USB: introduce usb_device_no_sg_constraint() helper
Some host controllers(such as xHCI) can support building
packet from discontinuous buffers, so introduce one flag
and helper for this kind of host controllers, then the
feature can help some applications(such as usbnet) by
supporting arbitrary length of sg buffers.
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Ming Lei <ming.lei@canonical.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/usb/core/urb.c b/drivers/usb/core/urb.c
index 4e7a311..c12bc79 100644
--- a/drivers/usb/core/urb.c
+++ b/drivers/usb/core/urb.c
@@ -416,7 +416,8 @@
urb->iso_frame_desc[n].status = -EXDEV;
urb->iso_frame_desc[n].actual_length = 0;
}
- } else if (dev->speed != USB_SPEED_WIRELESS && urb->num_sgs) {
+ } else if (urb->num_sgs && !urb->dev->bus->no_sg_constraint &&
+ dev->speed != USB_SPEED_WIRELESS) {
struct scatterlist *sg;
int i;