[PATCH v2 1/5] usb: gadget: dummy_hcd: emulate sending zlp in packet logic

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currently, when a zlp flag is set and an urb/usb_request
buffer is filled without a short packet, transfer() leaves
its status at -EINPROGRESS and does not rescan for short
packet.

In a scenario where ep.maxpacket bytes are copied,
URB_ZERO_PACKET is set, urb buffer is filled and usb_request
buffer is not, transfer() returns with an urb with
-EINPROGRESS status, which dummy_hcd treats as incomplete
transfer.

Check for zlp and rescan appropriately.

Signed-off-by: Igor Kotrasinski <i.kotrasinsk@xxxxxxxxxxx>
---
 drivers/usb/gadget/udc/dummy_hcd.c | 24 ++++++++++++++++--------
 1 file changed, 16 insertions(+), 8 deletions(-)

diff --git a/drivers/usb/gadget/udc/dummy_hcd.c b/drivers/usb/gadget/udc/dummy_hcd.c
index 181112c..59be03e 100644
--- a/drivers/usb/gadget/udc/dummy_hcd.c
+++ b/drivers/usb/gadget/udc/dummy_hcd.c
@@ -1364,15 +1364,23 @@ top:
 					req->req.status = 0;
 			}
 
-		/* many requests terminate without a short packet */
+		/* many requests terminate without a short packet.
+		 * send a zlp if demanded by flags.
+		 */
 		} else {
-			if (req->req.length == req->req.actual
-					&& !req->req.zero)
-				req->req.status = 0;
-			if (urb->transfer_buffer_length == urb->actual_length
-					&& !(urb->transfer_flags
-						& URB_ZERO_PACKET))
-				*status = 0;
+			if (req->req.length == req->req.actual) {
+				if (req->req.zero && to_host)
+					rescan = 1;
+				else
+					req->req.status = 0;
+			}
+			if (urb->transfer_buffer_length == urb->actual_length) {
+				if (urb->transfer_flags & URB_ZERO_PACKET &&
+				    !to_host)
+					rescan = 1;
+				else
+					*status = 0;
+			}
 		}
 
 		/* device side completion --> continuable */
-- 
1.9.1

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