2fe4ad52f8
git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@4499 42af7a65-404d-4744-a932-0658087f49c3
507 lines
14 KiB
C
507 lines
14 KiB
C
/****************************************************************************
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* drivers/loop.c
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*
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* Copyright (C) 2008-2009, 2011 Gregory Nutt. All rights reserved.
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* Author: Gregory Nutt <spudmonkey@racsa.co.cr>
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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* 3. Neither the name NuttX nor the names of its contributors may be
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* used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*
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****************************************************************************/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <nuttx/config.h>
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <sys/types.h>
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#include <sys/ioctl.h>
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#include <sys/mount.h>
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#include <stdint.h>
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#include <stdbool.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <string.h>
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#include <fcntl.h>
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#include <semaphore.h>
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#include <debug.h>
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#include <errno.h>
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#include <nuttx/kmalloc.h>
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#include <nuttx/fs/fs.h>
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/****************************************************************************
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* Pre-processor Definitions
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****************************************************************************/
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#define loop_semgive(d) sem_post(&(d)->sem) /* To match loop_semtake */
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#define MAX_OPENCNT (255) /* Limit of uint8_t */
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/****************************************************************************
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* Private Types
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****************************************************************************/
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struct loop_struct_s
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{
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sem_t sem; /* For safe read-modify-write operations */
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uint32_t nsectors; /* Number of sectors on device */
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off_t offset; /* Offset (in bytes) to the first sector */
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uint16_t sectsize; /* The size of one sector */
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uint8_t opencnt; /* Count of open references to the loop device */
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#ifdef CONFIG_FS_WRITABLE
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bool writeenabled; /* true: can write to device */
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#endif
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int fd; /* Descriptor of char device/file */
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};
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/****************************************************************************
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* Private Function Prototypes
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****************************************************************************/
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static void loop_semtake(FAR struct loop_struct_s *dev);
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static int loop_open(FAR struct inode *inode);
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static int loop_close(FAR struct inode *inode);
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static ssize_t loop_read(FAR struct inode *inode, unsigned char *buffer,
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size_t start_sector, unsigned int nsectors);
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#ifdef CONFIG_FS_WRITABLE
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static ssize_t loop_write(FAR struct inode *inode, const unsigned char *buffer,
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size_t start_sector, unsigned int nsectors);
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#endif
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static int loop_geometry(FAR struct inode *inode, struct geometry *geometry);
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/****************************************************************************
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* Private Data
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****************************************************************************/
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static const struct block_operations g_bops =
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{
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loop_open, /* open */
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loop_close, /* close */
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loop_read, /* read */
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#ifdef CONFIG_FS_WRITABLE
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loop_write, /* write */
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#else
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NULL, /* write */
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#endif
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loop_geometry, /* geometry */
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NULL /* ioctl */
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};
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/****************************************************************************
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* Private Functions
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****************************************************************************/
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/****************************************************************************
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* Name: loop_semtake
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****************************************************************************/
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static void loop_semtake(FAR struct loop_struct_s *dev)
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{
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/* Take the semaphore (perhaps waiting) */
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while (sem_wait(&dev->sem) != 0)
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{
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/* The only case that an error should occur here is if
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* the wait was awakened by a signal.
