include/nuttx/mutex.h: Add inline wrapper functions to more clearly support semaphores when used as mutexs.

include/nuttx/mutex.h

@@ -0,0 +1,228 @@
+/****************************************************************************
+ * include/nuttx/mutex.h
+ *
+ *   Copyright (C) 2017 Pinecone Inc. All rights reserved.
+ *   Author: Qian Wenfa <qianwenfa@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_MUTEX_H
+#define __INCLUDE_NUTTX_MUTEX_H
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <stdbool.h>
+#include <errno.h>
+#include <assert.h>
+#include <nuttx/semaphore.h>
+
+/****************************************************************************
+ * Pre-processor Definitions
+ ****************************************************************************/
+
+#define MUTEX_INITIALIZER    SEM_INITIALIZER(1);
+
+/****************************************************************************
+ * Public Type Definitions
+ ****************************************************************************/
+
+typedef sem_t mutex_t;
+
+/****************************************************************************
+ * Public Function Prototypes
+ ****************************************************************************/
+
+#ifndef __ASSEMBLY__
+
+#ifdef __cplusplus
+#define EXTERN extern "C"
+extern "C"
+{
+#else
+#define EXTERN extern
+#endif
+
+/****************************************************************************
+ * Name: nxmutex_init
+ *
+ * Description:
+ *   This function initializes the UNAMED mutex. Following a
+ *   successful call to nxmutex_init(), the mutex may be used in subsequent
+ *   calls to nxmutex_lock(), nxmutex_unlock(), and nxmutex_trylock().  The mutex
+ *   remains usable until it is destroyed.
+ *
+ * Parameters:
+ *   mutex - Semaphore to be initialized
+ *
+ * Return Value:
+ *   This is an internal OS interface and should not be used by applications.
+ *   It follows the NuttX internal error return policy:  Zero (OK) is
+ *   returned on success.  A negated errno value is returned on failure.
+ *
+ ****************************************************************************/
+
+static inline int nxmutex_init(FAR mutex_t *mutex)
+{
+  return nxsem_init(mutex, 0, 1);
+}
+
+/****************************************************************************
+ * Name: nxmutex_destroy
+ *
+ * Description:
+ *   This function initializes the UNAMED mutex. Following a
+ *   successful call to nxmutex_init(), the mutex may be used in subsequent
+ *   calls to nxmutex_lock(), nxmutex_unlock(), and nxmutex_trylock().  The mutex
+ *   remains usable until it is destroyed.
+ *
+ * Parameters:
+ *   mutex - Semaphore to be destroyed
+ *
+ * Return Value:
+ *   This is an internal OS interface and should not be used by applications.
+ *   It follows the NuttX internal error return policy:  Zero (OK) is
+ *   returned on success.  A negated errno value is returned on failure.
+ *
+ ****************************************************************************/
+
+static inline int nxmutex_destroy(FAR mutex_t *mutex)
+{
+  return nxsem_destroy(mutex);
+}
+
+/****************************************************************************
+ * Name: nxmutex_lock
+ *
+ * Description:
+ *   This function attempts to lock the mutex referenced by 'mutex'.  The mutex
+ *   is implemented with a semaphore, so if the semaphore value is (<=) zero,
+ *   then the calling task will not return until it successfully acquires the lock.
+ *
+ * Parameters:
+ *   mutex - mutex descriptor.
+ *
+ * Return Value:
+ *   This is an internal OS interface and should not be used by applications.
+ *   It follows the NuttX internal error return policy:  Zero (OK) is
+ *   returned on success.  A negated errno value is returned on failure.
+ *   Possible returned errors:
+ *
+ ****************************************************************************/
+
+static inline int nxmutex_lock(FAR mutex_t *mutex)
+{
+  return nxsem_wait_uninterruptible(mutex);
+}
+
+/****************************************************************************
+ * Name: nxmutex_trylock
+ *
+ * Description:
+ *   This function locks the mutex only if the mutex is currently not locked.
+ *   If the mutex has been locked already, the call returns without blocking.
+ *
+ * Parameters:
+ *   mutex - mutex descriptor.
+ *
+ * Return Value:
+ *   This is an internal OS interface and should not be used by applications.
+ *   It follows the NuttX internal error return policy:  Zero (OK) is
+ *   returned on success.  A negated errno value is returned on failure.
+ *   Possible returned errors:
+ *
+ *     -EINVAL - Invalid attempt to lock the mutex
+ *     -EAGAIN - The mutex is not available.
+ *
+ ****************************************************************************/
+
+static inline int nxmutex_trylock(FAR mutex_t *mutex)
+{
+  return nxsem_trywait(mutex);
+}
+
+/****************************************************************************
+ * Name: nxmutex_is_locked
+ *
+ * Description:
+ *   This function get the lock state the mutex referenced by 'mutex'.
+ *
+ * Parameters:
+ *   mutex - mutex descriptor.
+ *
+ * Return Value:
+ *
+ ****************************************************************************/
+
+static inline bool nxmutex_is_locked(FAR mutex_t *mutex)
+{
+  int cnt;
+  int ret;
+
+  ret = nxsem_getvalue(mutex, &cnt);
+
+  DEBUGASSERT(ret == OK);
+
+  return cnt < 1;
+}
+
+/****************************************************************************
+ * Name: nxmutex_unlock
+ *
+ * Description:
+ *   This function attempts to unlock the mutex referenced by 'mutex'.
+ *
+ * Parameters:
+ *   mutex - mutex descriptor.
+ *
+ * Return Value:
+ *   This is an internal OS interface and should not be used by applications.
+ *   It follows the NuttX internal error return policy:  Zero (OK) is
+ *   returned on success.  A negated errno value is returned on failure.
+ *   Possible returned errors:
+ *
+ * Assumptions:
+ *   This function may be called from an interrupt handler.
+ *
+ ****************************************************************************/
+
+static inline int nxmutex_unlock(FAR mutex_t *mutex)
+{
+  return nxsem_post(mutex);
+}
+
+#undef EXTERN
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* __ASSEMBLY__ */
+#endif /* __INCLUDE_NUTTX_MUTEX_H */