Updated audio subsystem from Ken Pettit

5 files changed, 745 insertions, 171 deletions

diff --git a/nuttx/audio/Kconfig b/nuttx/audio/Kconfig
index 7ce503aaf..ef4bfe779 100644
--- a/nuttx/audio/Kconfig
+++ b/nuttx/audio/Kconfig
@@ -11,53 +11,64 @@ config AUDIO
 
 if AUDIO
 
-config AUDIO_NCHANNELS
-	int "Number of Audio Channels"
-	default 2
+config AUDIO_MULTI_SESSION
+	bool "Support multiple sessions"
+	default n
 	---help---
-		Stereo channel support is standard, but some systems may support 5 or 7
-		channel capability.
+		Some audio devices, such as USB attached sound cards, may support more
+		than one streaming session at a time (each with one or more audio channels).
+		Selecting this feature adds support for tracking multiple concurrent
+		sessions with the lower-level audio devices.
 
 config AUDIO_LARGE_BUFFERS
 	bool "Support Audio Buffers with greater than 65K samples"
 	default n
 	---help---
-		By default, the Audio Pipeline Buffer uses a 16-bit max sample count, limiting
+		By default, the Audio Pipeline Buffers use a 16-bit max sample count, limiting
 		the number of samples per buffer to 65K.  Enable this option to specify a
 		32-bit max sample count for increased samples / buffer capability.
 		channel capability.
 
-config AUDIO_CUSTOM_DEV_PATH
-	bool "Use custom device path"
-	default n
+config AUDIO_NUM_BUFFERS
+	int "Number of buffers for audio processing"
+	default 2
 	---help---
-		By default, all audio devices on the target are are registered in the
-		/dev/audio directory.  Select this option to change the default location
-		for the device registration.
-
-if AUDIO_CUSTOM_DEV_PATH
+		Specifies the number of buffers to allocate for audio processing.
+		If Driver Specified buffer sizes is enabled (below), then the
+		low-level drivers will have the opportunity to override this
+		value.
+
+config AUDIO_BUFFER_NUMBYTES
+	int "Size of each audio buffer for audio processing"
+	default 8192
+	---help---
+		Specifies the allocation size for each audio buffer
+		If Driver Specified buffer sizes is enabled (below), then the
+		low-level drivers will have the opportunity to override this
+		value.
 
-config AUDIO_DEV_ROOT
-	bool "Place audio devices in /dev"
+config AUDIO_DRIVER_SPECIFIC_BUFFERS
+	bool "Support for Driver specified buffer sizes"
 	default n
 	---help---
-		This option causes all device entries to appear in /dev with all the
-		other device entries.  This option generates the smallest code and
-		RAM footprint.
+		By default, the Audio system uses the same size and number of buffers
+		regardless of the specific audio device in use.  Specifying 'y' here
+		adds extra code which allows the lower-level audio device to specify
+		a partucular size and number of buffers.
 
-if !AUDIO_DEV_ROOT
+menu "Supported Audio Formats"
 
-config AUDIO_DEV_PATH
-	string "Base path for Audio devices"
-	default "/dev/audio"
+config AUDIO_FORMAT_AC3
+	bool "AC3 Format"
+	default n
 	---help---
-		The path on the target where audio devices are registered.  The default
-		is to place all audio devices in the /dev/audio/ directory.
+		Build in support for AC3 (Dolby Digital) Audio format.
 
-endif
-endif
-
-menu "Supported Audio Formats"
+config AUDIO_FORMAT_DTS
+	bool "DTS Format"
+	default n
+	---help---
+		Add in support for DTS format.
 
 config AUDIO_FORMAT_PCM
 	bool "PCM Audio"
@@ -67,10 +78,16 @@ config AUDIO_FORMAT_PCM
 
 config AUDIO_FORMAT_MP3
 	bool "MPEG 3 Layer 1"
-	default n
+	default y
 	---help---
 		Build in support for MP3 Audio format.
 
+config AUDIO_FORMAT_MIDI
+	bool "Midi Format"
+	default n
+	---help---
+		Add in support for MIDI format.
+
 config AUDIO_FORMAT_WMA
 	bool "WMA Format (see copyright notice)"
 	default n
@@ -85,6 +102,79 @@ config AUDIO_FORMAT_OGG_VORBIS
 
 endmenu
 
+menu "Exclude Specific Audio Features"
+
+config AUDIO_EXCLUDE_VOLUME
+	bool "Exclude volume controls"
+	default n
+	---help---
+		Exclude building support for changing the playback volume.
+
+config AUDIO_EXCLUDE_BALANCE
+	bool "Exclude balance controls"
+	default n
+	---help---
+		Exclude building support for changing the balance.
+
+config AUDIO_EXCLUDE_TONE
+	bool "Exclude tone (bass and treble) controls"
+	default n
+	---help---
+		Exclude building support for changing the bass and treble.
+
+config AUDIO_EXCLUDE_PAUSE_RESUME
+	bool "Exclude pause and resume controls"
+	default n
+	---help---
+		Exclude building support for pausing and resuming audio files
+		once they are submitted.  If the sound system is being used to play
+		short system notification or error type sounds that typicaly only
+		last a second or two, then there is no need (or chance) to pause or
+		resume sound playback once it has started.
+
+config AUDIO_EXCLUDE_STOP
+	bool "Exclude stop playback controls"
+	default n
+	---help---
+		Exclude building support for stopping audio files once they are
+		submitted.  If the sound system is being used to play short ssytem
+		notification or error type sounds that typicaly only last a second
+		or two, then there is no need (or chance) to stop the sound
+		playback once it has started.
+
+endmenu
+
+config AUDIO_CUSTOM_DEV_PATH
+	bool "Use custom device path"
+	default n
+	---help---
+		By default, all audio devices on the target are are registered in the
+		/dev/audio directory.  Select this option to change the default location
+		for the device registration.
+
+if AUDIO_CUSTOM_DEV_PATH
+
+config AUDIO_DEV_ROOT
+	bool "Place audio devices in /dev"
+	default n
+	---help---
+		This option causes all device entries to appear in /dev with all the
+		other device entries.  This option generates the smallest code and
+		RAM footprint.
+
+if !AUDIO_DEV_ROOT
+
+config AUDIO_DEV_PATH
+	string "Base path for Audio devices"
+	default "/dev/audio"
+	---help---
+		The path on the target where audio devices are registered.  The default
+		is to place all audio devices in the /dev/audio/ directory.
+
+endif
+endif
+
+
 # These are here as placeholders of what could be added
 
