FAT_CVT_U16
FAT_SUPER->root_max = FAT_DIRENTRY_LENGTH * FAT_CVT_U16(bpb.dir_entries);
if (FAT_CVT_U16(bpb.dir_entries))
if (FAT_CVT_U16(bpb.bytes_per_sect) != (1 << FAT_SUPER->sectsize_bits)
|| FAT_CVT_U16(bpb.bytes_per_sect) != SECTOR_SIZE
FAT_SUPER->sectsize_bits = log2 (FAT_CVT_U16 (bpb.bytes_per_sect));
FAT_SUPER->num_sectors = FAT_CVT_U16 (bpb.short_sectors)
? FAT_CVT_U16 (bpb.short_sectors) : bpb.long_sectors;
FAT_SUPER->fat_offset = FAT_CVT_U16 (bpb.reserved_sects);