add note for blocking tuh_configuration_set(), tuh_interface_set()

src/host/usbh.c

@@ -1030,7 +1030,15 @@ bool tuh_configuration_set(uint8_t daddr, uint8_t config_num,
     .user_data   = user_data
   };
 
-  return tuh_control_xfer(&xfer);
+  bool ret = tuh_control_xfer(&xfer);
+
+  // if blocking, user_data could be pointed to xfer_result
+  if ( !complete_cb && user_data )
+  {
+    *((xfer_result_t*) user_data) = xfer.result;
+  }
+
+  return ret;
 }
 
 bool tuh_interface_set(uint8_t daddr, uint8_t itf_num, uint8_t itf_alt,
@@ -1062,7 +1070,15 @@ bool tuh_interface_set(uint8_t daddr, uint8_t itf_num, uint8_t itf_alt,
     .user_data   = user_data
   };
 
-  return tuh_control_xfer(&xfer);
+  bool ret = tuh_control_xfer(&xfer);
+
+  // if blocking, user_data could be pointed to xfer_result
+  if ( !complete_cb && user_data )
+  {
+    *((xfer_result_t*) user_data) = xfer.result;
+  }
+
+  return ret;
 }
 
 //--------------------------------------------------------------------+

src/host/usbh.h

@@ -168,11 +168,13 @@ bool tuh_edpt_open(uint8_t dev_addr, tusb_desc_endpoint_t const * desc_ep);
 // Set Configuration (control transfer)
 // config_num = 0 will un-configure device. Note: config_num = config_descriptor_index + 1
 // true on success, false if there is on-going control transfer or incorrect parameters
+// if complete_cb == NULL i.e blocking, user_data should be pointed to xfer_reuslt_t*
 bool tuh_configuration_set(uint8_t daddr, uint8_t config_num,
                            tuh_xfer_cb_t complete_cb, uintptr_t user_data);
 
 // Set Interface (control transfer)
 // true on success, false if there is on-going control transfer or incorrect parameters
+// if complete_cb == NULL i.e blocking, user_data should be pointed to xfer_reuslt_t*
 bool tuh_interface_set(uint8_t daddr, uint8_t itf_num, uint8_t itf_alt,
                        tuh_xfer_cb_t complete_cb, uintptr_t user_data);