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I have a laptop mySN QMG6 / Chiligreen Mobilitas NW which is Quanta TW9 barebone with intel i3 and nvidia 335m GT onboard. On ubuntu distros 10.04, 10.10, 11.04 and 11.10 i had problem with changing screen backlight with nouveau and nvidia drivers. FN+F4/F5 buttons did not change my brightness. I tried to edit xorg.conf, adding

Option “RegistryDwords” “EnableBrightnessControl=1″

Also tried to add some lines to grub

acpi_osi="Linux" acpi_backlight=vendor

Neither worked for me. Today I installed Ubuntu 12.04 beta2 and... With nouveau driver my FN key works, and changes the brightness (is it a new 3.0.22 linux kernel, or patched nouveau driver, i don't know). This is a big step forward. But, when installing proprietary nvidia driver (295.33) FN button stops working and i can't change brightness. I also tried workaround with xorg and grub with no result. Tried to install acpi from apt - no result. Is there anything left to try? I really need that nvidia driver working with FN keys, as i would like to have a working 3D acceleration.

P.S. Does the nouveau driver has 3d acceleration like nvidia drivers??? If there is need to provide some log data, please write what should i print, as i'm a bit new to Ubuntu.

P.P.S. Same problems i had with other Linux distros (Mint, Fedora and others)

P.P.P.S. Other FN buttons work with both drivers (Mute, VOL UP/DOWN, WiFi on/off, Bluetooth, Sleep, Start/Pause, Stop, Next/Prev song)

Some new thoughts...

CONFIG_BACKLIGHT_GENERIC=m

could this be an issue? Made this by

grep BACKLIGHT /boot/config-3.2.0-22-generic-pae

Full grep output can be viewed here: http://pastebin.com/sMRd2Z4k

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3 Answers

Type su and enter root password in terminal

And then type this :

echo "x" > /sys/class/backlight/acpi_video0/brightness

where x = 0 - 7

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Thanks for a hint. Tried to type this : echo "x" > /sys/class/backlight/acpi_video0/brightness where x = 0 - 7 But got an answer:bash: /sys/class/backlight/acpi_video0/brightness: No such file or directory –  Vladimir Apr 10 '12 at 10:57
    
While this link may answer the question, it is better to include the essential parts of the answer here and provide the link for reference. Link-only answers can become invalid if the linked page changes. –  hexafraction Aug 17 '12 at 14:04
    
removed the link .. ;) –  Sakti Aug 20 '12 at 16:15
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Got my nvidia backlight working with https://github.com/guillaumezin/nvidiabl So there was no need to reconfigure kernel or other things

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use my new method for Nvidia Graphics and it hopefully will help you.. thats only thing worked for me.

http://askubuntu.com/a/179063/82136

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