Hey Daniel,
On Tue, 2018-05-08 at 09:55 +0200, Daniel Vetter wrote:
> On Tue, May 08, 2018 at 01:52:01AM -0300, Ezequiel Garcia wrote:
> > It's perfectly possible to get dumb buffers out of drivers
> > that don't support modeset. This is the case of vgem,
> > which can be used to export dmabuf to run various tests.
> >
> > Inspired by commit f3f4c4d68a28 ("drm: Allow CAP_PRIME on !MODESET").
>
> Prime makes sense, because render-only drivers _really_ want to be able to
> share buffers.
>
> But dumb buffers are really meant for dumb userspace running on kms
> drivers only, there's no need ever to tell userspace that dumb buffers are
> supported on non-kms drivers. It's kinda abuse of ioctls, but oh well,
> uapi is fixed forever. And you can still call the ioctls if you know
> they're there (which is always the case for the render-side of drm,
> there's no generic alloc ioctl for those).
>
Right, I see.
Well, I was mostly interested in dry testing, and vgem seemed a good
candidate for a dma-buf exporter. For instance, this would be useful
to test dmabuf video4linux pipelines.
Now, is this is a nack, then the other path is to support proper prime
operations on virtio-gpu (which I'm also working on).
Thanks for reviewing!
Eze
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