From mboxrd@z Thu Jan 1 00:00:00 1970 From: Aaron Lu Subject: Re: [PATCH] ACPI: Disable Windows 8 compatibility for some Lenovo ThinkPads Date: Mon, 22 Apr 2013 18:08:17 +0800 Message-ID: <51750C11.7060600@intel.com> 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> <1366597102.23707.92.camel@linux-s257.site> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Received: from mga02.intel.com ([134.134.136.20]:41329 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753070Ab3DVKGv (ORCPT ); Mon, 22 Apr 2013 06:06:51 -0400 In-Reply-To: <1366597102.23707.92.camel@linux-s257.site> Sender: linux-acpi-owner@vger.kernel.org List-Id: linux-acpi@vger.kernel.org To: joeyli Cc: Ben Jencks , Seth Forshee , Len Brown , "Rafael J. Wysocki" , linux-acpi@vger.kernel.org, Matthew Garrett On 04/22/2013 10:18 AM, joeyli wrote: > =E6=96=BC =E4=BA=94=EF=BC=8C2013-04-19 =E6=96=BC 11:15 +0800=EF=BC=8C= Aaron 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. >>> >>> Just checked; Windows 8 doesn't use the ACPI interface. It seems to= have >>> access to at least 100 distinct brightness levels. >> >> I just came across a document on win8 backlight control, it has word= s >> like this: >> " >> In Windows 8, the primary mechanism by which a platform should expos= e >> 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= =2E >> >> The link for the document is here: >> http://msdn.microsoft.com/en-US/library/windows/hardware/jj159305 >> >> -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. Thanks for the information, so this suggests that acpi interface is mostly used for pre-win8 OSes?(does win7 support WDDM?) One interesting thing is, if they do not support acpi interface, why they even bother to expose this interface in acpi table? -Aaron -- 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