The Design and Implementation of the FreeBSD Operating System, Second Edition
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FreeBSD/Linux Kernel Cross Reference
sys/msdosfs/bpb.h

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    1 /* $FreeBSD: src/sys/msdosfs/bpb.h,v 1.3.4.2 1999/09/05 08:17:15 peter Exp $ */
    2 /*      $NetBSD: bpb.h,v 1.7 1997/11/17 15:36:24 ws Exp $       */
    3 
    4 /*
    5  * Written by Paul Popelka (paulp@uts.amdahl.com)
    6  *
    7  * You can do anything you want with this software, just don't say you wrote
    8  * it, and don't remove this notice.
    9  *
   10  * This software is provided "as is".
   11  *
   12  * The author supplies this software to be publicly redistributed on the
   13  * understanding that the author is not responsible for the correct
   14  * functioning of this software in any circumstances and is not liable for
   15  * any damages caused by this software.
   16  *
   17  * October 1992
   18  */
   19 
   20 /*
   21  * BIOS Parameter Block (BPB) for DOS 3.3
   22  */
   23 struct bpb33 {
   24         u_int16_t       bpbBytesPerSec; /* bytes per sector */
   25         u_int8_t        bpbSecPerClust; /* sectors per cluster */
   26         u_int16_t       bpbResSectors;  /* number of reserved sectors */
   27         u_int8_t        bpbFATs;        /* number of FATs */
   28         u_int16_t       bpbRootDirEnts; /* number of root directory entries */
   29         u_int16_t       bpbSectors;     /* total number of sectors */
   30         u_int8_t        bpbMedia;       /* media descriptor */
   31         u_int16_t       bpbFATsecs;     /* number of sectors per FAT */
   32         u_int16_t       bpbSecPerTrack; /* sectors per track */
   33         u_int16_t       bpbHeads;       /* number of heads */
   34         u_int16_t       bpbHiddenSecs;  /* number of hidden sectors */
   35 };
   36 
   37 /*
   38  * BPB for DOS 5.0 The difference is bpbHiddenSecs is a short for DOS 3.3,
   39  * and bpbHugeSectors is not in the 3.3 bpb.
   40  */
   41 struct bpb50 {
   42         u_int16_t       bpbBytesPerSec; /* bytes per sector */
   43         u_int8_t        bpbSecPerClust; /* sectors per cluster */
   44         u_int16_t       bpbResSectors;  /* number of reserved sectors */
   45         u_int8_t        bpbFATs;        /* number of FATs */
   46         u_int16_t       bpbRootDirEnts; /* number of root directory entries */
   47         u_int16_t       bpbSectors;     /* total number of sectors */
   48         u_int8_t        bpbMedia;       /* media descriptor */
   49         u_int16_t       bpbFATsecs;     /* number of sectors per FAT */
   50         u_int16_t       bpbSecPerTrack; /* sectors per track */
   51         u_int16_t       bpbHeads;       /* number of heads */
   52         u_int32_t       bpbHiddenSecs;  /* # of hidden sectors */
   53         u_int32_t       bpbHugeSectors; /* # of sectors if bpbSectors == 0 */
   54 };
   55 
   56 /*
   57  * BPB for DOS 7.10 (FAT32).  This one has a few extensions to bpb50.
