audio/audio_comp.c: Add the composite audio driver

audio/Kconfig

@@ -11,6 +11,12 @@ config AUDIO
 
 if AUDIO
 
+config AUDIO_COMP
+	bool "Support audio composition"
+	default n
+	---help---
+		Composite several lower level audio devices into big one.
+
 config AUDIO_MULTI_SESSION
 	bool "Support multiple sessions"
 	default n

audio/Makefile

@@ -45,6 +45,10 @@ ASRCS =
 CSRCS = audio.c
 VPATH = .
 
+ifeq ($(CONFIG_AUDIO_COMP),y)
+  CSRCS += audio_comp.c
+endif
+
 # Include support for various drivers.  Each Make.defs file will add its
 # files to the source file list, add its DEPPATH info, and will add
 # the appropriate paths to the VPATH variable

include/nuttx/audio/audio_comp.h

@@ -0,0 +1,99 @@
+/****************************************************************************
+ * include/nuttx/audio/audio_comp.h
+ * A general audio driver to composite other lower level audio driver.
+ *
+ *   Copyright (C) 2018 Pinecone Inc. All rights reserved.
+ *   Author:  Xiang Xiao <xiaoxiang@pinecone.net>
+ *
+ * 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.
+ *
+ ****************************************************************************/
+
+#ifndef __INCLUDE_NUTTX_AUDIO_AUDIO_COMP_H
+#define __INCLUDE_NUTTX_AUDIO_AUDIO_COMP_H
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#ifdef CONFIG_AUDIO_COMP
+#include <nuttx/audio/audio.h>
+
+/****************************************************************************
+ * Pre-processor Definitions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Public Types
+ ****************************************************************************/
+
+/****************************************************************************
+ * Public Data
+ ****************************************************************************/
+
+#ifdef __cplusplus
+#define EXTERN extern "C"
+extern "C"
+{
+#else
+#define EXTERN extern
+#endif
+
+/****************************************************************************
+ * Public Function Prototypes
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: audio_comp_initialize
+ *
+ * Description:
+ *   Initialize the composite audio device.
+ *
+ * Input Parameters:
+ *   name - The name of the audio device.
+ *   ...  - The list of the lower half audio driver.
+ *
+ * Returned Value:
+ *   Zero on success; a negated errno value on failure.
+ *
+ * Note
+ *   The variable argument list must be NULL terminated.
+ *
+ ****************************************************************************/
+
+int audio_comp_initialize(FAR const char *name, ...);
+
+#undef EXTERN
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* CONFIG_AUDIO_COMP */
+#endif /* __INCLUDE_NUTTX_AUDIO_AUDIO_COMP_H */