FatPkg/EnhancedFatDxe/Init.c - third_party/edk2 - Git at Google

 /** @file
   Initialization routines.

 Copyright (c) 2005 - 2013, Intel Corporation. All rights reserved.<BR>
 This program and the accompanying materials are licensed and made available
 under the terms and conditions of the BSD License which accompanies this
 distribution. The full text of the license may be found at
 http://opensource.org/licenses/bsd-license.php

 THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
 WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.

 **/

 #include "Fat.h"

 /**

   Allocates volume structure, detects FAT file system, installs protocol,
   and initialize cache.

   @param  Handle                - The handle of parent device.
   @param  DiskIo                - The DiskIo of parent device.
   @param  DiskIo2               - The DiskIo2 of parent device.
   @param  BlockIo               - The BlockIo of parent devicel

   @retval EFI_SUCCESS           - Allocate a new volume successfully.
   @retval EFI_OUT_OF_RESOURCES  - Can not allocate the memory.
   @return Others                - Allocating a new volume failed.

 **/
 EFI_STATUS
 FatAllocateVolume (
   IN  EFI_HANDLE                Handle,
   IN  EFI_DISK_IO_PROTOCOL      *DiskIo,
   IN  EFI_DISK_IO2_PROTOCOL     *DiskIo2,
   IN  EFI_BLOCK_IO_PROTOCOL     *BlockIo
   )
 {
   EFI_STATUS  Status;
   FAT_VOLUME  *Volume;

   //
   // Allocate a volume structure
   //
   Volume = AllocateZeroPool (sizeof (FAT_VOLUME));
   if (Volume == NULL) {
     return EFI_OUT_OF_RESOURCES;
   }

   //
   // Initialize the structure
   //
   Volume->Signature                   = FAT_VOLUME_SIGNATURE;
   Volume->Handle                      = Handle;
   Volume->DiskIo                      = DiskIo;
   Volume->DiskIo2                     = DiskIo2;
   Volume->BlockIo                     = BlockIo;
   Volume->MediaId                     = BlockIo->Media->MediaId;
   Volume->ReadOnly                    = BlockIo->Media->ReadOnly;
   Volume->VolumeInterface.Revision    = EFI_SIMPLE_FILE_SYSTEM_PROTOCOL_REVISION;
   Volume->VolumeInterface.OpenVolume  = FatOpenVolume;
   InitializeListHead (&Volume->CheckRef);
   InitializeListHead (&Volume->DirCacheList);
   //
   // Initialize Root Directory entry
   //
   Volume->RootDirEnt.FileString       = Volume->RootFileString;
   Volume->RootDirEnt.Entry.Attributes = FAT_ATTRIBUTE_DIRECTORY;
   //
   // Check to see if there's a file system on the volume
   //
   Status = FatOpenDevice (Volume);
   if (EFI_ERROR (Status)) {
     goto Done;
   }
   //
   // Initialize cache
   //
   Status = FatInitializeDiskCache (Volume);
   if (EFI_ERROR (Status)) {
     goto Done;
   }
   //
   // Install our protocol interfaces on the device's handle
   //
   Status = gBS->InstallMultipleProtocolInterfaces (
                   &Volume->Handle,
                   &gEfiSimpleFileSystemProtocolGuid,
                   &Volume->VolumeInterface,
                   NULL
                   );
   if (EFI_ERROR (Status)) {
     goto Done;
   }
   //
   // Volume installed
   //
   DEBUG ((EFI_D_INIT, "Installed Fat filesystem on %p\n", Handle));
   Volume->Valid = TRUE;

 Done:
   if (EFI_ERROR (Status)) {
     FatFreeVolume (Volume);
   }

   return Status;
 }

 /**

   Called by FatDriverBindingStop(), Abandon the volume.

   @param  Volume                - The volume to be abandoned.

   @retval EFI_SUCCESS           - Abandoned the volume successfully.
   @return Others                - Can not uninstall the protocol interfaces.

