On Wed, 12 May 2010 tom.leiming@xxxxxxxxx wrote:
> From: Ming Lei <tom.leiming@xxxxxxxxx>
>
> This patch only checks URB_SETUP_MAP_* flag for URB of control endpoint.
>
> Since control transfer is very few compared with other kind of transfer,
> the fix decreases 2 compares to 1 compares for non-control transfer and
> is more efficient.
>
> It does make sense for unmap_urb_for_dma() often runs in hardirq context.
>
> Signed-off-by: Ming Lei <tom.leiming@xxxxxxxxx>
> ---
> drivers/usb/core/hcd.c | 24 +++++++++++++-----------
> 1 files changed, 13 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
> index 12742f1..df1f9af 100644
> --- a/drivers/usb/core/hcd.c
> +++ b/drivers/usb/core/hcd.c
> @@ -1263,17 +1263,19 @@ static void unmap_urb_for_dma(struct usb_hcd *hcd, struct urb *urb)
> {
> enum dma_data_direction dir;
>
> - if (urb->transfer_flags & URB_SETUP_MAP_SINGLE)
> - dma_unmap_single(hcd->self.controller,
> - urb->setup_dma,
> - sizeof(struct usb_ctrlrequest),
> - DMA_TO_DEVICE);
> - else if (urb->transfer_flags & URB_SETUP_MAP_LOCAL)
> - hcd_free_coherent(urb->dev->bus,
> - &urb->setup_dma,
> - (void **) &urb->setup_packet,
> - sizeof(struct usb_ctrlrequest),
> - DMA_TO_DEVICE);
> + if (usb_endpoint_xfer_control(&urb->ep->desc)) {
If you really want to do this sort of micro-optimization, it would be
better to test
if (urb->transfer_flags &
(URB_SETUP_MAP_SINGLE | URB_SETUP_MAP_LOCAL))
because urb->transfer_flags gets reused immediately.
Alan Stern
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