fs/yaffs2/yaffs_checkptrw.c - platform/external/u-boot - Gitiles

 /*
  * YAFFS: Yet Another Flash File System. A NAND-flash specific file system.
  *
  * Copyright (C) 2002-2007 Aleph One Ltd.
  *   for Toby Churchill Ltd and Brightstar Engineering
  *
  * Created by Charles Manning <charles@aleph1.co.uk>
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2 as
  * published by the Free Software Foundation.
  */

 const char *yaffs_checkptrw_c_version =
     "$Id: yaffs_checkptrw.c,v 1.14 2007/05/15 20:07:40 charles Exp $";


 #include "yaffs_checkptrw.h"


 static int yaffs_CheckpointSpaceOk(yaffs_Device *dev)
 {

 	int blocksAvailable = dev->nErasedBlocks - dev->nReservedBlocks;

 	T(YAFFS_TRACE_CHECKPOINT,
 		(TSTR("checkpt blocks available = %d" TENDSTR),
 		blocksAvailable));


 	return (blocksAvailable <= 0) ? 0 : 1;
 }


 static int yaffs_CheckpointErase(yaffs_Device *dev)
 {

 	int i;


 	if(!dev->eraseBlockInNAND)
 		return 0;
 	T(YAFFS_TRACE_CHECKPOINT,(TSTR("checking blocks %d to %d"TENDSTR),
 		dev->internalStartBlock,dev->internalEndBlock));

 	for(i = dev->internalStartBlock; i <= dev->internalEndBlock; i++) {
 		yaffs_BlockInfo *bi = yaffs_GetBlockInfo(dev,i);
 		if(bi->blockState == YAFFS_BLOCK_STATE_CHECKPOINT){
 			T(YAFFS_TRACE_CHECKPOINT,(TSTR("erasing checkpt block %d"TENDSTR),i));
 			if(dev->eraseBlockInNAND(dev,i- dev->blockOffset /* realign */)){
 				bi->blockState = YAFFS_BLOCK_STATE_EMPTY;
 				dev->nErasedBlocks++;
 				dev->nFreeChunks += dev->nChunksPerBlock;
 			}
 			else {
 				dev->markNANDBlockBad(dev,i);
 				bi->blockState = YAFFS_BLOCK_STATE_DEAD;
 			}
 		}
 	}

 	dev->blocksInCheckpoint = 0;

 	return 1;
 }


 static void yaffs_CheckpointFindNextErasedBlock(yaffs_Device *dev)
 {
 	int  i;
 	int blocksAvailable = dev->nErasedBlocks - dev->nReservedBlocks;
 	T(YAFFS_TRACE_CHECKPOINT,
 		(TSTR("allocating checkpt block: erased %d reserved %d avail %d next %d "TENDSTR),
 		dev->nErasedBlocks,dev->nReservedBlocks,blocksAvailable,dev->checkpointNextBlock));

 	if(dev->checkpointNextBlock >= 0 &&
 	   dev->checkpointNextBlock <= dev->internalEndBlock &&
 	   blocksAvailable > 0){

 		for(i = dev->checkpointNextBlock; i <= dev->internalEndBlock; i++){
 			yaffs_BlockInfo *bi = yaffs_GetBlockInfo(dev,i);
 			if(bi->blockState == YAFFS_BLOCK_STATE_EMPTY){
 				dev->checkpointNextBlock = i + 1;
 				dev->checkpointCurrentBlock = i;
 				T(YAFFS_TRACE_CHECKPOINT,(TSTR("allocating checkpt block %d"TENDSTR),i));
 				return;
 			}
 		}
 	}
 	T(YAFFS_TRACE_CHECKPOINT,(TSTR("out of checkpt blocks"TENDSTR)));

 	dev->checkpointNextBlock = -1;
 	dev->checkpointCurrentBlock = -1;
 }

 static void yaffs_CheckpointFindNextCheckpointBlock(yaffs_Device *dev)
 {
 	int  i;
 	yaffs_ExtendedTags tags;

