in fs/fatfs/src/ff.c [2941:3152]
FRESULT find_volume ( /* FR_OK(0): successful, !=0: any error occurred */
const TCHAR** path, /* Pointer to pointer to the path name (drive number) */
FATFS** rfs, /* Pointer to pointer to the found file system object */
BYTE mode /* !=0: Check write protection for write access */
)
{
BYTE fmt, *pt;
int vol;
DSTATUS stat;
DWORD bsect, fasize, tsect, sysect, nclst, szbfat, br[4];
WORD nrsv;
FATFS *fs;
UINT i;
/* Get logical drive number */
*rfs = 0;
vol = get_ldnumber(path);
if (vol < 0) return FR_INVALID_DRIVE;
/* Check if the file system object is valid or not */
fs = FatFs[vol]; /* Get pointer to the file system object */
if (!fs) return FR_NOT_ENABLED; /* Is the file system object available? */
ENTER_FF(fs); /* Lock the volume */
*rfs = fs; /* Return pointer to the file system object */
mode &= (BYTE)~FA_READ; /* Desired access mode, write access or not */
if (fs->fs_type) { /* If the volume has been mounted */
stat = disk_status(fs->drv);
if (!(stat & STA_NOINIT)) { /* and the physical drive is kept initialized */
if (!_FS_READONLY && mode && (stat & STA_PROTECT)) { /* Check write protection if needed */
return FR_WRITE_PROTECTED;
}
return FR_OK; /* The file system object is valid */
}
}
/* The file system object is not valid. */
/* Following code attempts to mount the volume. (analyze BPB and initialize the fs object) */
fs->fs_type = 0; /* Clear the file system object */
fs->drv = LD2PD(vol); /* Bind the logical drive and a physical drive */
stat = disk_initialize(fs->drv); /* Initialize the physical drive */
if (stat & STA_NOINIT) { /* Check if the initialization succeeded */
return FR_NOT_READY; /* Failed to initialize due to no medium or hard error */
}
if (!_FS_READONLY && mode && (stat & STA_PROTECT)) { /* Check disk write protection if needed */
return FR_WRITE_PROTECTED;
}
#if _MAX_SS != _MIN_SS /* Get sector size (multiple sector size cfg only) */
if (disk_ioctl(fs->drv, GET_SECTOR_SIZE, &SS(fs)) != RES_OK) return FR_DISK_ERR;
if (SS(fs) > _MAX_SS || SS(fs) < _MIN_SS || (SS(fs) & (SS(fs) - 1))) return FR_DISK_ERR;
#endif
/* Find an FAT partition on the drive. Supports only generic partitioning, FDISK and SFD. */
bsect = 0;
fmt = check_fs(fs, bsect); /* Load sector 0 and check if it is an FAT-VBR as SFD */
if (fmt == 2 || (fmt < 2 && LD2PT(vol) != 0)) { /* Not an FAT-VBR or forced partition number */
for (i = 0; i < 4; i++) { /* Get partition offset */
pt = fs->win + (MBR_Table + i * SZ_PTE);
br[i] = pt[PTE_System] ? ld_dword(pt + PTE_StLba) : 0;
}
i = LD2PT(vol); /* Partition number: 0:auto, 1-4:forced */
if (i) i--;
do { /* Find an FAT volume */
bsect = br[i];
fmt = bsect ? check_fs(fs, bsect) : 3; /* Check the partition */
} while (!LD2PT(vol) && fmt >= 2 && ++i < 4);
}
if (fmt == 4) return FR_DISK_ERR; /* An error occured in the disk I/O layer */
if (fmt >= 2) return FR_NO_FILESYSTEM; /* No FAT volume is found */