 if CONFIG_AUDIO_PLANNED
diff --git a/nuttx/audio/Makefile b/nuttx/audio/Makefile
index b6c111621..7b34de1ae 100644
--- a/nuttx/audio/Makefile
+++ b/nuttx/audio/Makefile
@@ -53,18 +53,6 @@ ifeq ($(CONFIG_AUDIO_FORMAT_PCM),y)
   CSRCS += pcm.c
 endif
 
-ifeq ($(CONFIG_AUDIO_MIXER),y)
-  CSRCS += mixer.c
-endif
-
-ifeq ($(CONFIG_AUDIO_MIDI_SYNTH),y)
-  CSRCS += midisynth.c
-endif
-
-ifeq ($(CONFIG_AUDIO_FONT),y)
-  CSRCS += audio_font.c
-endif
-
 AOBJS = $(ASRCS:.S=$(OBJEXT))
 COBJS = $(CSRCS:.c=$(OBJEXT))
 
diff --git a/nuttx/audio/README.txt b/nuttx/audio/README.txt
new file mode 100644
index 000000000..80178865d
--- /dev/null
+++ b/nuttx/audio/README.txt
@@ -0,0 +1,125 @@
+README
+^^^^^^
+
+This directory contains the audio subsytem support for NuttX.  The contents of this
+directory are only built if CONFIG_AUDIO is defined in the NuttX configuration file.
+
+Contents
+^^^^^^^^
+  - Files in this directory
+  - Related Header Files
+  - Related directories
+
+Files in this directory
+^^^^^^^^^^^^^^^^^^^^^^^
+
+This directory holds the NuttX audio subsystem upper-half.  The upper-half provides
+a common interface for applications to interface with and also defines a bind
+layer for specific lower-half audio device drivers.
+
+  audio.c   - The upper-half driver that binds to a lower-half driver from the
+              drivers/audio subdirectory.  For each attached audio device, there
+              will be an instance of this upper-half driver bound to the
+              instance of the lower half driver context.
+  buffer.c  - Routines to manage creattion and destruction of audio pipeline buffers
+              (apb) used in the audio subsystem.  Audio pipeline buffers are passed
+              between user applications and the audio drivers to deliver audio
+              content for playback (or possibly recording in the future).
+  pcm.c     - Routines to manage PCM / WAV type data.  Currently just a placeholder.
+  README    - This file!
+
+
+Related Header Files
+^^^^^^^^^^^^^^^^^^^^
+
+include/nuttx/audio/audio.h   -- Top level include file defining the audio interface
+include/nuttx/audio/vs1053.h  -- Specific driver initialization prototypes
+
+Configuration Settings
+^^^^^^^^^^^^^^^^^^^^^^
+
+General Audio Settings
+----------------------
+
+CONFIG_AUDIO
+  Enables overall support for audio subsystem
+CONFIG_AUDIO_MULTI_SESSION
+  Enables support for the audio subystem to track mutliple open sessions
+  with lower-level audio devices.
+CONFIG_AUDIO_LARGE_BUFFERS
+  Specifies that buffer size variables should be 32-bit vs. the normal 16-bit
+  size.  This allows buffers to be larger than 64K bytes on systems with
+  an abundance of RAM.
+CONFIG_AUDIO_NUM_BUFFERS
+  Sets the number of audio buffers to use for audio operations.  If the
+  configuration has set CONFIG_AUDIO_DRIVER_SPECIFIC_BUFFERS, and an audio
+  device does not support the operation, then this becomes the default number
+  of buffers to use.
+CONFIG_AUDIO_BUFFER_SIZE
+  Sets the size of the audio buffers to use for audio operations.  If the
+  configuration has set CONFIG_AUDIO_DRIVER_SPECIFIC_BUFFERS, and an audio
+  device does not support the operation, then this becomes the default size
+  of buffers to use.
+CONFIG_AUDIO_DRIVER_SPECIFIC_BUFFERS
+  Enables support for lower-level audio drivers to specify the number and size
+  of buffers that should be allocated for best performance while interacting
+  with that driver.
+CONFIG_AUDIO_CUSTOM_DEV_PATH
+  Specifies that all audio devices should be registered in the filesystem at
+  a location other than the standard /dev/audio directory.
+CONFIG_AUDIO_DEV_ROOT
+  Specifies that all audio devices should be registered in the /dev directory.
+  Saves a tiny bit of code and RAM space since an additional directory isn't needed,
+  but at the expense of execution speed when searching for audio devices since all
+  entries in /dev must be opened and tested if they provide audio support.
+  Available only if CONFIG_AUDIO_CUSTOM_DEV_PATH is selected.
+CONFIG_AUDIO_DEV_PATH
+  Specifies a custom directory where audio devices will be registered.
+  Available if CONFIG_AUDIO_CUSTOM_DEV_PATH is selected and CONFIG_AUDIO_DEV_ROOT
+  is not selected.
+
+
+Audio Format Support Selections
+-------------------------------
+
+CONFIG_AUDIO_FORMAT_AC3
+  Specifies that AC3 support should be enabled if available by a lower-half driver.
+CONFIG_AUDIO_FORMAT_DTS
+  Specifies that DTS support should be enabled if available by a lower-half driver.
+CONFIG_AUDIO_FORMAT_PCM
+  Specifies that PCM support should be enabled if available by a lower-half driver.
+CONFIG_AUDIO_FORMAT_MP3
+  Specifies that MP3 support should be enabled if available by a lower-half driver.
+CONFIG_AUDIO_FORMAT_MIDI
+  Specifies that MIDI support should be enabled if available by a lower-half driver.
+CONFIG_AUDIO_FORMAT_WMA
+  Specifies that WMA support should be enabled if available by a lower-half driver.
+CONFIG_AUDIO_FORMAT_OGG_VORBIS
+  Specifies that Ogg Vorbis support should be enabled if available by a lower-half driver.
+
+
+Audio feature exclusion Selections
+----------------------------------
+
+CONFIG_AUDIO_EXCLUDE_VOLUME
+  Disables support in all libraries and drivers for setting the playback volume.  In
+  this case, the device volume will depend on the default level defined by the
+  lower-level driver, typically via a config setting.
+CONFIG_AUDIO_EXCLUDE_BALANCE
+  Disables support in all libraries and drivers for setting the playback balance.
+  Also, the volume support must not be excluded for balance to work or make sense.
+CONFIG_AUDIO_EXCLUDE_TONE
+  Disables support for setting bass and treble.
+CONFIG_AUDIO_EXCLUDE_PAUSE_RESUME
+  Disables support in all libraries and drivers for pausing and resuming playback.
+CONFIG_AUDIO_EXCLUDE_STOP
+  Disables support in all libraries and drivers for stopping an audio playback
+  once it has started.  Typically selected if only short notification audio sounds
+  are needed (vs. media playing type applications).
+
+Related Subdirectories
+^^^^^^^^^^^^^^^^^^^^^^
+
+drivers/audio           -- Contains the lower-level device specific drivers.
+apps/system/nxplayer    -- User-mode audio subsystem interface library.
+
diff --git a/nuttx/audio/audio.c b/nuttx/audio/audio.c
index 444412c97..351ed8ad9 100644
--- a/nuttx/audio/audio.c
+++ b/nuttx/audio/audio.c
@@ -60,6 +60,7 @@
 #include <nuttx/fs/fs.h>
 #include <nuttx/arch.h>
 #include <nuttx/audio/audio.h>
+#include <mqueue.h>
 