 	T(YAFFS_TRACE_CHECKPOINT,(TSTR("find next checkpt block: start:  blocks %d next %d" TENDSTR),
 		dev->blocksInCheckpoint, dev->checkpointNextBlock));

 	if(dev->blocksInCheckpoint < dev->checkpointMaxBlocks)
 		for(i = dev->checkpointNextBlock; i <= dev->internalEndBlock; i++){
 			int chunk = i * dev->nChunksPerBlock;
 			int realignedChunk = chunk - dev->chunkOffset;

 			dev->readChunkWithTagsFromNAND(dev,realignedChunk,NULL,&tags);
 			T(YAFFS_TRACE_CHECKPOINT,(TSTR("find next checkpt block: search: block %d oid %d seq %d eccr %d" TENDSTR),
 				i, tags.objectId,tags.sequenceNumber,tags.eccResult));

 			if(tags.sequenceNumber == YAFFS_SEQUENCE_CHECKPOINT_DATA){
 				/* Right kind of block */
 				dev->checkpointNextBlock = tags.objectId;
 				dev->checkpointCurrentBlock = i;
 				dev->checkpointBlockList[dev->blocksInCheckpoint] = i;
 				dev->blocksInCheckpoint++;
 				T(YAFFS_TRACE_CHECKPOINT,(TSTR("found checkpt block %d"TENDSTR),i));
 				return;
 			}
 		}

 	T(YAFFS_TRACE_CHECKPOINT,(TSTR("found no more checkpt blocks"TENDSTR)));

 	dev->checkpointNextBlock = -1;
 	dev->checkpointCurrentBlock = -1;
 }


 int yaffs_CheckpointOpen(yaffs_Device *dev, int forWriting)
 {

 	/* Got the functions we need? */
 	if (!dev->writeChunkWithTagsToNAND ||
 	    !dev->readChunkWithTagsFromNAND ||
 	    !dev->eraseBlockInNAND ||
 	    !dev->markNANDBlockBad)
 		return 0;

 	if(forWriting && !yaffs_CheckpointSpaceOk(dev))
 		return 0;

 	if(!dev->checkpointBuffer)
 		dev->checkpointBuffer = YMALLOC_DMA(dev->nDataBytesPerChunk);
 	if(!dev->checkpointBuffer)
 		return 0;


 	dev->checkpointPageSequence = 0;

 	dev->checkpointOpenForWrite = forWriting;

 	dev->checkpointByteCount = 0;
 	dev->checkpointSum = 0;
 	dev->checkpointXor = 0;
 	dev->checkpointCurrentBlock = -1;
 	dev->checkpointCurrentChunk = -1;
 	dev->checkpointNextBlock = dev->internalStartBlock;

 	/* Erase all the blocks in the checkpoint area */
 	if(forWriting){
 		memset(dev->checkpointBuffer,0,dev->nDataBytesPerChunk);
 		dev->checkpointByteOffset = 0;
 		return yaffs_CheckpointErase(dev);


 	} else {
 		int i;
 		/* Set to a value that will kick off a read */
 		dev->checkpointByteOffset = dev->nDataBytesPerChunk;
 		/* A checkpoint block list of 1 checkpoint block per 16 block is (hopefully)
 		 * going to be way more than we need */
 		dev->blocksInCheckpoint = 0;
 		dev->checkpointMaxBlocks = (dev->internalEndBlock - dev->internalStartBlock)/16 + 2;
 		dev->checkpointBlockList = YMALLOC(sizeof(int) * dev->checkpointMaxBlocks);
 		for(i = 0; i < dev->checkpointMaxBlocks; i++)
 			dev->checkpointBlockList[i] = -1;
 	}

 	return 1;
 }

 int yaffs_GetCheckpointSum(yaffs_Device *dev, __u32 *sum)
 {
 	__u32 compositeSum;
 	compositeSum =  (dev->checkpointSum << 8) | (dev->checkpointXor & 0xFF);
 	*sum = compositeSum;
 	return 1;
 }

 static int yaffs_CheckpointFlushBuffer(yaffs_Device *dev)
 {

 	int chunk;
 	int realignedChunk;

 	yaffs_ExtendedTags tags;

 	if(dev->checkpointCurrentBlock < 0){
 		yaffs_CheckpointFindNextErasedBlock(dev);
 		dev->checkpointCurrentChunk = 0;
 	}

 	if(dev->checkpointCurrentBlock < 0)
 		return 0;

