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

Jesse Barnes jbarnes at virtuousgeek.org
Tue Apr 26 08:16:02 PDT 2011

On Tue, 26 Apr 2011 11:01:30 +0100
Alan Cox <alan at lxorguk.ukuu.org.uk> wrote:

> > A lot of older hardware had one overlay that could be sourced to any
> > crtc, just not simultaneously.  The tricky part is the formats and
> > capabilities: alpha blending, color/chromakey, gamma correction, etc.
> > Even the current crtc gamma stuff is somewhat lacking in in terms of
> > what hardware is capable of (PWL vs. LUT, user defined conversion
> > matrices, gamut remapping, etc.).
> Rather than re-inventing enough wheels to run a large truck would it not
> make sense to make hardware sourced overlays Video4Linux objects in their
> entirity so you can just say "attach V4L object A as overlay B"
> That would provide format definitions, provide control interfaces for
> the surface (eg for overlays of cameras such as on some of the Intel
> embedded and non PC devices), give you an existing well understood API.
> For some hardware you are going to need this integration anyway so that
> you can do things like move a GEM object which is currently a DMA target
> of a capture device (as well as to fence it).
> For a software surface you could either expose it as a V4L object that
> is GEM or fb memory backed or at least use the same descriptions so that
> the kernel has a consistent set of descriptions for formats and we don't
> have user libraries doing adhoc format translation crap.
> A lot of capture hardware would map very nicely onto GEM objects I
> suspect and if you want to merge live video into Wayland it seems a
> logical path ?

Thanks Alan, of course that's a good idea, I'll see about integrating
the two.

Jesse Barnes, Intel Open Source Technology Center

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