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Message #01239
[Bug 1400155] Re: inconsistent backlight brightness behaviour
David Chatterton, Please execute the following command, as it will automatically gather debugging information, in a terminal:
apport-collect 1400155
When reporting bugs in the future please use apport by using 'ubuntu-bug' and the name of the package affected. You can learn more about this functionality at https://wiki.ubuntu.com/ReportingBugs.
** Package changed: ubuntu-docs (Ubuntu) => linux (Ubuntu)
** Changed in: linux (Ubuntu)
Importance: Undecided => Low
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https://bugs.launchpad.net/bugs/1400155
Title:
inconsistent backlight brightness behaviour
Status in linux package in Ubuntu:
Incomplete
Bug description:
This bug refers to a Dell XPS13-9333 running Ubuntu 14.10.
I discovered a workaround to prevent the screen starting with full
brightness.
The reference to the workaround advice is:
http://ubuntuhandbook.org/index.php/2014/04/save-screen-brightness-settings-in-ubuntu-14-04/
There is a folder sys/class/backlight/intel_backlight/ containing a
number of files such as brightness, actual_brightness and
max_brightness. When using Fn-F4 & F5 to control the screen backlight,
the two files: brightness and actual_brightness respond by changing
there contents to a number which is a proportion of the contents of
max_brightness (937).
The workaround was to include the line:
echo 569 > /sys/class/backlight/intel_backlight/brightness
at the end of the file: /etc/rc.local using gedit (where 569 is a
value noted for a typically comfortable level of backlight).
This works when doing a restart but, when logging back in after
logging out, the backlight comes on at maximum brightness.
This particular laptop has a front-facing webcam fitted. Its function
can be confirmed by running the Cheese webcam Booth. It would be a
vast improvement if the ambient brightness could be sensed by the
webcam and used to adjust the backlight brightness. Auto brightness
could be selected or not by a tick box in the Brightness & Lock
section of System Settings. Similarly, a tick box might also be
provided to enable saving of the backlight brightness when shutting
down or logging off
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References