fs_fat32util.c

/****************************************************************************
 * fs/fat/fs_fat32util.c
 *
 *   Copyright (C) 2007-2009, 2011 Gregory Nutt. All rights reserved.
 *   Author: Gregory Nutt <gnutt@nuttx.org>
 *
 * References:
 *   Microsoft FAT documentation
 *   Some good ideas were leveraged from the FAT implementation:
 *     'Copyright (C) 2007, ChaN, all right reserved.'
 *     which has an unrestricted license.
 *
 * 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 <stdint.h>
#include <stdbool.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <semaphore.h>
#include <assert.h>
#include <errno.h>
#include <debug.h>

#include <nuttx/kmalloc.h>
#include <nuttx/fs.h>
#include <nuttx/fat.h>

#include "fs_internal.h"
#include "fs_fat32.h"

/****************************************************************************
 * Definitions
 ****************************************************************************/

/****************************************************************************
 * Private Types
 ****************************************************************************/

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

/****************************************************************************
 * Private Variables
 ****************************************************************************/

/****************************************************************************
 * Public Variables
 ****************************************************************************/

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

/****************************************************************************
 * Name: fat_checkfsinfo
 *
 * Desciption: Read the FAT32 FSINFO sector
 *
 ****************************************************************************/

static int fat_checkfsinfo(struct fat_mountpt_s *fs)
{
  /* Make sure that the fsinfo sector is in the cache */

  if (fat_fscacheread(fs, fs->fs_fsinfo) == OK)
    {
      /* Verify that this is, indeed, an FSINFO sector */

      if (FSI_GETLEADSIG(fs->fs_buffer) == 0x41615252  &&
          FSI_GETSTRUCTSIG(fs->fs_buffer) == 0x61417272 &&
          FSI_GETTRAILSIG(fs->fs_buffer) == BOOT_SIGNATURE32)
        {
          fs->fs_fsinextfree  = FSI_GETFREECOUNT(fs->fs_buffer);
          fs->fs_fsifreecount = FSI_GETNXTFREE(fs->fs_buffer);
          return OK;
        }
    }
  return -ENODEV;
}

/****************************************************************************
 * Name: fat_checkbootrecord
 *
 * Desciption: Read a sector and verify that it is a a FAT boot record.
 *
 ****************************************************************************/

static int fat_checkbootrecord(struct fat_mountpt_s *fs)
{
  uint32_t ndatasectors;
  uint32_t ntotalfatsects;
  uint16_t rootdirsectors = 0;
  bool     notfat32 = false;

  /* Verify the MBR signature at offset 510 in the sector (true even
   * if the sector size is greater than 512.  All FAT file systems have
   * this signature. On a FAT32 volume, the RootEntCount , FatSz16, and
   * FatSz32 values should always be zero.  The FAT sector size should
   * match the reported hardware sector size.
   */

  if (MBR_GETSIGNATURE(fs->fs_buffer) != BOOT_SIGNATURE16 ||
      MBR_GETBYTESPERSEC(fs->fs_buffer) != fs->fs_hwsectorsize)
    {
      fdbg("ERROR: Signature: %04x FS sectorsize: %d HW sectorsize: %d\n",
            MBR_GETSIGNATURE(fs->fs_buffer), MBR_GETBYTESPERSEC(fs->fs_buffer),
            fs->fs_hwsectorsize);

      return -ENODEV;
    }

  /* Verify the FAT32 file system type. The determination of the file
   * system type is based on the number of clusters on the volume:  FAT12
   * volume has <= FAT_MAXCLUST12 (4084) clusters, a FAT16 volume has <=
   * FAT_MINCLUST16 (microsfoft says < 65,525) clusters, and any larger
   * is FAT32.
   *
   * Get the number of 32-bit directory entries in root directory (zero
   * for FAT32).
   */

  fs->fs_rootentcnt = MBR_GETROOTENTCNT(fs->fs_buffer);
  if (fs->fs_rootentcnt != 0)
    {
      notfat32       = true; /* Must be zero for FAT32 */
      rootdirsectors = (32 * fs->fs_rootentcnt  + fs->fs_hwsectorsize - 1) / fs->fs_hwsectorsize;
    }

  /* Determine the number of sectors in a FAT. */

  fs->fs_nfatsects = MBR_GETFATSZ16(fs->fs_buffer); /* Should be zero */
  if (fs->fs_nfatsects)
    {
      notfat32 = true; /* Must be zero for FAT32 */
    }
  else
    {
      fs->fs_nfatsects = MBR_GETFATSZ32(fs->fs_buffer);
    }

  if (!fs->fs_nfatsects || fs->fs_nfatsects >= fs->fs_hwnsectors)
    {
      fdbg("ERROR: fs_nfatsects %d fs_hwnsectors: %d\n",
           fs->fs_nfatsects, fs->fs_hwnsectors);

      return -ENODEV;
    }

  /* Get the total number of sectors on the volume. */

  fs->fs_fattotsec = MBR_GETTOTSEC16(fs->fs_buffer); /* Should be zero */
  if (fs->fs_fattotsec)
    {
      notfat32 = true; /* Must be zero for FAT32 */
    }
  else
    {
      fs->fs_fattotsec = MBR_GETTOTSEC32(fs->fs_buffer);
    }

  if (!fs->fs_fattotsec || fs->fs_fattotsec > fs->fs_hwnsectors)
    {
      fdbg("ERROR: fs_fattotsec %d fs_hwnsectors: %d\n",
           fs->fs_fattotsec, fs->fs_hwnsectors);