add gatt_get_mtu daemon command and GATT_MTU response event

include/btstack/hci_cmds.h

@@ -535,6 +535,13 @@ extern "C" {
 #define GATT_CHARACTERISTIC_DESCRIPTOR_QUERY_RESULT        0xA9
 #define GATT_LONG_CHARACTERISTIC_DESCRIPTOR_QUERY_RESULT   0xAA
 
+/** 
+ * @format H2
+ * @param handle
+ * @param MTU
+ */    
+#define GATT_MTU										   0xAB
+
 /** 
  * @format H2
  * @param handle

platforms/posix/src/daemon.c

@@ -564,6 +564,19 @@ static void send_gatt_query_complete(connection_t * connection, uint16_t handle,
     socket_connection_send_packet(connection, HCI_EVENT_PACKET, 0, event, sizeof(event));
 }
 
+static void send_gatt_mtu_event(connection_t * connection, uint16_t handle, uint16_t mtu){
+    uint8_t event[6];
+    int pos = 0;
+    event[pos++] = GATT_MTU;
+    event[pos++] = sizeof(event) - 2;
+    bt_store_16(event, pos, handle);
+    pos += 2;
+    bt_store_16(event, pos, mtu);
+    pos += 2;
+    hci_dump_packet(HCI_EVENT_PACKET, 0, event, sizeof(event));
+    socket_connection_send_packet(connection, HCI_EVENT_PACKET, 0, event, sizeof(event));
+}
+
 linked_list_gatt_client_helper_t * daemon_setup_gatt_client_request(connection_t *connection, uint8_t *packet) {
     hci_con_handle_t handle = READ_BT_16(packet, 3);    
     log_info("daemon_setup_gatt_client_request for handle 0x%02x", handle);
@@ -1063,6 +1076,11 @@ static int btstack_command_handler(connection_t *connection, uint8_t *packet, ui
             daemon_gatt_deserialize_characteristic(packet, 5, &characteristic);
             gatt_client_write_client_characteristic_configuration(gatt_client_id, gatt_helper->con_handle, &characteristic, configuration);
             break;
+        case GATT_GET_MTU:
+            handle = READ_BT_16(packet, 3);
+            gatt_client_get_mtu(handle, &mtu);
+            send_gatt_mtu_event(connection, handle, mtu);
+            break;
         }
 #endif
     default:

src/hci.h

@@ -230,6 +230,7 @@ extern "C" {
 #define GATT_WRITE_CHARACTERISTIC_DESCRIPTOR                     0X7F
 #define GATT_WRITE_LONG_CHARACTERISTIC_DESCRIPTOR                0X80
 #define GATT_WRITE_CLIENT_CHARACTERISTIC_CONFIGURATION           0X81
+#define GATT_GET_MTU                                             0x82
 
 // 
 #define IS_COMMAND(packet, command) (READ_BT_16(packet,0) == command.opcode)

src/hci_cmds.c

@@ -1400,3 +1400,10 @@ const hci_cmd_t gatt_write_long_characteristic_descriptor_cmd = {
 const hci_cmd_t gatt_write_client_characteristic_configuration_cmd = {
     OPCODE(OGF_BTSTACK, GATT_WRITE_CLIENT_CHARACTERISTIC_CONFIGURATION), "HY2"
 };
+
+/**
+ * @param handle
+ */
+const hci_cmd_t gatt_get_mtu = {
+    OPCODE(OGF_BTSTACK, GATT_GET_MTU), "H"
+};