trident XP4m32 brightness change

Mathieu Lacage mathieu.lacage at
Mon Jul 23 00:25:12 PDT 2007

On Sun, 2007-07-22 at 18:42 +0200, René Rebe wrote:

> > > Maybe try to figure out what register is used for the brightness control
> > > and add support the "backlight change via xrandr" (also see xbacklight)
> > > to have full control about the behaviour.
> > 
> > The current trident driver seems to contain already code to control the
> > brightness. I suspect that this code is controlled by the
> > "GammaBrightness" config file option which is not super useful to me.
> Gamma is not brightness. it is the non-linear mapping of color values.

The documentation of the "GammaBrightness" option seems to imply that
you can control separately the "gamma" and the "brightness".

> Based on the initial mail I thought you want to change your display
> backlight in order to save power?


> > xbacklight seems to require randr 1.2 support which is not in my current
> > server. I suspect that this would require adding full xrandr 1.2 support
> > to the trident driver, right ? Or could I manage to just put enough
> > support to make this work ?
> You do not need to implement the BACKLIGHT atom, for an example see:
>   xf86-video-intel-2.1.0/src/i830_lvds.c

will look at this.

thank you,

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