diff --git a/components/bt/host/bluedroid/api/esp_gatt_common_api.c b/components/bt/host/bluedroid/api/esp_gatt_common_api.c
index 4504ffd1d..c7081c3bc 100644
--- a/components/bt/host/bluedroid/api/esp_gatt_common_api.c
+++ b/components/bt/host/bluedroid/api/esp_gatt_common_api.c
@@ -51,11 +51,21 @@ esp_err_t esp_ble_gatt_set_local_mtu (uint16_t mtu)
 #if (BLE_INCLUDED == TRUE)
 extern UINT16 L2CA_GetFreePktBufferNum_LE(void);
 
+/**
+ * @brief           This function is called to get currently sendable packets number on controller,
+ *                  the function is called only in BLE running core now.
+ *
+ * @return
+ *                  sendable packets number on controller
+ *
+ */
+ 
 uint16_t esp_ble_get_sendable_packets_num (void)
 {
     return L2CA_GetFreePktBufferNum_LE();
 }
 
+
 extern UINT16 L2CA_GetCurFreePktBufferNum_LE(UINT16 conn_id);
 uint16_t esp_ble_get_cur_sendable_packets_num (uint16_t connid)
 {