 **/
 EFI_STATUS
 FatAbandonVolume (
   IN FAT_VOLUME *Volume
   )
 {
   EFI_STATUS  Status;
   BOOLEAN     LockedByMe;

   //
   // Uninstall the protocol interface.
   //
   if (Volume->Handle != NULL) {
     Status = gBS->UninstallMultipleProtocolInterfaces (
                     Volume->Handle,
                     &gEfiSimpleFileSystemProtocolGuid,
                     &Volume->VolumeInterface,
                     NULL
                     );
     if (EFI_ERROR (Status)) {
       return Status;
     }
   }

   LockedByMe = FALSE;

   //
   // Acquire the lock.
   // If the caller has already acquired the lock (which
   // means we are in the process of some Fat operation),
   // we can not acquire again.
   //
   Status = FatAcquireLockOrFail ();
   if (!EFI_ERROR (Status)) {
     LockedByMe = TRUE;
   }
   //
   // The volume is still being used. Hence, set error flag for all OFiles still in
   // use. In two cases, we could get here. One is EFI_MEDIA_CHANGED, the other is
   // EFI_NO_MEDIA.
   //
   if (Volume->Root != NULL) {
     FatSetVolumeError (
       Volume->Root,
       Volume->BlockIo->Media->MediaPresent ? EFI_MEDIA_CHANGED : EFI_NO_MEDIA
       );
   }

   Volume->Valid = FALSE;

   //
   // Release the lock.
   // If locked by me, this means DriverBindingStop is NOT
   // called within an on-going Fat operation, so we should
   // take responsibility to cleanup and free the volume.
   // Otherwise, the DriverBindingStop is called within an on-going
   // Fat operation, we shouldn't check reference, so just let outer
   // FatCleanupVolume do the task.
   //
   if (LockedByMe) {
     FatCleanupVolume (Volume, NULL, EFI_SUCCESS, NULL);
     FatReleaseLock ();
   }

   return EFI_SUCCESS;
 }

 /**

   Detects FAT file system on Disk and set relevant fields of Volume.

   @param Volume                - The volume structure.

   @retval EFI_SUCCESS           - The Fat File System is detected successfully
   @retval EFI_UNSUPPORTED       - The volume is not FAT file system.
   @retval EFI_VOLUME_CORRUPTED  - The volume is corrupted.

 **/
 EFI_STATUS
 FatOpenDevice (
   IN OUT FAT_VOLUME           *Volume
   )
 {
   EFI_STATUS            Status;
   UINT32                BlockSize;
   UINT32                DirtyMask;
   EFI_DISK_IO_PROTOCOL  *DiskIo;
   FAT_BOOT_SECTOR       FatBs;
   FAT_VOLUME_TYPE       FatType;
   UINTN                 RootDirSectors;
   UINTN                 FatLba;
   UINTN                 RootLba;
   UINTN                 FirstClusterLba;
   UINTN                 Sectors;
   UINTN                 SectorsPerFat;
   UINT8                 SectorsPerClusterAlignment;
   UINT8                 BlockAlignment;

   //
   // Read the FAT_BOOT_SECTOR BPB info
   // This is the only part of FAT code that uses parent DiskIo,
   // Others use FatDiskIo which utilizes a Cache.
   //
   DiskIo  = Volume->DiskIo;
   Status  = DiskIo->ReadDisk (DiskIo, Volume->MediaId, 0, sizeof (FatBs), &FatBs);

   if (EFI_ERROR (Status)) {
     DEBUG ((EFI_D_INIT, "FatOpenDevice: read of part_lba failed %r\n", Status));
     return Status;
   }

   FatType = FatUndefined;

   //
   // Use LargeSectors if Sectors is 0
   //
   Sectors = FatBs.FatBsb.Sectors;
   if (Sectors == 0) {
     Sectors = FatBs.FatBsb.LargeSectors;
   }

   SectorsPerFat = FatBs.FatBsb.SectorsPerFat;
   if (SectorsPerFat == 0) {
     SectorsPerFat = FatBs.FatBse.Fat32Bse.LargeSectorsPerFat;
     FatType       = Fat32;
   }
   //
   // Is boot sector a fat sector?
   // (Note that so far we only know if the sector is FAT32 or not, we don't
   // know if the sector is Fat16 or Fat12 until later when we can compute
   // the volume size)
   //
   if (FatBs.FatBsb.ReservedSectors == 0 || FatBs.FatBsb.NumFats == 0 || Sectors == 0) {
     return EFI_UNSUPPORTED;
   }

   if ((FatBs.FatBsb.SectorSize & (FatBs.FatBsb.SectorSize - 1)) != 0) {
     return EFI_UNSUPPORTED;
   }

