kbuild: Add support for DT binding schema checks

This adds the build infrastructure for checking DT binding schema
documents and validating dts files using the binding schema.

Check DT binding schema documents:
make dt_binding_check

Build dts files and check using DT binding schema:
make dtbs_check

Optionally, DT_SCHEMA_FILES can be passed in with a schema file(s) to
use for validation. This makes it easier to find and fix errors
generated by a specific schema.

Currently, the validation targets are separate from a normal build to
avoid a hard dependency on the external DT schema project and because
there are lots of warnings generated.

Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Mark Rutland <mark.rutland@arm.com>
Acked-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Michal Marek <michal.lkml@markovi.net>
Cc: linux-doc@vger.kernel.org
Cc: devicetree@vger.kernel.org
Cc: linux-kbuild@vger.kernel.org
Signed-off-by: Rob Herring <robh@kernel.org>

7 files changed, 67 insertions, 6 deletions

diff --git a/.gitignore b/.gitignore
index 97ba6b79834c..a20ac26aa2f5 100644
--- a/.gitignore
+++ b/.gitignore
@@ -15,6 +15,7 @@
 *.bin
 *.bz2
 *.c.[012]*.*
+*.dt.yaml
 *.dtb
 *.dtb.S
 *.dwo
diff --git a/Documentation/Makefile b/Documentation/Makefile
index 2ca77ad0f238..9786957c6a35 100644
--- a/Documentation/Makefile
+++ b/Documentation/Makefile
@@ -2,7 +2,7 @@
 # Makefile for Sphinx documentation
 #
 
-subdir-y :=
+subdir-y := devicetree/bindings/
 
 # You can set these variables from the command line.
 SPHINXBUILD   = sphinx-build
diff --git a/Documentation/devicetree/bindings/.gitignore b/Documentation/devicetree/bindings/.gitignore
new file mode 100644
index 000000000000..ef82fcfcccab
--- /dev/null
+++ b/Documentation/devicetree/bindings/.gitignore
@@ -0,0 +1,2 @@
+*.example.dts
+processed-schema.yaml
diff --git a/Documentation/devicetree/bindings/Makefile b/Documentation/devicetree/bindings/Makefile
new file mode 100644
index 000000000000..6e5cef0ed6fb
--- /dev/null
+++ b/Documentation/devicetree/bindings/Makefile
@@ -0,0 +1,27 @@
+# SPDX-License-Identifier: GPL-2.0
+DT_DOC_CHECKER ?= dt-doc-validate
+DT_EXTRACT_EX ?= dt-extract-example
+DT_MK_SCHEMA ?= dt-mk-schema
+DT_MK_SCHEMA_FLAGS := $(if $(DT_SCHEMA_FILES), -u)
+
+quiet_cmd_chk_binding = CHKDT   $(patsubst $(srctree)/%,%,$<)
+      cmd_chk_binding = $(DT_DOC_CHECKER) $< ; \
+                        $(DT_EXTRACT_EX) $< > $@
+
+$(obj)/%.example.dts: $(src)/%.yaml FORCE
+	$(call if_changed,chk_binding)
+
+DT_TMP_SCHEMA := processed-schema.yaml
+extra-y += $(DT_TMP_SCHEMA)
+
+quiet_cmd_mk_schema = SCHEMA  $@
+      cmd_mk_schema = $(DT_MK_SCHEMA) $(DT_MK_SCHEMA_FLAGS) -o $@ $(filter-out FORCE, $^)
+
+DT_DOCS = $(shell cd $(srctree)/$(src) && find * -name '*.yaml')
+DT_SCHEMA_FILES ?= $(addprefix $(src)/,$(DT_DOCS))
+
+extra-y += $(patsubst $(src)/%.yaml,%.example.dts, $(DT_SCHEMA_FILES))
+extra-y += $(patsubst $(src)/%.yaml,%.example.dtb, $(DT_SCHEMA_FILES))
+
+$(obj)/$(DT_TMP_SCHEMA): $(DT_SCHEMA_FILES) FORCE
+	$(call if_changed,mk_schema)
diff --git a/Makefile b/Makefile
index 2f36db897895..a3e2db2a3119 100644
--- a/Makefile
+++ b/Makefile
@@ -1232,10 +1232,13 @@ ifneq ($(dtstree),)
 %.dtb: prepare3 scripts_dtc
 	$(Q)$(MAKE) $(build)=$(dtstree) $(dtstree)/$@
 
-PHONY += dtbs dtbs_install
-dtbs: prepare3 scripts_dtc
+PHONY += dtbs dtbs_install dt_binding_check
+dtbs dtbs_check: prepare3 scripts_dtc
 	$(Q)$(MAKE) $(build)=$(dtstree)
 
