[Intel-gfx] Regarding the laptop with the BOE panel with ID 2270

[Lyude Paul]

Hey Aaron! A while ago you submitted some patches for a machine that appears to
have needed the VESA backlight interface in order to control the panel backlight
on it:

https://patchwork.freedesktop.org/patch/394371/

We're currently dealing with a different laptop where the machine advertises
VESA backlight support, which we end up defaulting to after failing to probe for
the Intel backlight interface, but this backlight interface appears to be
broken:

https://gitlab.freedesktop.org/drm/intel/-/issues/3158

The fix I was hoping to do was to just not attempt probing for the VESA
backlight interface, but if we did that then it's possible that the backlight
controls for the machine you submitted your patch for would stop working out of
the box. However, it occurred to me that we never tried the Intel backlight
interface on your machine - and if it works there, then we'd likely be able to
require the VBT to advertise VESA support before using it and fix the machine in
the gitlab issue I've linked.

Do you think you could test this for us? If you build the latest kernel from
drm-tip, the easiest way should be to boot up with
"i915.enable_dpcd_backlight=3" and just see if your backlight controls still
work as expected.
-- 
Sincerely,
   Lyude Paul (she/her)
   Software Engineer at Red Hat
   
Note: I deal with a lot of emails and have a lot of bugs on my plate. If you've
asked me a question, are waiting for a review/merge on a patch, etc. and I
haven't responded in a while, please feel free to send me another email to check
on my status. I don't bite!