zbus: optional publishing statistics

Add optional statistics around the channel publishing action. Store the
time a channel was last published to, and a total publish count.

This information can be used to determine how old a given channels data
is, and an average channel publishing frequency.

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

include/zephyr/zbus/zbus.h

@@ -62,6 +62,13 @@ struct zbus_channel_data {
 	 */
 	struct net_buf_pool *msg_subscriber_pool;
 #endif /* ZBUS_MSG_SUBSCRIBER_NET_BUF_POOL_ISOLATION */
+
+#if defined(CONFIG_ZBUS_CHANNEL_PUBLISH_STATS) || defined(__DOXYGEN__)
+	/** Kernel timestamp of the last publish action on this channel */
+	k_ticks_t publish_timestamp;
+	/** Number of times data has been published to this channel */
+	uint32_t publish_count;
+#endif /* CONFIG_ZBUS_CHANNEL_PUBLISH_STATS */
 };
 
 /**
@@ -722,6 +729,89 @@ static inline void zbus_chan_set_msg_sub_pool(const struct zbus_channel *chan,
 
 #endif /* ZBUS_MSG_SUBSCRIBER_NET_BUF_POOL_ISOLATION */
 
+#if defined(CONFIG_ZBUS_CHANNEL_PUBLISH_STATS) || defined(__DOXYGEN__)
+
+/**
+ * @brief Update the publishing statistics for a channel
+ *
+ * This function updates the publishing statistics for the @ref zbus_chan_claim ->
+ * @ref zbus_chan_finish workflow, which cannot automatically determine whether
+ * new data has been published or not.
+ *
+ * @warning This function must only be used directly for already locked channels.
+ *
+ * @param chan The channel's reference.
+ */
+static inline void zbus_chan_pub_stats_update(const struct zbus_channel *chan)
+{
+	__ASSERT(chan != NULL, "chan is required");
+
+	chan->data->publish_timestamp = k_uptime_ticks();
+	chan->data->publish_count += 1;
+}
+
+/**
+ * @brief Get the time a channel was last published to.
+ *
+ * @note Will return 0 if channel has not yet been published to.
+ *
+ * @param chan The channel's reference.
+ *
+ * @return The kernel timestamp of the last publishing action.
+ */
+static inline k_ticks_t zbus_chan_pub_stats_last_time(const struct zbus_channel *chan)
+{
+	__ASSERT(chan != NULL, "chan is required");
+
+	return chan->data->publish_timestamp;
+}
+
+/**
+ * @brief Get the number of times a channel has been published to.
+ *
+ * @note Will return 0 if channel has not yet been published to.
+ *
+ * @param chan The channel's reference.
+ *
+ * @return The number of times a channel has been published to.
+ */
+static inline uint32_t zbus_chan_pub_stats_count(const struct zbus_channel *chan)
+{
+	__ASSERT(chan != NULL, "chan is required");
+
+	return chan->data->publish_count;
+}
+
+/**
+ * @brief Get the average period between publishes to a channel.
+ *
+ * @note Will return 0 if channel has not yet been published to.
+ *
+ * @param chan The channel's reference.
+ *
+ * @return Average duration in milliseconds between publishes.
+ */
+static inline uint32_t zbus_chan_pub_stats_avg_period(const struct zbus_channel *chan)
+{
+	__ASSERT(chan != NULL, "chan is required");
+
+	/* Not yet published, period = 0ms */
+	if (chan->data->publish_count == 0) {
+		return 0;
+	}
+	/* Average period across application runtime */
+	return k_uptime_get() / chan->data->publish_count;
+}
+
+#else
+
+static inline void zbus_chan_pub_stats_update(const struct zbus_channel *chan)
+{
+	(void)chan;
+}
+
+#endif /* CONFIG_ZBUS_CHANNEL_PUBLISH_STATS */
+
 #if defined(CONFIG_ZBUS_RUNTIME_OBSERVERS) || defined(__DOXYGEN__)
 
 /**

subsys/zbus/Kconfig

@@ -19,6 +19,9 @@ config ZBUS_CHANNEL_NAME
 config ZBUS_OBSERVER_NAME
 	bool "Observer name field"
 
+config ZBUS_CHANNEL_PUBLISH_STATS
+	bool "Channel publishing statistics (Timestamp and count)"
+
 config ZBUS_MSG_SUBSCRIBER
 	select NET_BUF
 	bool "Message subscribers will receive all messages in sequence."

subsys/zbus/zbus.c

@@ -355,6 +355,11 @@ int zbus_chan_pub(const struct zbus_channel *chan, const void *msg, k_timeout_t
 		return err;
 	}
 
+#if defined(CONFIG_ZBUS_CHANNEL_PUBLISH_STATS)
+	chan->data->publish_timestamp = k_uptime_ticks();
+	chan->data->publish_count += 1;
+#endif /* CONFIG_ZBUS_CHANNEL_PUBLISH_STATS */
+
 	memcpy(chan->message, msg, chan->message_size);
 
 	err = _zbus_vded_exec(chan, end_time);