 	tags.chunkDeleted = 0;
 	tags.objectId = dev->checkpointNextBlock; /* Hint to next place to look */
 	tags.chunkId = dev->checkpointPageSequence + 1;
 	tags.sequenceNumber =  YAFFS_SEQUENCE_CHECKPOINT_DATA;
 	tags.byteCount = dev->nDataBytesPerChunk;
 	if(dev->checkpointCurrentChunk == 0){
 		/* First chunk we write for the block? Set block state to
 		   checkpoint */
 		yaffs_BlockInfo *bi = yaffs_GetBlockInfo(dev,dev->checkpointCurrentBlock);
 		bi->blockState = YAFFS_BLOCK_STATE_CHECKPOINT;
 		dev->blocksInCheckpoint++;
 	}

 	chunk = dev->checkpointCurrentBlock * dev->nChunksPerBlock + dev->checkpointCurrentChunk;


 	T(YAFFS_TRACE_CHECKPOINT,(TSTR("checkpoint wite buffer nand %d(%d:%d) objid %d chId %d" TENDSTR),
 		chunk, dev->checkpointCurrentBlock, dev->checkpointCurrentChunk,tags.objectId,tags.chunkId));

 	realignedChunk = chunk - dev->chunkOffset;

 	dev->writeChunkWithTagsToNAND(dev,realignedChunk,dev->checkpointBuffer,&tags);
 	dev->checkpointByteOffset = 0;
 	dev->checkpointPageSequence++;
 	dev->checkpointCurrentChunk++;
 	if(dev->checkpointCurrentChunk >= dev->nChunksPerBlock){
 		dev->checkpointCurrentChunk = 0;
 		dev->checkpointCurrentBlock = -1;
 	}
 	memset(dev->checkpointBuffer,0,dev->nDataBytesPerChunk);

 	return 1;
 }


 int yaffs_CheckpointWrite(yaffs_Device *dev,const void *data, int nBytes)
 {
 	int i=0;
 	int ok = 1;


 	__u8 * dataBytes = (__u8 *)data;


 	if(!dev->checkpointBuffer)
 		return 0;

 	if(!dev->checkpointOpenForWrite)
 		return -1;

 	while(i < nBytes && ok) {


 		dev->checkpointBuffer[dev->checkpointByteOffset] = *dataBytes ;
 		dev->checkpointSum += *dataBytes;
 		dev->checkpointXor ^= *dataBytes;

 		dev->checkpointByteOffset++;
 		i++;
 		dataBytes++;
 		dev->checkpointByteCount++;


 		if(dev->checkpointByteOffset < 0 ||
 		   dev->checkpointByteOffset >= dev->nDataBytesPerChunk)
 			ok = yaffs_CheckpointFlushBuffer(dev);

 	}

 	return 	i;
 }

 int yaffs_CheckpointRead(yaffs_Device *dev, void *data, int nBytes)
 {
 	int i=0;
 	int ok = 1;
 	yaffs_ExtendedTags tags;


 	int chunk;
 	int realignedChunk;

 	__u8 *dataBytes = (__u8 *)data;

 	if(!dev->checkpointBuffer)
 		return 0;

 	if(dev->checkpointOpenForWrite)
 		return -1;

 	while(i < nBytes && ok) {


 		if(dev->checkpointByteOffset < 0 ||
 		   dev->checkpointByteOffset >= dev->nDataBytesPerChunk) {

 		   	if(dev->checkpointCurrentBlock < 0){
 				yaffs_CheckpointFindNextCheckpointBlock(dev);
 				dev->checkpointCurrentChunk = 0;
 			}

 			if(dev->checkpointCurrentBlock < 0)
 				ok = 0;
 			else {

 				chunk = dev->checkpointCurrentBlock * dev->nChunksPerBlock +
 				          dev->checkpointCurrentChunk;

 				realignedChunk = chunk - dev->chunkOffset;

