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.
-Aaron
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