Hi,
- for the runtime upcasting the usual approach is to check the ->ops
pointer. Which means that would need to be the same for all virtio dma_bufs, which might get a bit awkward. But I'd really prefer we not add allocator specific stuff like this to dma-buf.
This is exactly the problem, it gets messy quickly, also when it comes to using the drm_prime.c helpers ...
take care, Gerd