Re: 2.6.38-rc2: acpi backlight control missing

From: Rafael J. Wysocki
Date: Mon Jan 31 2011 - 15:39:33 EST


On Friday, January 28, 2011, Thomas Meyer wrote:
> Am Samstag, den 22.01.2011, 20:43 +0100 schrieb Rafael J. Wysocki:
> > On Saturday, January 22, 2011, Thomas Meyer wrote:
> > > with 2.6.38-rc2 the acpi backlight is gone:
> > >
> > > any ideas?
> >
> > Not really, but Matthew may have some (CCed).
>
> Okay, found the problem.
>
> This commit broke my backlight:
>
> commit 677bd810eedce61edf15452491781ff046b92edc
> Author: Zhang Rui <rui.zhang@xxxxxxxxx>
> Date: Mon Dec 6 15:04:21 2010 +0800
>
> ACPI video: remove output switching control
>
> This is because in function
> "acpi_is_video_device()" (drivers/acpi/video_detect.c) the backlight
> device is only checked when some video capabilities were found, but by
> removing the check for the VIDEO_OUTPUT_SWITCHING (that seems to be the
> only video capability on my system) the check for the backlight device
> isn't done anymore.
>
> by reverting above commit, the backlight is back again.

Is it the same issue as https://bugzilla.kernel.org/show_bug.cgi?id=27702 ?
In case it is, can you test the patch in there, please?

Rafael
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