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[Guillaume Millet <gmillet@xxxxxxxxx>]

The bug existed on Maverick, as noticied on http://wiki.daviddarts.com/Ubuntu_Maverick_on_the_Asus_UL30VT#Screen_Brightness.
However, today, Precise is the last release still supported on Desktop. I have not tested any other release.

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https://bugs.launchpad.net/bugs/1178796

Title:
  8086:2a42 [Asus UL80VT] Backlight control does not work with Intel
  integrated card, but there are entries in /sys/class/backlight

Status in “linux” package in Ubuntu:
  Incomplete

Bug description:
  It used to work with the workaround suggested at
  http://wiki.daviddarts.com/Ubuntu_Maverick_on_the_Asus_UL30VT#Screen_Brightness
  which modifies asus-brn-down.sh to use the "setpci" method.

  But I had forgotten that workaround and I suspect that upgrading to
  Raring removed my modified scripts. So, in the original description of
  the bug, I thought it was a regression. But it's probably not a
  regression as the brightness control has apparently never worked off-
  the-shelf.

  Not working neither with linux-
  image-3.9.1-030901-generic_3.9.1-030901.201305080210 from
  http://kernel.ubuntu.com/~kernel-ppa/mainline/v3.9.1-saucy/

  Hotkeys are detected, showkey -s:
  Fn+F5:
  0xe0 0x4c 0xe0 0xcc
  Fn+F6:
  0xe0 0x54 0xe0 0xd4

  I also attach the results from tests described on
  https://wiki.ubuntu.com/Kernel/Debugging/Backlight.

  Test with acpi_backlight=vendor:
  - on 3.8.0-20.31-generic, no change. But echo 8 > /sys/class/backlight/intel_backlight/brightness makes the screen dark, moreover /sys/class/backlight/intel_backlight/max_brightness = 2583660
  - on 3.9.1, no brightness change but the KDE notification pops up with only 3 levels (0, 53, 100%)

  Test with video.use_bios_initial_backlight=0:
  - on 3.8.0-20.31-generic, no change.

  WORKAROUND: On KDE Raring Ubuntu 3.8.0-30.44-generic, bumblebee removed, BIOS SATA mode set to Compatible (this disables the Intel graphics card which does not appear anymore in lspci, http://wiki.daviddarts.com/Ubuntu_Maverick_on_the_Asus_UL30VT#Nvidia_Accelerated_Graphics_Driver), only default kernel parameters, and using either nouveau or nvidia drivers:
  The plasma widget for screen brightness (inside battery monitor widget) is able to change the brightness. And automatic brightness change from KDE system (when the power adaptor is unplugged) works also. In Raring, the hotkeys do not trigger any change (see bug #1225067) but this is fixed in Saucy.

  ProblemType: Bug
  DistroRelease: Ubuntu 13.04
  Package: linux-image-3.8.0-20-generic 3.8.0-20.31
  ProcVersionSignature: Ubuntu 3.8.0-20.31-generic 3.8.11
  Uname: Linux 3.8.0-20-generic x86_64
  ApportVersion: 2.9.2-0ubuntu8
  Architecture: amd64
  AudioDevicesInUse:
   USER        PID ACCESS COMMAND
   /dev/snd/controlC1:  guillaume   2490 F.... pulseaudio
   /dev/snd/controlC0:  guillaume   2490 F.... pulseaudio
  Date: Fri May 10 12:14:58 2013
  HibernationDevice: RESUME=/dev/sda6
  InstallationDate: Installed on 2010-01-19 (1207 days ago)
  InstallationMedia: Kubuntu 9.10 "Karmic Koala" - Release amd64 (20091027)
  MachineType: ASUSTeK Computer Inc. UL80VT
  MarkForUpload: True
  ProcFB: 0 inteldrmfb
  ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.8.0-20-generic root=UUID=d92f3a31-9e9c-4c19-98be-6fbc82629a36 ro video.use_bios_initial_backlight=0 quiet splash vt.handoff=7
  RelatedPackageVersions:
   linux-restricted-modules-3.8.0-20-generic N/A
   linux-backports-modules-3.8.0-20-generic  N/A
   linux-firmware                            1.106
  SourcePackage: linux
  UpgradeStatus: Upgraded to raring on 2013-04-27 (12 days ago)
  dmi.bios.date: 01/17/2011
  dmi.bios.vendor: American Megatrends Inc.
  dmi.bios.version: 214
  dmi.board.asset.tag: ATN12345678901234567
  dmi.board.name: UL80VT
  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.:bvr214:bd01/17/2011:svnASUSTeKComputerInc.:pnUL80VT:pvr1.0:rvnASUSTeKComputerInc.:rnUL80VT:rvr1.0:cvnASUSTeKComputerInc.:ct10:cvr1.0:
  dmi.product.name: UL80VT
  dmi.product.version: 1.0
  dmi.sys.vendor: ASUSTeK Computer Inc.
  ---
  ApportVersion: 2.12-0ubuntu3
  Architecture: amd64
  AudioDevicesInUse:
   USER        PID ACCESS COMMAND
   /dev/snd/controlC1:  ubuntu     2788 F.... pulseaudio
   /dev/snd/controlC0:  ubuntu     2788 F.... pulseaudio
  CasperVersion: 1.336
  DistroRelease: Ubuntu 13.10
  LiveMediaBuild: Ubuntu 13.10 "Saucy Salamander" - Alpha amd64 (20130813)
  MachineType: ASUSTeK Computer Inc. UL80VT
  MarkForUpload: True
  Package: linux (not installed)
  ProcFB: 0 inteldrmfb
  ProcKernelCmdLine: noprompt cdrom-detect/try-usb=true file=/cdrom/preseed/username.seed boot=casper initrd=/casper/initrd.lz quiet splash acpi_backlight=vendor --
  ProcVersionSignature: Ubuntu 3.11.0-1.4-generic 3.11.0-rc4
  RelatedPackageVersions:
   linux-restricted-modules-3.11.0-1-generic N/A
   linux-backports-modules-3.11.0-1-generic  N/A
   linux-firmware                            1.113
  Tags:  saucy
  Uname: Linux 3.11.0-1-generic x86_64
  UpgradeStatus: No upgrade log present (probably fresh install)
  UserGroups: adm cdrom dip lpadmin plugdev sambashare sudo
  dmi.bios.date: 01/17/2011
  dmi.bios.vendor: American Megatrends Inc.
  dmi.bios.version: 214
  dmi.board.asset.tag: ATN12345678901234567
  dmi.board.name: UL80VT
  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.:bvr214:bd01/17/2011:svnASUSTeKComputerInc.:pnUL80VT:pvr1.0:rvnASUSTeKComputerInc.:rnUL80VT:rvr1.0:cvnASUSTeKComputerInc.:ct10:cvr1.0:
  dmi.product.name: UL80VT
  dmi.product.version: 1.0
  dmi.sys.vendor: ASUSTeK Computer Inc.

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