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incubator-nuttx/drivers/loop.c

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/****************************************************************************
* drivers/loop.c
*
* Copyright (C) 2008-2009, 2011, 2014 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 <sys/types.h>
#include <sys/ioctl.h>
#include <sys/mount.h>
#include <stdint.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <fcntl.h>
#include <semaphore.h>
#include <debug.h>
#include <errno.h>
#include <nuttx/kmalloc.h>
#include <nuttx/fs/fs.h>
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
#define loop_semgive(d) sem_post(&(d)->sem) /* To match loop_semtake */
#define MAX_OPENCNT (255) /* Limit of uint8_t */
/****************************************************************************
* Private Types
****************************************************************************/
struct loop_struct_s
{
sem_t sem; /* For safe read-modify-write operations */
uint32_t nsectors; /* Number of sectors on device */
off_t offset; /* Offset (in bytes) to the first sector */
uint16_t sectsize; /* The size of one sector */
uint8_t opencnt; /* Count of open references to the loop device */
#ifdef CONFIG_FS_WRITABLE
bool writeenabled; /* true: can write to device */
#endif
int fd; /* Descriptor of char device/file */
};
/****************************************************************************
* Private Function Prototypes
****************************************************************************/
static int loop_semtake(FAR struct loop_struct_s *dev);
static int loop_open(FAR struct inode *inode);
static int loop_close(FAR struct inode *inode);
static ssize_t loop_read(FAR struct inode *inode, FAR unsigned char *buffer,
size_t start_sector, unsigned int nsectors);
#ifdef CONFIG_FS_WRITABLE
static ssize_t loop_write(FAR struct inode *inode,
FAR const unsigned char *buffer,
size_t start_sector, unsigned int nsectors);
#endif
static int loop_geometry(FAR struct inode *inode,
FAR struct geometry *geometry);
/****************************************************************************
* Private Data
****************************************************************************/
static const struct block_operations g_bops =
{
loop_open, /* open */
loop_close, /* close */
loop_read, /* read */
#ifdef CONFIG_FS_WRITABLE
loop_write, /* write */
#else
NULL, /* write */
#endif
loop_geometry, /* geometry */
NULL /* ioctl */
};
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Name: loop_semtake
****************************************************************************/
static int loop_semtake(FAR struct loop_struct_s *dev)
{
int ret;
/* Take the semaphore (perhaps waiting) */
ret = sem_wait(&dev->sem);
if (ret < 0)
{
int errcode = get_errno();
/* The only case that an error should occur here is if
* the wait was awakened by a signal.
*/
ASSERT(errcode == EINTR);
return -ret;
}
return OK;
}
/****************************************************************************
* Name: loop_open
*
* Description: Open the block device
*
****************************************************************************/
static int loop_open(FAR struct inode *inode)
{
FAR struct loop_struct_s *dev;
int ret;
DEBUGASSERT(inode && inode->i_private);
dev = (FAR struct loop_struct_s *)inode->i_private;
/* Make sure we have exclusive access to the state structure */
ret = loop_semtake(dev);
if (ret == OK)
{
if (dev->opencnt == MAX_OPENCNT)
{
ret = -EMFILE;
}
else
{
/* Increment the open count */
dev->opencnt++;
}
loop_semgive(dev);
}
return ret;
}
/****************************************************************************
* Name: loop_close
*
* Description: close the block device
*
****************************************************************************/
static int loop_close(FAR struct inode *inode)
{
FAR struct loop_struct_s *dev;
int ret;
DEBUGASSERT(inode && inode->i_private);
dev = (FAR struct loop_struct_s *)inode->i_private;
/* Make sure we have exclusive access to the state structure */
ret = loop_semtake(dev);
if (ret == OK)
{
if (dev->opencnt == 0)
{
ret = -EIO;
}
else
{
/* Decrement the open count */
dev->opencnt--;
}
loop_semgive(dev);
}
return ret;
}
/****************************************************************************
* Name: loop_read
*
* Description: Read the specified number of sectors
*
****************************************************************************/
static ssize_t loop_read(FAR struct inode *inode, FAR unsigned char *buffer,
size_t start_sector, unsigned int nsectors)
{
FAR struct loop_struct_s *dev;
ssize_t nbytesread;
off_t offset;
int ret;
DEBUGASSERT(inode && inode->i_private);
dev = (FAR struct loop_struct_s *)inode->i_private;
if (start_sector + nsectors > dev->nsectors)
{
dbg("Read past end of file\n");
return -EIO;
}
/* Calculate the offset to read the sectors and seek to the position */
offset = start_sector * dev->sectsize + dev->offset;
ret = lseek(dev->fd, offset, SEEK_SET);
if (ret == (off_t)-1)
{
dbg("Seek failed for offset=%d: %d\n", (int)offset, get_errno());
return -EIO;
}
/* Then read the requested number of sectors from that position */
do
{
nbytesread = read(dev->fd, buffer, nsectors * dev->sectsize);
