I am using Ubuntu 12.04 on a Samsung Laptop (300e4a-ad1 model). To get brightness adjustment through multimedia keys working properly i've ever used these lines on /etc/default/grub file:
Until the kernel 3.2.0-26-generic it was ok but after any kernel update i can't adjust brightness using the newer kernel through multimedia keys. With acpi_osi=Linux acpi_backlight=vendor it doesn't change nothing and without it or with acpi_osi=Linux acpi_backlight=legacy, the environment is crashing when i try to change the brightness.
GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian`
GRUB_CMDLINE_LINUX_DEFAULT="quiet acpi_osi=Linux acpi_backlight=vendor enable_mtrr_cleanup splash"
I think that it's not related to kernel as i compared the both config files, dmesg and modules. Anybody seen or is experiencing the same problem?