tail pointers to be used by the kernel and
+userspace (respectively) to put commands on the ring, and indicate
+when the commands are completed.
+
+version - 1 (userspace should abort if otherwise)
+
+flags:
+    - TCMU_MAILBOX_FLAG_CAP_OOOC:
+	indicates out-of-order completion is supported.
+	See "The Command Ring" for details.
+
+cmdr_off
+	The offset of the start of the command ring from the start
+	of the memory region, to account for the mailbox size.
+cmdr_size
+	The size of the command ring. This does *not* need to be a
+	power of two.
+cmd_head
+	Modified by the kernel to indicate when a command has been
+	placed on the ring.
+cmd_tail
+	Modified by userspace to indicate when it has completed
+	processing of a command.
+
+The Command Ring
+----------------
+
+Commands are placed on the ring by the kernel incrementing
+mailbox.cmd_head by the size of the command, modulo cmdr_size, and
+then signaling userspace via uio_event_notify(). Once the command is
+completed, userspace updates mailbox.cmd_tail in the same way and
+signals the kernel via a 4-byte write(). When cmd_head equals
+cmd_tail, the ring is empty -- no commands are currently waiting to be
+processed by userspace.
+
+TCMU commands are 8-byte aligned. They start with a common header
+containing "len_op", a 32-bit value that stores the length, as well as
+the opcode in the lowest unused bits. It also contains cmd_id and
+flags fields for setting by the kernel (kflags) and userspace
+(uflags).
+
+Currently only two opcodes are defined, TCMU_OP_CMD and TCMU_OP_PAD.
+
+When the opcode is CMD, the entry in the command ring is a struct
+tcmu_cmd_entry. Userspace finds the SCSI CDB (Command Data Block) via
+tcmu_cmd_entry.req.cdb_off. This is an offset from the start of the
+overall shared memory region, not the entry. The data in/out buffers
+are accessible via tht req.iov[] array. iov_cnt contains the number of
+entries in iov[] needed to describe either the Data-In or Data-Out
+buffers. For bidirectional commands, iov_cnt specifies how many iovec
+entries cover the Data-Out area, and iov_bidi_cnt specifies how many
+iovec entries immediately after that in iov[] cover the Data-In
+area. Just like other fields, iov.iov_base is an offset from the start
+of the region.
+
+When completing a command, userspace sets rsp.scsi_status, and
+rsp.sense_buffer if necessary. Userspace then increments
+mailbox.cmd_tail by entry.hdr.length (mod cmdr_size) and signals the
+kernel via the UIO method, a 4-byte write to the file descriptor.
+
+If TCMU_MAILBOX_FLAG_CAP_OOOC is set for mailbox->flags, kernel is
+capable of handling out-of-order completions. In this case, userspace can
+handle command in different order other than original. Since kernel would
+still process the commands in the same order it appeared in the command
+ring, userspace need to update the cmd->id when completing the
+command(a.k.a steal the original command's entry).
+
+When the opcode is PAD, userspace only updates cmd_tail as above --
+it's a no-op. (The kernel inserts PAD entries to ensure each CMD entry
+is contiguous within the command ring.)
+
+More opcodes may be added in the future. If userspace encounters an
+opcode it does not handle, it must set UNKNOWN_OP bit (bit 0) in
+hdr.uflags, update cmd_tail, and proceed with processing additional
+commands, if any.
+
+The Data Area
+-------------
+
+This is shared-memory space after the command ring. The organization
+of this area is not defined in the TCMU interface, and userspace
+should access only the parts referenced by pending iovs.
+
+
+Device Discovery
+----------------
+
+Other devices may be using UIO besides TCMU. Unrelated user processes
+may also be handling different sets of TCMU devices. TCMU userspace
+processes must find their devices by scanning sysfs
+class/uio/uio*/name. For TCMU devices, these names will be of the
+format::
+
+	tcm-user/<hba_num>/<device_name>/<subtype>/<path>
+
+where "tcm-user" is common for all TCMU-backed UIO devices. <hba_num>
+and <device_name> allow userspace to find the device's path in the
+kernel target's configfs tree. Assuming the usual mount point, it is
+found at::
+
+	/sys/kernel/config/target/core/user_<hba_num>/<device_name>
+
+This location contains attributes such as "hw_block_size", that
+userspace needs to know for correct operation.
+
+<subtype> will be a userspace-process-unique string to identify the
+TCMU device as expecting to be backed by a certain handler, and <path>
+will be an additional handler-specific string for the user process to
+configure the device, if needed. The name cannot contain ':', due to
+LIO limitations.
+
+For all devices so discovered, the user handler opens /dev/uioX and
+calls mmap()::
+
+	mmap(NULL, size, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0)
+
+where size must be equal to the value read from
+/sys/class/uio/uioX/maps/map0/size.
+
+
+Device Events
+-------------
+
+If a new device is added or removed, a notification will be broadcast
+over netlink, using a generic netlink family name of "TCM-USER" and a
+multicast group named "config". This will include the UIO name as
+described in the previous section, as well as the UIO minor
+number. This should allow userspace to identify both the UIO device and
+the LIO device, so that after determining the device is supported
+(based on subtype) it can take the appropriate action.
+
+
+Other contingencies
+-------------------
+
+Userspace handler process never attaches:
+
+- TCMU will post commands, and then abort them after a timeout period
+  (30 seconds.)
+
+Userspace handler process is killed:
+
+- It is still possible to restart and re-connect to TCMU
+  devices. Command ring is preserved. However, after the timeout period,
+  the kernel will abort pending tasks.
+
+Userspace handler process hangs:
+
+- The kernel will abort pending tasks after a timeout period.
+
+Userspace handler process is malicious:
+
+- The process can trivially break the handling of devices it controls,
+  but should not be able to access kernel memory outside its shared
+  memory areas.
+
+
+Writing a user pass-through handler (with example code)
+=======================================================
+
+A user process handing a TCMU device must support the following:
+
+a) Discovering and configuring TCMU uio devices
+b) Waiting for events on the device(s)
+c) Managing the command ring: Parsing operations and commands,
+   performing work as needed, setting response fields (scsi_status and
+   possibly sense_buffer), updating cmd_tail, and notifying the kernel
+   that work has been finished
+
+First, consider instead writing a plugin for tcmu-runner. tcmu-runner
+implements all of this, and provides a higher-level API for plugin
+authors.
+
+TCMU is designed so that multiple unrelated processes can manage TCMU
+devices separately. All handlers should make sure to only open their
+devices, based opon a known subtype string.
+
+a) Discovering and configuring TCMU UIO devices::
+
+      /* error checking omitted for brevity */
+
+      int fd, dev_fd;
+      char buf[256];
+      unsigned long long map_len;
+      void *map;
+
+      fd = open("/sys/class/uio/uio0/name", O_RDONLY);
+      ret = read(fd, buf, sizeof(buf));
+      close(fd);
+      buf[ret-1] = '\0'; /* null-terminate and chop off the \n */
+
+      /* we only want uio devices whose name is a format we expect */
+      if (strncmp(buf, "tcm-user", 8))
+	exit(-1);
+
+      /* Further checking for subtype also needed here */
+
+      fd = open(/sys/class/uio/%s/maps/map0/size, O_RDONLY);
+      ret = read(fd, buf, sizeof(buf));
+      close(fd);
+      str_buf[ret-1] = '\0'; /* null-terminate and chop off the \n */
+
+      map_len = strtoull(buf, NULL, 0);
+
+      dev_fd = open("/dev/uio0", O_RDWR);
+      map = mmap(NULL, map_len, PROT_READ|PROT_WRITE, MAP_SHARED, dev_fd, 0);
+
+
+      b) Waiting for events on the device(s)
+
+      while (1) {
+        char buf[4];
+
+        int ret = read(dev_fd, buf, 4); /* will block */
+
+        handle_device_events(dev_fd, map);
+      }
+
+
+c) Managing the command ring::
+
+      #include <linux/target_core_user.h>
+
+      int handle_device_events(int fd, void *map)
+      {
+        struct tcmu_mailbox *mb = map;
+        struct tcmu_cmd_entry *ent = (void *) mb + mb->cmdr_off + mb->cmd_tail;
+        int did_some_work = 0;
+
+        /* Process events from cmd ring until we catch up with cmd_head */
+        while (ent != (void *)mb + mb->cmdr_off + mb->cmd_head) {
+
+          if (tcmu_hdr_get_op(ent->hdr.len_op) == TCMU_OP_CMD) {
+            uint8_t *cdb = (void *)mb + ent->req.cdb_off;
+            bool success = true;
+
+            /* Handle command here. */
+            printf("SCSI opcode: 0x%x\n", cdb[0]);
+
+            /* Set response fields */
+            if (success)
+              ent->rsp.scsi_status = SCSI_NO_SENSE;
+            else {
+              /* Also fill in rsp->sense_buffer here */
+              ent->rsp.scsi_status = SCSI_CHECK_CONDITION;
+            }
+          }
+          else if (tcmu_hdr_get_op(ent->hdr.len_op) != TCMU_OP_PAD) {
+            /* Tell the kernel we didn't handle unknown opcodes */
+            ent->hdr.uflags |= TCMU_UFLAG_UNKNOWN_OP;
+          }
+          else {
+            /* Do nothing for PAD entries except update cmd_tail */
+          }
+
+          /* update cmd_tail */
+          mb->cmd_tail = (mb->cmd_tail + tcmu_hdr_get_len(&ent->hdr)) % mb->cmdr_size;
+          ent = (void *) mb + mb->cmdr_off + mb->cmd_tail;
+          did_some_work = 1;
+        }
+
+        /* Notify the kernel that work has been finished */
+        if (did_some_work) {
+          uint32_t buf = 0;
+
+          write(fd, &buf, 4);
+        }
+
+        return 0;
+      }
+
+
+A final note
+============
+
+Please be careful to return codes as defined by the SCSI
+specifications. These are different than some values defined in the
+scsi/scsi.h include file. For example, CHECK CONDITION's status code
+is 2, not 1.
diff --git a/Documentation/target/tcmu-design.txt b/Documentation/target/tcmu-design.txt
deleted file mode 100644
index 4cebc1ebf99a..000000000000
--- a/Documentation/target/tcmu-design.txt
+++ /dev/null
@@ -1,381 +0,0 @@
-Contents:
-
-1) TCM Userspace Design
-  a) Background
-  b) Benefits
-  c) Design constraints
-  d) Implementation overview
-     i. Mailbox
-     ii. Command ring
-     iii. Data Area
-  e) Device discovery
-  f) Device events
-  g) Other contingencies
-2) Writing a user pass-through handler
-  a) Discovering and configuring TCMU uio devices
-  b) Waiting for events on the device(s)
-  c) Managing the command ring
-3) A final note
-
-
-TCM Userspace Design
---------------------
-
-TCM is another name for LIO, an in-kernel iSCSI target (server).
-Existing TCM targets run in the kernel.  TCMU (TCM in Userspace)
-allows userspace programs to be written which act as iSCSI targets.
-This document describes the design.
-
-The existing kernel provides modules for different SCSI transport
-protocols.  TCM also modularizes the data storage.  There are existing
-modules for file, block device, RAM or using another SCSI device as
-storage.  These are called "backstores" or "storage engines".  These
-built-in modules are implemented entirely as kernel code.
-
-Background:
-
-In addition to modularizing the transport protocol used for carrying
-SCSI commands ("fabrics"), the Linux kernel target, LIO, also modularizes
-the actual data storage as well. These are referred to as "backstores"
-or "storage engines". The target comes with backstores that allow a
-file, a block device, RAM, or another SCSI device to be used for the
-local storage needed for the exported SCSI LUN. Like the rest of LIO,
-these are implemented entirely as kernel code.
-
-These backstores cover the most common use cases, but not all. One new
-use case that other non-kernel target solutions, such as tgt, are able
-to support is using Gluster's GLFS or Ceph's RBD as a backstore. The
-target then serves as a translator, allowing initiators to store data
-in these non-traditional networked storage systems, while still only
-using standard protocols themselves.
-
-If the target is a userspace process, supporting these is easy. tgt,
-for example, needs only a small adapter module for each, because the
-modules just use the available userspace libraries for RBD and GLFS.
-
-Adding support for these backstores in LIO is considerably more
-difficult, because LIO is entirely kernel code. Instead of undertaking
-the significant work to port the GLFS or RBD APIs and protocols to the
-kernel, another approach is to create a userspace pass-through
-backstore for LIO, "TCMU".
-
-
-Benefits:
-
-In addition to allowing relatively easy support for RBD and GLFS, TCMU
-will also allow easier development of new backstores. TCMU combines
-with the LIO loopback fabric to become something similar to FUSE
-(Filesystem in Userspace), but at the SCSI layer instead of the
-filesystem layer. A SUSE, if you will.
-
-The disadvantage is there are more distinct components to configure, and
-potentially to malfunction. This is unavoidable, but hopefully not
-fatal if we're careful to keep things as simple as possible.
-
-Design constraints:
-
-- Good performance: high throughput, low latency
-- Cleanly handle if userspace:
-   1) never attaches
-   2) hangs
-   3) dies
-   4) misbehaves
-- Allow future flexibility in user & kernel implementations
-- Be reasonably memory-efficient
-- Simple to configure & run
-- Simple to write a userspace backend
-
-
-Implementation overview:
-
-The core of the TCMU interface is a memory region that is shared
-between kernel and userspace. Within this region is: a control area
-(mailbox); a lockless producer/consumer circular buffer for commands
-to be passed up, and status returned; and an in/out data buffer area.
-
-TCMU uses the pre-existing UIO subsystem. UIO allows device driver
-development in userspace, and this is conceptually very close to the
-TCMU use case, except instead of a physical device, TCMU implements a
-memory-mapped layout designed for SCSI commands. Using UIO also
-benefits TCMU by handling device introspection (e.g. a way for
-userspace to determine how large the shared region is) and signaling
-mechanisms in both directions.
-
-There are no embedded pointers in the memory region. Everything is
-expressed as an offset from the region's starting address. This allows
-the ring to still work if the user process dies and is restarted with
-the region mapped at a different virtual address.
-
-See target_core_user.h for the struct definitions.
-
-The Mailbox:
-
-The mailbox is always at the start of the shared memory region, and
-contains a version, details about the starting offset and size of the
-command ring, and head and tail pointers to be used by the kernel and
-userspace (respectively) to put commands on the ring, and indicate
-when the commands are completed.
-
-version - 1 (userspace should abort if otherwise)
-flags:
-- TCMU_MAILBOX_FLAG_CAP_OOOC: indicates out-of-order completion is
-  supported.  See "The Command Ring" for details.
-cmdr_off - The offset of the start of the command ring from the start
-of the memory region, to account for the mailbox size.
-cmdr_size - The size of the command ring. This does *not* need to be a
-power of two.
-cmd_head - Modified by the kernel to indicate when a command has been
-placed on the ring.
-cmd_tail - Modified by userspace to indicate when it has completed
-processing of a command.
-
-The Command Ring:
-
-Commands are placed on the ring by the kernel incrementing
-mailbox.cmd_head by the size of the command, modulo cmdr_size, and
-then signaling userspace via uio_event_notify(). Once the command is
-completed, userspace updates mailbox.cmd_tail in the same way and
-signals the kernel via a 4-byte write(). When cmd_head equals
-cmd_tail, the ring is empty -- no commands are currently waiting to be
-processed by userspace.
-
-TCMU commands are 8-byte aligned. They start with a common header
-containing "len_op", a 32-bit value that stores the length, as well as
-the opcode in the lowest unused bits. It also contains cmd_id and
-flags fields for setting by the kernel (kflags) and userspace
-(uflags).
-
-Currently only two opcodes are defined, TCMU_OP_CMD and TCMU_OP_PAD.
-
-When the opcode is CMD, the entry in the command ring is a struct
-tcmu_cmd_entry. Userspace finds the SCSI CDB (Command Data Block) via
-tcmu_cmd_entry.req.cdb_off. This is an offset from the start of the
-overall shared memory region, not the entry. The data in/out buffers
-are accessible via tht req.iov[] array. iov_cnt contains the number of
-entries in iov[] needed to describe either the Data-In or Data-Out
-buffers. For bidirectional commands, iov_cnt specifies how many iovec
-entries cover the Data-Out area, and iov_bidi_cnt specifies how many
-iovec entries immediately after that in iov[] cover the Data-In
-area. Just like other fields, iov.iov_base is an offset from the start
-of the region.
-
-When completing a command, userspace sets rsp.scsi_status, and
-rsp.sense_buffer if necessary. Userspace then increments
-mailbox.cmd_tail by entry.hdr.length (mod cmdr_size) and signals the
-kernel via the UIO method, a 4-byte write to the file descriptor.
-
-If TCMU_MAILBOX_FLAG_CAP_OOOC is set for mailbox->flags, kernel is
-capable of handling out-of-order completions. In this case, userspace can
-handle command in different order other than original. Since kernel would
-still process the commands in the same order it appeared in the command
-ring, userspace need to update the cmd->id when completing the
-command(a.k.a steal the original command's entry).
-
-When the opcode is PAD, userspace only updates cmd_tail as above --
-it's a no-op. (The kernel inserts PAD entries to ensure each CMD entry
-is contiguous within the command ring.)
-
-More opcodes may be added in the future. If userspace encounters an
-opcode it does not handle, it must set UNKNOWN_OP bit (bit 0) in
-hdr.uflags, update cmd_tail, and proceed with processing additional
-commands, if any.
-
-The Data Area:
-
-This is shared-memory space after the command ring. The organization
-of this area is not defined in the TCMU interface, and userspace
-should access only the parts referenced by pending iovs.
-
-
-Device Discovery:
-
-Other devices may be using UIO besides TCMU. Unrelated user processes
-may also be handling different sets of TCMU devices. TCMU userspace
-processes must find their devices by scanning sysfs
-class/uio/uio*/name. For TCMU devices, these names will be of the
-format:
-
-tcm-user/<hba_num>/<device_name>/<subtype>/<path>
-
-where "tcm-user" is common for all TCMU-backed UIO devices. <hba_num>
-and <device_name> allow userspace to find the device's path in the
-kernel target's configfs tree. Assuming the usual mount point, it is
-found at:
-
-/sys/kernel/config/target/core/user_<hba_num>/<device_name>
-
-This location contains attributes such as "hw_block_size", that
-userspace needs to know for correct operation.
-
-<subtype> will be a userspace-process-unique string to identify the
-TCMU device as expecting to be backed by a certain handler, and <path>
-will be an additional handler-specific string for the user process to
-configure the device, if needed. The name cannot contain ':', due to
-LIO limitations.
-
-For all devices so discovered, the user handler opens /dev/uioX and
-calls mmap():
-
-mmap(NULL, size, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0)
-
-where size must be equal to the value read from
-/sys/class/uio/uioX/maps/map0/size.
-
-
-Device Events:
-
-If a new device is added or removed, a notification will be broadcast
-over netlink, using a generic netlink family name of "TCM-USER" and a
-multicast group named "config". This will include the UIO name as
-described in the previous section, as well as the UIO minor
-number. This should allow userspace to identify both the UIO device and
-the LIO device, so that after determining the device is supported
-(based on subtype) it can take the appropriate action.
-
-
-Other contingencies:
-
-Userspace handler process never attaches:
-
-- TCMU will post commands, and then abort them after a timeout period
-  (30 seconds.)
-
-Userspace handler process is killed:
-
-- It is still possible to restart and re-connect to TCMU
-  devices. Command ring is preserved. However, after the timeout period,
-  the kernel will abort pending tasks.
-
-Userspace handler process hangs:
-
-- The kernel will abort pending tasks after a timeout period.
-
-Userspace handler process is malicious:
-
-- The process can trivially break the handling of devices it controls,
-  but should not be able to access kernel memory outside its shared
-  memory areas.
-
-
-Writing a user pass-through handler (with example code)
--------------------------------------------------------
-
-A user process handing a TCMU device must support the following:
-
-a) Discovering and configuring TCMU uio devices
-b) Waiting for events on the device(s)
-c) Managing the command ring: Parsing operations and commands,
-   performing work as needed, setting response fields (scsi_status and
-   possibly sense_buffer), updating cmd_tail, and notifying the kernel
-   that work has been finished
-
-First, consider instead writing a plugin for tcmu-runner. tcmu-runner
-implements all of this, and provides a higher-level API for plugin
-authors.
-
-TCMU is designed so that multiple unrelated processes can manage TCMU
-devices separately. All handlers should make sure to only open their
-devices, based opon a known subtype string.
-
-a) Discovering and configuring TCMU UIO devices:
-
-(error checking omitted for brevity)
-
-int fd, dev_fd;
-char buf[256];
-unsigned long long map_len;
-void *map;
-
-fd = open("/sys/class/uio/uio0/name", O_RDONLY);
-ret = read(fd, buf, sizeof(buf));
-close(fd);
-buf[ret-1] = '\0'; /* null-terminate and chop off the \n */
-
-/* we only want uio devices whose name is a format we expect */
-if (strncmp(buf, "tcm-user", 8))
-	exit(-1);
-
-/* Further checking for subtype also needed here */
-
-fd = open(/sys/class/uio/%s/maps/map0/size, O_RDONLY);
-ret = read(fd, buf, sizeof(buf));
-close(fd);
-str_buf[ret-1] = '\0'; /* null-terminate and chop off the \n */
-
-map_len = strtoull(buf, NULL, 0);
-
-dev_fd = open("/dev/uio0", O_RDWR);
-map = mmap(NULL, map_len, PROT_READ|PROT_WRITE, MAP_SHARED, dev_fd, 0);
-
-
-b) Waiting for events on the device(s)
-
-while (1) {
-  char buf[4];
-
-  int ret = read(dev_fd, buf, 4); /* will block */
-
-  handle_device_events(dev_fd, map);
-}
-
-
-c) Managing the command ring
-
-#include <linux/target_core_user.h>
-
-int handle_device_events(int fd, void *map)
-{
-  struct tcmu_mailbox *mb = map;
-  struct tcmu_cmd_entry *ent = (void *) mb + mb->cmdr_off + mb->cmd_tail;
-  int did_some_work = 0;
-
-  /* Process events from cmd ring until we catch up with cmd_head */
-  while (ent != (void *)mb + mb->cmdr_off + mb->cmd_head) {
-
-    if (tcmu_hdr_get_op(ent->hdr.len_op) == TCMU_OP_CMD) {
-      uint8_t *cdb = (void *)mb + ent->req.cdb_off;
-      bool success = true;
-
-      /* Handle command here. */
-      printf("SCSI opcode: 0x%x\n", cdb[0]);
-
-      /* Set response fields */
-      if (success)
-        ent->rsp.scsi_status = SCSI_NO_SENSE;
-      else {
-        /* Also fill in rsp->sense_buffer here */
-        ent->rsp.scsi_status = SCSI_CHECK_CONDITION;
-      }
-    }
-    else if (tcmu_hdr_get_op(ent->hdr.len_op) != TCMU_OP_PAD) {
-      /* Tell the kernel we didn't handle unknown opcodes */
-      ent->hdr.uflags |= TCMU_UFLAG_UNKNOWN_OP;
-    }
-    else {
-      /* Do nothing for PAD entries except update cmd_tail */
-    }
-
-    /* update cmd_tail */
-    mb->cmd_tail = (mb->cmd_tail + tcmu_hdr_get_len(&ent->hdr)) % mb->cmdr_size;
-    ent = (void *) mb + mb->cmdr_off + mb->cmd_tail;
-    did_some_work = 1;
-  }
-
-  /* Notify the kernel that work has been finished */
-  if (did_some_work) {
-    uint32_t buf = 0;
-
-    write(fd, &buf, 4);
-  }
-
-  return 0;
-}
-
-
-A final note
-------------
-
-Please be careful to return codes as defined by the SCSI
-specifications. These are different than some values defined in the
-scsi/scsi.h include file. For example, CHECK CONDITION's status code
-is 2, not 1.
diff --git a/scripts/documentation-file-ref-check b/scripts/documentation-file-ref-check
index 440227bb55a9..a4139a576726 100755
--- a/scripts/documentation-file-ref-check
+++ b/scripts/documentation-file-ref-check
@@ -124,7 +124,7 @@ while (<IN>) {
 		# Remove sched-pelt false-positive
 		next if ($fulref =~ m,^Documentation/scheduler/sched-pelt$,);
 
