Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755900Ab3GYMrx (ORCPT ); Thu, 25 Jul 2013 08:47:53 -0400 Received: from hydra.sisk.pl ([212.160.235.94]:39697 "EHLO hydra.sisk.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755450Ab3GYMrs (ORCPT ); Thu, 25 Jul 2013 08:47:48 -0400 From: "Rafael J. Wysocki" To: Jani Nikula Cc: Linus Torvalds , Aaron Lu , Matthew Garrett , * =?ISO-8859-1?Q?SAM=CD?= * , intel-gfx , LKML , ACPI Devel Maling List , Igor Gnatenko Subject: Re: [Intel-gfx] Linux 3.11-rc2 [backlight] [ASUS N56VZ] Date: Thu, 25 Jul 2013 14:57:52 +0200 Message-ID: <5730704.o2aLKRMvVz@vostro.rjw.lan> User-Agent: KMail/4.9.5 (Linux/3.10.0+; KDE/4.9.5; x86_64; ; ) In-Reply-To: <877ggeyg1p.fsf@intel.com> References: <2024506.rXjN91yI0W@vostro.rjw.lan> <877ggeyg1p.fsf@intel.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="utf-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3494 Lines: 81 On Thursday, July 25, 2013 03:34:10 PM Jani Nikula wrote: > On Thu, 25 Jul 2013, "Rafael J. Wysocki" wrote: > > On Thursday, July 25, 2013 11:09:27 AM Jani Nikula wrote: > >> On Thu, 25 Jul 2013, "Rafael J. Wysocki" 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 > >> 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. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/