[Intel-gfx] [REGRESSION BISECTED] backlight control stops workin with 3.14 and later

[Bertrik Sikken]

> On Sun, 17 Aug 2014, Bertrik Sikken <bertrik at sikken.nl> wrote:
>> On 15-8-2014 3:43, Jani Nikula wrote:
>>> On Thu, 14 Aug 2014, Bertrik Sikken <bertrik at sikken.nl> wrote:
>>
>>>> Attached is dmesg output from booting kernel 3.14-2 (debian unstable)
>>>> with drm.debug=0xe and the samsung_laptop module enabled, from my
>>>> Samsung N150plus netbook.
>>>
>>> Have you tried 3.15?
>>
>> I've built the v3.15 kernel (using the .config file from debian
>> unstable and doing make oldconfig).
>>
>> The backlight is at maximum brightness after boot and I can't control
>> it using the backlight buttons, nor by writing to
>> /sys/class/backlight/samsung/brightness
>> (say half the value or 1/10th of max_brightness)
>>
>> Backlight does work when writing
>> /sys/class/backlight/intel_backlight/brightness
>
> How about disabling samsung backlight module with 3.15?

I'm not sure what you mean by that.

As I understand it, there are three ways to control the backlight on this
netbook: using intel_backlight, samsung_laptop (using a "sabi" interface)
and acpi_video.
Backlight control using the samsung_laptop driver no longer seems to work
after the change. If I disable it (e.g. by blacklisting it), I expect it
to no longer work at all obviously.

What do you want me to test exactly?

Kind regards,
Bertrik