[RFC] Updated plane support v3

[Jesse Barnes]

On Tue, 21 Jun 2011 10:55:39 +0200
Marcus Lorentzon <marcus.xm.lorentzon at stericsson.com> wrote:

> On 06/20/2011 10:11 PM, Jesse Barnes wrote:
> > This version adds both source and dest rect params to the set_plane
> > ioctl, and makes the source fixed point to support hardware that needs
> > it.
> >
> > I haven't changed the name of the SNB implementation yet (per Chris's
> > suggestions) but will before it gets upstream.
> >
> > I'd be interested to see whether these interfaces will work for other
> > hardware, so please take a close look at them and ideally implement them
> > on your hardware to make sure (see my userspace example code from
> > earlier posts if you want something to crib from).
> >
> > Thanks,
> > Jesse
> >
> >    
> Is it possible to position a plane above and below the "normal" crtc 
> framebuffer? Plane z-order is unsigned, and I would assume 0 is default 
> z-order.
> Applications will need to position planes above and below crtc normal 
> framebuffer. Below when using a translucent or color keyed framebuffer, 
> and above if framebuffer is opaque.

I was thinking 0 would be the bottom layer.  But either way we don't
have a way of getting the primary plane z position atm, so it'll be
hard to position a new plane above or below the main plane...  I'm ok
with a signed value here, but the real meaning will be defined by a new
ioctl we use to get plane blending restrictions, z order, and such.

> So maybe add a one liner comment about z-order meaning and make it 
> signed unless ordering should be solved in another way.
> 
> And should it be possible to only define planes with no crtc framebuffer 
> at all? Use case, for example letter boxed video on black background 
> with small UI controls/subtitles. In this case it's not power efficient 
> to have a fullscreen fb with mostly if not all transparent pixels.

A particular driver may be able to expose that somehow, maybe by
allowing clients to define a special fb handle that can be used to
indicate no plane should be bound to the CRTC as the "primary" plane.

-- 
Jesse Barnes, Intel Open Source Technology Center