GNOME Bugzilla – Bug 720370
usability - gsd-backlight-helper fails to change backlight / screen brightness
Last modified: 2013-12-13 12:38:41 UTC
In Saucy Salamander (Ubuntu 13.10), nothing happens when programmatically changing the backlight using the command: pkexec /usr/lib/gnome-settings-daemon/gsd-backlight-helper --set-brightness 50 After issuing the above-mentioned command: 1. There is no difference in the screen brightness. 2. The slider in the "System Settings" -> "Brightness & Lock" remains unchanged. However, the value specified with --set-brightness argument is correctly reflected in the file: /sys/class/backlight/acpi_video0/actual_brightness and /sys/class/backlight/acpi_video0/actual_brightness Additionally, I'm using the proprietary Video driver for the AMD graphics accelerators from fglrx-updates. (I can't use the X.org X Server open source driver, because I get a lot of visual artefacts / screen refresh problems when I use it). Furthermore, manually adjusting the brightness directly from the GUI, using the slider in "System Settings" -> "Brightness & Lock" works correctly, changing the screen brightness, as is expected. This manual change in screen brightness is also reflected in the above-mentioned files, which can be confirmed by issuing the following commands: pkexec /usr/lib/gnome-settings-daemon/gsd-backlight-helper --get-brightness and cat /sys/class/backlight/acpi_video0/actual_brightness and cat /sys/class/backlight/acpi_video0/actual_brightness Also, note that this worked previously on the very same machine when Ubuntu 13.04 was the Operating system, without a problem. This issue has only surfaced after upgrading the operating system to Ubuntu 13.10. Also, I did a clean update of the Operating System upgrade - namely, I cleaned off all the old stuff and then started with the fresh install of Ubuntu 13.10 from the beginning with the re-formatting of disk, etc. Ubuntu Release: -------------------------- Description: Ubuntu 13.10 Release: 13.10 Machine Type: Desktop Computer (All-in-one Desktop) Architecture: 64 bit. Package version: ----------------------------- gnome-settings-daemon: Installed: 3.8.5-0ubuntu11.1 Candidate: 3.8.5-0ubuntu11.1 Version table: *** 3.8.5-0ubuntu11.1 0 500 http://us.archive.ubuntu.com/ubuntu/ saucy-updates/main amd64 Packages 100 /var/lib/dpkg/status 3.8.5-0ubuntu9 0 500 http://us.archive.ubuntu.com/ubuntu/ saucy/main amd64 Packages Expected Behavior: ------------------------------- After issuing the command pkexec /usr/lib/gnome-settings-daemon/gsd-backlight-helper --set-brightness XX, the following should happen: 1. The screen brightness should increase or decrease as per the XX value specified. 2. The slider in the "System Settings" -> "Brightness & Lock" should change to reflect the new value. What Happens Instead: ----------------------------------- 1. There is no difference in the screen brightness. 2. The slider in the "System Settings" -> "Brightness & Lock" remains unchanged. Link to Launchpad bug: ----------------------- https://bugs.launchpad.net/ubuntu/+source/gnome-settings-daemon/+bug/1252507
(In reply to comment #0) > In Saucy Salamander (Ubuntu 13.10), nothing happens when programmatically > changing the backlight using the command: > pkexec /usr/lib/gnome-settings-daemon/gsd-backlight-helper --set-brightness 50 <snip> > Furthermore, manually adjusting the brightness directly from the GUI, using the > slider in "System Settings" -> "Brightness & Lock" works correctly, changing > the screen brightness, as is expected. The pkexec helper doesn't work but the brightness slider works. That means that gnome-settings-daemon works, and that it's using XRandR and not the pkexec helper to change the brightness. You can double-check that with: xrandr -q --verbose | grep -i backlight Furthermore, the pkexec helper isn't public API. The public API is through D-Bus.