Date:	Mon, 29 Jul 2013 23:53:59 +0200
From:	* SAMÍ * <miaousami@...mail.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
CC:	Jani Nikula <jani.nikula@...ux.intel.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Aaron Lu <aaron.lu@...el.com>,
	Matthew Garrett <mjg59@...f.ucam.org>,
	intel-gfx <intel-gfx@...ts.freedesktop.org>,
	LKML <linux-kernel@...r.kernel.org>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	Igor Gnatenko <i.gnatenko.brain@...il.com>
Subject: Re: [Intel-gfx] Linux 3.11-rc2 [backlight] [ASUS N56VZ]

When I make acpi_video_backlight_quirks() return false:
- the Fn+x keys are not working anymore (remember that they didn't work 
in 3.10 nor 3.9)
- At least the backlight remains on at boot.
- Gnome brightness settings do not work anymore. Neither do xbacklight.
- Writing to /sys/class/backlight/intel_backlight/brightness works

Regards,
Sam

On 07/29/2013 10:03 PM, Rafael J. Wysocki wrote:
> On Monday, July 29, 2013 09:36:31 PM * SAMÍ * wrote:
>> Hi Rafael,
>>
>>
>> did you commit a full revert?
> Yes, but I left acpi_video_backlight_quirks() (in drivers/acpi/video_detect.c)
> that is used to decide what to do with _DOS.
>
> Can you please check if making that function always return 'false' makes any
> difference?
>
> Rafael
>
>
>> Because I am experiencing quite weird things in rc3.
>> Do we have a bug opened to discuss about it?
>>
>> Here is what I can observe:
>> 1) During boot, probably when loading the driver, backlight gets off (or
>> to a level low enough to make me feel it is off)
>> 2) When I am playing with my Fn+x keys, I am getting a completely full /
>> completely low brightness with no intermediate steps
>> 3) When I am playing with my Fn+x keys while gnome brightness settings
>> panel is open, I am recovering intermediate steps but the Fn+x keys
>> behavior is inverted (the key supposed to lower the brightness make it
>> increase and vice-versa. Note that the gnome brightness indicator also
>> gets inverted).
>> 4) Playing with the mouse on gnome brightness settings is working,
>> except that on the minimum level, backlight gets off
>> 5) Writing to /sys/class/backlight/intel_backlight/brightness works
>>
>>
>> Regards
>>
>> On 07/25/2013 02:57 PM, Rafael J. Wysocki wrote:
>>> On Thursday, July 25, 2013 03:34:10 PM Jani Nikula wrote:
>>>> On Thu, 25 Jul 2013, "Rafael J. Wysocki" <rjw@...k.pl> wrote:
>>>>> On Thursday, July 25, 2013 11:09:27 AM Jani Nikula wrote:
>>>>>> On Thu, 25 Jul 2013, "Rafael J. Wysocki" <rjw@...k.pl> wrote:
>>>>>>> Well, I wonder what about the appended (untested) patch?
>>>>>> Rafael, before going there, I've been trying to wrap my (poor, rusty
>>>>>> after vacation) head around
>>>>>>
>>>>>> commit 8c5bd7adb2ce47e6aa39d17b2375f69b0c0aa255
>>>>>> Author: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>>>>>> Date:   Thu Jul 18 02:08:06 2013 +0200
>>>>>>
>>>>>>       ACPI / video / i915: No ACPI backlight if firmware expects Windows 8
>>>>>>
>>>>>> and I can't see how it could work.
>>>>> Well, if it didn't work, people wouldn't see either improvement or breakage
>>>>> from it, but they do see that, so it evidently works. :-)
>>>> I didn't claim it didn't work, just that *I* didn't see how it could. ;)
>>>>
>>>>>> First, the ACPI_VIDEO_SKIP_BACKLIGHT flag seems to be checked before
>>>>>> it's actually set anywhere.
>>>>> Are you sure about that?
>>>>>
>>>>> acpi_video_bus_add() is the .add() callback routine for acpi_video_bus which
>>>>> in fact is an ACPI driver (the naming sucks, but I didn't invent it).  This
>>>>> means that acpi_video_bus_add() can only be called *after* acpi_video_bus
>>>>> has been registered with the ACPI subsystem (and the driver core).  That
>>>>> is done by acpi_bus_register_driver() and, guess what?, this happens in
>>>>> __acpi_video_register().  So clearly, acpi_video_bus_add() *cannot* run before
>>>>> __acpi_video_register().
>>>> Right. I totally missed the call within the ternary operator. Thanks for
>>>> the explanation, and apologies for the noise.
>>>>
>>>>>> Second, with i915 that has opregion support, __acpi_video_register()
>>>>>> should only ever get called once. Which means the acpi_walk_namespace()
>>>>>> with video_unregister_backlight() should never get called in register.
>>>>>>
>>>>>> Please enlighten me.
>>>>> Actually, that's correct, so we don't need the whole
>>>>> video_unregister_backlight() thing, calling acpi_video_backlight_quirks() would
>>>>> be sufficient.
>>>>>
>>>>> Ah, one more reason to do a full revert.  I'm thinking, though, that I'll leave
>>>>> acpi_video_backlight_quirks() as is so that it can be used by
>>>>> acpi_video_bus_(start)|(stop)_devices(), because that doesn't seem to cause
>>>>> problems to happen.
>>>> I observe that for the regular non-quirk acpi_video_register() call,
>>>> acpi_video_backlight_quirks() won't be called during register, but it
>>>> will get called later. This might have subtle effects later on, don't
>>>> you think?
>>> Yes, it might, but after dropping ACPI_VIDEO_SKIP_BACKLIGHT it should be OK.
>>>
>>>> As to the original problem, and your patch in this thread, what do you
>>>> think about having another value in acpi_backlight kernel parameter for
>>>> it? Having an i915 module parameter to tell acpi to use or not use
>>>> quirks seems odd, since the i915 is not really taking over
>>>> anything. It's just passing the info on to acpi.
>>> I agree, I'm going to send a full revert in a while and we'll think what to
>>> do about all that later.
>>>
>>> Thanks,
>>> Rafael
>>>
>>>

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