On Thu, 2014-05-08 at 19:25 +0300, Mathias Nyman wrote:
> Save someone else the debug cycles of figuring out why a driver's
> transfer request is failing or causing undefined system behavior.
> Buffers submitted for dma must come from GFP allocated / DMA-able
> memory.
>
> Return -EAGAIN matching the return value for dma_mapping_error() cases.
[]
> diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
[]
> @@ -1502,6 +1502,9 @@ int usb_hcd_map_urb_for_dma(struct usb_hcd *hcd, struct urb *urb,
> ret = -EAGAIN;
> else
> urb->transfer_flags |= URB_DMA_MAP_PAGE;
> + } else if (is_vmalloc_addr(urb->transfer_buffer)) {
> + WARN_ONCE(1, "transfer buffer not dma capable\n");
> + ret = -EAGAIN;
> } else {
> urb->transfer_dma = dma_map_single(
> hcd->self.controller,
Perhaps this could be #ifdef'd here or moved to and
tested in dma_map_single/dma_map_single_attr instead.
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