msdos_fs.h

Go to the documentation of this file.

#ifndef _UAPI_LINUX_MSDOS_FS_H
#define _UAPI_LINUX_MSDOS_FS_H

#include <linux/types.h>
#include <linux/magic.h>
#include <asm/byteorder.h>

/*
 * The MS-DOS filesystem constants/structures
 */

#define SECTOR_SIZE 512     /* sector size (bytes) */
#define SECTOR_BITS 9       /* log2(SECTOR_SIZE) */
#define MSDOS_DPB   (MSDOS_DPS) /* dir entries per block */
#define MSDOS_DPB_BITS  4       /* log2(MSDOS_DPB) */
#define MSDOS_DPS   (SECTOR_SIZE / sizeof(struct msdos_dir_entry))
#define MSDOS_DPS_BITS  4       /* log2(MSDOS_DPS) */
#define MSDOS_LONGNAME  256     /* maximum name length */
#define CF_LE_W(v)  le16_to_cpu(v)
#define CF_LE_L(v)  le32_to_cpu(v)
#define CT_LE_W(v)  cpu_to_le16(v)
#define CT_LE_L(v)  cpu_to_le32(v)

#define MSDOS_ROOT_INO   1  /* The root inode number */
#define MSDOS_FSINFO_INO 2  /* Used for managing the FSINFO block */

#define MSDOS_DIR_BITS  5   /* log2(sizeof(struct msdos_dir_entry)) */

/* directory limit */
#define FAT_MAX_DIR_ENTRIES (65536)
#define FAT_MAX_DIR_SIZE    (FAT_MAX_DIR_ENTRIES << MSDOS_DIR_BITS)

#define ATTR_NONE   0   /* no attribute bits */
#define ATTR_RO     1   /* read-only */
#define ATTR_HIDDEN 2   /* hidden */
#define ATTR_SYS    4   /* system */
#define ATTR_VOLUME 8   /* volume label */
#define ATTR_DIR    16  /* directory */
#define ATTR_ARCH   32  /* archived */

/* attribute bits that are copied "as is" */
#define ATTR_UNUSED (ATTR_VOLUME | ATTR_ARCH | ATTR_SYS | ATTR_HIDDEN)
/* bits that are used by the Windows 95/Windows NT extended FAT */
#define ATTR_EXT    (ATTR_RO | ATTR_HIDDEN | ATTR_SYS | ATTR_VOLUME)

#define CASE_LOWER_BASE 8   /* base is lower case */
#define CASE_LOWER_EXT  16  /* extension is lower case */

#define DELETED_FLAG    0xe5    /* marks file as deleted when in name[0] */
#define IS_FREE(n)  (!*(n) || *(n) == DELETED_FLAG)

#define FAT_LFN_LEN 255 /* maximum long name length */
#define MSDOS_NAME  11  /* maximum name length */
#define MSDOS_SLOTS 21  /* max # of slots for short and long names */
#define MSDOS_DOT   ".          "   /* ".", padded to MSDOS_NAME chars */
#define MSDOS_DOTDOT    "..         "   /* "..", padded to MSDOS_NAME chars */

#define FAT_FIRST_ENT(s, x) ((MSDOS_SB(s)->fat_bits == 32 ? 0x0FFFFF00 : \
    MSDOS_SB(s)->fat_bits == 16 ? 0xFF00 : 0xF00) | (x))

/* start of data cluster's entry (number of reserved clusters) */
#define FAT_START_ENT   2

/* maximum number of clusters */
#define MAX_FAT12   0xFF4
#define MAX_FAT16   0xFFF4
#define MAX_FAT32   0x0FFFFFF6
#define MAX_FAT(s)  (MSDOS_SB(s)->fat_bits == 32 ? MAX_FAT32 : \
    MSDOS_SB(s)->fat_bits == 16 ? MAX_FAT16 : MAX_FAT12)

/* bad cluster mark */
#define BAD_FAT12   0xFF7
#define BAD_FAT16   0xFFF7
#define BAD_FAT32   0x0FFFFFF7

/* standard EOF */
#define EOF_FAT12   0xFFF
#define EOF_FAT16   0xFFFF
#define EOF_FAT32   0x0FFFFFFF

