Re: [PATCH] ACPI: Disable Windows 8 compatibility for some Lenovo ThinkPads

[joeyli <jlee@suse.com>]

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.

But, I discussed with Acer for this situation at last year, they didn't
force their ODM do test ACPI compatibility. They only test through
Windows 8 UI with Fn keys.


Thanks a lot!
Joey Lee

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