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gregghz
Asked: 2011-04-13 00:27:45 +0800 CST

Xbacklight can only decrease brightness

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I'm running Ubuntu 10.10 on a Cr48. I'm attempting to bind xbacklight -dec 10 to f6 (decrease brightness in chrome os) and xbacklight -inc 10 to f7 (increase brightness in chrome os). The decrease command works fine, but the increase command appears to have no effect. It's the same whether I run the command from the command line or use the bindings I set in CompizConfig Settings Manager.

cr-48

3 Answers

  1. For me, the smallest increase that works is 13. Decreases of any size dim the screen, although I cannot see any difference between -dec 1 and -dec 10

    • 4

  2. You can change the brightness by changing some setting files.

    1. Open a terminal

    2. Login as root. sudo su

    3. Type echo -n 100 > /proc/acpi/video/DVGA/LCD/brightness.

    4. If you get a "No such file or directory" error, replace DVGA with VGA.

    5. 100 is the highest brightness level (100%). For example, just change the 100 to 50, to dim your display by 50 percent.

    I hope this helped you and I don't know if it's possible to fix this bug with xbacklight. If you really want to work with xbacklight, I'd create a bug report.

    -- Daniel

    • 1

  3. I had this same issue at first... I think it's that the default is to take 20 steps to complete the transition... this combined with your small 10% change breaks things it seems.

    I got mine to work by making my functions as such:

    brightness up => xbacklight -steps 1 -inc 20 brightness down => xbacklight -steps 1 -dec 20

    • Also, I saw in the above answer about LCD vs OVGA. You won't get LCD becuase it's a notebook. They should be OVGA ... something like: /proc/acpi/video/OVGA/DD01/

    But if you setup your steps to be 1 and increase your percent changes to 20 or more you should be just fine with xbacklight!

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