text: // SPDX-License-Identifier: GPL-2.0-only
  /*
   *  Overview:
   *   Bad block table support for the NAND driver
   *
   *  Copyright © 2004 Thomas Gleixner (tglx@linutronix.de)
   *
   * Description:
   *
   * When nand_scan_bbt is called, then it tries to find the bad block table
   * depending on the options in the BBT descriptor(s). If no flash based BBT
   * (NAND_BBT_USE_FLASH) is specified then the device is scanned for factory
   * marked good / bad blocks. This information is used to create a memory BBT.
   * Once a new bad block is discovered then the "factory" information is updated
   * on the device.
   * If a flash based BBT is specified then the function first tries to find the
   * BBT on flash. If a BBT is found then the contents are read and the memory
   * based BBT is created. If a mirrored BBT is selected then the mirror is
   * searched too and the versions are compared. If the mirror has a greater
   * version number, then the mirror BBT is used to build the memory based BBT.
   * If the tables are not versioned, then we "or" the bad block information.
   * If one of the BBTs is out of date or does not exist it is (re)created.
   * If no BBT exists at all then the device is scanned for factory marked
   * good / bad blocks and the bad block tables are created.
   *
   * For manufacturer created BBTs like the one found on M-SYS DOC devices
   * the BBT is searched and read but never created
   *
   * The auto generated bad block table is located in the last good blocks
   * of the device. The table is mirrored, so it can be updated eventually.
   * The table is marked in the OOB area with an ident pattern and a version
   * number which indicates which of both tables is more up to date. If the NAND
   * controller needs the complete OOB area for the ECC information then the
   * option NAND_BBT_NO_OOB should be used (along with NAND_BBT_USE_FLASH, of
   * course): it moves the ident pattern and the version byte into the data area
   * and the OOB area will remain untouched.
   *
   * The table uses 2 bits per block
   * 11b:		block is good
   * 00b:		block is factory marked bad
   * 01b, 10b:	block is marked bad due to wear
   *
   * The memory bad block table uses the following scheme:
   * 00b:		block is good
   * 01b:		block is marked bad due to wear
   * 10b:		block is reserved (to protect the bbt area)
   * 11b:		block is factory marked bad
   *
   * Multichip devices like DOC store the bad block info per floor.
   *
   * Following assumptions are made:
   * - bbts start at a page boundary, if autolocated on a block boundary
   * - the space necessary for a bbt in FLASH does not exceed a block boundary
   */
  
  #include <linux/slab.h>
  #include <linux/types.h>
  #include <linux/mtd/mtd.h>
  #include <linux/mtd/bbm.h>
  #include <linux/bitops.h>
  #include <linux/delay.h>
  #include <linux/vmalloc.h>
  #include <linux/export.h>
  #include <linux/string.h>
  
  #include "internals.h"
  
  #define BBT_BLOCK_GOOD		0x00
  #define BBT_BLOCK_WORN		0x01
  #define BBT_BLOCK_RESERVED	0x02
  #define BBT_BLOCK_FACTORY_BAD	0x03
  
  #define BBT_ENTRY_MASK		0x03
  #define BBT_ENTRY_SHIFT		2
  
  static inline uint8_t bbt_get_entry(struct nand_chip *chip, int block)
  {
  	uint8_t entry = chip->bbt[block >> BBT_ENTRY_SHIFT];
  	entry >>= (block & BBT_ENTRY_MASK) * 2;
  	return entry & BBT_ENTRY_MASK;
  }
  
  static inline void bbt_mark_entry(struct nand_chip *chip, int block,
  		uint8_t mark)
  {
  	uint8_t msk = (mark & BBT_ENTRY_MASK) << ((block & BBT_ENTRY_MASK) * 2);
  	chip->bbt[block >> BBT_ENTRY_SHIFT] |= msk;
  }
  
  static int check_pattern_no_oob(uint8_t *buf, struct nand_bbt_descr *td)
  {
  	if (memcmp(buf, td->pattern, td->len))
  		return -1;
  	return 0;
  }
  
