[Nouveau] [Bug 39550] Brightness stuck to low value after suspend/resume

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=39550

--- Comment #13 from rick <rick.hendricksen at gmail.com> 2011-09-25 05:08:35 PDT ---
(In reply to comment #12)
> Rik
> 
> Can you please indicate what exactly do you mean with
> 
> "Brightness control does not work with this option for me."
>
> Does it work before suspending the system?
Brightness control does not work before suspend, I did not try suspending. So
no.
> Can you please attach your dmesg log, as it is the one relevant in this case
> (whereas xf86-video-nouveau, mesa and libdrm are not)

will post in a few minutes (need to get laptop)

> 
> Auke, Rik
> 
> AFAIK brightness/backlight is(can be) controlled via
> 1. ACPI
> 2. platform specific - (asus-laptop, samsung-laptop, thinkpad ...)
> 3. the gpu/card itself
> 
> On various system different ones work correctly
> 
> By default nouveau does not register it's device if an ACPI one exists
> Note that the blob has similar behaviour but they have an option to override
> it.
> 
> If you suspect that the ACPI backlight control is buggy you can disable it by
> appending "acpi_backlight=vendor" to your kernel command line

I tried that. It works exactly the same as without this option. Brightness
control works fine before suspend, fails after.

> This will fall back to either 2. or 3. - dmesg will tell you which one
> 
> Feel free to give it a try
> 
> Cheers
> Emil

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