lorawan: add link check support.

Add link check support, by adding:
- link check callback in response of LinkCheckAns.
- link check request function using LinkCheckReq.

Signed-off-by: Martin Durietz <martin.durietz@gmail.com>

doc/releases/release-notes-4.2.rst

@@ -172,6 +172,9 @@ New APIs and options
   * :c:func:`util_eq`
   * :c:func:`util_memeq`
 
+* LoRaWAN
+   * :c:func:`lorawan_request_link_check`
+
 New Boards
 **********
 

include/zephyr/lorawan/lorawan.h

@@ -217,6 +217,14 @@ typedef uint8_t (*lorawan_battery_level_cb_t)(void);
  */
 typedef void (*lorawan_dr_changed_cb_t)(enum lorawan_datarate dr);
 
+/**
+ * @brief Defines the link check answer handler function signature.
+ *
+ * @param demod_margin The demodulation margin in db.
+ * @param nb_gateways The number of gateways the device is connected to.
+ */
+typedef void (*lorawan_link_check_ans_cb_t)(uint8_t demod_margin, uint8_t nb_gateways);
+
 /**
  * @brief Defines the user's descriptor callback handler function signature.
  *
@@ -267,6 +275,14 @@ void lorawan_register_downlink_callback(struct lorawan_downlink_cb *cb);
  */
 void lorawan_register_dr_changed_callback(lorawan_dr_changed_cb_t cb);
 
+/**
+ * @brief Register a callback to be called when getting answer
+ * a to check link request.
+ *
+ * @param cb Pointer to link check ans callback
+ */
+void lorawan_register_link_check_ans_callback(lorawan_link_check_ans_cb_t cb);
+
 /**
  * @brief Join the LoRaWAN network
  *
@@ -426,6 +442,18 @@ int lorawan_request_device_time(bool force_request);
  */
 int lorawan_device_time_get(uint32_t *gps_time);
 
+/**
+ * @brief Request for link check according to LinkCheckReq MAC cmd
+ *
+ * Append MAC LinkCheckReq command. It will be processed on next send
+ * message or force sending empty message to request time immediately.
+ *
+ * @param force_request Immediately send an empty message to execute the request
+ *
+ * @return 0 if successful, negative errno otherwise
+ */
+int lorawan_request_link_check(bool force_request);
+
 #ifdef CONFIG_LORAWAN_APP_CLOCK_SYNC
 
 /**

subsys/lorawan/lorawan.c

@@ -93,6 +93,7 @@ static enum lorawan_channels_mask_size region_channels_mask_size =
 
 static lorawan_battery_level_cb_t battery_level_cb;
 static lorawan_dr_changed_cb_t dr_changed_cb;
+static lorawan_link_check_ans_cb_t link_check_cb;
 
 /* implementation required by the soft-se (software secure element) */
 void BoardGetUniqueId(uint8_t *id)
@@ -213,8 +214,10 @@ static void mlme_confirm_handler(MlmeConfirm_t *mlme_confirm)
 		LOG_INF("Joined network! DevAddr: %08x", mib_req.Param.DevAddr);
 		break;
 	case MLME_LINK_CHECK:
-		/* Not implemented */
-		LOG_INF("Link check not implemented yet!");
+		if (link_check_cb != NULL) {
+			link_check_cb(mlme_confirm->DemodMargin, mlme_confirm->NbGateways);
+		}
+		LOG_INF("Link check done");
 		break;
 	case MLME_DEVICE_TIME:
 		LOG_INF("DevTimeReq done");
@@ -399,6 +402,27 @@ int lorawan_set_region(enum lorawan_region region)
 	return 0;
 }
 
+int lorawan_request_link_check(bool force_request)
+{
+	int ret = 0;
+	LoRaMacStatus_t status;
+	MlmeReq_t mlme_req;
+
+	mlme_req.Type = MLME_LINK_CHECK;
+	status = LoRaMacMlmeRequest(&mlme_req);
+	if (status != LORAMAC_STATUS_OK) {
+		LOG_ERR("LinkCheckReq failed: %s", lorawan_status2str(status));
+		ret = lorawan_status2errno(status);
+		return ret;
+	}
+
+	if (force_request) {
+		ret = lorawan_send(0U, "", 0U, LORAWAN_MSG_UNCONFIRMED);
+	}
+
+	return ret;
+}
+
 int lorawan_request_device_time(bool force_request)
 {
 	int ret = 0;
@@ -732,6 +756,11 @@ void lorawan_register_dr_changed_callback(lorawan_dr_changed_cb_t cb)
 	dr_changed_cb = cb;
 }
 
+void lorawan_register_link_check_ans_callback(lorawan_link_check_ans_cb_t cb)
+{
+	link_check_cb = cb;
+}
+
 int lorawan_start(void)
 {
 	LoRaMacStatus_t status;