-		# Discard some build examples from Documentation/target/tcm_mod_builder.txt
+		# Discard some build examples from Documentation/target/tcm_mod_builder.rst
 		next if ($fulref =~ m,mnt/sdb/lio-core-2.6.git/Documentation/target,);
 
 		# Check if exists, evaluating wildcards
-- 
cgit v1.2.3


From 458f69ef36656dc74679667380422dd8063eabfb Mon Sep 17 00:00:00 2001
From: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Date: Wed, 12 Jun 2019 14:53:00 -0300
Subject: docs: timers: convert docs to ReST and rename to *.rst

The conversion here is really trivial: just a bunch of title
markups and very few puntual changes is enough to make it to
be parsed by Sphinx and generate a nice html.

The conversion is actually:
  - add blank lines and identation in order to identify paragraphs;
  - fix tables markups;
  - add some lists markups;
  - mark literal blocks;
  - adjust title markups.

At its new index.rst, let's add a :orphan: while this is not linked to
the main index.rst file, in order to avoid build warnings.

Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Acked-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
---
 Documentation/timers/NO_HZ.txt        | 318 ---------------------------------
 Documentation/timers/highres.rst      | 250 ++++++++++++++++++++++++++
 Documentation/timers/highres.txt      | 249 --------------------------
 Documentation/timers/hpet.rst         |  30 ++++
 Documentation/timers/hpet.txt         |  28 ---
 Documentation/timers/hrtimers.rst     | 178 +++++++++++++++++++
 Documentation/timers/hrtimers.txt     | 178 -------------------
 Documentation/timers/index.rst        |  22 +++
 Documentation/timers/no_hz.rst        | 326 ++++++++++++++++++++++++++++++++++
 Documentation/timers/timekeeping.rst  | 180 +++++++++++++++++++
 Documentation/timers/timekeeping.txt  | 179 -------------------
 Documentation/timers/timers-howto.rst | 112 ++++++++++++
 Documentation/timers/timers-howto.txt | 105 -----------
 MAINTAINERS                           |   2 +-
 drivers/media/usb/dvb-usb-v2/anysee.c |   2 +-
 drivers/regulator/core.c              |   2 +-
 include/linux/iopoll.h                |   4 +-
 include/linux/regmap.h                |   4 +-
 scripts/checkpatch.pl                 |   8 +-
 sound/soc/sof/ops.h                   |   2 +-
 20 files changed, 1110 insertions(+), 1069 deletions(-)
 delete mode 100644 Documentation/timers/NO_HZ.txt
 create mode 100644 Documentation/timers/highres.rst
 delete mode 100644 Documentation/timers/highres.txt
 create mode 100644 Documentation/timers/hpet.rst
 delete mode 100644 Documentation/timers/hpet.txt
 create mode 100644 Documentation/timers/hrtimers.rst
 delete mode 100644 Documentation/timers/hrtimers.txt
 create mode 100644 Documentation/timers/index.rst
 create mode 100644 Documentation/timers/no_hz.rst
 create mode 100644 Documentation/timers/timekeeping.rst
 delete mode 100644 Documentation/timers/timekeeping.txt
 create mode 100644 Documentation/timers/timers-howto.rst
 delete mode 100644 Documentation/timers/timers-howto.txt

(limited to 'scripts')

