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[Florent Flament <contact@xxxxxxxxxxxxxxxxxx>]

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https://bugs.launchpad.net/bugs/1335458

Title:
  Backlight control does not work, but there are entries in
  /sys/class/backlight - Toshiba Satellite Z930-164

Status in “linux” package in Ubuntu:
  Confirmed

Bug description:
  Following bug reporting process:
  https://wiki.ubuntu.com/Kernel/Debugging/Backlight#Reporting_Backlight_Bugs

  Running Ubuntu 14.04 with Unity.

  
  Testing for a work around:

  * With kernel parameter acpi_backlight=vendor
    -> Brightness control is working with both applet and hotkeys.

    - # echo 8 > /sys/class/backlight/intel_backlight/brightness
      -> The command sets the screens brightness very low (almost turns
         it off).

  * With kernel parameter video.use_bios_initial_backlight=0
    -> Brightness control is neither working with applet nor hotkeys.

  * With kernel parameter video.use_native_backlight=1
    -> Brightness control is working with both applet and hotkeys.

  ProblemType: Bug
  DistroRelease: Ubuntu 14.04
  Package: linux-image-3.13.0-30-generic 3.13.0-30.54
  ProcVersionSignature: Ubuntu 3.13.0-30.54-generic 3.13.11.2
  Uname: Linux 3.13.0-30-generic x86_64
  ApportVersion: 2.14.1-0ubuntu3.2
  Architecture: amd64
  AudioDevicesInUse:
   USER        PID ACCESS COMMAND
   /dev/snd/controlC0:  florent    2107 F.... pulseaudio
  CurrentDesktop: Unity
  Date: Sat Jun 28 18:17:42 2014
  EcryptfsInUse: Yes
  HibernationDevice: RESUME=/dev/mapper/toshnux--vg-swap_1
  MachineType: TOSHIBA SATELLITE Z930
  ProcFB: 0 inteldrmfb
  ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.13.0-30-generic root=/dev/mapper/hostname--vg-root ro splash quiet acpi_backlight=vendor vt.handoff=7
  RelatedPackageVersions:
   linux-restricted-modules-3.13.0-30-generic N/A
   linux-backports-modules-3.13.0-30-generic  N/A
   linux-firmware                             1.127.4
  SourcePackage: linux
  UpgradeStatus: No upgrade log present (probably fresh install)
  dmi.bios.date: 04/04/2013
  dmi.bios.vendor: TOSHIBA
  dmi.bios.version: Version 6.70
  dmi.board.asset.tag: 0000000000
  dmi.board.name: SATELLITE Z930
  dmi.board.vendor: TOSHIBA
  dmi.board.version: Version A0
  dmi.chassis.asset.tag: 0000000000
  dmi.chassis.type: 10
  dmi.chassis.vendor: TOSHIBA
  dmi.chassis.version: Version 1.0
  dmi.modalias: dmi:bvnTOSHIBA:bvrVersion6.70:bd04/04/2013:svnTOSHIBA:pnSATELLITEZ930:pvrPT23LE-01900EFR:rvnTOSHIBA:rnSATELLITEZ930:rvrVersionA0:cvnTOSHIBA:ct10:cvrVersion1.0:
  dmi.product.name: SATELLITE Z930
  dmi.product.version: PT23LE-01900EFR
  dmi.sys.vendor: TOSHIBA

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