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 -- SENT FROM MY DEC VT50 TERMINAL
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