   58  */
   59 struct bpb710 {
   60         u_int16_t       bpbBytesPerSec; /* bytes per sector */
   61         u_int8_t        bpbSecPerClust; /* sectors per cluster */
   62         u_int16_t       bpbResSectors;  /* number of reserved sectors */
   63         u_int8_t        bpbFATs;        /* number of FATs */
   64         u_int16_t       bpbRootDirEnts; /* number of root directory entries */
   65         u_int16_t       bpbSectors;     /* total number of sectors */
   66         u_int8_t        bpbMedia;       /* media descriptor */
   67         u_int16_t       bpbFATsecs;     /* number of sectors per FAT */
   68         u_int16_t       bpbSecPerTrack; /* sectors per track */
   69         u_int16_t       bpbHeads;       /* number of heads */
   70         u_int32_t       bpbHiddenSecs;  /* # of hidden sectors */
   71         u_int32_t       bpbHugeSectors; /* # of sectors if bpbSectors == 0 */
   72         u_int32_t       bpbBigFATsecs;  /* like bpbFATsecs for FAT32 */
   73         u_int16_t       bpbExtFlags;    /* extended flags: */
   74 #define FATNUM          0xf             /* mask for numbering active FAT */
   75 #define FATMIRROR       0x80            /* FAT is mirrored (like it always was) */
   76         u_int16_t       bpbFSVers;      /* filesystem version */
   77 #define FSVERS          0               /* currently only 0 is understood */
   78         u_int32_t       bpbRootClust;   /* start cluster for root directory */
   79         u_int16_t       bpbFSInfo;      /* filesystem info structure sector */
   80         u_int16_t       bpbBackup;      /* backup boot sector */
   81         /* There is a 12 byte filler here, but we ignore it */
   82 };
   83 
   84 #ifdef  atari
   85 /*
   86  * BPB for gemdos filesystems. Atari leaves the obsolete stuff undefined.
   87  * Currently there is no need for a separate BPB structure.
   88  */
   89 #if 0
   90 struct bpb_a {
   91         u_int16_t       bpbBytesPerSec; /* bytes per sector             */
   92         u_int8_t        bpbSecPerClust; /* sectors per cluster          */
   93         u_int16_t       bpbResSectors;  /* number of reserved sectors   */
   94         u_int8_t        bpbFATs;        /* number of FATs               */
   95         u_int16_t       bpbRootDirEnts; /* number of root directory entries */
   96         u_int16_t       bpbSectors;     /* total number of sectors      */
   97         u_int8_t        bpbUseless1;    /* meaningless on gemdos fs     */
   98         u_int16_t       bpbFATsecs;     /* number of sectors per FAT    */
   99         u_int16_t       bpbUseless2;    /* meaningless for harddisk fs  */
  100         u_int16_t       bpbUseless3;    /* meaningless for harddisk fs  */
  101         u_int16_t       bpbHiddenSecs;  /* the TOS-BIOS ignores this    */
  102 };
  103 #endif
  104 #endif  /* atari */
  105 
  106 /*
  107  * The following structures represent how the bpb's look on disk.  shorts
  108  * and longs are just character arrays of the appropriate length.  This is
  109  * because the compiler forces shorts and longs to align on word or
  110  * halfword boundaries.
  111  *
  112  * XXX The little-endian code here assumes that the processor can access
  113  * 16-bit and 32-bit quantities on byte boundaries.  If this is not true,
  114  * use the macros for the big-endian case.
  115  */
  116 #include <machine/endian.h>
  117 #if (BYTE_ORDER == LITTLE_ENDIAN)                       /* && defined(UNALIGNED_ACCESS) */
  118 #define getushort(x)    *((u_int16_t *)(x))
  119 #define getulong(x)     *((u_int32_t *)(x))
  120 #define putushort(p, v) (*((u_int16_t *)(p)) = (v))
  121 #define putulong(p, v)  (*((u_int32_t *)(p)) = (v))
  122 #else
  123 #define getushort(x)    (((u_int8_t *)(x))[0] + (((u_int8_t *)(x))[1] << 8))
  124 #define getulong(x)     (((u_int8_t *)(x))[0] + (((u_int8_t *)(x))[1] << 8) \
  125                          + (((u_int8_t *)(x))[2] << 16) \
  126                          + (((u_int8_t *)(x))[3] << 24))
  127 #define putushort(p, v) (((u_int8_t *)(p))[0] = (v),    \
  128                          ((u_int8_t *)(p))[1] = (v) >> 8)
  129 #define putulong(p, v)  (((u_int8_t *)(p))[0] = (v),    \
  130                          ((u_int8_t *)(p))[1] = (v) >> 8, \
  131                          ((u_int8_t *)(p))[2] = (v) >> 16,\
  132                          ((u_int8_t *)(p))[3] = (v) >> 24)
  133 #endif
  134 
  135 /*
  136  * BIOS Parameter Block (BPB) for DOS 3.3
  137  */
  138 struct byte_bpb33 {
  139         int8_t bpbBytesPerSec[2];       /* bytes per sector */
  140         int8_t bpbSecPerClust;          /* sectors per cluster */
  141         int8_t bpbResSectors[2];        /* number of reserved sectors */
  142         int8_t bpbFATs;                 /* number of FATs */
  143         int8_t bpbRootDirEnts[2];       /* number of root directory entries */
  144         int8_t bpbSectors[2];           /* total number of sectors */
  145         int8_t bpbMedia;                /* media descriptor */
  146         int8_t bpbFATsecs[2];           /* number of sectors per FAT */
  147         int8_t bpbSecPerTrack[2];       /* sectors per track */
  148         int8_t bpbHeads[2];             /* number of heads */
  149         int8_t bpbHiddenSecs[2];        /* number of hidden sectors */
  150 };
  151 
  152 /*
  153  * BPB for DOS 5.0 The difference is bpbHiddenSecs is a short for DOS 3.3,
  154  * and bpbHugeSectors is not in the 3.3 bpb.
