Re: [PATCH v4] drm/i915: add support for Z-order of planes for VLV.

[Yu Dai <yu.dai@intel.com>]

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Chris,

This looks like a hw specific value which is difficult to understand. 
However, the definition of these values are just a list of available 
options of z-order. On Intel VLV, there is only 6 options for the three 
planes Primary, Sprite A and Sprite B. Cursor is always on top. For 
example, "P1S1S2C1" means z-order (from bottom to top) of Primary -> 
Sprite A -> Sprite B -> Cursor.

#define P1S1S2C1        0
#define P1S2S1C1        8
#define S2P1S1C1        1
#define S2S1P1C1        9
#define S1P1S2C1        4
#define S1S2P1C1        6

In theory, if hw supports, each CRTC may have their own plane z-order if 
user intentionally wants that happens. The pipe info (0 or 1) is packed 
into z-order value with extra bit (bit 31).

Thanks,
Alex

On 14-03-04 12:20 AM, Chris Wilson wrote:
> On Mon, Mar 03, 2014 at  02:12:28PM -0800, yu.dai@intel.com wrote:
 >> From: "Yu(Alex) Dai" <yu.dai@intel.com>
 >>
 >> Add "zorder" property to crtc to control Z-order of sprite and
 >> primary planes. The alpha channel of the planes can be enabled or
 >> disabled during Z-order change.
 >
 > Can I just say that is an abonimal user interface. You expect the
 > client to encode a hw specific value into a CRTC property that
 > affects global state. and given the two properties on the two CRTCs,
 > which should userspace believe? -Chris
 >



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