Framework for a WM8904 audio driver. The initial driver check-in is simply Ken Pettit's VS1053 driver forced to compile with only WM8904 definitions

4 files changed, 1578 insertions, 6 deletions

diff --git a/nuttx/drivers/audio/Kconfig b/nuttx/drivers/audio/Kconfig
index b94df1d3d..3e51751f9 100644
--- a/nuttx/drivers/audio/Kconfig
+++ b/nuttx/drivers/audio/Kconfig
@@ -82,3 +82,25 @@ config VS1053_BUFFER_SIZE
 endif # AUDIO_DRIVER_SPECIFIC_BUFFERS
 
 endif # VS1053
+
+config AUDIO_WM8904
+	bool "WM8904 audio chip"
+	default n
+	depends on EXPERIMENTAL
+	---help---
+		Select to enable support for the WM8904 Audio codec by Wolfson
+		Microelectonics.  This chip is a lower level audio chip.. basically
+		an exotic D-to-A.  It includes no builtin support for audion CODECS
+		The WM8904 provides:
+
+			- Low power consumption
+			- High SNR
+			- Stereo digital microphone input
+			- Digital Dynamic Range Controller (compressor / limiter)
+			- Digital sidetone mixing
+			- Ground-referenced headphone driver
+			- Ground-referenced line outputs
+
+if AUDIO_WM8904
+endif # AUDIO_WM8904
+
diff --git a/nuttx/drivers/audio/Make.defs b/nuttx/drivers/audio/Make.defs
index 2dd8c8d4c..72bb16b1a 100644
--- a/nuttx/drivers/audio/Make.defs
+++ b/nuttx/drivers/audio/Make.defs
@@ -37,12 +37,16 @@
 
 # Include Audio drivers
 
-ifeq ($(CONFIG_AUDIO),y)
+ifeq ($(CONFIG_AUDIO_DEVICES),y)
 
 ifeq ($(CONFIG_VS1053),y)
 CSRCS += vs1053.c
 endif
 
+ifeq ($(CONFIG_AUDIO_WM8904),y)
+CSRCS += wm8904.c
+endif
+
 ifeq ($(CONFIG_AUDIO_I2SCHAR),y)
 CSRCS += i2schar.c
 endif
diff --git a/nuttx/drivers/audio/wm8904.c b/nuttx/drivers/audio/wm8904.c
new file mode 100644
index 000000000..85ca5eea4
--- /dev/null
+++ b/nuttx/drivers/audio/wm8904.c
@@ -0,0 +1,1546 @@
+/****************************************************************************
+ * drivers/audio/wm8904.c
+ *
+ * Audio device driver for Wolfson Microelectronics WM8904 Audio codec.
+ *
+ *   Copyright (C) 2014 Gregory Nutt. All rights reserved.
+ *   Author:  Gregory Nutt <gnutt@nuttx.org>
+ *
+ * Reference:
+ *   "WM8904 Ultra Low Power CODEC for Portable Audio Applications, Pre-
+ *    Production", September 2012, Rev 3.3, Wolfson Microelectronics
+ *
+ * The framework for this driver is based on Ken Pettit's VS1053 driver.
+ *
+ * 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 <sys/ioctl.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <fcntl.h>
+#include <string.h>
+#include <debug.h>
+#include <errno.h>
+#include <queue.h>
+
+#include <nuttx/kmalloc.h>
+#include <nuttx/i2c.h>
+#include <nuttx/fs/fs.h>
+#include <nuttx/fs/ioctl.h>
+#include <nuttx/audio/i2s.h>
+#include <nuttx/audio/audio.h>
+#include <nuttx/audio/wm8904.h>
+#include <nuttx/math.h>
+
+#include "wm8904.h"
+
+/****************************************************************************
+ * Private Definitions
+ ****************************************************************************/
+
+#ifndef CONFIG_WM8904_XTALI
+#  define CONFIG_WM8904_XTALI             12288000
+#endif
+
+#ifndef CONFIG_WM8904_MP3_DECODE_FREQ
+#  define CONFIG_WM8904_MP3_DECODE_FREQ   43000000
+#endif
+
+#ifndef CONFIG_WM8904_MSG_PRIO
+#  define CONFIG_WM8904_MSG_PRIO          1
+#endif
+
+#ifndef CONFIG_WM8904_BUFFER_SIZE
+#  define CONFIG_WM8904_BUFFER_SIZE       8192
+#endif
+
+#ifndef CONFIG_WM8904_NUM_BUFFERS
+#  define CONFIG_WM8904_NUM_BUFFERS       2
+#endif
+
+#ifndef CONFIG_WM8904_WORKER_STACKSIZE
+#  define CONFIG_WM8904_WORKER_STACKSIZE  768
+#endif
+
+#define WM8904_DUMMY                      0xFF
+#define WM8904_DEFAULT_XTALI              12288000
+#define WM8904_DATA_FREQ                  20000000
+#define WM8904_RST_USECS                  2000
+
+/****************************************************************************
+ * Private Types
+ ****************************************************************************/
+
+struct wm8904_dev_s
+{
+  /* We are an audio lower half driver (We are also the upper "half" of
+   * the WM8904 driver with respect to the board lower half driver).
+   *
+   * Terminology: Our "lower" half audio instances will be called dev for the
+   * publicly visible version and "priv" for the version that only this driver
+   * knows.  From the point of view of this driver, it is the board lower
+   * "half" that is referred to as "lower".
