https://bugzilla.kernel.org/show_bug.cgi?id=81691
Bug ID: 81691
Summary: Regression: Thinkpad T420 brightness keys broken by
commit 751109aad, video.use_native_backlight=1
Product: ACPI
Version: 2.5
Kernel Version: 3.16 (since commit 751109aad)
Hardware: x86-64
OS: Linux
Tree: Mainline
Status: NEW
Severity: normal
Priority: P1
Component: Power-Video
Assignee: [email protected]
Reporter: [email protected]
Regression: No
Created attachment 145151
--> https://bugzilla.kernel.org/attachment.cgi?id=145151&action=edit
output of dmidecode, xz compressed
In linux-3.16, this commit
> commit 751109aad5834375ca9ed0dcfcd85a00cbf872b5
> Author: Rafael J. Wysocki <[email protected]>
> Date: Thu Jun 5 22:47:35 2014 +0200
>
> ACPI / video: Change the default for video.use_native_backlight to 1
breaks backlight control on the Lenovo Thinkpad T420.
That is, I can't change brightness via the Fn-Keys anymore.
Writing to
/sys/devices/pci0000:00/0000:00:02.0/drm/card0/card0-LVDS-1/intel_backlight/brightness
works, but the kernel should just handle it by itself.
Providing video.use_native_backlight=0 on the kernel command line
fixes the controls.
So this would need to get a quirk or a fix for native backlight.
I do attach the dmidecode output.
I'll happily provide more information, or test things.
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