[Intel-gfx] [PATCH 6/6] [drm/i915] implement drmmode overlay support v2

[Daniel Vetter]

On Wed, Sep 02, 2009 at 10:18:36AM +0200, Thomas Hellström wrote:
> > ...

> >Nope, Xv has one fixed format with stride == line length.
> 
> This is perhaps a little out of scope, but I'm pretty sure Xv sets
> up the HW needed stride of Xv images and pushes that to the client,
> and if the client doesn't adhere to it, that's a bug in the client.
> That's done in queryImageAttributes(). It's used, for example in the
> unichrome / openchrome drivers to make it possible to use the PCI
> DMA engine (which has stride limitations) for image uploads. IIRC
> it's in the Xv docs as well, but it was a couple of years ago I last
> looked at this.

Yep, you're right. The intel driver just does not use this and sets stride
values that do not fullfill the hw requirements. [Sidenote: Xv still often
confuses me because only a very tiny part is actually used by modern
applications. So I tend to sometimes overlook important things]. Still,
there are other isssues that force intel to (unnecessarily, IMHO) copy the
video frame. For reference and to make sure a future generic api supports
these cases (besides the obvious stuff like pixel layout, alignment,
strides which seems all to be handled by Xv):

* crtc rotation. Especially painful when the vertical and horizontal UV
  subsampling frequencies are not equal.
* the sw video decoder doesn't render into approprate memory (bo suitable
  for mapping into the GART/doing DMA/whater that's efficient).

> > ...

> >Fine. I'll just push this then as a device ioctl to bring usable video on
> >8xx to kms.
> 
> OK,
> Thanks,
> 
> Thomas

Thanks, Daniel
-- 
Daniel Vetter
Mail: daniel at ffwll.ch
Mobile: +41 (0)79 365 57 48