fs/yaffs2/yaffs_mtdif1.c - kernel/common.git - Git at Google

 /*
  * YAFFS: Yet another FFS. A NAND-flash specific file system.
  *
  * Copyright (C) 2002-2010 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.
  */

 /*
  * This module provides the interface between yaffs_nand.c and the
  * MTD API.  This version is used when the MTD interface supports the
  * 'mtd_oob_ops' style calls to read_oob and write_oob, circa 2.6.17,
  * and we have small-page NAND device.
  *
  * These functions are invoked via function pointers in yaffs_nand.c.
  * This replaces functionality provided by functions in yaffs_mtdif.c
  * and the yaffs_tags compatability functions in yaffs_tagscompat.c that are
  * called in yaffs_mtdif.c when the function pointers are NULL.
  * We assume the MTD layer is performing ECC (use_nand_ecc is true).
  */

 #include "yportenv.h"
 #include "yaffs_trace.h"
 #include "yaffs_guts.h"
 #include "yaffs_packedtags1.h"
 #include "yaffs_tagscompat.h"	/* for yaffs_calc_tags_ecc */
 #include "yaffs_linux.h"

 #include "linux/kernel.h"
 #include "linux/version.h"
 #include "linux/types.h"
 #include "linux/mtd/mtd.h"

 #ifndef CONFIG_YAFFS_9BYTE_TAGS
 # define YTAG1_SIZE 8
 #else
 # define YTAG1_SIZE 9
 #endif

 /* Write a chunk (page) of data to NAND.
  *
  * Caller always provides ExtendedTags data which are converted to a more
  * compact (packed) form for storage in NAND.  A mini-ECC runs over the
  * contents of the tags meta-data; used to valid the tags when read.
  *
  *  - Pack ExtendedTags to packed_tags1 form
  *  - Compute mini-ECC for packed_tags1
  *  - Write data and packed tags to NAND.
  *
  * Note: Due to the use of the packed_tags1 meta-data which does not include
  * a full sequence number (as found in the larger packed_tags2 form) it is
  * necessary for Yaffs to re-write a chunk/page (just once) to mark it as
  * discarded and dirty.  This is not ideal: newer NAND parts are supposed
  * to be written just once.  When Yaffs performs this operation, this
  * function is called with a NULL data pointer -- calling MTD write_oob
  * without data is valid usage (2.6.17).
  *
  * Any underlying MTD error results in YAFFS_FAIL.
  * Returns YAFFS_OK or YAFFS_FAIL.
  */
 int nandmtd1_write_chunk_tags(struct yaffs_dev *dev,
 			      int nand_chunk, const u8 * data,
 			      const struct yaffs_ext_tags *etags)
 {
 	struct mtd_info *mtd = yaffs_dev_to_mtd(dev);
 	int chunk_bytes = dev->data_bytes_per_chunk;
 	loff_t addr = ((loff_t) nand_chunk) * chunk_bytes;
 	struct mtd_oob_ops ops;
 	struct yaffs_packed_tags1 pt1;
 	int retval;

 	/* we assume that packed_tags1 and struct yaffs_tags are compatible */
 	compile_time_assertion(sizeof(struct yaffs_packed_tags1) == 12);
 	compile_time_assertion(sizeof(struct yaffs_tags) == 8);

 	yaffs_pack_tags1(&pt1, etags);
 	yaffs_calc_tags_ecc((struct yaffs_tags *)&pt1);

 	/* When deleting a chunk, the upper layer provides only skeletal
 	 * etags, one with is_deleted set.  However, we need to update the
 	 * tags, not erase them completely.  So we use the NAND write property
 	 * that only zeroed-bits stick and set tag bytes to all-ones and
 	 * zero just the (not) deleted bit.
 	 */
 #ifndef CONFIG_YAFFS_9BYTE_TAGS
 	if (etags->is_deleted) {
 		memset(&pt1, 0xff, 8);
 		/* clear delete status bit to indicate deleted */
 		pt1.deleted = 0;
 	}
 #else
 	((u8 *) & pt1)[8] = 0xff;
 	if (etags->is_deleted) {
 		memset(&pt1, 0xff, 8);
 		/* zero page_status byte to indicate deleted */
 		((u8 *) & pt1)[8] = 0;
 	}
 #endif

 	memset(&ops, 0, sizeof(ops));
 	ops.mode = MTD_OOB_AUTO;
 	ops.len = (data) ? chunk_bytes : 0;
 	ops.ooblen = YTAG1_SIZE;
 	ops.datbuf = (u8 *) data;
 	ops.oobbuf = (u8 *) & pt1;

 	retval = mtd->write_oob(mtd, addr, &ops);
 	if (retval) {
 		yaffs_trace(YAFFS_TRACE_MTD,
 			"write_oob failed, chunk %d, mtd error %d",
 			nand_chunk, retval);
 	}
 	return retval ? YAFFS_FAIL : YAFFS_OK;
 }

