X-Git-Url: http://git.lttng.org./?a=blobdiff_plain;f=include%2Flttng%2Fust-events.h;h=d9e15d34a72f8a0cfedbac33344734dfe4da740b;hb=6d35572a24bb6d7b1d21d0bf88dc49e5bfac5e20;hp=7abca292729671151cf1fb50d821f49db706e6ea;hpb=808edfc82d5518fb99f5fdc781c74dcf61d8e770;p=lttng-ust.git

diff --git a/include/lttng/ust-events.h b/include/lttng/ust-events.h
index 7abca292..d9e15d34 100644
--- a/include/lttng/ust-events.h
+++ b/include/lttng/ust-events.h
@@ -286,7 +286,6 @@ struct lttng_event_desc {
 	union {
 		struct {
 			const char **model_emf_uri;
-			void (*event_notifier_callback)(void);
 		} ext;
 		char padding[LTTNG_UST_EVENT_DESC_PADDING];
 	} u;
@@ -355,39 +354,90 @@ enum lttng_ust_event_type {
 	LTTNG_UST_EVENT_TYPE_NOTIFIER = 1,
 };
 
+/*
+ * IMPORTANT: this structure is part of the ABI between the probe and
+ * UST. Fields need to be only added at the end, never reordered, never
+ * removed.
+ *
+ * struct lttng_ust_event_common is the common ancestor of the various
+ * public event actions. Inheritance is done by composition: The parent
+ * has a pointer to its child, and the child has a pointer to its
+ * parent. Inheritance of those public structures is done by composition
+ * to ensure both parent and child structures can be extended.
+ *
+ * The field @struct_size should be used to determine the size of the
+ * structure. It should be queried before using additional fields added
+ * at the end of the structure.
+ */
 struct lttng_ust_event_common {
 	uint32_t struct_size;				/* Size of this structure. */
 	struct lttng_ust_event_common_private *priv;	/* Private event interface */
 
 	enum lttng_ust_event_type type;
+	void *child;					/* Pointer to child, for inheritance by aggregation. */
+
 	int enabled;
 	int has_enablers_without_bytecode;
 	/* list of struct lttng_bytecode_runtime, sorted by seqnum */
 	struct cds_list_head filter_bytecode_runtime_head;
+
+	/* End of base ABI. Fields below should be used after checking struct_size. */
 };
 
 struct lttng_ust_event_recorder_private;
 
+/*
+ * IMPORTANT: this structure is part of the ABI between the probe and
+ * UST. Fields need to be only added at the end, never reordered, never
+ * removed.
+ *
+ * struct lttng_ust_event_recorder is the action for recording events
+ * into a ring buffer. It inherits from struct lttng_ust_event_common
+ * by composition to ensure both parent and child structure are
+ * extensible.
+ *
+ * The field @struct_size should be used to determine the size of the
+ * structure. It should be queried before using additional fields added
+ * at the end of the structure.
+ */
 struct lttng_ust_event_recorder {
 	uint32_t struct_size;				/* Size of this structure. */
-	struct lttng_ust_event_common *parent;
+	struct lttng_ust_event_common *parent;		/* Inheritance by aggregation. */
 	struct lttng_ust_event_recorder_private *priv;	/* Private event record interface */
 
 	unsigned int id;
 	struct lttng_channel *chan;
 	struct lttng_ctx *ctx;
+
+	/* End of base ABI. Fields below should be used after checking struct_size. */
 };
 
 struct lttng_ust_event_notifier_private;
 
+/*
+ * IMPORTANT: this structure is part of the ABI between the probe and
+ * UST. Fields need to be only added at the end, never reordered, never
+ * removed.
+ *
+ * struct lttng_ust_event_notifier is the action for sending
+ * notifications. It inherits from struct lttng_ust_event_common
+ * by composition to ensure both parent and child structure are
+ * extensible.
+ *
+ * The field @struct_size should be used to determine the size of the
+ * structure. It should be queried before using additional fields added
+ * at the end of the structure.
+ */
 struct lttng_ust_event_notifier {
 	uint32_t struct_size;				/* Size of this structure. */
-	struct lttng_ust_event_common *parent;
+	struct lttng_ust_event_common *parent;		/* Inheritance by aggregation. */
 	struct lttng_ust_event_notifier_private *priv;	/* Private event notifier interface */
 
 	void (*notification_send)(struct lttng_ust_event_notifier *event_notifier,
 		const char *stack_data);
 	struct cds_list_head capture_bytecode_runtime_head;
+
+	/* End of base ABI. Fields below should be used after checking struct_size. */
 };
 
 struct lttng_enum {
@@ -522,12 +572,18 @@ struct lttng_ust_session_private;
  * IMPORTANT: this structure is part of the ABI between the probe and
  * UST. Fields need to be only added at the end, never reordered, never
  * removed.
+ *
+ * The field @struct_size should be used to determine the size of the
+ * structure. It should be queried before using additional fields added
+ * at the end of the structure.
  */
 struct lttng_session {
 	uint32_t struct_size;			/* Size of this structure */
 	struct lttng_ust_session_private *priv;	/* Private session interface */
 
 	int active;				/* Is trace session active ? */
+
+	/* End of base ABI. Fields below should be used after checking struct_size. */
 };
 
 int lttng_probe_register(struct lttng_probe_desc *desc);