 	   			/* read in the next chunk */
 	   			/* printf("read checkpoint page %d\n",dev->checkpointPage); */
 				dev->readChunkWithTagsFromNAND(dev, realignedChunk,
 							       dev->checkpointBuffer,
 							      &tags);

 				if(tags.chunkId != (dev->checkpointPageSequence + 1) ||
 				   tags.sequenceNumber != YAFFS_SEQUENCE_CHECKPOINT_DATA)
 				   ok = 0;

 				dev->checkpointByteOffset = 0;
 				dev->checkpointPageSequence++;
 				dev->checkpointCurrentChunk++;

 				if(dev->checkpointCurrentChunk >= dev->nChunksPerBlock)
 					dev->checkpointCurrentBlock = -1;
 			}
 		}

 		if(ok){
 			*dataBytes = dev->checkpointBuffer[dev->checkpointByteOffset];
 			dev->checkpointSum += *dataBytes;
 			dev->checkpointXor ^= *dataBytes;
 			dev->checkpointByteOffset++;
 			i++;
 			dataBytes++;
 			dev->checkpointByteCount++;
 		}
 	}

 	return 	i;
 }

 int yaffs_CheckpointClose(yaffs_Device *dev)
 {

 	if(dev->checkpointOpenForWrite){
 		if(dev->checkpointByteOffset != 0)
 			yaffs_CheckpointFlushBuffer(dev);
 	} else {
 		int i;
 		for(i = 0; i < dev->blocksInCheckpoint && dev->checkpointBlockList[i] >= 0; i++){
 			yaffs_BlockInfo *bi = yaffs_GetBlockInfo(dev,dev->checkpointBlockList[i]);
 			if(bi->blockState == YAFFS_BLOCK_STATE_EMPTY)
 				bi->blockState = YAFFS_BLOCK_STATE_CHECKPOINT;
 			else {
 				// Todo this looks odd...
 			}
 		}
 		YFREE(dev->checkpointBlockList);
 		dev->checkpointBlockList = NULL;
 	}

 	dev->nFreeChunks -= dev->blocksInCheckpoint * dev->nChunksPerBlock;
 	dev->nErasedBlocks -= dev->blocksInCheckpoint;


 	T(YAFFS_TRACE_CHECKPOINT,(TSTR("checkpoint byte count %d" TENDSTR),
 			dev->checkpointByteCount));

 	if(dev->checkpointBuffer){
 		/* free the buffer */
 		YFREE(dev->checkpointBuffer);
 		dev->checkpointBuffer = NULL;
 		return 1;
 	}
 	else
 		return 0;

 }

 int yaffs_CheckpointInvalidateStream(yaffs_Device *dev)
 {
 	/* Erase the first checksum block */

 	T(YAFFS_TRACE_CHECKPOINT,(TSTR("checkpoint invalidate"TENDSTR)));

 	if(!yaffs_CheckpointSpaceOk(dev))
 		return 0;

 	return yaffs_CheckpointErase(dev);
 }
	/*
	* YAFFS: Yet Another Flash File System. A NAND-flash specific file system.
	*
	* Copyright (C) 2002-2007 Aleph One Ltd.
	* for Toby Churchill Ltd and Brightstar Engineering
	*
	* Created by Charles Manning <charles@aleph1.co.uk>
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License version 2 as
	* published by the Free Software Foundation.
	*/

	const char *yaffs_checkptrw_c_version =
	"$Id: yaffs_checkptrw.c,v 1.14 2007/05/15 20:07:40 charles Exp $";


	#include "yaffs_checkptrw.h"


	static int yaffs_CheckpointSpaceOk(yaffs_Device *dev)
	{

	int blocksAvailable = dev->nErasedBlocks - dev->nReservedBlocks;

	T(YAFFS_TRACE_CHECKPOINT,
	(TSTR("checkpt blocks available = %d" TENDSTR),
	blocksAvailable));


	return (blocksAvailable <= 0) ? 0 : 1;
	}


	static int yaffs_CheckpointErase(yaffs_Device *dev)
	{

	int i;


	if(!dev->eraseBlockInNAND)
	return 0;
	T(YAFFS_TRACE_CHECKPOINT,(TSTR("checking blocks %d to %d"TENDSTR),
	dev->internalStartBlock,dev->internalEndBlock));

	for(i = dev->internalStartBlock; i <= dev->internalEndBlock; i++) {
	yaffs_BlockInfo *bi = yaffs_GetBlockInfo(dev,i);
	if(bi->blockState == YAFFS_BLOCK_STATE_CHECKPOINT){
	T(YAFFS_TRACE_CHECKPOINT,(TSTR("erasing checkpt block %d"TENDSTR),i));
	if(dev->eraseBlockInNAND(dev,i- dev->blockOffset /* realign */)){
	bi->blockState = YAFFS_BLOCK_STATE_EMPTY;
	dev->nErasedBlocks++;
	dev->nFreeChunks += dev->nChunksPerBlock;
	}
	else {
	dev->markNANDBlockBad(dev,i);
	bi->blockState = YAFFS_BLOCK_STATE_DEAD;
	}
	}
	}

