On 04/26/2016 01:05 PM, Daniel Vetter wrote:
On Tue, Apr 26, 2016 at 09:55:06PM +0300, Ville Syrjälä wrote:
On Tue, Apr 26, 2016 at 08:23:46PM +0200, Daniel Vetter wrote:
On Tue, Apr 26, 2016 at 08:40:45PM +0300, Ville Syrjälä wrote:
But really the reason for per-plane is hw composer from
Android. I don't see any point in designing an api that's needlessly
different from what the main user expects (even if it may be silly).
What are they doing that can't stuff the fences into an array
instead of props?
The hw composer interface is one in-fence per plane. That's really the
major reason why the kernel interface is built to match. And I really
don't think we should diverge just because we have a slight different
color preference ;-)
As long as you end up with a pile of fences somehow it'll work.
-Daniel
The relationship between layers and fences is only fuzzy and indirect
though. The relationship is really between the buffer you're displaying
on that layer, and the fence representing the work done to render into
that buffer. SurfaceFlinger just happens to bundle them together inside
the same struct hwc_layer_1 as an API convenience.
Which is kind of splitting hairs as long as you have a 1-to-1
relationship between layers and DRM planes. But that's not always the case.
A (per-CRTC?) array of fences would be more flexible. And even in the
cases where you could make a 1-to-1 mapping between planes and fences,
it's not that much more work for userspace to assemble those fences into
an array anyway.
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