[Mesa-dev] vdpau_interop extension oddities

[Christian König]

Hi Thomas,

I'm on sick leave, but will try to quickly answer your questions.

But don't be disappointed if you don't hear back from me before Monday.

Am 01.02.2017 um 15:56 schrieb Thomas Hellstrom:
> Hi, Christian,
>
> I'm looking through the mesa vdpau interop code and found something that
> looks strange to me:
>
> (dmabuf part)
>
> For video surfaces, it looks like vdpau exports a handle to a 2D_ARRAY
> texture.
> Later in the mesa state tracker, that handle is used to back a "fake"
> single slice 2D texture from which we create views like if it were an
> array texture, using the layer_override. I guess this would cause
> numerous problems when trying to render to these textures or using
> texSubImage etc.

Hui? That's not how I remembered it.

For the dma-buf part we export one layer of a 2D_ARRAY texture and then 
import that as "normal" 2D texture.

The layer_override is only for the old code path used by Nouveau, e.g. 
exporting the pipe objects directly and then access only a certain layer.

> Wouldn't the correct solution be to have vdpau export a single layer of
> the array texture (using the whandle offset pointing to the layer start)
> which is then reinterpreted by the driver, not the state tracker, as a
> true non-array texture.

Actually that is exactly as it should be, yes.

> And if for some reason the driver doesn't support reinterpreting and
> offseting like this wouldn't it be possible to hide the layer_override
> inside the driver for surface, sampler_view and transfer object
> purposes, as part of the texture internal format?

As noted above the layer_override should only be used for the old code path.

Could be that we accidentally set layer_override in the new code path as 
well, but that would clearly be a bug.

Regards,
Christian.

>
> Thanks,
>
> Thomas
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