Re: [Regression]: Changing brightness does not work with v3.16-rc4

[Julian Wollrath <jwollrath@web.de>]

Am Mon, 14 Jul 2014 21:10:47 +0200
schrieb "Rafael J. Wysocki" <rjw@rjwysocki.net>:

> On Monday, July 14, 2014 09:02:34 PM Rafael J. Wysocki wrote:
> > On Monday, July 14, 2014 08:34:22 PM Julian Wollrath wrote:
> > > Am Mon, 14 Jul 2014 20:21:19 +0200
> > > schrieb "Rafael J. Wysocki" <rjw@rjwysocki.net>:
> > > 
> > > > On Saturday, July 12, 2014 06:24:52 PM Julian Wollrath wrote:
> > > > > Hi,
> > > > > 
> > > > > > changing the brightness on my Thinkpad X230 with Intel
> > > > > > HD4000 graphics, stopped working after commit 886129a8eebe
> > > > > > (ACPI / video: change acpi-video brightness_switch_enabled
> > > > > > default to 0). Changing it back to 1, fixes the problem, if
> > > > > > "acpi_osi=!Windows 2012" is also set. Before that commit
> > > > > > just setting "acpi_osi=!Windows 2012" was enough to get
> > > > > > changing the brightness working.
> > > > >
> > > > > small correction: It setting "acpi_osi=!Windows 2012" does
> > > > > only help when using a kernel with commit 886129a8eebe as
> > > > > HEAD, with v3.16-rc4 setting
> > > > > video.brightness_switch_enabled=1 and acpi_osi=!Windows 2012
> > > > > or just one of them, does not make changing the brightness
> > > > > work again.
> > > > 
> > > > And reverting commit 751109aad583 (ACPI / video: Change the
> > > > default for video.use_native_backlight to 1) make that last
> > > > problem go away, right?
> > > > 
> > > > We are going to rever commit 886129a8eebe for other reasons, so
> > > > can you please revert it from 3.16-rc5 on your system and
> > > > report back?
> > > Yes, with both 751109aad583 and 886129a8eebe reverted, changing
> > > the brightness works again.
> > 
> > What if you revert 886129a8eebe alone?
> 
> I mean, what exactly do you need to pass to the kernel command line
> in that case to make brightness switching work?
I need to pass
  acpi_osi="!Windows 2012" video.brightness_switch_enabled=1 video.use_native_backlight=-1

If I leave one of these parameters out, the brightness switch stops
working.

Cheers,
Julian