usb: xhci: Add support for URB_ZERO_PACKET to bulk/sg transfers

This commit checks for the URB_ZERO_PACKET flag and creates an extra
zero-length td if the urb transfer length is a multiple of the endpoint's
max packet length.

Signed-off-by: Reyad Attiyat <reyad.attiyat@gmail.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
index 91fd328..6b0f4a4 100644
--- a/drivers/usb/host/xhci.c
+++ b/drivers/usb/host/xhci.c
@@ -1340,6 +1340,11 @@
 
 	if (usb_endpoint_xfer_isoc(&urb->ep->desc))
 		size = urb->number_of_packets;
+	else if (usb_endpoint_is_bulk_out(&urb->ep->desc) &&
+	    urb->transfer_buffer_length > 0 &&
+	    urb->transfer_flags & URB_ZERO_PACKET &&
+	    !(urb->transfer_buffer_length % usb_endpoint_maxp(&urb->ep->desc)))
+		size = 2;
 	else
 		size = 1;