perf session: Share the common trace sample_check routine as perf_session__has_traces

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frédéric Weisbecker <fweisbec@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
LKML-Reference: <1261957026-15580-5-git-send-email-acme@infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
index 736d4fd..60eab8b 100644
--- a/tools/perf/util/session.c
+++ b/tools/perf/util/session.c
@@ -393,3 +393,14 @@
 out_err:
 	return err;
 }
+
+int perf_session__has_traces(struct perf_session *self)
+{
+	if (!(self->sample_type & PERF_SAMPLE_RAW)) {
+		pr_err("No trace sample to read. Did you call perf record "
+		       "without -R?");
+		return -1;
+	}
+
+	return 0;
+}