Comment # 16 on bug 1180591 from Maurizio Galli

(In reply to Takashi Iwai from comment #15)
> Thanks.
> 
> I checked briefly between v5.7 and v5.8, but there is no change in either
> driver/acpi/video_detect.c or drivers/acpi/acpi_video.c.  So the ACPI code
> (in those areas) didn't change, and something else (also in ACPI) must be
> the cause of the regression.  It's hard to tell for now.
> 
> And, I looked at the backlight support on Apple machines and they are...
> well... messy.  There is apple-gmux driver that supports things on some
> devices but it's only for ACPI APP000B, which isn't enabled on yours.
> 
> At this moment, the best thing we can do is to git bisect.  But of course it
> takes time (and patience).

It's fine if it will take time, for the time being I'll look at the screen with
sunglasses on :P.

Thank you for looking into it.