Comment 29 for bug 226894

MacBook Pro v.3 (Santa Rosa) running Ubuntu 8.10 , kernel 2.6.27-11-generic , has problems with backlight.
The module "mbp_nvidia_bl" does not load by default. Loading the module manually and writing the desired back-light value (a number between 1 to 15) to /sys/class/backlight/mbp_backlight/brightness solves the problem. (You need to "sudo -i" )
Note that when you connect the laptop to power, the back-light goes back to the default value (i guess 15) , in which case you have to set it to 15 and then set it to your desired value the way I mentioned above.