From: Aaron Lu <aaron.lu@intel.com>
To: John Marsden <john.d.marsden@gmail.com>
Cc: linux-acpi@vger.kernel.org, platform-driver-x86@vger.kernel.org,
Matthew Garrett <matthew.garrett@nebula.com>
Subject: Re: PROBLEM: [Toshiba Portege Z835] Brightness control lost after suspend
Date: Fri, 1 Aug 2014 10:42:55 +0800 [thread overview]
Message-ID: <20140801024255.GF30211@aaronlu.sh.intel.com> (raw)
In-Reply-To: <CACiopZCrfyqxgqS8NoF5Hi-K-0zM+8YHsyXqfhWKgjU65n4-Pg@mail.gmail.com>
On Thu, Jul 31, 2014 at 10:05:14PM +0100, John Marsden wrote:
> On 31 July 2014 09:09, Aaron Lu <aaron.lu@intel.com> wrote:
> > Please add acpi_backlight=vendor to kernel cmdline and see if that makes
> > the backlight work. What it does is to tell ACPI video module not to
> > create the acpi_videoX sysfs interface and let's see if X server will
> > pick up the intel_backlight one.
>
> Adding acpi_backlight=vendor to the kernel cmdline results in the
> brightness controls not working from first boot, not just after a
> suspend.
That probably because X server now picks the toshiba_acpi interface
instead of the intel_backlight one.
A workaround from user space is to specify the backlight interface you
want to use in xorg.conf, an example is here:
https://bugs.debian.org/cgi-bin/bugreport.cgi?msg=78;att=0;bug=651741
Section "Device"
Identifier "Intel Graphics"
Driver "intel"
Option "AccelMethod" "sna"
Option "Backlight" "intel_backlight"
Driver "intel"
BusID "PCI:0:2:0"
EndSection
Alternatively, we can disable the acpi_video and toshiba_acpi interfaces
in the kernel so that only intel_backlight is available. I'm not sure
how to do this nicely, I've cc-ed platform x86 mailing list.
Regards,
Aaron
>
> Detailed test results:
>
> After fresh boot into 3.16-rc with acpi_backlight=vendor added to the
> kernel cmdline
> ls -l /sys/class/backlight
> total 0
> lrwxrwxrwx 1 root root 0 Jul 31 21:38 intel_backlight ->
> ../../devices/pci0000:00/0000:00:02.0/drm/card0/card0-LVDS-1/intel_backlight
> lrwxrwxrwx 1 root root 0 Jul 31 21:38 toshiba ->
> ../../devices/LNXSYSTM:00/LNXSYBUS:00/TOS6208:00/backlight/toshiba
>
> Attempts to adjust brightness via user interfaces (system settings and
> function keys) fail to change brightness.
>
> It remains possible to adjust brightness by directly writing to
> /sys/class/backlight/intel_backlight/brightness but, as before, not by
> writing to /sys/class/backlight/toshiba/brightness.
>
> After suspend and resume same test results.
>
> Regards, John
next prev parent reply other threads:[~2014-08-01 2:42 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-07-28 20:52 PROBLEM: [Toshiba Portege Z835] Brightness control lost after suspend John Marsden
2014-07-29 14:28 ` Aaron Lu
2014-07-29 18:20 ` John Marsden
2014-07-30 8:32 ` Aaron Lu
2014-07-30 17:11 ` John Marsden
2014-07-31 8:09 ` Aaron Lu
2014-07-31 21:05 ` John Marsden
2014-08-01 2:42 ` Aaron Lu [this message]
2014-08-04 20:32 ` John Marsden
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