perf evsel: Introduce set_filter method

Replaces existing filter string with the one provided.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: David Ahern <dsahern@gmail.com>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-jst49z83li0yx3g18o54u51a@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index 6676774..ae925b9 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -823,6 +823,19 @@
 				     (void *)filter);
 }
 
+int perf_evsel__set_filter(struct perf_evsel *evsel, const char *filter)
+{
+	char *new_filter = strdup(filter);
+
+	if (new_filter != NULL) {
+		free(evsel->filter);
+		evsel->filter = new_filter;
+		return 0;
+	}
+
+	return -1;
+}
+
 int perf_evsel__enable(struct perf_evsel *evsel, int ncpus, int nthreads)
 {
 	return perf_evsel__run_ioctl(evsel, ncpus, nthreads,