incubator-nuttx/drivers/loop/loop.c

/****************************************************************************
 * drivers/loop/loop.c
 *
 *   Copyright (C) 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 <stdbool.h>
#include <string.h>
#include <errno.h>

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

#ifdef CONFIG_DEV_LOOP

/****************************************************************************
 * Private Function Prototypes
 ****************************************************************************/

static ssize_t loop_read(FAR struct file *filep, FAR char *buffer,
                 size_t buflen);
static ssize_t loop_write(FAR struct file *filep, FAR const char *buffer,
                 size_t buflen);
static int     loop_ioctl(FAR struct file *filep, int cmd,
                 unsigned long arg);

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

static const struct file_operations g_loop_fops =
{
  NULL,          /* open */
  NULL,          /* close */
  loop_read,     /* read */
  loop_write,    /* write */
  NULL,          /* seek */
  loop_ioctl,    /* ioctl */
  NULL           /* poll */
};

/****************************************************************************
 * Private Functions
 ****************************************************************************/

/****************************************************************************
 * Name: loop_read
 ****************************************************************************/

static ssize_t loop_read(FAR struct file *filep, FAR char *buffer,
                         size_t len)
{
  return 0; /* Return EOF */
}

/****************************************************************************
 * Name: loop_write
 ****************************************************************************/

static ssize_t loop_write(FAR struct file *filep, FAR const char *buffer,
                          size_t len)
{
  return len; /* Say that everything was written */
}

/****************************************************************************
 * Name: loop_ioctl
 ****************************************************************************/

static int loop_ioctl(FAR struct file *filep, int cmd, unsigned long arg)
{
  int ret;

  switch (cmd)
    {
    /* Command:      LOOPIOC_SETUP
     * Description:  Setup the loop device
     * Argument:     A pointer to a read-only instance of struct losetup_s.
     * Dependencies: The loop device must be enabled (CONFIG_DEV_LOOP=y)
     */

    case LOOPIOC_SETUP:
      {
         FAR struct losetup_s *setup =
           (FAR struct losetup_s *)((uintptr_t)arg);

        if (setup == NULL)
          {
            ret = -EINVAL;
          }
        else
          {
            ret = losetup(setup->devname, setup->filename, setup->sectsize,
                          setup->offset, setup->readonly);
          }
      }
      break;

    /* Command:      LOOPIOC_TEARDOWN
     * Description:  Teardown a loop device previously setup via
                     LOOPIOC_SETUP
     * Argument:     A read-able pointer to the path of the device to be
     *               torn down
     * Dependencies: The loop device must be enabled (CONFIG_DEV_LOOP=y)
     */

    case LOOPIOC_TEARDOWN:
      {
        FAR const char *devname = (FAR const char *)((uintptr_t)arg);

        if (devname == NULL)
          {
            ret = -EINVAL;
          }
        else
          {
            ret = loteardown(devname);
          }
       }
       break;

     default:
       ret = -ENOTTY;
       break;
    }

  return ret;
}

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

/****************************************************************************
 * Name: loop_register
 *
 * Description:
 *   Register /dev/null
 *
 ****************************************************************************/

void loop_register(void)
{
  register_driver("/dev/loop", &g_loop_fops, 0666, NULL);
}

#endif /* CONFIG_DEV_LOOP */