/* This will discover all characteristics on the server, retrieving the handles of the writeable characteristics and subscribing to all notify and indicate characteristics.  */
int bt_tbs_client_read_call_state(struct bt_conn *conn, uint8_t inst_index)
/* This will discover all characteristics on the server, retrieving the handles of the writeable characteristics and subscribing to all notify and indicate characteristics.  */
int bt_tbs_client_read_call_state(struct bt_conn *conn, uint8_t inst_index)
{
	struct bt_tbs_instance *inst;
	if (conn == NULL) {
		return -ENOTCONN;
	}
	inst = tbs_inst_by_index(conn, inst_index);
	if (inst == NULL) {
		return -EINVAL;
	}
	if (inst->call_state_sub_params.value_handle == 0) {
		LOG_DBG("Handle not set");
		return -EINVAL;
	}
	return tbs_client_gatt_read(conn, inst, inst->call_state_sub_params.value_handle,
				    read_call_state_cb);
}