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[Bug 1388817] Re: Backlight brightness problem with Thinkpad T440S


I don't know which tag I should add since not all of my problems are
fixed by v3.18-rc3-vivid.

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  Backlight brightness problem with Thinkpad T440S

Status in “linux” package in Ubuntu:

Bug description:
  The brightness can't be adjusted smoothly. Only 4 brightnesses can be
  achieved with Fn keys.

  WORKAROUND: I add "acpi_backlight=vendor" kernel parameter according
  to https://wiki.ubuntu.com/Kernel/Debugging/Backlight.

  ProblemType: Bug
  DistroRelease: Ubuntu 14.04
  Package: linux-image-3.13.0-39-generic 3.13.0-39.66
  ProcVersionSignature: Ubuntu 3.13.0-39.66-generic
  Uname: Linux 3.13.0-39-generic x86_64
  ApportVersion: 2.14.1-0ubuntu3.5
  Architecture: amd64
   /dev/snd/controlC0:  jing       2280 F.... pulseaudio
   /dev/snd/controlC1:  jing       2280 F.... pulseaudio
   /dev/snd/pcmC1D0p:   jing       2280 F...m pulseaudio
  CurrentDesktop: Unity
  Date: Mon Nov  3 20:51:08 2014
  HibernationDevice: RESUME=UUID=4bfed795-9c38-418e-b097-83b17523308e
  InstallationDate: Installed on 2014-06-28 (128 days ago)
  InstallationMedia: Ubuntu 14.04 LTS "Trusty Tahr" - Release amd64 (20140417)
  MachineType: LENOVO 20AQA02QHH
  ProcFB: 0 inteldrmfb
  ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-3.13.0-39-generic root=/dev/mapper/ubuntu--vg-root ro quiet splash acpi_backlight=vendor vt.handoff=7
   linux-restricted-modules-3.13.0-39-generic N/A
   linux-backports-modules-3.13.0-39-generic  N/A
   linux-firmware                             1.127.7
  SourcePackage: linux
  UpgradeStatus: No upgrade log present (probably fresh install)
  dmi.bios.date: 02/21/2014
  dmi.bios.vendor: LENOVO
  dmi.bios.version: GJET72WW (2.22 )
  dmi.board.asset.tag: Not Available
  dmi.board.name: 20AQA02QHH
  dmi.board.vendor: LENOVO
  dmi.board.version: 0B98405 STD
  dmi.chassis.asset.tag: No Asset Information
  dmi.chassis.type: 10
  dmi.chassis.vendor: LENOVO
  dmi.chassis.version: Not Available
  dmi.modalias: dmi:bvnLENOVO:bvrGJET72WW(2.22):bd02/21/2014:svnLENOVO:pn20AQA02QHH:pvrThinkPadT440s:rvnLENOVO:rn20AQA02QHH:rvr0B98405STD:cvnLENOVO:ct10:cvrNotAvailable:
  dmi.product.name: 20AQA02QHH
  dmi.product.version: ThinkPad T440s
  dmi.sys.vendor: LENOVO

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