Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755154Ab3ILCZx (ORCPT ); Wed, 11 Sep 2013 22:25:53 -0400 Received: from mail-pa0-f51.google.com ([209.85.220.51]:44409 "EHLO mail-pa0-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751424Ab3ILCZv (ORCPT ); Wed, 11 Sep 2013 22:25:51 -0400 Date: Thu, 12 Sep 2013 10:26:12 +0800 From: Aaron Lu To: Jani Nikula Cc: "Rafael J. Wysocki" , Daniel Vetter , ACPI Devel Mailing List , Matthew Garrett , Daniel Vetter , "intel-gfx@lists.freedesktop.org" , Yves-Alexis Perez , "linux-kernel@vger.kernel.org" , "dri-devel@lists.freedesktop.org" , Seth Forshee , "Lee, Chun-Yi" , Igor Gnatenko , Henrique de Moraes Holschuh , Lee Chun-Yi , Len Brown Subject: Re: [PATCH 2/2] ACPI / video / i915: Remove ACPI backlight if firmware expects Windows 8 Message-ID: <20130912022611.GA11167@aaronlu.sh.intel.com> References: <522D88C3.7000808@intel.com> <5155010.Y1gov7SKhP@vostro.rjw.lan> <87eh8wail7.fsf@intel.com> <1889567.vxI8heiC3B@vostro.rjw.lan> <20130911013206.GA556@mint-spring.sh.intel.com> <87hadrycf4.fsf@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87hadrycf4.fsf@intel.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2417 Lines: 53 On Wed, Sep 11, 2013 at 11:45:19AM +0300, Jani Nikula wrote: > On Wed, 11 Sep 2013, Aaron Lu wrote: > > It is possible the i915 driver decides not to register a backlight > > interface for the graphics card for some reason(memory allocation failed > > or it knows the native control does not work on this card or whatever), > > so I would prefer let i915 tell ACPI video that it has registered a > > native backlight control interface as Jani has said. > > > > Then together with the video.use_native_backlight, we can register or > > not register ACPI video backlight interface accordingly. Or rather, we > > can simply not register ACPI video backlight interface for Win8 systems > > as long as i915 indicates that it has native backlight control(if the > > native control is broken, i915 should fix it or blacklist it so that > > i915 will not indicate it has native backlight control and ACPI video > > will continue to register its own). > > > > How does this sound? > > Sounds good to me. > > Before plunging forward, have you observed any difference between the > boot modes? We have reports [1] that the backlight behaviour is Not yet from ACPI's point of view. > different with UEFI vs. UEFI+CSM or legacy boot. So I'm wondering if the > acpi_gbl_osi_data >= ACPI_OSI_WIN_8 check in patch 2/2 is the whole > story. This check in patch 2/2 is a policy: for Win8 system, we think the native backlight control has a better chance of working than the ACPI video's, so I think the check is enough in ACPI video. > > Further, if we tell the BIOS we're Windows 8 to use the tested BIOS code > paths, what guarantees do we have of UEFI+CSM or legacy boots working? I suppose the 'tested BIOS code paths' means the pure UEFI boot mode? I don't know what guatantees do we have since I don't know what happened underneath after the backlight register is set in i915 driver, you or other i915 driver people should know more than I do :-) BTW, after the backlight register is set in i915, is it that some find of firmware code will run in response to the setting of the register(e.g. the BLC_PWM_CTL/BLC_PWM_CPU_CTL/PCI_LBPC reg)? Thanks, Aaron -- 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/