#define FAT_ENT_FREE    (0)
#define FAT_ENT_BAD (BAD_FAT32)
#define FAT_ENT_EOF (EOF_FAT32)

#define FAT_FSINFO_SIG1 0x41615252
#define FAT_FSINFO_SIG2 0x61417272
#define IS_FSINFO(x)    (le32_to_cpu((x)->signature1) == FAT_FSINFO_SIG1 \
             && le32_to_cpu((x)->signature2) == FAT_FSINFO_SIG2)

struct __fat_dirent {
    long        d_ino;
    __kernel_off_t  d_off;
    unsigned short  d_reclen;
    char        d_name[256]; /* We must not include limits.h! */
};

/*
 * ioctl commands
 */
#define VFAT_IOCTL_READDIR_BOTH     _IOR('r', 1, struct __fat_dirent[2])
#define VFAT_IOCTL_READDIR_SHORT    _IOR('r', 2, struct __fat_dirent[2])
/* <linux/videotext.h> has used 0x72 ('r') in collision, so skip a few */
#define FAT_IOCTL_GET_ATTRIBUTES    _IOR('r', 0x10, __u32)
#define FAT_IOCTL_SET_ATTRIBUTES    _IOW('r', 0x11, __u32)

struct fat_boot_sector {
    __u8    ignored[3]; /* Boot strap short or near jump */
    __u8    system_id[8];   /* Name - can be used to special case
                   partition manager volumes */
    __u8    sector_size[2]; /* bytes per logical sector */
    __u8    sec_per_clus;   /* sectors/cluster */
    __le16  reserved;   /* reserved sectors */
    __u8    fats;       /* number of FATs */
    __u8    dir_entries[2]; /* root directory entries */
    __u8    sectors[2]; /* number of sectors */
    __u8    media;      /* media code */
    __le16  fat_length; /* sectors/FAT */
    __le16  secs_track; /* sectors per track */
    __le16  heads;      /* number of heads */
    __le32  hidden;     /* hidden sectors (unused) */
    __le32  total_sect; /* number of sectors (if sectors == 0) */

    /* The following fields are only used by FAT32 */
    __le32  fat32_length;   /* sectors/FAT */
    __le16  flags;      /* bit 8: fat mirroring, low 4: active fat */
    __u8    version[2]; /* major, minor filesystem version */
    __le32  root_cluster;   /* first cluster in root directory */
    __le16  info_sector;    /* filesystem info sector */
    __le16  backup_boot;    /* backup boot sector */
    __le16  reserved2[6];   /* Unused */
};

struct fat_boot_fsinfo {
    __le32   signature1;    /* 0x41615252L */
    __le32   reserved1[120];    /* Nothing as far as I can tell */
    __le32   signature2;    /* 0x61417272L */
    __le32   free_clusters; /* Free cluster count.  -1 if unknown */
    __le32   next_cluster;  /* Most recently allocated cluster */
    __le32   reserved2[4];
};

struct msdos_dir_entry {
    __u8    name[MSDOS_NAME];/* name and extension */
    __u8    attr;       /* attribute bits */
    __u8    lcase;      /* Case for base and extension */
    __u8    ctime_cs;   /* Creation time, centiseconds (0-199) */
    __le16  ctime;      /* Creation time */
    __le16  cdate;      /* Creation date */
    __le16  adate;      /* Last access date */
    __le16  starthi;    /* High 16 bits of cluster in FAT32 */
    __le16  time,date,start;/* time, date and first cluster */
    __le32  size;       /* file size (in bytes) */
};

/* Up to 13 characters of the name */
struct msdos_dir_slot {
    __u8    id;     /* sequence number for slot */
    __u8    name0_4[10];    /* first 5 characters in name */
    __u8    attr;       /* attribute byte */
    __u8    reserved;   /* always 0 */
    __u8    alias_checksum; /* checksum for 8.3 alias */
    __u8    name5_10[12];   /* 6 more characters in name */
    __le16   start;     /* starting cluster number, 0 in long slots */
    __u8    name11_12[4];   /* last 2 characters in name */
};

#endif /* _UAPI_LINUX_MSDOS_FS_H */