perf ui: Introduce struct perf_error_ops

The struct perf_error_ops is for flexible error logging.

We can register appropriate functions based on front-end.

Signed-off-by: Namhyung Kim <namhyung.kim@lge.com>
Acked-by: Pekka Enberg <penberg@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1338265382-6872-4-git-send-email-namhyung@gmail.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/tools/perf/ui/util.h b/tools/perf/ui/util.h
index 2d1738b..361f08c 100644
--- a/tools/perf/ui/util.h
+++ b/tools/perf/ui/util.h
@@ -9,6 +9,13 @@
 int ui__dialog_yesno(const char *msg);
 int ui__question_window(const char *title, const char *text,
 			const char *exit_msg, int delay_secs);
-int __ui__warning(const char *title, const char *format, va_list args);
+
+struct perf_error_ops {
+	int (*error)(const char *format, va_list args);
+	int (*warning)(const char *format, va_list args);
+};
+
+int perf_error__register(struct perf_error_ops *eops);
+int perf_error__unregister(struct perf_error_ops *eops);
 
 #endif /* _PERF_UI_UTIL_H_ */