diff --git a/Documentation/timers/NO_HZ.txt b/Documentation/timers/NO_HZ.txt
deleted file mode 100644
index 9591092da5e0..000000000000
--- a/Documentation/timers/NO_HZ.txt
+++ /dev/null
@@ -1,318 +0,0 @@
-		NO_HZ: Reducing Scheduling-Clock Ticks
-
-
-This document describes Kconfig options and boot parameters that can
-reduce the number of scheduling-clock interrupts, thereby improving energy
-efficiency and reducing OS jitter.  Reducing OS jitter is important for
-some types of computationally intensive high-performance computing (HPC)
-applications and for real-time applications.
-
-There are three main ways of managing scheduling-clock interrupts
-(also known as "scheduling-clock ticks" or simply "ticks"):
-
-1.	Never omit scheduling-clock ticks (CONFIG_HZ_PERIODIC=y or
-	CONFIG_NO_HZ=n for older kernels).  You normally will -not-
-	want to choose this option.
-
-2.	Omit scheduling-clock ticks on idle CPUs (CONFIG_NO_HZ_IDLE=y or
-	CONFIG_NO_HZ=y for older kernels).  This is the most common
-	approach, and should be the default.
-
-3.	Omit scheduling-clock ticks on CPUs that are either idle or that
-	have only one runnable task (CONFIG_NO_HZ_FULL=y).  Unless you
-	are running realtime applications or certain types of HPC
-	workloads, you will normally -not- want this option.
-
-These three cases are described in the following three sections, followed
-by a third section on RCU-specific considerations, a fourth section
-discussing testing, and a fifth and final section listing known issues.
-
-
-NEVER OMIT SCHEDULING-CLOCK TICKS
-
-Very old versions of Linux from the 1990s and the very early 2000s
-are incapable of omitting scheduling-clock ticks.  It turns out that
-there are some situations where this old-school approach is still the
-right approach, for example, in heavy workloads with lots of tasks
-that use short bursts of CPU, where there are very frequent idle
-periods, but where these idle periods are also quite short (tens or
-hundreds of microseconds).  For these types of workloads, scheduling
-clock interrupts will normally be delivered any way because there
-will frequently be multiple runnable tasks per CPU.  In these cases,
-attempting to turn off the scheduling clock interrupt will have no effect
-other than increasing the overhead of switching to and from idle and
-transitioning between user and kernel execution.
-
-This mode of operation can be selected using CONFIG_HZ_PERIODIC=y (or
-CONFIG_NO_HZ=n for older kernels).
-
-However, if you are instead running a light workload with long idle
-periods, failing to omit scheduling-clock interrupts will result in
-excessive power consumption.  This is especially bad on battery-powered
-devices, where it results in extremely short battery lifetimes.  If you
-are running light workloads, you should therefore read the following
-section.
-
-In addition, if you are running either a real-time workload or an HPC
-workload with short iterations, the scheduling-clock interrupts can
-degrade your applications performance.  If this describes your workload,
-you should read the following two sections.
-
-
-OMIT SCHEDULING-CLOCK TICKS FOR IDLE CPUs
-
-If a CPU is idle, there is little point in sending it a scheduling-clock
-interrupt.  After all, the primary purpose of a scheduling-clock interrupt
-is to force a busy CPU to shift its attention among multiple duties,
-and an idle CPU has no duties to shift its attention among.
-
-The CONFIG_NO_HZ_IDLE=y Kconfig option causes the kernel to avoid sending
-scheduling-clock interrupts to idle CPUs, which is critically important
-both to battery-powered devices and to highly virtualized mainframes.
-A battery-powered device running a CONFIG_HZ_PERIODIC=y kernel would
-drain its battery very quickly, easily 2-3 times as fast as would the
-same device running a CONFIG_NO_HZ_IDLE=y kernel.  A mainframe running
-1,500 OS instances might find that half of its CPU time was consumed by
-unnecessary scheduling-clock interrupts.  In these situations, there
-is strong motivation to avoid sending scheduling-clock interrupts to
-idle CPUs.  That said, dyntick-idle mode is not free:
-
-1.	It increases the number of instructions executed on the path
-	to and from the idle loop.
-
-2.	On many architectures, dyntick-idle mode also increases the
-	number of expensive clock-reprogramming operations.
-
-Therefore, systems with aggressive real-time response constraints often
-run CONFIG_HZ_PERIODIC=y kernels (or CONFIG_NO_HZ=n for older kernels)
-in order to avoid degrading from-idle transition latencies.
-
-An idle CPU that is not receiving scheduling-clock interrupts is said to
-be "dyntick-idle", "in dyntick-idle mode", "in nohz mode", or "running
-tickless".  The remainder of this document will use "dyntick-idle mode".
-
-There is also a boot parameter "nohz=" that can be used to disable
-dyntick-idle mode in CONFIG_NO_HZ_IDLE=y kernels by specifying "nohz=off".
-By default, CONFIG_NO_HZ_IDLE=y kernels boot with "nohz=on", enabling
-dyntick-idle mode.
-
-
-OMIT SCHEDULING-CLOCK TICKS FOR CPUs WITH ONLY ONE RUNNABLE TASK
-
-If a CPU has only one runnable task, there is little point in sending it
-a scheduling-clock interrupt because there is no other task to switch to.
-Note that omitting scheduling-clock ticks for CPUs with only one runnable
-task implies also omitting them for idle CPUs.
-
-The CONFIG_NO_HZ_FULL=y Kconfig option causes the kernel to avoid
-sending scheduling-clock interrupts to CPUs with a single runnable task,
-and such CPUs are said to be "adaptive-ticks CPUs".  This is important
-for applications with aggressive real-time response constraints because
-it allows them to improve their worst-case response times by the maximum
-duration of a scheduling-clock interrupt.  It is also important for
-computationally intensive short-iteration workloads:  If any CPU is
-delayed during a given iteration, all the other CPUs will be forced to
-wait idle while the delayed CPU finishes.  Thus, the delay is multiplied
-by one less than the number of CPUs.  In these situations, there is
-again strong motivation to avoid sending scheduling-clock interrupts.
-
-By default, no CPU will be an adaptive-ticks CPU.  The "nohz_full="
-boot parameter specifies the adaptive-ticks CPUs.  For example,
-"nohz_full=1,6-8" says that CPUs 1, 6, 7, and 8 are to be adaptive-ticks
-CPUs.  Note that you are prohibited from marking all of the CPUs as
-adaptive-tick CPUs:  At least one non-adaptive-tick CPU must remain
-online to handle timekeeping tasks in order to ensure that system
-calls like gettimeofday() returns accurate values on adaptive-tick CPUs.
-(This is not an issue for CONFIG_NO_HZ_IDLE=y because there are no running
-user processes to observe slight drifts in clock rate.)  Therefore, the
-boot CPU is prohibited from entering adaptive-ticks mode.  Specifying a
-"nohz_full=" mask that includes the boot CPU will result in a boot-time
-error message, and the boot CPU will be removed from the mask.  Note that
-this means that your system must have at least two CPUs in order for
-CONFIG_NO_HZ_FULL=y to do anything for you.
-
-Finally, adaptive-ticks CPUs must have their RCU callbacks offloaded.
-This is covered in the "RCU IMPLICATIONS" section below.
-
-Normally, a CPU remains in adaptive-ticks mode as long as possible.
-In particular, transitioning to kernel mode does not automatically change
-the mode.  Instead, the CPU will exit adaptive-ticks mode only if needed,
-for example, if that CPU enqueues an RCU callback.
-
-Just as with dyntick-idle mode, the benefits of adaptive-tick mode do
-not come for free:
-
-1.	CONFIG_NO_HZ_FULL selects CONFIG_NO_HZ_COMMON, so you cannot run
-	adaptive ticks without also running dyntick idle.  This dependency
-	extends down into the implementation, so that all of the costs
-	of CONFIG_NO_HZ_IDLE are also incurred by CONFIG_NO_HZ_FULL.
-
-2.	The user/kernel transitions are slightly more expensive due
-	to the need to inform kernel subsystems (such as RCU) about
-	the change in mode.
-
-3.	POSIX CPU timers prevent CPUs from entering adaptive-tick mode.
-	Real-time applications needing to take actions based on CPU time
-	consumption need to use other means of doing so.
-
-4.	If there are more perf events pending than the hardware can
-	accommodate, they are normally round-robined so as to collect
-	all of them over time.  Adaptive-tick mode may prevent this
-	round-robining from happening.  This will likely be fixed by
-	preventing CPUs with large numbers of perf events pending from
-	entering adaptive-tick mode.
-
-5.	Scheduler statistics for adaptive-tick CPUs may be computed
-	slightly differently than those for non-adaptive-tick CPUs.
-	This might in turn perturb load-balancing of real-time tasks.
-
-6.	The LB_BIAS scheduler feature is disabled by adaptive ticks.
-
-Although improvements are expected over time, adaptive ticks is quite
-useful for many types of real-time and compute-intensive applications.
-However, the drawbacks listed above mean that adaptive ticks should not
-(yet) be enabled by default.
-
-
-RCU IMPLICATIONS
-
-There are situations in which idle CPUs cannot be permitted to
-enter either dyntick-idle mode or adaptive-tick mode, the most
-common being when that CPU has RCU callbacks pending.
-
-The CONFIG_RCU_FAST_NO_HZ=y Kconfig option may be used to cause such CPUs
-to enter dyntick-idle mode or adaptive-tick mode anyway.  In this case,
-a timer will awaken these CPUs every four jiffies in order to ensure
-that the RCU callbacks are processed in a timely fashion.
-
-Another approach is to offload RCU callback processing to "rcuo" kthreads
-using the CONFIG_RCU_NOCB_CPU=y Kconfig option.  The specific CPUs to
-offload may be selected using The "rcu_nocbs=" kernel boot parameter,
-which takes a comma-separated list of CPUs and CPU ranges, for example,
-"1,3-5" selects CPUs 1, 3, 4, and 5.
-
-The offloaded CPUs will never queue RCU callbacks, and therefore RCU
-never prevents offloaded CPUs from entering either dyntick-idle mode
-or adaptive-tick mode.  That said, note that it is up to userspace to
-pin the "rcuo" kthreads to specific CPUs if desired.  Otherwise, the
-scheduler will decide where to run them, which might or might not be
-where you want them to run.
-
-
-TESTING
-
-So you enable all the OS-jitter features described in this document,
-but do not see any change in your workload's behavior.  Is this because
-your workload isn't affected that much by OS jitter, or is it because
-something else is in the way?  This section helps answer this question
-by providing a simple OS-jitter test suite, which is available on branch
-master of the following git archive:
-
-git://git.kernel.org/pub/scm/linux/kernel/git/frederic/dynticks-testing.git
-
-Clone this archive and follow the instructions in the README file.
-This test procedure will produce a trace that will allow you to evaluate
-whether or not you have succeeded in removing OS jitter from your system.
-If this trace shows that you have removed OS jitter as much as is
-possible, then you can conclude that your workload is not all that
-sensitive to OS jitter.
-
-Note: this test requires that your system have at least two CPUs.
-We do not currently have a good way to remove OS jitter from single-CPU
-systems.
-
-
-KNOWN ISSUES
-
-o	Dyntick-idle slows transitions to and from idle slightly.
-	In practice, this has not been a problem except for the most
-	aggressive real-time workloads, which have the option of disabling
-	dyntick-idle mode, an option that most of them take.  However,
-	some workloads will no doubt want to use adaptive ticks to
-	eliminate scheduling-clock interrupt latencies.  Here are some
-	options for these workloads:
-
-	a.	Use PMQOS from userspace to inform the kernel of your
-		latency requirements (preferred).
-
-	b.	On x86 systems, use the "idle=mwait" boot parameter.
-
-	c.	On x86 systems, use the "intel_idle.max_cstate=" to limit
-	`	the maximum C-state depth.
-
-	d.	On x86 systems, use the "idle=poll" boot parameter.
-		However, please note that use of this parameter can cause
-		your CPU to overheat, which may cause thermal throttling
-		to degrade your latencies -- and that this degradation can
-		be even worse than that of dyntick-idle.  Furthermore,
-		this parameter effectively disables Turbo Mode on Intel
-		CPUs, which can significantly reduce maximum performance.
-
-o	Adaptive-ticks slows user/kernel transitions slightly.
-	This is not expected to be a problem for computationally intensive
-	workloads, which have few such transitions.  Careful benchmarking
-	will be required to determine whether or not other workloads
-	are significantly affected by this effect.
-
-o	Adaptive-ticks does not do anything unless there is only one
-	runnable task for a given CPU, even though there are a number
-	of other situations where the scheduling-clock tick is not
-	needed.  To give but one example, consider a CPU that has one
-	runnable high-priority SCHED_FIFO task and an arbitrary number
-	of low-priority SCHED_OTHER tasks.  In this case, the CPU is
-	required to run the SCHED_FIFO task until it either blocks or
-	some other higher-priority task awakens on (or is assigned to)
-	this CPU, so there is no point in sending a scheduling-clock
-	interrupt to this CPU.	However, the current implementation
-	nevertheless sends scheduling-clock interrupts to CPUs having a
-	single runnable SCHED_FIFO task and multiple runnable SCHED_OTHER
-	tasks, even though these interrupts are unnecessary.
-
-	And even when there are multiple runnable tasks on a given CPU,
-	there is little point in interrupting that CPU until the current
-	running task's timeslice expires, which is almost always way
-	longer than the time of the next scheduling-clock interrupt.
-
-	Better handling of these sorts of situations is future work.
-
-o	A reboot is required to reconfigure both adaptive idle and RCU
-	callback offloading.  Runtime reconfiguration could be provided
-	if needed, however, due to the complexity of reconfiguring RCU at
-	runtime, there would need to be an earthshakingly good reason.
-	Especially given that you have the straightforward option of
-	simply offloading RCU callbacks from all CPUs and pinning them
-	where you want them whenever you want them pinned.
-
-o	Additional configuration is required to deal with other sources
-	of OS jitter, including interrupts and system-utility tasks
-	and processes.  This configuration normally involves binding
-	interrupts and tasks to particular CPUs.
-
-o	Some sources of OS jitter can currently be eliminated only by
-	constraining the workload.  For example, the only way to eliminate
-	OS jitter due to global TLB shootdowns is to avoid the unmapping
-	operations (such as kernel module unload operations) that
-	result in these shootdowns.  For another example, page faults
-	and TLB misses can be reduced (and in some cases eliminated) by
-	using huge pages and by constraining the amount of memory used
-	by the application.  Pre-faulting the working set can also be
-	helpful, especially when combined with the mlock() and mlockall()
-	system calls.
-
-o	Unless all CPUs are idle, at least one CPU must keep the
-	scheduling-clock interrupt going in order to support accurate
-	timekeeping.
-
-o	If there might potentially be some adaptive-ticks CPUs, there
-	will be at least one CPU keeping the scheduling-clock interrupt
-	going, even if all CPUs are otherwise idle.
-
-	Better handling of this situation is ongoing work.
-
-o	Some process-handling operations still require the occasional
-	scheduling-clock tick.	These operations include calculating CPU
-	load, maintaining sched average, computing CFS entity vruntime,
-	computing avenrun, and carrying out load balancing.  They are
-	currently accommodated by scheduling-clock tick every second
-	or so.	On-going work will eliminate the need even for these
-	infrequent scheduling-clock ticks.
diff --git a/Documentation/timers/highres.rst b/Documentation/timers/highres.rst
new file mode 100644
index 000000000000..bde5eb7e5c9e
--- /dev/null
+++ b/Documentation/timers/highres.rst
@@ -0,0 +1,250 @@
+=====================================================
+High resolution timers and dynamic ticks design notes
+=====================================================
+
+Further information can be found in the paper of the OLS 2006 talk "hrtimers
+and beyond". The paper is part of the OLS 2006 Proceedings Volume 1, which can
+be found on the OLS website:
+https://www.kernel.org/doc/ols/2006/ols2006v1-pages-333-346.pdf
+
+The slides to this talk are available from:
+http://www.cs.columbia.edu/~nahum/w6998/papers/ols2006-hrtimers-slides.pdf
+
+The slides contain five figures (pages 2, 15, 18, 20, 22), which illustrate the
+changes in the time(r) related Linux subsystems. Figure #1 (p. 2) shows the
+design of the Linux time(r) system before hrtimers and other building blocks
+got merged into mainline.
+
+Note: the paper and the slides are talking about "clock event source", while we
+switched to the name "clock event devices" in meantime.
+
+The design contains the following basic building blocks:
+
+- hrtimer base infrastructure
+- timeofday and clock source management
+- clock event management
+- high resolution timer functionality
+- dynamic ticks
+
+
+hrtimer base infrastructure
+---------------------------
+
+The hrtimer base infrastructure was merged into the 2.6.16 kernel. Details of
+the base implementation are covered in Documentation/timers/hrtimers.rst. See
+also figure #2 (OLS slides p. 15)
+
+The main differences to the timer wheel, which holds the armed timer_list type
+timers are:
+
+       - time ordered enqueueing into a rb-tree
+       - independent of ticks (the processing is based on nanoseconds)
+
+
+timeofday and clock source management
+-------------------------------------
+
+John Stultz's Generic Time Of Day (GTOD) framework moves a large portion of
+code out of the architecture-specific areas into a generic management
+framework, as illustrated in figure #3 (OLS slides p. 18). The architecture
+specific portion is reduced to the low level hardware details of the clock
+sources, which are registered in the framework and selected on a quality based
+decision. The low level code provides hardware setup and readout routines and
+initializes data structures, which are used by the generic time keeping code to
+convert the clock ticks to nanosecond based time values. All other time keeping
+related functionality is moved into the generic code. The GTOD base patch got
+merged into the 2.6.18 kernel.
+
+Further information about the Generic Time Of Day framework is available in the
+OLS 2005 Proceedings Volume 1:
+
+	http://www.linuxsymposium.org/2005/linuxsymposium_procv1.pdf
+
+The paper "We Are Not Getting Any Younger: A New Approach to Time and
+Timers" was written by J. Stultz, D.V. Hart, & N. Aravamudan.
+
+Figure #3 (OLS slides p.18) illustrates the transformation.
+
+
+clock event management
+----------------------
+
+While clock sources provide read access to the monotonically increasing time
+value, clock event devices are used to schedule the next event
+interrupt(s). The next event is currently defined to be periodic, with its
+period defined at compile time. The setup and selection of the event device
+for various event driven functionalities is hardwired into the architecture
+dependent code. This results in duplicated code across all architectures and
+makes it extremely difficult to change the configuration of the system to use
+event interrupt devices other than those already built into the
+architecture. Another implication of the current design is that it is necessary
+to touch all the architecture-specific implementations in order to provide new
+functionality like high resolution timers or dynamic ticks.
+
+The clock events subsystem tries to address this problem by providing a generic
+solution to manage clock event devices and their usage for the various clock
+event driven kernel functionalities. The goal of the clock event subsystem is
+to minimize the clock event related architecture dependent code to the pure
+hardware related handling and to allow easy addition and utilization of new
+clock event devices. It also minimizes the duplicated code across the
+architectures as it provides generic functionality down to the interrupt
+service handler, which is almost inherently hardware dependent.
+
+Clock event devices are registered either by the architecture dependent boot
+code or at module insertion time. Each clock event device fills a data
+structure with clock-specific property parameters and callback functions. The
+clock event management decides, by using the specified property parameters, the
+set of system functions a clock event device will be used to support. This
+includes the distinction of per-CPU and per-system global event devices.
+
+System-level global event devices are used for the Linux periodic tick. Per-CPU
+event devices are used to provide local CPU functionality such as process
+accounting, profiling, and high resolution timers.
+
+The management layer assigns one or more of the following functions to a clock
+event device:
+
+      - system global periodic tick (jiffies update)
+      - cpu local update_process_times
+      - cpu local profiling
+      - cpu local next event interrupt (non periodic mode)
+
+The clock event device delegates the selection of those timer interrupt related
+functions completely to the management layer. The clock management layer stores
+a function pointer in the device description structure, which has to be called
+from the hardware level handler. This removes a lot of duplicated code from the
+architecture specific timer interrupt handlers and hands the control over the
+clock event devices and the assignment of timer interrupt related functionality
+to the core code.
+
+The clock event layer API is rather small. Aside from the clock event device
+registration interface it provides functions to schedule the next event
+interrupt, clock event device notification service and support for suspend and
+resume.
+
+The framework adds about 700 lines of code which results in a 2KB increase of
+the kernel binary size. The conversion of i386 removes about 100 lines of
+code. The binary size decrease is in the range of 400 byte. We believe that the
+increase of flexibility and the avoidance of duplicated code across
+architectures justifies the slight increase of the binary size.
+
+The conversion of an architecture has no functional impact, but allows to
+utilize the high resolution and dynamic tick functionalities without any change
+to the clock event device and timer interrupt code. After the conversion the
+enabling of high resolution timers and dynamic ticks is simply provided by
+adding the kernel/time/Kconfig file to the architecture specific Kconfig and
+adding the dynamic tick specific calls to the idle routine (a total of 3 lines
+added to the idle function and the Kconfig file)
+
+Figure #4 (OLS slides p.20) illustrates the transformation.
+
+
+high resolution timer functionality
+-----------------------------------
+
+During system boot it is not possible to use the high resolution timer
+functionality, while making it possible would be difficult and would serve no
+useful function. The initialization of the clock event device framework, the
+clock source framework (GTOD) and hrtimers itself has to be done and
+appropriate clock sources and clock event devices have to be registered before
+the high resolution functionality can work. Up to the point where hrtimers are
+initialized, the system works in the usual low resolution periodic mode. The
+clock source and the clock event device layers provide notification functions
+which inform hrtimers about availability of new hardware. hrtimers validates
+the usability of the registered clock sources and clock event devices before
+switching to high resolution mode. This ensures also that a kernel which is
+configured for high resolution timers can run on a system which lacks the
+necessary hardware support.
+
+The high resolution timer code does not support SMP machines which have only
+global clock event devices. The support of such hardware would involve IPI
+calls when an interrupt happens. The overhead would be much larger than the
+benefit. This is the reason why we currently disable high resolution and
+dynamic ticks on i386 SMP systems which stop the local APIC in C3 power
+state. A workaround is available as an idea, but the problem has not been
+tackled yet.
+
+The time ordered insertion of timers provides all the infrastructure to decide
+whether the event device has to be reprogrammed when a timer is added. The
+decision is made per timer base and synchronized across per-cpu timer bases in
+a support function. The design allows the system to utilize separate per-CPU
+clock event devices for the per-CPU timer bases, but currently only one
+reprogrammable clock event device per-CPU is utilized.
+
+When the timer interrupt happens, the next event interrupt handler is called
+from the clock event distribution code and moves expired timers from the
+red-black tree to a separate double linked list and invokes the softirq
+handler. An additional mode field in the hrtimer structure allows the system to
+execute callback functions directly from the next event interrupt handler. This
+is restricted to code which can safely be executed in the hard interrupt
+context. This applies, for example, to the common case of a wakeup function as
+used by nanosleep. The advantage of executing the handler in the interrupt
+context is the avoidance of up to two context switches - from the interrupted
+context to the softirq and to the task which is woken up by the expired
+timer.
+
+Once a system has switched to high resolution mode, the periodic tick is
+switched off. This disables the per system global periodic clock event device -
+e.g. the PIT on i386 SMP systems.
+
+The periodic tick functionality is provided by an per-cpu hrtimer. The callback
+function is executed in the next event interrupt context and updates jiffies
+and calls update_process_times and profiling. The implementation of the hrtimer
+based periodic tick is designed to be extended with dynamic tick functionality.
+This allows to use a single clock event device to schedule high resolution
+timer and periodic events (jiffies tick, profiling, process accounting) on UP
+systems. This has been proved to work with the PIT on i386 and the Incrementer
+on PPC.
+
+The softirq for running the hrtimer queues and executing the callbacks has been
+separated from the tick bound timer softirq to allow accurate delivery of high
+resolution timer signals which are used by itimer and POSIX interval
+timers. The execution of this softirq can still be delayed by other softirqs,
+but the overall latencies have been significantly improved by this separation.
+
+Figure #5 (OLS slides p.22) illustrates the transformation.
+
+
+dynamic ticks
+-------------
+
+Dynamic ticks are the logical consequence of the hrtimer based periodic tick
+replacement (sched_tick). The functionality of the sched_tick hrtimer is
+extended by three functions:
+
+- hrtimer_stop_sched_tick
+- hrtimer_restart_sched_tick
+- hrtimer_update_jiffies
+
+hrtimer_stop_sched_tick() is called when a CPU goes into idle state. The code
+evaluates the next scheduled timer event (from both hrtimers and the timer
+wheel) and in case that the next event is further away than the next tick it
+reprograms the sched_tick to this future event, to allow longer idle sleeps
+without worthless interruption by the periodic tick. The function is also
+called when an interrupt happens during the idle period, which does not cause a
+reschedule. The call is necessary as the interrupt handler might have armed a
+new timer whose expiry time is before the time which was identified as the
+nearest event in the previous call to hrtimer_stop_sched_tick.
+
+hrtimer_restart_sched_tick() is called when the CPU leaves the idle state before
+it calls schedule(). hrtimer_restart_sched_tick() resumes the periodic tick,
+which is kept active until the next call to hrtimer_stop_sched_tick().
+
