On Mon, 24 Feb 2014, Dan Williams 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.
>
> Cc: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
> Cc: Sarah Sharp <sarah.a.sharp@xxxxxxxxxxxxxxx>
> Cc: Mathias Nyman <mathias.nyman@xxxxxxxxxxxxxxx>
> Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
> ---
> drivers/usb/core/hcd.c | 3 +++
> 1 files changed, 3 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
> index 2518c3250750..ff7cd489f55d 100644
> --- 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");
> + return -EAGAIN;
> } else {
> urb->transfer_dma = dma_map_single(
> hcd->self.controller,
>
You mustn't just return -EAGAIN. Set ret = -EAGAIN and fall through to
the error-handling pathway.
Alan Stern
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