Re: [PATCH] acpi: video: no automatic brightness changes by firmware

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

On 06/17/2013 07:27 PM, Rafael J. Wysocki wrote:
> On Monday, June 17, 2013 09:01:10 AM Aaron Lu wrote:
>> Starting from win8, MS backlight control driver will set bit 2 of the
>> parameter of control method _DOS, to inform firmware it should not
>> perform any automatic brightness changes. This mostly affects hotkey
>> notification deliver - if we do not set this bit, on hotkey press,
>> firmware may choose to adjust brightness level instead of sending out
>> notification and doing nothing.
>>
>> So this patch sets bit 2 when calling _DOS so that GUIs can show the
>> notification window on hotkey press.
>>
>> The MS document on win8 backlight control is here:
>> http://msdn.microsoft.com/en-US/library/windows/hardware/jj159305
>>
>> This patch solves problem for ASUS N56VZ and ASUS N56VJ, both for
>> notification delivery and for brightness control.
>>
>> Buglink: https://bugzilla.kernel.org/show_bug.cgi?id=52951
>> Buglink: https://bugzilla.kernel.org/show_bug.cgi?id=56711
>> Reported-and-tested-by: Micael Dias <kam1kaz3@gmail.com>
>> Reported-and-tested-by: Dan Garton <dan.garton@gmail.com>
>> Reported-and-tested-by: Bob Ziuchkovski <bob.ziuchkovski@gmail.com>
>> Signed-off-by: Aaron Lu <aaron.lu@intel.com>
> 
> OK, do we need that in -stable and if so, which ones?

Perhaps only for new kernels, since 3.7 and 3.8 are EOL-ed, so just
for 3.9. I don't think older kernels need change the behavior.

Thanks,
Aaron

> 
> Rafael
> 
> 
>> ---
>>  drivers/acpi/video.c | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/acpi/video.c b/drivers/acpi/video.c
>> index b8299f2..f8fa541 100644
>> --- a/drivers/acpi/video.c
>> +++ b/drivers/acpi/video.c
>> @@ -1543,12 +1543,12 @@ static int acpi_video_bus_put_devices(struct acpi_video_bus *video)
>>  
>>  static int acpi_video_bus_start_devices(struct acpi_video_bus *video)
>>  {
>> -	return acpi_video_bus_DOS(video, 0, 0);
>> +	return acpi_video_bus_DOS(video, 0, 1);
>>  }
>>  
>>  static int acpi_video_bus_stop_devices(struct acpi_video_bus *video)
>>  {
>> -	return acpi_video_bus_DOS(video, 0, 1);
>> +	return acpi_video_bus_DOS(video, 0, 0);
>>  }
>>  
>>  static void acpi_video_bus_notify(struct acpi_device *device, u32 event)
>>