Re: [PATCH] add raw video support for Samsung SUR40 touchscreen

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

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.

> 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.

-- 
Regards,

Laurent Pinchart