http://forums.opensuse.org/english/get-technical-help-here/laptop/478677-cant-manage-brightness-opensuse-12-2-a.html

The correct kernel parameter should be acpi_backlight=vendor acpi_osi=Linux.
Add it to the end of the GRUB_CMDLINE_LINUX variable in the /etc/default/grub file.
Then run the grub2-mkconfig -o /boot/grub2/grub.cfg command ...