Add new framework for the PCM decoder. It is now a 'front end' for lower-level drivers like the WM8904 that performs the PCM decoding from end

4 files changed, 571 insertions, 101 deletions

diff --git a/nuttx/audio/Makefile b/nuttx/audio/Makefile
index b95e3900b..33b3a26a7 100644
--- a/nuttx/audio/Makefile
+++ b/nuttx/audio/Makefile
@@ -50,7 +50,7 @@ VPATH = .
 # the appropriate paths to the VPATH variable
 
 ifeq ($(CONFIG_AUDIO_FORMAT_PCM),y)
-  CSRCS += pcm.c
+  CSRCS += pcm_decode.c
 endif
 
 AOBJS = $(ASRCS:.S=$(OBJEXT))
diff --git a/nuttx/audio/README.txt b/nuttx/audio/README.txt
index be86cacb0..85ab2e1a3 100644
--- a/nuttx/audio/README.txt
+++ b/nuttx/audio/README.txt
@@ -17,12 +17,12 @@ This directory holds the NuttX audio subsystem upper-half.  The upper-half provi
 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.
-  pcm.c     - Routines to manage PCM / WAV type data.  Currently just a placeholder.
-  README    - This file!
+  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.
+  pcm_decode.c - Routines to decode PCM / WAV type data.
+  README       - This file!
 
 Portions of the the audio system interface have application interfaces.  Those
 portions reside in the nuttx/libc/audio directory where the will be built for
diff --git a/nuttx/audio/pcm.c b/nuttx/audio/pcm.c
deleted file mode 100644
index aeb1b7b64..000000000
--- a/nuttx/audio/pcm.c
+++ /dev/null
@@ -1,94 +0,0 @@
-/****************************************************************************
- * audio/pcm.c
- *
- *   Copyright (C) 2013 Ken Pettit. All rights reserved.
- *   Author: Ken Pettit <pettitkd@gmail.com>
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- *
- * 1. Redistributions of source code must retain the above copyright
- *    notice, this list of conditions and the following disclaimer.
- * 2. Redistributions in binary form must reproduce the above copyright
- *    notice, this list of conditions and the following disclaimer in
- *    the documentation and/or other materials provided with the
- *    distribution.
- * 3. Neither the name NuttX nor the names of its contributors may be
- *    used to endorse or promote products derived from this software
- *    without specific prior written permission.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
- * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
- * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
- * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
- * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
- * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
- * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
- * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
- * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
- * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
- * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
- * POSSIBILITY OF SUCH DAMAGE.
- *
- ****************************************************************************/
-
-/****************************************************************************
- * Included Files
- ****************************************************************************/
-
-#include <nuttx/config.h>
-
-#include <sys/types.h>
-#include <stdint.h>
-#include <stdbool.h>
-#include <stdlib.h>
-#include <string.h>
-#include <assert.h>
-#include <semaphore.h>
-#include <errno.h>
-#include <debug.h>
-
-#include <nuttx/kmalloc.h>
-#include <nuttx/audio/audio.h>
-
-#if defined(CONFIG_AUDIO) && defined(CONFIG_AUDIO_FORMAT_PCM)
-
-/****************************************************************************
- * Preprocessor Definitions
- ****************************************************************************/
-
-/* Configuration ************************************************************/
-
-/****************************************************************************
- * Private Types
- ****************************************************************************/
-
-/****************************************************************************
- * Private Variables
- ****************************************************************************/
-
-/****************************************************************************
- * Public Variables
- ****************************************************************************/
-
-/****************************************************************************
- * Private Functions
- ****************************************************************************/
-
-/****************************************************************************
- * Name: audio_pcm_init
- *
- * Initialized the Audio PCM library.
