[PATCH v3 0/4] Fix Win8 backlight issue

[Rafael J. Wysocki]

On Thursday, September 26, 2013 09:49:03 AM Jörg Otte wrote:
> 2013/9/25 Jani Nikula <jani.nikula at linux.intel.com>:
> > On Wed, 25 Sep 2013, Jörg Otte <jrg.otte at gmail.com> wrote:
> >> 2013/9/25 Jani Nikula <jani.nikula at linux.intel.com>:
> >>> On Wed, 25 Sep 2013, Aaron Lu <aaron.lu at intel.com> wrote:
> >>>> On Wed, Sep 25, 2013 at 10:29:37AM +0200, Jörg Otte wrote:
> >>>>> Backlight can't be modified with this patch set - neither with
> >>>>> function keys nor with the gui. It is a step backward to v3.11-rc1
> >>>
> >>> So both hotkeys and GUI work in v3.11-rc1? And v3.12-rc2?
> >>
> >> In  v3.11-rc1 it didn't work.
> >> Since a later rc (I don't remember exactly which) it did work.
> >> In v3.12-rc1/2 it does work.
> >> In v3.12-rc2 + Aaron's patch set it again doesn't work.
> >>
> >>>
> >>>> Thanks for the test.
> >>>>
> >>>> Please check /sys/class/backlight, is there only one link file
> >>>> intel_backlight?
> >>>
> >>> Indeed, are there others? fujitsu-laptop perhaps? If yes, try
> >>> CONFIG_FUJITSU_LAPTOP=n or an appropriate module blacklist.
> >>>
> >>> Just checking, you do have CONFIG_BACKLIGHT_CLASS_DEVICE=y?
> >>
> >> There is only one intel_backlight link.
> >> Yes, I have CONFIG_BACKLIGHT_CLASS_DEVICE=y
> >>
> >>> Embarrassingly there was a bug in i915 fixed just recently where the
> >>> backlight device wasn't registered for
> >>> CONFIG_BACKLIGHT_CLASS_DEVICE=m...
> >>>
> >>>> If so, please cd inside and try modify the brightness file using echo
> >>>> with some values in the range of 0 - max_brightness, does the
> >>>> backlight level change when you echo a new value? I guess it doesn't,
> >>>> or you wouldn't notice problem. If indeed so, perhaps file a bug at
> >>>> http://bugzilla.kernel.org, Drivers/Video(DRI-Intel)? I suppose Jani
> >>>> and Daniel can help fix your problem.
> >>>
> >>> Yup, please check the above, and report back.
> >>
> >> - echo 0..max_brightness > brightness does not work.
> >
> > Thanks for the info.
> >
> > How about v3.12-rc2 without Aaron's patches? Does intel_backlight also
> > not work there? How about the acpi_video0 (which I presume is present)
> > sysfs interface?
> >
> 
> Without Aaron's patches intel_backlight also does not work.
> But acpi_video0 does (and takes precedence I think).

So can you please open a bug entry at bugzilla.kernel.org against i915?

The fact that ACPI video works for you doesn't mean that intel_backlight
shouldn't, I suppose?

Rafael