   BlockAlignment = (UINT8) HighBitSet32 (FatBs.FatBsb.SectorSize);
   if (BlockAlignment > MAX_BLOCK_ALIGNMENT || BlockAlignment < MIN_BLOCK_ALIGNMENT) {
     return EFI_UNSUPPORTED;
   }

   if ((FatBs.FatBsb.SectorsPerCluster & (FatBs.FatBsb.SectorsPerCluster - 1)) != 0) {
     return EFI_UNSUPPORTED;
   }

   SectorsPerClusterAlignment = (UINT8) HighBitSet32 (FatBs.FatBsb.SectorsPerCluster);
   if (SectorsPerClusterAlignment > MAX_SECTORS_PER_CLUSTER_ALIGNMENT) {
     return EFI_UNSUPPORTED;
   }

   if (FatBs.FatBsb.Media <= 0xf7 &&
       FatBs.FatBsb.Media != 0xf0 &&
       FatBs.FatBsb.Media != 0x00 &&
       FatBs.FatBsb.Media != 0x01
       ) {
     return EFI_UNSUPPORTED;
   }
   //
   // Initialize fields the volume information for this FatType
   //
   if (FatType != Fat32) {
     if (FatBs.FatBsb.RootEntries == 0) {
       return EFI_UNSUPPORTED;
     }
     //
     // Unpack fat12, fat16 info
     //
     Volume->RootEntries = FatBs.FatBsb.RootEntries;
   } else {
     //
     // If this is fat32, refuse to mount mirror-disabled volumes
     //
     if ((SectorsPerFat == 0 || FatBs.FatBse.Fat32Bse.FsVersion != 0) || (FatBs.FatBse.Fat32Bse.ExtendedFlags & 0x80)) {
       return EFI_UNSUPPORTED;
     }
     //
     // Unpack fat32 info
     //
     Volume->RootCluster = FatBs.FatBse.Fat32Bse.RootDirFirstCluster;
   }

   Volume->NumFats           = FatBs.FatBsb.NumFats;
   //
   // Compute some fat locations
   //
   BlockSize                 = FatBs.FatBsb.SectorSize;
   RootDirSectors            = ((Volume->RootEntries * sizeof (FAT_DIRECTORY_ENTRY)) + (BlockSize - 1)) / BlockSize;

   FatLba                    = FatBs.FatBsb.ReservedSectors;
   RootLba                   = FatBs.FatBsb.NumFats * SectorsPerFat + FatLba;
   FirstClusterLba           = RootLba + RootDirSectors;

   Volume->FatPos            = FatLba * BlockSize;
   Volume->FatSize           = SectorsPerFat * BlockSize;

   Volume->VolumeSize        = LShiftU64 (Sectors, BlockAlignment);
   Volume->RootPos           = LShiftU64 (RootLba, BlockAlignment);
   Volume->FirstClusterPos   = LShiftU64 (FirstClusterLba, BlockAlignment);
   Volume->MaxCluster        = (Sectors - FirstClusterLba) >> SectorsPerClusterAlignment;
   Volume->ClusterAlignment  = (UINT8)(BlockAlignment + SectorsPerClusterAlignment);
   Volume->ClusterSize       = (UINTN)1 << (Volume->ClusterAlignment);

   //
   // If this is not a fat32, determine if it's a fat16 or fat12
   //
   if (FatType != Fat32) {
     if (Volume->MaxCluster >= FAT_MAX_FAT16_CLUSTER) {
       return EFI_VOLUME_CORRUPTED;
     }