+   */
+
+  struct audio_lowerhalf_s dev;             /* WM8904 audio lower half (this drive) */
+
+  /* Our specific driver data goes here */
+
+  const FAR struct wm8904_lower_s *lower;   /* Pointer to the board lower functions */
+  FAR struct i2c_dev_s   *i2c;              /* I2C driver to use */
+  FAR struct i2s_dev_s   *i2s;              /* I2S driver to use */
+  FAR struct ap_buffer_s *apb;              /* Pointer to the buffer we are processing */
+  struct dq_queue_s       apbq;             /* Our queue for enqueued buffers */
+  unsigned long           frequency;        /* Frequency to run the I2C bus at. */
+  unsigned long           actual;           /* Current chip frequency */
+  mqd_t                   mq;               /* Message queue for receiving messages */
+  char                    mqname[16];       /* Our message queue name */
+  pthread_t               threadid;         /* ID of our thread */
+  sem_t                   apbq_sem;         /* Audio Pipeline Buffer Queue sem access */
+#ifndef CONFIG_AUDIO_EXCLUDE_VOLUME
+  int16_t                 volume;           /* Current volume level */
+#ifndef CONFIG_AUDIO_EXCLUDE_BALANCE
+  int16_t                 balance;          /* Current balance level */
+#endif  /* CONFIG_AUDIO_EXCLUDE_BALANCE */
+#endif  /* CONFIG_AUDIO_EXCLUDE_VOLUME */
+#ifndef CONFIG_AUDIO_EXCLUDE_TONE
+  uint8_t                 bass;             /* Bass level */
+  uint8_t                 treble;           /* Bass level */
+#endif
+  uint16_t                endfillbytes;
+  uint8_t                 endfillchar;      /* Fill char to send when no more data */
+  uint8_t                 running;
+  uint8_t                 paused;
+  uint8_t                 endmode;
+#ifndef CONFIG_AUDIO_EXCLUDE_STOP
+  uint8_t                 cancelmode;
+#endif
+  uint8_t                 busy;             /* Set true when device reserved */
+};
+
+/****************************************************************************
+ * Private Function Prototypes
+ ****************************************************************************/
+
+static int     wm8904_getcaps(FAR struct audio_lowerhalf_s *dev, int type,
+                 FAR struct audio_caps_s *caps);
+static int     wm8904_shutdown(FAR struct audio_lowerhalf_s *dev);
+#ifdef CONFIG_AUDIO_MULTI_SESSION
+static int     wm8904_configure(FAR struct audio_lowerhalf_s *dev,
+                 FAR void *session, FAR const struct audio_caps_s *caps);
+static int     wm8904_start(FAR struct audio_lowerhalf_s *dev,
+                 FAR void *session);
+#ifndef CONFIG_AUDIO_EXCLUDE_STOP
+static int     wm8904_stop(FAR struct audio_lowerhalf_s *dev,
+                 FAR void *session);
+#endif
+#ifndef CONFIG_AUDIO_EXCLUDE_PAUSE_RESUME
+static int     wm8904_pause(FAR struct audio_lowerhalf_s *dev,
+                 FAR void *session);
+static int     wm8904_resume(FAR struct audio_lowerhalf_s *dev,
+                 FAR void *session);
+#endif  /* CONFIG_AUDIO_EXCLUDE_PAUSE_RESUME */
+static int     wm8904_reserve(FAR struct audio_lowerhalf_s *dev,
+                 FAR void** ppContext);
+static int     wm8904_release(FAR struct audio_lowerhalf_s *dev,
+                 FAR void* pContext);
+#else
+static int     wm8904_configure(FAR struct audio_lowerhalf_s *dev,
+                 FAR const struct audio_caps_s *caps);
+static int     wm8904_start(FAR struct audio_lowerhalf_s *dev);
+#ifndef CONFIG_AUDIO_EXCLUDE_STOP
+static int     wm8904_stop(FAR struct audio_lowerhalf_s *dev);
+#endif
+#ifndef CONFIG_AUDIO_EXCLUDE_PAUSE_RESUME
+static int     wm8904_pause(FAR struct audio_lowerhalf_s *dev);
+static int     wm8904_resume(FAR struct audio_lowerhalf_s *dev);
+#endif  /* CONFIG_AUDIO_EXCLUDE_PAUSE_RESUME */
+static int     wm8904_reserve(FAR struct audio_lowerhalf_s *dev);
+static int     wm8904_release(FAR struct audio_lowerhalf_s *dev);
+#endif /* CONFIG_AUDIO_MULTI_SESION */
+static int     wm8904_enqueuebuffer(FAR struct audio_lowerhalf_s *dev,
+                 FAR struct ap_buffer_s *apb);
+static int     wm8904_cancelbuffer(FAR struct audio_lowerhalf_s *dev,
+                 FAR struct ap_buffer_s *apb);
+static int     wm8904_ioctl(FAR struct audio_lowerhalf_s *dev, int cmd,
+                 unsigned long arg);
+
+/****************************************************************************
+ * Private Data
+ ****************************************************************************/
+
+static const struct audio_ops_s g_audioops =
+{
+  wm8904_getcaps,       /* getcaps        */
+  wm8904_configure,     /* configure      */
+  wm8904_shutdown,      /* shutdown       */
+  wm8904_start,         /* start          */
+#ifndef CONFIG_AUDIO_EXCLUDE_STOP
+  wm8904_stop,          /* stop           */
+#endif
+#ifndef CONFIG_AUDIO_EXCLUDE_PAUSE_RESUME
+  wm8904_pause,         /* pause          */
+  wm8904_resume,        /* resume         */
+#endif
+  NULL,                 /* alloc_buffer   */
+  NULL,                 /* free_buffer    */
+  wm8904_enqueuebuffer, /* enqueue_buffer */
+  wm8904_cancelbuffer,  /* cancel_buffer  */
+  wm8904_ioctl,         /* ioctl          */
+  NULL,                 /* read           */
+  NULL,                 /* write          */
+  wm8904_reserve,       /* reserve        */
+  wm8904_release        /* release        */
+};
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: wm8904_readreg
+ *
+ * Description
+ *    Read the specified 16-bit register from the WM8904 device.
+ *
+ ****************************************************************************/
+
+static uint16_t wm8904_readreg(FAR struct wm8904_dev_s *priv, uint8_t regaddr)
+{
+  FAR struct i2c_dev_s *i2c = priv->i2c;
+  uint16_t regval;
+#warning Missing logic
+  audvdbg("Read: %02x -> %04x\n", regaddr, regval);
+  return regval;
+}
+
+/************************************************************************************
+ * Name: wm8904_writereg
+ *
+ * Description:
+ *   Write the specified 16-bit register to the WM8904 device.
+ *
+ ************************************************************************************/
+
+static void wm8904_writereg(FAR struct wm8904_dev_s *priv, uint8_t regaddr, uint16_t regval)
+{
+  FAR struct i2c_dev_s *i2c = priv->i2c;
+
+  /* Select the AUDIO_CTRL device on the I2C bus */
+
+  audvdbg("Write: %02x <- %04x\n", regaddr, regval);
+#warning "Missing logic"
+
+  /* Short delay after a write for WM8904 processing time */
+  /* REVISIT: Necessary for the WM8904? */
+  usleep(10);
+}
+
+/************************************************************************************
+ * Name: wm8904_setvolume
+ *
+ * Description:
+ *   Set the right and left volume values in the WM8904 device based on the current
+ *   volume and balance settings.
+ *
+ ************************************************************************************/
+
+#ifndef CONFIG_AUDIO_EXCLUDE_VOLUME
+static void wm8904_setvolume(FAR struct wm8904_dev_s *priv)
+{
+  FAR struct i2c_dev_s *i2c = priv->i2c;
+  uint32_t              leftlevel;
+  uint32_t              rightlevel;
+
+  /* Constrain balance */
+
+#ifndef CONFIG_AUDIO_EXCLUDE_BALANCE
+  if (priv->balance > 1000)
+    {
+      priv->balance = 1000;
+    }
+
+  /* Calculate the left channel volume level */
+
+  if (priv->balance <= 500)
+    {
+      leftlevel = priv->volume;
+    }
+  else if (priv->balance == 1000)
+    {
+      leftlevel = 0;
+    }
+  else
+    {
+      leftlevel = priv->volume * (1000 - priv->balance) / 500;
+    }
+
+  /* Calculate the right channel volume level */
+
+  if (priv->balance >= 500)
+    {
+      rightlevel = priv->volume;
+    }
+  else if (priv->balance == 0)
+    {
+      rightlevel = 0;
+    }
+  else
+    {
+      rightlevel = priv->volume * priv->balance / 500;
+    }
+#else
+  leftlevel = rightlevel = priv->volume;
+#endif
+
+  /* Set the volume */
+#warning Missing logic
+}
+#endif /* CONFIG_AUDIO_EXCLUDE_VOLUME */
+
+/************************************************************************************
+ * Name: wm8904_setbass
+ *
+ * Description:
+ *   Set the bass and treble level as specified in the context's bass and treble
+ *   variables..