+dtbs_check: export CHECK_DTBS=1
+dtbs_check: dt_binding_check
+
 dtbs_install:
 	$(Q)$(MAKE) $(dtbinst)=$(dtstree)
 
@@ -1249,6 +1252,9 @@ PHONY += scripts_dtc
 scripts_dtc: scripts_basic
 	$(Q)$(MAKE) $(build)=scripts/dtc
 
+dt_binding_check: scripts_dtc
+	$(Q)$(MAKE) $(build)=Documentation/devicetree/bindings
+
 # ---------------------------------------------------------------------------
 # Modules
 
@@ -1611,7 +1617,8 @@ clean: $(clean-dirs)
 	$(call cmd,rmfiles)
 	@find $(if $(KBUILD_EXTMOD), $(KBUILD_EXTMOD), .) $(RCS_FIND_IGNORE) \
 		\( -name '*.[aios]' -o -name '*.ko' -o -name '.*.cmd' \
-		-o -name '*.ko.*' -o -name '*.dtb' -o -name '*.dtb.S' \
+		-o -name '*.ko.*' \
+		-o -name '*.dtb' -o -name '*.dtb.S' -o -name '*.dt.yaml' \
 		-o -name '*.dwo' -o -name '*.lst' \
 		-o -name '*.su'  \
 		-o -name '.*.d' -o -name '.*.tmp' -o -name '*.mod.c' \
diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index 8fe4468f9bda..723b33c942df 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -61,6 +61,11 @@ real-obj-m := $(foreach m, $(obj-m), $(if $(strip $($(m:.o=-objs)) $($(m:.o=-y))
 extra-y				+= $(dtb-y)
 extra-$(CONFIG_OF_ALL_DTBS)	+= $(dtb-)
 
+ifneq ($(CHECK_DTBS),)
+extra-y += $(patsubst %.dtb,%.dt.yaml, $(dtb-y))
+extra-$(CONFIG_OF_ALL_DTBS) += $(patsubst %.dtb,%.dt.yaml, $(dtb-))
+endif
+
 # Add subdir path
 
 extra-y		:= $(addprefix $(obj)/,$(extra-y))
@@ -284,13 +289,28 @@ $(obj)/%.dtb.S: $(obj)/%.dtb FORCE
 quiet_cmd_dtc = DTC     $@
 cmd_dtc = mkdir -p $(dir ${dtc-tmp}) ; \
 	$(HOSTCC) -E $(dtc_cpp_flags) -x assembler-with-cpp -o $(dtc-tmp) $< ; \
-	$(DTC) -O dtb -o $@ -b 0 \
+	$(DTC) -O $(2) -o $@ -b 0 \
 		$(addprefix -i,$(dir $<) $(DTC_INCLUDE)) $(DTC_FLAGS) \
 		-d $(depfile).dtc.tmp $(dtc-tmp) ; \
 	cat $(depfile).pre.tmp $(depfile).dtc.tmp > $(depfile)
 
 $(obj)/%.dtb: $(src)/%.dts $(DTC) FORCE
-	$(call if_changed_dep,dtc)
+	$(call if_changed_dep,dtc,dtb)
+
+DT_CHECKER ?= dt-validate
+DT_BINDING_DIR := Documentation/devicetree/bindings
+DT_TMP_SCHEMA := $(objtree)/$(DT_BINDING_DIR)/processed-schema.yaml
+
+quiet_cmd_dtb_check =	CHECK   $@
+      cmd_dtb_check =	$(DT_CHECKER) -p $(DT_TMP_SCHEMA) $@ ;
+
+define rule_dtc_dt_yaml
+	$(call cmd_and_fixdep,dtc,yaml)		\
+	$(call echo-cmd,dtb_check) $(cmd_dtb_check)
+endef
+
+$(obj)/%.dt.yaml: $(src)/%.dts $(DTC) $(DT_TMP_SCHEMA) FORCE
+	$(call if_changed_rule,dtc_dt_yaml)
 
 dtc-tmp = $(subst $(comma),_,$(dot-target).dts.tmp)
 
diff --git a/scripts/dtc/Makefile b/scripts/dtc/Makefile
index 056d5da6c477..5f227d8d39d8 100644
--- a/scripts/dtc/Makefile
+++ b/scripts/dtc/Makefile
@@ -12,6 +12,10 @@ dtc-objs	+= dtc-lexer.lex.o dtc-parser.tab.o
 HOST_EXTRACFLAGS := -I$(src)/libfdt
 
 ifeq ($(wildcard /usr/include/yaml.h),)
+ifneq ($(CHECK_DTBS),)
+$(error dtc needs libyaml for DT schema validation support. \
+	Install the necessary libyaml development package.)
+endif
 HOST_EXTRACFLAGS += -DNO_YAML
 else
 dtc-objs	+= yamltree.o