Comment 16 for bug 921321

(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