Audio: Add a NULL audio device that can be used to simply unit-level testing of audio decoders

drivers/audio/Kconfig

@@ -106,5 +106,57 @@ config AUDIO_WM8904
 		that dependency is not explicit here.
 
 if AUDIO_WM8904
+
+config WM8904_INITVOLUME
+	int "WM8904 initial volume setting"
+	default 250
+
+config WM8904_INFLIGHT
+	int "WM8904 maximum in-flight audio buffers"
+	default 2
+
+config WM8904_MSG_PRIO
+	int "WM8904 message priority"
+	default 1
+
+config WM8904_BUFFER_SIZE
+	int "WM8904 preferred buffer size"
+	default 8192
+
+config WM8904_NUM_BUFFERS
+	int "WM8904 preferred number of buffers"
+	default 4
+
+config WM8904_WORKER_STACKSIZE
+	int "WM8904 worker thread stack size"
+	default 768
+
 endif # AUDIO_WM8904
 
+config AUDIO_NULL
+	bool "NULL audio device"
+	default n
+	depends on AUDIO
+	---help---
+		A do-nothinig audio device driver to simplify testing of audio
+		decoders.
+
+if AUDIO_NULL
+
+config AUDIO_NULL_MSG_PRIO
+	int "Null audio device message priority"
+	default 1
+
+config UDIO_NULL_BUFFER_SIZE
+	int "Null audio device preferred buffer size"
+	default 8192
+
+config AUDIO_NULL_NUM_BUFFERS
+	int "Null audio device preferred number of buffers"
+	default 4
+
+config AUDIO_NULL_WORKER_STACKSIZE
+	int "Null audio device worker thread stack size"
+	default 768
+
+endif # AUDIO_NULL

drivers/audio/Make.defs

@@ -47,6 +47,10 @@ ifeq ($(CONFIG_AUDIO_WM8904),y)
 CSRCS += wm8904.c
 endif
 
+ifeq ($(CONFIG_AUDIO_NULL),y)
+CSRCS += audio_null.c
+endif
+
 ifeq ($(CONFIG_AUDIO_I2SCHAR),y)
 CSRCS += i2schar.c
 endif

drivers/audio/wm8904.c

@@ -95,7 +95,7 @@ struct wm8904_dev_s
    * "half" that is referred to as "lower".
    */
 
-  struct audio_lowerhalf_s dev;             /* WM8904 audio lower half (this drive) */
+  struct audio_lowerhalf_s dev;             /* WM8904 audio lower half (this device) */
 
   /* Our specific driver data goes here */
 
@@ -181,15 +181,10 @@ static int      wm8904_stop(FAR struct audio_lowerhalf_s *dev);
 #ifdef CONFIG_AUDIO_MULTI_SESSION
 static int      wm8904_pause(FAR struct audio_lowerhalf_s *dev,
                   FAR void* session);
-#else
-static int      wm8904_pause(FAR struct audio_lowerhalf_s *dev);
-#endif
-#endif
-#ifndef CONFIG_AUDIO_EXCLUDE_PAUSE_RESUME
-#ifdef CONFIG_AUDIO_MULTI_SESSION
 static int      wm8904_resume(FAR struct audio_lowerhalf_s *dev,
                   FAR void* session);
 #else
+static int      wm8904_pause(FAR struct audio_lowerhalf_s *dev);
 static int      wm8904_resume(FAR struct audio_lowerhalf_s *dev);
 #endif
 #endif
@@ -1755,8 +1750,8 @@ static void wm8904_audio_input(FAR struct wm8904_dev_s *priv)
  *   lower   - Persistent board configuration data
  *
  * Returned Value:
- *   A new lower half audio interface is returned for the WM8904 device is
- *   returned on success; NULL is returned on failure.
+ *   A new lower half audio interface for the WM8904 device is returned on
+ *   success; NULL is returned on failure.
  *
  ****************************************************************************/