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["Christopher M. Penalver" <christopher.m.penalver@xxxxxxxxx>]

** Tags removed: backlight kernel

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https://bugs.launchpad.net/bugs/1138168

Title:
  8086:0106 Backlight control regression

Status in The Linux Kernel:
  Incomplete
Status in “linux” package in Ubuntu:
  Triaged

Bug description:
  Laptop: ASUS A54C-NB91 with BIOS version 210 After the 3.6 kernel
  controlling the backlight via software (like xbacklight and the
  brightness applet) no longer works as intended (attempting to get
  brightness alters the brightness). This was not a Issue on the older
  BIOS version (207), but downgrading that is not possible, and ASUS
  will not fix it stating the typical we don't support linux on this
  model On the 3.6 kernel with the latest BIOS the backlight can't be
  controlled via the fn+brightness keys, that still works on the 3.7
  kernel and up i have never had the fn+brightness keys ever update
  /sys/class/backlight/acpi_video0/brightness under any tested scenario.

  I have tested Kernel versions 3.8.1-030801, 3.8.0-8, 3.7.10-030710, and 3.6.11-030611 today on raring without acpi_backlight=vendor. I had the exact same results as when i did the test earlier in raring and quantal (see PDF file in attachment). The attachment contains the following files (all system generated files are from this install)
  Detailed test.pdf
  dmesg_3.6.11-030611-generic
  dmesg_3.7.10-030710-generic
  dmesg_3.8.0-8-generic
  dmesg_3.8.1-030801-generic
  lspci_very_verbose
  syslog

  WORKAROUND: One may choose a value from 0 (completely off) to 4882 (100%) works in increments of 2:
  echo 100 | sudo tee /sys/class/backlight/intel_backlight/brightness

  ProblemType: Bug
  DistroRelease: Ubuntu 13.04
  Package: linux-image-3.8.0-8-generic 3.8.0-8.17
  ProcVersionSignature: Ubuntu 3.8.0-8.17-generic 3.8.0
  Uname: Linux 3.8.0-8-generic x86_64
  ApportVersion: 2.9-0ubuntu2
  Architecture: amd64
  AudioDevicesInUse:
   USER        PID ACCESS COMMAND
   /dev/snd/controlC0:  chad       1708 F.... xfce4-volumed
                        chad       1722 F.... pulseaudio
   /dev/snd/pcmC0D0p:   chad       1722 F...m pulseaudio
  CurrentDmesg:

  Date: Fri Mar  1 11:31:52 2013
  HibernationDevice: RESUME=UUID=a974f07b-dcae-4886-8ddb-e5a48219f891
  InstallationDate: Installed on 2013-03-01 (0 days ago)
  InstallationMedia: Xubuntu 13.04 "Raring Ringtail" - Alpha amd64 (20130301)
  MachineType: ASUSTeK Computer Inc. K54C
  MarkForUpload: True
  ProcFB: 0 inteldrmfb
  ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.8.0-8-generic root=UUID=5c6a915b-d2e5-4746-9c09-657e51145ad6 ro quiet splash vt.handoff=7
  RelatedPackageVersions:
   linux-restricted-modules-3.8.0-8-generic N/A
   linux-backports-modules-3.8.0-8-generic  N/A
   linux-firmware                           1.103
  SourcePackage: linux
  UpgradeStatus: No upgrade log present (probably fresh install)
  dmi.bios.date: 10/23/2012
  dmi.bios.vendor: American Megatrends Inc.
  dmi.bios.version: K54C.210
  dmi.board.asset.tag: ATN12345678901234567
  dmi.board.name: K54C
  dmi.board.vendor: ASUSTeK Computer Inc.
  dmi.board.version: 1.0
  dmi.chassis.asset.tag: ATN12345678901234567
  dmi.chassis.type: 10
  dmi.chassis.vendor: ASUSTeK Computer Inc.
  dmi.chassis.version: 1.0
  dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvrK54C.210:bd10/23/2012:svnASUSTeKComputerInc.:pnK54C:pvr1.0:rvnASUSTeKComputerInc.:rnK54C:rvr1.0:cvnASUSTeKComputerInc.:ct10:cvr1.0:
  dmi.product.name: K54C
  dmi.product.version: 1.0
  dmi.sys.vendor: ASUSTeK Computer Inc.

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