 #include <arch/irq.h>
 
@@ -75,6 +76,10 @@
 #  define AUDIO_MAX_DEVICE_PATH 32
 #endif
 
+#ifndef CONFIG_AUDIO_BUFFER_DEQUEUE_PRIO
+#  define CONFIG_AUDIO_BUFFER_DEQUEUE_PRIO  1
+#endif
+
 /****************************************************************************
  * Private Type Definitions
  ****************************************************************************/
@@ -84,10 +89,10 @@
 struct audio_upperhalf_s
 {
   uint8_t           crefs;    /* The number of times the device has been opened */
-  volatile bool     started;  /* True: pulsed output is being generated */
+  volatile bool     started;  /* True: playback is active */
   sem_t             exclsem;  /* Supports mutual exclusion */
-  struct audio_info_s info;     /* Pulsed output characteristics */
   FAR struct audio_lowerhalf_s *dev;  /* lower-half state */
+  mqd_t             usermq;   /* User mode app's message queue */
 };
 
 /****************************************************************************
@@ -98,10 +103,16 @@ static int      audio_open(FAR struct file *filep);
 static int      audio_close(FAR struct file *filep);
 static ssize_t  audio_read(FAR struct file *filep, FAR char *buffer, size_t buflen);
 static ssize_t  audio_write(FAR struct file *filep, FAR const char *buffer, size_t buflen);
-static int      audio_start(FAR struct audio_upperhalf_s *upper, unsigned int oflags);
 static int      audio_ioctl(FAR struct file *filep, int cmd, unsigned long arg);
+#ifdef CONFIG_AUDIO_MULTI_SESSION
+static int      audio_start(FAR struct audio_upperhalf_s *upper, FAR void *session);
+static void     audio_callback(FAR void *priv, uint16_t reason,
+                    FAR struct ap_buffer_s *apb, uint16_t status, FAR void *session);
+#else
+static int      audio_start(FAR struct audio_upperhalf_s *upper);
 static void     audio_callback(FAR void *priv, uint16_t reason,
                     FAR struct ap_buffer_s *apb, uint16_t status);
+#endif /* CONFIG_AUDIO_MULTI_SESSION */
 
 /****************************************************************************
  * Private Data
@@ -113,10 +124,10 @@ static const struct file_operations g_audioops =
   audio_close, /* close */
   audio_read,  /* read */
   audio_write, /* write */
-  0,         /* seek */
+  0,           /* seek */
   audio_ioctl  /* ioctl */
 #ifndef CONFIG_DISABLE_POLL
-  , 0        /* poll */
+  , 0          /* poll */
 #endif
 };
 
