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[Tony Pursell <ajp@xxxxxxxxxxxxxxxxxxxxxxx>]

Backlight debugging as per link supplied by jpds.

Backlight control does not work, but there are entries in
/sys/class/backlight.

Debugging information collected and attached.

Testing for work around:

After reboot with only the kernel parameter acpi_backlight=vendor:

The function keys (hotkeys) have no effect (i.e do not change brightness
or cause the brightness indicator to appear) but the Brightness slider
in the Brightness & Lock settings dialogue does change the screen
brightness.

Command ls /sys/class/backlight > vendorbacklight was executed

There is a folder /sys/class/backlight/intel_backlight/

Command ls -la /sys/class/backlight/intel_backlight/ > lslabacklight was
executed

Command echo 8 > /sys/class/backlight/intel_backlight/brightness
executed causing the screen brightnes to change to very dim.


After reboot with only the kernel parameter video.use_bios_initial_backlight=0 :

The function keys (hotkeys) do not change brightness but they do cause
the brightness indicator to appear and move. The Brightness slider in
the Brightness & Lock settings dialogue *does* change the screen
brightness.


Kernel is 3.13.0-24-generic. After reboot with only the kernel parameter video.use_native_backlight=1 :

The function keys (hotkeys) do not change brightness but they do cause
the brightness indicator to appear and move. The Brightness slider in
the Brightness & Lock settings dialogue does not change the screen
brightness.


** Attachment added: "acpi"
   https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1311297/+attachment/4095598/+files/acpi

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https://bugs.launchpad.net/bugs/1311297

Title:
  Screen brightness cannot be adjusted on ASUS Eeepc 1015PEM

Status in “linux” package in Ubuntu:
  Incomplete

Bug description:
  This is a regression.  Up to 13.10 there was no problem changing
  screen brightness on my Asus Eeepc 1015PEM.  This machine has function
  keys for changing  the screen brightness up (with Fn+F6) and down
  (with Fn+F5).

  In 14.04 using the function keys causes the indicator to appear and
  the the brightness bar moves appropriately, but there is no change to
  screen brightness.

  Using the slider on the (new?) Brightness and Lock settings form also
  has no affect on the screen brightness.  Operation of the function
  keys will move the slider.  However, repeated use of the function keys
  causes the slider control to disappear from the form (as is found on a
  machine where control of screen brightness by function keys are not
  available).

  ProblemType: Bug
  DistroRelease: Ubuntu 14.04
  Package: linux-image-3.13.0-24-generic 3.13.0-24.46
  ProcVersionSignature: Ubuntu 3.13.0-24.46-generic 3.13.9
  Uname: Linux 3.13.0-24-generic i686
  NonfreeKernelModules: wl
  ApportVersion: 2.14.1-0ubuntu3
  Architecture: i386
  AudioDevicesInUse:
   USER        PID ACCESS COMMAND
   /dev/snd/controlC0:  tony       2031 F.... pulseaudio
  CurrentDesktop: Unity
  Date: Tue Apr 22 20:12:48 2014
  HibernationDevice: RESUME=UUID=fcc3dc2b-0a3b-4dcf-98d9-b1f03b2c812e
  InstallationDate: Installed on 2012-04-27 (724 days ago)
  InstallationMedia: Ubuntu 12.04 LTS "Precise Pangolin" - Release i386 (20120423)
  MachineType: ASUSTeK Computer INC. 1015PEM
  ProcFB: 0 inteldrmfb
  ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.13.0-24-generic root=UUID=abf837ae-032d-4686-8803-27a1376ee9c5 ro quiet splash vt.handoff=7
  RelatedPackageVersions:
   linux-restricted-modules-3.13.0-24-generic N/A
   linux-backports-modules-3.13.0-24-generic  N/A
   linux-firmware                             1.127
  SourcePackage: linux
  UpgradeStatus: Upgraded to trusty on 2014-04-20 (2 days ago)
  dmi.bios.date: 10/06/2010
  dmi.bios.vendor: American Megatrends Inc.
  dmi.bios.version: 0801
  dmi.board.asset.tag: To Be Filled By O.E.M.
  dmi.board.name: 1015PE
  dmi.board.vendor: ASUSTeK Computer INC.
  dmi.board.version: x.xx
  dmi.chassis.asset.tag: 0x00000000
  dmi.chassis.type: 10
  dmi.chassis.vendor: ASUSTeK Computer INC.
  dmi.chassis.version: x.x
  dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvr0801:bd10/06/2010:svnASUSTeKComputerINC.:pn1015PEM:pvrx.x:rvnASUSTeKComputerINC.:rn1015PE:rvrx.xx:cvnASUSTeKComputerINC.:ct10:cvrx.x:
  dmi.product.name: 1015PEM
  dmi.product.version: x.x
  dmi.sys.vendor: ASUSTeK Computer INC.

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