text: /****************************************************************************
   *
   * Copyright 2017 Samsung Electronics All Rights Reserved.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   * http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing,
   * software distributed under the License is distributed on an
   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
   * either express or implied. See the License for the specific
   * language governing permissions and limitations under the License.
   *
   ****************************************************************************/
  /****************************************************************************
   * fs/driver/fs_blockproxy.c
   *
   *   Copyright (C) 2015-2016 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 <tinyara/config.h>
  
  #include <sys/types.h>
  #include <sys/stat.h>
  
  #include <stdlib.h>
  #include <unistd.h>
  #include <stdio.h>
  #include <fcntl.h>
  #include <semaphore.h>
  #include <string.h>
  #include <errno.h>
  #include <assert.h>
  #include <debug.h>
  
  #include <tinyara/kmalloc.h>
  #include <tinyara/fs/fs.h>
  
  #if !defined(CONFIG_DISABLE_MOUNTPOINT) && \
  	!defined(CONFIG_DISABLE_PSEUDOFS_OPERATIONS)
  
  /****************************************************************************
   * Private Data
   ****************************************************************************/
  
  static uint32_t g_devno;
  static sem_t g_devno_sem;
  
  /****************************************************************************
   * Private Functions
   ****************************************************************************/
  
  /****************************************************************************
   * Name: unique_chardev
   *
   * Description:
   *   Create a unique temporary device name in the /dev/ directory of the
   *   psuedo-file system.  We cannot use mktemp for this because it will
   *   attempt to open() the file.
   *
   * Input parameters:
   *   None
   *
   * Returned Value:
   *   The allocated path to the device.  This must be released by the caller
   *   to prevent memory links.  NULL will be returned only the case where
   *   we fail to allocate memory.
   *
   ****************************************************************************/
  static FAR char *unique_chardev(void)
  {
  	struct stat statbuf;
  	char devbuf[16];
  	uint32_t devno;
  	int ret;
  
  	/* Loop until we get a unique device name */
  	for (; ; ) {
  		/* Get the semaphore protecting the path number */
  		while (sem_wait(&g_devno_sem) < 0) {
  			DEBUGASSERT(errno == EINTR);
  		}
  
  		/* Get the next device number and release the semaphore */
  		devno = ++g_devno;
  		sem_post(&g_devno_sem);
  
  		/* Construct the full device number */
  		devno &= 0xffffff;
  		snprintf(devbuf, 16, "/dev/tmp%06lx", (unsigned long)devno);
  
  		/* Make sure that file name is not in use */
  		ret = stat(devbuf, &statbuf);
  		if (ret < 0) {
  			DEBUGASSERT(errno == ENOENT);
  			return strdup(devbuf);
  		}
  
  		/* It is in use, try again */
  	}
  }
  
  /****************************************************************************
   * Public Functions
   ****************************************************************************/
  /****************************************************************************
   * Name: block_proxy
   *
   * Description:
   *   Create a temporary char driver using drivers/bch to mediate character
   *   oriented accessed to the block driver.
   *
   * Input parameters:
   *   blkdev - The path to the block driver
   *   oflags - Character driver open flags
   *
   * Returned Value:
   *   If positive, non-zero file descriptor is returned on success.  This
   *   is the file descriptor of the nameless character driver that mediates
   *   accesses to the block driver.
   *
   *   Errors that may be returned:
   *
   *     ENOMEM - Failed to create a temporay path name.
   *
   *   Plus:
   *
   *     - Errors reported from bchdev_register()
   *     - Errors reported from open() or unlink()
   *
   ****************************************************************************/
  int block_proxy(FAR const char *blkdev, int oflags)
  {
  	FAR char *chardev;
  	bool readonly;
  	int ret;
  	int fd;
  
  	DEBUGASSERT(blkdev);
  	DEBUGASSERT((oflags & (O_CREAT | O_EXCL | O_APPEND | O_TRUNC)) == 0);
  
  	/* Create a unique temporary file name for the character device */
  	chardev = unique_chardev();
  	if (chardev == NULL) {
  		fdbg("ERROR: Failed to create temporary device name\n");
  		return -ENOMEM;
  	}
  
  	/* Should this character driver be read-only? */
  	readonly = ((oflags & O_WROK) == 0);
  
  	/* Wrap the block driver with an instance of the BCH driver */
  	ret = bchdev_register(blkdev, chardev, readonly);
  	if (ret < 0) {
  		fdbg("ERROR: bchdev_register(%s, %s) failed: %d\n",
  				blkdev, chardev, ret);
  
  		goto errout_with_chardev;
  	}
  
  	/* Open the newly created character driver */
  	oflags &= ~(O_CREAT | O_EXCL | O_APPEND | O_TRUNC);
  	fd = open(chardev, oflags);
  	if (fd < 0) {
  		ret = -errno;
  		fdbg("ERROR: Failed to open %s: %d\n", chardev, ret);
  		goto errout_with_bchdev;
  	}
  
  	/*
  	 * Unlink the character device name.  The driver instance will persist,
  	 * provided that CONFIG_DISABLE_PSEUDOFS_OPERATIONS=y (otherwise, we have
  	 * a problem here!)
  	 */
  	ret = unlink(chardev);
  	if (ret < 0) {
  		ret = -errno;
  		fdbg("ERROR: Failed to unlink %s: %d\n", chardev, ret);
  	}
  
  	/*
  	 * Free the allocate character driver name and return the open file
  	 * descriptor.
  	 */
  	kmm_free(chardev);
  	return fd;
  
  errout_with_bchdev:
  	(void)unlink(chardev);
  
  errout_with_chardev:
  	kmm_free(chardev);
  	return ret;
  }
  
  /****************************************************************************
   * Name: unique_chardev_initialize
   *
   * Description:
   *   Initialize a semphore for unique character device
   *
   * Input parameters:
   *   None
   *
   * Returned Value:
   *   None
   *
   ****************************************************************************/
  void unique_chardev_initialize(void)
  {
  	/* Initialize a semphore for unique chardev */
  
  	sem_init(&g_devno_sem, 0, 1);
  }
  #endif /* !CONFIG_DISABLE_MOUNTPOINT && !CONFIG_DISABLE_PSEUDOFS_OPERATIONS */
  