On 04/22/2013 10:18 AM, joeyli wrote: > 於 五，2013-04-19 於 11:15 +0800，Aaron Lu 提到： >> 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 same >>>>> 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 value. >>>> Lenovo could also be supplying a driver which rounds values to the >>>> nearest working value or uses some other interface or something else. >>> >>> 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 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. >> >> The link for the document is here: >> http://msdn.microsoft.com/en-US/library/windows/hardware/jj159305 >> >> -Aaron >> > > 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" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