 /* Return with empty ExtendedTags but add ecc_result.
  */
 static int rettags(struct yaffs_ext_tags *etags, int ecc_result, int retval)
 {
 	if (etags) {
 		memset(etags, 0, sizeof(*etags));
 		etags->ecc_result = ecc_result;
 	}
 	return retval;
 }

 /* Read a chunk (page) from NAND.
  *
  * Caller expects ExtendedTags data to be usable even on error; that is,
  * all members except ecc_result and block_bad are zeroed.
  *
  *  - Check ECC results for data (if applicable)
  *  - Check for blank/erased block (return empty ExtendedTags if blank)
  *  - Check the packed_tags1 mini-ECC (correct if necessary/possible)
  *  - Convert packed_tags1 to ExtendedTags
  *  - Update ecc_result and block_bad members to refect state.
  *
  * Returns YAFFS_OK or YAFFS_FAIL.
  */
 int nandmtd1_read_chunk_tags(struct yaffs_dev *dev,
 			     int nand_chunk, u8 * data,
 			     struct yaffs_ext_tags *etags)
 {
 	struct mtd_info *mtd = yaffs_dev_to_mtd(dev);
 	int chunk_bytes = dev->data_bytes_per_chunk;
 	loff_t addr = ((loff_t) nand_chunk) * chunk_bytes;
 	int eccres = YAFFS_ECC_RESULT_NO_ERROR;
 	struct mtd_oob_ops ops;
 	struct yaffs_packed_tags1 pt1;
 	int retval;
 	int deleted;

 	memset(&ops, 0, sizeof(ops));
 	ops.mode = MTD_OOB_AUTO;
 	ops.len = (data) ? chunk_bytes : 0;
 	ops.ooblen = YTAG1_SIZE;
 	ops.datbuf = data;
 	ops.oobbuf = (u8 *) & pt1;

 	/* Read page and oob using MTD.
 	 * Check status and determine ECC result.
 	 */
 	retval = mtd->read_oob(mtd, addr, &ops);
 	if (retval) {
 		yaffs_trace(YAFFS_TRACE_MTD,
 			"read_oob failed, chunk %d, mtd error %d",
 			nand_chunk, retval);
 	}

 	switch (retval) {
 	case 0:
 		/* no error */
 		break;

 	case -EUCLEAN:
 		/* MTD's ECC fixed the data */
 		eccres = YAFFS_ECC_RESULT_FIXED;
 		dev->n_ecc_fixed++;
 		break;

 	case -EBADMSG:
 		/* MTD's ECC could not fix the data */
 		dev->n_ecc_unfixed++;
 		/* fall into... */
 	default:
 		rettags(etags, YAFFS_ECC_RESULT_UNFIXED, 0);
 		etags->block_bad = (mtd->block_isbad) (mtd, addr);
 		return YAFFS_FAIL;
 	}

 	/* Check for a blank/erased chunk.
 	 */
 	if (yaffs_check_ff((u8 *) & pt1, 8)) {
 		/* when blank, upper layers want ecc_result to be <= NO_ERROR */
 		return rettags(etags, YAFFS_ECC_RESULT_NO_ERROR, YAFFS_OK);
 	}
 #ifndef CONFIG_YAFFS_9BYTE_TAGS
 	/* Read deleted status (bit) then return it to it's non-deleted
 	 * state before performing tags mini-ECC check. pt1.deleted is
 	 * inverted.
 	 */
 	deleted = !pt1.deleted;
 	pt1.deleted = 1;
 #else
 	deleted = (yaffs_count_bits(((u8 *) & pt1)[8]) < 7);
 #endif

