[PATCH v3 0/4] Fix Win8 backlight issue

[Jörg Otte]

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.

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

Jörg