Re: [PATCH 00/22] Fallback to native backlight

[Akihiko Odaki]

On 2022/10/25 3:11, Jani Nikula wrote:
> On Tue, 25 Oct 2022, Akihiko Odaki <akihiko.odaki@xxxxxxxxxx> wrote:
> > That aside, the first patch in this series can be applied without the
> > later patches so you may have a look at it. It's fine if you don't merge
> > it though since it does not fix really a pragmatic bug as its message says.
>
> I think it's problematic because it needlessly ties i915 backlight
> operation to existence of backlight devices that may not be related to
> Intel GPU at all. The direction should be multiple supported backlight
> devices, across GPUs and connectors, but only one per display.
>
> BR,
> Jani.

Unfortunately it is the current situation (even without this patch), and 
this patch is not meant to fix the particular issue.

This patch replaces the following expression:
acpi_video_get_backlight_type() == acpi_backlight_native

As you can see, acpi_video_get_backlight_type() doesn't take a parameter 
which represents the backlight currently being operated. The problem is 
known and documented in "Brightness handling on devices with multiple 
internal panels" section of Documentation/gpu/todo.rst.

The exiting solution is based on the assumption that no device with i915 
and multiple internal backlights.

Regards,
Akihiko Odaki