+hrtimer_update_jiffies() is called from irq_enter() when an interrupt happens
+in the idle period to make sure that jiffies are up to date and the interrupt
+handler has not to deal with an eventually stale jiffy value.
+
+The dynamic tick feature provides statistical values which are exported to
+userspace via /proc/stat and can be made available for enhanced power
+management control.
+
+The implementation leaves room for further development like full tickless
+systems, where the time slice is controlled by the scheduler, variable
+frequency profiling, and a complete removal of jiffies in the future.
+
+
+Aside the current initial submission of i386 support, the patchset has been
+extended to x86_64 and ARM already. Initial (work in progress) support is also
+available for MIPS and PowerPC.
+
+	  Thomas, Ingo
diff --git a/Documentation/timers/highres.txt b/Documentation/timers/highres.txt
deleted file mode 100644
index 8f9741592123..000000000000
--- a/Documentation/timers/highres.txt
+++ /dev/null
@@ -1,249 +0,0 @@
-High resolution timers and dynamic ticks design notes
------------------------------------------------------
-
-Further information can be found in the paper of the OLS 2006 talk "hrtimers
-and beyond". The paper is part of the OLS 2006 Proceedings Volume 1, which can
-be found on the OLS website:
-https://www.kernel.org/doc/ols/2006/ols2006v1-pages-333-346.pdf
-
-The slides to this talk are available from:
-http://www.cs.columbia.edu/~nahum/w6998/papers/ols2006-hrtimers-slides.pdf
-
-The slides contain five figures (pages 2, 15, 18, 20, 22), which illustrate the
-changes in the time(r) related Linux subsystems. Figure #1 (p. 2) shows the
-design of the Linux time(r) system before hrtimers and other building blocks
-got merged into mainline.
-
-Note: the paper and the slides are talking about "clock event source", while we
-switched to the name "clock event devices" in meantime.
-
-The design contains the following basic building blocks:
-
-- hrtimer base infrastructure
-- timeofday and clock source management
-- clock event management
-- high resolution timer functionality
-- dynamic ticks
-
-
-hrtimer base infrastructure
----------------------------
-
-The hrtimer base infrastructure was merged into the 2.6.16 kernel. Details of
-the base implementation are covered in Documentation/timers/hrtimers.txt. See
-also figure #2 (OLS slides p. 15)
-
-The main differences to the timer wheel, which holds the armed timer_list type
-timers are:
-       - time ordered enqueueing into a rb-tree
-       - independent of ticks (the processing is based on nanoseconds)
-
-
-timeofday and clock source management
--------------------------------------
-
-John Stultz's Generic Time Of Day (GTOD) framework moves a large portion of
-code out of the architecture-specific areas into a generic management
-framework, as illustrated in figure #3 (OLS slides p. 18). The architecture
-specific portion is reduced to the low level hardware details of the clock
-sources, which are registered in the framework and selected on a quality based
-decision. The low level code provides hardware setup and readout routines and
-initializes data structures, which are used by the generic time keeping code to
-convert the clock ticks to nanosecond based time values. All other time keeping
-related functionality is moved into the generic code. The GTOD base patch got
-merged into the 2.6.18 kernel.
-
-Further information about the Generic Time Of Day framework is available in the
-OLS 2005 Proceedings Volume 1:
-http://www.linuxsymposium.org/2005/linuxsymposium_procv1.pdf
-
-The paper "We Are Not Getting Any Younger: A New Approach to Time and
-Timers" was written by J. Stultz, D.V. Hart, & N. Aravamudan.
-
-Figure #3 (OLS slides p.18) illustrates the transformation.
-
-
-clock event management
-----------------------
-
-While clock sources provide read access to the monotonically increasing time
-value, clock event devices are used to schedule the next event
-interrupt(s). The next event is currently defined to be periodic, with its
-period defined at compile time. The setup and selection of the event device
-for various event driven functionalities is hardwired into the architecture
-dependent code. This results in duplicated code across all architectures and
-makes it extremely difficult to change the configuration of the system to use
-event interrupt devices other than those already built into the
-architecture. Another implication of the current design is that it is necessary
-to touch all the architecture-specific implementations in order to provide new
-functionality like high resolution timers or dynamic ticks.
-
-The clock events subsystem tries to address this problem by providing a generic
-solution to manage clock event devices and their usage for the various clock
-event driven kernel functionalities. The goal of the clock event subsystem is
-to minimize the clock event related architecture dependent code to the pure
-hardware related handling and to allow easy addition and utilization of new
-clock event devices. It also minimizes the duplicated code across the
-architectures as it provides generic functionality down to the interrupt
-service handler, which is almost inherently hardware dependent.
-
-Clock event devices are registered either by the architecture dependent boot
-code or at module insertion time. Each clock event device fills a data
-structure with clock-specific property parameters and callback functions. The
-clock event management decides, by using the specified property parameters, the
-set of system functions a clock event device will be used to support. This
-includes the distinction of per-CPU and per-system global event devices.
-
-System-level global event devices are used for the Linux periodic tick. Per-CPU
-event devices are used to provide local CPU functionality such as process
-accounting, profiling, and high resolution timers.
-
-The management layer assigns one or more of the following functions to a clock
-event device:
-      - system global periodic tick (jiffies update)
-      - cpu local update_process_times
-      - cpu local profiling
-      - cpu local next event interrupt (non periodic mode)
-
-The clock event device delegates the selection of those timer interrupt related
-functions completely to the management layer. The clock management layer stores
-a function pointer in the device description structure, which has to be called
-from the hardware level handler. This removes a lot of duplicated code from the
-architecture specific timer interrupt handlers and hands the control over the
-clock event devices and the assignment of timer interrupt related functionality
-to the core code.
-
-The clock event layer API is rather small. Aside from the clock event device
-registration interface it provides functions to schedule the next event
-interrupt, clock event device notification service and support for suspend and
-resume.
-
-The framework adds about 700 lines of code which results in a 2KB increase of
-the kernel binary size. The conversion of i386 removes about 100 lines of
-code. The binary size decrease is in the range of 400 byte. We believe that the
-increase of flexibility and the avoidance of duplicated code across
-architectures justifies the slight increase of the binary size.
-
-The conversion of an architecture has no functional impact, but allows to
-utilize the high resolution and dynamic tick functionalities without any change
-to the clock event device and timer interrupt code. After the conversion the
-enabling of high resolution timers and dynamic ticks is simply provided by
-adding the kernel/time/Kconfig file to the architecture specific Kconfig and
-adding the dynamic tick specific calls to the idle routine (a total of 3 lines
-added to the idle function and the Kconfig file)
-
-Figure #4 (OLS slides p.20) illustrates the transformation.
-
-
-high resolution timer functionality
------------------------------------
-
-During system boot it is not possible to use the high resolution timer
-functionality, while making it possible would be difficult and would serve no
-useful function. The initialization of the clock event device framework, the
-clock source framework (GTOD) and hrtimers itself has to be done and
-appropriate clock sources and clock event devices have to be registered before
-the high resolution functionality can work. Up to the point where hrtimers are
-initialized, the system works in the usual low resolution periodic mode. The
-clock source and the clock event device layers provide notification functions
-which inform hrtimers about availability of new hardware. hrtimers validates
-the usability of the registered clock sources and clock event devices before
-switching to high resolution mode. This ensures also that a kernel which is
-configured for high resolution timers can run on a system which lacks the
-necessary hardware support.
-
-The high resolution timer code does not support SMP machines which have only
-global clock event devices. The support of such hardware would involve IPI
-calls when an interrupt happens. The overhead would be much larger than the
-benefit. This is the reason why we currently disable high resolution and
-dynamic ticks on i386 SMP systems which stop the local APIC in C3 power
-state. A workaround is available as an idea, but the problem has not been
-tackled yet.
-
-The time ordered insertion of timers provides all the infrastructure to decide
-whether the event device has to be reprogrammed when a timer is added. The
-decision is made per timer base and synchronized across per-cpu timer bases in
-a support function. The design allows the system to utilize separate per-CPU
-clock event devices for the per-CPU timer bases, but currently only one
-reprogrammable clock event device per-CPU is utilized.
-
-When the timer interrupt happens, the next event interrupt handler is called
-from the clock event distribution code and moves expired timers from the
-red-black tree to a separate double linked list and invokes the softirq
-handler. An additional mode field in the hrtimer structure allows the system to
-execute callback functions directly from the next event interrupt handler. This
-is restricted to code which can safely be executed in the hard interrupt
-context. This applies, for example, to the common case of a wakeup function as
-used by nanosleep. The advantage of executing the handler in the interrupt
-context is the avoidance of up to two context switches - from the interrupted
-context to the softirq and to the task which is woken up by the expired
-timer.
-
-Once a system has switched to high resolution mode, the periodic tick is
-switched off. This disables the per system global periodic clock event device -
-e.g. the PIT on i386 SMP systems.
-
-The periodic tick functionality is provided by an per-cpu hrtimer. The callback
-function is executed in the next event interrupt context and updates jiffies
-and calls update_process_times and profiling. The implementation of the hrtimer
-based periodic tick is designed to be extended with dynamic tick functionality.
-This allows to use a single clock event device to schedule high resolution
-timer and periodic events (jiffies tick, profiling, process accounting) on UP
-systems. This has been proved to work with the PIT on i386 and the Incrementer
-on PPC.
-
-The softirq for running the hrtimer queues and executing the callbacks has been
-separated from the tick bound timer softirq to allow accurate delivery of high
-resolution timer signals which are used by itimer and POSIX interval
-timers. The execution of this softirq can still be delayed by other softirqs,
-but the overall latencies have been significantly improved by this separation.
-
-Figure #5 (OLS slides p.22) illustrates the transformation.
-
-
-dynamic ticks
--------------
-
-Dynamic ticks are the logical consequence of the hrtimer based periodic tick
-replacement (sched_tick). The functionality of the sched_tick hrtimer is
-extended by three functions:
-
-- hrtimer_stop_sched_tick
-- hrtimer_restart_sched_tick
-- hrtimer_update_jiffies
-
-hrtimer_stop_sched_tick() is called when a CPU goes into idle state. The code
-evaluates the next scheduled timer event (from both hrtimers and the timer
-wheel) and in case that the next event is further away than the next tick it
-reprograms the sched_tick to this future event, to allow longer idle sleeps
-without worthless interruption by the periodic tick. The function is also
-called when an interrupt happens during the idle period, which does not cause a
-reschedule. The call is necessary as the interrupt handler might have armed a
-new timer whose expiry time is before the time which was identified as the
-nearest event in the previous call to hrtimer_stop_sched_tick.
-
-hrtimer_restart_sched_tick() is called when the CPU leaves the idle state before
-it calls schedule(). hrtimer_restart_sched_tick() resumes the periodic tick,
-which is kept active until the next call to hrtimer_stop_sched_tick().
-
-hrtimer_update_jiffies() is called from irq_enter() when an interrupt happens
-in the idle period to make sure that jiffies are up to date and the interrupt
-handler has not to deal with an eventually stale jiffy value.
-
-The dynamic tick feature provides statistical values which are exported to
-userspace via /proc/stat and can be made available for enhanced power
-management control.
-
-The implementation leaves room for further development like full tickless
-systems, where the time slice is controlled by the scheduler, variable
-frequency profiling, and a complete removal of jiffies in the future.
-
-
-Aside the current initial submission of i386 support, the patchset has been
-extended to x86_64 and ARM already. Initial (work in progress) support is also
-available for MIPS and PowerPC.
-
-	  Thomas, Ingo
-
-
-
diff --git a/Documentation/timers/hpet.rst b/Documentation/timers/hpet.rst
new file mode 100644
index 000000000000..c9d05d3caaca
--- /dev/null
+++ b/Documentation/timers/hpet.rst
@@ -0,0 +1,30 @@
+===========================================
+High Precision Event Timer Driver for Linux
+===========================================
+
+The High Precision Event Timer (HPET) hardware follows a specification
+by Intel and Microsoft, revision 1.
+
+Each HPET has one fixed-rate counter (at 10+ MHz, hence "High Precision")
+and up to 32 comparators.  Normally three or more comparators are provided,
+each of which can generate oneshot interrupts and at least one of which has
+additional hardware to support periodic interrupts.  The comparators are
+also called "timers", which can be misleading since usually timers are
+independent of each other ... these share a counter, complicating resets.
+
+HPET devices can support two interrupt routing modes.  In one mode, the
+comparators are additional interrupt sources with no particular system
+role.  Many x86 BIOS writers don't route HPET interrupts at all, which
+prevents use of that mode.  They support the other "legacy replacement"
+mode where the first two comparators block interrupts from 8254 timers
+and from the RTC.
+
+The driver supports detection of HPET driver allocation and initialization
+of the HPET before the driver module_init routine is called.  This enables
+platform code which uses timer 0 or 1 as the main timer to intercept HPET
+initialization.  An example of this initialization can be found in
+arch/x86/kernel/hpet.c.
+
+The driver provides a userspace API which resembles the API found in the
+RTC driver framework.  An example user space program is provided in
+file:samples/timers/hpet_example.c
diff --git a/Documentation/timers/hpet.txt b/Documentation/timers/hpet.txt
deleted file mode 100644
index 895345ec513b..000000000000
--- a/Documentation/timers/hpet.txt
+++ /dev/null
@@ -1,28 +0,0 @@
-		High Precision Event Timer Driver for Linux
-
-The High Precision Event Timer (HPET) hardware follows a specification
-by Intel and Microsoft, revision 1.
-
-Each HPET has one fixed-rate counter (at 10+ MHz, hence "High Precision")
-and up to 32 comparators.  Normally three or more comparators are provided,
-each of which can generate oneshot interrupts and at least one of which has
-additional hardware to support periodic interrupts.  The comparators are
-also called "timers", which can be misleading since usually timers are
-independent of each other ... these share a counter, complicating resets.
-
-HPET devices can support two interrupt routing modes.  In one mode, the
-comparators are additional interrupt sources with no particular system
-role.  Many x86 BIOS writers don't route HPET interrupts at all, which
-prevents use of that mode.  They support the other "legacy replacement"
-mode where the first two comparators block interrupts from 8254 timers
-and from the RTC.
-
-The driver supports detection of HPET driver allocation and initialization
-of the HPET before the driver module_init routine is called.  This enables
-platform code which uses timer 0 or 1 as the main timer to intercept HPET
-initialization.  An example of this initialization can be found in
-arch/x86/kernel/hpet.c.
-
-The driver provides a userspace API which resembles the API found in the
-RTC driver framework.  An example user space program is provided in
-file:samples/timers/hpet_example.c
diff --git a/Documentation/timers/hrtimers.rst b/Documentation/timers/hrtimers.rst
new file mode 100644
index 000000000000..c1c20a693e8f
--- /dev/null
+++ b/Documentation/timers/hrtimers.rst
@@ -0,0 +1,178 @@
+======================================================
+hrtimers - subsystem for high-resolution kernel timers
+======================================================
+
+This patch introduces a new subsystem for high-resolution kernel timers.
+
+One might ask the question: we already have a timer subsystem
+(kernel/timers.c), why do we need two timer subsystems? After a lot of
+back and forth trying to integrate high-resolution and high-precision
+features into the existing timer framework, and after testing various
+such high-resolution timer implementations in practice, we came to the
+conclusion that the timer wheel code is fundamentally not suitable for
+such an approach. We initially didn't believe this ('there must be a way
+to solve this'), and spent a considerable effort trying to integrate
+things into the timer wheel, but we failed. In hindsight, there are
+several reasons why such integration is hard/impossible:
+
+- the forced handling of low-resolution and high-resolution timers in
+  the same way leads to a lot of compromises, macro magic and #ifdef
+  mess. The timers.c code is very "tightly coded" around jiffies and
+  32-bitness assumptions, and has been honed and micro-optimized for a
+  relatively narrow use case (jiffies in a relatively narrow HZ range)
+  for many years - and thus even small extensions to it easily break
+  the wheel concept, leading to even worse compromises. The timer wheel
+  code is very good and tight code, there's zero problems with it in its
+  current usage - but it is simply not suitable to be extended for
+  high-res timers.
+
+- the unpredictable [O(N)] overhead of cascading leads to delays which
+  necessitate a more complex handling of high resolution timers, which
+  in turn decreases robustness. Such a design still leads to rather large
+  timing inaccuracies. Cascading is a fundamental property of the timer
+  wheel concept, it cannot be 'designed out' without inevitably
+  degrading other portions of the timers.c code in an unacceptable way.
+
+- the implementation of the current posix-timer subsystem on top of
+  the timer wheel has already introduced a quite complex handling of
+  the required readjusting of absolute CLOCK_REALTIME timers at
+  settimeofday or NTP time - further underlying our experience by
+  example: that the timer wheel data structure is too rigid for high-res
+  timers.
+
+- the timer wheel code is most optimal for use cases which can be
+  identified as "timeouts". Such timeouts are usually set up to cover
+  error conditions in various I/O paths, such as networking and block
+  I/O. The vast majority of those timers never expire and are rarely
+  recascaded because the expected correct event arrives in time so they
+  can be removed from the timer wheel before any further processing of
+  them becomes necessary. Thus the users of these timeouts can accept
+  the granularity and precision tradeoffs of the timer wheel, and
+  largely expect the timer subsystem to have near-zero overhead.
+  Accurate timing for them is not a core purpose - in fact most of the
+  timeout values used are ad-hoc. For them it is at most a necessary
+  evil to guarantee the processing of actual timeout completions
+  (because most of the timeouts are deleted before completion), which
+  should thus be as cheap and unintrusive as possible.
+
+The primary users of precision timers are user-space applications that
+utilize nanosleep, posix-timers and itimer interfaces. Also, in-kernel
+users like drivers and subsystems which require precise timed events
+(e.g. multimedia) can benefit from the availability of a separate
+high-resolution timer subsystem as well.
+
+While this subsystem does not offer high-resolution clock sources just
+yet, the hrtimer subsystem can be easily extended with high-resolution
+clock capabilities, and patches for that exist and are maturing quickly.
+The increasing demand for realtime and multimedia applications along
+with other potential users for precise timers gives another reason to
+separate the "timeout" and "precise timer" subsystems.
+
+Another potential benefit is that such a separation allows even more
+special-purpose optimization of the existing timer wheel for the low
+resolution and low precision use cases - once the precision-sensitive
+APIs are separated from the timer wheel and are migrated over to
+hrtimers. E.g. we could decrease the frequency of the timeout subsystem
+from 250 Hz to 100 HZ (or even smaller).
+
+hrtimer subsystem implementation details
+----------------------------------------
+
+the basic design considerations were:
+
+- simplicity
+
+- data structure not bound to jiffies or any other granularity. All the
+  kernel logic works at 64-bit nanoseconds resolution - no compromises.
+
+- simplification of existing, timing related kernel code
+
+another basic requirement was the immediate enqueueing and ordering of
+timers at activation time. After looking at several possible solutions
+such as radix trees and hashes, we chose the red black tree as the basic
+data structure. Rbtrees are available as a library in the kernel and are
+used in various performance-critical areas of e.g. memory management and
+file systems. The rbtree is solely used for time sorted ordering, while
+a separate list is used to give the expiry code fast access to the
+queued timers, without having to walk the rbtree.
+
+(This separate list is also useful for later when we'll introduce
+high-resolution clocks, where we need separate pending and expired
+queues while keeping the time-order intact.)
+
+Time-ordered enqueueing is not purely for the purposes of
+high-resolution clocks though, it also simplifies the handling of
+absolute timers based on a low-resolution CLOCK_REALTIME. The existing
+implementation needed to keep an extra list of all armed absolute
+CLOCK_REALTIME timers along with complex locking. In case of
+settimeofday and NTP, all the timers (!) had to be dequeued, the
+time-changing code had to fix them up one by one, and all of them had to
+be enqueued again. The time-ordered enqueueing and the storage of the
+expiry time in absolute time units removes all this complex and poorly
+scaling code from the posix-timer implementation - the clock can simply
+be set without having to touch the rbtree. This also makes the handling
+of posix-timers simpler in general.
+
+The locking and per-CPU behavior of hrtimers was mostly taken from the
+existing timer wheel code, as it is mature and well suited. Sharing code
+was not really a win, due to the different data structures. Also, the
+hrtimer functions now have clearer behavior and clearer names - such as
+hrtimer_try_to_cancel() and hrtimer_cancel() [which are roughly
+equivalent to del_timer() and del_timer_sync()] - so there's no direct
+1:1 mapping between them on the algorithmic level, and thus no real
+potential for code sharing either.
+
+Basic data types: every time value, absolute or relative, is in a
+special nanosecond-resolution type: ktime_t. The kernel-internal
+representation of ktime_t values and operations is implemented via
+macros and inline functions, and can be switched between a "hybrid
+union" type and a plain "scalar" 64bit nanoseconds representation (at
+compile time). The hybrid union type optimizes time conversions on 32bit
+CPUs. This build-time-selectable ktime_t storage format was implemented
+to avoid the performance impact of 64-bit multiplications and divisions
+on 32bit CPUs. Such operations are frequently necessary to convert
+between the storage formats provided by kernel and userspace interfaces
+and the internal time format. (See include/linux/ktime.h for further
+details.)
+
+hrtimers - rounding of timer values
+-----------------------------------
+
+the hrtimer code will round timer events to lower-resolution clocks
+because it has to. Otherwise it will do no artificial rounding at all.
+
+one question is, what resolution value should be returned to the user by
+the clock_getres() interface. This will return whatever real resolution
+a given clock has - be it low-res, high-res, or artificially-low-res.
+
+hrtimers - testing and verification
+-----------------------------------
+
+We used the high-resolution clock subsystem ontop of hrtimers to verify
+the hrtimer implementation details in praxis, and we also ran the posix
+timer tests in order to ensure specification compliance. We also ran
+tests on low-resolution clocks.
+
+The hrtimer patch converts the following kernel functionality to use
+hrtimers:
+
+ - nanosleep
+ - itimers
+ - posix-timers
+
+The conversion of nanosleep and posix-timers enabled the unification of
+nanosleep and clock_nanosleep.
+
+The code was successfully compiled for the following platforms:
+
+ i386, x86_64, ARM, PPC, PPC64, IA64
+
+The code was run-tested on the following platforms:
+
+ i386(UP/SMP), x86_64(UP/SMP), ARM, PPC
+
+hrtimers were also integrated into the -rt tree, along with a
+hrtimers-based high-resolution clock implementation, so the hrtimers
+code got a healthy amount of testing and use in practice.
+
+	Thomas Gleixner, Ingo Molnar
diff --git a/Documentation/timers/hrtimers.txt b/Documentation/timers/hrtimers.txt
deleted file mode 100644
index 588d85724f10..000000000000
--- a/Documentation/timers/hrtimers.txt
+++ /dev/null
@@ -1,178 +0,0 @@
-
-hrtimers - subsystem for high-resolution kernel timers
-----------------------------------------------------
-
-This patch introduces a new subsystem for high-resolution kernel timers.
-
-One might ask the question: we already have a timer subsystem
-(kernel/timers.c), why do we need two timer subsystems? After a lot of
-back and forth trying to integrate high-resolution and high-precision
-features into the existing timer framework, and after testing various
-such high-resolution timer implementations in practice, we came to the
-conclusion that the timer wheel code is fundamentally not suitable for
-such an approach. We initially didn't believe this ('there must be a way
-to solve this'), and spent a considerable effort trying to integrate
-things into the timer wheel, but we failed. In hindsight, there are
-several reasons why such integration is hard/impossible:
-
-- the forced handling of low-resolution and high-resolution timers in
-  the same way leads to a lot of compromises, macro magic and #ifdef
-  mess. The timers.c code is very "tightly coded" around jiffies and
-  32-bitness assumptions, and has been honed and micro-optimized for a
-  relatively narrow use case (jiffies in a relatively narrow HZ range)
-  for many years - and thus even small extensions to it easily break
-  the wheel concept, leading to even worse compromises. The timer wheel
