modem: modem_cellular: comms check result callback

Add a callback for the periodic script result so that applications have
a way of detecting dead links.

Signed-off-by: Jordan Yates <jordan@embeint.com>

Author: JordanYates

doc/releases/release-notes-4.3.rst

@@ -146,6 +146,10 @@ New APIs and options
 
     * :kconfig:option:`CONFIG_CPU_FREQ`
 
+* Cellular
+
+  * :c:enumerator:`CELLULAR_EVENT_MODEM_COMMS_CHECK_RESULT`
+
 * Crypto
 
   * :kconfig:option:`CONFIG_MBEDTLS_PSA_CRYPTO_BUILTIN_KEYS`

drivers/modem/modem_cellular.c

@@ -1391,11 +1391,15 @@ static void modem_cellular_carrier_on_event_handler(struct modem_cellular_data *
 {
 	const struct modem_cellular_config *config =
 		(const struct modem_cellular_config *)data->dev->config;
+	struct cellular_evt_modem_comms_check_result result;
 
 	switch (evt) {
 	case MODEM_CELLULAR_EVENT_SCRIPT_SUCCESS:
 	case MODEM_CELLULAR_EVENT_SCRIPT_FAILED:
+		result.success = evt == MODEM_CELLULAR_EVENT_SCRIPT_SUCCESS;
+
 		modem_cellular_start_timer(data, MODEM_CELLULAR_PERIODIC_SCRIPT_TIMEOUT);
+		modem_cellular_emit_event(data, CELLULAR_EVENT_MODEM_COMMS_CHECK_RESULT, &result);
 		break;
 
 	case MODEM_CELLULAR_EVENT_TIMEOUT:

include/zephyr/drivers/cellular.h

@@ -139,6 +139,8 @@ enum cellular_event {
 	CELLULAR_EVENT_MODEM_INFO_CHANGED = BIT(0),
 	/** Cellular network registration status changed */
 	CELLULAR_EVENT_REGISTRATION_STATUS_CHANGED = BIT(1),
+	/** Result of a communications link check to the modem */
+	CELLULAR_EVENT_MODEM_COMMS_CHECK_RESULT = BIT(2),
 };
 
 /* Opaque bit-mask large enough for all current & future events */
@@ -154,6 +156,11 @@ struct cellular_evt_registration_status {
 	enum cellular_registration_status status; /**< New registration status */
 };
 
+/** Payload for @ref CELLULAR_EVENT_MODEM_COMMS_CHECK_RESULT */
+struct cellular_evt_modem_comms_check_result {
+	bool success; /**< Communications to modem checked successfully */
+};
+
 /**
  * @brief Prototype for cellular event callbacks.
  *