Cannot adjust brightness via Fn key

Question

I just set up a new Arch with Gnome 3.2. Until now, everything seems to work fine, except for the brightness adjustment. When I try to adjust the brightness from within the Gnome settings or with Fn+☼↑, the screen flickers for some seconds and afterwards the brightness stays the same (Fn variant) or has changed (Gnome settings). It seems like some other part of the system insists on keeping the brightness as is, there is a fight and this other part wins.

edit:

The Hardware is a Samsung N130 Netbook with an Intel 945GME graphics controller.

update: The culprit of this manifests itself as this line in /var/log/messages:

samsung_laptop: SABI set command 0x01 failed with completion flag 0xaa and data 0xff

Some research led to this, which says that a patch for the problem is on its way into the 3.2 kernel.

Answer 1

You may try the following, this might bring you luck.

1. Open your terminal (Ctrl+Alt+T)
2. sudo vi /etc/default/acpi_support

3. Find and enable this line (remove the # behind):

   ENABLE_LAPTOP_MODE=true

4. Install the laptop mode tool from Laptop Mode
5. sudo vi /etc/laptop-mode/laptop-mode.conf

# Enable laptop mode when on AC power.
ENABLE_LAPTOP_MODE_ON_AC=1
# Should laptop mode tools control LCD brightness?
CONTROL_BRIGHTNESS=1
# Commands to execute to set the brightness on your LCD
BATT_BRIGHTNESS_COMMAND="echo 0"
LM_AC_BRIGHTNESS_COMMAND="echo 9"
NOLM_AC_BRIGHTNESS_COMMAND="echo 9"
BRIGHTNESS_OUTPUT=”/sys/class/backlight/acpi_video1/brightness”

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You can read the instructions before editing the file:

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# * If your system has the file “/proc/acpi/video/VID/LCD/brightness” (VID may
# be VID1 or similar), use this file as BRIGHTNESS_OUTPUT, and use
# the command “echo “. The possible values can be listed using the
# command
#
# cat /proc/acpi/video/VID/LCD/brightness
# * If you have a file /sys/class/backlight/…/brightness, then you can use
# that file as BRIGHTNESS_OUTPUT, and the command “echo “.
#
# As far as I understand it the values are between 0 and
# the value contained in the file /sys/class/backlight/…/max_brightness.
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Answer 2

I've been having the same problem with my Dell Laptop running Xubuntu. The solution offered by Blue Sky hasn't worked for me, but I was able to set up a script (to be run thru sudo).

cd /sys/class/backlight/intel_backlight
cat max_brightness > brightness

There is also a /sys/class/backlight/dell_backlight directory, but that didn't seem to work on my system.

Answer 3

After hacking around for hours and getting to various states of half-working brightness up/down Fn keys I ended up installing samsung-tools - this guide worked for me nicely.

I was able by pressing Fn keys to decrease brightness only. But using terminal I was able to adjust brightness normally - increase/decrease.

Samsung np300v5z, Ubuntu 12.04.