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[Bug 1345499] [NEW] [Lenovo ThinkPad X220] kernel 3.13 i915 brightness settings broken when going from docked -> undocked

 

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The brightness control on the Lenovo ThinkPad x220 is no longer working
after undocking. It is stuck an the lowest level and can't by changed
with the hotkeys. There is /sys/class/backlight/acpi_video0/ which has
no effect. The bug occurs when using kernel 3.13 on 12.04 and on 14.04.

WORKAROUND: Set the brightness through /sys/class/backlight/intel_backlight/
The hotkeys are working again after setting the brightness once on the command line.

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: linux-image-3.13.0-30-generic 3.13.0-30.55~precise1
ProcVersionSignature: Ubuntu 3.13.0-30.55~precise1-generic 3.13.11.2
Uname: Linux 3.13.0-30-generic x86_64
ApportVersion: 2.0.1-0ubuntu17.6
Architecture: amd64
Date: Sun Jul 20 09:39:01 2014
InstallationMedia: Ubuntu 12.04 LTS "Precise Pangolin" - Release amd64 (20120425)
MarkForUpload: True
SourcePackage: linux-lts-trusty
UpgradeStatus: No upgrade log present (probably fresh install)

** Affects: linux (Ubuntu)
     Importance: Low
         Status: Incomplete


** Tags: amd64 apport-bug precise
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[Lenovo ThinkPad X220] kernel 3.13 i915 brightness settings broken when going from docked -> undocked
https://bugs.launchpad.net/bugs/1345499
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