Display brightness control in "power management" does not work anymore

[farhan]

Hi,

My screen brightness control was working fine since i installed Kubuntu last week but today when i started the computer i was not able to change the brightness level. In "power management" tool, when i change the brightness to different levels it does not change the brightness at all. Recent changes that i made were installing nvidia driver from jockey and using BleachBit to clean system. So i do not know if these changes did something to power management settings or if there is some other problem.

I have dual boot and in windows brightness settings is working fine.

Any help to fix this issue would be of great great value to me.

Farhan
Graphics Nvidia Geforce GT 420M

[SteveRiley]

Since you're using the nVidia binary driver, you'll need to modify a file on your computer to get brightness controls to work.

1. Press Alt+F2 to bring up the KRunner.

2. Enter kdesudo kate /etc/X11/xorg.conf

3. Find the part that begins with Section "Screen".

4. Inside this section, add the following:

    Option         "RegistryDwords" "EnableBrightnessControl=1"

5. Save the file and quit the editor.

6. Log out and log back in.

Here's an example file, with the required line shown in bold:

# nvidia-settings: X configuration file generated by nvidia-settings
# nvidia-settings:  version 313.09  (buildd@mekbuda)  Wed Dec 12 17:04:43 UTC 2012

Section "ServerLayout"
    Identifier     "Layout0"
    Screen      0  "Screen0" 0 0
    InputDevice    "Keyboard0" "CoreKeyboard"
    InputDevice    "Mouse0" "CorePointer"
    Option         "Xinerama" "0"
EndSection

Section "Files"
EndSection

Section "InputDevice"
    # generated from default
    Identifier     "Mouse0"
    Driver         "mouse"
    Option         "Protocol" "auto"
    Option         "Device" "/dev/psaux"
    Option         "Emulate3Buttons" "no"
    Option         "ZAxisMapping" "4 5"
EndSection

Section "InputDevice"
    # generated from default
    Identifier     "Keyboard0"
    Driver         "kbd"
EndSection

Section "Monitor"
    # HorizSync source: edid, VertRefresh source: edid
    Identifier     "Monitor0"
    VendorName     "Unknown"
    ModelName      "Lenovo Group Limited"
    HorizSync       56.5 - 67.8
    VertRefresh     50.0 - 60.0
    Option         "DPMS"
EndSection

Section "Device"
    Identifier     "Device0"
    Driver         "nvidia"
    VendorName     "NVIDIA Corporation"
    BoardName      "NVS 4200M"
EndSection

Section "Screen"
    Identifier     "Screen0"
    Device         "Device0"
    Monitor        "Monitor0"
    DefaultDepth    24
    Option         "Stereo" "0"
    Option         "metamodes" "nvidia-auto-select +0+0"
    [B]Option         "RegistryDwords" "EnableBrightnessControl=1"[/B]
    SubSection     "Display"
        Depth       24
    EndSubSection
EndSection

[farhan]

Hi Steve,

Thanks again for your support. I did as you told me above but brightness control still doesn't work. Any other suggestion?

[SteveRiley]

Hm...that's always worked for me on nVidia-equipped machines. Have you consulted Google?

[farhan]

yes i searched over the Google particularly ubuntu forums. I tried "xbacklight" and adding the above mentioned line in "device section"but didn't work. By the way i am using the latest nvidia driver (310) which is mentioned as experimental in jockey. Is it possible that this nvidia driver has some issue?