Moving mixers to audio outputs

src/output_api.h

@@ -100,6 +100,12 @@ struct audio_output_plugin {
 	 */
 	void (*close)(void *data);
 
+	/**
+	 * Control the device. Usualy used for implementing
+	 * set and get mixer levels
+	 */
+	bool (*control)(void *data, int cmd, void *arg);
+
 	/**
 	 * Display metadata for the next chunk.  Optional method,
 	 * because not all devices can display metadata.
@@ -118,6 +124,12 @@ enum audio_output_command {
 	AO_COMMAND_KILL
 };
 
+enum audio_control_command {
+	AC_MIXER_GETVOL = 0,
+	AC_MIXER_SETVOL,
+	AC_MIXER_CONFIGURE,
+};
+
 struct audio_output;
 
 const char *audio_output_get_name(const struct audio_output *ao);