 	/* Check the packed tags mini-ECC and correct if necessary/possible.
 	 */
 	retval = yaffs_check_tags_ecc((struct yaffs_tags *)&pt1);
 	switch (retval) {
 	case 0:
 		/* no tags error, use MTD result */
 		break;
 	case 1:
 		/* recovered tags-ECC error */
 		dev->n_tags_ecc_fixed++;
 		if (eccres == YAFFS_ECC_RESULT_NO_ERROR)
 			eccres = YAFFS_ECC_RESULT_FIXED;
 		break;
 	default:
 		/* unrecovered tags-ECC error */
 		dev->n_tags_ecc_unfixed++;
 		return rettags(etags, YAFFS_ECC_RESULT_UNFIXED, YAFFS_FAIL);
 	}

 	/* Unpack the tags to extended form and set ECC result.
 	 * [set should_be_ff just to keep yaffs_unpack_tags1 happy]
 	 */
 	pt1.should_be_ff = 0xFFFFFFFF;
 	yaffs_unpack_tags1(etags, &pt1);
 	etags->ecc_result = eccres;

 	/* Set deleted state */
 	etags->is_deleted = deleted;
 	return YAFFS_OK;
 }

 /* Mark a block bad.
  *
  * This is a persistant state.
  * Use of this function should be rare.
  *
  * Returns YAFFS_OK or YAFFS_FAIL.
  */
 int nandmtd1_mark_block_bad(struct yaffs_dev *dev, int block_no)
 {
 	struct mtd_info *mtd = yaffs_dev_to_mtd(dev);
 	int blocksize = dev->param.chunks_per_block * dev->data_bytes_per_chunk;
 	int retval;

 	yaffs_trace(YAFFS_TRACE_BAD_BLOCKS,
 		"marking block %d bad", block_no);

 	retval = mtd->block_markbad(mtd, (loff_t) blocksize * block_no);
 	return (retval) ? YAFFS_FAIL : YAFFS_OK;
 }

 /* Check any MTD prerequists.
  *
  * Returns YAFFS_OK or YAFFS_FAIL.
  */
 static int nandmtd1_test_prerequists(struct mtd_info *mtd)
 {
 	/* 2.6.18 has mtd->ecclayout->oobavail */
 	/* 2.6.21 has mtd->ecclayout->oobavail and mtd->oobavail */
 	int oobavail = mtd->ecclayout->oobavail;

 	if (oobavail < YTAG1_SIZE) {
 		yaffs_trace(YAFFS_TRACE_ERROR,
 			"mtd device has only %d bytes for tags, need %d",
 			oobavail, YTAG1_SIZE);
 		return YAFFS_FAIL;
 	}
 	return YAFFS_OK;
 }

 /* Query for the current state of a specific block.
  *
  * Examine the tags of the first chunk of the block and return the state:
  *  - YAFFS_BLOCK_STATE_DEAD, the block is marked bad
  *  - YAFFS_BLOCK_STATE_NEEDS_SCANNING, the block is in use
  *  - YAFFS_BLOCK_STATE_EMPTY, the block is clean
  *
  * Always returns YAFFS_OK.
  */
 int nandmtd1_query_block(struct yaffs_dev *dev, int block_no,
 			 enum yaffs_block_state *state_ptr, u32 * seq_ptr)
 {
 	struct mtd_info *mtd = yaffs_dev_to_mtd(dev);
 	int chunk_num = block_no * dev->param.chunks_per_block;
 	loff_t addr = (loff_t) chunk_num * dev->data_bytes_per_chunk;
 	struct yaffs_ext_tags etags;
 	int state = YAFFS_BLOCK_STATE_DEAD;
 	int seqnum = 0;
 	int retval;

 	/* We don't yet have a good place to test for MTD config prerequists.
 	 * Do it here as we are called during the initial scan.
 	 */
 	if (nandmtd1_test_prerequists(mtd) != YAFFS_OK)
 		return YAFFS_FAIL;

 	retval = nandmtd1_read_chunk_tags(dev, chunk_num, NULL, &etags);
 	etags.block_bad = (mtd->block_isbad) (mtd, addr);
 	if (etags.block_bad) {
 		yaffs_trace(YAFFS_TRACE_BAD_BLOCKS,
 			"block %d is marked bad", block_no);
 		state = YAFFS_BLOCK_STATE_DEAD;
 	} else if (etags.ecc_result != YAFFS_ECC_RESULT_NO_ERROR) {
 		/* bad tags, need to look more closely */
 		state = YAFFS_BLOCK_STATE_NEEDS_SCANNING;
 	} else if (etags.chunk_used) {
 		state = YAFFS_BLOCK_STATE_NEEDS_SCANNING;
 		seqnum = etags.seq_number;
 	} else {
 		state = YAFFS_BLOCK_STATE_EMPTY;
 	}

