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 <[e-mail]>
Cc: Alexander Shishkin <[e-mail]>
Cc: Andi Kleen <[e-mail]>
Cc: David Ahern <[e-mail]>
Cc: Geneviève Bastien <[e-mail]>
Cc: Ian Rogers <[e-mail]>
Cc: Jeremie Galarneau <[e-mail]>
Cc: Michael Petlan <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Wang Nan <[e-mail]>
Link: http://lore.kernel.org/lkml/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/util/clockid.c

···
 	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

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