  /**
   * check_pattern - [GENERIC] check if a pattern is in the buffer
   * @buf: the buffer to search
   * @len: the length of buffer to search
   * @paglen: the pagelength
   * @td: search pattern descriptor
   *
   * Check for a pattern at the given place. Used to search bad block tables and
   * good / bad block identifiers.
   */
  static int check_pattern(uint8_t *buf, int len, int paglen, struct nand_bbt_descr *td)
  {
  	if (td->options & NAND_BBT_NO_OOB)
  		return check_pattern_no_oob(buf, td);
  
  	/* Compare the pattern */
  	if (memcmp(buf + paglen + td->offs, td->pattern, td->len))
  		return -1;
  
  	return 0;
  }
  
  /**
   * check_short_pattern - [GENERIC] check if a pattern is in the buffer
   * @buf: the buffer to search
   * @td:	search pattern descriptor
   *
   * Check for a pattern at the given place. Used to search bad block tables and
   * good / bad block identifiers. Same as check_pattern, but no optional empty
   * check.
   */
  static int check_short_pattern(uint8_t *buf, struct nand_bbt_descr *td)
  {
  	/* Compare the pattern */
  	if (memcmp(buf + td->offs, td->pattern, td->len))
  		return -1;
  	return 0;
  }
  
  /**
   * add_marker_len - compute the length of the marker in data area
   * @td: BBT descriptor used for computation
   *
   * The length will be 0 if the marker is located in OOB area.
   */
  static u32 add_marker_len(struct nand_bbt_descr *td)
  {
  	u32 len;
  
  	if (!(td->options & NAND_BBT_NO_OOB))
  		return 0;
  
  	len = td->len;
  	if (td->options & NAND_BBT_VERSION)
  		len++;
  	return len;
  }
  
  /**
   * read_bbt - [GENERIC] Read the bad block table starting from page
   * @this: NAND chip object
   * @buf: temporary buffer
   * @page: the starting page
   * @num: the number of bbt descriptors to read
   * @td: the bbt describtion table
   * @offs: block number offset in the table
   *
   * Read the bad block table starting from page.
   */
  static int read_bbt(struct nand_chip *this, uint8_t *buf, int page, int num,
  		    struct nand_bbt_descr *td, int offs)
  {
  	struct mtd_info *mtd = nand_to_mtd(this);
  	int res, ret = 0, i, j, act = 0;
  	size_t retlen, len, totlen;
  	loff_t from;
  	int bits = td->options & NAND_BBT_NRBITS_MSK;
  	uint8_t msk = (uint8_t)((1 << bits) - 1);
  	u32 marker_len;
  	int reserved_block_code = td->reserved_block_code;
  
  	totlen = (num * bits) >> 3;
  	marker_len = add_marker_len(td);
  	from = ((loff_t)page) << this->page_shift;
  
  	while (totlen) {
  		len = min(totlen, (size_t)(1 << this->bbt_erase_shift));
  		if (marker_len) {
  			/*
  			 * In case the BBT marker is not in the OOB area it
  			 * will be just in the first page.
  			 */
  			len -= marker_len;
  			from += marker_len;
  			marker_len = 0;
  		}
  		res = mtd_read(mtd, from, len, &retlen, buf);
  		if (res < 0) {
  			if (mtd_is_eccerr(res)) {
  				pr_info("nand_bbt: ECC error in BBT at 0x%012llx\n",
  					from & ~mtd->writesize);
  				return res;
  			} else if (mtd_is_bitflip(res)) {
  				pr_info("nand_bbt: corrected error in BBT at 0x%012llx\n",
  					from & ~mtd->writesize);
  				ret = res;
  			} else {
  				pr_info("nand_bbt: error reading BBT\n");
  				return res;
  			}
  		}
  
