I'm using a samsung R590 laptop (wich is quite similar to the R580) and I got my brightness controls to work on ubuntu 10.10 like this:
I first installed the samsung-tools these fixed all of my other fn buttons. This is just a tip and not necessary (i think) for the funcionality of the brightness buttons.
Part 1: install drivers
1. Disable previous drivers (System/Additional drivers)
2. Download drivers from www.nvidia.com (use save as)
3. Reboot in a recovery shell
5. Follow install instructions. (If previously installed the standard nvidia drivers, you should let the setup create a textfile wich will disable the previous drivers. After that, you should reboot and try again form step 3.)
sudo sh ./<downloaded file>
Part 2: adjust grub
2. Add acpi_backlight=vendor to the default command line, the line should then look like this:
sudo gedit /etc/default/grub
3. Part 3: enable screen adjustments
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_backlight=vendor"
2. Add the following line in the device section: Option "RegistryDwords" "EnableBrightnessControl=1"
sudo gedit /etc/X11/xorg.conf
My own section looked like this:
Part 4: reboot and everything should work
VendorName "NVIDIA Corporation"
Option "RegistryDwords" "EnableBrightnessControl=1"