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[Bug 1363623]


Hi, it took me quite some time to get here, but hopefully you can still solve my problem.
I'm running a 2006 Intel iMac (Core Duo) under Unbuntu 12.04LTS server, which sits on my desk and almost never log to the console, which would normally go blank a few minutes after boot.

There is strong evidence that this patch found its way to my "stock" kernel back in september 2014, and since then my iMac exhibits the following behaviour after boot:
- whenever the console blanking activates, backlight goes to MAX (with my LCD screen going all strange and overheating — even causing fans to blow)
- only way out is to echo 0 > /sys/class/backlight/radeon_bl0/brightness — which I 'crontabbed' but is not exactly satisfactory.
- any other value causes the backlight to go all the way up and overheat.

I did try to "echo 1 > /sys/class/backlight/acpi_video0/brightness"
today, and that caused the iMac to reboot.

I have not experimented anything else, but would be happy to help.

uname is "Linux xxx 3.13.0-49-generic #81~precise1-Ubuntu SMP Wed Mar 25
16:32:40 UTC 2015 i686 i686 i386 GNU/Linux"

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  [ASUS-A7K laptop] screen brightness dimmed after kernel update

Status in xserver-xorg-driver-radeonhd:
Status in linux package in Ubuntu:

Bug description:

  Following the update from kernel version 3.13.0-34 to 3.13.0-35-generic the screen brightness got a lot dimmer.
  The Fn+F5/F6 control keys still work, in that the display gets dimmer and brighter, but the maximum brightness is too low.
  When starting ubuntu using the previous kernel release the display brightness is alright.
  I've looked around the web for ways to change the display brightness and I checked that both files "/sys/class/backlight/acpi_video0/brightness" and "/sys/class/backlight/radeon_bl0/brightness" have the maximum values, 15 and 255 respectively.

  The release I am running is : Ubuntu 14.04.1 LTS
  The XORG package version is : 1:7.7+1ubuntu8

  Please feel free to contact me for any further information.

  ProblemType: Bug
  DistroRelease: Ubuntu 14.04
  Package: xorg 1:7.7+1ubuntu8
  ProcVersionSignature: Ubuntu 3.13.0-35.62-generic
  Uname: Linux 3.13.0-35-generic x86_64
  ApportVersion: 2.14.1-0ubuntu3.3
  Architecture: amd64
  CompizPlugins: No value set for `/apps/compiz-1/general/screen0/options/active_plugins'
  CompositorRunning: None
  CurrentDesktop: GNOME
  Date: Sun Aug 31 11:40:07 2014
  DistUpgraded: Fresh install
  DistroCodename: trusty
  DistroVariant: ubuntu
  ExtraDebuggingInterest: Yes, if not too technical
   Advanced Micro Devices, Inc. [AMD/ATI] RV630/M76 [Mobility Radeon HD 2600] [1002:9581] (prog-if 00 [VGA controller])
     Subsystem: ASUSTeK Computer Inc. Device [1043:1562]
  InstallationDate: Installed on 2014-07-24 (38 days ago)
  InstallationMedia: Ubuntu 14.04 LTS "Trusty Tahr" - Release amd64 (20140417)
  MachineType: ASUSTeK Computer Inc. A7K
   PATH=(custom, no user)
  ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-3.13.0-35-generic root=/dev/mapper/vg_a7k-lv_root ro quiet splash vt.handoff=7
  SourcePackage: xorg
  Symptom: display
  UpgradeStatus: No upgrade log present (probably fresh install)
  dmi.bios.date: 07/25/2007
  dmi.bios.vendor: American Megatrends Inc.
  dmi.bios.version: A7KAS.2
  dmi.board.asset.tag: ATN12345678901234567
  dmi.board.name: A7K
  dmi.board.vendor: ASUSTeK Computer Inc.
  dmi.board.version: 1.0
  dmi.chassis.type: 10
  dmi.chassis.vendor: ASUSTeK Computer Inc.
  dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvrA7KAS.2:bd07/25/2007:svnASUSTeKComputerInc.:pnA7K:pvr1.0:rvnASUSTeKComputerInc.:rnA7K:rvr1.0:cvnASUSTeKComputerInc.:ct10:cvr:
  dmi.product.name: A7K
  dmi.product.version: 1.0
  dmi.sys.vendor: ASUSTeK Computer Inc.
  version.compiz: compiz 1:
  version.ia32-libs: ia32-libs N/A
  version.libdrm2: libdrm2 2.4.52-1
  version.libgl1-mesa-dri: libgl1-mesa-dri 10.1.3-0ubuntu0.1
  version.libgl1-mesa-dri-experimental: libgl1-mesa-dri-experimental N/A
  version.libgl1-mesa-glx: libgl1-mesa-glx 10.1.3-0ubuntu0.1
  version.xserver-xorg-core: xserver-xorg-core 2:1.15.1-0ubuntu2
  version.xserver-xorg-input-evdev: xserver-xorg-input-evdev 1:2.8.2-1ubuntu2
  version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:7.3.0-1ubuntu3.1
  version.xserver-xorg-video-intel: xserver-xorg-video-intel 2:2.99.910-0ubuntu1
  version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:1.0.10-1ubuntu2
  xserver.bootTime: Sun Aug 31 11:06:06 2014
  xserver.configfile: default
  xserver.logfile: /var/log/Xorg.0.log
  xserver.version: 2:1.15.1-0ubuntu2
  xserver.video_driver: radeon

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