[PATCH 04/11] perf tools: Use PERF_EVENT_IOC_ID perf ioctl to read event id

[Jiri Olsa]

Changing the way we retrieve the event ID. Instead of parsing out
the ID out of the read data, using the PERF_EVENT_IOC_ID ioctl.

Keeping the old way in place to support kernels without
PERF_EVENT_IOC_ID ioctl support.

This will be useful for retrieving the event ID for events
with PERF_FORMAT_GROUP read format set, where it's impossible
to get correct event id out of the read call data.

Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: Corey Ashford <cjashfor@xxxxxxxxxxxxxxxxxx>
Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
---
 tools/perf/util/evlist.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index eddd5eb..51e21f9 100644
--- a/tools/perf/util/evlist.c
+++ b/tools/perf/util/evlist.c
@@ -298,6 +298,17 @@ static int perf_evlist__id_add_fd(struct perf_evlist *evlist,
 {
 	u64 read_data[4] = { 0, };
 	int id_idx = 1; /* The first entry is the counter value */
+	u64 id;
+	int ret;
+
+	ret = ioctl(fd, PERF_EVENT_IOC_ID, &id);
+	if (!ret)
+		goto add;
+
+	if (errno != ENOTTY)
+		return -1;
+
+	/* Legacy way to get event id.. All hail to old kernels! */
 
 	if (!(evsel->attr.read_format & PERF_FORMAT_ID) ||
 	    read(fd, &read_data, sizeof(read_data)) == -1)
@@ -308,7 +319,10 @@ static int perf_evlist__id_add_fd(struct perf_evlist *evlist,
 	if (evsel->attr.read_format & PERF_FORMAT_TOTAL_TIME_RUNNING)
 		++id_idx;
 
-	perf_evlist__id_add(evlist, evsel, cpu, thread, read_data[id_idx]);
+	id = read_data[id_idx];
+
+ add:
+	perf_evlist__id_add(evlist, evsel, cpu, thread, id);
 	return 0;
 }
 
-- 
1.7.11.7

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