On 02/04/15 12:34, Laurent Pinchart wrote: > Hi Florian, > > On Wednesday 04 February 2015 11:56:58 Florian Echtler wrote: >> On 04.02.2015 11:22, Hans Verkuil wrote: >>> On 02/04/15 11:08, Florian Echtler wrote: >>>> On 04.02.2015 09:08, Hans Verkuil wrote: >>>>> 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. >> >> That's what I assumed, however, I'm running into the same problem as >> with dma-sg when I switch to vmalloc...? > > I don't expect vmalloc to work, as you can't DMA to vmalloc memory directly > without any IOMMU in the general case (the allocated memory being physically > fragmented). > > dma-sg should work though, but you won't be able to use usb_bulk_msg(). You > need to create the URBs manually, set their sg and num_sgs fields and submit > them. So it works for other usb media drivers because they allocate memory using kmalloc (and presumably the usb core can DMA to that), and then memcpy it to the vmalloc-ed buffers? Anyway Florian, based on Laurent's explanation I think trying to make dma-sg work seems to be the best solution. And I've learned something new :-) Regards, Hans > >> I've sent a "proper" patch submission again, which has all the other >> issues from the previous submission fixed. I'm hoping you can maybe have >> a closer look and see if I'm doing anything subtly wrong which causes >> both vmalloc and dma-sg to fail while dma-contig works. > -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