     FatType = Volume->MaxCluster < FAT_MAX_FAT12_CLUSTER ? Fat12 : Fat16;
     //
     // fat12 & fat16 fat-entries are 2 bytes
     //
     Volume->FatEntrySize = sizeof (UINT16);
     DirtyMask            = FAT16_DIRTY_MASK;
   } else {
     if (Volume->MaxCluster < FAT_MAX_FAT16_CLUSTER) {
       return EFI_VOLUME_CORRUPTED;
     }
     //
     // fat32 fat-entries are 4 bytes
     //
     Volume->FatEntrySize = sizeof (UINT32);
     DirtyMask            = FAT32_DIRTY_MASK;
   }
   //
   // Get the DirtyValue and NotDirtyValue
   // We should keep the initial value as the NotDirtyValue
   // in case the volume is dirty already
   //
   if (FatType != Fat12) {
     Status = FatAccessVolumeDirty (Volume, ReadDisk, &Volume->NotDirtyValue);
     if (EFI_ERROR (Status)) {
       return Status;
     }

     Volume->DirtyValue = Volume->NotDirtyValue & DirtyMask;
   }
   //
   // If present, read the fat hint info
   //
   if (FatType == Fat32) {
     Volume->FreeInfoPos = FatBs.FatBse.Fat32Bse.FsInfoSector * BlockSize;
     if (FatBs.FatBse.Fat32Bse.FsInfoSector != 0) {
       FatDiskIo (Volume, ReadDisk, Volume->FreeInfoPos, sizeof (FAT_INFO_SECTOR), &Volume->FatInfoSector, NULL);
       if (Volume->FatInfoSector.Signature == FAT_INFO_SIGNATURE &&
           Volume->FatInfoSector.InfoBeginSignature == FAT_INFO_BEGIN_SIGNATURE &&
           Volume->FatInfoSector.InfoEndSignature == FAT_INFO_END_SIGNATURE &&
           Volume->FatInfoSector.FreeInfo.ClusterCount <= Volume->MaxCluster
           ) {
         Volume->FreeInfoValid = TRUE;
       }
     }
   }
   //
   // Just make up a FreeInfo.NextCluster for use by allocate cluster
   //
   if (FAT_MIN_CLUSTER > Volume->FatInfoSector.FreeInfo.NextCluster ||
      Volume->FatInfoSector.FreeInfo.NextCluster > Volume->MaxCluster + 1
      ) {
     Volume->FatInfoSector.FreeInfo.NextCluster = FAT_MIN_CLUSTER;
   }
   //
   // We are now defining FAT Type
   //
   Volume->FatType = FatType;
   ASSERT (FatType != FatUndefined);

   return EFI_SUCCESS;
 }
	/** @file
	Initialization routines.

	Copyright (c) 2005 - 2013, Intel Corporation. All rights reserved.<BR>
	This program and the accompanying materials are licensed and made available
	under the terms and conditions of the BSD License which accompanies this
	distribution. The full text of the license may be found at
	http://opensource.org/licenses/bsd-license.php

	THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
	WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.

	**/

	#include "Fat.h"

	/**

	Allocates volume structure, detects FAT file system, installs protocol,
	and initialize cache.

	@param Handle - The handle of parent device.
	@param DiskIo - The DiskIo of parent device.
	@param DiskIo2 - The DiskIo2 of parent device.
	@param BlockIo - The BlockIo of parent devicel

	@retval EFI_SUCCESS - Allocate a new volume successfully.
	@retval EFI_OUT_OF_RESOURCES - Can not allocate the memory.
	@return Others - Allocating a new volume failed.

	**/
	EFI_STATUS
	FatAllocateVolume (
	IN EFI_HANDLE Handle,
	IN EFI_DISK_IO_PROTOCOL *DiskIo,
	IN EFI_DISK_IO2_PROTOCOL *DiskIo2,
	IN EFI_BLOCK_IO_PROTOCOL *BlockIo
	)
	{
	EFI_STATUS Status;
	FAT_VOLUME *Volume;

	//
	// Allocate a volume structure
	//
	Volume = AllocateZeroPool (sizeof (FAT_VOLUME));
	if (Volume == NULL) {
	return EFI_OUT_OF_RESOURCES;
	}