+ *
+ *   The level and range are in whole percentage levels (0-100).
+ *
+ ************************************************************************************/
+
+#ifndef CONFIG_AUDIO_EXCLUDE_TONE
+static void wm8904_setbass(FAR struct wm8904_dev_s *priv)
+{
+  FAR struct i2c_dev_s *i2c = priv->i2c;
+
+#warning Missing logic
+}
+#endif /* CONFIG_AUDIO_EXCLUDE_TONE */
+
+/****************************************************************************
+ * Name: wm8904_getcaps
+ *
+ * Description: Get the audio device capabilities
+ *
+ ****************************************************************************/
+
+static int wm8904_getcaps(FAR struct audio_lowerhalf_s *dev, int type,
+                          FAR struct audio_caps_s *caps)
+{
+  audvdbg("Entry\n");
+
+  /* Validate the structure */
+
+  DEBUGASSERT(caps->ac_len >= sizeof(struct audio_caps_s));
+
+  /* Fill in the caller's structure based on requested info */
+
+  caps->ac_format[0]   = 0;
+  caps->ac_format[1]   = 0;
+  caps->ac_controls[0] = 0;
+  caps->ac_controls[1] = 0;
+  caps->ac_controls[2] = 0;
+  caps->ac_controls[3] = 0;
+
+  switch (caps->ac_type)
+    {
+      /* Caller is querying for the types of units we support */
+
+      case AUDIO_TYPE_QUERY:
+
+        /* Provide our overall capabilities.  The interfacing software
+         * must then call us back for specific info for each capability.
+         */
+
+        caps->ac_channels = 2;       /* Stereo output */
+
+        switch (caps->ac_subtype)
+          {
+            case AUDIO_TYPE_QUERY:
+              /* The input formats we can decode / accept */
+
+              *((uint16_t *) &caps->ac_format[0]) = 0
+#ifdef CONFIG_AUDIO_FORMAT_AC3
+                    | (1 << (AUDIO_FMT_AC3 - 1))
+#endif
+#ifdef CONFIG_AUDIO_FORMAT_MP3
+                    | (1 << (AUDIO_FMT_MP3 - 1))
+#endif
+#ifdef CONFIG_AUDIO_FORMAT_WMA
+                    | (1 << (AUDIO_FMT_WMA - 1))
+#endif
+#ifdef CONFIG_AUDIO_FORMAT_MIDI
+                    | (1 << (AUDIO_FMT_MIDI - 1))
+#endif
+#ifdef CONFIG_AUDIO_FORMAT_PCM
+                    | (1 << (AUDIO_FMT_PCM - 1))
+#endif
+#ifdef CONFIG_AUDIO_FORMAT_OGG_VORBIS
+                    | (1 << (AUDIO_FMT_OGG_VORBIS - 1))
+#endif
+                ;
+
+              /* The types of audio units we implement */
+
+              caps->ac_controls[0] = AUDIO_TYPE_OUTPUT | AUDIO_TYPE_FEATURE |
+                                     AUDIO_TYPE_PROCESSING;
+
+              break;
+
+            /* Report sub-formats for MIDI if requested */
+
+#ifdef CONFIG_AUDIO_FORMAT_MIDI
+            case AUDIO_FMT_MIDI:
+              /* We only support Format 0 */
+
+              caps->ac_controls[0] = AUDIO_SUBFMT_MIDI_0;
+              caps->ac_controls[1] = AUDIO_SUBFMT_END;
+              break;
+#endif
+
+            default:
+              caps->ac_controls[0] = AUDIO_SUBFMT_END;
+              break;
+          }
+
+        break;
+
+      /* Provide capabilities of our OUTPUT unit */
+
+      case AUDIO_TYPE_OUTPUT:
+
+        caps->ac_channels = 2;
+
+        switch (caps->ac_subtype)
+          {
+            case AUDIO_TYPE_QUERY:
+
+              /* Report the Sample rates we support */
+
+              caps->ac_controls[0] = AUDIO_SAMP_RATE_8K | AUDIO_SAMP_RATE_11K |
+                                      AUDIO_SAMP_RATE_16K | AUDIO_SAMP_RATE_22K |
+                                      AUDIO_SAMP_RATE_32K | AUDIO_SAMP_RATE_44K |
+                                      AUDIO_SAMP_RATE_48K;
+              break;
+
+            case AUDIO_FMT_MP3:
+            case AUDIO_FMT_WMA:
+            case AUDIO_FMT_PCM:
+              /* Report the Bit rates we support.  The bit rate support is actually a
+               * complex function of the format and selected sample rate, and the datasheet
+               * has multiple tables to indicate the supported bit rate vs sample rate vs
+               * format.  The selected sample rate should be provided in the ac_format
+               * field of the query, and only a single sample rate should be given.
+               */
+
+              /* TODO:  Create a table or set of tables to report this! */
+
+              break;
+
+            default:
+              break;
+          }
+
+        break;
+
+      /* Provide capabilities of our FEATURE units */
+
+      case AUDIO_TYPE_FEATURE:
+
+        /* If the sub-type is UNDEF, then report the Feature Units we support */
+
+        if (caps->ac_subtype == AUDIO_FU_UNDEF)
+          {
+            /* Fill in the ac_controls section with the Feature Units we have */
+
+            caps->ac_controls[0] = AUDIO_FU_VOLUME | AUDIO_FU_BASS | AUDIO_FU_TREBLE;
+            caps->ac_controls[1] = AUDIO_FU_BALANCE >> 8;
+          }
+        else
+          {
+            /* TODO:  Do we need to provide specific info for the Feature Units,
+             * such as volume setting ranges, etc.?
