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Old 11-07-10, 09:29 AM   #1
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Join Date: Jan 2009
Posts: 10
Default Backlight/Brightness control not working

Hi Forum,

I write this thread because my backlight control auf my DELL Vostro 3700 doesn't work like it should do.

I can control it with the hardware keys FN+Up/Down... but this was most time a litte bit buggy - sometimes I have to set the backlight to the lowest value and than when I scale it up again its reacting first time or it react right (to make it complete bright)

But now I found, that I have to set

Option	"RegistryDwords"	"EnableBrightnessControl=1"
in Xorg.conf section of the driver, which I also did.

The main problem is, that I can not control the brightness per software with as example:
echo 0 | sudo tee /sys/devices/virtual/backlight/acpi_video0/brightness
echo 0 | sudo tee /sys/class/backlight/acpi_video0/brightness
echo 6 | sudo tee /proc/acpi/video/PEGP/LCD/brightness
None of them let the backlight react.

When I monitor all values with

watch -n1 "cat /sys/class/backlight/acpi_video0/brightness && cat /sys/devices/virtual/backlight/acpi_video0/brightness && cat /proc/acpi/video/PEGP/LCD/brightness"
and use the function keys to change the brightness I can see that all values get changed...

Any Idea what I can do?

I use Ubuntu Lucid Lynx with Nvidia driver 260.19.12 and kernel 2.6.36

ThomasC is offline   Reply With Quote