[PATCH 2/3] tools/lib/traceevent: Changed return logic of tep_register_event_handler() API

[Tzvetomir Stoyanov <tstoyanov@vmware.com>]

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@vmware.com>
---
 .../libtraceevent-reg_event_handler.txt              | 12 +++++++++---
 tools/lib/traceevent/event-parse.c                   | 10 ++++++++--
 tools/lib/traceevent/event-parse.h                   |  5 +++++
 3 files changed, 22 insertions(+), 5 deletions(-)

diff --git a/tools/lib/traceevent/Documentation/libtraceevent-reg_event_handler.txt b/tools/lib/traceevent/Documentation/libtraceevent-reg_event_handler.txt
index 1a9269039f6c..ee9aa3a4151b 100644
--- a/tools/lib/traceevent/Documentation/libtraceevent-reg_event_handler.txt
+++ b/tools/lib/traceevent/Documentation/libtraceevent-reg_event_handler.txt
@@ -12,6 +12,11 @@ SYNOPSIS
 --
 *#include <event-parse.h>*
 
+enum *tep_reg_handler* {
+	_TEP_REGISTER_SUCCESS_,
+	_TEP_REGISTER_SUCCESS_OVERWRITE_,
+};
+
 int *tep_register_event_handler*(struct tep_handle pass:[*]_tep_, int _id_, const char pass:[*]_sys_name_, const char pass:[*]_event_name_, tep_event_handler_func _func_, void pass:[*]_context_);
 int *tep_unregister_event_handler*(struct tep_handle pass:[*]tep, int id, const char pass:[*]sys_name, const char pass:[*]event_name, tep_event_handler_func func, void pass:[*]_context_);
 
@@ -48,9 +53,10 @@ _context_ is custom context, set when the custom event handler is registered.
  
 RETURN VALUE
 ------------
-The _tep_register_event_handler()_ function returns 0 in case of success. 
-If there is not  enough memory to complete the registration, 
-TEP_ERRNO__MEM_ALLOC_FAILED is returned. 
+The _tep_register_event_handler()_ function returns _TEP_REGISTER_SUCCESS_
+if the new handler is registered successfully or _TEP_REGISTER_SUCCESS_OVERWRITE_ if
+an existing handler is overwritten. If there is not  enough memory to complete 
+the registration, TEP_ERRNO__MEM_ALLOC_FAILED is returned. 
 
 The _tep_unregister_event_handler()_ function returns 0 if _func_ was removed 
 successful or, -1 if the event was not found.
diff --git a/tools/lib/traceevent/event-parse.c b/tools/lib/traceevent/event-parse.c
index 2970358b4c10..a5048c1b9bec 100644
--- a/tools/lib/traceevent/event-parse.c
+++ b/tools/lib/traceevent/event-parse.c
@@ -6624,6 +6624,12 @@ 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,
@@ -6641,7 +6647,7 @@ 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. */
@@ -6671,7 +6677,7 @@ 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,
diff --git a/tools/lib/traceevent/event-parse.h b/tools/lib/traceevent/event-parse.h
index c6bdebf0a0ed..e5bdce43b3b4 100644
--- a/tools/lib/traceevent/event-parse.h
+++ b/tools/lib/traceevent/event-parse.h
@@ -484,6 +484,11 @@ 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);
-- 
2.19.1