+             */
+          }
+
+        break;
+
+      /* Provide capabilities of our PROCESSING unit */
+
+      case AUDIO_TYPE_PROCESSING:
+
+        switch (caps->ac_subtype)
+          {
+            case AUDIO_PU_UNDEF:
+
+              /* Provide the type of Processing Units we support */
+
+              caps->ac_controls[0] = AUDIO_PU_STEREO_EXTENDER;
+              break;
+
+            case AUDIO_PU_STEREO_EXTENDER:
+
+              /* Provide capabilities of our Stereo Extender */
+
+              caps->ac_controls[0] = AUDIO_STEXT_ENABLE | AUDIO_STEXT_WIDTH;
+              break;
+
+            default:
+
+              /* Other types of processing uint we don't support */
+
+              break;
+          }
+
+        break;
+
+      /* All others we don't support */
+
+      default:
+
+        /* Zero out the fields to indicate no support */
+
+        caps->ac_subtype = 0;
+        caps->ac_channels = 0;
+
+        break;
+    }
+
+  /* Return the length of the audio_caps_s struct for validation of
+   * proper Audio device type.
+   */
+
+  return caps->ac_len;
+}
+
+/****************************************************************************
+ * Name: wm8904_configure
+ *
+ * Description:
+ *   Configure the audio device for the specified  mode of operation.
+ *
+ ****************************************************************************/
+
+#ifdef CONFIG_AUDIO_MULTI_SESSION
+static int wm8904_configure(FAR struct audio_lowerhalf_s *dev,
+                            FAR void *session,
+                            FAR const struct audio_caps_s *caps)
+#else
+static int wm8904_configure(FAR struct audio_lowerhalf_s *dev,
+                            FAR const struct audio_caps_s *caps)
+#endif
+{
+  int     ret = OK;
+#if !defined(CONFIG_AUDIO_EXCLUDE_VOLUME) || !defined(CONFIG_AUDIO_EXCLUDE_TONE)
+  FAR struct wm8904_dev_s *priv = (FAR struct wm8904_dev_s *)dev;
+#endif
+
+  audvdbg("Entry\n");
+
+  /* Process the configure operation */
+
+  switch (caps->ac_type)
+    {
+      case AUDIO_TYPE_FEATURE:
+
+        /* Process based on Feature Unit */
+
+        switch (*((uint16_t *) caps->ac_format))
+          {
+#ifndef CONFIG_AUDIO_EXCLUDE_VOLUME
+            case AUDIO_FU_VOLUME:
+              /* Set the volume */
+
+              priv->volume = *((uint16_t *) caps->ac_controls);
+              wm8904_setvolume(priv);
+
+              break;
+#endif  /* CONFIG_AUDIO_EXCLUDE_VOLUME */
+
+#if !defined(CONFIG_AUDIO_EXCLUDE_TONE) && !defined(CONFIG_AUDIO_EXCLUDE_VOLUME)
+            case AUDIO_FU_BALANCE:
+              /* Set the volume */
+
+              priv->balance = *((uint16_t *) caps->ac_controls);
+              wm8904_setvolume(priv);
+
+              break;
+#endif
+
+#ifndef CONFIG_AUDIO_EXCLUDE_TONE
+            case AUDIO_FU_BASS:
+              /* Set the bass.  The percentage level (0-100) is in the
+               * ac_controls[0] parameter.
+               */
+
+              priv->bass = caps->ac_controls[0];
+              if (priv->bass > 100)
+                priv->bass = 100;
+              wm8904_setbass(priv);
+
+              break;
+
+            case AUDIO_FU_TREBLE:
+              /* Set the treble.  The percentage level (0-100) is in the
+               * ac_controls[0] parameter.
+               */
+
+              priv->treble = caps->ac_controls[0];
+              if (priv->treble > 100)
+                priv->treble = 100;
+              wm8904_setbass(priv);
+
+              break;
+#endif  /* CONFIG_AUDIO_EXCLUDE_TONE */
+
+            default:
+              /* Others we don't support */
+
+              break;
+          }
+
+        break;
+
+      case AUDIO_TYPE_PROCESSING:
+
+        /* We only support STEREO_EXTENDER */
+
+        if (*((uint16_t *) caps->ac_format) == AUDIO_PU_STEREO_EXTENDER)
+          {
+          }
+
+        break;
+    }
+
+  return ret;
+}
+
+/****************************************************************************
+ * Name: wm8904_softreset
+ *
+ * Description:
+ *   Performs a soft reset on the WM8904 chip by setting the RESET bit of
+ *   the MODE register.
+ *
+ ****************************************************************************/
+
+static int wm8904_softreset(FAR struct wm8904_dev_s *priv)
+{
+  /* First disable interrupts */
+
+  WM8904_DISABLE(priv->lower);
+
+  /* Now issue a reset command */
+#warning Missing logic
+
+  /* Switch to the lowest frequency */
+#warning Missing logic
+  return OK;
+}
+
+/****************************************************************************
+ * Name: wm8904_hardreset
+ *
+ * Description:
+ *   Performs a hardware reset on the WM8904 chip by toggling the RST line,
+ *   disabling interrupts, and setting the default operating frequency.
+ *
+ ****************************************************************************/
+
+static int wm8904_hardreset(FAR struct wm8904_dev_s *priv)
+{
+  WM8904_DISABLE(priv->lower);
+  return OK;
+}
+
+/****************************************************************************
+ * Name: wm8904_shutdown
+ *
+ * Description:
+ *   Shutdown the WM8904 chip and put it in the lowest power state possible.
+ *
+ ****************************************************************************/
+
+static int wm8904_shutdown(FAR struct audio_lowerhalf_s *dev)
+{
+  FAR struct wm8904_dev_s *priv = (FAR struct wm8904_dev_s *)dev;
+  FAR struct i2c_dev_s  *i2c = priv->i2c;
+
+#warning Missing logic
+  return OK;
+}
+
+/****************************************************************************
+ * Name: wm8904_feeddata
+ *
+ * Description:
+ *   Feeds more data to the wm8904 chip from the enqueued buffers.  It will
+ *   continue feeding data until the WM8904 line indicates it can't accept
+ *   any more data.
+ *
+ ****************************************************************************/
+
+static void wm8904_feeddata(FAR struct wm8904_dev_s *priv)
+{
+  FAR struct i2s_dev_s *i2s = priv->i2s;
+  FAR struct ap_buffer_s *apb;
+  FAR uint8_t *samp = NULL;
+  uint16_t regval;
+  int nbytes;
+  int ret;
+
+  /* Local stack copy of our active buffer */
+
+  apb = priv->apb;
+  //auddbg("Entry apb=%p, Bytes left=%d\n", apb, apb->nbytes - apb->curbyte);
+
+  /* Setup pointer to the next sample in the buffer */
+
+  if (apb)
+    {
+      samp = &apb->samp[apb->curbyte];
+    }
+  else if (!priv->endmode)
+    {
+      return;
+    }
+
+  /* Loop until the FIFO is full */
+
+#warning Missing/bogus logic
+  while (false)
+    {
+      /* If endmode, then send fill characters */
+
+      if (priv->endmode)
+        {
+          nbytes = 32;
+          while (nbytes)
+            {
+#warning BOGUS I2S_SEND call
+              I2S_SEND(i2s, NULL, NULL, priv, 0);
+              nbytes--;
+            }
+
+          /* For the WM8904, after the file has been played, we must
+           * send 2052 bytes of endfillchar per the datasheet.
