tools lib api fs tracing_path: Introduce opendir() method

That takes care of using the right call to get the tracing_path
directory, the one that will end up calling tracing_path_set() to figure
out where tracefs is mounted.

One more step in doing just lazy reading of system structures to reduce
the number of operations done unconditionaly at 'perf' start.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: https://lkml.kernel.org/n/tip-42zzi0f274909bg9mxzl81bu@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
index 2466830..15eec49 100644
--- a/tools/perf/util/parse-events.c
+++ b/tools/perf/util/parse-events.c
@@ -191,7 +191,7 @@ struct tracepoint_path *tracepoint_id_to_path(u64 config)
 	char evt_path[MAXPATHLEN];
 	char *dir_path;
 
-	sys_dir = opendir(tracing_events_path);
+	sys_dir = tracing_events__opendir();
 	if (!sys_dir)
 		return NULL;
 
@@ -578,7 +578,7 @@ static int add_tracepoint_multi_sys(struct list_head *list, int *idx,
 	DIR *events_dir;
 	int ret = 0;
 
-	events_dir = opendir(tracing_events_path);
+	events_dir = tracing_events__opendir();
 	if (!events_dir) {
 		tracepoint_error(err, errno, sys_name, evt_name);
 		return -1;
@@ -2106,7 +2106,7 @@ void print_tracepoint_events(const char *subsys_glob, const char *event_glob,
 	bool evt_num_known = false;
 
 restart:
-	sys_dir = opendir(tracing_events_path);
+	sys_dir = tracing_events__opendir();
 	if (!sys_dir)
 		return;
 
@@ -2200,7 +2200,7 @@ int is_valid_tracepoint(const char *event_string)
 	char evt_path[MAXPATHLEN];
 	char *dir_path;
 
-	sys_dir = opendir(tracing_events_path);
+	sys_dir = tracing_events__opendir();
 	if (!sys_dir)
 		return 0;