 	*state_ptr = state;
 	*seq_ptr = seqnum;

 	/* query always succeeds */
 	return YAFFS_OK;
 }
	/*
	* YAFFS: Yet another FFS. A NAND-flash specific file system.
	*
	* Copyright (C) 2002-2010 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.
	*/

	/*
	* This module provides the interface between yaffs_nand.c and the
	* MTD API. This version is used when the MTD interface supports the
	* 'mtd_oob_ops' style calls to read_oob and write_oob, circa 2.6.17,
	* and we have small-page NAND device.
	*
	* These functions are invoked via function pointers in yaffs_nand.c.
	* This replaces functionality provided by functions in yaffs_mtdif.c
	* and the yaffs_tags compatability functions in yaffs_tagscompat.c that are
	* called in yaffs_mtdif.c when the function pointers are NULL.
	* We assume the MTD layer is performing ECC (use_nand_ecc is true).
	*/

	#include "yportenv.h"
	#include "yaffs_trace.h"
	#include "yaffs_guts.h"
	#include "yaffs_packedtags1.h"
	#include "yaffs_tagscompat.h" /* for yaffs_calc_tags_ecc */
	#include "yaffs_linux.h"

	#include "linux/kernel.h"
	#include "linux/version.h"
	#include "linux/types.h"
	#include "linux/mtd/mtd.h"

	#ifndef CONFIG_YAFFS_9BYTE_TAGS
	# define YTAG1_SIZE 8
	#else
	# define YTAG1_SIZE 9
	#endif

	/* Write a chunk (page) of data to NAND.
	*
	* Caller always provides ExtendedTags data which are converted to a more
	* compact (packed) form for storage in NAND. A mini-ECC runs over the
	* contents of the tags meta-data; used to valid the tags when read.
	*
	* - Pack ExtendedTags to packed_tags1 form
	* - Compute mini-ECC for packed_tags1
	* - Write data and packed tags to NAND.
	*
	* Note: Due to the use of the packed_tags1 meta-data which does not include
	* a full sequence number (as found in the larger packed_tags2 form) it is
	* necessary for Yaffs to re-write a chunk/page (just once) to mark it as
	* discarded and dirty. This is not ideal: newer NAND parts are supposed
	* to be written just once. When Yaffs performs this operation, this
	* function is called with a NULL data pointer -- calling MTD write_oob
	* without data is valid usage (2.6.17).
	*
	* Any underlying MTD error results in YAFFS_FAIL.
	* Returns YAFFS_OK or YAFFS_FAIL.
	*/
	int nandmtd1_write_chunk_tags(struct yaffs_dev *dev,
	int nand_chunk, const u8 * data,
	const struct yaffs_ext_tags *etags)
	{
	struct mtd_info *mtd = yaffs_dev_to_mtd(dev);
	int chunk_bytes = dev->data_bytes_per_chunk;
	loff_t addr = ((loff_t) nand_chunk) * chunk_bytes;
	struct mtd_oob_ops ops;
	struct yaffs_packed_tags1 pt1;
	int retval;

	/* we assume that packed_tags1 and struct yaffs_tags are compatible */
	compile_time_assertion(sizeof(struct yaffs_packed_tags1) == 12);
	compile_time_assertion(sizeof(struct yaffs_tags) == 8);

	yaffs_pack_tags1(&pt1, etags);
	yaffs_calc_tags_ecc((struct yaffs_tags *)&pt1);

	/* When deleting a chunk, the upper layer provides only skeletal
	* etags, one with is_deleted set. However, we need to update the
	* tags, not erase them completely. So we use the NAND write property
	* that only zeroed-bits stick and set tag bytes to all-ones and
	* zero just the (not) deleted bit.
	*/
	#ifndef CONFIG_YAFFS_9BYTE_TAGS
	if (etags->is_deleted) {
	memset(&pt1, 0xff, 8);
	/* clear delete status bit to indicate deleted */
	pt1.deleted = 0;
	}
	#else
	((u8 *) & pt1)[8] = 0xff;
	if (etags->is_deleted) {
	memset(&pt1, 0xff, 8);
	/* zero page_status byte to indicate deleted */
	((u8 *) & pt1)[8] = 0;
	}
	#endif

	memset(&ops, 0, sizeof(ops));
	ops.mode = MTD_OOB_AUTO;
	ops.len = (data) ? chunk_bytes : 0;
	ops.ooblen = YTAG1_SIZE;
	ops.datbuf = (u8 *) data;
	ops.oobbuf = (u8 *) & pt1;

	retval = mtd->write_oob(mtd, addr, &ops);
	if (retval) {
	yaffs_trace(YAFFS_TRACE_MTD,
	"write_oob failed, chunk %d, mtd error %d",
	nand_chunk, retval);
	}
	return retval ? YAFFS_FAIL : YAFFS_OK;
	}

