[audio] Add comment to inform that it's optional

Change-Id: I65d27b6aa4d262cdcd2a651f74c70b2cad620e42
Signed-off-by: Jeongmo Yang <jm80.yang@samsung.com>

diff --git a/include/audio/tizen-audio.h b/include/audio/tizen-audio.h
index 6d4a1a1..a476c88 100644 (file)
--- a/include/audio/tizen-audio.h
+++ b/include/audio/tizen-audio.h
@@ -145,7 +145,7 @@ typedef struct audio_interface {
     audio_return_t (*get_volume_mute)(void *audio_handle, audio_volume_info_t *info, uint32_t *mute);
     audio_return_t (*set_volume_mute)(void *audio_handle, audio_volume_info_t *info, uint32_t mute);
     audio_return_t (*set_volume_ratio)(void *audio_handle, audio_stream_info_t *info, double ratio); /* optional */
-    audio_return_t (*notify_ducking_activation_changed)(void *audio_handle, audio_ducking_info_t *info, uint32_t is_activated);
+    audio_return_t (*notify_ducking_activation_changed)(void *audio_handle, audio_ducking_info_t *info, uint32_t is_activated); /* optional */
     /* Routing */
     audio_return_t (*update_route)(void *audio_handle, audio_route_info_t *info);
     audio_return_t (*update_route_option)(void *audio_handle, audio_route_option_t *option);
@@ -299,7 +299,7 @@ audio_return_t audio_set_volume_mute(void *audio_handle, audio_volume_info_t *in
 audio_return_t audio_set_volume_ratio(void *audio_handle, audio_stream_info_t *info, double ratio);
 
 /**
- * @brief Gets notified when a ducking is activated and deactivated.
+ * @brief Gets notified when a ducking is activated and deactivated. (optional)
  * @since_tizen 5.5
  * @param[in] audio_handle The audio hal handle
  * @param[in] info The ducking information including target role, duration and ratio