- *
- ****************************************************************************/
-
-int audio_pcm_initialize(void)
-{
-  /* Initialze the Audio PCM routines */
-
-  return OK;
-}
-
-#endif /* CONFIG_AUDIO && CONFIG_AUDIO_FORMAT_PCM */
-
diff --git a/nuttx/audio/pcm_decode.c b/nuttx/audio/pcm_decode.c
new file mode 100644
index 000000000..ba817a313
--- /dev/null
+++ b/nuttx/audio/pcm_decode.c
@@ -0,0 +1,564 @@
+/****************************************************************************
+ * audio/pcm_decode.c
+ *
+ *   Copyright (C) 2014 Gregory Nutt. All rights reserved.
+ *   Author:  Gregory Nutt <gnutt@nuttx.org>
+ *
+ * Based on the original audio framework from:
+ *
+ *   Author: Ken Pettit <pettitkd@gmail.com>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name NuttX nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <sys/types.h>
+#include <stdint.h>
+#include <stdbool.h>
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+#include <semaphore.h>
+#include <errno.h>
+#include <debug.h>
+
+#include <nuttx/kmalloc.h>
+#include <nuttx/audio/audio.h>
+#include <nuttx/audio/pcm_decode.h>
+
+#if defined(CONFIG_AUDIO) && defined(CONFIG_AUDIO_FORMAT_PCM)
+
+/****************************************************************************
+ * Pre-processor Definitions
+ ****************************************************************************/
+
+/* Configuration ************************************************************/
+
+/****************************************************************************
+ * Private Types
+ ****************************************************************************/
+/* This structure describes the internal state of the PCM decoder */
+
+struct pcm_decode_s
+{
+  /* This is is our our appearance to the outside world.  This *MUST* be the
+   * first element of the structure so that we can freely cast between types
+   * struct audio_lowerhalf and struct pcm_decode_s.
+   */
+
+  struct audio_lowerhalf_s export;
+
+  /* These are our operations that intervene between the player application
+   * and the lower level driver.  Unlike the ops in the struct
+   * audio_lowerhalf_s, these are writeable because we need to customize a
+   * few of the methods based upon what is supported by the the lower level
+   * driver.
+   */
+
+  struct audio_ops_s ops;
+
+  /* This is the contained, low-level DAC-type device and will receive the
+   * decoded PCM audio data.
+   */
+
+  FAR struct audio_lowerhalf_s *lower;
+};
+
+/****************************************************************************
+ * Private Function Prototypes
+ ****************************************************************************/
+
+/* struct audio_lowerhalf_s methods *****************************************/
+
+static int  pcm_getcaps(FAR struct audio_lowerhalf_s *dev, int type,
+              FAR struct audio_caps_s *caps);
+
+#ifdef CONFIG_AUDIO_MULTI_SESSION
+static int  pcm_configure(FAR struct audio_lowerhalf_s *dev,
+              FAR void *session, FAR const struct audio_caps_s *caps);
+#else
+static int  pcm_configure(FAR struct audio_lowerhalf_s *dev,
+              FAR const struct audio_caps_s *caps);
+#endif
+
+static int  pcm_shutdown(FAR struct audio_lowerhalf_s *dev);
+
+#ifdef CONFIG_AUDIO_MULTI_SESSION
+static int  pcm_start(FAR struct audio_lowerhalf_s *dev, FAR void *session);
+#else
+static int  pcm_start(FAR struct audio_lowerhalf_s *dev);
+#endif
+
+#ifndef CONFIG_AUDIO_EXCLUDE_STOP
+#ifdef CONFIG_AUDIO_MULTI_SESSION
+static int  pcm_stop(FAR struct audio_lowerhalf_s *dev, FAR void *session);
+#else
+static int  pcm_stop(FAR struct audio_lowerhalf_s *dev);
+#endif
+#endif
+
+#ifndef CONFIG_AUDIO_EXCLUDE_PAUSE_RESUME
+#ifdef CONFIG_AUDIO_MULTI_SESSION
+static int  pcm_pause(FAR struct audio_lowerhalf_s *dev, FAR void *session);
+#else