/* An FAT volume is found. Following code initializes the file system object */
#if _FS_EXFAT
if (fmt == 1) {
QWORD maxlba;
for (i = BPB_ZeroedEx; i < BPB_ZeroedEx + 53 && fs->win[i] == 0; i++) ; /* Check zero filler */
if (i < BPB_ZeroedEx + 53) return FR_NO_FILESYSTEM;
if (ld_word(fs->win + BPB_FSVerEx) != 0x100) return FR_NO_FILESYSTEM; /* Check exFAT revision (Must be 1.0) */
if (1 << fs->win[BPB_BytsPerSecEx] != SS(fs)) /* (BPB_BytsPerSecEx must be equal to the physical sector size) */
return FR_NO_FILESYSTEM;
maxlba = ld_qword(fs->win + BPB_TotSecEx) + bsect; /* Last LBA + 1 of the volume */
if (maxlba >= 0x100000000) return FR_NO_FILESYSTEM; /* (It cannot be handled in 32-bit LBA) */
fs->fsize = ld_dword(fs->win + BPB_FatSzEx); /* Number of sectors per FAT */
fs->n_fats = fs->win[BPB_NumFATsEx]; /* Number of FATs */
if (fs->n_fats != 1) return FR_NO_FILESYSTEM; /* (Supports only 1 FAT) */
fs->csize = 1 << fs->win[BPB_SecPerClusEx]; /* Cluster size */
if (fs->csize == 0) return FR_NO_FILESYSTEM; /* (Must be 1..32768) */
nclst = ld_dword(fs->win + BPB_NumClusEx); /* Number of clusters */
if (nclst > MAX_EXFAT) return FR_NO_FILESYSTEM; /* (Too many clusters) */
fs->n_fatent = nclst + 2;
/* Boundaries and Limits */
fs->volbase = bsect;
fs->database = bsect + ld_dword(fs->win + BPB_DataOfsEx);
fs->fatbase = bsect + ld_dword(fs->win + BPB_FatOfsEx);
if (maxlba < (QWORD)fs->database + nclst * fs->csize) return FR_NO_FILESYSTEM; /* (Volume size must not be smaller than the size requiered) */
fs->dirbase = ld_dword(fs->win + BPB_RootClusEx);
/* Check if bitmap location is in assumption (at the first cluster) */
if (move_window(fs, clust2sect(fs, fs->dirbase)) != FR_OK) return FR_DISK_ERR;
for (i = 0; i < SS(fs); i += SZDIRE) {
if (fs->win[i] == 0x81 && ld_dword(fs->win + i + 20) == 2) break; /* 81 entry with cluster #2? */
}
if (i == SS(fs)) return FR_NO_FILESYSTEM;
#if !_FS_READONLY
fs->last_clst = fs->free_clst = 0xFFFFFFFF; /* Initialize cluster allocation information */
#endif
fmt = FS_EXFAT; /* FAT sub-type */
} else
#endif /* _FS_EXFAT */
{
if (ld_word(fs->win + BPB_BytsPerSec) != SS(fs)) return FR_NO_FILESYSTEM; /* (BPB_BytsPerSec must be equal to the physical sector size) */
fasize = ld_word(fs->win + BPB_FATSz16); /* Number of sectors per FAT */
if (fasize == 0) fasize = ld_dword(fs->win + BPB_FATSz32);
fs->fsize = fasize;
fs->n_fats = fs->win[BPB_NumFATs]; /* Number of FATs */
if (fs->n_fats != 1 && fs->n_fats != 2) return FR_NO_FILESYSTEM; /* (Must be 1 or 2) */
fasize *= fs->n_fats; /* Number of sectors for FAT area */
fs->csize = fs->win[BPB_SecPerClus]; /* Cluster size */
if (fs->csize == 0 || (fs->csize & (fs->csize - 1))) return FR_NO_FILESYSTEM; /* (Must be power of 2) */
fs->n_rootdir = ld_word(fs->win + BPB_RootEntCnt); /* Number of root directory entries */
if (fs->n_rootdir % (SS(fs) / SZDIRE)) return FR_NO_FILESYSTEM; /* (Must be sector aligned) */