  		/* Analyse data */
  		for (i = 0; i < len; i++) {
  			uint8_t dat = buf[i];
  			for (j = 0; j < 8; j += bits, act++) {
  				uint8_t tmp = (dat >> j) & msk;
  				if (tmp == msk)
  					continue;
  				if (reserved_block_code && (tmp == reserved_block_code)) {
  					pr_info("nand_read_bbt: reserved block at 0x%012llx\n",
  						 (loff_t)(offs + act) <<
  						 this->bbt_erase_shift);
  					bbt_mark_entry(this, offs + act,
  							BBT_BLOCK_RESERVED);
  					mtd->ecc_stats.bbtblocks++;
  					continue;
  				}
  				/*
  				 * Leave it for now, if it's matured we can
  				 * move this message to pr_debug.
  				 */
  				pr_info("nand_read_bbt: bad block at 0x%012llx\n",
  					 (loff_t)(offs + act) <<
  					 this->bbt_erase_shift);
  				/* Factory marked bad or worn out? */
  				if (tmp == 0)
  					bbt_mark_entry(this, offs + act,
  							BBT_BLOCK_FACTORY_BAD);
  				else
  					bbt_mark_entry(this, offs + act,
  							BBT_BLOCK_WORN);
  				mtd->ecc_stats.badblocks++;
  			}
  		}
  		totlen -= len;
  		from += len;
  	}
  	return ret;
  }
  
  /**
   * read_abs_bbt - [GENERIC] Read the bad block table starting at a given page
   * @this: NAND chip object
   * @buf: temporary buffer
   * @td: descriptor for the bad block table
   * @chip: read the table for a specific chip, -1 read all chips; applies only if
   *        NAND_BBT_PERCHIP option is set
   *
   * Read the bad block table for all chips starting at a given page. We assume
   * that the bbt bits are in consecutive order.
   */
  static int read_abs_bbt(struct nand_chip *this, uint8_t *buf,
  			struct nand_bbt_descr *td, int chip)
  {
  	struct mtd_info *mtd = nand_to_mtd(this);
  	u64 targetsize = nanddev_target_size(&this->base);
  	int res = 0, i;
  
  	if (td->options & NAND_BBT_PERCHIP) {
  		int offs = 0;
  		for (i = 0; i < nanddev_ntargets(&this->base); i++) {
  			if (chip == -1 || chip == i)
  				res = read_bbt(this, buf, td->pages[i],
  					targetsize >> this->bbt_erase_shift,
  					td, offs);
  			if (res)
  				return res;
  			offs += targetsize >> this->bbt_erase_shift;
  		}
  	} else {
  		res = read_bbt(this, buf, td->pages[0],
  				mtd->size >> this->bbt_erase_shift, td, 0);
  		if (res)
  			return res;
  	}
  	return 0;
  }
  
  /* BBT marker is in the first page, no OOB */
  static int scan_read_data(struct nand_chip *this, uint8_t *buf, loff_t offs,
  			  struct nand_bbt_descr *td)
  {
  	struct mtd_info *mtd = nand_to_mtd(this);
  	size_t retlen;
  	size_t len;
  
  	len = td->len;
  	if (td->options & NAND_BBT_VERSION)
  		len++;
  
  	return mtd_read(mtd, offs, len, &retlen, buf);
  }
  
  /**
   * scan_read_oob - [GENERIC] Scan data+OOB region to buffer
   * @this: NAND chip object
   * @buf: temporary buffer
   * @offs: offset at which to scan
   * @len: length of data region to read
   *
   * Scan read data from data+OOB. May traverse multiple pages, interleaving
   * page,OOB,page,OOB,... in buf. Completes transfer and returns the "strongest"
   * ECC condition (error or bitflip). May quit on the first (non-ECC) error.
   */
  static int scan_read_oob(struct nand_chip *this, uint8_t *buf, loff_t offs,
  			 size_t len)
  {
  	struct mtd_info *mtd = nand_to_mtd(this);
  	struct mtd_oob_ops ops;
  	int res, ret = 0;
  
  	ops.mode = MTD_OPS_PLACE_OOB;
  	ops.ooboffs = 0;
  	ops.ooblen = mtd->oobsize;
  
  	while (len > 0) {
  		ops.datbuf = buf;
  		ops.len = min(len, (size_t)mtd->writesize);
  		ops.oobbuf = buf + ops.len;
  
  		res = mtd_read_oob(mtd, offs, &ops);
  		if (res) {
  			if (!mtd_is_bitflip_or_eccerr(res))
  				return res;
  			else if (mtd_is_eccerr(res) || !ret)
  				ret = res;
  		}
  
  		buf += mtd->oobsize + mtd->writesize;
  		len -= mtd->writesize;
  		offs += mtd->writesize;
  	}
  	return ret;
  }
  
  static int scan_read(struct nand_chip *this, uint8_t *buf, loff_t offs,
  		     size_t len, struct nand_bbt_descr *td)
  {
  	if (td->options & NAND_BBT_NO_OOB)
  		return scan_read_data(this, buf, offs, td);
  	else
  		return scan_read_oob(this, buf, offs, len);
  }
  
