[nrf frtomtree] Tests: Bluetooth: Add MTU exchange procedure in testlib

Add `bt_testlib_att_exchange_mtu` function to simplify the procedure.

Signed-off-by: Théo Battrel <[email protected]>
(cherry picked from commit e3cf59b)

Author: theob-pro

tests/bluetooth/common/testlib/CMakeLists.txt

@@ -15,6 +15,7 @@ target_include_directories(testlib PUBLIC
 
 target_sources(testlib PRIVATE
   src/adv.c
+  src/att.c
   src/att_read.c
   src/att_write.c
   src/conn_ref.c

tests/bluetooth/common/testlib/include/testlib/att.h

@@ -0,0 +1,15 @@
+/*
+ * Copyright (c) 2025 Nordic Semiconductor ASA
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#ifndef ZEPHYR_TESTS_BLUETOOTH_COMMON_TESTLIB_INCLUDE_TESTLIB_ATT_H_
+#define ZEPHYR_TESTS_BLUETOOTH_COMMON_TESTLIB_INCLUDE_TESTLIB_ATT_H_
+
+#include <stdint.h>
+#include <zephyr/bluetooth/conn.h>
+
+int bt_testlib_att_exchange_mtu(struct bt_conn *conn);
+
+#endif /* ZEPHYR_TESTS_BLUETOOTH_COMMON_TESTLIB_INCLUDE_TESTLIB_ATT_H_ */

tests/bluetooth/common/testlib/src/att.c

@@ -0,0 +1,69 @@
+/*
+ * Copyright (c) 2025 Nordic Semiconductor ASA
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <zephyr/kernel.h>
+
+#include <zephyr/bluetooth/bluetooth.h>
+#include <zephyr/bluetooth/conn.h>
+#include <zephyr/bluetooth/gatt.h>
+#include <zephyr/bluetooth/att.h>
+
+#include <zephyr/logging/log.h>
+
+LOG_MODULE_REGISTER(bt_testlib_att, LOG_LEVEL_DBG);
+
+static uint8_t exchange_mtu_err;
+static K_MUTEX_DEFINE(exchange_mtu_lock);
+static K_CONDVAR_DEFINE(exchange_mtu_done);
+
+static void bt_testlib_att_exchange_mtu_cb(struct bt_conn *conn, uint8_t err,
+					   struct bt_gatt_exchange_params *params)
+{
+	char addr[BT_ADDR_LE_STR_LEN];
+
+	k_mutex_lock(&exchange_mtu_lock, K_FOREVER);
+
+	bt_addr_le_to_str(bt_conn_get_dst(conn), addr, sizeof(addr));
+
+	LOG_DBG("MTU exchange %s (%s)", err == 0U ? "successful" : "failed", addr);
+
+	exchange_mtu_err = err;
+
+	k_condvar_signal(&exchange_mtu_done);
+
+	k_mutex_unlock(&exchange_mtu_lock);
+}
+
+int bt_testlib_att_exchange_mtu(struct bt_conn *conn)
+{
+	int err;
+	struct bt_gatt_exchange_params exchange_mtu_params;
+
+	__ASSERT_NO_MSG(conn != NULL);
+
+	k_mutex_lock(&exchange_mtu_lock, K_FOREVER);
+
+	exchange_mtu_err = 0;
+
+	exchange_mtu_params.func = bt_testlib_att_exchange_mtu_cb;
+
+	err = bt_gatt_exchange_mtu(conn, &exchange_mtu_params);
+	if (err != 0) {
+		LOG_ERR("Failed to exchange MTU (err %d)", err);
+
+		k_mutex_unlock(&exchange_mtu_lock);
+
+		return err;
+	}
+
+	k_condvar_wait(&exchange_mtu_done, &exchange_mtu_lock, K_FOREVER);
+
+	err = exchange_mtu_err;
+
+	k_mutex_unlock(&exchange_mtu_lock);
+
+	return err;
+}