linux-kernel - Re: [Intel-gfx] Linux 3.11-rc2 [backlight] [ASUS N56VZ]

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Message-ID: <1472278.oeeviaMfXH@vostro.rjw.lan>
Date:	Mon, 29 Jul 2013 22:03:31 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	* SAMÍ * <miaousami@...mail.com>
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]

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
> >
> >
> 
-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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