@@ -134,10 +145,10 @@ static const struct file_operations g_audioops =
 
 static int audio_open(FAR struct file *filep)
 {
-  FAR struct inode           *inode = filep->f_inode;
+  FAR struct inode *inode = filep->f_inode;
   FAR struct audio_upperhalf_s *upper = inode->i_private;
-  uint8_t                     tmp;
-  int                         ret;
+  uint8_t tmp;
+  int ret;
 
   audvdbg("crefs: %d\n", upper->crefs);
 
@@ -167,6 +178,7 @@ static int audio_open(FAR struct file *filep)
   /* Save the new open count on success */
 
   upper->crefs = tmp;
+  upper->usermq = NULL;
   ret = OK;
 
 errout_with_sem:
@@ -186,9 +198,9 @@ errout:
 
 static int audio_close(FAR struct file *filep)
 {
-  FAR struct inode           *inode = filep->f_inode;
+  FAR struct inode *inode = filep->f_inode;
   FAR struct audio_upperhalf_s *upper = inode->i_private;
-  int                         ret;
+  int ret;
 
   audvdbg("crefs: %d\n", upper->crefs);
 
@@ -243,7 +255,18 @@ errout:
 
 static ssize_t audio_read(FAR struct file *filep, FAR char *buffer, size_t buflen)
 {
-  /* Return zero -- usually meaning end-of-file */
+  FAR struct inode *inode = filep->f_inode;
+  FAR struct audio_upperhalf_s *upper = inode->i_private;
+  FAR struct audio_lowerhalf_s *lower = upper->dev;
+
+  /* TODO: Should we check permissions here? */
+
+  /* Audio read operations get passed directly to the lower-level */
+
+  if (lower->ops->read != NULL)
+    {
+      return lower->ops->read(lower, buffer, buflen);
+    }
 
   return 0;
 }
@@ -258,6 +281,19 @@ static ssize_t audio_read(FAR struct file *filep, FAR char *buffer, size_t bufle
 
 static ssize_t audio_write(FAR struct file *filep, FAR const char *buffer, size_t buflen)
 {
+  FAR struct inode *inode = filep->f_inode;
+  FAR struct audio_upperhalf_s *upper = inode->i_private;
+  FAR struct audio_lowerhalf_s *lower = upper->dev;
+
+  /* TODO: Should we check permissions here? */
+
+  /* Audio write operations get passed directly to the lower-level */
+
+  if (lower->ops->write != NULL)
+    {
+      return lower->ops->write(lower, buffer, buflen);
+    }
+
   return 0;
 }
 
@@ -269,7 +305,11 @@ static ssize_t audio_write(FAR struct file *filep, FAR const char *buffer, size_
  *
  ************************************************************************************/
 
-static int audio_start(FAR struct audio_upperhalf_s *upper, unsigned int oflags)
+#ifdef CONFIG_AUDIO_MULTI_SESSION
+static int audio_start(FAR struct audio_upperhalf_s *upper, FAR void *session)
+#else
+static int audio_start(FAR struct audio_upperhalf_s *upper)
+#endif
 {
   FAR struct audio_lowerhalf_s *lower = upper->dev;
   int ret = OK;
@@ -280,17 +320,21 @@ static int audio_start(FAR struct audio_upperhalf_s *upper, unsigned int oflags)
 
   if (!upper->started)
     {
-      /* Invoke the bottom half method to start the pulse train */
+      /* Invoke the bottom half method to start the audio stream */
 
+#ifdef CONFIG_AUDIO_MULTI_SESSION
+      ret = lower->ops->start(lower, session);
+#else
       ret = lower->ops->start(lower);
+#endif
 
-      /* A return value of zero means that the pulse train was started
+      /* A return value of zero means that the audio stream was started
        * successfully.
        */
 
       if (ret == OK)
         {
-          /* Indicate that the pulse train has started */
+          /* Indicate that the audio stream has started */
 
           upper->started = true;
         }
@@ -309,10 +353,14 @@ static int audio_start(FAR struct audio_upperhalf_s *upper, unsigned int oflags)
 
 static int audio_ioctl(FAR struct file *filep, int cmd, unsigned long arg)
 {
-  FAR struct inode           *inode = filep->f_inode;
+  FAR struct inode *inode = filep->f_inode;
   FAR struct audio_upperhalf_s *upper = inode->i_private;
   FAR struct audio_lowerhalf_s *lower = upper->dev;
-  int                         ret;
+  FAR struct audio_buf_desc_s  *bufdesc;
+#ifdef CONFIG_AUDIO_MULTI_SESSION
+  FAR void *session;
+#endif
+  int ret;
 
   audvdbg("cmd: %d arg: %ld\n", cmd, arg);
 
@@ -347,14 +395,19 @@ static int audio_ioctl(FAR struct file *filep, int cmd, unsigned long arg)
 
       case AUDIOIOC_CONFIGURE:
         {
-          FAR const struct audio_caps_s *caps = (FAR const struct audio_caps_s*)((uintptr_t)arg);
+          FAR const struct audio_caps_desc_s *caps =
+            (FAR const struct audio_caps_desc_s*)((uintptr_t)arg);
           DEBUGASSERT(lower->ops->configure != NULL);
 
-          audvdbg("AUDIOIOC_INITIALIZE: Device=%d", caps->ac_type);
+          audvdbg("AUDIOIOC_INITIALIZE: Device=%d", caps->caps.ac_type);
 
           /* Call the lower-half driver configure handler */
 
-          ret = lower->ops->configure(lower, caps, &audio_callback, upper);
+#ifdef CONFIG_AUDIO_MULTI_SESSION
+          ret = lower->ops->configure(lower, caps->session, &caps->caps);
+#else
+          ret = lower->ops->configure(lower, &caps->caps);
+#endif
         }
         break;
 
@@ -369,10 +422,10 @@ static int audio_ioctl(FAR struct file *filep, int cmd, unsigned long arg)
         }
         break;
 
-      /* AUDIOIOC_START - Start the pulsed output.  The AUDIOIOC_SETCHARACTERISTICS
+      /* AUDIOIOC_START - Start the audio stream.  The AUDIOIOC_SETCHARACTERISTICS
        *   command must have previously been sent.
        *
-       *   ioctl argument:  None
+       *   ioctl argument:  Audio session
        */
 
       case AUDIOIOC_START:
@@ -380,17 +433,23 @@ static int audio_ioctl(FAR struct file *filep, int cmd, unsigned long arg)
           audvdbg("AUDIOIOC_START\n");
           DEBUGASSERT(lower->ops->start != NULL);
 
-          /* Start the pulse train */
+          /* Start the audio stream */
 
-          ret = audio_start(upper, filep->f_oflags);
+#ifdef CONFIG_AUDIO_MULTI_SESSION
+          session = (FAR void *) arg;
+          ret = audio_start(upper, session);
+#else
+          ret = audio_start(upper);
+#endif
         }
         break;
 
-      /* AUDIOIOC_STOP - Stop the pulsed output.
+      /* AUDIOIOC_STOP - Stop the audio stream.
        *
-       *   ioctl argument:  None
+       *   ioctl argument:  Audio session
        */
 
+#ifndef CONFIG_AUDIO_EXCLUDE_STOP
       case AUDIOIOC_STOP:
         {
           audvdbg("AUDIOIOC_STOP\n");
@@ -398,11 +457,191 @@ static int audio_ioctl(FAR struct file *filep, int cmd, unsigned long arg)
 
           if (upper->started)
             {
+#ifdef CONFIG_AUDIO_MULTI_SESSION
+              session = (FAR void *) arg;
+              ret = lower->ops->stop(lower, session);
+#else
               ret = lower->ops->stop(lower);
+#endif
               upper->started = false;
             }
         }
         break;
+#endif  /* CONFIG_AUDIO_EXCLUDE_STOP */
+
+      /* AUDIOIOC_PAUSE - Pause the audio stream.
+       *
+       *   ioctl argument:  Audio session
+       */
+
+#ifndef CONFIG_AUDIO_EXCLUDE_PAUSE_RESUME
+
+      case AUDIOIOC_PAUSE:
+        {
+          audvdbg("AUDIOIOC_PAUSE\n");
+          DEBUGASSERT(lower->ops->pause != NULL);
+
+          if (upper->started)
+            {
+#ifdef CONFIG_AUDIO_MULTI_SESSION
+              session = (FAR void *) arg;
+              ret = lower->ops->pause(lower, session);
+#else
+              ret = lower->ops->pause(lower);
+#endif
+            }
+        }
+        break;
+
+      /* AUDIOIOC_RESUME - Resume the audio stream.
+       *
+       *   ioctl argument:  Audio session
+       */
+
+      case AUDIOIOC_RESUME:
+        {
+          audvdbg("AUDIOIOC_RESUME\n");
+          DEBUGASSERT(lower->ops->resume != NULL);
+
+          if (upper->started)
+            {
+#ifdef CONFIG_AUDIO_MULTI_SESSION
+              session = (FAR void *) arg;
+              ret = lower->ops->resume(lower, session);
+#else
+              ret = lower->ops->resume(lower);
+#endif
+            }
+        }
+        break;
+
+#endif  /* CONFIG_AUDIO_EXCLUDE_PAUSE_RESUME */
+
+      /* AUDIOIOC_ALLOCBUFFER - Allocate an audio buffer
+       *
+       *   ioctl argument:  pointer to an audio_buf_desc_s structure
+       */
+
+      case AUDIOIOC_ALLOCBUFFER:
+        {
+          audvdbg("AUDIOIOC_ALLOCBUFFER\n");
+
+          bufdesc = (FAR struct audio_buf_desc_s *) arg;
+          if (lower->ops->allocbuffer)
+            {
+              ret = lower->ops->allocbuffer(lower, bufdesc);
+            }
+          else
+            {
+              /* Perform a simple kumalloc operation assuming 1 session */
+
+              ret = apb_alloc(bufdesc);
+            }
+        }
+        break;
+
+      /* AUDIOIOC_FREEBUFFER - Free an audio buffer
+       *
+       *   ioctl argument:  pointer to an audio_buf_desc_s structure
+       */
+
+      case AUDIOIOC_FREEBUFFER:
+        {
+          audvdbg("AUDIOIOC_FREEBUFFER\n");
+
+          bufdesc = (FAR struct audio_buf_desc_s *) arg;
+          if (lower->ops->freebuffer)
+            {
+              ret = lower->ops->freebuffer(lower, bufdesc);
+            }
+          else
+            {
+              /* Perform a simple kufree operation */
+
+              DEBUGASSERT(bufdesc->u.pBuffer != NULL);
+              apb_free(bufdesc->u.pBuffer);
+              ret = sizeof(struct audio_buf_desc_s);
+            }
+        }
+        break;
+
+      /* AUDIOIOC_ENQUEUEBUFFER - Enqueue an audio buffer
+       *
+       *   ioctl argument:  pointer to an audio_buf_desc_s structure
+       */
+
+      case AUDIOIOC_ENQUEUEBUFFER:
+        {
+          audvdbg("AUDIOIOC_ENQUEUEBUFFER\n");
+
+          DEBUGASSERT(lower->ops->enqueuebuffer != NULL);
+
+          bufdesc = (FAR struct audio_buf_desc_s *) arg;
+          ret = lower->ops->enqueuebuffer(lower, bufdesc->u.pBuffer);
+        }
+        break;
+
+      /* AUDIOIOC_REGISTERMQ - Register a client Message Queue
+       *
+       * TODO:  This needs to have multi session support.
+       */
+
+      case AUDIOIOC_REGISTERMQ:
+        {
+          upper->usermq = (mqd_t) arg;
+          ret = OK;
+        }
+        break;
+
+      /* AUDIOIOC_UNREGISTERMQ - Register a client Message Queue
+       *
+       * TODO:  This needs to have multi session support.
+       */
+
+      case AUDIOIOC_UNREGISTERMQ:
+        {
+          upper->usermq = NULL;
+          ret = OK;
+        }
+        break;
+
+      /* AUDIOIOC_RESERVE - Reserve a session with the driver
+       *
+       *   ioctl argument - pointer to receive the session context
+       */
+
+      case AUDIOIOC_RESERVE:
+        {
+          DEBUGASSERT(lower->ops->reserve != NULL);
+
+          /* Call lower-half to perform the reservation */
+
+#ifdef CONFIG_AUDIO_MULTI_SESSION
+          ret = lower->ops->reserve(lower, (FAR void **) arg);
+#else
+          ret = lower->ops->reserve(lower);
+#endif
+        }
+        break;
+
+      /* AUDIOIOC_RESERVE - Reserve a session with the driver
+       *
+       *   ioctl argument - pointer to receive the session context
+       */
+
+      case AUDIOIOC_RELEASE:
+        {
+          DEBUGASSERT(lower->ops->release != NULL);
+
+          /* Call lower-half to perform the release */
+
+#ifdef CONFIG_AUDIO_MULTI_SESSION
+          ret = lower->ops->release(lower, (FAR void *) arg);
+#else
+          ret = lower->ops->release(lower);
+#endif
+        }
+        break;
 
       /* Any unrecognized IOCTL commands might be platform-specific ioctl commands */
 
@@ -420,6 +659,182 @@ static int audio_ioctl(FAR struct file *filep, int cmd, unsigned long arg)
 }
 
 /****************************************************************************
+ * Name: audio_dequeuebuffer
+ *
+ * Description:
+ *   Dequeues a previously enqueued Audio Pipeline Buffer.
+ *
+ *   1. The upper half driver calls the enqueuebuffer method, providing the
+ *      lower half driver with the ab_buffer to process.
+ *   2. The lower half driver's enqueuebuffer will either processes the
+ *      buffer directly, or more likely add it to a queue for processing
+ *      by a background thread or worker task.
+ *   3. When the lower half driver has completed processing of the enqueued
+ *      ab_buffer, it will call this routine to indicate processing of the
+ *      buffer is complete.
+ *   4. When this routine is called, it will check if any threads are waiting
+ *      to enqueue additional buffers and "wake them up" for further
+ *      processing.
+ *
+ * Input parameters:
+ *   handle - This is the handle that was provided to the lower-half
+ *     start() method.
+ *   apb - A pointer to the previsously enqueued ap_buffer_s
+ *   status - Status of the dequeue operation
+ *
+ * Returned Value:
+ *   None
+ *
+ * Assumptions:
+ *   This function may be called from an interrupt handler.
+ *
+ ****************************************************************************/
+
+#ifdef CONFIG_AUDIO_MULTI_SESSION
+static inline void audio_dequeuebuffer(FAR struct audio_upperhalf_s *upper,
+                    FAR struct ap_buffer_s *apb, uint16_t status,
+                    FAR void *session)
+#else
+static inline void audio_dequeuebuffer(FAR struct audio_upperhalf_s *upper,
+                    FAR struct ap_buffer_s *apb, uint16_t status)
+#endif
+{
+  struct audio_msg_s    msg;
+
+  audllvdbg("Entry\n");
+
+  /* Send a dequeue message to the user if a message queue is registered */
+
+  if (upper->usermq != NULL)
+    {
+      msg.msgId = AUDIO_MSG_DEQUEUE;
+      msg.u.pPtr = apb;
+#ifdef CONFIG_AUDIO_MULTI_SESSION
+      msg.session = session;
+#endif
+      apb->flags |= AUDIO_APB_DEQUEUED;
+      mq_send(upper->usermq, &msg, sizeof(msg), CONFIG_AUDIO_BUFFER_DEQUEUE_PRIO);
+    }
+}
+
+/****************************************************************************
+ * Name: audio_complete
+ *
+ * Description:
+ *   Send an AUDIO_MSG_COMPLETE message to the client to indicate that the
+ *   active playback has completed.  The lower-half driver initiates this
+ *   call via its callback pointer to our upper-half driver.
+ *
+ ****************************************************************************/
+
+#ifdef CONFIG_AUDIO_MULTI_SESSION
+static inline void audio_complete(FAR struct audio_upperhalf_s *upper,
+                    FAR struct ap_buffer_s *apb, uint16_t status,
+                    FAR void *session)
+#else
+static inline void audio_complete(FAR struct audio_upperhalf_s *upper,
+                    FAR struct ap_buffer_s *apb, uint16_t status)
+#endif
+{
+  struct audio_msg_s    msg;
+
+  audllvdbg("Entry\n");
+
+  /* Send a dequeue message to the user if a message queue is registered */
+
+  upper->started = false;
+  if (upper->usermq != NULL)
+    {
+      msg.msgId = AUDIO_MSG_COMPLETE;
+      msg.u.pPtr = NULL;
+#ifdef CONFIG_AUDIO_MULTI_SESSION
+      msg.session = session;
+#endif
+      mq_send(upper->usermq, &msg, sizeof(msg),
+          CONFIG_AUDIO_BUFFER_DEQUEUE_PRIO);
+    }
+}
+
+/****************************************************************************
+ * Name: audio_callback
+ *
+ * Description:
+ *   Provides a callback interface for lower-half drivers to call to the
+ *   upper-half for buffer dequeueing, error reporting, etc.
+ *
+ * Input parameters:
+ *   priv - Private context data owned by the upper-half
+ *   reason - The reason code for the callback
+ *   apb - A pointer to the previsously enqueued ap_buffer_s
+ *   status - Status information associated with the callback
+ *
+ * Returned Value:
+ *   None
+ *
+ * Assumptions:
+ *   This function may be called from an interrupt handler.
+ *
+ ****************************************************************************/
+
+#ifdef CONFIG_AUDIO_MULTI_SESSION
+static void audio_callback(FAR void *handle, uint16_t reason,
+        FAR struct ap_buffer_s *apb, uint16_t status,
+        FAR void *session)
+#else
+static void audio_callback(FAR void *handle, uint16_t reason,
+        FAR struct ap_buffer_s *apb, uint16_t status)
+#endif
+{
+  FAR struct audio_upperhalf_s *upper = (FAR struct audio_upperhalf_s *)handle;
+
+  audllvdbg("Entry\n");
+
+  /* Perform operation based on reason code */
+
+  switch (reason)
+    {
+      case AUDIO_CALLBACK_DEQUEUE:
+        {
+          /* Call the dequeue routine */
+
+#ifdef CONFIG_AUDIO_MULTI_SESSION
+          audio_dequeuebuffer(upper, apb, status, session);
+#else
+          audio_dequeuebuffer(upper, apb, status);
+#endif
+          break;
+        }
+
+      /* Lower-half I/O error occurred */
+
+      case AUDIO_CALLBACK_IOERR:
+        {
+        }
+        break;
+
+      /* Lower-half driver has completed a playback */
+
+      case AUDIO_CALLBACK_COMPLETE:
+        {
+          /* Send a complete message to the user if a message queue is registered */
+
+#ifdef CONFIG_AUDIO_MULTI_SESSION
+          audio_complete(upper, apb, status, session);
+#else
+          audio_complete(upper, apb, status);
+#endif
+        }
+        break;
+
+      default:
+        {
+          auddbg("Unknown callback reason code %d\n", reason);
+          break;
+        }
+    }
+}
+
+/****************************************************************************
  * Public Functions
  ****************************************************************************/
 
@@ -451,14 +866,14 @@ static int audio_ioctl(FAR struct file *filep, int cmd, unsigned long arg)
 int audio_register(FAR const char *name, FAR struct audio_lowerhalf_s *dev)
 {
   FAR struct audio_upperhalf_s *upper;
-  char  path[AUDIO_MAX_DEVICE_PATH];
+  char path[AUDIO_MAX_DEVICE_PATH];
   static bool dev_audio_created = false;
 #ifndef CONFIG_AUDIO_CUSTOM_DEV_PATH
   const char* devname = "/dev/audio";
 #elif !defined(CONFIG_AUDIO_DEV_ROOT)
   const char* devname = CONFIG_AUDIO_DEV_PATH;
   const char* ptr;
-  char*       pathptr;
+  char* pathptr;
 #endif
 
   /* Allocate the upper-half data structure */
@@ -570,102 +985,13 @@ int audio_register(FAR const char *name, FAR struct audio_lowerhalf_s *dev)
   strncat(path, name, AUDIO_MAX_DEVICE_PATH - 11);
 #endif
 
-  audvdbg("Registering %s\n", path);
-  return register_driver(path, &g_audioops, 0666, upper);
-}
+  /* Give the lower-half a context to the upper half */
 