	//
	// Initialize the structure
	//
	Volume->Signature = FAT_VOLUME_SIGNATURE;
	Volume->Handle = Handle;
	Volume->DiskIo = DiskIo;
	Volume->DiskIo2 = DiskIo2;
	Volume->BlockIo = BlockIo;
	Volume->MediaId = BlockIo->Media->MediaId;
	Volume->ReadOnly = BlockIo->Media->ReadOnly;
	Volume->VolumeInterface.Revision = EFI_SIMPLE_FILE_SYSTEM_PROTOCOL_REVISION;
	Volume->VolumeInterface.OpenVolume = FatOpenVolume;
	InitializeListHead (&Volume->CheckRef);
	InitializeListHead (&Volume->DirCacheList);
	//
	// Initialize Root Directory entry
	//
	Volume->RootDirEnt.FileString = Volume->RootFileString;
	Volume->RootDirEnt.Entry.Attributes = FAT_ATTRIBUTE_DIRECTORY;
	//
	// Check to see if there's a file system on the volume
	//
	Status = FatOpenDevice (Volume);
	if (EFI_ERROR (Status)) {
	goto Done;
	}
	//
	// Initialize cache
	//
	Status = FatInitializeDiskCache (Volume);
	if (EFI_ERROR (Status)) {
	goto Done;
	}
	//
	// Install our protocol interfaces on the device's handle
	//
	Status = gBS->InstallMultipleProtocolInterfaces (
	&Volume->Handle,
	&gEfiSimpleFileSystemProtocolGuid,
	&Volume->VolumeInterface,
	NULL
	);
	if (EFI_ERROR (Status)) {
	goto Done;
	}
	//
	// Volume installed
	//
	DEBUG ((EFI_D_INIT, "Installed Fat filesystem on %p\n", Handle));
	Volume->Valid = TRUE;

	Done:
	if (EFI_ERROR (Status)) {
	FatFreeVolume (Volume);
	}

	return Status;
	}

	/**

	Called by FatDriverBindingStop(), Abandon the volume.

	@param Volume - The volume to be abandoned.

	@retval EFI_SUCCESS - Abandoned the volume successfully.
	@return Others - Can not uninstall the protocol interfaces.

	**/
	EFI_STATUS
	FatAbandonVolume (
	IN FAT_VOLUME *Volume
	)
	{
	EFI_STATUS Status;
	BOOLEAN LockedByMe;

	//
	// Uninstall the protocol interface.
	//
	if (Volume->Handle != NULL) {
	Status = gBS->UninstallMultipleProtocolInterfaces (
	Volume->Handle,
	&gEfiSimpleFileSystemProtocolGuid,
	&Volume->VolumeInterface,
	NULL
	);
	if (EFI_ERROR (Status)) {
	return Status;
	}
	}

	LockedByMe = FALSE;

	//
	// Acquire the lock.
	// If the caller has already acquired the lock (which
	// means we are in the process of some Fat operation),
	// we can not acquire again.
	//
	Status = FatAcquireLockOrFail ();
	if (!EFI_ERROR (Status)) {
	LockedByMe = TRUE;
	}
	//
	// The volume is still being used. Hence, set error flag for all OFiles still in
	// use. In two cases, we could get here. One is EFI_MEDIA_CHANGED, the other is
	// EFI_NO_MEDIA.
	//
	if (Volume->Root != NULL) {
	FatSetVolumeError (
	Volume->Root,
	Volume->BlockIo->Media->MediaPresent ? EFI_MEDIA_CHANGED : EFI_NO_MEDIA
	);
	}

	Volume->Valid = FALSE;

	//
	// Release the lock.
	// If locked by me, this means DriverBindingStop is NOT
	// called within an on-going Fat operation, so we should
	// take responsibility to cleanup and free the volume.
	// Otherwise, the DriverBindingStop is called within an on-going
	// Fat operation, we shouldn't check reference, so just let outer
	// FatCleanupVolume do the task.
	//
	if (LockedByMe) {
	FatCleanupVolume (Volume, NULL, EFI_SUCCESS, NULL);
	FatReleaseLock ();
	}

	return EFI_SUCCESS;
	}

	/**

	Detects FAT file system on Disk and set relevant fields of Volume.

	@param Volume - The volume structure.

	@retval EFI_SUCCESS - The Fat File System is detected successfully
	@retval EFI_UNSUPPORTED - The volume is not FAT file system.
	@retval EFI_VOLUME_CORRUPTED - The volume is corrupted.