-  code is very good and tight code, there's zero problems with it in its
-  current usage - but it is simply not suitable to be extended for
-  high-res timers.
-
-- the unpredictable [O(N)] overhead of cascading leads to delays which
-  necessitate a more complex handling of high resolution timers, which
-  in turn decreases robustness. Such a design still leads to rather large
-  timing inaccuracies. Cascading is a fundamental property of the timer
-  wheel concept, it cannot be 'designed out' without inevitably
-  degrading other portions of the timers.c code in an unacceptable way.
-
-- the implementation of the current posix-timer subsystem on top of
-  the timer wheel has already introduced a quite complex handling of
-  the required readjusting of absolute CLOCK_REALTIME timers at
-  settimeofday or NTP time - further underlying our experience by
-  example: that the timer wheel data structure is too rigid for high-res
-  timers.
-
-- the timer wheel code is most optimal for use cases which can be
-  identified as "timeouts". Such timeouts are usually set up to cover
-  error conditions in various I/O paths, such as networking and block
-  I/O. The vast majority of those timers never expire and are rarely
-  recascaded because the expected correct event arrives in time so they
-  can be removed from the timer wheel before any further processing of
-  them becomes necessary. Thus the users of these timeouts can accept
-  the granularity and precision tradeoffs of the timer wheel, and
-  largely expect the timer subsystem to have near-zero overhead.
-  Accurate timing for them is not a core purpose - in fact most of the
-  timeout values used are ad-hoc. For them it is at most a necessary
-  evil to guarantee the processing of actual timeout completions
-  (because most of the timeouts are deleted before completion), which
-  should thus be as cheap and unintrusive as possible.
-
-The primary users of precision timers are user-space applications that
-utilize nanosleep, posix-timers and itimer interfaces. Also, in-kernel
-users like drivers and subsystems which require precise timed events
-(e.g. multimedia) can benefit from the availability of a separate
-high-resolution timer subsystem as well.
-
-While this subsystem does not offer high-resolution clock sources just
-yet, the hrtimer subsystem can be easily extended with high-resolution
-clock capabilities, and patches for that exist and are maturing quickly.
-The increasing demand for realtime and multimedia applications along
-with other potential users for precise timers gives another reason to
-separate the "timeout" and "precise timer" subsystems.
-
-Another potential benefit is that such a separation allows even more
-special-purpose optimization of the existing timer wheel for the low
-resolution and low precision use cases - once the precision-sensitive
-APIs are separated from the timer wheel and are migrated over to
-hrtimers. E.g. we could decrease the frequency of the timeout subsystem
-from 250 Hz to 100 HZ (or even smaller).
-
-hrtimer subsystem implementation details
-----------------------------------------
-
-the basic design considerations were:
-
-- simplicity
-
-- data structure not bound to jiffies or any other granularity. All the
-  kernel logic works at 64-bit nanoseconds resolution - no compromises.
-
-- simplification of existing, timing related kernel code
-
-another basic requirement was the immediate enqueueing and ordering of
-timers at activation time. After looking at several possible solutions
-such as radix trees and hashes, we chose the red black tree as the basic
-data structure. Rbtrees are available as a library in the kernel and are
-used in various performance-critical areas of e.g. memory management and
-file systems. The rbtree is solely used for time sorted ordering, while
-a separate list is used to give the expiry code fast access to the
-queued timers, without having to walk the rbtree.
-
-(This separate list is also useful for later when we'll introduce
-high-resolution clocks, where we need separate pending and expired
-queues while keeping the time-order intact.)
-
-Time-ordered enqueueing is not purely for the purposes of
-high-resolution clocks though, it also simplifies the handling of
-absolute timers based on a low-resolution CLOCK_REALTIME. The existing
-implementation needed to keep an extra list of all armed absolute
-CLOCK_REALTIME timers along with complex locking. In case of
-settimeofday and NTP, all the timers (!) had to be dequeued, the
-time-changing code had to fix them up one by one, and all of them had to
-be enqueued again. The time-ordered enqueueing and the storage of the
-expiry time in absolute time units removes all this complex and poorly
-scaling code from the posix-timer implementation - the clock can simply
-be set without having to touch the rbtree. This also makes the handling
-of posix-timers simpler in general.
-
-The locking and per-CPU behavior of hrtimers was mostly taken from the
-existing timer wheel code, as it is mature and well suited. Sharing code
-was not really a win, due to the different data structures. Also, the
-hrtimer functions now have clearer behavior and clearer names - such as
-hrtimer_try_to_cancel() and hrtimer_cancel() [which are roughly
-equivalent to del_timer() and del_timer_sync()] - so there's no direct
-1:1 mapping between them on the algorithmic level, and thus no real
-potential for code sharing either.
-
-Basic data types: every time value, absolute or relative, is in a
-special nanosecond-resolution type: ktime_t. The kernel-internal
-representation of ktime_t values and operations is implemented via
-macros and inline functions, and can be switched between a "hybrid
-union" type and a plain "scalar" 64bit nanoseconds representation (at
-compile time). The hybrid union type optimizes time conversions on 32bit
-CPUs. This build-time-selectable ktime_t storage format was implemented
-to avoid the performance impact of 64-bit multiplications and divisions
-on 32bit CPUs. Such operations are frequently necessary to convert
-between the storage formats provided by kernel and userspace interfaces
-and the internal time format. (See include/linux/ktime.h for further
-details.)
-
-hrtimers - rounding of timer values
------------------------------------
-
-the hrtimer code will round timer events to lower-resolution clocks
-because it has to. Otherwise it will do no artificial rounding at all.
-
-one question is, what resolution value should be returned to the user by
-the clock_getres() interface. This will return whatever real resolution
-a given clock has - be it low-res, high-res, or artificially-low-res.
-
-hrtimers - testing and verification
-----------------------------------
-
-We used the high-resolution clock subsystem ontop of hrtimers to verify
-the hrtimer implementation details in praxis, and we also ran the posix
-timer tests in order to ensure specification compliance. We also ran
-tests on low-resolution clocks.
-
-The hrtimer patch converts the following kernel functionality to use
-hrtimers:
-
- - nanosleep
- - itimers
- - posix-timers
-
-The conversion of nanosleep and posix-timers enabled the unification of
-nanosleep and clock_nanosleep.
-
-The code was successfully compiled for the following platforms:
-
- i386, x86_64, ARM, PPC, PPC64, IA64
-
-The code was run-tested on the following platforms:
-
- i386(UP/SMP), x86_64(UP/SMP), ARM, PPC
-
-hrtimers were also integrated into the -rt tree, along with a
-hrtimers-based high-resolution clock implementation, so the hrtimers
-code got a healthy amount of testing and use in practice.
-
-	Thomas Gleixner, Ingo Molnar
diff --git a/Documentation/timers/index.rst b/Documentation/timers/index.rst
new file mode 100644
index 000000000000..91f6f8263c48
--- /dev/null
+++ b/Documentation/timers/index.rst
@@ -0,0 +1,22 @@
+:orphan:
+
+======
+timers
+======
+
+.. toctree::
+    :maxdepth: 1
+
+    highres
+    hpet
+    hrtimers
+    no_hz
+    timekeeping
+    timers-howto
+
+.. only::  subproject and html
+
+   Indices
+   =======
+
+   * :ref:`genindex`
diff --git a/Documentation/timers/no_hz.rst b/Documentation/timers/no_hz.rst
new file mode 100644
index 000000000000..065db217cb04
--- /dev/null
+++ b/Documentation/timers/no_hz.rst
@@ -0,0 +1,326 @@
+======================================
+NO_HZ: Reducing Scheduling-Clock Ticks
+======================================
+
+
+This document describes Kconfig options and boot parameters that can
+reduce the number of scheduling-clock interrupts, thereby improving energy
+efficiency and reducing OS jitter.  Reducing OS jitter is important for
+some types of computationally intensive high-performance computing (HPC)
+applications and for real-time applications.
+
+There are three main ways of managing scheduling-clock interrupts
+(also known as "scheduling-clock ticks" or simply "ticks"):
+
+1.	Never omit scheduling-clock ticks (CONFIG_HZ_PERIODIC=y or
+	CONFIG_NO_HZ=n for older kernels).  You normally will -not-
+	want to choose this option.
+
+2.	Omit scheduling-clock ticks on idle CPUs (CONFIG_NO_HZ_IDLE=y or
+	CONFIG_NO_HZ=y for older kernels).  This is the most common
+	approach, and should be the default.
+
+3.	Omit scheduling-clock ticks on CPUs that are either idle or that
+	have only one runnable task (CONFIG_NO_HZ_FULL=y).  Unless you
+	are running realtime applications or certain types of HPC
+	workloads, you will normally -not- want this option.
+
+These three cases are described in the following three sections, followed
+by a third section on RCU-specific considerations, a fourth section
+discussing testing, and a fifth and final section listing known issues.
+
+
+Never Omit Scheduling-Clock Ticks
+=================================
+
+Very old versions of Linux from the 1990s and the very early 2000s
+are incapable of omitting scheduling-clock ticks.  It turns out that
+there are some situations where this old-school approach is still the
+right approach, for example, in heavy workloads with lots of tasks
+that use short bursts of CPU, where there are very frequent idle
+periods, but where these idle periods are also quite short (tens or
+hundreds of microseconds).  For these types of workloads, scheduling
+clock interrupts will normally be delivered any way because there
+will frequently be multiple runnable tasks per CPU.  In these cases,
+attempting to turn off the scheduling clock interrupt will have no effect
+other than increasing the overhead of switching to and from idle and
+transitioning between user and kernel execution.
+
+This mode of operation can be selected using CONFIG_HZ_PERIODIC=y (or
+CONFIG_NO_HZ=n for older kernels).
+
+However, if you are instead running a light workload with long idle
+periods, failing to omit scheduling-clock interrupts will result in
+excessive power consumption.  This is especially bad on battery-powered
+devices, where it results in extremely short battery lifetimes.  If you
+are running light workloads, you should therefore read the following
+section.
+
+In addition, if you are running either a real-time workload or an HPC
+workload with short iterations, the scheduling-clock interrupts can
+degrade your applications performance.  If this describes your workload,
+you should read the following two sections.
+
+
+Omit Scheduling-Clock Ticks For Idle CPUs
+=========================================
+
+If a CPU is idle, there is little point in sending it a scheduling-clock
+interrupt.  After all, the primary purpose of a scheduling-clock interrupt
+is to force a busy CPU to shift its attention among multiple duties,
+and an idle CPU has no duties to shift its attention among.
+
+The CONFIG_NO_HZ_IDLE=y Kconfig option causes the kernel to avoid sending
+scheduling-clock interrupts to idle CPUs, which is critically important
+both to battery-powered devices and to highly virtualized mainframes.
+A battery-powered device running a CONFIG_HZ_PERIODIC=y kernel would
+drain its battery very quickly, easily 2-3 times as fast as would the
+same device running a CONFIG_NO_HZ_IDLE=y kernel.  A mainframe running
+1,500 OS instances might find that half of its CPU time was consumed by
+unnecessary scheduling-clock interrupts.  In these situations, there
+is strong motivation to avoid sending scheduling-clock interrupts to
+idle CPUs.  That said, dyntick-idle mode is not free:
+
+1.	It increases the number of instructions executed on the path
+	to and from the idle loop.
+
+2.	On many architectures, dyntick-idle mode also increases the
+	number of expensive clock-reprogramming operations.
+
+Therefore, systems with aggressive real-time response constraints often
+run CONFIG_HZ_PERIODIC=y kernels (or CONFIG_NO_HZ=n for older kernels)
+in order to avoid degrading from-idle transition latencies.
+
+An idle CPU that is not receiving scheduling-clock interrupts is said to
+be "dyntick-idle", "in dyntick-idle mode", "in nohz mode", or "running
+tickless".  The remainder of this document will use "dyntick-idle mode".
+
+There is also a boot parameter "nohz=" that can be used to disable
+dyntick-idle mode in CONFIG_NO_HZ_IDLE=y kernels by specifying "nohz=off".
+By default, CONFIG_NO_HZ_IDLE=y kernels boot with "nohz=on", enabling
+dyntick-idle mode.
+
+
+Omit Scheduling-Clock Ticks For CPUs With Only One Runnable Task
+================================================================
+
+If a CPU has only one runnable task, there is little point in sending it
+a scheduling-clock interrupt because there is no other task to switch to.
+Note that omitting scheduling-clock ticks for CPUs with only one runnable
+task implies also omitting them for idle CPUs.
+
+The CONFIG_NO_HZ_FULL=y Kconfig option causes the kernel to avoid
+sending scheduling-clock interrupts to CPUs with a single runnable task,
+and such CPUs are said to be "adaptive-ticks CPUs".  This is important
+for applications with aggressive real-time response constraints because
+it allows them to improve their worst-case response times by the maximum
+duration of a scheduling-clock interrupt.  It is also important for
+computationally intensive short-iteration workloads:  If any CPU is
+delayed during a given iteration, all the other CPUs will be forced to
+wait idle while the delayed CPU finishes.  Thus, the delay is multiplied
+by one less than the number of CPUs.  In these situations, there is
+again strong motivation to avoid sending scheduling-clock interrupts.
+
+By default, no CPU will be an adaptive-ticks CPU.  The "nohz_full="
+boot parameter specifies the adaptive-ticks CPUs.  For example,
+"nohz_full=1,6-8" says that CPUs 1, 6, 7, and 8 are to be adaptive-ticks
+CPUs.  Note that you are prohibited from marking all of the CPUs as
+adaptive-tick CPUs:  At least one non-adaptive-tick CPU must remain
+online to handle timekeeping tasks in order to ensure that system
+calls like gettimeofday() returns accurate values on adaptive-tick CPUs.
+(This is not an issue for CONFIG_NO_HZ_IDLE=y because there are no running
+user processes to observe slight drifts in clock rate.)  Therefore, the
+boot CPU is prohibited from entering adaptive-ticks mode.  Specifying a
+"nohz_full=" mask that includes the boot CPU will result in a boot-time
+error message, and the boot CPU will be removed from the mask.  Note that
+this means that your system must have at least two CPUs in order for
+CONFIG_NO_HZ_FULL=y to do anything for you.
+
+Finally, adaptive-ticks CPUs must have their RCU callbacks offloaded.
+This is covered in the "RCU IMPLICATIONS" section below.
+
+Normally, a CPU remains in adaptive-ticks mode as long as possible.
+In particular, transitioning to kernel mode does not automatically change
+the mode.  Instead, the CPU will exit adaptive-ticks mode only if needed,
+for example, if that CPU enqueues an RCU callback.
+
+Just as with dyntick-idle mode, the benefits of adaptive-tick mode do
+not come for free:
+
+1.	CONFIG_NO_HZ_FULL selects CONFIG_NO_HZ_COMMON, so you cannot run
+	adaptive ticks without also running dyntick idle.  This dependency
+	extends down into the implementation, so that all of the costs
+	of CONFIG_NO_HZ_IDLE are also incurred by CONFIG_NO_HZ_FULL.
+
+2.	The user/kernel transitions are slightly more expensive due
+	to the need to inform kernel subsystems (such as RCU) about
+	the change in mode.
+
+3.	POSIX CPU timers prevent CPUs from entering adaptive-tick mode.
+	Real-time applications needing to take actions based on CPU time
+	consumption need to use other means of doing so.
+
+4.	If there are more perf events pending than the hardware can
+	accommodate, they are normally round-robined so as to collect
+	all of them over time.  Adaptive-tick mode may prevent this
+	round-robining from happening.  This will likely be fixed by
+	preventing CPUs with large numbers of perf events pending from
+	entering adaptive-tick mode.
+
+5.	Scheduler statistics for adaptive-tick CPUs may be computed
+	slightly differently than those for non-adaptive-tick CPUs.
+	This might in turn perturb load-balancing of real-time tasks.
+
+6.	The LB_BIAS scheduler feature is disabled by adaptive ticks.
+
+Although improvements are expected over time, adaptive ticks is quite
+useful for many types of real-time and compute-intensive applications.
+However, the drawbacks listed above mean that adaptive ticks should not
+(yet) be enabled by default.
+
+
+RCU Implications
+================
+
+There are situations in which idle CPUs cannot be permitted to
+enter either dyntick-idle mode or adaptive-tick mode, the most
+common being when that CPU has RCU callbacks pending.
+
+The CONFIG_RCU_FAST_NO_HZ=y Kconfig option may be used to cause such CPUs
+to enter dyntick-idle mode or adaptive-tick mode anyway.  In this case,
+a timer will awaken these CPUs every four jiffies in order to ensure
+that the RCU callbacks are processed in a timely fashion.
+
+Another approach is to offload RCU callback processing to "rcuo" kthreads
+using the CONFIG_RCU_NOCB_CPU=y Kconfig option.  The specific CPUs to
+offload may be selected using The "rcu_nocbs=" kernel boot parameter,
+which takes a comma-separated list of CPUs and CPU ranges, for example,
+"1,3-5" selects CPUs 1, 3, 4, and 5.
+
+The offloaded CPUs will never queue RCU callbacks, and therefore RCU
+never prevents offloaded CPUs from entering either dyntick-idle mode
+or adaptive-tick mode.  That said, note that it is up to userspace to
+pin the "rcuo" kthreads to specific CPUs if desired.  Otherwise, the
+scheduler will decide where to run them, which might or might not be
+where you want them to run.
+
+
+Testing
+=======
+
+So you enable all the OS-jitter features described in this document,
+but do not see any change in your workload's behavior.  Is this because
+your workload isn't affected that much by OS jitter, or is it because
+something else is in the way?  This section helps answer this question
+by providing a simple OS-jitter test suite, which is available on branch
+master of the following git archive:
+
+git://git.kernel.org/pub/scm/linux/kernel/git/frederic/dynticks-testing.git
+
+Clone this archive and follow the instructions in the README file.
+This test procedure will produce a trace that will allow you to evaluate
+whether or not you have succeeded in removing OS jitter from your system.
+If this trace shows that you have removed OS jitter as much as is
+possible, then you can conclude that your workload is not all that
+sensitive to OS jitter.
+
+Note: this test requires that your system have at least two CPUs.
+We do not currently have a good way to remove OS jitter from single-CPU
+systems.
+
+
+Known Issues
+============
+
+*	Dyntick-idle slows transitions to and from idle slightly.
+	In practice, this has not been a problem except for the most
+	aggressive real-time workloads, which have the option of disabling
+	dyntick-idle mode, an option that most of them take.  However,
+	some workloads will no doubt want to use adaptive ticks to
+	eliminate scheduling-clock interrupt latencies.  Here are some
+	options for these workloads:
+
+	a.	Use PMQOS from userspace to inform the kernel of your
+		latency requirements (preferred).
+
+	b.	On x86 systems, use the "idle=mwait" boot parameter.
+
+	c.	On x86 systems, use the "intel_idle.max_cstate=" to limit
+	`	the maximum C-state depth.
+
+	d.	On x86 systems, use the "idle=poll" boot parameter.
+		However, please note that use of this parameter can cause
+		your CPU to overheat, which may cause thermal throttling
+		to degrade your latencies -- and that this degradation can
+		be even worse than that of dyntick-idle.  Furthermore,
+		this parameter effectively disables Turbo Mode on Intel
+		CPUs, which can significantly reduce maximum performance.
+
+*	Adaptive-ticks slows user/kernel transitions slightly.
+	This is not expected to be a problem for computationally intensive
+	workloads, which have few such transitions.  Careful benchmarking
+	will be required to determine whether or not other workloads
+	are significantly affected by this effect.
+
+*	Adaptive-ticks does not do anything unless there is only one
+	runnable task for a given CPU, even though there are a number
+	of other situations where the scheduling-clock tick is not
+	needed.  To give but one example, consider a CPU that has one
+	runnable high-priority SCHED_FIFO task and an arbitrary number
+	of low-priority SCHED_OTHER tasks.  In this case, the CPU is
+	required to run the SCHED_FIFO task until it either blocks or
+	some other higher-priority task awakens on (or is assigned to)
+	this CPU, so there is no point in sending a scheduling-clock
+	interrupt to this CPU.	However, the current implementation
+	nevertheless sends scheduling-clock interrupts to CPUs having a
+	single runnable SCHED_FIFO task and multiple runnable SCHED_OTHER
+	tasks, even though these interrupts are unnecessary.
+
+	And even when there are multiple runnable tasks on a given CPU,
+	there is little point in interrupting that CPU until the current
+	running task's timeslice expires, which is almost always way
+	longer than the time of the next scheduling-clock interrupt.
+
+	Better handling of these sorts of situations is future work.
+
+*	A reboot is required to reconfigure both adaptive idle and RCU
+	callback offloading.  Runtime reconfiguration could be provided
+	if needed, however, due to the complexity of reconfiguring RCU at
+	runtime, there would need to be an earthshakingly good reason.
+	Especially given that you have the straightforward option of
+	simply offloading RCU callbacks from all CPUs and pinning them
+	where you want them whenever you want them pinned.
+
+*	Additional configuration is required to deal with other sources
+	of OS jitter, including interrupts and system-utility tasks
+	and processes.  This configuration normally involves binding
+	interrupts and tasks to particular CPUs.
+
+*	Some sources of OS jitter can currently be eliminated only by
+	constraining the workload.  For example, the only way to eliminate
+	OS jitter due to global TLB shootdowns is to avoid the unmapping
+	operations (such as kernel module unload operations) that
+	result in these shootdowns.  For another example, page faults
+	and TLB misses can be reduced (and in some cases eliminated) by
+	using huge pages and by constraining the amount of memory used
+	by the application.  Pre-faulting the working set can also be
+	helpful, especially when combined with the mlock() and mlockall()
+	system calls.
+
+*	Unless all CPUs are idle, at least one CPU must keep the
+	scheduling-clock interrupt going in order to support accurate
+	timekeeping.
+
+*	If there might potentially be some adaptive-ticks CPUs, there
+	will be at least one CPU keeping the scheduling-clock interrupt
+	going, even if all CPUs are otherwise idle.
+
+	Better handling of this situation is ongoing work.
+
+*	Some process-handling operations still require the occasional
+	scheduling-clock tick.	These operations include calculating CPU
+	load, maintaining sched average, computing CFS entity vruntime,
+	computing avenrun, and carrying out load balancing.  They are
+	currently accommodated by scheduling-clock tick every second
+	or so.	On-going work will eliminate the need even for these
+	infrequent scheduling-clock ticks.
diff --git a/Documentation/timers/timekeeping.rst b/Documentation/timers/timekeeping.rst
new file mode 100644
index 000000000000..f83e98852e2c
--- /dev/null
+++ b/Documentation/timers/timekeeping.rst
@@ -0,0 +1,180 @@
+===========================================================
+Clock sources, Clock events, sched_clock() and delay timers
+===========================================================
+
+This document tries to briefly explain some basic kernel timekeeping
+abstractions. It partly pertains to the drivers usually found in
+drivers/clocksource in the kernel tree, but the code may be spread out
+across the kernel.
+
+If you grep through the kernel source you will find a number of architecture-
+specific implementations of clock sources, clockevents and several likewise
+architecture-specific overrides of the sched_clock() function and some
+delay timers.
+
+To provide timekeeping for your platform, the clock source provides
+the basic timeline, whereas clock events shoot interrupts on certain points
+on this timeline, providing facilities such as high-resolution timers.
+sched_clock() is used for scheduling and timestamping, and delay timers
+provide an accurate delay source using hardware counters.
+
+
+Clock sources
+-------------
+
+The purpose of the clock source is to provide a timeline for the system that
+tells you where you are in time. For example issuing the command 'date' on
+a Linux system will eventually read the clock source to determine exactly
+what time it is.
+
+Typically the clock source is a monotonic, atomic counter which will provide
+n bits which count from 0 to (2^n)-1 and then wraps around to 0 and start over.
+It will ideally NEVER stop ticking as long as the system is running. It
+may stop during system suspend.
+
+The clock source shall have as high resolution as possible, and the frequency
+shall be as stable and correct as possible as compared to a real-world wall
+clock. It should not move unpredictably back and forth in time or miss a few
+cycles here and there.
+
+It must be immune to the kind of effects that occur in hardware where e.g.
+the counter register is read in two phases on the bus lowest 16 bits first
+and the higher 16 bits in a second bus cycle with the counter bits
+potentially being updated in between leading to the risk of very strange
+values from the counter.
+
+When the wall-clock accuracy of the clock source isn't satisfactory, there
+are various quirks and layers in the timekeeping code for e.g. synchronizing
+the user-visible time to RTC clocks in the system or against networked time
+servers using NTP, but all they do basically is update an offset against
+the clock source, which provides the fundamental timeline for the system.
+These measures does not affect the clock source per se, they only adapt the
+system to the shortcomings of it.
+
+The clock source struct shall provide means to translate the provided counter
+into a nanosecond value as an unsigned long long (unsigned 64 bit) number.
+Since this operation may be invoked very often, doing this in a strict
+mathematical sense is not desirable: instead the number is taken as close as
+possible to a nanosecond value using only the arithmetic operations
+multiply and shift, so in clocksource_cyc2ns() you find:
+
+  ns ~= (clocksource * mult) >> shift
+
+You will find a number of helper functions in the clock source code intended
+to aid in providing these mult and shift values, such as
+clocksource_khz2mult(), clocksource_hz2mult() that help determine the
+mult factor from a fixed shift, and clocksource_register_hz() and
+clocksource_register_khz() which will help out assigning both shift and mult
+factors using the frequency of the clock source as the only input.
+
+For real simple clock sources accessed from a single I/O memory location
+there is nowadays even clocksource_mmio_init() which will take a memory