+static int  pcm_pause(FAR struct audio_lowerhalf_s *dev);
+#endif
+
+#ifdef CONFIG_AUDIO_MULTI_SESSION
+static int  pcm_resume(FAR struct audio_lowerhalf_s *dev, FAR void *session);
+#else
+static int  pcm_resume(FAR struct audio_lowerhalf_s *dev);
+#endif
+#endif
+
+static int  pcm_allocbuffer(FAR struct audio_lowerhalf_s *dev,
+              FAR struct audio_buf_desc_s *apb);
+static int  pcm_freebuffer(FAR struct audio_lowerhalf_s *dev,
+              FAR struct audio_buf_desc_s *apb);
+static int  pcm_enqueuebuffer(FAR struct audio_lowerhalf_s *dev,
+              FAR struct ap_buffer_s *apb);
+static int  pcm_cancelbuffer(FAR struct audio_lowerhalf_s *dev,
+              FAR struct ap_buffer_s *apb);
+static int  pcm_ioctl(FAR struct audio_lowerhalf_s *dev,
+              int cmd, unsigned long arg);
+
+#ifdef CONFIG_AUDIO_MULTI_SESSION
+static int  pcm_reserve(FAR struct audio_lowerhalf_s *dev, FAR void **session);
+#else
+static int  pcm_reserve(FAR struct audio_lowerhalf_s *dev);
+#endif
+
+#ifdef CONFIG_AUDIO_MULTI_SESSION
+static int  pcm_release(FAR struct audio_lowerhalf_s *dev, FAR void *session);
+#else
+static int  pcm_release(FAR struct audio_lowerhalf_s *dev);
+#endif
+
+/****************************************************************************
+ * Private Data
+ ****************************************************************************/
+
+/****************************************************************************
+ * Public Data
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: pcm_getcaps
+ *
+ * Description:
+ *    This method is called to retrieve the lower-half device capabilities.
+ *    It will be called with device type AUDIO_TYPE_QUERY to request the
+ *    overall capabilities, such as to determine the types of devices supported
+ *    audio formats supported, etc.  Then it may be called once or more with
+ *    reported supported device types to determine the specific capabilities
+ *    of that device type (such as MP3 encoder, WMA encoder, PCM output, etc.).
+ *
+ ****************************************************************************/
+
+static int pcm_getcaps(FAR struct audio_lowerhalf_s *dev, int type,
+                       FAR struct audio_caps_s *caps)
+{
+  FAR struct pcm_decode_s *priv = (FAR struct pcm_decode_s *)dev;
+#warning Missing logic
+  return -ENOSYS;
+}
+
+/****************************************************************************
+ * Name: pcm_configure
+ *
+ * Description:
+ *    This method is called to bind the lower-level driver to the upper-level
+ *    driver and to configure the driver for a specific mode of
+ *    operation defined by the parameters selected in supplied device caps
+ *    structure.  The lower-level device should perform any initialization
+ *    needed to prepare for operations in the specified mode.  It should not,
+ *    however, process any audio data until the start method is called.
+ *
+ ****************************************************************************/
+
+#ifdef CONFIG_AUDIO_MULTI_SESSION
+static int pcm_configure(FAR struct audio_lowerhalf_s *dev,
+                         FAR void *session, FAR const struct audio_caps_s *caps)
+#else
+static int pcm_configure(FAR struct audio_lowerhalf_s *dev,
+                         FAR const struct audio_caps_s *caps)
+#endif
+{
+  FAR struct pcm_decode_s *priv = (FAR struct pcm_decode_s *)dev;
+#warning Missing logic
+  return -ENOSYS;
+}
+
+/****************************************************************************
+ * Name: pcm_shutdown
+ *
+ * Description:
+ *    This method is called when the driver is closed.  The lower half driver
+ *    should stop processing audio data, including terminating any active
+ *    output generation.  It should also disable the audio hardware and put
+ *    it into the lowest possible power usage state.
