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

[Aaron Lu <aaron.lu@intel.com>]

On 07/15/2014 03:17 AM, Rafael J. Wysocki wrote:
> On Monday, July 14, 2014 08:56:29 PM Julian Wollrath wrote:
>> 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.
> 
> With 886129a8eebe reverted you should not need video.brightness_switch_enabled=1.
> 
> Aaron, what do you think?

I agree.

I suppose Julian is not using an standard GUI so he needs the in kernel
processing of the backlight event. And his laptop has a broken ACPI
interface in Win8 mode, so he also needs the "!Windows 2012" option.

With a standard GUI environment, his system would have only one
interface left: the GPU one and everything should work. But of course,
that may not be his config.

Thanks,
Aaron