perf tools: Add clockid_name function

Add the clockid_name() function to get the clock name based on its
clockid.  It will be used in the following changes.
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Geneviève Bastien <gbastien@versatic.net>
Cc: Ian Rogers <irogers@google.com>
Cc: Jeremie Galarneau <jgalar@efficios.com>
Cc: Michael Petlan <mpetlan@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lore.kernel.org/lkml/20200805093444.314999-3-jolsa@kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/clockid.c

@@ -106,3 +106,14 @@ int parse_clockid(const struct option *opt, const char *str, int unset)
 	ui__warning("unknown clockid %s, check man page\n", ostr);
 	return -1;
 }
+
+const char *clockid_name(clockid_t clk_id)
+{
+	const struct clockid_map *cm;
+
+	for (cm = clockids; cm->name; cm++) {
+		if (cm->clockid == clk_id)
+			return cm->name;
+	}
+	return "(not found)";
+}

tools/perf/util/clockid.h

@@ -6,4 +6,6 @@
 struct option;
 int parse_clockid(const struct option *opt, const char *str, int unset);
 
+const char *clockid_name(clockid_t clk_id);
+
 #endif