+ *
+ *    Any enqueued Audio Pipeline Buffers that have not been processed / dequeued
+ *    should be dequeued by this function.
+ *
+ ****************************************************************************/
+
+static int pcm_shutdown(FAR struct audio_lowerhalf_s *dev)
+{
+  FAR struct pcm_decode_s *priv = (FAR struct pcm_decode_s *)dev;
+#warning Missing logic
+  return -ENOSYS;
+}
+
+/****************************************************************************
+ * Name: pcm_start
+ *
+ * Description:
+ *    Start audio streaming in the configured mode.  For input and synthesis
+ *    devices, this means it should begin sending streaming audio data.  For output
+ *    or processing type device, it means it should begin processing of any enqueued
+ *    Audio Pipeline Buffers.
+ *
+ ****************************************************************************/
+
+#ifdef CONFIG_AUDIO_MULTI_SESSION
+static int pcm_start(FAR struct audio_lowerhalf_s *dev, FAR void *session)
+#else
+static int pcm_start(FAR struct audio_lowerhalf_s *dev)
+#endif
+{
+  FAR struct pcm_decode_s *priv = (FAR struct pcm_decode_s *)dev;
+#warning Missing logic
+  return -ENOSYS;
+}
+
+/****************************************************************************
+ * Name: pcm_stop
+ *
+ * Description:
+ *    Stop audio streaming and/or processing of enqueued Audio Pipeline
+ *    Buffers
+ *
+ ****************************************************************************/
+
+#ifndef CONFIG_AUDIO_EXCLUDE_STOP
+#ifdef CONFIG_AUDIO_MULTI_SESSION
+static int pcm_stop(FAR struct audio_lowerhalf_s *dev, FAR void *session)
+#else
+static int pcm_stop(FAR struct audio_lowerhalf_s *dev)
+#endif
+#endif
+{
+  FAR struct pcm_decode_s *priv = (FAR struct pcm_decode_s *)dev;
+#warning Missing logic
+  return -ENOSYS;
+}
+
+/****************************************************************************
+ * Name: pcm_pause
+ *
+ * Description:
+ *    Pause the audio stream.  Should keep current playback context active
+ *    in case a resume is issued.  Could be called and then followed by a stop.
+ *
+ ****************************************************************************/
+
+#ifndef CONFIG_AUDIO_EXCLUDE_PAUSE_RESUME
+#ifdef CONFIG_AUDIO_MULTI_SESSION
+static int pcm_pause(FAR struct audio_lowerhalf_s *dev, FAR void *session)
+#else
+static int pcm_pause(FAR struct audio_lowerhalf_s *dev)
+#endif
+{
+  FAR struct pcm_decode_s *priv = (FAR struct pcm_decode_s *)dev;
+#warning Missing logic
+  return -ENOSYS;
+}
+
+/****************************************************************************
+ * Name: pcm_resume
+ *
+ * Description:
+ *    Resumes audio streaming after a pause.
+ *
+ ****************************************************************************/
+
+#ifdef CONFIG_AUDIO_MULTI_SESSION
+static int pcm_resume(FAR struct audio_lowerhalf_s *dev, FAR void *session)
+#else
+static int pcm_resume(FAR struct audio_lowerhalf_s *dev)
+#endif
+#endif
+{
+  FAR struct pcm_decode_s *priv = (FAR struct pcm_decode_s *)dev;
+#warning Missing logic
+  return -ENOSYS;
+}
+
+/****************************************************************************
+ * Name: pcm_allocbuffer
+ *
+ * Description:
+ *    Allocate an audio pipeline buffer.  This routine provides the
+ *    lower-half driver with the opportunity to perform special buffer
+ *    allocation if needed, such as allocating from a specific memory
+ *    region (DMA-able, etc.).  If not supplied, then the top-half
+ *    driver will perform a standard kumalloc using normal user-space
+ *    memory region.