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*/
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ASSERT(errno == EINTR);
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}
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}
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/****************************************************************************
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* Name: loop_open
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*
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* Description: Open the block device
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*
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****************************************************************************/
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static int loop_open(FAR struct inode *inode)
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{
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FAR struct loop_struct_s *dev;
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int ret = OK;
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DEBUGASSERT(inode && inode->i_private);
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dev = (FAR struct loop_struct_s *)inode->i_private;
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/* Make sure we have exclusive access to the state structure */
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loop_semtake(dev);
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if (dev->opencnt == MAX_OPENCNT)
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{
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return -EMFILE;
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}
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else
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{
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/* Increment the open count */
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dev->opencnt++;
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}
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loop_semgive(dev);
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return ret;
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}
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/****************************************************************************
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* Name: loop_close
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*
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* Description: close the block device
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*
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****************************************************************************/
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static int loop_close(FAR struct inode *inode)
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{
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FAR struct loop_struct_s *dev;
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int ret = OK;
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DEBUGASSERT(inode && inode->i_private);
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dev = (FAR struct loop_struct_s *)inode->i_private;
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/* Make sure we have exclusive access to the state structure */
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loop_semtake(dev);
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if (dev->opencnt == 0)
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{
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return -EIO;
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}
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else
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{
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/* Decrement the open count */
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dev->opencnt--;
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}
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loop_semgive(dev);
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return ret;
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}
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/****************************************************************************
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* Name: loop_read
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*
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* Description: Read the specified numer of sectors
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*
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****************************************************************************/
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static ssize_t loop_read(FAR struct inode *inode, unsigned char *buffer,
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size_t start_sector, unsigned int nsectors)
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{
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FAR struct loop_struct_s *dev;
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size_t nbytesread;
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off_t offset;
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int ret;
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DEBUGASSERT(inode && inode->i_private);
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dev = (FAR struct loop_struct_s *)inode->i_private;
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if (start_sector + nsectors > dev->nsectors)
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{
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dbg("Read past end of file\n");
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return -EIO;
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}
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/* Calculate the offset to read the sectors and seek to the position */
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offset = start_sector * dev->sectsize + dev->offset;
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ret = lseek(dev->fd, offset, SEEK_SET);
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if (ret == (off_t)-1)
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{
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dbg("Seek failed for offset=%d: %d\n", (int)offset, errno);
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return -EIO;
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}
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/* Then read the requested number of sectors from that position */
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do
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{
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nbytesread = read(dev->fd, buffer, nsectors * dev->sectsize);
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if (nbytesread < 0 && errno != EINTR)
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{
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dbg("Read failed: %d\n", errno);
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return -errno;
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}
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}
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while (nbytesread < 0);
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/* Return the number of sectors read */
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return nbytesread / dev->sectsize;
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}
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/****************************************************************************
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* Name: loop_write
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*
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* Description: Write the specified number of sectors
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*
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****************************************************************************/
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#ifdef CONFIG_FS_WRITABLE
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static ssize_t loop_write(FAR struct inode *inode, const unsigned char *buffer,
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size_t start_sector, unsigned int nsectors)
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{
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FAR struct loop_struct_s *dev;
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size_t nbyteswritten;
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off_t offset;
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int ret;
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DEBUGASSERT(inode && inode->i_private);
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dev = (FAR struct loop_struct_s *)inode->i_private;
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/* Calculate the offset to write the sectors and seek to the position */
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offset = start_sector * dev->sectsize + dev->offset;
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ret = lseek(dev->fd, offset, SEEK_SET);
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if (ret == (off_t)-1)
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{
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dbg("Seek failed for offset=%d: %d\n", (int)offset, errno);
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}
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/* Then write the requested number of sectors to that position */
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do
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{
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nbyteswritten = write(dev->fd, buffer, nsectors * dev->sectsize);
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if (nbyteswritten < 0 && errno != EINTR)
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{
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dbg("Write failed: %d\n", errno);
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return -errno;
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}
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}
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while (nbyteswritten < 0);
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/* Return the number of sectors written */
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return nbyteswritten / dev->sectsize;
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}
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#endif
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/****************************************************************************
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* Name: loop_geometry
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*
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* Description: Return device geometry
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*
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****************************************************************************/
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static int loop_geometry(FAR struct inode *inode, struct geometry *geometry)
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{
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FAR struct loop_struct_s *dev;
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DEBUGASSERT(inode);
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if (geometry)
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{
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dev = (FAR struct loop_struct_s *)inode->i_private;
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geometry->geo_available = true;
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geometry->geo_mediachanged = false;
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#ifdef CONFIG_FS_WRITABLE
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geometry->geo_writeenabled = dev->writeenabled;
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#else
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geometry->geo_writeenabled = false;
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#endif
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geometry->geo_nsectors = dev->nsectors;
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geometry->geo_sectorsize = dev->sectsize;
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return OK;
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}
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return -EINVAL;
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}
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: losetup
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*
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* Description:
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* Setup the loop device so that it exports the file referenced by 'filename'
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* as a block device.
