After upgrading my Toshiba Z830 Ultrabook to 12.04 (Precise Pangolin) I noticed that the ability to control the screen back-light was not working using the Toshiba Fn F6/F7 keys.
Thanks to http://www.linlap.com/wiki/acer+aspire+s3 the solution was found quite quickly.
sudo vim /etc/default/grub
This will open the grub configuration file. (Grub is the initial boot selection software)
To be able to dim the screen brightness, You’ve got to modify the line:
to these two lines:
GRUB_CMDLINE_LINUX="quiet splash pcie_aspm=force i915.i915_enable_rc6=1 i915.lvds_downclock=1 acpi_osi=Linux acpi_backlight=vendor elevator=noop"
Another neat tip: intel-gpu-tools can be used to control brightness from the commandline.
# will set brightness at 50%
EDIT [2012-08-24]: to avoid issues on resume you need to add a script to the
sudo vim /etc/pm/sleep.d/20_wakeup
Add the following:
case "$1" in
echo 7 > /sys/class/backlight/toshiba/brightness
Mark the file as executable
sudo chmod +x /etc/pm/sleep.d/20_wakeup