+ *
+ ****************************************************************************/
+
+static int pcm_allocbuffer(FAR struct audio_lowerhalf_s *dev,
+                           FAR struct audio_buf_desc_s *apb)
+{
+  FAR struct pcm_decode_s *priv = (FAR struct pcm_decode_s *)dev;
+  FAR struct audio_lowerhalf_s *lower;
+
+  DEBUGASSERT(priv);
+
+  /* Defer the operation to the lower device driver */
+
+  lower = priv->lower;
+  DEBUGASSERT(lower && lower->ops->allocbuffer);
+  return lower->ops->allocbuffer(lower, apb);
+}
+
+/****************************************************************************
+ * Name: pcm_freebuffer
+ *
+ * Description:
+ *    Free an audio pipeline buffer.  If the lower-level driver
+ *    provides an allocbuffer routine, it should also provide the
+ *    freebuffer routine to perform the free operation.
+ *
+ ****************************************************************************/
+
+static int pcm_freebuffer(FAR struct audio_lowerhalf_s *dev,
+                          FAR struct audio_buf_desc_s *apb)
+{
+  FAR struct pcm_decode_s *priv = (FAR struct pcm_decode_s *)dev;
+  FAR struct audio_lowerhalf_s *lower;
+
+  DEBUGASSERT(priv);
+
+  /* Defer the operation to the lower device driver */
+
+  lower = priv->lower;
+  DEBUGASSERT(lower && lower->ops->freebuffer);
+  return lower->ops->freebuffer(lower, apb);
+}
+
+/****************************************************************************
+ * Name: pcm_enqueuebuffer
+ *
+ * Description:
+ *    Enqueue a buffer for processing.  This is a non-blocking enqueue operation.
+ *    If the lower-half driver's buffer queue is full, then it should return an
+ *    error code of -ENOMEM, and the upper-half driver can decide to either block
+ *    the calling thread or deal with it in a non-blocking manner.
+ *
+ *    For each call to enqueuebuffer, the lower-half driver must call
+ *    audio_dequeuebuffer when it is finished processing the bufferr, passing the
+ *    previously enqueued apb and a dequeue status so that the upper-half driver
+ *    can decide if a waiting thread needs to be release, if the dequeued buffer
+ *    should be passed to the next block in the Audio Pipeline, etc.
+ *
+ ****************************************************************************/
+
+static int pcm_enqueuebuffer(FAR struct audio_lowerhalf_s *dev,
+                             FAR struct ap_buffer_s *apb)
+{
+  FAR struct pcm_decode_s *priv = (FAR struct pcm_decode_s *)dev;
+#warning Missing logic
+  return -ENOSYS;
+}
+
+/****************************************************************************
+ * Name: pcm_cancelbuffer
+ *
+ * Description:
+ *    Cancel a previously enqueued buffer.
+ *
+ ****************************************************************************/
+
+static int pcm_cancelbuffer(FAR struct audio_lowerhalf_s *dev,
+                            FAR struct ap_buffer_s *apb)
+{
+  FAR struct pcm_decode_s *priv = (FAR struct pcm_decode_s *)dev;
+#warning Missing logic
+  return -ENOSYS;
+}
+
+/****************************************************************************
+ * Name: pcm_ioctl
+ *
+ * Description:
+ *    Lower-half logic may support platform-specific ioctl commands.
