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

[Florian Echtler <floe@butterbrot.org>]

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Sorry to bring this up again, but would it be acceptable to simply use
dma-contig after all? Since the GFP_DMA flag is gone, this shouldn't be
too big of an issue IMHO, and I was kind of hoping the patch could still
be part of 3.20.

Best, Florian

On 29.01.2015 22:35, Florian Echtler wrote:
> I'm still having a couple of issues sorting out the correct way to
> provide DMA access for my driver. I've integrated most of your
> suggestions, but I still can't switch from dma-contig to dma-sg.
> As far as I understood it, there is no further initialization required
> besides using vb2_dma_sg_memops, vb2_dma_sg_init_ctx and
> vb2_dma_sg_cleanup_ctx instead of the respective -contig- calls, correct?
> However, as soon as I swap the relevant function calls, the video image
> stays black and in dmesg, I get the following warning:
>
> Call Trace:
> [<ffffffff817c4584>] dump_stack+0x45/0x57
> [<ffffffff81076df7>] warn_slowpath_common+0x97/0xe0
> [<ffffffff81076ef6>] warn_slowpath_fmt+0x46/0x50
> [<ffffffff815aff0b>] usb_hcd_map_urb_for_dma+0x4eb/0x500
> [<ffffffff817d03b4>] ? schedule_timeout+0x124/0x210
> [<ffffffff815b0bd5>] usb_hcd_submit_urb+0x135/0x1c0
> [<ffffffff815b20a6>] usb_submit_urb.part.8+0x1f6/0x580
> [<ffffffff811bb542>] ? vmap_pud_range+0x122/0x1c0
> [<ffffffff815b2465>] usb_submit_urb+0x35/0x80
> [<ffffffff815b339a>] usb_start_wait_urb+0x6a/0x170
> [<ffffffff815b1cce>] ? usb_alloc_urb+0x1e/0x50
> [<ffffffff815b1cce>] ? usb_alloc_urb+0x1e/0x50
> [<ffffffff815b3570>] usb_bulk_msg+0xd0/0x1a0
> [<ffffffffc059a841>] sur40_poll+0x561/0x5e0 [sur40]
>
> Moreover, I'm getting the following test failure from v4l2-compliance:
> 
> Streaming ioctls:
> 	test read/write: OK
> 	test MMAP: OK
> 		fail: v4l2-test-buffers.cpp(951): buf.qbuf(node)
> 		fail: v4l2-test-buffers.cpp(994): setupUserPtr(node, q)
> 	test USERPTR: FAIL
> 	test DMABUF: Cannot test, specify --expbuf-device
> 
> Total: 45, Succeeded: 44, Failed: 1, Warnings: 0


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