Hello,
I wrote a little Linux driver based on Andy Wingo's work (
http://wingolog.org/pub/nvbacklight-0.1.tar.bz2) and MacTel Team (
https://launchpad.net/~mactel-suppor..._filter=karmic) that enables the control of laptop backlight connected to nVidia chip using the /sys/class/backlight interface.
Source and binary download are now available on github:
https://github.com/guillaumezin/nvidiabl
Guillaume