  155  */
  156 struct byte_bpb50 {
  157         int8_t bpbBytesPerSec[2];       /* bytes per sector */
  158         int8_t bpbSecPerClust;          /* sectors per cluster */
  159         int8_t bpbResSectors[2];        /* number of reserved sectors */
  160         int8_t bpbFATs;                 /* number of FATs */
  161         int8_t bpbRootDirEnts[2];       /* number of root directory entries */
  162         int8_t bpbSectors[2];           /* total number of sectors */
  163         int8_t bpbMedia;                /* media descriptor */
  164         int8_t bpbFATsecs[2];           /* number of sectors per FAT */
  165         int8_t bpbSecPerTrack[2];       /* sectors per track */
  166         int8_t bpbHeads[2];             /* number of heads */
  167         int8_t bpbHiddenSecs[4];        /* number of hidden sectors */
  168         int8_t bpbHugeSectors[4];       /* # of sectors if bpbSectors == 0 */
  169 };
  170 
  171 /*
  172  * BPB for DOS 7.10 (FAT32).  This one has a few extensions to bpb50.
  173  */
  174 struct byte_bpb710 {
  175         u_int8_t bpbBytesPerSec[2];     /* bytes per sector */
  176         u_int8_t bpbSecPerClust;        /* sectors per cluster */
  177         u_int8_t bpbResSectors[2];      /* number of reserved sectors */
  178         u_int8_t bpbFATs;               /* number of FATs */
  179         u_int8_t bpbRootDirEnts[2];     /* number of root directory entries */
  180         u_int8_t bpbSectors[2];         /* total number of sectors */
  181         u_int8_t bpbMedia;              /* media descriptor */
  182         u_int8_t bpbFATsecs[2];         /* number of sectors per FAT */
  183         u_int8_t bpbSecPerTrack[2];     /* sectors per track */
  184         u_int8_t bpbHeads[2];           /* number of heads */
  185         u_int8_t bpbHiddenSecs[4];      /* # of hidden sectors */
  186         u_int8_t bpbHugeSectors[4];     /* # of sectors if bpbSectors == 0 */
  187         u_int8_t bpbBigFATsecs[4];      /* like bpbFATsecs for FAT32 */
  188         u_int8_t bpbExtFlags[2];        /* extended flags: */
  189         u_int8_t bpbFSVers[2];          /* filesystem version */
  190         u_int8_t bpbRootClust[4];       /* start cluster for root directory */
  191         u_int8_t bpbFSInfo[2];          /* filesystem info structure sector */
  192         u_int8_t bpbBackup[2];          /* backup boot sector */
  193         /* There is a 12 byte filler here, but we ignore it */
  194 };
  195 
  196 /*
  197  * FAT32 FSInfo block.
  198  */
  199 struct fsinfo {
  200         u_int8_t fsisig1[4];
  201         u_int8_t fsifill1[480];
  202         u_int8_t fsisig2[4];
  203         u_int8_t fsinfree[4];
  204         u_int8_t fsinxtfree[4];
  205         u_int8_t fsifill2[12];
  206         u_int8_t fsisig3[4];
  207         u_int8_t fsifill3[508];
  208         u_int8_t fsisig4[4];
  209 };

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