[PATCH 4/6] trace-cmd: Changed return logic of tep_register_event_handler() API

[Tzvetomir Stoyanov <tstoyanov@xxxxxxxxxx>]

In order to make libtraceevent into a proper library, its API
should be straightforward.

The tep_register_event_handler() functions returns -1 in case it
successfully registers the new event handler. Such return code is used
by the other library APIs in case of an error.

To unify the return logic of tep_register_event_handler() with the other
APIs, this patch introduces enum tep_reg_handler, which is used by this
function as return value, to handle all possible successful return
cases.

Signed-off-by: Tzvetomir Stoyanov <tstoyanov@xxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Link: http://lkml.kernel.org/r/20181201040852.628034497@xxxxxxxxxxx
Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
---
 include/traceevent/event-parse.h |  5 +++++
 lib/traceevent/event-parse.c     | 10 ++++++++--
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/include/traceevent/event-parse.h b/include/traceevent/event-parse.h
index 426b7eb..b4fa2c7 100644
--- a/include/traceevent/event-parse.h
+++ b/include/traceevent/event-parse.h
@@ -473,6 +473,11 @@ int tep_print_func_field(struct trace_seq *s, const char *fmt,
 			 struct tep_event *event, const char *name,
 			 struct tep_record *record, int err);
 
+enum tep_reg_handler {
+	TEP_REGISTER_SUCCESS = 0,
+	TEP_REGISTER_SUCCESS_OVERWRITE,
+};
+
 int tep_register_event_handler(struct tep_handle *pevent, int id,
 			       const char *sys_name, const char *event_name,
 			       tep_event_handler_func func, void *context);
diff --git a/lib/traceevent/event-parse.c b/lib/traceevent/event-parse.c
index 1f1821d..8cdb5a3 100644
--- a/lib/traceevent/event-parse.c
+++ b/lib/traceevent/event-parse.c
@@ -6699,6 +6699,12 @@ static struct tep_event *search_event(struct tep_handle *pevent, int id,
  *
  * If @id is >= 0, then it is used to find the event.
  * else @sys_name and @event_name are used.
+ *
+ * Returns:
+ *  TEP_REGISTER_SUCCESS_OVERWRITE if an existing handler is overwritten
+ *  TEP_REGISTER_SUCCESS if a new handler is registered successfully
+ *  negative TEP_ERRNO_... in case of an error
+ *
  */
 int tep_register_event_handler(struct tep_handle *pevent, int id,
 			       const char *sys_name, const char *event_name,
@@ -6716,7 +6722,7 @@ int tep_register_event_handler(struct tep_handle *pevent, int id,
 
 	event->handler = func;
 	event->context = context;
-	return 0;
+	return TEP_REGISTER_SUCCESS_OVERWRITE;
 
  not_found:
 	/* Save for later use. */
@@ -6746,7 +6752,7 @@ int tep_register_event_handler(struct tep_handle *pevent, int id,
 	pevent->handlers = handle;
 	handle->context = context;
 
-	return -1;
+	return TEP_REGISTER_SUCCESS;
 }
 
 static int handle_matches(struct event_handler *handler, int id,
-- 
2.20.1