From mboxrd@z Thu Jan  1 00:00:00 1970
From: Chris Wilson <chris@chris-wilson.co.uk>
Subject: Re: [PATCH] drm/i915: The hw does not support source
	offsets into a YUV linear fb
Date: Tue, 18 Dec 2012 23:26:47 +0000
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To: Daniel Vetter <daniel@ffwll.ch>
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On Tue, 18 Dec 2012 23:03:02 +0000, Chris Wilson <chris@chris-wilson.co.uk> wrote:
> On Tue, 18 Dec 2012 23:57:05 +0100, Daniel Vetter <daniel@ffwll.ch> wrote:
> > On Tue, Dec 18, 2012 at 11:51 PM, Chris Wilson <chris@chris-wilson.co.uk> wrote:
> > > As we can only pass in the base address of the first plane, we can not
> > > control the offset into the subsampled chroma planes. This means that we
> > > cannot support a source offset into a YUV* linear framebuffer. However,
> > > for tiled framebuffers we can tell the hardware which pixels to read
> > > from. So if we see a source offset into a linear YUV framebuffer, report
> > > the invalid value back to userspace.
> > >
> > > Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> > 
> > Aren't all the yuv formats we support packet planar? So I think we
> > should be able to support source offsets, as long as x is even ...
> > Probably not worth the bother though.

Ok, double-checked and they are using a packed format, so it should be
possible given the single linear offset and a co-operative userspace to
pass in valid x/y offsets.

I'm no longer trying to use this in the ddx, so you can leave it in
until someone with a little more clue feels like tackling it.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre