[PATCH v3] usbip: Don't submit special requests twice

[Simon Holesch]

Skip submitting URBs, when identical requests were already sent in
tweak_special_requests(). Instead call the completion handler directly
to return the result of the URB.

Even though submitting those requests twice should be harmless, there
are USB devices that react poorly to some duplicated requests.

One example is the ChipIdea controller implementation in U-Boot: The
second SET_CONFIURATION request makes U-Boot disable and re-enable all
endpoints. Re-enabling an endpoint in the ChipIdea controller, however,
was broken until U-Boot commit b272c8792502 ("usb: ci: Fix gadget
reinit").

Signed-off-by: Simon Holesch <simon@xxxxxxxxxx>
---

Changes in v3:
- handle errors in tweak_* routines: send URB if tweaking fails

Changes in v2:
- explain change in commit message

Thanks again for the feedback!

 drivers/usb/usbip/stub_rx.c | 73 +++++++++++++++++++++++--------------
 1 file changed, 46 insertions(+), 27 deletions(-)

diff --git a/drivers/usb/usbip/stub_rx.c b/drivers/usb/usbip/stub_rx.c
index fc01b31bbb87..76a6f46b8676 100644
--- a/drivers/usb/usbip/stub_rx.c
+++ b/drivers/usb/usbip/stub_rx.c
@@ -144,53 +144,62 @@ static int tweak_set_configuration_cmd(struct urb *urb)
 	if (err && err != -ENODEV)
 		dev_err(&sdev->udev->dev, "can't set config #%d, error %d\n",
 			config, err);
-	return 0;
+	return err;
 }
 
 static int tweak_reset_device_cmd(struct urb *urb)
 {
 	struct stub_priv *priv = (struct stub_priv *) urb->context;
 	struct stub_device *sdev = priv->sdev;
+	int err;
 
 	dev_info(&urb->dev->dev, "usb_queue_reset_device\n");
 
-	if (usb_lock_device_for_reset(sdev->udev, NULL) < 0) {
+	err = usb_lock_device_for_reset(sdev->udev, NULL)
+	if (err < 0) {
 		dev_err(&urb->dev->dev, "could not obtain lock to reset device\n");
-		return 0;
+		return err;
 	}
-	usb_reset_device(sdev->udev);
+	err = usb_reset_device(sdev->udev);
 	usb_unlock_device(sdev->udev);
 
-	return 0;
+	return err;
 }
 
 /*
  * clear_halt, set_interface, and set_configuration require special tricks.
+ * Returns 1 if request was tweaked, 0 otherwise.
  */
-static void tweak_special_requests(struct urb *urb)
+static int tweak_special_requests(struct urb *urb)
 {
+	int err;
+
 	if (!urb || !urb->setup_packet)
-		return;
+		return 0;
 
 	if (usb_pipetype(urb->pipe) != PIPE_CONTROL)
-		return;
+		return 0;
 
 	if (is_clear_halt_cmd(urb))
 		/* tweak clear_halt */
-		 tweak_clear_halt_cmd(urb);
+		err = tweak_clear_halt_cmd(urb);
 
 	else if (is_set_interface_cmd(urb))
 		/* tweak set_interface */
-		tweak_set_interface_cmd(urb);
+		err = tweak_set_interface_cmd(urb);
 
 	else if (is_set_configuration_cmd(urb))
 		/* tweak set_configuration */
-		tweak_set_configuration_cmd(urb);
+		err = tweak_set_configuration_cmd(urb);
 
 	else if (is_reset_device_cmd(urb))
-		tweak_reset_device_cmd(urb);
-	else
+		err = tweak_reset_device_cmd(urb);
+	else {
 		usbip_dbg_stub_rx("no need to tweak\n");
+		return 0;
+	}
+
+	return !err;
 }
 
 /*
@@ -468,6 +477,7 @@ static void stub_recv_cmd_submit(struct stub_device *sdev,
 	int support_sg = 1;
 	int np = 0;
 	int ret, i;
+	int is_tweaked;
 
 	if (pipe == -1)
 		return;
@@ -580,8 +590,7 @@ static void stub_recv_cmd_submit(struct stub_device *sdev,
 		priv->urbs[i]->pipe = pipe;
 		priv->urbs[i]->complete = stub_complete;
 
-		/* no need to submit an intercepted request, but harmless? */
-		tweak_special_requests(priv->urbs[i]);
+		is_tweaked = tweak_special_requests(priv->urbs[i]);
 
 		masking_bogus_flags(priv->urbs[i]);
 	}
@@ -594,22 +603,32 @@ static void stub_recv_cmd_submit(struct stub_device *sdev,
 
 	/* urb is now ready to submit */
 	for (i = 0; i < priv->num_urbs; i++) {
-		ret = usb_submit_urb(priv->urbs[i], GFP_KERNEL);
+		if (!is_tweaked) {
+			ret = usb_submit_urb(priv->urbs[i], GFP_KERNEL);
 
-		if (ret == 0)
-			usbip_dbg_stub_rx("submit urb ok, seqnum %u\n",
-					pdu->base.seqnum);
-		else {
-			dev_err(&udev->dev, "submit_urb error, %d\n", ret);
-			usbip_dump_header(pdu);
-			usbip_dump_urb(priv->urbs[i]);
+			if (ret == 0)
+				usbip_dbg_stub_rx("submit urb ok, seqnum %u\n",
+						pdu->base.seqnum);
+			else {
+				dev_err(&udev->dev, "submit_urb error, %d\n", ret);
+				usbip_dump_header(pdu);
+				usbip_dump_urb(priv->urbs[i]);
 
+				/*
+				 * Pessimistic.
+				 * This connection will be discarded.
+				 */
+				usbip_event_add(ud, SDEV_EVENT_ERROR_SUBMIT);
+				break;
+			}
+		} else {
 			/*
-			 * Pessimistic.
-			 * This connection will be discarded.
+			 * An identical URB was already submitted in
+			 * tweak_special_requests(). Skip submitting this URB to not
+			 * duplicate the request.
 			 */
-			usbip_event_add(ud, SDEV_EVENT_ERROR_SUBMIT);
-			break;
+			priv->urbs[i]->status = 0;
+			stub_complete(priv->urbs[i]);
 		}
 	}
 
-- 
2.43.0