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Bug#448467: xserver-xorg-video-intel: Thinkpad brightness keys don't work

On Saturday, December 22, 2007 9:12 am Brice Goglin wrote:
> Henrique de Moraes Holschuh wrote:
> > On Sat, 15 Dec 2007, Marcus Better wrote:
> >> I just tried with a new one, but the brightness is still broken.
> >> It requires "native" or "combination" mode.
> >
> > I'd like to see X.org talking to the kernel to find out and
> > coordinate which mode should be used...
> Jesse,
> Could you please have a look at
>     http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=448467
> and see if you can find a solution with the thinkpad guys for correct
> backlight handling? Marcus tried with intel git about a week ago, it
> didn't go very well.

The backlight situation is rather unfortunate.  As you've already 
discovered, there are several different ways backlights are controlled 
on various platforms, and some of them are incompatible.

The Intel X driver now tries to talk to the kernel drivers directly (via 
the /sys/class/backlight interface) starting with the thinkpad_screen 
driver, followed by acpi_video1 and acpi_video0.  Depending on how your 
kernel is configured, this may work perfectly or result in the drivers 
fighting one another for backlight adjustments.

Since on Thinkpads, the kernel method is available (either via the 
kernel thinkpad driver or ACPI) you should try to use that, but it may 
be that the acpi_video1 method is your best choice.  You can try that 
interface by changing the order of the string array in i830_lvds.c 
around line 67.

If you want to use one of the other methods (which may provide you with 
more possible backlight levels) you should unload all kernel backlight 
drivers prior to loading X (or disabling their backlight interfaces as 
in the case of the thinkpad driver); that may give you a good user 
experience too...

Sorry if I missed anything in the initial bug report, I'm on vacation at 
my mother-in-law's right now, with a free wireless connection kindly 
provided by someone called 'jazzman' (at least according to his 
ESSD :).


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