usb: ci_udc: detect queued requests on ep0

The flipping of ep0 between IN and OUT relies on ci_ep_queue() consuming
the current IN/OUT setting immediately. If this is deferred to a later
point when the req is pulled out of ci_req->queue, then the IN/OUT
setting may have been changed since the req was queued, and state will
get out of sync. This condition doesn't occur today, but could if bugs
were introduced later, and this error-check will save a lot of debugging
time.

Signed-off-by: Stephen Warren <swarren@nvidia.com>

1 files changed, 15 insertions, 0 deletions

diff --git a/drivers/usb/gadget/ci_udc.c b/drivers/usb/gadget/ci_udc.c
index 9cd003636a4..a68a85f84e7 100644
--- a/drivers/usb/gadget/ci_udc.c
+++ b/drivers/usb/gadget/ci_udc.c
@@ -397,6 +397,21 @@ static int ci_ep_queue(struct usb_ep *ep,
 	num = ci_ep->desc->bEndpointAddress & USB_ENDPOINT_NUMBER_MASK;
 	in = (ci_ep->desc->bEndpointAddress & USB_DIR_IN) != 0;
 
+	if (!num && ci_ep->req_primed) {
+		/*
+		 * The flipping of ep0 between IN and OUT relies on
+		 * ci_ep_queue consuming the current IN/OUT setting
+		 * immediately. If this is deferred to a later point when the
+		 * req is pulled out of ci_req->queue, then the IN/OUT setting
+		 * may have been changed since the req was queued, and state
+		 * will get out of sync. This condition doesn't occur today,
+		 * but could if bugs were introduced later, and this error
+		 * check will save a lot of debugging time.
+		 */
+		printf("%s: ep0 transaction already in progress\n", __func__);
+		return -EPROTO;
+	}
+
 	ret = ci_bounce(ci_req, in);
 	if (ret)
 		return ret;