	**/
	EFI_STATUS
	FatOpenDevice (
	IN OUT FAT_VOLUME *Volume
	)
	{
	EFI_STATUS Status;
	UINT32 BlockSize;
	UINT32 DirtyMask;
	EFI_DISK_IO_PROTOCOL *DiskIo;
	FAT_BOOT_SECTOR FatBs;
	FAT_VOLUME_TYPE FatType;
	UINTN RootDirSectors;
	UINTN FatLba;
	UINTN RootLba;
	UINTN FirstClusterLba;
	UINTN Sectors;
	UINTN SectorsPerFat;
	UINT8 SectorsPerClusterAlignment;
	UINT8 BlockAlignment;

	//
	// Read the FAT_BOOT_SECTOR BPB info
	// This is the only part of FAT code that uses parent DiskIo,
	// Others use FatDiskIo which utilizes a Cache.
	//
	DiskIo = Volume->DiskIo;
	Status = DiskIo->ReadDisk (DiskIo, Volume->MediaId, 0, sizeof (FatBs), &FatBs);

	if (EFI_ERROR (Status)) {
	DEBUG ((EFI_D_INIT, "FatOpenDevice: read of part_lba failed %r\n", Status));
	return Status;
	}

	FatType = FatUndefined;

	//
	// Use LargeSectors if Sectors is 0
	//
	Sectors = FatBs.FatBsb.Sectors;
	if (Sectors == 0) {
	Sectors = FatBs.FatBsb.LargeSectors;
	}

	SectorsPerFat = FatBs.FatBsb.SectorsPerFat;
	if (SectorsPerFat == 0) {
	SectorsPerFat = FatBs.FatBse.Fat32Bse.LargeSectorsPerFat;
	FatType = Fat32;
	}
	//
	// Is boot sector a fat sector?
	// (Note that so far we only know if the sector is FAT32 or not, we don't
	// know if the sector is Fat16 or Fat12 until later when we can compute
	// the volume size)
	//
	if (FatBs.FatBsb.ReservedSectors == 0 \|\| FatBs.FatBsb.NumFats == 0 \|\| Sectors == 0) {
	return EFI_UNSUPPORTED;
	}

	if ((FatBs.FatBsb.SectorSize & (FatBs.FatBsb.SectorSize - 1)) != 0) {
	return EFI_UNSUPPORTED;
	}

	BlockAlignment = (UINT8) HighBitSet32 (FatBs.FatBsb.SectorSize);
	if (BlockAlignment > MAX_BLOCK_ALIGNMENT \|\| BlockAlignment < MIN_BLOCK_ALIGNMENT) {
	return EFI_UNSUPPORTED;
	}

	if ((FatBs.FatBsb.SectorsPerCluster & (FatBs.FatBsb.SectorsPerCluster - 1)) != 0) {
	return EFI_UNSUPPORTED;
	}

	SectorsPerClusterAlignment = (UINT8) HighBitSet32 (FatBs.FatBsb.SectorsPerCluster);
	if (SectorsPerClusterAlignment > MAX_SECTORS_PER_CLUSTER_ALIGNMENT) {
	return EFI_UNSUPPORTED;
	}

	if (FatBs.FatBsb.Media <= 0xf7 &&
	FatBs.FatBsb.Media != 0xf0 &&
	FatBs.FatBsb.Media != 0x00 &&
	FatBs.FatBsb.Media != 0x01
	) {
	return EFI_UNSUPPORTED;
	}
	//
	// Initialize fields the volume information for this FatType
	//
	if (FatType != Fat32) {
	if (FatBs.FatBsb.RootEntries == 0) {
	return EFI_UNSUPPORTED;
	}
	//
	// Unpack fat12, fat16 info
	//
	Volume->RootEntries = FatBs.FatBsb.RootEntries;
	} else {
	//
	// If this is fat32, refuse to mount mirror-disabled volumes
	//
	if ((SectorsPerFat == 0 \|\| FatBs.FatBse.Fat32Bse.FsVersion != 0) \|\| (FatBs.FatBse.Fat32Bse.ExtendedFlags & 0x80)) {
	return EFI_UNSUPPORTED;
	}
	//
	// Unpack fat32 info
	//
	Volume->RootCluster = FatBs.FatBse.Fat32Bse.RootDirFirstCluster;
	}

