On 04/22/2013 05:42 AM, Rafael J. Wysocki wrote: > 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"? Sorry, I don't know. According to the following bug page: https://bugzilla.kernel.org/show_bug.cgi?id=51231 "these systems" now include: thinkpad x230, t430s, t530, L430. -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
