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[Bug 1400155] Re: inconsistent backlight brightness behaviour


[Expired for linux (Ubuntu) because there has been no activity for 60

** Changed in: linux (Ubuntu)
       Status: Incomplete => Expired

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  inconsistent backlight brightness behaviour

Status in linux package in Ubuntu:

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

  The reference to the workaround advice is:

  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
  ApportVersion: 2.14.7-0ubuntu8
  Architecture: amd64
   /dev/snd/controlC0:  david      2755 F.... pulseaudio
   /dev/snd/controlC1:  david      2755 F.... pulseaudio
  CurrentDesktop: Unity
   # This is a distribution channel descriptor
   # For more information see http://wiki.ubuntu.com/DistributionChannelDescriptor
  DistroRelease: Ubuntu 14.10
  HibernationDevice: RESUME=UUID=2ce4d026-79c8-46d8-aa78-9a01276f4ada
  InstallationDate: Installed on 2014-11-08 (29 days ago)
  InstallationMedia: Ubuntu 12.04 "Precise" - Build amd64 LIVE Binary 20130203-13:50
  MachineType: Dell Inc. XPS13 9333
  Package: linux (not installed)
  ProcFB: 0 inteldrmfb
  ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.16.0-25-generic root=UUID=10c98fc6-0c96-44d3-9e0e-ba93d84dffe6 ro quiet splash vt.handoff=7
  ProcVersionSignature: Ubuntu 3.16.0-25.33-generic 3.16.7
   linux-restricted-modules-3.16.0-25-generic N/A
   linux-backports-modules-3.16.0-25-generic  N/A
   linux-firmware                             1.138
  Tags:  utopic
  Uname: Linux 3.16.0-25-generic x86_64
  UpgradeStatus: Upgraded to utopic on 2014-11-21 (16 days ago)
  UserGroups: adm cdrom dialout dip libvirtd lpadmin plugdev sambashare sudo
  _MarkForUpload: True
  dmi.bios.date: 09/11/2014
  dmi.bios.vendor: Dell Inc.
  dmi.bios.version: A05
  dmi.board.name: 0D13CR
  dmi.board.vendor: Dell Inc.
  dmi.board.version: A00
  dmi.chassis.type: 8
  dmi.chassis.vendor: Dell Inc.
  dmi.chassis.version: 0.1
  dmi.modalias: dmi:bvnDellInc.:bvrA05:bd09/11/2014:svnDellInc.:pnXPS139333:pvr:rvnDellInc.:rn0D13CR:rvrA00:cvnDellInc.:ct8:cvr0.1:
  dmi.product.name: XPS13 9333
  dmi.sys.vendor: Dell Inc.

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