	Volume->NumFats = FatBs.FatBsb.NumFats;
	//
	// Compute some fat locations
	//
	BlockSize = FatBs.FatBsb.SectorSize;
	RootDirSectors = ((Volume->RootEntries * sizeof (FAT_DIRECTORY_ENTRY)) + (BlockSize - 1)) / BlockSize;

	FatLba = FatBs.FatBsb.ReservedSectors;
	RootLba = FatBs.FatBsb.NumFats * SectorsPerFat + FatLba;
	FirstClusterLba = RootLba + RootDirSectors;

	Volume->FatPos = FatLba * BlockSize;
	Volume->FatSize = SectorsPerFat * BlockSize;

	Volume->VolumeSize = LShiftU64 (Sectors, BlockAlignment);
	Volume->RootPos = LShiftU64 (RootLba, BlockAlignment);
	Volume->FirstClusterPos = LShiftU64 (FirstClusterLba, BlockAlignment);
	Volume->MaxCluster = (Sectors - FirstClusterLba) >> SectorsPerClusterAlignment;
	Volume->ClusterAlignment = (UINT8)(BlockAlignment + SectorsPerClusterAlignment);
	Volume->ClusterSize = (UINTN)1 << (Volume->ClusterAlignment);

	//
	// If this is not a fat32, determine if it's a fat16 or fat12
	//
	if (FatType != Fat32) {
	if (Volume->MaxCluster >= FAT_MAX_FAT16_CLUSTER) {
	return EFI_VOLUME_CORRUPTED;
	}

	FatType = Volume->MaxCluster < FAT_MAX_FAT12_CLUSTER ? Fat12 : Fat16;
	//
	// fat12 & fat16 fat-entries are 2 bytes
	//
	Volume->FatEntrySize = sizeof (UINT16);
	DirtyMask = FAT16_DIRTY_MASK;
	} else {
	if (Volume->MaxCluster < FAT_MAX_FAT16_CLUSTER) {
	return EFI_VOLUME_CORRUPTED;
	}
	//
	// fat32 fat-entries are 4 bytes
	//
	Volume->FatEntrySize = sizeof (UINT32);
	DirtyMask = FAT32_DIRTY_MASK;
	}
	//
	// Get the DirtyValue and NotDirtyValue
	// We should keep the initial value as the NotDirtyValue
	// in case the volume is dirty already
	//
	if (FatType != Fat12) {
	Status = FatAccessVolumeDirty (Volume, ReadDisk, &Volume->NotDirtyValue);
	if (EFI_ERROR (Status)) {
	return Status;
	}

	Volume->DirtyValue = Volume->NotDirtyValue & DirtyMask;
	}
	//
	// If present, read the fat hint info
	//
	if (FatType == Fat32) {
	Volume->FreeInfoPos = FatBs.FatBse.Fat32Bse.FsInfoSector * BlockSize;
	if (FatBs.FatBse.Fat32Bse.FsInfoSector != 0) {
	FatDiskIo (Volume, ReadDisk, Volume->FreeInfoPos, sizeof (FAT_INFO_SECTOR), &Volume->FatInfoSector, NULL);
	if (Volume->FatInfoSector.Signature == FAT_INFO_SIGNATURE &&
	Volume->FatInfoSector.InfoBeginSignature == FAT_INFO_BEGIN_SIGNATURE &&
	Volume->FatInfoSector.InfoEndSignature == FAT_INFO_END_SIGNATURE &&
	Volume->FatInfoSector.FreeInfo.ClusterCount <= Volume->MaxCluster
	) {
	Volume->FreeInfoValid = TRUE;
	}
	}
	}
	//
	// Just make up a FreeInfo.NextCluster for use by allocate cluster
	//
	if (FAT_MIN_CLUSTER > Volume->FatInfoSector.FreeInfo.NextCluster \|\|
	Volume->FatInfoSector.FreeInfo.NextCluster > Volume->MaxCluster + 1
	) {
	Volume->FatInfoSector.FreeInfo.NextCluster = FAT_MIN_CLUSTER;
	}
	//
	// We are now defining FAT Type
	//
	Volume->FatType = FatType;
	ASSERT (FatType != FatUndefined);

	return EFI_SUCCESS;
	}