usbdevice/core: use static message queue

Although currently the only message send to the queue is struct
udev_msg, in order to keep backward compacity and for extention in the
future, we set the size of message to 32.

components/drivers/usb/usbdevice/core/core.c

@@ -1274,7 +1274,7 @@ rt_err_t rt_usbd_set_config(udevice_t device, rt_uint8_t value)
     return RT_TRUE;
 }
 
-static struct rt_messagequeue *usb_mq;
+static struct rt_messagequeue usb_mq;
 
 /**
  * This function is the main entry of usb device thread, it is in charge of
@@ -1294,7 +1294,7 @@ static void rt_usbd_thread_entry(void* parameter)
         uep_t ep;
 
         /* receive message */
-        if(rt_mq_recv(usb_mq,
+        if(rt_mq_recv(&usb_mq,
                     &msg, sizeof(struct udev_msg),
                     RT_WAITING_FOREVER) != RT_EOK )
             continue;
@@ -1341,13 +1341,19 @@ rt_err_t rt_usbd_post_event(struct udev_msg* msg, rt_size_t size)
     RT_ASSERT(msg != RT_NULL);
 
     /* send message to usb message queue */
-    return rt_mq_send(usb_mq, (void*)msg, size);
+    return rt_mq_send(&usb_mq, (void*)msg, size);
 }
 
 
 ALIGN(RT_ALIGN_SIZE)
 static rt_uint8_t usb_thread_stack[RT_USBD_THREAD_STACK_SZ];
 static struct rt_thread usb_thread;
+#define USBD_MQ_MSG_SZ  32
+#define USBD_MQ_MAX_MSG 16
+/* internal of the message queue: every message is associated with a pointer,
+ * so in order to recveive USBD_MQ_MAX_MSG messages, we have to allocate more
+ * than USBD_MQ_MSG_SZ*USBD_MQ_MAX_MSG memery. */
+static rt_uint8_t usb_mq_pool[(USBD_MQ_MSG_SZ+sizeof(void*))*USBD_MQ_MAX_MSG];
 
 /**
  * This function will initialize usb device thread.
@@ -1360,7 +1366,8 @@ rt_err_t rt_usbd_core_init(void)
     rt_list_init(&device_list);
 
     /* create an usb message queue */
-    usb_mq = rt_mq_create("usbd", 32, 16, RT_IPC_FLAG_FIFO);
+    rt_mq_init(&usb_mq, "usbd", usb_mq_pool, USBD_MQ_MSG_SZ,
+            sizeof(usb_mq_pool), RT_IPC_FLAG_FIFO);
 
     /* init usb device thread */
     rt_thread_init(&usb_thread, "usbd", rt_usbd_thread_entry, RT_NULL,