[RFC] drm: add overlays as first class KMS objects

Keith Packard keithp at keithp.com
Mon Apr 25 16:37:46 PDT 2011

On Mon, 25 Apr 2011 16:22:16 -0700, Jesse Barnes <jbarnes at virtuousgeek.org> wrote:

> Yes, that matches my understanding as well.  I've deliberately made the
> implementation flexible there though, under the assumption that some
> hardware allows a plane to be directed at more than one CRTC (though
> probably not simultaneously).

So you create a scanout buffer and assign it to the appropriate slot in
the CRTC. Describing *how* the CRTC mixes pixels would be a good idea,
so the ordering of the slots might be relevant, and they might have a
blend mode (per-pixel alpha values, color key, separate alpha plane, etc).

> Arguably, this is something we should have done when the
> connector/encoder split was done (making planes in general first class
> objects).  But with today's code, treating a CRTC as a pixel pump and a
> primary plane seems fine, with overlays tacked onto the side as
> secondary pixel sources but tied to a specific CRTC.

I know of hardware that needs a lot more than one overlay...

keith.packard at intel.com
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