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Thread: Cannot change backlight brightness Ubuntu 14.04

  1. #11
    Join Date
    May 2014
    Beans
    214

    Re: Cannot change backlight brightness Ubuntu 14.04

    Quote Originally Posted by cyrus_the_virus View Post
    I used this/ article that suggests making a change in xorg.conf. I removed this later because it does solve my problem. I think it just tells to which file the brightness value should be echoed, but since echoing a value manually does not work this solution does not work either.

    Here is the output of the commands that you gave me:

    Code:
    $ cat /proc/cmdline
    BOOT_IMAGE=/boot/vmlinuz-3.13.0-29-generic root=UUID=4e04ddb0-3020-4b02-827f-635306f670db ro quiet splash video.use_native_backlight=1 vt.handoff=7
    Code:
    $ ls /sys/class/backlight
    intel_backlight
    Code:
    $ cat /var/log/Xorg.0.log | grep backlight
    [    11.054] Kernel command line: BOOT_IMAGE=/boot/vmlinuz-3.13.0-29-generic root=UUID=4e04ddb0-3020-4b02-827f-635306f670db ro quiet splash video.use_native_backlight=1 vt.handoff=7
    [    11.101] (--) intel(0): found backlight control interface intel_backlight (type 'raw')
    Code:
    $ for interface in /sys/class/backlight/*; do echo $interface; cat $interface/actual_brightness; cat $interface/max_brightness; done
    /sys/class/backlight/intel_backlight
    4882
    4882
    Note that this was done with video.use_native_backlight=1

    Have you tried to set the brightness using
    Code:
    echo 3500 | sudo tee /sys/class/backlight/intel_backlight/brightness
    with and without video.use_native_backlight?

    It sounds like using the 3.14.5 kernel fixes a backlight bug on the XPS13 per a bug report https://bugs.freedesktop.org/show_bug.cgi?id=76276

  2. #12
    Join Date
    Dec 2007
    Beans
    78

    Re: Cannot change backlight brightness Ubuntu 14.04

    Hi, sorry for my late reply.

    Today I wanted to look into your latest comments and I found out that the display is completely broken now. There is no backlight at all black even during the initial boot up. So, I think it is safe to assume that this is a hardware problem. I will contact Dell support to send it back for repair.

  3. #13
    Join Date
    May 2014
    Beans
    214

    Re: Cannot change backlight brightness Ubuntu 14.04

    That isn't good, hopefully Dell will have it fixed and back to you soon

  4. #14
    Join Date
    Dec 2007
    Beans
    78

    Re: Cannot change backlight brightness Ubuntu 14.04

    I hope so too. Thanks again for your help with troubleshooting the problem

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