Backlight control
 

Hello, I'm running Slackware-current on a Compaq Presario laptop, and I'd like to know how to (if possible) activate lcd backlight control. With this, I mean the following: dim the backlight when the AC is unplugged, i.e., in battery mode. None of the kernel laptop extras apply for me (Toshiba, Sony, etc.).

Also, it would be nice to be able to control the backlight also from the corresponding function keys in my laptop keyboard; this is not so important as the above though (xsetbacklight gives me "No outupt has backlight property").

At least in the Unix world, this laptop supports that kind of stuff because it worked with FreeBSD.

Any help is valuable!