+           */
+
+          priv->endfillbytes += 32;
+
+          /* Process end mode logic.  We send 2080 bytes of endfillchar as
+           * directed by the datasheet, then set SM_CANCEL.  Then we wait
+           * until the chip clears SM_CANCEL while sending endfillchar
+           * 32 bytes at a time.
+           */
+
+          if (priv->endfillbytes == 32*65)
+            {
+              /* After at least 2052 bytes, we send an SM_CANCEL */
+
+              WM8904_DISABLE(priv->lower);
+#warning Missing logic
+              WM8904_ENABLE(priv->lower);
+            }
+          else if (priv->endfillbytes >= 32*130)
+            {
+              /* Do a hard reset and terminate */
+
+              wm8904_hardreset(priv);
+              priv->running = false;
+              priv->endmode = false;
+              break;
+            }
+          else if (priv->endfillbytes > 32*65)
+            {
+              /* After each 32 byte of endfillchar, check the status
+               * register to see if SM_CANCEL has been cleared.  If
+               * it has been cleared, then we're done.
+               */
+#warning Missing logic
+              priv->running = false;
+              priv->endmode = false;
+              break;
+            }
+        }
+      else
+        {
+          /* Send 32 more bytes.  We only send 32 at a time because this is
+           * the meaning of WM8904 active from the chip ... that it can
+           * accept at least 32 more bytes.  After each 32 byte block, we
+           * will recheck the WM8904 line again.
+           */
+
+          nbytes = apb->nbytes - apb->curbyte;
+          if (nbytes > 32)
+            {
+              nbytes = 32;
+            }
+#if 1
+          I2S_SNDBLOCK(priv->i2s, samp, nbytes);
+          samp += nbytes;
+#else
+          nbytes = nbytes;
+          while (nbytes--)
+            {
+              /* Send next byte from the buffer */
+
+#warning BOGUS I2S_SEND call
+              I2S_SEND(i2s, NULL, NULL, priv, 0);
+              samp++;
+            }
+#endif
+          apb->curbyte += nbytes;
+
+          /* Test if we are in cancel mode.  If we are, then we need
+           * to continue sending file data and check for the SM_CANCEL
+           * bit going inactive.
+           */
+
+#ifndef CONFIG_AUDIO_EXCLUDE_STOP
+          if (priv->cancelmode)
+            {
+              /* Check the SM_CANCEL bit */
+#warning Missing logic
+
+              /* Cancel has begun.  Switch to endmode */
+
+              apb->curbyte = apb->nbytes = 0;
+            }
+#endif /* CONFIG_AUDIO_EXCLUDE_STOP */
+
+          /* Test if we are at the end of the buffer */
+
+          if (apb->curbyte >= apb->nbytes)
+            {
+              if (apb->nbytes != apb->nmaxbytes)
+                {
+                  /* Mark the device as endmode */
+
+                  priv->endmode = true;
+#ifndef CONFIG_AUDIO_EXCLUDE_STOP
+                  if (priv->cancelmode)
+                    {
+                      /* If we are in cancel mode, then we don't dequeue the buffer
+                       * or need to send another SM_CANCEL, so jump into the middle
+                       * of the stop sequence.
+                       */
+
+                      priv->endfillbytes = 32*65+1;
+                      continue;
+                    }
+                  else
+#endif  /* CONFIG_AUDIO_EXCLUDE_STOP */
+                    {
+                      priv->endfillbytes = 0;
+                    }
+                }
+
+              /* We referenced the buffer so we must free it */
+
+              apb_free(apb);
+#ifdef CONFIG_AUDIO_MULTI_SESSION
+              priv->dev.upper(priv->dev.priv, AUDIO_CALLBACK_DEQUEUE,
+                              apb, OK, NULL);
+#else
+              priv->dev.upper(priv->dev.priv, AUDIO_CALLBACK_DEQUEUE,
+                              apb, OK);
+#endif
+
+              /* Lock the buffer queue to pop the next buffer */
+
+              if ((ret = sem_wait(&priv->apbq_sem)) != OK)
+                {
+#ifdef CONFIG_AUDIO_MULTI_SESSION
+                  priv->dev.upper(priv->dev.priv,
+                                  AUDIO_CALLBACK_IOERR, NULL, ret, NULL);
+#else
+                  priv->dev.upper(priv->dev.priv,
+                                  AUDIO_CALLBACK_IOERR, NULL, ret);
+#endif
+                  auddbg("I/O error!\n");
+                  break;
+                }
+
+              /* Pop the next entry */
+
+              apb = (struct ap_buffer_s *) dq_remfirst(&priv->apbq);
+              priv->apb = apb;
+
+              //auddbg("Next Buffer = %p, bytes = %d\n", apb, apb ? apb->nbytes : 0);
+              if (apb == NULL)
+                {
+                  sem_post(&priv->apbq_sem);
+                  break;
+                }
+
+              samp = &apb->samp[apb->curbyte];
+              apb_reference(apb);                /* Add our buffer reference */
+              sem_post(&priv->apbq_sem);
+            }
+        }
+    }
+}
+
+/****************************************************************************
+ * Name: wm8904_interrupt
+ *
+ *  This is the ISR that services the WM8904 pin from the WM8904, which
+ *  indicates the chip is ready to receive additional data.  We use it to
+ *  send a message to our worker thread message queue so it knows to wake
+ *  up and send more data.
+ *
+ ****************************************************************************/
+
+static int wm8904_interrupt(FAR const struct wm8904_lower_s *lower,
+                            FAR void *arg)
+{
+  FAR struct wm8904_dev_s *priv = (FAR struct wm8904_dev_s *)arg;
+  struct audio_msg_s msg;
+
+  DEBUGASSERT(lower && priv);
+
+  /* Create a message and send it to the worker thread */
+
+  if (priv->running)
+    {
+      msg.msgId = AUDIO_MSG_DATA_REQUEST;
+      mq_send(priv->mq, &msg, sizeof(msg), CONFIG_WM8904_MSG_PRIO);
+    }
+  else
+    {
+      msg.msgId = AUDIO_MSG_DATA_REQUEST;
+    }
+
+  return 0;
+}
+
+/****************************************************************************
+ * Name: wm8904_workerthread
+ *
+ *  This is the thread that feeds data to the chip and keeps the audio
+ *  stream going.
