On 02/04/15 11:08, Florian Echtler wrote:

Hello Hans,

On 04.02.2015 09:08, Hans Verkuil wrote:

quoted

I remain very skeptical about the use of dma-contig (or dma-sg for that
matter). Have you tried using vmalloc and check if the USB core isn't
automatically using DMA transfers for that?

Basically I would like to see proof that vmalloc is not an option before
allowing dma-contig (or dma-sg if you can figure out why that isn't
working).

You can also make a version with vmalloc and I'll merge that, and then
you can look more into the DMA issues. That way the driver is merged,
even if it is perhaps not yet optimal, and you can address that part later.

OK, that sounds sensible, I will try that route. When using
videobuf2-vmalloc, what do I pass back for alloc_ctxs in queue_setup?

vmalloc doesn't need those, so you can just drop any alloc_ctx related code.

Regards,

	Hans