[PATCH v2 2/4] libtracefs: New API for getting dynamic event

["Tzvetomir Stoyanov (VMware)" <tz.stoyanov@gmail.com>]

A new API is proposed, to get tep event describing given dynamic event:

	tracefs_dynevent_get_event()

The API detects any newly created or removed dynamic events.

Signed-off-by: Tzvetomir Stoyanov (VMware) <tz.stoyanov@gmail.com>
---
 Documentation/libtracefs-dynevents.txt | 13 ++++++++--
 include/tracefs.h                      |  2 ++
 src/tracefs-dynevents.c                | 33 ++++++++++++++++++++++++++
 3 files changed, 46 insertions(+), 2 deletions(-)

diff --git a/Documentation/libtracefs-dynevents.txt b/Documentation/libtracefs-dynevents.txt
index a374651..bec31f1 100644
--- a/Documentation/libtracefs-dynevents.txt
+++ b/Documentation/libtracefs-dynevents.txt
@@ -4,8 +4,8 @@ libtracefs(3)
 NAME
 ----
 tracefs_dynevent_create, tracefs_dynevent_destroy, tracefs_dynevent_destroy_all,
-tracefs_dynevent_free, tracefs_dynevent_list_free, tracefs_dynevent_get_all, tracefs_dynevent_info -
-Create, destroy, free and get dynamic events.
+tracefs_dynevent_free, tracefs_dynevent_list_free, tracefs_dynevent_get_all, tracefs_dynevent_info,
+tracefs_dynevent_get_event - Create, destroy, free and get dynamic events.
 
 SYNOPSIS
 --------
@@ -23,6 +23,7 @@ void *tracefs_dynevent_list_free*(struct tracefs_dynevent pass:[*]pass:[*]_event
 struct tracefs_dynevent pass:[*]*tracefs_dynevent_get*(enum tracefs_dynevent_type _type_, const char pass:[*]_system_, const char pass:[*]_event_);
 struct tracefs_dynevent pass:[*]pass:[*]*tracefs_dynevent_get_all*(unsigned int _types_, const char pass:[*]_system_);
 enum tracefs_dynevent_type *tracefs_dynevent_info*(struct tracefs_dynevent pass:[*]_dynevent_, char pass:[*]pass:[*]_system_, char pass:[*]pass:[*]_event_, char pass:[*]pass:[*]_prefix_, char pass:[*]pass:[*]_addr_, char pass:[*]pass:[*]_format_);
+struct tep_event pass:[*]*tracefs_dynevent_get_event*(struct tep_handle pass:[*]_tep_, struct tracefs_dynevent pass:[*]_dynevent_);
 --
 
 DESCRIPTION
@@ -68,6 +69,10 @@ if relevant for this event type. If _format_ is non NULL, it will hold the forma
 dynamic event. Note, that the content in _group_, _event_, _prefix_, _addr_, and _format_ must be
 freed with free(3) if they are set.
 
+The *tracefs_dynevent_get_event*() function returns a tep event, describing the given dynamic event.
+The API detects any newly created or removed dynamic events. The returned pointer to tep event is
+controlled by @tep and must not be freed.
+
 RETURN VALUE
 ------------
 
@@ -88,6 +93,10 @@ in case of an error or in case there are no events in the system. That array mus
 on error. If _system_, _event_, _prefix_, _addr_, or _format_ are non NULL, they will contain
 allocated strings that must be freed by free(3).
 
+The *tracefs_dynevent_get_event*() function returns a pointer to a tep event or NULL in case of an
+error or if the requested dynamic event is missing. The returned pointer to tep event is controlled
+by @tep and must not be freed.
+
 ERRORS
 ------
 The following errors are for all the above calls:
diff --git a/include/tracefs.h b/include/tracefs.h
index c9ebaa6..383974b 100644
--- a/include/tracefs.h
+++ b/include/tracefs.h
@@ -262,6 +262,8 @@ tracefs_dynevent_get(enum tracefs_dynevent_type type, const char *system, const
 enum tracefs_dynevent_type
 tracefs_dynevent_info(struct tracefs_dynevent *dynevent, char **system,
 		      char **event, char **prefix, char **addr, char **format);
+struct tep_event *
+tracefs_dynevent_get_event(struct tep_handle *tep, struct tracefs_dynevent *dynevent);
 
 struct tracefs_dynevent *
 tracefs_eprobe_alloc(const char *system, const char *event,
diff --git a/src/tracefs-dynevents.c b/src/tracefs-dynevents.c
index ea07d13..d089d02 100644
--- a/src/tracefs-dynevents.c
+++ b/src/tracefs-dynevents.c
@@ -752,3 +752,36 @@ error:
 
 	return TRACEFS_DYNEVENT_UNKNOWN;
 }
+
+/**
+ * tracefs_dynevent_get_event - return tep event representing the given dynamic event
+ * @tep: a handle to the trace event parser context that holds the events
+ * @dynevent: a dynamic event context, describing given dynamic event.
+ *
+ * Returns a pointer to a tep event describing the given dynamic event. The pointer
+ * is managed by the @tep handle and must not be freed. In case of an error, or in case
+ * the requested dynamic event is missing in the @tep handler - NULL is returned.
+ */
+struct tep_event *
+tracefs_dynevent_get_event(struct tep_handle *tep, struct tracefs_dynevent *dynevent)
+{
+	struct tep_event *event;
+
+	if (!tep || !dynevent || !dynevent->event)
+		return NULL;
+
+	/* Check if event exists in the system */
+	if (!tracefs_event_file_exists(NULL, dynevent->system, dynevent->event, "format"))
+		return NULL;
+
+	/* If the dynamic event is already loaded in the tep, return it */
+	event = tep_find_event_by_name(tep, dynevent->system, dynevent->event);
+	if (event)
+		return event;
+
+	/* Try to load any new events from the given system */
+	if (trace_rescan_events(tep, NULL, dynevent->system))
+		return NULL;
+
+	return tep_find_event_by_name(tep, dynevent->system, dynevent->event);
+}
-- 
2.33.1