lkml.org 
[lkml]   [2013]   [Jul]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRe: [Intel-gfx] Linux 3.11-rc2 [backlight] [ASUS N56VZ]
Date
On Thursday, July 25, 2013 03:34:10 PM Jani Nikula wrote:
> On Thu, 25 Jul 2013, "Rafael J. Wysocki" <rjw@sisk.pl> wrote:
> > On Thursday, July 25, 2013 11:09:27 AM Jani Nikula wrote:
> >> On Thu, 25 Jul 2013, "Rafael J. Wysocki" <rjw@sisk.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@intel.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.


\
 
 \ /
  Last update: 2013-07-25 15:01    [W:0.091 / U:0.976 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site