[Bug 82634] [snb] backlight issue on TOSHIBA PORTEGE R830 after suspend/resume

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=82634

--- Comment #19 from Hans de Goede <jwrdegoede at fedoraproject.org> ---
Hi Jani,

(In reply to Jani Nikula from comment #18)
> (In reply to Hans de Goede from comment #17)
> > Created attachment 116122 [details] [review] [review]
> > [PATCH] drm: i915: Add an enable_backlight_control module parameter
> 
> Hans, while I truly appreciate your efforts in fixing backlight issues, I
> really *really* would like to exhaust all other options before adding such
> module parameters. It should be made to Just Work(tm).

I understand and I agree, but it seems that there just is not enough manpower
to look into backlight breaking on (somewhat) older machines such as this one.
The reporter has attached register dumps of the i915 both before and after
suspend / resume and no one seems to have seriously looked into these...

Also having 2 pieces of code (the i915 driver and the firmware) poling at the
same registers during suspend / resume is just wrong, that it happens to often
work does not make it less wrong, we really should always be loading either the
i915 or the acpi-video backlight driver and not both.

> All the cargo culting forum posts telling people to tweak their i915 module
> parameters are giving us headaches. We've even made some of our module
> parameters taint the kernel, and we won't look at bugs if people changed
> them from their platform specific defaults. Just wanted to let you know my
> opinion right from the start.

Note that my plan (if this helps) includes a follow up patch which allows
getting the same result via a quirk and then to add a quirk for this (and
likely also some other Toshiba models). So things will just work, and we won't
have people referencing ancient ubuntu form posts and taking dark magic
settings from there to make things work.

Regards,

Hans

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