On Sunday, April 21, 2013 07:07:04 PM Aaron Lu wrote: > On 04/21/2013 06:06 AM, Rafael J. Wysocki wrote: > > On Friday, April 19, 2013 11:15:57 AM Aaron Lu wrote: > >> 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 > > > > OK, so what does that mean for the issue at hand? > > That means, we should not try to use acpi video interface to control > backlight on these systems if they are in win8 mode. In that case, how are we going to indentify "these systems"? Rafael -- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center. -- 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