+ *
+ ****************************************************************************/
+
+static void *wm8904_workerthread(pthread_addr_t pvarg)
+{
+  FAR struct wm8904_dev_s *priv = (struct wm8904_dev_s *) pvarg;
+  struct audio_msg_s      msg;
+  FAR struct ap_buffer_s *apb;
+  int                     size;
+  int                     prio;
+#ifndef CONFIG_AUDIO_EXCLUDE_STOP
+  uint16_t                regval;
+#endif
+
+  auddbg("Entry\n");
+
+#ifndef CONFIG_AUDIO_EXCLUDE_STOP
+  priv->cancelmode = 0;
+#endif
+  priv->endmode = priv->endfillbytes = 0;
+
+  /* Fill the WM8904 FIFO with initial data.  */
+
+  wm8904_feeddata(priv);
+
+  /* Loop as long as we are supposed to be running */
+
+  priv->running = true;
+  WM8904_ENABLE(priv->lower);
+  while (priv->running || priv->endmode)
+    {
+      /* Check if the WM8904 can accept more data */
+#warning Missing logic
+        {
+          wm8904_feeddata(priv);    /* Feed more data to the WM8904 FIFO */
+        }
+
+      /* Wait for messages from our message queue */
+
+      size = mq_receive(priv->mq, &msg, sizeof(msg), &prio);
+
+      /* Handle the case when we return with no message */
+
+      if (size == 0)
+        {
+          /* Should we just stop running? */
+
+          priv->running = false;
+          break;
+        }
+
+      /* Process the message */
+
+      switch (msg.msgId)
+        {
+          /* The ISR has requested more data */
+
+          case AUDIO_MSG_DATA_REQUEST:
+            usleep(500);
+            wm8904_feeddata(priv);   /* Feed more data to the WM8904 FIFO */
+            break;
+
+          /* Stop the playback */
+
+#ifndef CONFIG_AUDIO_EXCLUDE_STOP
+          case AUDIO_MSG_STOP:
+            /* Send CANCEL message to WM8904 */
+
+            WM8904_DISABLE(priv->lower);
+#warning Missing logic
+            WM8904_ENABLE(priv->lower);
+
+            /* Set cancelmode */
+
+            priv->cancelmode = true;
+
+            break;
+#endif
+
+          /* We will wake up when a new buffer enqueued just in case */
+
+          case AUDIO_MSG_ENQUEUE:
+            break;
+
+          default:
+            break;
+        }
+    }
+
+  /* Disable the WM8904 interrupt */
+
+  WM8904_DISABLE(priv->lower);
+
+  /* Cancel any leftover buffer in our queue */
+
+  if (sem_wait(&priv->apbq_sem) == OK)
+    {
+      /* Get the next buffer from the queue */
+
+      while ((apb = (FAR struct ap_buffer_s *) dq_remfirst(&priv->apbq)) != NULL)
+        ;
+    }
+
+  sem_post(&priv->apbq_sem);
+
+  /* Free the active buffer */
+
+  if (priv->apb != NULL)
+    {
+      apb_free(priv->apb);
+      priv->apb = NULL;
+    }
+
+  /* Close the message queue */
+
+  mq_close(priv->mq);
+  mq_unlink(priv->mqname);
+  priv->mq = NULL;
+
+  /* Send an AUDIO_MSG_COMPLETE message to the client */
+
+#ifdef CONFIG_AUDIO_MULTI_SESSION
+  priv->dev.upper(priv->dev.priv, AUDIO_CALLBACK_COMPLETE, NULL, OK, NULL);
+#else
+  priv->dev.upper(priv->dev.priv, AUDIO_CALLBACK_COMPLETE, NULL, OK);
+#endif
+
+  auddbg("Exit\n");
+
+  return NULL;
+}
+
+/****************************************************************************
+ * Name: wm8904_start
+ *
+ * Description: Start the configured operation (audio streaming, volume
+ *              enabled, etc.).
+ *
+ ****************************************************************************/
+
+#ifdef CONFIG_AUDIO_MULTI_SESSION
+static int wm8904_start(FAR struct audio_lowerhalf_s *dev, FAR void *session)
+#else
+static int wm8904_start(FAR struct audio_lowerhalf_s *dev)
+#endif
+{
+  FAR struct wm8904_dev_s *priv = (FAR struct wm8904_dev_s *)dev;
+  struct mq_attr      attr;
+  struct sched_param  sparam;
+  pthread_attr_t      tattr;
+  int                 ret;
+  FAR void           *value;
+
+  auddbg("Entry\n");
+
+  /* Do a soft reset, just in case */
+
+  wm8904_softreset(priv);
+
+  /* Increase the frequency of the part during processing */
+#warning Missing logic
+
+  /* Create a message queue for the worker thread */
+
+  snprintf(priv->mqname, sizeof(priv->mqname), "/tmp/%X", priv);
+
+  attr.mq_maxmsg  = 16;
+  attr.mq_msgsize = sizeof(struct audio_msg_s);
+  attr.mq_curmsgs = 0;
+  attr.mq_flags   = 0;
+
+  priv->mq = mq_open(priv->mqname, O_RDWR | O_CREAT, 0644, &attr);
+  if (priv->mq == NULL)
+    {
+      /* Error creating message queue! */
+
+      auddbg("Couldn't allocate message queue\n");
+      return -ENOMEM;
+    }
+
+  /* Pop the first enqueued buffer */
+
+  if ((ret = sem_wait(&priv->apbq_sem)) == OK)
+    {
+      priv->apb = (FAR struct ap_buffer_s *) dq_remfirst(&priv->apbq);
+      apb_reference(priv->apb);               /* Add our buffer reference */
+      sem_post(&priv->apbq_sem);
+    }
+  else
+    {
+      auddbg("Error getting APB Queue sem\n");
+      return ret;
+    }
+
+  /* Join any old worker thread we had created to prevent a memory leak */
+
+  if (priv->threadid != 0)
+    {
+      auddbg("Joining old thread\n");
+      pthread_join(priv->threadid, &value);
+    }
+
+  /* Start our thread for sending data to the device */
+
+  pthread_attr_init(&tattr);
+  sparam.sched_priority = sched_get_priority_max(SCHED_FIFO) - 3;
+  (void)pthread_attr_setschedparam(&tattr, &sparam);
+  (void)pthread_attr_setstacksize(&tattr, CONFIG_WM8904_WORKER_STACKSIZE);
+
+  auddbg("Starting workerthread\n");
+  ret = pthread_create(&priv->threadid, &tattr, wm8904_workerthread,
+      (pthread_addr_t) priv);
+  if (ret != OK)
+    {
+      auddbg("Can't create worker thread, errno=%d\n", errno);
+    }
+  else
+    {
+      pthread_setname_np(priv->threadid, "wm8904");
+      auddbg("Created worker thread\n");
+    }
+
+  return ret;
+}
+
+/****************************************************************************
+ * Name: wm8904_stop
+ *
+ * Description: Stop the configured operation (audio streaming, volume
+ *              disabled, etc.).
