Closing since the brightness control itself works starting with Karmic as long as you've upgraded your BIOS to at least v.11CA. Please see the link in #23 for alternative solutions if you don't want to upgrade your BIOS.
However, there are related issues which don't affect the brightness control itself: Oneiric users will find following bug 810093 useful. The issue about completely enabling/disabling baclight (eg screen on/off) with Fn-F5 button is tracked at bug 296489.
Closing since the brightness control itself works starting with Karmic as long as you've upgraded your BIOS to at least v.11CA. Please see the link in #23 for alternative solutions if you don't want to upgrade your BIOS.
However, there are related issues which don't affect the brightness control itself: Oneiric users will find following bug 810093 useful. The issue about completely enabling/disabling baclight (eg screen on/off) with Fn-F5 button is tracked at bug 296489.