## FATFS

The `FATFS` structure holds dynamic work area of individual logical drives. It is given by application program and registerd/unregisterd to the FatFs module with f_mount function. Following members are in standard configuration. There is no member that can be changed from the application program.

    typedef struct _FATFS {
        BYTE    fs_type;      /* FAT sub type */
        BYTE    drive;        /* Physical drive number */
        BYTE    csize;        /* Number of sectors per cluster */
        BYTE    n_fats;       /* Number of FAT copies */
        BYTE    wflag;        /* win[] dirty flag (1:must be written back) */
        BYTE    pad1;
        WORD    id;           /* File system mount ID */
        WORD    n_rootdir;    /* Number of root directory entries (0 on FAT32) */
    #if _FS_REENTRANT
        HANDLE  h_mutex;      /* Handle to the mutex (Platform dependent) */
    #endif
    #if _MAX_SS != 512
        WORD    s_size;       /* Sector size */
    #endif
    #if !_FS_READONLY
        BYTE    fsi_flag;     /* fsinfo dirty flag (1:must be written back) */
        BYTE    pad2;
        DWORD   last_clust;   /* Last allocated cluster */
        DWORD   free_clust;   /* Number of free clusters */
        DWORD   fsi_sector;   /* fsinfo sector */
    #endif
        DWORD   sects_fat;    /* Sectors per fat */
        DWORD   max_clust;    /* Maximum cluster# + 1. Number of clusters is max_clust - 2 */
        DWORD   fatbase;      /* FAT start sector */
        DWORD   dirbase;      /* Root directory start sector (Cluster# on FAT32) */
        DWORD   database;     /* Data start sector */
        DWORD   winsect;      /* Current sector appearing in the win[] */
        BYTE    win[MAX_SS];  /* Disk access window for Directory/FAT */
    } FATFS;

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