+ *
+ ****************************************************************************/
+
+#ifndef CONFIG_AUDIO_EXCLUDE_STOP
+#ifdef CONFIG_AUDIO_MULTI_SESSION
+static int wm8904_stop(FAR struct audio_lowerhalf_s *dev, FAR void* session)
+#else
+static int wm8904_stop(FAR struct audio_lowerhalf_s *dev)
+#endif
+{
+  FAR struct wm8904_dev_s *priv = (FAR struct wm8904_dev_s *)dev;
+  struct audio_msg_s  term_msg;
+  FAR void*           value;
+
+  /* Send a message to stop all audio streaming */
+
+  term_msg.msgId = AUDIO_MSG_STOP;
+  term_msg.u.data = 0;
+  mq_send(priv->mq, &term_msg, sizeof(term_msg), CONFIG_WM8904_MSG_PRIO);
+
+  /* Join the worker thread */
+
+  pthread_join(priv->threadid, &value);
+  priv->threadid = 0;
+
+  /* Reduce the decoder's operating frequency to save power */
+#warning Missing logic
+
+  /* Wait for a bit */
+
+  up_mdelay(40);
+  return OK;
+}
+#endif
+
+/****************************************************************************
+ * Name: wm8904_pause
+ *
+ * Description: Pauses the playback.
+ *
+ ****************************************************************************/
+
+#ifndef CONFIG_AUDIO_EXCLUDE_PAUSE_RESUME
+#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
+{
+  FAR struct wm8904_dev_s *priv = (FAR struct wm8904_dev_s *)dev;
+
+  if (!priv->running)
+    return OK;
+
+  /* Disable interrupts to prevent us from suppling any more data */
+
+  priv->paused = true;
+  WM8904_DISABLE(priv->lower);
+  return OK;
+}
+#endif /* CONFIG_AUDIO_EXCLUDE_PAUSE_RESUME */
+
+/****************************************************************************
+ * Name: wm8904_resume
+ *
+ * Description: Resuems the playback.
+ *
+ ****************************************************************************/
+
+#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_resume(FAR struct audio_lowerhalf_s *dev)
+#endif
+{
+  FAR struct wm8904_dev_s *priv = (FAR struct wm8904_dev_s *)dev;
+
+  if (!priv->running)
+    return OK;
+
+  /* Enable interrupts to allow suppling data */
+
+  priv->paused = false;
+  wm8904_feeddata(priv);
+  WM8904_ENABLE(priv->lower);
+  return OK;
+}
+#endif /* CONFIG_AUDIO_EXCLUDE_PAUSE_RESUME */
+
+/****************************************************************************
+ * Name: wm8904_enqueuebuffer
+ *
+ * Description: Enqueue an Audio Pipeline Buffer for playback/ processing.
+ *
+ ****************************************************************************/
+
+static int wm8904_enqueuebuffer(FAR struct audio_lowerhalf_s *dev,
+                                FAR struct ap_buffer_s *apb )
+{
+  FAR struct wm8904_dev_s *priv = (FAR struct wm8904_dev_s *)dev;
+  struct audio_msg_s  term_msg;
+  int ret;
+
+  audvdbg("Entry\n");
+
+  /* Lock access to the apbq */
+
+  if ((ret = sem_wait(&priv->apbq_sem)) == OK)
+    {
+      /* We can now safely add the buffer to the queue */
+
+      apb->curbyte = 0;
+      apb->flags = AUDIO_APB_OUTPUT_ENQUEUED;
+      dq_addlast(&apb->dq_entry, &priv->apbq);
+      sem_post(&priv->apbq_sem);
+
+      /* Send a message indicating a new buffer enqueued */
+
+      if (priv->mq != NULL)
+        {
+          term_msg.msgId = AUDIO_MSG_ENQUEUE;
+          term_msg.u.data = 0;
+          mq_send(priv->mq, &term_msg, sizeof(term_msg), CONFIG_WM8904_MSG_PRIO);
+        }
+    }
+
+  return ret;
+}
+
+/****************************************************************************
+ * Name: wm8904_cancelbuffer
+ *
+ * Description: Called when an enqueued buffer is being cancelled.
+ *
+ ****************************************************************************/
+
+static int wm8904_cancelbuffer(FAR struct audio_lowerhalf_s *dev,
+                               FAR struct ap_buffer_s *apb )
+{
+  return OK;
+}
+
+/****************************************************************************
+ * Name: wm8904_ioctl
+ *
+ * Description: Perform a device ioctl
+ *
+ ****************************************************************************/
+
+static int wm8904_ioctl(FAR struct audio_lowerhalf_s *dev, int cmd,
+                        unsigned long arg)
+{
+#ifdef CONFIG_AUDIO_DRIVER_SPECIFIC_BUFFERS
+  FAR struct ap_buffer_info_s *bufinfo;
+#endif
+
+  /* Deal with ioctls passed from the upper-half driver */
+
+  switch (cmd)
+    {
+      /* Check for AUDIOIOC_HWRESET ioctl.  This ioctl is passed straight
+       * through from the upper-half audio driver.
+       */
+
+      case AUDIOIOC_HWRESET:
+        wm8904_hardreset((FAR struct wm8904_dev_s *)dev);
+        break;
+
+       /* Report our preferred buffer size and quantity */
+
+#ifdef CONFIG_AUDIO_DRIVER_SPECIFIC_BUFFERS
+      case AUDIOIOC_GETBUFFERINFO:
+
+        bufinfo = (FAR struct ap_buffer_info_s *) arg;
+        bufinfo->buffer_size = CONFIG_WM8904_BUFFER_SIZE;
+        bufinfo->nbuffers = CONFIG_WM8904_NUM_BUFFERS;
+        break;
+#endif
+
+      default:
+        break;
+    }
+
+  return OK;
+}
+
+/****************************************************************************
+ * Name: wm8904_reserve
+ *
+ * Description: Reserves a session (the only one we have).
+ *
+ ****************************************************************************/
+
+#ifdef CONFIG_AUDIO_MULTI_SESSION
+static int wm8904_reserve(FAR struct audio_lowerhalf_s *dev,
+                          FAR void **session)
+#else
+static int wm8904_reserve(FAR struct audio_lowerhalf_s *dev)
+#endif
+{
+  FAR struct wm8904_dev_s *priv = (FAR struct wm8904_dev_s *) dev;
+  int   ret = OK;
+
+  /* Borrow the APBQ semaphore for thread sync */
+
+  if (sem_wait(&priv->apbq_sem) != OK)
+    {
+      return -EBUSY;
+    }
+
+  if (priv->busy)
+    {
+      ret = -EBUSY;
+    }
+  else
+    {
+      /* Initialize the session context.  We don't really use it. */
+
+#ifdef CONFIG_AUDIO_MULTI_SESSION
+      *session = NULL;
+#endif
+      priv->busy    = true;
+      priv->running = false;
+      priv->paused  = false;
+    }
+
+  sem_post(&priv->apbq_sem);
+
+  return ret;
+}
+
+/****************************************************************************
+ * Name: wm8904_release
+ *
+ * Description: Releases the session (the only one we have).
