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[Bug 1270079] Re: [Lenovo T540p, W540] Backlight interfaces not fully working


** Changed in: linux-lts-saucy (Ubuntu)
       Status: Confirmed => Fix Released

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  [Lenovo T540p, W540] Backlight interfaces not fully working

Status in linux-lts-raring package in Ubuntu:
  Fix Released
Status in linux-lts-saucy package in Ubuntu:
  Fix Released

Bug description:
  This is a system installed with 12.04.3.

  Brightness can be controlled in "Systems Settings" > "Brightness and
  Lock" > Brightness slider.

  However there are three interfaces,

  /sys/class/backlight$ ls
  acpi_video0  acpi_video1  intel_backlight

  By controlling each interfaces as following command:
  $ sudo sh -c 'echo 80 > brightness'

  here is the findings:

  acpi_video*/brighness can be only controll by particular values like,
  80, 40, 22, 12, 8, 5 ,3,1

  intel_backlight/brightness can adjust from 0 to 4789.

  three interfaces are not synchronized, this cause an issue for other
  tools that uses acpi_video0 or acpi_video1 on this system.

  ProblemType: Bug
  DistroRelease: Ubuntu 12.04
  Package: linux-image-3.8.0-35-generic 3.8.0-35.50~precise1
  ProcVersionSignature: Ubuntu 3.8.0-35.50~precise1-generic
  Uname: Linux 3.8.0-35-generic x86_64
  AlsaVersion: Advanced Linux Sound Architecture Driver Version k3.8.0-35-generic.
  ApportVersion: 2.0.1-0ubuntu17.6
  Architecture: amd64
   **** List of CAPTURE Hardware Devices ****
   card 1: PCH [HDA Intel PCH], device 0: ALC292 Analog [ALC292 Analog]
     Subdevices: 1/1
     Subdevice #0: subdevice #0
   /dev/snd/controlC1:  ubuntu     1751 F.... pulseaudio
   /dev/snd/controlC0:  ubuntu     1751 F.... pulseaudio
  CRDA: Error: [Errno 2] No such file or directory
   Card hw:0 'MID'/'HDA Intel MID at 0xf2630000 irq 48'
     Mixer name	: 'Intel Haswell HDMI'
     Components	: 'HDA:80862807,80860101,00100000'
     Controls      : 21
     Simple ctrls  : 3
   Card hw:1 'PCH'/'HDA Intel PCH at 0xf2634000 irq 49'
     Mixer name	: 'Realtek ALC292'
     Components	: 'HDA:10ec0292,17aa2210,00100001'
     Controls      : 22
     Simple ctrls  : 10
   Card hw:29 'ThinkPadEC'/'ThinkPad Console Audio Control at EC reg 0x30, fw unknown'
     Mixer name	: 'ThinkPad EC (unknown)'
     Components	: ''
     Controls      : 1
     Simple ctrls  : 1
   Simple mixer control 'Console',0
     Capabilities: pswitch pswitch-joined penum
     Playback channels: Mono
     Mono: Playback [on]
  CurrentDmesg: [   40.050791] type=1400 audit(1389947716.229:28): apparmor="DENIED" operation="open" parent=1 profile="/usr/lib/telepathy/mission-control-5" name="/usr/share/gvfs/remote-volume-monitors/" pid=1974 comm="mission-control" requested_mask="r" denied_mask="r" fsuid=1000 ouid=0
  Date: Fri Jan 17 03:40:35 2014
  HibernationDevice: RESUME=UUID=619bafb8-b790-472c-9471-181ae33c4dd2
  InstallationMedia: Ubuntu 12.04.3 LTS "Precise Pangolin" - Release amd64 (20130820.1)
   eth0      no wireless extensions.
   lo        no wireless extensions.
  MachineType: LENOVO 20BFZ052US
  MarkForUpload: True
   PATH=(custom, no user)
  ProcFB: 0 inteldrmfb
  ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.8.0-35-generic root=UUID=4fde570e-2674-44ba-8c05-5626a382ef7b ro quiet splash thinkpad-acpi brightness_enable=1 initcall_debug vt.handoff=7
   linux-restricted-modules-3.8.0-35-generic N/A
   linux-backports-modules-3.8.0-35-generic  N/A
   linux-firmware                            1.79.6
  SourcePackage: linux-lts-raring
  UpgradeStatus: No upgrade log present (probably fresh install)
  dmi.bios.date: 08/09/2013
  dmi.bios.vendor: LENOVO
  dmi.bios.version: GMET21WW (1.01 )
  dmi.board.asset.tag: Not Available
  dmi.board.name: 20BFZ052US
  dmi.board.vendor: LENOVO
  dmi.board.version: Win8 Pro DPK TPG
  dmi.chassis.asset.tag: No Asset Information
  dmi.chassis.type: 10
  dmi.chassis.vendor: LENOVO
  dmi.chassis.version: Not Available
  dmi.modalias: dmi:bvnLENOVO:bvrGMET21WW(1.01):bd08/09/2013:svnLENOVO:pn20BFZ052US:pvrThinkPadT540p:rvnLENOVO:rn20BFZ052US:rvrWin8ProDPKTPG:cvnLENOVO:ct10:cvrNotAvailable:
  dmi.product.name: 20BFZ052US
  dmi.product.version: ThinkPad T540p
  dmi.sys.vendor: LENOVO

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