lorawan: services: add Class C session handling

The new functions are required for Multicast Class C session setup.

Signed-off-by: Martin Jäger <martin@libre.solar>

subsys/lorawan/services/clock_sync.c

@@ -174,6 +174,12 @@ static int clock_sync_app_time_req(void)
 	uint8_t tx_pos = 0;
 	uint8_t tx_buf[6];
 
+	if (lorawan_services_class_c_active() > 0) {
+		/* avoid disturbing the session and causing potential package loss */
+		LOG_DBG("AppTimeReq not sent because of active class C session");
+		return -EBUSY;
+	}
+
 	tx_buf[tx_pos++] = CLOCK_SYNC_CMD_APP_TIME;
 	tx_pos += clock_sync_serialize_device_time(tx_buf + tx_pos,
 						       sizeof(tx_buf) - tx_pos);

subsys/lorawan/services/lorawan_services.c

@@ -35,6 +35,10 @@ static struct k_work_q services_workq;
 
 static struct k_work_delayable uplink_work;
 
+/* Number of active class C sessions and mutex to protect access to session info */
+static uint8_t active_class_c_sessions;
+static struct k_mutex session_mutex;
+
 /* single-linked list (with pointers) and array for implementation of priority queue */
 static struct service_uplink_msg messages[10];
 static sys_slist_t msg_list;
@@ -160,6 +164,56 @@ int lorawan_services_reschedule_work(struct k_work_delayable *dwork, k_timeout_t
 	return k_work_reschedule_for_queue(&services_workq, dwork, delay);
 }
 
+int lorawan_services_class_c_start(void)
+{
+	int ret;
+
+	k_mutex_lock(&session_mutex, K_FOREVER);
+
+	if (active_class_c_sessions == 0) {
+		ret = lorawan_set_class(LORAWAN_CLASS_C);
+		if (ret == 0) {
+			LOG_DBG("Switched to class C");
+			active_class_c_sessions++;
+			ret = active_class_c_sessions;
+		}
+	} else {
+		active_class_c_sessions++;
+		ret = active_class_c_sessions;
+	}
+
+	k_mutex_unlock(&session_mutex);
+
+	return ret;
+}
+
+int lorawan_services_class_c_stop(void)
+{
+	int ret = 0;
+
+	k_mutex_lock(&session_mutex, K_FOREVER);
+
+	if (active_class_c_sessions == 1) {
+		ret = lorawan_set_class(LORAWAN_CLASS_A);
+		if (ret == 0) {
+			LOG_DBG("Reverted to class A");
+			active_class_c_sessions--;
+		}
+	} else if (active_class_c_sessions > 1) {
+		active_class_c_sessions--;
+		ret = active_class_c_sessions;
+	}
+
+	k_mutex_unlock(&session_mutex);
+
+	return ret;
+}
+
+int lorawan_services_class_c_active(void)
+{
+	return active_class_c_sessions;
+}
+
 static int lorawan_services_init(void)
 {
 
@@ -173,6 +227,8 @@ static int lorawan_services_init(void)
 
 	k_work_init_delayable(&uplink_work, uplink_handler);
 
+	k_mutex_init(&session_mutex);
+
 	k_thread_name_set(&services_workq.thread, "lorawan_services");
 
 	return 0;

subsys/lorawan/services/lorawan_services.h

@@ -58,4 +58,34 @@ int lorawan_services_schedule_uplink(uint8_t port, uint8_t *data, uint8_t len, u
 int lorawan_services_reschedule_work(struct k_work_delayable *dwork, k_timeout_t delay);
 
 
+/**
+ * @brief Start a class C session
+ *
+ * If there is already an ongoing class C session, only the internal counter of
+ * active sessions is incremented.
+ *
+ * @returns Number of active sessions if successful or negative errno otherwise.
+ */
+int lorawan_services_class_c_start(void);
+
+/**
+ * @brief Stop class C session and revert to class A
+ *
+ * If there is more than one class C session ongoing, only the internal counter
+ * of active sessions is decremented.
+ *
+ * @returns Number of active sessions if successful or negative errno otherwise.
+ */
+int lorawan_services_class_c_stop(void);
+
+/**
+ * @brief Retrieve number of active sessions
+ *
+ * Can be used to determine if sessions are ongoing and avoid disturbing an
+ * ongoing session by sending out unnecessary messages.
+ *
+ * @returns Number of active class C sessions.
+ */
+int lorawan_services_class_c_active(void);
+
 #endif /* ZEPHYR_SUBSYS_LORAWAN_SERVICES_LORAWAN_SERVICES_H_ */