	/* Return with empty ExtendedTags but add ecc_result.
	*/
	static int rettags(struct yaffs_ext_tags *etags, int ecc_result, int retval)
	{
	if (etags) {
	memset(etags, 0, sizeof(*etags));
	etags->ecc_result = ecc_result;
	}
	return retval;
	}

	/* Read a chunk (page) from NAND.
	*
	* Caller expects ExtendedTags data to be usable even on error; that is,
	* all members except ecc_result and block_bad are zeroed.
	*
	* - Check ECC results for data (if applicable)
	* - Check for blank/erased block (return empty ExtendedTags if blank)
	* - Check the packed_tags1 mini-ECC (correct if necessary/possible)
	* - Convert packed_tags1 to ExtendedTags
	* - Update ecc_result and block_bad members to refect state.
	*
	* Returns YAFFS_OK or YAFFS_FAIL.
	*/
	int nandmtd1_read_chunk_tags(struct yaffs_dev *dev,
	int nand_chunk, u8 * data,
	struct yaffs_ext_tags *etags)
	{
	struct mtd_info *mtd = yaffs_dev_to_mtd(dev);
	int chunk_bytes = dev->data_bytes_per_chunk;
	loff_t addr = ((loff_t) nand_chunk) * chunk_bytes;
	int eccres = YAFFS_ECC_RESULT_NO_ERROR;
	struct mtd_oob_ops ops;
	struct yaffs_packed_tags1 pt1;
	int retval;
	int deleted;

	memset(&ops, 0, sizeof(ops));
	ops.mode = MTD_OOB_AUTO;
	ops.len = (data) ? chunk_bytes : 0;
	ops.ooblen = YTAG1_SIZE;
	ops.datbuf = data;
	ops.oobbuf = (u8 *) & pt1;

	/* Read page and oob using MTD.
	* Check status and determine ECC result.
	*/
	retval = mtd->read_oob(mtd, addr, &ops);
	if (retval) {
	yaffs_trace(YAFFS_TRACE_MTD,
	"read_oob failed, chunk %d, mtd error %d",
	nand_chunk, retval);
	}

	switch (retval) {
	case 0:
	/* no error */
	break;

	case -EUCLEAN:
	/* MTD's ECC fixed the data */
	eccres = YAFFS_ECC_RESULT_FIXED;
	dev->n_ecc_fixed++;
	break;

	case -EBADMSG:
	/* MTD's ECC could not fix the data */
	dev->n_ecc_unfixed++;
	/* fall into... */
	default:
	rettags(etags, YAFFS_ECC_RESULT_UNFIXED, 0);
	etags->block_bad = (mtd->block_isbad) (mtd, addr);
	return YAFFS_FAIL;
	}

	/* Check for a blank/erased chunk.
	*/
	if (yaffs_check_ff((u8 *) & pt1, 8)) {
	/* when blank, upper layers want ecc_result to be <= NO_ERROR */
	return rettags(etags, YAFFS_ECC_RESULT_NO_ERROR, YAFFS_OK);
	}
	#ifndef CONFIG_YAFFS_9BYTE_TAGS
	/* Read deleted status (bit) then return it to it's non-deleted
	* state before performing tags mini-ECC check. pt1.deleted is
	* inverted.
	*/
	deleted = !pt1.deleted;
	pt1.deleted = 1;
	#else
	deleted = (yaffs_count_bits(((u8 *) & pt1)[8]) < 7);
	#endif

	/* Check the packed tags mini-ECC and correct if necessary/possible.
	*/
	retval = yaffs_check_tags_ecc((struct yaffs_tags *)&pt1);
	switch (retval) {
	case 0:
	/* no tags error, use MTD result */
	break;
	case 1:
	/* recovered tags-ECC error */
	dev->n_tags_ecc_fixed++;
	if (eccres == YAFFS_ECC_RESULT_NO_ERROR)
	eccres = YAFFS_ECC_RESULT_FIXED;
	break;
	default:
	/* unrecovered tags-ECC error */
	dev->n_tags_ecc_unfixed++;
	return rettags(etags, YAFFS_ECC_RESULT_UNFIXED, YAFFS_FAIL);
	}