+location, bit width, a parameter telling whether the counter in the
+register counts up or down, and the timer clock rate, and then conjure all
+necessary parameters.
+
+Since a 32-bit counter at say 100 MHz will wrap around to zero after some 43
+seconds, the code handling the clock source will have to compensate for this.
+That is the reason why the clock source struct also contains a 'mask'
+member telling how many bits of the source are valid. This way the timekeeping
+code knows when the counter will wrap around and can insert the necessary
+compensation code on both sides of the wrap point so that the system timeline
+remains monotonic.
+
+
+Clock events
+------------
+
+Clock events are the conceptual reverse of clock sources: they take a
+desired time specification value and calculate the values to poke into
+hardware timer registers.
+
+Clock events are orthogonal to clock sources. The same hardware
+and register range may be used for the clock event, but it is essentially
+a different thing. The hardware driving clock events has to be able to
+fire interrupts, so as to trigger events on the system timeline. On an SMP
+system, it is ideal (and customary) to have one such event driving timer per
+CPU core, so that each core can trigger events independently of any other
+core.
+
+You will notice that the clock event device code is based on the same basic
+idea about translating counters to nanoseconds using mult and shift
+arithmetic, and you find the same family of helper functions again for
+assigning these values. The clock event driver does not need a 'mask'
+attribute however: the system will not try to plan events beyond the time
+horizon of the clock event.
+
+
+sched_clock()
+-------------
+
+In addition to the clock sources and clock events there is a special weak
+function in the kernel called sched_clock(). This function shall return the
+number of nanoseconds since the system was started. An architecture may or
+may not provide an implementation of sched_clock() on its own. If a local
+implementation is not provided, the system jiffy counter will be used as
+sched_clock().
+
+As the name suggests, sched_clock() is used for scheduling the system,
+determining the absolute timeslice for a certain process in the CFS scheduler
+for example. It is also used for printk timestamps when you have selected to
+include time information in printk for things like bootcharts.
+
+Compared to clock sources, sched_clock() has to be very fast: it is called
+much more often, especially by the scheduler. If you have to do trade-offs
+between accuracy compared to the clock source, you may sacrifice accuracy
+for speed in sched_clock(). It however requires some of the same basic
+characteristics as the clock source, i.e. it should be monotonic.
+
+The sched_clock() function may wrap only on unsigned long long boundaries,
+i.e. after 64 bits. Since this is a nanosecond value this will mean it wraps
+after circa 585 years. (For most practical systems this means "never".)
+
+If an architecture does not provide its own implementation of this function,
+it will fall back to using jiffies, making its maximum resolution 1/HZ of the
+jiffy frequency for the architecture. This will affect scheduling accuracy
+and will likely show up in system benchmarks.
+
+The clock driving sched_clock() may stop or reset to zero during system
+suspend/sleep. This does not matter to the function it serves of scheduling
+events on the system. However it may result in interesting timestamps in
+printk().
+
+The sched_clock() function should be callable in any context, IRQ- and
+NMI-safe and return a sane value in any context.
+
+Some architectures may have a limited set of time sources and lack a nice
+counter to derive a 64-bit nanosecond value, so for example on the ARM
+architecture, special helper functions have been created to provide a
+sched_clock() nanosecond base from a 16- or 32-bit counter. Sometimes the
+same counter that is also used as clock source is used for this purpose.
+
+On SMP systems, it is crucial for performance that sched_clock() can be called
+independently on each CPU without any synchronization performance hits.
+Some hardware (such as the x86 TSC) will cause the sched_clock() function to
+drift between the CPUs on the system. The kernel can work around this by
+enabling the CONFIG_HAVE_UNSTABLE_SCHED_CLOCK option. This is another aspect
+that makes sched_clock() different from the ordinary clock source.
+
+
+Delay timers (some architectures only)
+--------------------------------------
+
+On systems with variable CPU frequency, the various kernel delay() functions
+will sometimes behave strangely. Basically these delays usually use a hard
+loop to delay a certain number of jiffy fractions using a "lpj" (loops per
+jiffy) value, calibrated on boot.
+
+Let's hope that your system is running on maximum frequency when this value
+is calibrated: as an effect when the frequency is geared down to half the
+full frequency, any delay() will be twice as long. Usually this does not
+hurt, as you're commonly requesting that amount of delay *or more*. But
+basically the semantics are quite unpredictable on such systems.
+
+Enter timer-based delays. Using these, a timer read may be used instead of
+a hard-coded loop for providing the desired delay.
+
+This is done by declaring a struct delay_timer and assigning the appropriate
+function pointers and rate settings for this delay timer.
+
+This is available on some architectures like OpenRISC or ARM.
diff --git a/Documentation/timers/timekeeping.txt b/Documentation/timers/timekeeping.txt
deleted file mode 100644
index 2d1732b0a868..000000000000
--- a/Documentation/timers/timekeeping.txt
+++ /dev/null
@@ -1,179 +0,0 @@
-Clock sources, Clock events, sched_clock() and delay timers
------------------------------------------------------------
-
-This document tries to briefly explain some basic kernel timekeeping
-abstractions. It partly pertains to the drivers usually found in
-drivers/clocksource in the kernel tree, but the code may be spread out
-across the kernel.
-
-If you grep through the kernel source you will find a number of architecture-
-specific implementations of clock sources, clockevents and several likewise
-architecture-specific overrides of the sched_clock() function and some
-delay timers.
-
-To provide timekeeping for your platform, the clock source provides
-the basic timeline, whereas clock events shoot interrupts on certain points
-on this timeline, providing facilities such as high-resolution timers.
-sched_clock() is used for scheduling and timestamping, and delay timers
-provide an accurate delay source using hardware counters.
-
-
-Clock sources
--------------
-
-The purpose of the clock source is to provide a timeline for the system that
-tells you where you are in time. For example issuing the command 'date' on
-a Linux system will eventually read the clock source to determine exactly
-what time it is.
-
-Typically the clock source is a monotonic, atomic counter which will provide
-n bits which count from 0 to (2^n)-1 and then wraps around to 0 and start over.
-It will ideally NEVER stop ticking as long as the system is running. It
-may stop during system suspend.
-
-The clock source shall have as high resolution as possible, and the frequency
-shall be as stable and correct as possible as compared to a real-world wall
-clock. It should not move unpredictably back and forth in time or miss a few
-cycles here and there.
-
-It must be immune to the kind of effects that occur in hardware where e.g.
-the counter register is read in two phases on the bus lowest 16 bits first
-and the higher 16 bits in a second bus cycle with the counter bits
-potentially being updated in between leading to the risk of very strange
-values from the counter.
-
-When the wall-clock accuracy of the clock source isn't satisfactory, there
-are various quirks and layers in the timekeeping code for e.g. synchronizing
-the user-visible time to RTC clocks in the system or against networked time
-servers using NTP, but all they do basically is update an offset against
-the clock source, which provides the fundamental timeline for the system.
-These measures does not affect the clock source per se, they only adapt the
-system to the shortcomings of it.
-
-The clock source struct shall provide means to translate the provided counter
-into a nanosecond value as an unsigned long long (unsigned 64 bit) number.
-Since this operation may be invoked very often, doing this in a strict
-mathematical sense is not desirable: instead the number is taken as close as
-possible to a nanosecond value using only the arithmetic operations
-multiply and shift, so in clocksource_cyc2ns() you find:
-
-  ns ~= (clocksource * mult) >> shift
-
-You will find a number of helper functions in the clock source code intended
-to aid in providing these mult and shift values, such as
-clocksource_khz2mult(), clocksource_hz2mult() that help determine the
-mult factor from a fixed shift, and clocksource_register_hz() and
-clocksource_register_khz() which will help out assigning both shift and mult
-factors using the frequency of the clock source as the only input.
-
-For real simple clock sources accessed from a single I/O memory location
-there is nowadays even clocksource_mmio_init() which will take a memory
-location, bit width, a parameter telling whether the counter in the
-register counts up or down, and the timer clock rate, and then conjure all
-necessary parameters.
-
-Since a 32-bit counter at say 100 MHz will wrap around to zero after some 43
-seconds, the code handling the clock source will have to compensate for this.
-That is the reason why the clock source struct also contains a 'mask'
-member telling how many bits of the source are valid. This way the timekeeping
-code knows when the counter will wrap around and can insert the necessary
-compensation code on both sides of the wrap point so that the system timeline
-remains monotonic.
-
-
-Clock events
-------------
-
-Clock events are the conceptual reverse of clock sources: they take a
-desired time specification value and calculate the values to poke into
-hardware timer registers.
-
-Clock events are orthogonal to clock sources. The same hardware
-and register range may be used for the clock event, but it is essentially
-a different thing. The hardware driving clock events has to be able to
-fire interrupts, so as to trigger events on the system timeline. On an SMP
-system, it is ideal (and customary) to have one such event driving timer per
-CPU core, so that each core can trigger events independently of any other
-core.
-
-You will notice that the clock event device code is based on the same basic
-idea about translating counters to nanoseconds using mult and shift
-arithmetic, and you find the same family of helper functions again for
-assigning these values. The clock event driver does not need a 'mask'
-attribute however: the system will not try to plan events beyond the time
-horizon of the clock event.
-
-
-sched_clock()
--------------
-
-In addition to the clock sources and clock events there is a special weak
-function in the kernel called sched_clock(). This function shall return the
-number of nanoseconds since the system was started. An architecture may or
-may not provide an implementation of sched_clock() on its own. If a local
-implementation is not provided, the system jiffy counter will be used as
-sched_clock().
-
-As the name suggests, sched_clock() is used for scheduling the system,
-determining the absolute timeslice for a certain process in the CFS scheduler
-for example. It is also used for printk timestamps when you have selected to
-include time information in printk for things like bootcharts.
-
-Compared to clock sources, sched_clock() has to be very fast: it is called
-much more often, especially by the scheduler. If you have to do trade-offs
-between accuracy compared to the clock source, you may sacrifice accuracy
-for speed in sched_clock(). It however requires some of the same basic
-characteristics as the clock source, i.e. it should be monotonic.
-
-The sched_clock() function may wrap only on unsigned long long boundaries,
-i.e. after 64 bits. Since this is a nanosecond value this will mean it wraps
-after circa 585 years. (For most practical systems this means "never".)
-
-If an architecture does not provide its own implementation of this function,
-it will fall back to using jiffies, making its maximum resolution 1/HZ of the
-jiffy frequency for the architecture. This will affect scheduling accuracy
-and will likely show up in system benchmarks.
-
-The clock driving sched_clock() may stop or reset to zero during system
-suspend/sleep. This does not matter to the function it serves of scheduling
-events on the system. However it may result in interesting timestamps in
-printk().
-
-The sched_clock() function should be callable in any context, IRQ- and
-NMI-safe and return a sane value in any context.
-
-Some architectures may have a limited set of time sources and lack a nice
-counter to derive a 64-bit nanosecond value, so for example on the ARM
-architecture, special helper functions have been created to provide a
-sched_clock() nanosecond base from a 16- or 32-bit counter. Sometimes the
-same counter that is also used as clock source is used for this purpose.
-
-On SMP systems, it is crucial for performance that sched_clock() can be called
-independently on each CPU without any synchronization performance hits.
-Some hardware (such as the x86 TSC) will cause the sched_clock() function to
-drift between the CPUs on the system. The kernel can work around this by
-enabling the CONFIG_HAVE_UNSTABLE_SCHED_CLOCK option. This is another aspect
-that makes sched_clock() different from the ordinary clock source.
-
-
-Delay timers (some architectures only)
---------------------------------------
-
-On systems with variable CPU frequency, the various kernel delay() functions
-will sometimes behave strangely. Basically these delays usually use a hard
-loop to delay a certain number of jiffy fractions using a "lpj" (loops per
-jiffy) value, calibrated on boot.
-
-Let's hope that your system is running on maximum frequency when this value
-is calibrated: as an effect when the frequency is geared down to half the
-full frequency, any delay() will be twice as long. Usually this does not
-hurt, as you're commonly requesting that amount of delay *or more*. But
-basically the semantics are quite unpredictable on such systems.
-
-Enter timer-based delays. Using these, a timer read may be used instead of
-a hard-coded loop for providing the desired delay.
-
-This is done by declaring a struct delay_timer and assigning the appropriate
-function pointers and rate settings for this delay timer.
-
-This is available on some architectures like OpenRISC or ARM.
diff --git a/Documentation/timers/timers-howto.rst b/Documentation/timers/timers-howto.rst
new file mode 100644
index 000000000000..7e3167bec2b1
--- /dev/null
+++ b/Documentation/timers/timers-howto.rst
@@ -0,0 +1,112 @@
+===================================================================
+delays - Information on the various kernel delay / sleep mechanisms
+===================================================================
+
+This document seeks to answer the common question: "What is the
+RightWay (TM) to insert a delay?"
+
+This question is most often faced by driver writers who have to
+deal with hardware delays and who may not be the most intimately
+familiar with the inner workings of the Linux Kernel.
+
+
+Inserting Delays
+----------------
+
+The first, and most important, question you need to ask is "Is my
+code in an atomic context?"  This should be followed closely by "Does
+it really need to delay in atomic context?" If so...
+
+ATOMIC CONTEXT:
+	You must use the `*delay` family of functions. These
+	functions use the jiffie estimation of clock speed
+	and will busy wait for enough loop cycles to achieve
+	the desired delay:
+
+	ndelay(unsigned long nsecs)
+	udelay(unsigned long usecs)
+	mdelay(unsigned long msecs)
+
+	udelay is the generally preferred API; ndelay-level
+	precision may not actually exist on many non-PC devices.
+
+	mdelay is macro wrapper around udelay, to account for
+	possible overflow when passing large arguments to udelay.
+	In general, use of mdelay is discouraged and code should
+	be refactored to allow for the use of msleep.
+
+NON-ATOMIC CONTEXT:
+	You should use the `*sleep[_range]` family of functions.
+	There are a few more options here, while any of them may
+	work correctly, using the "right" sleep function will
+	help the scheduler, power management, and just make your
+	driver better :)
+
+	-- Backed by busy-wait loop:
+
+		udelay(unsigned long usecs)
+
+	-- Backed by hrtimers:
+
+		usleep_range(unsigned long min, unsigned long max)
+
+	-- Backed by jiffies / legacy_timers
+
+		msleep(unsigned long msecs)
+		msleep_interruptible(unsigned long msecs)
+
+	Unlike the `*delay` family, the underlying mechanism
+	driving each of these calls varies, thus there are
+	quirks you should be aware of.
+
+
+	SLEEPING FOR "A FEW" USECS ( < ~10us? ):
+		* Use udelay
+
+		- Why not usleep?
+			On slower systems, (embedded, OR perhaps a speed-
+			stepped PC!) the overhead of setting up the hrtimers
+			for usleep *may* not be worth it. Such an evaluation
+			will obviously depend on your specific situation, but
+			it is something to be aware of.
+
+	SLEEPING FOR ~USECS OR SMALL MSECS ( 10us - 20ms):
+		* Use usleep_range
+
+		- Why not msleep for (1ms - 20ms)?
+			Explained originally here:
+				http://lkml.org/lkml/2007/8/3/250
+
+			msleep(1~20) may not do what the caller intends, and
+			will often sleep longer (~20 ms actual sleep for any
+			value given in the 1~20ms range). In many cases this
+			is not the desired behavior.
+
+		- Why is there no "usleep" / What is a good range?
+			Since usleep_range is built on top of hrtimers, the
+			wakeup will be very precise (ish), thus a simple
+			usleep function would likely introduce a large number
+			of undesired interrupts.
+
+			With the introduction of a range, the scheduler is
+			free to coalesce your wakeup with any other wakeup
+			that may have happened for other reasons, or at the
+			worst case, fire an interrupt for your upper bound.
+
+			The larger a range you supply, the greater a chance
+			that you will not trigger an interrupt; this should
+			be balanced with what is an acceptable upper bound on
+			delay / performance for your specific code path. Exact
+			tolerances here are very situation specific, thus it
+			is left to the caller to determine a reasonable range.
+
+	SLEEPING FOR LARGER MSECS ( 10ms+ )
+		* Use msleep or possibly msleep_interruptible
+
+		- What's the difference?
+			msleep sets the current task to TASK_UNINTERRUPTIBLE
+			whereas msleep_interruptible sets the current task to
+			TASK_INTERRUPTIBLE before scheduling the sleep. In
+			short, the difference is whether the sleep can be ended
+			early by a signal. In general, just use msleep unless
+			you know you have a need for the interruptible variant.
diff --git a/Documentation/timers/timers-howto.txt b/Documentation/timers/timers-howto.txt
deleted file mode 100644
index 038f8c77a076..000000000000
--- a/Documentation/timers/timers-howto.txt
+++ /dev/null
@@ -1,105 +0,0 @@
-delays - Information on the various kernel delay / sleep mechanisms
--------------------------------------------------------------------
-
-This document seeks to answer the common question: "What is the
-RightWay (TM) to insert a delay?"
-
-This question is most often faced by driver writers who have to
-deal with hardware delays and who may not be the most intimately
-familiar with the inner workings of the Linux Kernel.
-
-
-Inserting Delays
-----------------
-
-The first, and most important, question you need to ask is "Is my
-code in an atomic context?"  This should be followed closely by "Does
-it really need to delay in atomic context?" If so...
-
-ATOMIC CONTEXT:
-	You must use the *delay family of functions. These
-	functions use the jiffie estimation of clock speed
-	and will busy wait for enough loop cycles to achieve
-	the desired delay:
-
-	ndelay(unsigned long nsecs)
-	udelay(unsigned long usecs)
-	mdelay(unsigned long msecs)
-
-	udelay is the generally preferred API; ndelay-level
-	precision may not actually exist on many non-PC devices.
-
-	mdelay is macro wrapper around udelay, to account for
-	possible overflow when passing large arguments to udelay.
-	In general, use of mdelay is discouraged and code should
-	be refactored to allow for the use of msleep.
-
-NON-ATOMIC CONTEXT:
-	You should use the *sleep[_range] family of functions.
-	There are a few more options here, while any of them may
-	work correctly, using the "right" sleep function will
-	help the scheduler, power management, and just make your
-	driver better :)
-
-	-- Backed by busy-wait loop:
-		udelay(unsigned long usecs)
-	-- Backed by hrtimers:
-		usleep_range(unsigned long min, unsigned long max)
-	-- Backed by jiffies / legacy_timers
-		msleep(unsigned long msecs)
-		msleep_interruptible(unsigned long msecs)
-
-	Unlike the *delay family, the underlying mechanism
-	driving each of these calls varies, thus there are
-	quirks you should be aware of.
-
-
-	SLEEPING FOR "A FEW" USECS ( < ~10us? ):
-		* Use udelay
-
-		- Why not usleep?
-			On slower systems, (embedded, OR perhaps a speed-
-			stepped PC!) the overhead of setting up the hrtimers
-			for usleep *may* not be worth it. Such an evaluation
-			will obviously depend on your specific situation, but
-			it is something to be aware of.
-
-	SLEEPING FOR ~USECS OR SMALL MSECS ( 10us - 20ms):
-		* Use usleep_range
-
-		- Why not msleep for (1ms - 20ms)?
-			Explained originally here:
-				http://lkml.org/lkml/2007/8/3/250
-			msleep(1~20) may not do what the caller intends, and
-			will often sleep longer (~20 ms actual sleep for any
-			value given in the 1~20ms range). In many cases this
-			is not the desired behavior.
-
-		- Why is there no "usleep" / What is a good range?
-			Since usleep_range is built on top of hrtimers, the
-			wakeup will be very precise (ish), thus a simple
-			usleep function would likely introduce a large number
-			of undesired interrupts.
-
-			With the introduction of a range, the scheduler is
-			free to coalesce your wakeup with any other wakeup
-			that may have happened for other reasons, or at the
-			worst case, fire an interrupt for your upper bound.
-
-			The larger a range you supply, the greater a chance
-			that you will not trigger an interrupt; this should
-			be balanced with what is an acceptable upper bound on
-			delay / performance for your specific code path. Exact
-			tolerances here are very situation specific, thus it
-			is left to the caller to determine a reasonable range.
-
-	SLEEPING FOR LARGER MSECS ( 10ms+ )
-		* Use msleep or possibly msleep_interruptible
-
-		- What's the difference?
-			msleep sets the current task to TASK_UNINTERRUPTIBLE
-			whereas msleep_interruptible sets the current task to
-			TASK_INTERRUPTIBLE before scheduling the sleep. In
-			short, the difference is whether the sleep can be ended
-			early by a signal. In general, just use msleep unless
-			you know you have a need for the interruptible variant.
diff --git a/MAINTAINERS b/MAINTAINERS
index 5fe44d5d82b4..0db7f12439f7 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -7192,7 +7192,7 @@ F:	drivers/net/ethernet/hp/hp100.*
 HPET:	High Precision Event Timers driver
 M:	Clemens Ladisch <clemens@ladisch.de>
 S:	Maintained
-F:	Documentation/timers/hpet.txt
+F:	Documentation/timers/hpet.rst
 F:	drivers/char/hpet.c
 F:	include/linux/hpet.h
 F:	include/uapi/linux/hpet.h
diff --git a/drivers/media/usb/dvb-usb-v2/anysee.c b/drivers/media/usb/dvb-usb-v2/anysee.c
index 48fb0d41e03b..fb6d99dea31a 100644
--- a/drivers/media/usb/dvb-usb-v2/anysee.c
+++ b/drivers/media/usb/dvb-usb-v2/anysee.c
@@ -56,7 +56,7 @@ static int anysee_ctrl_msg(struct dvb_usb_device *d,
 	/* TODO FIXME: dvb_usb_generic_rw() fails rarely with error code -32
 	 * (EPIPE, Broken pipe). Function supports currently msleep() as a
 	 * parameter but I would not like to use it, since according to
-	 * Documentation/timers/timers-howto.txt it should not be used such
+	 * Documentation/timers/timers-howto.rst it should not be used such
 	 * short, under < 20ms, sleeps. Repeating failed message would be
 	 * better choice as not to add unwanted delays...
 	 * Fixing that correctly is one of those or both;
diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index c894cf0d8a28..c5d8996d5165 100644
--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -2304,7 +2304,7 @@ static int regulator_ena_gpio_ctrl(struct regulator_dev *rdev, bool enable)
  *
  * Delay for the requested amount of time as per the guidelines in:
  *
- *     Documentation/timers/timers-howto.txt
+ *     Documentation/timers/timers-howto.rst
  *
  * The assumption here is that regulators will never be enabled in
  * atomic context and therefore sleeping functions can be used.
diff --git a/include/linux/iopoll.h b/include/linux/iopoll.h
index 3908353deec6..35e15dfd4155 100644
--- a/include/linux/iopoll.h
+++ b/include/linux/iopoll.h
@@ -21,7 +21,7 @@
  * @cond: Break condition (usually involving @val)
  * @sleep_us: Maximum time to sleep between reads in us (0
  *            tight-loops).  Should be less than ~20ms since usleep_range
- *            is used (see Documentation/timers/timers-howto.txt).
+ *            is used (see Documentation/timers/timers-howto.rst).
  * @timeout_us: Timeout in us, 0 means never timeout
  *
  * Returns 0 on success and -ETIMEDOUT upon a timeout. In either
@@ -60,7 +60,7 @@
  * @cond: Break condition (usually involving @val)
  * @delay_us: Time to udelay between reads in us (0 tight-loops).  Should
  *            be less than ~10us since udelay is used (see
- *            Documentation/timers/timers-howto.txt).
+ *            Documentation/timers/timers-howto.rst).
  * @timeout_us: Timeout in us, 0 means never timeout
  *
  * Returns 0 on success and -ETIMEDOUT upon a timeout. In either
diff --git a/include/linux/regmap.h b/include/linux/regmap.h
index daeec7dbd65c..ed5e9d0a1285 100644
--- a/include/linux/regmap.h
+++ b/include/linux/regmap.h
@@ -112,7 +112,7 @@ struct reg_sequence {
  * @cond: Break condition (usually involving @val)
  * @sleep_us: Maximum time to sleep between reads in us (0
  *            tight-loops).  Should be less than ~20ms since usleep_range
- *            is used (see Documentation/timers/timers-howto.txt).
+ *            is used (see Documentation/timers/timers-howto.rst).
  * @timeout_us: Timeout in us, 0 means never timeout
  *
  * Returns 0 on success and -ETIMEDOUT upon a timeout or the regmap_read
@@ -154,7 +154,7 @@ struct reg_sequence {
  * @cond: Break condition (usually involving @val)
  * @sleep_us: Maximum time to sleep between reads in us (0
  *            tight-loops).  Should be less than ~20ms since usleep_range
- *            is used (see Documentation/timers/timers-howto.txt).
+ *            is used (see Documentation/timers/timers-howto.rst).
  * @timeout_us: Timeout in us, 0 means never timeout
  *
  * Returns 0 on success and -ETIMEDOUT upon a timeout or the regmap_field_read
diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 342c7c781ba5..a6d436809bf5 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -5712,7 +5712,7 @@ sub process {
 			# ignore udelay's < 10, however
 			if (! ($delay < 10) ) {
 				CHK("USLEEP_RANGE",
-				    "usleep_range is preferred over udelay; see Documentation/timers/timers-howto.txt\n" . $herecurr);
+				    "usleep_range is preferred over udelay; see Documentation/timers/timers-howto.rst\n" . $herecurr);
 			}
 			if ($delay > 2000) {
 				WARN("LONG_UDELAY",
@@ -5724,7 +5724,7 @@ sub process {
 		if ($line =~ /\bmsleep\s*\((\d+)\);/) {
 			if ($1 < 20) {
 				WARN("MSLEEP",
-				     "msleep < 20ms can sleep for up to 20ms; see Documentation/timers/timers-howto.txt\n" . $herecurr);
+				     "msleep < 20ms can sleep for up to 20ms; see Documentation/timers/timers-howto.rst\n" . $herecurr);
 			}
 		}
 
