Bug#462190: xserver-xorg-video-ati: backlight control doesn't work with Radeon Mobility M9

[Alex Deucher]

On Jan 24, 2008 3:17 PM, Ingo Saitz <Ingo.Saitz at stud.uni-hannover.de> wrote:
> Moin
>
> On Wed, Jan 23, 2008 at 11:14:30AM -0500, Alex Deucher wrote:
> > backlight control is an oem specific mess.  In order to fix lid
> > support, we had do mess with some of the bios scratch regs.
>
> Oh yes, the lid switch does not work, too. But that didn't bother me so
> far... :)
>
> > Unfortunately, these changes seem to break backlight on some laptops,
> > but not others.
>
> Maybe this should be an option in the xorg.conf file, if autodetecting
> the method to deal with the backlight controls is not really easy? So
> you could even cover new models which might need this messy fix.

We'll probably need some sort of option.  I'll know more when I've had
time to delve into that a bit more.  Right now you can restore the old
behavior by commenting out:

 if (info->IsMobility)
	RADEONInitBIOSRegisters(pScrn, info->ModeReg);

in legacy_crtc_mode_set() in legacy_crtc.c

Alex