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authorFabio M. Di Nitto <fdinitto@redhat.com>2011-03-22 16:34:20 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2011-03-22 17:44:12 -0700
commit7bf693951a8e5f7e600a45b74d91d962a453146e (patch)
treed322e17d0d6b445d8332e210e01d3cce7ddfe5ca /Documentation
parent26297607e09ca6c7e6f2a6b86a8bee2f23503bb8 (diff)
downloadlinux-7bf693951a8e5f7e600a45b74d91d962a453146e.tar.bz2
console: allow to retain boot console via boot option keep_bootcon
On some architectures, the boot process involves de-registering the boot console (early boot), initialize drivers and then re-register the console. This mechanism introduces a window in which no printk can happen on the console and messages are buffered and then printed once the new console is available. If a kernel crashes during this window, all it's left on the boot console is "console [foo] enabled, bootconsole disabled" making debug of the crash rather 'interesting'. By adding "keep_bootcon" option, do not unregister the boot console, that will allow to printk everything that is happening up to the crash. The option is clearly meant only for debugging purposes as it introduces lots of duplicated info printed on console, but will make bug report from users easier as it doesn't require a kernel build just to figure out where we crash. Signed-off-by: Fabio M. Di Nitto <fabbione@fabbione.net> Acked-by: David S. Miller <davem@davemloft.net> Cc: Alan Cox <alan@lxorguk.ukuu.org.uk> Cc: Greg KH <gregkh@suse.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/kernel-parameters.txt6
1 files changed, 6 insertions, 0 deletions
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index e9261e938f6a..c357a31411cd 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -872,6 +872,12 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
If specified, z/VM IUCV HVC accepts connections
from listed z/VM user IDs only.
+ keep_bootcon [KNL]
+ Do not unregister boot console at start. This is only
+ useful for debugging when something happens in the window
+ between unregistering the boot console and initializing
+ the real console.
+
i2c_bus= [HW] Override the default board specific I2C bus speed
or register an additional I2C bus that is not
registered from board initialization code.