@@ -6115,11 +6115,11 @@ sub process {
 			my $max = $7;
 			if ($min eq $max) {
 				WARN("USLEEP_RANGE",
-				     "usleep_range should not use min == max args; see Documentation/timers/timers-howto.txt\n" . "$here\n$stat\n");
+				     "usleep_range should not use min == max args; see Documentation/timers/timers-howto.rst\n" . "$here\n$stat\n");
 			} elsif ($min =~ /^\d+$/ && $max =~ /^\d+$/ &&
 				 $min > $max) {
 				WARN("USLEEP_RANGE",
-				     "usleep_range args reversed, use min then max; see Documentation/timers/timers-howto.txt\n" . "$here\n$stat\n");
+				     "usleep_range args reversed, use min then max; see Documentation/timers/timers-howto.rst\n" . "$here\n$stat\n");
 			}
 		}
 
diff --git a/sound/soc/sof/ops.h b/sound/soc/sof/ops.h
index 80fc3b374c2b..8058a6c73082 100644
--- a/sound/soc/sof/ops.h
+++ b/sound/soc/sof/ops.h
@@ -349,7 +349,7 @@ static inline const struct snd_sof_dsp_ops
  * @cond: Break condition (usually involving @val)
  * @sleep_us: Maximum time to sleep between reads in us (0
  *            tight-loops).  Should be less than ~20ms since usleep_range
- *            is used (see Documentation/timers/timers-howto.txt).
+ *            is used (see Documentation/timers/timers-howto.rst).
  * @timeout_us: Timeout in us, 0 means never timeout
  *
  * Returns 0 on success and -ETIMEDOUT upon a timeout. In either
-- 
cgit v1.2.3


