From mboxrd@z Thu Jan 1 00:00:00 1970 From: Matthew Garrett Subject: Re: [PATCH 2/2] ACPI / video / i915: Remove ACPI backlight if firmware expects Windows 8 Date: Wed, 11 Sep 2013 10:30:17 +0000 Message-ID: <1378895417.945.2.camel@x230.lan> 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> <1378889140.945.0.camel@x230.lan> <87d2ofy7li.fsf@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <87d2ofy7li.fsf@intel.com> Content-Language: en-US Content-ID: <4847B66A956DC249A340F90BA1CD9519@namprd05.prod.outlook.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: intel-gfx-bounces+gcfxdi-intel-gfx=m.gmane.org@lists.freedesktop.org Errors-To: intel-gfx-bounces+gcfxdi-intel-gfx=m.gmane.org@lists.freedesktop.org To: Jani Nikula Cc: Aaron Lu , Henrique de Moraes Holschuh , Seth Forshee , Daniel Vetter , "intel-gfx@lists.freedesktop.org" , Yves-Alexis Perez , "linux-kernel@vger.kernel.org" , "dri-devel@lists.freedesktop.org" , "Rafael J. Wysocki" , ACPI Devel Mailing List , "Lee, Chun-Yi" , Igor Gnatenko , Lee Chun-Yi , Len Brown List-Id: linux-acpi@vger.kernel.org On Wed, 2013-09-11 at 13:29 +0300, Jani Nikula wrote: > On Wed, 11 Sep 2013, Matthew Garrett wrote: > > On Wed, 2013-09-11 at 11:45 +0300, Jani Nikula wrote: > > > >> 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? > > > > We have no evidence of Windows behaving differently based on the exposed > > firmware type. > > By "behaving differently", do you mean internally adapting to the boot > mode, or exhibiting different behaviour to the user? As far as backlight control goes, both. > We have evidence of the firmware behaving differently (VBT, backlight) > based on the boot mode, all else being equal. We don't adapt to that, > and we fail. I don't know if we should adapt, or do things differently > altogether. I don't even know if Windows 8 works on all boot modes on > the machines in question. Sure, but Windows knows nothing about VBT or opregion-backed backlight control. That's up to the Intel driver. -- Matthew Garrett