[PATCH 3/3] drm/panic: Add a kmsg dump screen

[Javier Martinez Canillas]

Jocelyn Falempe <jfalempe at redhat.com> writes:

> On 31/05/2024 11:32, Javier Martinez Canillas wrote:
>> Jocelyn Falempe <jfalempe at redhat.com> writes:
>> 
>>> Add a kmsg dump option, which will display the last lines of kmsg,
>>> and should be similar to fbcon.
>>> Add a Kconfig choice for the panic screen, so that the user can
>>> choose between this new kmsg dump, or the userfriendly option.
>>>
>>> Signed-off-by: Jocelyn Falempe <jfalempe at redhat.com>
>>> ---
>>>   drivers/gpu/drm/Kconfig     |  21 +++++
>>>   drivers/gpu/drm/drm_panic.c | 151 +++++++++++++++++++++++++++---------
>>>   2 files changed, 136 insertions(+), 36 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
>>> index 9703429de6b9..78d401b55102 100644
>>> --- a/drivers/gpu/drm/Kconfig
>>> +++ b/drivers/gpu/drm/Kconfig
>>> @@ -137,6 +137,27 @@ config DRM_PANIC_DEBUG
>>>   	  This is unsafe and should not be enabled on a production build.
>>>   	  If in doubt, say "N".
>>>   
>>> +choice
>>> +	prompt "Panic screen formater"
>>> +	default DRM_PANIC_SCREEN_USERFRIENDLY
>>> +	depends on DRM_PANIC
>>> +	help
>>> +	  This option enable to choose what will be displayed when a kernel
>>> +	  panic occurs.
>>> +
>>> +	config DRM_PANIC_SCREEN_USERFRIENDLY
>>> +		bool "Default user friendly message"
>>> +		help
>>> +		  Only a short message telling the user to reboot the system.
>>> +
>>> +	config DRM_PANIC_SCREEN_KMSG
>>> +		bool "Display the last lines of kmsg"
>>> +		help
>>> +		  Display kmsg last lines on panic.
>>> +		  Enable if you are a kernel developer, and want to debug a
>>> +		  kernel panic.
>>> +endchoice
>> 
>> Why having it as a compile time option and not a runtime option ? AFAICT
>> this could be a drm.panic_format= kernel command line parameter instead.
>
> Yes, I didn't think about it. That would allow to get more debug 
> information from a user without rebuilding the kernel.
>
> I'll prepare a v2 with that.
>

Awesome, thanks!

> I prefer to use a drm.panic_screen=, as "format" might be confusing with 
> the color format ?
>

Indeed. I named _format because your prompt had "formater" in it, but
agree that _screen makes more sense and is easier to understand.

-- 
Best regards,

Javier Martinez Canillas
Core Platforms
Red Hat