Re: [PATCH v3 1/4] dma-buf: add support for virtio exported objects

[David Stevens]

On Thu, May 14, 2020 at 12:45 AM Daniel Vetter <daniel@xxxxxxxx> wrote:
> On Wed, Mar 11, 2020 at 12:20 PM David Stevens <stevensd@xxxxxxxxxxxx> wrote:
> >
> > This change adds a new dma-buf operation that allows dma-bufs to be used
> > by virtio drivers to share exported objects. The new operation allows
> > the importing driver to query the exporting driver for the UUID which
> > identifies the underlying exported object.
> >
> > Signed-off-by: David Stevens <stevensd@xxxxxxxxxxxx>
>
> Adding Tomasz Figa, I've discussed this with him at elce last year I
> think. Just to make sure.
>
> Bunch of things:
> - obviously we need the users of this in a few drivers, can't really
> review anything stand-alone

Here is a link to the usage of this feature by the currently under
development virtio-video driver:
https://markmail.org/thread/j4xlqaaim266qpks

> - adding very specific ops to the generic interface is rather awkward,
> eventually everyone wants that and we end up in a mess. I think the
> best solution here would be if we create a struct virtio_dma_buf which
> subclasses dma-buf, add a (hopefully safe) runtime upcasting
> functions, and then a virtio_dma_buf_get_uuid() function. Just storing
> the uuid should be doable (assuming this doesn't change during the
> lifetime of the buffer), so no need for a callback.

So you would prefer a solution similar to the original version of this
patchset? https://markmail.org/message/z7if4u56q5fmaok4