tracing: probes: Add a kerneldoc for traceprobe_parse_event_name()

Since traceprobe_parse_event_name() is a bit complicated, add a
kerneldoc for explaining the behavior.

Link: https://lore.kernel.org/all/175323430565.57270.2602609519355112748.stgit@devnote2/

Suggested-by: Steven Rostedt <[email protected]>
Signed-off-by: Masami Hiramatsu (Google) <[email protected]>
Reviewed-by: Steven Rostedt (Google) <[email protected]>

Author: mhiramat

kernel/trace/trace_probe.c

@@ -247,7 +247,25 @@ int traceprobe_split_symbol_offset(char *symbol, long *offset)
 	return 0;
 }
 
-/* @buf must has MAX_EVENT_NAME_LEN size */
+/**
+ * traceprobe_parse_event_name() - Parse a string into group and event names
+ * @pevent: A pointer to the string to be parsed.
+ * @pgroup: A pointer to the group name.
+ * @buf:    A buffer to store the parsed group name.
+ * @offset: The offset of the string in the original user command, for logging.
+ *
+ * This parses a string with the format `[GROUP/][EVENT]` or `[GROUP.][EVENT]`
+ * (either GROUP or EVENT or both must be specified).
+ * Since the parsed group name is stored in @buf, the caller must ensure @buf
+ * is at least MAX_EVENT_NAME_LEN bytes.
+ *
+ * Return: 0 on success, or -EINVAL on failure.
+ *
+ * If success, *@pevent is updated to point to the event name part of the
+ * original string, or NULL if there is no event name.
+ * Also, *@pgroup is updated to point to the parsed group which is stored
+ * in @buf, or NULL if there is no group name.
+ */
 int traceprobe_parse_event_name(const char **pevent, const char **pgroup,
 				char *buf, int offset)
 {