usb: device: Add usb_transfer_is_busy() function

Add usb_transfer_is_busy() function to check if there is ongoing
transfer.

Signed-off-by: Andrei Emeltchenko <andrei.emeltchenko@intel.com>

include/usb/usb_device.h

@@ -418,6 +418,16 @@ int usb_transfer_sync(u8_t ep, u8_t *data, size_t dlen, unsigned int flags);
  */
 void usb_cancel_transfer(u8_t ep);
 
+/**
+ * @brief Check that transfer is ongoing for the endpoint
+ *
+ * @param[in]  ep           Endpoint address corresponding to the one
+ *                          listed in the device configuration table
+ *
+ * @return true if transfer is ongoing, false otherwise.
+ */
+bool usb_transfer_is_busy(u8_t ep);
+
 /**
  * @brief Start the USB remote wakeup procedure
  *

subsys/usb/usb_device.c

@@ -1194,6 +1194,17 @@ static struct usb_transfer_data *usb_ep_get_transfer(u8_t ep)
 	return NULL;
 }
 
+bool usb_transfer_is_busy(u8_t ep)
+{
+	struct usb_transfer_data *trans = usb_ep_get_transfer(ep);
+
+	if (trans && trans->status == -EBUSY) {
+		return true;
+	}
+
+	return false;
+}
+
 static void usb_transfer_work(struct k_work *item)
 {
 	struct usb_transfer_data *trans;