Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753172Ab3IKInd (ORCPT ); Wed, 11 Sep 2013 04:43:33 -0400 Received: from mga14.intel.com ([143.182.124.37]:62343 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752067Ab3IKInb (ORCPT ); Wed, 11 Sep 2013 04:43:31 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.90,883,1371106800"; d="scan'208";a="293439595" From: Jani Nikula To: Aaron Lu , "Rafael J. Wysocki" Cc: Daniel Vetter , Aaron Lu , 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 In-Reply-To: <20130911013206.GA556@mint-spring.sh.intel.com> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo 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> User-Agent: Notmuch/0.16+64~g94fe857 (http://notmuchmail.org) Emacs/23.3.1 (x86_64-pc-linux-gnu) Date: Wed, 11 Sep 2013 11:45:19 +0300 Message-ID: <87hadrycf4.fsf@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1719 Lines: 42 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 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. 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? BR, Jani. [1] https://bugzilla.kernel.org/show_bug.cgi?id=47941#c96 -- Jani Nikula, 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/