+ *
+ ****************************************************************************/
+
+static int pcm_ioctl(FAR struct audio_lowerhalf_s *dev,
+                     int cmd, unsigned long arg)
+{
+  FAR struct pcm_decode_s *priv = (FAR struct pcm_decode_s *)dev;
+#warning Missing logic
+  return -ENOSYS;
+}
+
+/****************************************************************************
+ * Name: pcm_reserve
+ *
+ * Description:
+ *    Reserve a session (may only be one per device or may be multiple) for
+ *    use by a client.  Client software can open audio devices and issue
+ *    AUDIOIOC_GETCAPS calls freely, but other operations require a
+ *    reservation.  A session reservation will assign a context that must
+ *    be passed with
+ *
+ ****************************************************************************/
+
+#ifdef CONFIG_AUDIO_MULTI_SESSION
+static int pcm_reserve(FAR struct audio_lowerhalf_s *dev, FAR void **session)
+#else
+static int pcm_reserve(FAR struct audio_lowerhalf_s *dev)
+#endif
+{
+  FAR struct pcm_decode_s *priv = (FAR struct pcm_decode_s *)dev;
+#warning Missing logic
+  return -ENOSYS;
+}
+
+/****************************************************************************
+ * Name: pcm_release
+ *
+ * Description:
+ *    Release a session.
+ *
+ ****************************************************************************/
+
+#ifdef CONFIG_AUDIO_MULTI_SESSION
+static int pcm_release(FAR struct audio_lowerhalf_s *dev, FAR void *session)
+#else
+static int pcm_release(FAR struct audio_lowerhalf_s *dev)
+#endif
+{
+  FAR struct pcm_decode_s *priv = (FAR struct pcm_decode_s *)dev;
+#warning Missing logic
+  return -ENOSYS;
+}
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: pcm_decode_initialize
+ *
+ * Description:
+ *   Initialize the PCM device.  The PCM device accepts and contains a
+ *   low-level audio DAC-type device.  It then returns a new audio lower
+ *   half interface at adds a PCM decoding from end to the low-level
+ *   audio device
+ *
+ * Input Parameters:
+ *   dev - A reference to the low-level audio DAC-type device to contain.
+ *
+ * Returned Value:
+ *   On success, a new audio device instance is returned that wraps the
+ *   low-level device and provides a PCM decoding front end.  NULL is
+ *   returned on failure.
+ *
+ ****************************************************************************/
+
+FAR struct audio_lowerhalf_s *
+  pcm_decode_initialize(FAR struct audio_lowerhalf_s *dev)
+{
+  FAR struct pcm_decode_s *priv;
+  FAR struct audio_ops_s *ops;
+
+  /* Allocate an instance of our private data structure */
+
+  priv = (FAR struct pcm_decode_s *)kzalloc(sizeof(struct pcm_decode_s));
+  if (!priv)
+    {
+      auddbg("ERROR: Failed to allocate driver structure\n");
+      return NULL;
+    }
+
+  /* Initialize our private data structure.  Since kzalloc() was used for
+   * the allocation, we need to initialize only non-zero, non-NULL, non-
+   * false fields.
+   */
+
+  ops                  = &priv->ops;
+  ops->getcaps         = pcm_getcaps;
+  ops->configure       = pcm_configure;
+  ops->shutdown        = pcm_shutdown;
+  ops->start           = pcm_start;
+
+#ifndef CONFIG_AUDIO_EXCLUDE_STOP
+  ops->stop            = pcm_stop;
+#endif
+
+#ifndef CONFIG_AUDIO_EXCLUDE_PAUSE_RESUME
+  ops->pause           = pcm_pause;
+  ops->resume          = pcm_resume;
+#endif
+
+  if (dev->ops->allocbuffer)
+    {
+      DEBUGASSERT(dev->ops->freebuffer);
+      ops->allocbuffer = pcm_allocbuffer;
+      ops->freebuffer  = pcm_freebuffer;
+    }
+
+  ops->enqueuebuffer   = pcm_enqueuebuffer;
+  ops->cancelbuffer    = pcm_cancelbuffer;
+  ops->ioctl           = pcm_ioctl;
+  ops->reserve         = pcm_reserve;
+  ops->release         = pcm_release;
+
+  priv->export.ops     = &priv->ops;
+  priv->export.priv    = priv;
+  priv->lower          = dev;
+
+  return &priv->export;
+}
+
+#endif /* CONFIG_AUDIO && CONFIG_AUDIO_FORMAT_PCM */
+