-/****************************************************************************
- * Name: audio_dequeuebuffer
- *
- * Description:
- *   Dequeues a previously enqueued Audio Pipeline Buffer.
- *
- *   1. The upper half driver calls the enqueuebuffer method, providing the
- *      lower half driver with the ab_buffer to process.
- *   2. The lower half driver's enqueuebuffer will either processes the
- *      buffer directly, or more likely add it to a queue for processing
- *      by a background thread or worker task.
- *   3. When the lower half driver has completed processing of the enqueued
- *      ab_buffer, it will call this routine to indicated processing of the
- *      buffer is complete.
- *   4. When this routine is called, it will check if any threads are waiting
- *      to enqueue additional buffers and "wake them up" for further
- *      processing.
- *
- * Input parameters:
- *   handle - This is the handle that was provided to the lower-half
- *     start() method.
- *   apb - A pointer to the previsously enqueued ap_buffer_s
- *   status - Status of the dequeue operation
- *
- * Returned Value:
- *   None
- *
- * Assumptions:
- *   This function may be called from an interrupt handler.
- *
- ****************************************************************************/
-
-static inline void audio_dequeuebuffer(FAR struct audio_upperhalf_s *upper,
-                    FAR struct ap_buffer_s *apb, uint16_t status)
-{
-  audllvdbg("Entry\n");
-
-  /* TODO:  Implement the logic */
-
-}
-
-/****************************************************************************
- * Name: audio_callback
- *
- * Description:
- *   Provides a callback interface for lower-half drivers to call to the
- *   upper-half for buffer dequeueing, error reporting, etc.
- *
- * Input parameters:
- *   priv - Private context data owned by the upper-half
- *   reason - The reason code for the callback
- *   apb - A pointer to the previsously enqueued ap_buffer_s
- *   status - Status information associated with the callback
- *
- * Returned Value:
- *   None
- *
- * Assumptions:
- *   This function may be called from an interrupt handler.
- *
- ****************************************************************************/
-
-static void audio_callback(FAR void *handle, uint16_t reason,
-        FAR struct ap_buffer_s *apb, uint16_t status)
-{
-  FAR struct audio_upperhalf_s *upper = (FAR struct audio_upperhalf_s *)handle;
-
-  audllvdbg("Entry\n");
-
-  /* Perform operation based on reason code */
-
-  switch (reason)
-    {
-      case AUDIO_CALLBACK_DEQUEUE:
-        {
-          /* Call the dequeue routine */
-
-          audio_dequeuebuffer(upper, apb, status);
-          break;
-        }
-
-      case AUDIO_CALLBACK_IOERR:
-        {
-        }
-        break;
+  dev->upper = audio_callback;
+  dev->priv = upper;
 
-      default:
-        {
-          auddbg("Unknown callback reason code %d\n", reason);
-          break;
-        }
-    }
+  audvdbg("Registering %s\n", path);
+  return register_driver(path, &g_audioops, 0666, upper);
 }
 
 #endif /* CONFIG_AUDIO */
diff --git a/nuttx/audio/buffer.c b/nuttx/audio/buffer.c
index 3906891f6..b0b5c6c36 100644
--- a/nuttx/audio/buffer.c
+++ b/nuttx/audio/buffer.c
@@ -84,11 +84,11 @@
  *
  ****************************************************************************/
 
-static void apb_semtake(sem_t *sem)
+static void apb_semtake(FAR struct ap_buffer_s *apb)
 {
   /* Take the semaphore (perhaps waiting) */
 
-  while (sem_wait(sem) != 0)
+  while (sem_wait(&apb->sem) != 0)
     {
       /* The only case that an error should occr here is if
        * the wait was awakened by a signal.
@@ -102,7 +102,7 @@ static void apb_semtake(sem_t *sem)
  * Name: apb_semgive
  ****************************************************************************/
 
-#define apb_semgive(s) sem_post(s)
+#define apb_semgive(b) sem_post(&b->sem)
 
 /****************************************************************************
  * Name: apb_alloc
@@ -113,11 +113,41 @@ static void apb_semtake(sem_t *sem)
  *
  ****************************************************************************/
 
-FAR struct ap_buffer_s *apb_alloc(int type, int sampleCount)
+int apb_alloc(FAR struct audio_buf_desc_s * bufdesc)
 {
-  /* TODO:  Implement the alloc logic */
+  uint32_t            bufsize;
+  int                 ret;
+  struct ap_buffer_s  *pBuf;
 
-  return NULL;
+  DEBUGASSERT(bufdesc->u.ppBuffer != NULL);
+
+  /* Perform a user mode allocation */
+
+  bufsize = sizeof(struct ap_buffer_s) + bufdesc->numbytes;
+  pBuf = kumalloc(bufsize);
+  *bufdesc->u.ppBuffer = pBuf;
+
+  /* Test if the allocation was successful or not */
+
+  if (*bufdesc->u.ppBuffer == NULL)
+    ret = -ENOMEM;
+  else
+    {
+      /* Populate the buffer contents */
+
+      memset(pBuf, bufsize, 0);
+      pBuf->i.channels = 1;
+      pBuf->crefs = 1;
+      pBuf->nmaxbytes = bufdesc->numbytes;
+      pBuf->nbytes = 0;
+#ifdef CONFIG_AUDIO_MULTI_SESSION
+      pBuf->session = bufdesc->session;
+#endif
+      sem_init(&pBuf->sem, 0, 1);
+      ret = sizeof(struct audio_buf_desc_s);
+    }
+
+  return ret;
 }
 
 /****************************************************************************
@@ -143,8 +173,19 @@ void apb_prepare(FAR struct ap_buffer_s *apb, int8_t allocmode, uint8_t format,
 
 void apb_free(FAR struct ap_buffer_s *apb)
 {
+  int   refcount;
+
   /* Perform a reference count decrement and possibly release the memory */
 
+  apb_semtake(apb);
+  refcount = apb->crefs--;
+  apb_semgive(apb);
+
+  if (refcount == 1)
+    {
+      auddbg("Freeing %p\n", apb);
+      kufree(apb);
+    }
 }
 
 /****************************************************************************
@@ -158,7 +199,11 @@ void apb_free(FAR struct ap_buffer_s *apb)
 
 void apb_reference(FAR struct ap_buffer_s *apb)
 {
-  /* TODO:  Implement the reference logic */
+  /* Do we need any thread protection here?  Almost certaily... */
+
+  apb_semtake(apb);
+  apb->crefs++;
+  apb_semgive(apb);
 }
 
 #endif /* CONFIG_AUDIO */