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SubjectRe: [PATCH v2 2/3] USB: ehci-tegra: fix inefficient copy of unaligned buffers
On Thu, 23 Apr 2015, Johan Hovold wrote:

> Make sure only to copy any actual data rather than the whole buffer,
> when releasing the temporary buffer used for unaligned non-isochronous
> transfers.
>
> Compile-tested only.
>
> Signed-off-by: Johan Hovold <johan@kernel.org>
> ---
> drivers/usb/host/ehci-tegra.c | 12 +++++++++---
> 1 file changed, 9 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/usb/host/ehci-tegra.c b/drivers/usb/host/ehci-tegra.c
> index ff9af29b4e9f..4031b372008e 100644
> --- a/drivers/usb/host/ehci-tegra.c
> +++ b/drivers/usb/host/ehci-tegra.c
> @@ -304,6 +304,7 @@ struct dma_aligned_buffer {
> static void free_dma_aligned_buffer(struct urb *urb)
> {
> struct dma_aligned_buffer *temp;
> + size_t length;
>
> if (!(urb->transfer_flags & URB_ALIGNED_TEMP_BUFFER))
> return;
> @@ -311,9 +312,14 @@ static void free_dma_aligned_buffer(struct urb *urb)
> temp = container_of(urb->transfer_buffer,
> struct dma_aligned_buffer, data);
>
> - if (usb_urb_dir_in(urb))
> - memcpy(temp->old_xfer_buffer, temp->data,
> - urb->transfer_buffer_length);
> + if (usb_urb_dir_in(urb)) {
> + if (usb_pipeisoc(urb->pipe))
> + length = urb->transfer_buffer_length;
> + else
> + length = urb->actual_length;
> +
> + memcpy(temp->old_xfer_buffer, temp->data, length);
> + }
> urb->transfer_buffer = temp->old_xfer_buffer;
> kfree(temp->kmalloc_ptr);

Acked-by: Alan Stern <stern@rowland.harvard.edu>



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