+ *
+ ****************************************************************************/
+
+#ifdef CONFIG_AUDIO_MULTI_SESSION
+static int wm8904_release(FAR struct audio_lowerhalf_s *dev,
+                          FAR void *session)
+#else
+static int wm8904_release(FAR struct audio_lowerhalf_s *dev)
+#endif
+{
+  FAR struct wm8904_dev_s *priv = (FAR struct wm8904_dev_s *)dev;
+  void  *value;
+
+  /* Join any old worker thread we had created to prevent a memory leak */
+
+  if (priv->threadid != 0)
+    {
+      pthread_join(priv->threadid, &value);
+      priv->threadid = 0;
+    }
+
+  /* Borrow the APBQ semaphore for thread sync */
+
+  if (sem_wait(&priv->apbq_sem) != OK)
+    {
+      return -EBUSY;
+    }
+
+  /* Really we should free any queued buffers here */
+
+  priv->busy = false;
+  sem_post(&priv->apbq_sem);
+
+  return OK;
+}
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: wm8904_initialize
+ *
+ * Description:
+ *   Initialize the WM8904 device.
+ *
+ * Input Parameters:
+ *   i2c     - An I2C driver instance
+ *   i2s     - An I2S driver instance
+ *   lower   - Persistent board configuration data
+ *   minor   - The input device minor number
+ *   session - Returned if multi-sessions are supported
+ *
+ * Returned Value:
+ *   Zero is returned on success.  Otherwise, a negated errno value is
+ *   returned to indicate the nature of the failure.
+ *
+ ****************************************************************************/
+
+FAR struct audio_lowerhalf_s *
+  wm8904_initialize(FAR struct i2c_dev_s *i2c, FAR struct i2s_dev_s *i2s,
+                    FAR const struct wm8904_lower_s *lower, unsigned int devno)
+{
+  FAR struct wm8904_dev_s *priv;
+
+  /* Sanity check */
+
+  DEBUGASSERT(i2c && i2s && lower);
+
+  /* Allocate a WM8904 device structure */
+
+  priv = (FAR struct wm8904_dev_s *)kmalloc(sizeof(struct wm8904_dev_s));
+  if (priv)
+    {
+      /* Initialize the WM8904 device structure */
+
+      priv->dev.ops    = &g_audioops;
+      priv->dev.upper  = NULL;
+      priv->dev.priv   = NULL;
+      priv->lower      = lower;
+      priv->frequency  = CONFIG_WM8904_XTALI / 7;
+      priv->i2c        = i2c;
+      priv->mq         = NULL;
+      priv->busy       = false;
+      priv->threadid   = 0;
+      priv->running    = 0;
+
+#ifndef CONFIG_AUDIO_EXCLUDE_VOLUME
+      priv->volume     = 250;            /* 25% volume as default */
+#ifndef CONFIG_AUDIO_EXCLUDE_BALANCE
+      priv->balance    = 500;            /* Center balance */
+#endif
+#endif
+
+#ifndef CONFIG_AUDIO_EXCLUDE_TONE
+      priv->bass       = 0;
+      priv->treble     = 0;
+#endif
+      sem_init(&priv->apbq_sem, 0, 1);
+      dq_init(&priv->apbq);
+
+      /* Initialize I2C */
+
+      I2C_SETFREQUENCY(i2c, lower->frequency);
+      I2C_SETADDRESS(i2c, lower->address, 7);
+
+      /* Verify the device ID read from the chip */
+#warning Missing logic
+
+      /* Initialize the WM8904 hardware */
+#warning Missing logic
+
+      /* Attach our ISR to this device */
+
+      WM8904_ATTACH(lower, wm8904_interrupt, priv);
+
+      /* Put the drive in the 'shutdown' status */
+
+      wm8904_shutdown(&priv->dev);
+    }
+
+  return &priv->dev;
+}
diff --git a/nuttx/drivers/audio/wm8904.h b/nuttx/drivers/audio/wm8904.h
index b20373b12..44829e7d9 100644
--- a/nuttx/drivers/audio/wm8904.h
+++ b/nuttx/drivers/audio/wm8904.h
@@ -60,8 +60,8 @@
 #define WM8904_SWRST_ID              0x00 /* SW Reset and ID */
 #define WM8904_BIAS_CTRL             0x04 /* Bias Control */
 #define WM8904_VMID_CTRL             0x05 /* VMID Control */
-#define WM8904_MIC_BIAS_CTRL         0x06 /* Mic Bias Control */
-#define WM8904_MIC_BIAS_CTRL         0x07 /* Mic Bias Control */
+#define WM8904_MIC_BIAS_CTRL0        0x06 /* Mic Bias Control 0 */
+#define WM8904_MIC_BIAS_CTRL1        0x07 /* Mic Bias Control 1 */
 #define WM8904_ANALOG_ADC            0x0a /* Analogue ADC */
 #define WM8904_PM0                   0x0c /* Power Management 0 */
 #define WM8904_PM2                   0x0e /* Power Management 2 */
@@ -181,7 +181,7 @@
 #  define WM8904_VMID_RES_FASTSTART  (3 << WM8904_VMID_RES_SHIFT) /* 2 x 5k divider */
 #define WM8904_VMID_ENA              (1 << 0)  /* Bit 0:  VMID buffer enable */
 
-/* 0x06 Mic Bias Control */
+/* 0x06 Mic Bias Control 0 */
 
 #define WM8904_MICDET_THR_SHIFT      (4)       /* Bits 4-6: MICBIAS current detect threshold */
 #define WM8904_MICDET_THR_MASK       (7 << WM8904_MICDET_THR_SHIFT)
@@ -192,7 +192,7 @@
 #define WM8904_MICDET_ENA            (1 << 1)  /* Bit 1:  MICBIAS current/short circuit detect enable */
 #define WM8904_MICBIAS_ENA           (1 << 0)  /* Bit 0:  MICBIAS enable */
 
-/* 0x07 Mic Bias Control */
+/* 0x07 Mic Bias Control 1 */
 
 #define WM8904_MICBIAS_SEL_MASK      (0x0007)  /* Bits 0-2: Selects MICBIAS voltage */
 
@@ -264,7 +264,7 @@
 /* 0x18 Audio Interface 0 */
 
 #define WM8904_DACL_DATINV           (1 << 12) /* Bit 12: Left DAC invert */
-#define WM8904_DACR_DATINV           (1 << 11) /* Bit 11: Right DAC invert* /
+#define WM8904_DACR_DATINV           (1 << 11) /* Bit 11: Right DAC invert */
 #define WM8904_DAC_BOOST_SHIFT       (9)       /* Bits 9-10: DAC digital input volume boost */
 #define WM8904_DAC_BOOST_MASK        (3 << WM8904_DAC_BOOST_SHIFT)
 #  define WM8904_DAC_BOOST_0DB       (0 << WM8904_DAC_BOOST_SHIFT)