From 407b584d155be67a9311a62da8d7874f62b987ac Mon Sep 17 00:00:00 2001
From: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Date: Thu, 13 Jun 2019 07:29:17 -0300
Subject: scripts/documentation-file-ref-check: ignore output dir

When there's no Documentation/output directory, the script will
complain about those missing references:

	Documentation/doc-guide/sphinx.rst: Documentation/output
	Documentation/doc-guide/sphinx.rst: Documentation/output
	Documentation/process/howto.rst: Documentation/output
	Documentation/translations/it_IT/doc-guide/sphinx.rst: Documentation/output
	Documentation/translations/it_IT/doc-guide/sphinx.rst: Documentation/output
	Documentation/translations/it_IT/process/howto.rst: Documentation/output
	Documentation/translations/ja_JP/howto.rst: Documentation/output
	Documentation/translations/ko_KR/howto.rst: Documentation/output

Those are false positives, so add an ignore rule for them.

Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
---
 scripts/documentation-file-ref-check | 3 +++
 1 file changed, 3 insertions(+)

(limited to 'scripts')

diff --git a/scripts/documentation-file-ref-check b/scripts/documentation-file-ref-check
index a4139a576726..7784c54aa38b 100755
--- a/scripts/documentation-file-ref-check
+++ b/scripts/documentation-file-ref-check
@@ -90,6 +90,9 @@ while (<IN>) {
 	# Skip this script
 	next if ($f eq $scriptname);
 
+	# Ignore the dir where documentation will be built
+	next if ($ln =~ m,\b(\S*)Documentation/output,);
+
 	if ($ln =~ m,\b(\S*)(Documentation/[A-Za-z0-9\_\.\,\~/\*\[\]\?+-]*)(.*),) {
 		my $prefix = $1;
 		my $ref = $2;
-- 
cgit v1.2.3


From 344fdb28a0dfac2e42925f149029748b34d2effa Mon Sep 17 00:00:00 2001
From: Jonathan Corbet <corbet@lwn.net>
Date: Fri, 21 Jun 2019 17:34:30 -0600
Subject: kernel-doc: Don't try to mark up function names

We now have better automarkup in sphinx itself and, besides, this markup
was incorrect and left :c:func: gunk in the processed docs.  Sort of
discouraging that nobody ever noticed...:)

As a first step toward the removal of impenetrable regex magic from
kernel-doc it's a tiny one, but you have to start somewhere.

Signed-off-by: Jonathan Corbet <corbet@lwn.net>
---
 scripts/kernel-doc | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

(limited to 'scripts')

diff --git a/scripts/kernel-doc b/scripts/kernel-doc
index c0cb41e65b9b..6b03012750da 100755
--- a/scripts/kernel-doc
+++ b/scripts/kernel-doc
@@ -249,7 +249,7 @@ my @highlights_rst = (
                        [$type_member_func, "\\:c\\:type\\:`\$1\$2\$3\\\\(\\\\) <\$1>`"],
                        [$type_member, "\\:c\\:type\\:`\$1\$2\$3 <\$1>`"],
 		       [$type_fp_param, "**\$1\\\\(\\\\)**"],
-                       [$type_func, "\\:c\\:func\\:`\$1()`"],
+                       [$type_func, "\$1()"],
                        [$type_enum, "\\:c\\:type\\:`\$1 <\$2>`"],
                        [$type_struct, "\\:c\\:type\\:`\$1 <\$2>`"],
                        [$type_typedef, "\\:c\\:type\\:`\$1 <\$2>`"],
-- 
cgit v1.2.3


From 8c69b77a0175d6e14df9cdf386a8b69f6cfa2c6a Mon Sep 17 00:00:00 2001
From: Mike Rapoport <rppt@linux.ibm.com>
Date: Mon, 24 Jun 2019 08:25:07 +0300
Subject: scripts/sphinx-pre-install: fix out-of-tree build

Build of htmldocs fails for out-of-tree builds:

$ make V=1 O=~/build/kernel/ htmldocs
make -C /home/rppt/build/kernel -f /home/rppt/git/linux-docs/Makefile htmldocs
make[1]: Entering directory '/home/rppt/build/kernel'
make -f /home/rppt/git/linux-docs/scripts/Makefile.build obj=scripts/basic
rm -f .tmp_quiet_recordmcount
make -f /home/rppt/git/linux-docs/scripts/Makefile.build obj=Documentation htmldocs
Can't open Documentation/conf.py at /home/rppt/git/linux-docs/scripts/sphinx-pre-install line 230.
/home/rppt/git/linux-docs/Documentation/Makefile:80: recipe for target 'htmldocs' failed
make[2]: *** [htmldocs] Error 2

The scripts/sphinx-pre-install is trying to open files in the current
directory which is $KBUILD_OUTPUT rather than in $srctree.

Fix it.

Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
Reviewed-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
---
 scripts/sphinx-pre-install | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

(limited to 'scripts')

diff --git a/scripts/sphinx-pre-install b/scripts/sphinx-pre-install
index 0b44d51c4991..f230e65329a2 100755
--- a/scripts/sphinx-pre-install
+++ b/scripts/sphinx-pre-install
@@ -5,8 +5,11 @@ use strict;
 # Copyright (c) 2017-2019 Mauro Carvalho Chehab <mchehab@kernel.org>
 #
 
-my $conf = "Documentation/conf.py";
-my $requirement_file = "Documentation/sphinx/requirements.txt";
+my $prefix = "./";
+$prefix = "$ENV{'srctree'}/" if ($ENV{'srctree'});
+
+my $conf = $prefix . "Documentation/conf.py";
+my $requirement_file = $prefix . "Documentation/sphinx/requirements.txt";
 my $virtenv_prefix = "sphinx_";
 
 #
-- 
cgit v1.2.3