[PATCH v3 0/4] Fix Win8 backlight issue

Jani Nikula jani.nikula at linux.intel.com
Wed Sep 25 09:17:04 PDT 2013

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.
>> Embarrassingly there was a bug in i915 fixed just recently where the
>> backlight device wasn't registered for
>>> 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?


>>>> Video driver: i915
>>>> FUJITSU LIFEBOOK AH532/FJNBB1C, BIOS Version 1.09 05/22/2012
>>>> acpi_backlight=video works.
> Jörg

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