  /* Scan write data with oob to flash */
  static int scan_write_bbt(struct nand_chip *this, loff_t offs, size_t len,
  			  uint8_t *buf, uint8_t *oob)
  {
  	struct mtd_info *mtd = nand_to_mtd(this);
  	struct mtd_oob_ops ops;
  
  	ops.mode = MTD_OPS_PLACE_OOB;
  	ops.ooboffs = 0;
  	ops.ooblen = mtd->oobsize;
  	ops.datbuf = buf;
  	ops.oobbuf = oob;
  	ops.len = len;
  
  	return mtd_write_oob(mtd, offs, &ops);
  }
  
  static u32 bbt_get_ver_offs(struct nand_chip *this, struct nand_bbt_descr *td)
  {
  	struct mtd_info *mtd = nand_to_mtd(this);
  	u32 ver_offs = td->veroffs;
  
  	if (!(td->options & NAND_BBT_NO_OOB))
  		ver_offs += mtd->writesize;
  	return ver_offs;
  }
  
  /**
   * read_abs_bbts - [GENERIC] Read the bad block table(s) for all chips starting at a given page
   * @this: NAND chip object
   * @buf: temporary buffer
   * @td: descriptor for the bad block table
   * @md:	descriptor for the bad block table mirror
   *
   * Read the bad block table(s) for all chips starting at a given page. We
   * assume that the bbt bits are in consecutive order.
   */
  static void read_abs_bbts(struct nand_chip *this, uint8_t *buf,
  			  struct nand_bbt_descr *td, struct nand_bbt_descr *md)
  {
  	struct mtd_info *mtd = nand_to_mtd(this);
  
  	/* Read the primary version, if available */
  	if (td->options & NAND_BBT_VERSION) {
  		scan_read(this, buf, (loff_t)td->pages[0] << this->page_shift,
  			  mtd->writesize, td);
  		td->version[0] = buf[bbt_get_ver_offs(this, td)];
  		pr_info("Bad block table at page %d, version 0x%02X\n",
  			 td->pages[0], td->version[0]);
  	}
  
  	/* Read the mirror version, if available */
  	if (md && (md->options & NAND_BBT_VERSION)) {
  		scan_read(this, buf, (loff_t)md->pages[0] << this->page_shift,
  			  mtd->writesize, md);
  		md->version[0] = buf[bbt_get_ver_offs(this, md)];
  		pr_info("Bad block table at page %d, version 0x%02X\n",
  			 md->pages[0], md->version[0]);
  	}
  }
  
  /* Scan a given block partially */
  static int scan_block_fast(struct nand_chip *this, struct nand_bbt_descr *bd,
  			   loff_t offs, uint8_t *buf)
  {
  	struct mtd_info *mtd = nand_to_mtd(this);
  
  	struct mtd_oob_ops ops;
  	int ret, page_offset;
  
  	ops.ooblen = mtd->oobsize;
  	ops.oobbuf = buf;
  	ops.ooboffs = 0;
  	ops.datbuf = NULL;
  	ops.mode = MTD_OPS_PLACE_OOB;
  
  	page_offset = nand_bbm_get_next_page(this, 0);
  
  	while (page_offset >= 0) {
  		/*
  		 * Read the full oob until read_oob is fixed to handle single
  		 * byte reads for 16 bit buswidth.
  		 */
  		ret = mtd_read_oob(mtd, offs + (page_offset * mtd->writesize),
  				   &ops);
  		/* Ignore ECC errors when checking for BBM */
  		if (ret && !mtd_is_bitflip_or_eccerr(ret))
  			return ret;
  
  		if (check_short_pattern(buf, bd))
  			return 1;
  
  		page_offset = nand_bbm_get_next_page(this, page_offset + 1);
  	}
  
  	return 0;
  }
  
  /* Check if a potential BBT block is marked as bad */
  static int bbt_block_checkbad(struct nand_chip *this, struct nand_bbt_descr *td,
  			      loff_t offs, uint8_t *buf)
  {
  	struct nand_bbt_descr *bd = this->badblock_pattern;
  
