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My laptop has keyboard buttons for adjusting screen brightness. After a Debian Squeeze re-installation, they don't work no more.

[laptop] Acer TravelMate 6592; I use Fn< to decrease the brightness and Fn> to increase it.

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These things can sometimes be brand/model specific so a bit of information about the laptop in question might be useful. –  Steven D Feb 10 '11 at 17:42
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4 Answers 4

Is it a problem of key mapping or a problem of acpi support ?

Check in /proc/acpi/ if you have some entries like this one : /proc/acpi/video/GFX0/LCDD/brightness

If you find it, try to set a value maybe like this :

echo "4" > /proc/acpi/video/GFX0/LCDD/brightness
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I don't have the "/prc/acpi/video" directory. My kernel is 2.6.32 on Debian. –  Tshepang Feb 24 '11 at 13:12
    
What distro do you use? –  Tshepang Feb 24 '11 at 13:18
    
I use Ubuntu, but with a kernel on my own (2.6.37). –  profy Feb 25 '11 at 20:23
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Add "acpi_osi=Linux" to loader


Example:

title Arch Linux
root (hd0,1)
kernel /vmlinuz26 root=/dev/sda5 ro acpi_osi=Linux
initrd /kernel26.img
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What is loader? –  Tshepang Feb 24 '11 at 13:15
    
I've tried this, and I'm, still sitting with the problem. –  Tshepang Feb 24 '11 at 15:34
    
It's a /boot/grub/menu.lst –  1vanu4 Feb 27 '11 at 22:48
    
In my situation it helped me. –  1vanu4 Feb 27 '11 at 22:49
    
SO you can now adjust brightness using special laptop shortcuts, as in my case? –  Tshepang Mar 25 '11 at 20:59
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up vote 1 down vote accepted

It's probably the case that it got removed in the latest Debian Squeeze kernel (which is where the problem was), and it's now put back in 2.6.38. I say that because it was working way before Squeeze was released (and I only use pristine Debian kernel packages).

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If you can change your brightness with root user by typing:

echo 100 > /sys/class/backlight/<xxx>/brightnes

Then, you can follow this link: http://askubuntu.com/a/82320/301773

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