tsect = ld_word(fs->win + BPB_TotSec16); /* Number of sectors on the volume */
if (tsect == 0) tsect = ld_dword(fs->win + BPB_TotSec32);
nrsv = ld_word(fs->win + BPB_RsvdSecCnt); /* Number of reserved sectors */
if (nrsv == 0) return FR_NO_FILESYSTEM; /* (Must not be 0) */
/* Determine the FAT sub type */
sysect = nrsv + fasize + fs->n_rootdir / (SS(fs) / SZDIRE); /* RSV + FAT + FATFS_DIR */
if (tsect < sysect) return FR_NO_FILESYSTEM; /* (Invalid volume size) */
nclst = (tsect - sysect) / fs->csize; /* Number of clusters */
if (nclst == 0) return FR_NO_FILESYSTEM; /* (Invalid volume size) */
fmt = FS_FAT32;
if (nclst <= MAX_FAT16) fmt = FS_FAT16;
if (nclst <= MAX_FAT12) fmt = FS_FAT12;
/* Boundaries and Limits */
fs->n_fatent = nclst + 2; /* Number of FAT entries */
fs->volbase = bsect; /* Volume start sector */
fs->fatbase = bsect + nrsv; /* FAT start sector */
fs->database = bsect + sysect; /* Data start sector */
if (fmt == FS_FAT32) {
if (ld_word(fs->win + BPB_FSVer32) != 0) return FR_NO_FILESYSTEM; /* (Must be FAT32 revision 0.0) */
if (fs->n_rootdir) return FR_NO_FILESYSTEM; /* (BPB_RootEntCnt must be 0) */
fs->dirbase = ld_dword(fs->win + BPB_RootClus32); /* Root directory start cluster */
szbfat = fs->n_fatent * 4; /* (Needed FAT size) */
} else {
if (fs->n_rootdir == 0) return FR_NO_FILESYSTEM;/* (BPB_RootEntCnt must not be 0) */
fs->dirbase = fs->fatbase + fasize; /* Root directory start sector */
szbfat = (fmt == FS_FAT16) ? /* (Needed FAT size) */
fs->n_fatent * 2 : fs->n_fatent * 3 / 2 + (fs->n_fatent & 1);
}
if (fs->fsize < (szbfat + (SS(fs) - 1)) / SS(fs)) return FR_NO_FILESYSTEM; /* (BPB_FATSz must not be less than the size needed) */
#if !_FS_READONLY
/* Get FSINFO if available */
fs->last_clst = fs->free_clst = 0xFFFFFFFF; /* Initialize cluster allocation information */
fs->fsi_flag = 0x80;
#if (_FS_NOFSINFO & 3) != 3
if (fmt == FS_FAT32 /* Enable FSINFO only if FAT32 and BPB_FSInfo32 == 1 */
&& ld_word(fs->win + BPB_FSInfo32) == 1
&& move_window(fs, bsect + 1) == FR_OK)
{
fs->fsi_flag = 0;
if (ld_word(fs->win + BS_55AA) == 0xAA55 /* Load FSINFO data if available */
&& ld_dword(fs->win + FSI_LeadSig) == 0x41615252
&& ld_dword(fs->win + FSI_StrucSig) == 0x61417272)
{
#if (_FS_NOFSINFO & 1) == 0
fs->free_clst = ld_dword(fs->win + FSI_Free_Count);
#endif
#if (_FS_NOFSINFO & 2) == 0
fs->last_clst = ld_dword(fs->win + FSI_Nxt_Free);
#endif
}
}
#endif /* (_FS_NOFSINFO & 3) != 3 */
#endif /* !_FS_READONLY */
}
fs->fs_type = fmt; /* FAT sub-type */
fs->id = ++Fsid; /* File system mount ID */
#if _USE_LFN == 1
fs->lfnbuf = LfnBuf; /* Static LFN working buffer */
#if _FS_EXFAT
fs->dirbuf = DirBuf; /* Static directory block working buuffer */
#endif
#endif
#if _FS_RPATH != 0
fs->cdir = 0; /* Initialize current directory */
#endif
#if _FS_LOCK != 0 /* Clear file lock semaphores */
clear_lock(fs);
#endif
return FR_OK;
}