xbacklight on intel

Jesse Barnes jbarnes at virtuousgeek.org
Wed Nov 28 12:42:52 PST 2007

On Wednesday, November 28, 2007 12:18 am Khashayar Naderehvandi wrote:
> > So your machine is defaulting to the native register interface.  I wonder
> > if
> > it should be using the legacy interface instead?  Can you try
> >  $ xrandr --output LVDS --set BACKLIGHT_CONTROL legacy
> > and see if xbacklight works for you then?
> >
> > After changing it to legacy it still does not work. However, runing
> xbacklight -get I know get a figure (around 0.5), whereas before switching
> over to legacy xbacklight returned the mysterious string "nan".
> Anyway, xbacklight -set, -inc, or -dec does not yield any result.

Hm, well it might just be that you have an unsupported platform.  Some laptops 
(notably Thinkpads) have their own backlight controllers that aren't wired up 
to the GPU registers at all.  In the Thinkpad case there's a kernel driver 
you can load to get access to the backlight.

Have you looked around for an out-of-tree kernel module that supports the 
extra features of your lifebook?  If one exists, it may have 
a /sys/class/backlight interface that the Intel driver can use...


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