linux-kernel - Re: [PATCH] ACPI: video: Fix name collision with architecture's video.o

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Date: Thu, 16 May 2024 17:03:25 +0200
From: Hans de Goede <hdegoede@...hat.com>
To: "Rafael J. Wysocki" <rafael@...nel.org>,
 Thomas Zimmermann <tzimmermann@...e.de>
Cc: lenb@...nel.org, arnd@...db.de, chaitanya.kumar.borah@...el.com,
 suresh.kumar.kurmi@...el.com, jani.saarinen@...el.com,
 linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
 intel-gfx@...ts.freedesktop.org, linux-arch@...r.kernel.org,
 linux-fbdev@...r.kernel.org, dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH] ACPI: video: Fix name collision with architecture's
 video.o

Hi,

On 5/16/24 3:04 PM, Rafael J. Wysocki wrote:
> CC Hans who has been doing the majority of the ACPI video work.
> 
> On Thu, May 16, 2024 at 2:43 PM Thomas Zimmermann <tzimmermann@...e.de> wrote:
>>
>> Commit 2fd001cd3600 ("arch: Rename fbdev header and source files")
>> renames the video source files under arch/ such that they does not
>> refer to fbdev any longer. The new files named video.o conflict with
>> ACPI's video.ko module.
> 
> And surely nobody knew or was unable to check upfront that there was a
> video.ko already in the kernel.

Sorry, but nack for this change. I very deliberately kept the module-name
as video when renaming the actual .c file from video.c to acpi_video.c
because many people pass drivers/video/acpi_video.c module arguments
on the kernel commandline using video.param=val .

Try e.g. doing a duckduckgo search for 1 off:

"video.only_lcd"
"video.allow_duplicates"
"video.brightness_switch_enabled"

And you will find a lot of hits. The last one is even documented as
being "video.brightness_switch_enabled" in the main kernel-parameters.txt
as well as separately:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/admin-guide/kernel-parameters.txt#n39
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/admin-guide/kernel-parameters.txt#n7152
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/firmware-guide/acpi/video_extension.rst#n118

https://wiki.archlinux.org/title/Lenovo_ThinkPad_X1_Carbon#Brightness_control

If you rename this module then peoples config will break for
a whole lot of users.

So lets not do that and lets rename the new module which is causing
the conflict in the first place instead.

Regards,

Hans