how to configure contrast buttons on Squeeze laptops ?

[David Cho-Lerat <david.lerat@asterion.fr>]

Hi list,

I've installed Squeeze on 3 different laptops recently :
a Dell, a Packard Bell and a Toshiba. On the Dell, the
contrast buttons work : I can press "Fn" + "Up"/"Down"
to set the screen contrast level.

On the  others, though, they don't (in addition, on the
Toshiba the "mute" key doesn't work either).

Where should I look ? Is this related to Xorg ? the video
card driver ? something else ?

Thanks all !

Toshiba Satellite L775-18Z : nVidia GeForce 315M
Dell Studio 1735 : ATI Mobility Radeon HD 3650
Packard Bell EasyNote LM : ATI Mobility Radeon ? (have to check..)