From mboxrd@z Thu Jan 1 00:00:00 1970 From: joeyli Subject: Re: [PATCH] ACPI: Disable Windows 8 compatibility for some Lenovo ThinkPads Date: Mon, 22 Apr 2013 10:18:22 +0800 Message-ID: <1366597102.23707.92.camel@linux-s257.site> References: <1360599681-24781-1-git-send-email-seth.forshee@canonical.com> <5158E8A0.3050904@intel.com> <20130401130340.GA3269@thinkpad-t410> <515AA007.1050305@intel.com> <20130402130000.GA12381@thinkpad-t410> <515BD48B.7000901@bjencks.net> <5170B6ED.2040408@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Received: from smtp.nue.novell.com ([195.135.221.5]:54670 "EHLO smtp.nue.novell.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753616Ab3DVCTh (ORCPT ); Sun, 21 Apr 2013 22:19:37 -0400 In-Reply-To: <5170B6ED.2040408@intel.com> Sender: linux-acpi-owner@vger.kernel.org List-Id: linux-acpi@vger.kernel.org To: Aaron Lu Cc: Ben Jencks , Seth Forshee , Len Brown , "Rafael J. Wysocki" , linux-acpi@vger.kernel.org, Matthew Garrett =E6=96=BC =E4=BA=94=EF=BC=8C2013-04-19 =E6=96=BC 11:15 +0800=EF=BC=8CAa= ron Lu =E6=8F=90=E5=88=B0=EF=BC=9A > On 04/03/2013 03:04 PM, Ben Jencks wrote: > > On 04/02/2013 09:00 AM, Seth Forshee wrote: > >> On Tue, Apr 02, 2013 at 05:08:23PM +0800, Aaron Lu wrote: > >>> > >>> I really wondered, how Windows handled this, it should have the s= ame > >>> problem, unless they are not using the acpi video interface? > >> > >> I can only guess. > >> > >> I think I remember reading that Windows 8 does smooth backlight > >> transitions, so it may well hit every intermediate brightness valu= e. > >> Lenovo could also be supplying a driver which rounds values to the > >> nearest working value or uses some other interface or something el= se. > >=20 > > Just checked; Windows 8 doesn't use the ACPI interface. It seems to= have > > access to at least 100 distinct brightness levels. >=20 > I just came across a document on win8 backlight control, it has words > like this: > " > In Windows 8, the primary mechanism by which a platform should expose > its display brightness control functionality is the Windows Display > Driver Model (WDDM) miniport Device Driver Interfaces (DDI). > " > So looks like, on win8, ACPI interface is not used for these systems. >=20 > The link for the document is here: > http://msdn.microsoft.com/en-US/library/windows/hardware/jj159305 >=20 > -Aaron >=20 Per WDDM document, OEM/ODM should keep the ACPI methods (_BQL, _BCM, _BQC) available for compliant to the OS that doesn't support WDDM, e.g. XP, Vista. But, I discussed with Acer for this situation at last year, they didn't force their ODM do test ACPI compatibility. They only test through Windows 8 UI with Fn keys. Thanks a lot! Joey Lee -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html