	/* Unpack the tags to extended form and set ECC result.
	* [set should_be_ff just to keep yaffs_unpack_tags1 happy]
	*/
	pt1.should_be_ff = 0xFFFFFFFF;
	yaffs_unpack_tags1(etags, &pt1);
	etags->ecc_result = eccres;

	/* Set deleted state */
	etags->is_deleted = deleted;
	return YAFFS_OK;
	}

	/* Mark a block bad.
	*
	* This is a persistant state.
	* Use of this function should be rare.
	*
	* Returns YAFFS_OK or YAFFS_FAIL.
	*/
	int nandmtd1_mark_block_bad(struct yaffs_dev *dev, int block_no)
	{
	struct mtd_info *mtd = yaffs_dev_to_mtd(dev);
	int blocksize = dev->param.chunks_per_block * dev->data_bytes_per_chunk;
	int retval;

	yaffs_trace(YAFFS_TRACE_BAD_BLOCKS,
	"marking block %d bad", block_no);

	retval = mtd->block_markbad(mtd, (loff_t) blocksize * block_no);
	return (retval) ? YAFFS_FAIL : YAFFS_OK;
	}

	/* Check any MTD prerequists.
	*
	* Returns YAFFS_OK or YAFFS_FAIL.
	*/
	static int nandmtd1_test_prerequists(struct mtd_info *mtd)
	{
	/* 2.6.18 has mtd->ecclayout->oobavail */
	/* 2.6.21 has mtd->ecclayout->oobavail and mtd->oobavail */
	int oobavail = mtd->ecclayout->oobavail;

	if (oobavail < YTAG1_SIZE) {
	yaffs_trace(YAFFS_TRACE_ERROR,
	"mtd device has only %d bytes for tags, need %d",
	oobavail, YTAG1_SIZE);
	return YAFFS_FAIL;
	}
	return YAFFS_OK;
	}

	/* Query for the current state of a specific block.
	*
	* Examine the tags of the first chunk of the block and return the state:
	* - YAFFS_BLOCK_STATE_DEAD, the block is marked bad
	* - YAFFS_BLOCK_STATE_NEEDS_SCANNING, the block is in use
	* - YAFFS_BLOCK_STATE_EMPTY, the block is clean
	*
	* Always returns YAFFS_OK.
	*/
	int nandmtd1_query_block(struct yaffs_dev *dev, int block_no,
	enum yaffs_block_state state_ptr, u32 seq_ptr)
	{
	struct mtd_info *mtd = yaffs_dev_to_mtd(dev);
	int chunk_num = block_no * dev->param.chunks_per_block;
	loff_t addr = (loff_t) chunk_num * dev->data_bytes_per_chunk;
	struct yaffs_ext_tags etags;
	int state = YAFFS_BLOCK_STATE_DEAD;
	int seqnum = 0;
	int retval;

	/* We don't yet have a good place to test for MTD config prerequists.
	* Do it here as we are called during the initial scan.
	*/
	if (nandmtd1_test_prerequists(mtd) != YAFFS_OK)
	return YAFFS_FAIL;

	retval = nandmtd1_read_chunk_tags(dev, chunk_num, NULL, &etags);
	etags.block_bad = (mtd->block_isbad) (mtd, addr);
	if (etags.block_bad) {
	yaffs_trace(YAFFS_TRACE_BAD_BLOCKS,
	"block %d is marked bad", block_no);
	state = YAFFS_BLOCK_STATE_DEAD;
	} else if (etags.ecc_result != YAFFS_ECC_RESULT_NO_ERROR) {
	/* bad tags, need to look more closely */
	state = YAFFS_BLOCK_STATE_NEEDS_SCANNING;
	} else if (etags.chunk_used) {
	state = YAFFS_BLOCK_STATE_NEEDS_SCANNING;
	seqnum = etags.seq_number;
	} else {
	state = YAFFS_BLOCK_STATE_EMPTY;
	}

	*state_ptr = state;
	*seq_ptr = seqnum;

	/* query always succeeds */
	return YAFFS_OK;
	}