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*
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****************************************************************************/
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int losetup(const char *devname, const char *filename, uint16_t sectsize,
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off_t offset, bool readonly)
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{
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FAR struct loop_struct_s *dev;
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struct stat sb;
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int ret;
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/* Sanity check */
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#ifdef CONFIG_DEBUG
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if (!devname || !filename || !sectsize)
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{
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return -EINVAL;
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}
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#endif
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/* Get the size of the file */
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ret = stat(filename, &sb);
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if (ret < 0)
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{
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dbg("Failed to stat %s: %d\n", filename, errno);
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return -errno;
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}
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/* Check if the file system is big enough for one block */
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if (sb.st_size - offset < sectsize)
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{
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dbg("File is too small for blocksize\n");
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return -ERANGE;
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}
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/* Allocate a loop device structure */
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dev = (FAR struct loop_struct_s *)kzalloc(sizeof(struct loop_struct_s));
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if (!dev)
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{
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return -ENOMEM;
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}
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/* Initialize the loop device structure. */
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sem_init(&dev->sem, 0, 1);
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dev->nsectors = (sb.st_size - offset) / sectsize;
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dev->sectsize = sectsize;
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dev->offset = offset;
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/* Open the file. */
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#ifdef CONFIG_FS_WRITABLE
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dev->writeenabled = false; /* Assume failure */
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dev->fd = -1;
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/* First try to open the device R/W access (unless we are asked
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* to open it readonly).
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*/
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if (!readonly)
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{
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dev->fd = open(filename, O_RDWR);
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}
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if (dev->fd >= 0)
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{
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dev->writeenabled = true; /* Success */
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}
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else
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#endif
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{
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/* If that fails, then try to open the device read-only */
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dev->fd = open(filename, O_RDWR);
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if (dev->fd < 0)
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{
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dbg("Failed to open %s: %d\n", filename, errno);
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ret = -errno;
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goto errout_with_dev;
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}
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}
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/* Inode private data will be reference to the loop device structure */
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ret = register_blockdriver(devname, &g_bops, 0, dev);
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if (ret < 0)
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{
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fdbg("register_blockdriver failed: %d\n", -ret);
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goto errout_with_fd;
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}
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return OK;
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errout_with_fd:
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close(dev->fd);
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errout_with_dev:
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kfree(dev);
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return ret;
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}
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/****************************************************************************
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* Name: loteardown
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*
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* Description:
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* Undo the setup performed by losetup
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*
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****************************************************************************/
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int loteardown(const char *devname)
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{
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FAR struct loop_struct_s *dev;
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FAR struct inode *inode;
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int ret;
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/* Sanity check */
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#ifdef CONFIG_DEBUG
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if (!devname)
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{
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return -EINVAL;
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}
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#endif
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/* Open the block driver associated with devname so that we can get the inode
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* reference.
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*/
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ret = open_blockdriver(devname, MS_RDONLY, &inode);
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if (ret < 0)
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{
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dbg("Failed to open %s: %d\n", devname, -ret);
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return ret;
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}
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/* Inode private data is a reference to the loop device stgructure */
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dev = (FAR struct loop_struct_s *)inode->i_private;
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close_blockdriver(inode);
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DEBUGASSERT(dev);
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/* Are there still open references to the device */
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if (dev->opencnt > 0)
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{
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return -EBUSY;
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}
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/* Otherwise, unregister the block device */
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ret = unregister_blockdriver(devname);
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/* Release the device structure */
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if (dev->fd >= 0)
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{
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(void)close(dev->fd);
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}
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kfree(dev);
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return ret;
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}
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