nuttx/drivers/pipes/fifo.c

/****************************************************************************
 * drivers/pipes/fifo.c
 *
 *   Copyright (C) 2008-2009, 2014-2015 Gregory Nutt. All rights reserved.
 *   Author: Gregory Nutt <gnutt@nuttx.org>
 *
 * 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/stat.h>
#include <stdint.h>
#include <errno.h>

#include <nuttx/fs/fs.h>
#include <nuttx/drivers/drivers.h>

#include "pipe_common.h"

#if CONFIG_DEV_FIFO_SIZE > 0

/****************************************************************************
 * Private Data
 ****************************************************************************/

static const struct file_operations fifo_fops =
{
  pipecommon_open,  /* open */
  pipecommon_close, /* close */
  pipecommon_read,  /* read */
  pipecommon_write, /* write */
  0,                /* seek */
  pipecommon_ioctl, /* ioctl */
  pipecommon_poll,  /* poll */
#ifndef CONFIG_DISABLE_PSEUDOFS_OPERATIONS
  pipecommon_unlink /* unlink */
#endif
};

/****************************************************************************
 * Public Functions
 ****************************************************************************/

/****************************************************************************
 * Name: mkfifo2
 *
 * Description:
 *   mkfifo() makes a FIFO device driver file with name 'pathname.'  Unlike
 *   Linux, a NuttX FIFO is not a special file type but simply a device
 *   driver instance.  'mode' specifies the FIFO's permissions.
 *
 *   Once the FIFO has been created by mkfifo(), any thread can open it for
 *   reading or writing, in the same way as an ordinary file. However, it
 *   must have been opened from both reading and writing before input or
 *   output can be performed.  This FIFO implementation will block all
 *   attempts to open a FIFO read-only until at least one thread has opened
 *   the FIFO for  writing.
 *
 *   If all threads that write to the FIFO have closed, subsequent calls to
 *   read() on the FIFO will return 0 (end-of-file).
 *
 *   NOTE: mkfifo2 is a special, non-standard, NuttX-only interface.  Since
 *   the NuttX FIFOs are based in in-memory, circular buffers, the ability
 *   to control the size of those buffers is critical for system tuning.
 *
 * Input Parameters:
 *   pathname - The full path to the FIFO instance to attach to or to create
 *     (if not already created).
 *   mode - Ignored for now
 *   bufsize - The size of the in-memory, circular buffer in bytes.
 *
 * Returned Value:
 *   0 is returned on success; otherwise, -1 is returned with errno set
 *   appropriately.
 *
 ****************************************************************************/

int mkfifo2(FAR const char *pathname, mode_t mode, size_t bufsize)
{
  FAR struct pipe_dev_s *dev;
  int errcode;
  int ret;

  /* Allocate and initialize a new device structure instance */

  dev = pipecommon_allocdev(bufsize);
  if (!dev)
    {
      errcode = ENOMEM;
      goto errout;
    }

  ret = register_driver(pathname, &fifo_fops, mode, (FAR void *)dev);
  if (ret != 0)
    {
      pipecommon_freedev(dev);
      errcode = -ret;
      goto errout;
    }

  return OK;

errout:
  set_errno(errcode);
  return ERROR;
}

#endif /* CONFIG_DEV_FIFO_SIZE > 0 */