rndis_host: Poll status channel before control channel

Some RNDIS devices don't respond on the control channel until polled
on the status channel.  In particular, this was reported to be the
case for the 2Wire HomePortal 1000SW.

This is roughly based on a patch by John Carr <john.carr@unrouted.co.uk>
which is reported to be needed for use with some Windows Mobile devices
and which is currently applied by Mandriva.
Reported-by: Mark Glassberg <vzeeaxwl@myfairpoint.net>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Tested-by: Mark Glassberg <vzeeaxwl@myfairpoint.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/usb/rndis_host.c

@@ -104,8 +104,10 @@ static void rndis_msg_indicate(struct usbnet *dev, struct rndis_indicate *msg,
 int rndis_command(struct usbnet *dev, struct rndis_msg_hdr *buf, int buflen)
 {
 	struct cdc_state	*info = (void *) &dev->data;
+	struct usb_cdc_notification notification;
 	int			master_ifnum;
 	int			retval;
+	int			partial;
 	unsigned		count;
 	__le32			rsp;
 	u32			xid = 0, msg_len, request_id;
@@ -133,13 +135,17 @@ int rndis_command(struct usbnet *dev, struct rndis_msg_hdr *buf, int buflen)
 	if (unlikely(retval < 0 || xid == 0))
 		return retval;
 
-	// FIXME Seems like some devices discard responses when
-	// we time out and cancel our "get response" requests...
-	// so, this is fragile.  Probably need to poll for status.
+	/* Some devices don't respond on the control channel until
+	 * polled on the status channel, so do that first. */
+	retval = usb_interrupt_msg(
+		dev->udev,
+		usb_rcvintpipe(dev->udev, dev->status->desc.bEndpointAddress),
+		&notification, sizeof(notification), &partial,
+		RNDIS_CONTROL_TIMEOUT_MS);
+	if (unlikely(retval < 0))
+		return retval;
 
-	/* ignore status endpoint, just poll the control channel;
-	 * the request probably completed immediately
-	 */
+	/* Poll the control channel; the request probably completed immediately */
 	rsp = buf->msg_type | RNDIS_MSG_COMPLETION;
 	for (count = 0; count < 10; count++) {
 		memset(buf, 0, CONTROL_BUFFER_SIZE);