linux-kernel - [PATCH 03/11] perf tool: Use PERF_EVENT_IOC

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Date:	Sat, 20 Oct 2012 16:33:11 +0200
From:	Jiri Olsa <jolsa@...hat.com>
To:	linux-kernel@...r.kernel.org
Cc:	Jiri Olsa <jolsa@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Ingo Molnar <mingo@...e.hu>, Paul Mackerras <paulus@...ba.org>,
	Corey Ashford <cjashfor@...ux.vnet.ibm.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Namhyung Kim <namhyung@...nel.org>
Subject: [PATCH 03/11] perf tool: Use PERF_EVENT_IOC_ID perf ioctl to read event id

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.

Signed-off-by: Jiri Olsa <jolsa@...hat.com>
Cc: Arnaldo Carvalho de Melo <acme@...stprotocols.net>
Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc: Ingo Molnar <mingo@...e.hu>
Cc: Paul Mackerras <paulus@...ba.org>
Cc: Corey Ashford <cjashfor@...ux.vnet.ibm.com>
Cc: Frederic Weisbecker <fweisbec@...il.com>
Cc: Namhyung Kim <namhyung@...nel.org>
---
 tools/perf/util/evlist.c | 34 ++++++++++++++++++++++++----------
 1 file changed, 24 insertions(+), 10 deletions(-)

diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index 561bdfb..ef13aab 100644
--- a/tools/perf/util/evlist.c
+++ b/tools/perf/util/evlist.c
@@ -290,19 +290,33 @@ static int perf_evlist__id_add_fd(struct perf_evlist *evlist,
 				  struct perf_evsel *evsel,
 				  int cpu, int thread, int fd)
 {
-	u64 read_data[4] = { 0, };
-	int id_idx = 1; /* The first entry is the counter value */
+	u64 id;
+	int ret;
 
-	if (!(evsel->attr.read_format & PERF_FORMAT_ID) ||
-	    read(fd, &read_data, sizeof(read_data)) == -1)
-		return -1;
+	ret = ioctl(fd, PERF_EVENT_IOC_ID, &id);
+	if (!ret)
+		goto add;
+
+	/* Legacy way to get event id.. All hail to old kernels! */
+	if (errno == ENOTTY) {
+		u64 read_data[4] = { 0, };
+		int id_idx = 1; /* The first entry is the counter value */
+
+		if (!(evsel->attr.read_format & PERF_FORMAT_ID) ||
+		    read(fd, &read_data, sizeof(read_data)) == -1)
+			return -1;
 
-	if (evsel->attr.read_format & PERF_FORMAT_TOTAL_TIME_ENABLED)
-		++id_idx;
-	if (evsel->attr.read_format & PERF_FORMAT_TOTAL_TIME_RUNNING)
-		++id_idx;
+		if (evsel->attr.read_format & PERF_FORMAT_TOTAL_TIME_ENABLED)
+			++id_idx;
+		if (evsel->attr.read_format & PERF_FORMAT_TOTAL_TIME_RUNNING)
+			++id_idx;
+
+		id = read_data[id_idx];
+	} else if (errno)
+		return -1;
 
-	perf_evlist__id_add(evlist, evsel, cpu, thread, read_data[id_idx]);
+ add:
+	perf_evlist__id_add(evlist, evsel, cpu, thread, id);
 	return 0;
 }
 
-- 
1.7.11.4

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