	dev->blocksInCheckpoint = 0;

	return 1;
	}


	static void yaffs_CheckpointFindNextErasedBlock(yaffs_Device *dev)
	{
	int i;
	int blocksAvailable = dev->nErasedBlocks - dev->nReservedBlocks;
	T(YAFFS_TRACE_CHECKPOINT,
	(TSTR("allocating checkpt block: erased %d reserved %d avail %d next %d "TENDSTR),
	dev->nErasedBlocks,dev->nReservedBlocks,blocksAvailable,dev->checkpointNextBlock));

	if(dev->checkpointNextBlock >= 0 &&
	dev->checkpointNextBlock <= dev->internalEndBlock &&
	blocksAvailable > 0){

	for(i = dev->checkpointNextBlock; i <= dev->internalEndBlock; i++){
	yaffs_BlockInfo *bi = yaffs_GetBlockInfo(dev,i);
	if(bi->blockState == YAFFS_BLOCK_STATE_EMPTY){
	dev->checkpointNextBlock = i + 1;
	dev->checkpointCurrentBlock = i;
	T(YAFFS_TRACE_CHECKPOINT,(TSTR("allocating checkpt block %d"TENDSTR),i));
	return;
	}
	}
	}
	T(YAFFS_TRACE_CHECKPOINT,(TSTR("out of checkpt blocks"TENDSTR)));

	dev->checkpointNextBlock = -1;
	dev->checkpointCurrentBlock = -1;
	}

	static void yaffs_CheckpointFindNextCheckpointBlock(yaffs_Device *dev)
	{
	int i;
	yaffs_ExtendedTags tags;

	T(YAFFS_TRACE_CHECKPOINT,(TSTR("find next checkpt block: start: blocks %d next %d" TENDSTR),
	dev->blocksInCheckpoint, dev->checkpointNextBlock));

	if(dev->blocksInCheckpoint < dev->checkpointMaxBlocks)
	for(i = dev->checkpointNextBlock; i <= dev->internalEndBlock; i++){
	int chunk = i * dev->nChunksPerBlock;
	int realignedChunk = chunk - dev->chunkOffset;

	dev->readChunkWithTagsFromNAND(dev,realignedChunk,NULL,&tags);
	T(YAFFS_TRACE_CHECKPOINT,(TSTR("find next checkpt block: search: block %d oid %d seq %d eccr %d" TENDSTR),
	i, tags.objectId,tags.sequenceNumber,tags.eccResult));

	if(tags.sequenceNumber == YAFFS_SEQUENCE_CHECKPOINT_DATA){
	/* Right kind of block */
	dev->checkpointNextBlock = tags.objectId;
	dev->checkpointCurrentBlock = i;
	dev->checkpointBlockList[dev->blocksInCheckpoint] = i;
	dev->blocksInCheckpoint++;
	T(YAFFS_TRACE_CHECKPOINT,(TSTR("found checkpt block %d"TENDSTR),i));
	return;
	}
	}

	T(YAFFS_TRACE_CHECKPOINT,(TSTR("found no more checkpt blocks"TENDSTR)));

	dev->checkpointNextBlock = -1;
	dev->checkpointCurrentBlock = -1;
	}


	int yaffs_CheckpointOpen(yaffs_Device *dev, int forWriting)
	{

	/* Got the functions we need? */
	if (!dev->writeChunkWithTagsToNAND \|\|
	!dev->readChunkWithTagsFromNAND \|\|
	!dev->eraseBlockInNAND \|\|
	!dev->markNANDBlockBad)
	return 0;

	if(forWriting && !yaffs_CheckpointSpaceOk(dev))
	return 0;

	if(!dev->checkpointBuffer)
	dev->checkpointBuffer = YMALLOC_DMA(dev->nDataBytesPerChunk);
	if(!dev->checkpointBuffer)
	return 0;


	dev->checkpointPageSequence = 0;

	dev->checkpointOpenForWrite = forWriting;

	dev->checkpointByteCount = 0;
	dev->checkpointSum = 0;
	dev->checkpointXor = 0;
	dev->checkpointCurrentBlock = -1;
	dev->checkpointCurrentChunk = -1;
	dev->checkpointNextBlock = dev->internalStartBlock;

