perf trace/scripting: Don't display 'scripting unsupported' msg unnecessarily

The 'scripting unsupported' message should only be displayed
when the -s or -g options are used, and not when they aren't, as
the current code does.

Signed-off-by: Tom Zanussi <tzanussi@gmail.com>
Cc: rostedt@goodmis.org
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <1260163919-6679-3-git-send-email-tzanussi@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

tools/perf/util/trace-event-perl.c

@@ -570,26 +570,72 @@ struct scripting_ops perl_scripting_ops = {
 	.generate_script = perl_generate_script,
 };
 
-#ifdef NO_LIBPERL
-void setup_perl_scripting(void)
+static void print_unsupported_msg(void)
 {
 	fprintf(stderr, "Perl scripting not supported."
-		"  Install libperl and rebuild perf to enable it.  e.g. "
-		"apt-get install libperl-dev (ubuntu), yum install "
-		"perl-ExtUtils-Embed (Fedora), etc.\n");
+		"  Install libperl and rebuild perf to enable it.\n"
+		"For example:\n  # apt-get install libperl-dev (ubuntu)"
+		"\n  # yum install perl-ExtUtils-Embed (Fedora)"
+		"\n  etc.\n");
 }
-#else
-void setup_perl_scripting(void)
+
+static int perl_start_script_unsupported(const char *script __unused)
+{
+	print_unsupported_msg();
+
+	return -1;
+}
+
+static int perl_stop_script_unsupported(void)
+{
+	return 0;
+}
+
+static void perl_process_event_unsupported(int cpu __unused,
+					   void *data __unused,
+					   int size __unused,
+					   unsigned long long nsecs __unused,
+					   char *comm __unused)
+{
+}
+
+static int perl_generate_script_unsupported(const char *outfile __unused)
+{
+	print_unsupported_msg();
+
+	return -1;
+}
+
+struct scripting_ops perl_scripting_unsupported_ops = {
+	.name = "Perl",
+	.start_script = perl_start_script_unsupported,
+	.stop_script = perl_stop_script_unsupported,
+	.process_event = perl_process_event_unsupported,
+	.generate_script = perl_generate_script_unsupported,
+};
+
+static void register_perl_scripting(struct scripting_ops *scripting_ops)
 {
 	int err;
-	err = script_spec_register("Perl", &perl_scripting_ops);
+	err = script_spec_register("Perl", scripting_ops);
 	if (err)
 		die("error registering Perl script extension");
 
-	err = script_spec_register("pl", &perl_scripting_ops);
+	err = script_spec_register("pl", scripting_ops);
 	if (err)
 		die("error registering pl script extension");
 
 	scripting_context = malloc(sizeof(struct scripting_context));
 }
+
+#ifdef NO_LIBPERL
+void setup_perl_scripting(void)
+{
+	register_perl_scripting(&perl_scripting_unsupported_ops);
+}
+#else
+void setup_perl_scripting(void)
+{
+	register_perl_scripting(&perl_scripting_ops);
+}
 #endif