[trusty] ACPI / video: Change the default for video.use_native_backlight to 1

[Yidi Lin]

I would like to propose this patch for trusty kernel again.

According to upstream's discussion[1], following patches are necessary.

commit fbc9fe1b4f222a7c575e3bd8e9defe59c6190a04
Author: Aaron Lu <aaron.lu at intel.com>
Date:   Fri Oct 11 21:27:45 2013 +0800

    ACPI / video: Do not register backlight if win8 and native interface exists

commit 0e9f81d3b7cd0649a3bc437391b6a0650f98f844
Author: Aaron Lu <aaron.lu at intel.com>
Date:   Tue Feb 18 13:54:20 2014 +0800

    ACPI / video: Add systems that should favour native backlight interface

commit 751109aad5834375ca9ed0dcfcd85a00cbf872b5
Author: Rafael J. Wysocki <rafael.j.wysocki at intel.com>
Date:   Thu Jun 5 22:47:35 2014 +0200

    ACPI / video: Change the default for video.use_native_backlight to 1

First two patches have already committed in trusty kernel.
And "video.use_native_backlight=1" fixes most cases of backlight issues[2].

So I consider this patch could be backported to trusty kernel.

Edward

[1]: http://marc.info/?l=linux-acpi&m=140429106012604&w=2
[2]: bug 1284030 / bug 1284030 / bug 1332437 / bug 1250401 / bug 1332379 /
      bug 1354253 / bug 1341988 / bug 1354313

On Thu, Jun 19, 2014 at 10:27 AM, Yidi Lin <yidi.lin at canonical.com> wrote:
> After checking upstream commit logs, several patches are needed for
> use_native_backlight=1.
> But it does not guarantee that the patches work for every model.
> It seems that adding a quirk for Dell Inspiron 5737 is much safer.
> I will take Seth's suggestion.
> Thanks.
>
> On Wed, Jun 18, 2014 at 8:37 PM, Seth Forshee
> <seth.forshee at canonical.com> wrote:
>> On Wed, Jun 18, 2014 at 10:21:31AM +0800, Yidi Lin wrote:
>>> Thanks for reminding.
>>>
>>> I will check what patches are necessary when use_native_backlight=1 is in use.
>>
>> Your other option is a sauce patch to add this machine to the dmi list
>> in acpi_video.c. I think this is the safer option to avoid regressions
>> with other hardware in 3.13. They've been working on these backlight
>> issues for a long time because the solutions kept causing regressions on
>> various machines, so I'm going to remain skeptical that they've really
>> eliminated all the regressions until the changes have been upstream for
>> quite a bit longer.
>>
>> Seth
>>
>>>
>>> On Tue, Jun 17, 2014 at 7:40 PM, Tim Gardner <tim.gardner at canonical.com> wrote:
>>> > On 06/16/2014 10:55 PM, Yidi Lin wrote:
>>> >> BugLink: https://bugs.launchpad.net/bugs/1250401
>>> >>
>>> >> This patch is committed in v3.16-rc1 which fixes win8 backlight issue.
>>> >> I had verified this patch for bug #1250401.
>>> >>
>>> >> This patch also fixes bug #1284030.
>>> >>
>>> >> commit 751109aad5834375ca9ed0dcfcd85a00cbf872b5
>>> >> Author: Rafael J. Wysocki <rafael.j.wysocki at intel.com>
>>> >> Date:   Thu Jun 5 22:47:35 2014 +0200
>>> >>
>>> >>     ACPI / video: Change the default for video.use_native_backlight to 1
>>> >>
>>> >>     Now that we're hoping to have resolved all of the problems with
>>> >>     video.use_native_backlight=1, make that the default at last.
>>> >>
>>> >>     Link: http://marc.info/?l=linux-acpi&m=139716088401106&w=2
>>> >>     Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki at intel.com>
>>> >>
>>> >
>>> > While this patch may fix back light issues for a Dell Inspiron 5737, how
>>> > do you know changing the default won't break other platforms ? I imagine
>>> > there was a bit of work that went into back light support between 3.13
>>> > and 3.16-rc1, so I'm not sure flipping the default in 3.13 is sufficient.
>>> >
>>> > rtg
>>> > --
>>> > Tim Gardner tim.gardner at canonical.com
>>>
>>> --
>>> kernel-team mailing list
>>> kernel-team at lists.ubuntu.com
>>> https://lists.ubuntu.com/mailman/listinfo/kernel-team