	/* Erase all the blocks in the checkpoint area */
	if(forWriting){
	memset(dev->checkpointBuffer,0,dev->nDataBytesPerChunk);
	dev->checkpointByteOffset = 0;
	return yaffs_CheckpointErase(dev);


	} else {
	int i;
	/* Set to a value that will kick off a read */
	dev->checkpointByteOffset = dev->nDataBytesPerChunk;
	/* A checkpoint block list of 1 checkpoint block per 16 block is (hopefully)
	* going to be way more than we need */
	dev->blocksInCheckpoint = 0;
	dev->checkpointMaxBlocks = (dev->internalEndBlock - dev->internalStartBlock)/16 + 2;
	dev->checkpointBlockList = YMALLOC(sizeof(int) * dev->checkpointMaxBlocks);
	for(i = 0; i < dev->checkpointMaxBlocks; i++)
	dev->checkpointBlockList[i] = -1;
	}

	return 1;
	}

	int yaffs_GetCheckpointSum(yaffs_Device dev, __u32 sum)
	{
	__u32 compositeSum;
	compositeSum = (dev->checkpointSum << 8) \| (dev->checkpointXor & 0xFF);
	*sum = compositeSum;
	return 1;
	}

	static int yaffs_CheckpointFlushBuffer(yaffs_Device *dev)
	{

	int chunk;
	int realignedChunk;

	yaffs_ExtendedTags tags;

	if(dev->checkpointCurrentBlock < 0){
	yaffs_CheckpointFindNextErasedBlock(dev);
	dev->checkpointCurrentChunk = 0;
	}

	if(dev->checkpointCurrentBlock < 0)
	return 0;

	tags.chunkDeleted = 0;
	tags.objectId = dev->checkpointNextBlock; /* Hint to next place to look */
	tags.chunkId = dev->checkpointPageSequence + 1;
	tags.sequenceNumber = YAFFS_SEQUENCE_CHECKPOINT_DATA;
	tags.byteCount = dev->nDataBytesPerChunk;
	if(dev->checkpointCurrentChunk == 0){
	/* First chunk we write for the block? Set block state to
	checkpoint */
	yaffs_BlockInfo *bi = yaffs_GetBlockInfo(dev,dev->checkpointCurrentBlock);
	bi->blockState = YAFFS_BLOCK_STATE_CHECKPOINT;
	dev->blocksInCheckpoint++;
	}

	chunk = dev->checkpointCurrentBlock * dev->nChunksPerBlock + dev->checkpointCurrentChunk;


	T(YAFFS_TRACE_CHECKPOINT,(TSTR("checkpoint wite buffer nand %d(%d:%d) objid %d chId %d" TENDSTR),
	chunk, dev->checkpointCurrentBlock, dev->checkpointCurrentChunk,tags.objectId,tags.chunkId));

	realignedChunk = chunk - dev->chunkOffset;

	dev->writeChunkWithTagsToNAND(dev,realignedChunk,dev->checkpointBuffer,&tags);
	dev->checkpointByteOffset = 0;
	dev->checkpointPageSequence++;
	dev->checkpointCurrentChunk++;
	if(dev->checkpointCurrentChunk >= dev->nChunksPerBlock){
	dev->checkpointCurrentChunk = 0;
	dev->checkpointCurrentBlock = -1;
	}
	memset(dev->checkpointBuffer,0,dev->nDataBytesPerChunk);

	return 1;
	}


	int yaffs_CheckpointWrite(yaffs_Device dev,const void data, int nBytes)
	{
	int i=0;
	int ok = 1;


