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Message #17774
[Bug 1098216] Re: Regression in brightness control on Lenovo Thinkpad X230 (+tablet) and X1 Carbon
Using above fixes stepping in ubuntu. The fix is still working under
ubuntu Swapping Ctrl and Fn keys in bios works
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https://bugs.launchpad.net/bugs/1098216
Title:
Regression in brightness control on Lenovo Thinkpad X230 (+tablet) and
X1 Carbon
Status in The Linux Kernel:
In Progress
Status in “linux” package in Ubuntu:
Triaged
Status in “linux” package in Fedora:
Unknown
Bug description:
== Raring SRU Justification ==
Impact: A number of ThinkPad models have a workaround in the ACPI
backlight implementation for Windows 8 that more or less completely
breaks backlight control.
Fix: Add an OSI quirk to no longer claim to be Windows 8 on these
machines, causing the firmware to revert to the older, working behavior.
Test Case: Verified on LP #1098216 and bugzill.kernel.org #51231.
---
Something changed between the 3.5 and the 3.7 kernel, leading to
broken brightness control on my Thinkpad x230.
Here are some test results:
== 3.5.0-21-generic ==
=== Post-boot values ===
/sys/class/backlight:
- intel-backlight
+ actual_brightness => 4438
+ bl_power => 0
+ brightness => 4438
+ max_brightness => 4438
- acpi_video0
+ actual_brightness => 15
+ bl_power => 0
+ brightness => 15
+ max_brightness => 15
=== Tests ===
echo 0 > acpi_video0/brightness => works
echo 0 > intel_backlight/brightness => works
== 3.8.0-0-generic ==
=== Post-boot values ===
/sys/class/backlight:
- intel-backlight
+ actual_brightness => 4438
+ bl_power => 0
+ brightness => 4438
+ max_brightness => 4438
- acpi_video0
+ actual_brightness => 100
+ bl_power => 0
+ brightness => 100
+ max_brightness => 100
=== Tests ===
echo 0 > acpi_video0/brightness => doesn't do anything
echo 0 > intel_backlight/brightness => works
---
ApportVersion: 2.8-0ubuntu1
Architecture: amd64
CheckboxSubmission: 12108b8b8b67d760cdd84f1b9574e7f3
CheckboxSystem: bb422ca46d02494cdbc459927a98bc2f
DistroRelease: Ubuntu 13.04
InstallationDate: Installed on 2012-09-02 (129 days ago)
InstallationMedia: Ubuntu 12.10 "Quantal Quetzal" - Alpha amd64 (20120902)
MarkForUpload: True
Package: linux (not installed)
ProcEnviron:
LANGUAGE=en_US:en
TERM=xterm
PATH=(custom, no user)
LANG=en_US.UTF-8
SHELL=/bin/bash
ProcVersionSignature: Ubuntu 3.8.0-0.1-generic 3.8.0-rc3
Tags: raring
Uname: Linux 3.8.0-0-generic x86_64
UnreportableReason: The running kernel is not an Ubuntu kernel
UpgradeStatus: No upgrade log present (probably fresh install)
UserGroups:
WORKAROUND:
Add to /etc/default/grub
in the variable "GRUB_CMDLINE_LINUX_DEFAULT":
acpi_osi=\"!Windows 2012\"
e.g:
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_osi=\"!Windows 2012\""
Then run "sudo update-grub".
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