text: #ifndef _LINUX_MSDOS_FS_H
  #define _LINUX_MSDOS_FS_H
  
  #include <linux/magic.h>
  
  /*
   * The MS-DOS filesystem constants/structures
   */
  #include <asm/byteorder.h>
  
  #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 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	/* == MINIX_ROOT_INO */
  #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)
  
  /* valid file mode bits */
  #define MSDOS_VALID_MODE (S_IFREG | S_IFDIR | S_IRWXU | S_IRWXG | S_IRWXO)
  /* Convert attribute bits and a mask to the UNIX mode. */
  #define MSDOS_MKMODE(a, m) (m & (a & ATTR_RO ? S_IRUGO|S_IXUGO : S_IRWXUGO))
  
  #define MSDOS_NAME	11	/* maximum name length */
  #define MSDOS_LONGNAME	256	/* 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 */
  
  /* media of boot sector */
  #define FAT_VALID_MEDIA(x)	((0xF8 <= (x) && (x) <= 0xFF) || (x) == 0xF0)
  #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)
  
  /*
   * ioctl commands
   */
  #define VFAT_IOCTL_READDIR_BOTH		_IOR('r', 1, struct dirent [2])
  #define VFAT_IOCTL_READDIR_SHORT	_IOR('r', 2, struct 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)
  
  /*
   * vfat shortname flags
   */
  #define VFAT_SFN_DISPLAY_LOWER	0x0001 /* convert to lowercase for display */
  #define VFAT_SFN_DISPLAY_WIN95	0x0002 /* emulate win95 rule for display */
  #define VFAT_SFN_DISPLAY_WINNT	0x0004 /* emulate winnt rule for display */
  #define VFAT_SFN_CREATE_WIN95	0x0100 /* emulate win95 rule for create */
  #define VFAT_SFN_CREATE_WINNT	0x0200 /* emulate winnt rule for create */
  
  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 */
  };
  
  struct fat_slot_info {
  	loff_t i_pos;		/* on-disk position of directory entry */
  	loff_t slot_off;	/* offset for slot or de start */
  	int nr_slots;		/* number of slots + 1(de) in filename */
  	struct msdos_dir_entry *de;
  	struct buffer_head *bh;
  };
  
  
  #endif
  