	__u8 * dataBytes = (__u8 *)data;



	if(!dev->checkpointBuffer)
	return 0;

	if(!dev->checkpointOpenForWrite)
	return -1;

	while(i < nBytes && ok) {



	dev->checkpointBuffer[dev->checkpointByteOffset] = *dataBytes ;
	dev->checkpointSum += *dataBytes;
	dev->checkpointXor ^= *dataBytes;

	dev->checkpointByteOffset++;
	i++;
	dataBytes++;
	dev->checkpointByteCount++;


	if(dev->checkpointByteOffset < 0 \|\|
	dev->checkpointByteOffset >= dev->nDataBytesPerChunk)
	ok = yaffs_CheckpointFlushBuffer(dev);

	}

	return i;
	}

	int yaffs_CheckpointRead(yaffs_Device dev, void data, int nBytes)
	{
	int i=0;
	int ok = 1;
	yaffs_ExtendedTags tags;


	int chunk;
	int realignedChunk;

	__u8 dataBytes = (__u8 )data;

	if(!dev->checkpointBuffer)
	return 0;

	if(dev->checkpointOpenForWrite)
	return -1;

	while(i < nBytes && ok) {


	if(dev->checkpointByteOffset < 0 \|\|
	dev->checkpointByteOffset >= dev->nDataBytesPerChunk) {

	if(dev->checkpointCurrentBlock < 0){
	yaffs_CheckpointFindNextCheckpointBlock(dev);
	dev->checkpointCurrentChunk = 0;
	}

	if(dev->checkpointCurrentBlock < 0)
	ok = 0;
	else {

	chunk = dev->checkpointCurrentBlock * dev->nChunksPerBlock +
	dev->checkpointCurrentChunk;

	realignedChunk = chunk - dev->chunkOffset;

	/* read in the next chunk */
	/* printf("read checkpoint page %d\n",dev->checkpointPage); */
	dev->readChunkWithTagsFromNAND(dev, realignedChunk,
	dev->checkpointBuffer,
	&tags);

	if(tags.chunkId != (dev->checkpointPageSequence + 1) \|\|
	tags.sequenceNumber != YAFFS_SEQUENCE_CHECKPOINT_DATA)
	ok = 0;

	dev->checkpointByteOffset = 0;
	dev->checkpointPageSequence++;
	dev->checkpointCurrentChunk++;

	if(dev->checkpointCurrentChunk >= dev->nChunksPerBlock)
	dev->checkpointCurrentBlock = -1;
	}
	}

	if(ok){
	*dataBytes = dev->checkpointBuffer[dev->checkpointByteOffset];
	dev->checkpointSum += *dataBytes;
	dev->checkpointXor ^= *dataBytes;
	dev->checkpointByteOffset++;
	i++;
	dataBytes++;
	dev->checkpointByteCount++;
	}
	}

	return i;
	}

	int yaffs_CheckpointClose(yaffs_Device *dev)
	{

	if(dev->checkpointOpenForWrite){
	if(dev->checkpointByteOffset != 0)
	yaffs_CheckpointFlushBuffer(dev);
	} else {
	int i;
	for(i = 0; i < dev->blocksInCheckpoint && dev->checkpointBlockList[i] >= 0; i++){
	yaffs_BlockInfo *bi = yaffs_GetBlockInfo(dev,dev->checkpointBlockList[i]);
	if(bi->blockState == YAFFS_BLOCK_STATE_EMPTY)
	bi->blockState = YAFFS_BLOCK_STATE_CHECKPOINT;
	else {
	// Todo this looks odd...
	}
	}
	YFREE(dev->checkpointBlockList);
	dev->checkpointBlockList = NULL;
	}

	dev->nFreeChunks -= dev->blocksInCheckpoint * dev->nChunksPerBlock;
	dev->nErasedBlocks -= dev->blocksInCheckpoint;


	T(YAFFS_TRACE_CHECKPOINT,(TSTR("checkpoint byte count %d" TENDSTR),
	dev->checkpointByteCount));

	if(dev->checkpointBuffer){
	/* free the buffer */
	YFREE(dev->checkpointBuffer);
	dev->checkpointBuffer = NULL;
	return 1;
	}
	else
	return 0;

	}

	int yaffs_CheckpointInvalidateStream(yaffs_Device *dev)
	{
	/* Erase the first checksum block */

	T(YAFFS_TRACE_CHECKPOINT,(TSTR("checkpoint invalidate"TENDSTR)));

	if(!yaffs_CheckpointSpaceOk(dev))
	return 0;

	return yaffs_CheckpointErase(dev);
	}