if (nbytesread < 0 && get_errno() != EINTR)
{
dbg("Read failed: %d\n", get_errno());
return -get_errno();
}
}
while (nbytesread < 0);
/* Return the number of sectors read */
return nbytesread / dev->sectsize;
}
/****************************************************************************
* Name: loop_write
*
* Description: Write the specified number of sectors
*
****************************************************************************/
#ifdef CONFIG_FS_WRITABLE
static ssize_t loop_write(FAR struct inode *inode,
FAR const unsigned char *buffer,
size_t start_sector, unsigned int nsectors)
{
FAR struct loop_struct_s *dev;
ssize_t nbyteswritten;
off_t offset;
int ret;
DEBUGASSERT(inode && inode->i_private);
dev = (FAR struct loop_struct_s *)inode->i_private;
/* Calculate the offset to write the sectors and seek to the position */
offset = start_sector * dev->sectsize + dev->offset;
ret = lseek(dev->fd, offset, SEEK_SET);
if (ret == (off_t)-1)
{
dbg("Seek failed for offset=%d: %d\n", (int)offset, get_errno());
}
/* Then write the requested number of sectors to that position */
do
{
nbyteswritten = write(dev->fd, buffer, nsectors * dev->sectsize);
if (nbyteswritten < 0 && get_errno() != EINTR)
{
dbg("Write failed: %d\n", get_errno());
return -get_errno();
}
}
while (nbyteswritten < 0);
/* Return the number of sectors written */
return nbyteswritten / dev->sectsize;
}
#endif
/****************************************************************************
* Name: loop_geometry
*
* Description: Return device geometry
*
****************************************************************************/
static int loop_geometry(FAR struct inode *inode,
FAR struct geometry *geometry)
{
FAR struct loop_struct_s *dev;
DEBUGASSERT(inode);
if (geometry)
{
dev = (FAR struct loop_struct_s *)inode->i_private;
geometry->geo_available = true;
geometry->geo_mediachanged = false;
#ifdef CONFIG_FS_WRITABLE
geometry->geo_writeenabled = dev->writeenabled;
#else
geometry->geo_writeenabled = false;
#endif
geometry->geo_nsectors = dev->nsectors;
geometry->geo_sectorsize = dev->sectsize;
return OK;
}
return -EINVAL;
}
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: losetup
*
* Description:
* Setup the loop device so that it exports the file referenced by 'filename'
* as a block device.
*
****************************************************************************/
int losetup(FAR const char *devname, FAR const char *filename,
uint16_t sectsize, off_t offset, bool readonly)
{
FAR struct loop_struct_s *dev;
struct stat sb;
int ret;
/* Sanity check */
#ifdef CONFIG_DEBUG
if (!devname || !filename || !sectsize)
{
return -EINVAL;
}
#endif
/* Get the size of the file */
ret = stat(filename, &sb);
if (ret < 0)
{
dbg("Failed to stat %s: %d\n", filename, get_errno());
return -get_errno();
}
/* Check if the file system is big enough for one block */
if (sb.st_size - offset < sectsize)
{
dbg("File is too small for blocksize\n");
return -ERANGE;
}
/* Allocate a loop device structure */
dev = (FAR struct loop_struct_s *)kmm_zalloc(sizeof(struct loop_struct_s));
if (!dev)
{
return -ENOMEM;
}
/* Initialize the loop device structure. */
sem_init(&dev->sem, 0, 1);
dev->nsectors = (sb.st_size - offset) / sectsize;
dev->sectsize = sectsize;
dev->offset = offset;
/* Open the file. */
#ifdef CONFIG_FS_WRITABLE
dev->writeenabled = false; /* Assume failure */
dev->fd = -1;
/* First try to open the device R/W access (unless we are asked
* to open it readonly).
*/
if (!readonly)
{
dev->fd = open(filename, O_RDWR);
}
if (dev->fd >= 0)
{
dev->writeenabled = true; /* Success */
}
else
#endif
{
/* If that fails, then try to open the device read-only */
dev->fd = open(filename, O_RDWR);
if (dev->fd < 0)
{
dbg("Failed to open %s: %d\n", filename, get_errno());
ret = -get_errno();
goto errout_with_dev;
}
}
/* Inode private data will be reference to the loop device structure */
ret = register_blockdriver(devname, &g_bops, 0, dev);
if (ret < 0)
{
fdbg("register_blockdriver failed: %d\n", -ret);
goto errout_with_fd;
}
return OK;
errout_with_fd:
close(dev->fd);
errout_with_dev:
kmm_free(dev);
return ret;
}
/****************************************************************************
* Name: loteardown
*
* Description:
* Undo the setup performed by losetup
*
****************************************************************************/
int loteardown(FAR const char *devname)
{
FAR struct loop_struct_s *dev;
FAR struct inode *inode;
int ret;
/* Sanity check */
#ifdef CONFIG_DEBUG
if (!devname)
{
return -EINVAL;
}
#endif
/* Open the block driver associated with devname so that we can get the inode
* reference.
*/
ret = open_blockdriver(devname, MS_RDONLY, &inode);
if (ret < 0)
{
dbg("Failed to open %s: %d\n", devname, -ret);
return ret;
}
/* Inode private data is a reference to the loop device structure */
dev = (FAR struct loop_struct_s *)inode->i_private;
close_blockdriver(inode);
DEBUGASSERT(dev);
/* Are there still open references to the device */
if (dev->opencnt > 0)
{
return -EBUSY;
}
/* Otherwise, unregister the block device */
ret = unregister_blockdriver(devname);
/* Release the device structure */
if (dev->fd >= 0)
{
(void)close(dev->fd);
}
kmm_free(dev);
return ret;
}
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