  	/*
  	 * No need to check for a bad BBT block if the BBM area overlaps with
  	 * the bad block table marker area in OOB since writing a BBM here
  	 * invalidates the bad block table marker anyway.
  	 */
  	if (!(td->options & NAND_BBT_NO_OOB) &&
  	    td->offs >= bd->offs && td->offs < bd->offs + bd->len)
  		return 0;
  
  	/*
  	 * There is no point in checking for a bad block marker if writing
  	 * such marker is not supported
  	 */
  	if (this->bbt_options & NAND_BBT_NO_OOB_BBM ||
  	    this->options & NAND_NO_BBM_QUIRK)
  		return 0;
  
  	if (scan_block_fast(this, bd, offs, buf) > 0)
  		return 1;
  
  	return 0;
  }
  
  /**
   * create_bbt - [GENERIC] Create a bad block table by scanning the device
   * @this: NAND chip object
   * @buf: temporary buffer
   * @bd: descriptor for the good/bad block search pattern
   * @chip: create the table for a specific chip, -1 read all chips; applies only
   *        if NAND_BBT_PERCHIP option is set
   *
   * Create a bad block table by scanning the device for the given good/bad block
   * identify pattern.
   */
  static int create_bbt(struct nand_chip *this, uint8_t *buf,
  		      struct nand_bbt_descr *bd, int chip)
  {
  	u64 targetsize = nanddev_target_size(&this->base);
  	struct mtd_info *mtd = nand_to_mtd(this);
  	int i, numblocks, startblock;
  	loff_t from;
  
  	pr_info("Scanning device for bad blocks\n");
  
  	if (chip == -1) {
  		numblocks = mtd->size >> this->bbt_erase_shift;
  		startblock = 0;
  		from = 0;
  	} else {
  		if (chip >= nanddev_ntargets(&this->base)) {
  			pr_warn("create_bbt(): chipnr (%d) > available chips (%d)\n",
  			        chip + 1, nanddev_ntargets(&this->base));
  			return -EINVAL;
  		}
  		numblocks = targetsize >> this->bbt_erase_shift;
  		startblock = chip * numblocks;
  		numblocks += startblock;
  		from = (loff_t)startblock << this->bbt_erase_shift;
  	}
  
  	for (i = startblock; i < numblocks; i++) {
  		int ret;
  
  		BUG_ON(bd->options & NAND_BBT_NO_OOB);
  
  		ret = scan_block_fast(this, bd, from, buf);
  		if (ret < 0)
  			return ret;
  
  		if (ret) {
  			bbt_mark_entry(this, i, BBT_BLOCK_FACTORY_BAD);
  			pr_warn("Bad eraseblock %d at 0x%012llx\n",
  				i, (unsigned long long)from);
  			mtd->ecc_stats.badblocks++;
  		}
  
  		from += (1 << this->bbt_erase_shift);
  	}
  	return 0;
  }
  
  /**
   * search_bbt - [GENERIC] scan the device for a specific bad block table
   * @this: NAND chip object
   * @buf: temporary buffer
   * @td: descriptor for the bad block table
   *
   * Read the bad block table by searching for a given ident pattern. Search is
   * preformed either from the beginning up or from the end of the device
   * downwards. The search starts always at the start of a block. If the option
   * NAND_BBT_PERCHIP is given, each chip is searched for a bbt, which contains
   * the bad block information of this chip. This is necessary to provide support
   * for certain DOC devices.
   *
   * The bbt ident pattern resides in the oob area of the first page in a block.
   */
  static int search_bbt(struct nand_chip *this, uint8_t *buf,
  		      struct nand_bbt_descr *td)
  {
  	u64 targetsize = nanddev_target_size(&this->base);
  	struct mtd_info *mtd = nand_to_mtd(this);
  	int i, chips;
  	int startblock, block, dir;
  	int scanlen = mtd->writesize + mtd->oobsize;
  	int bbtblocks;
  	int blocktopage = this->bbt_erase_shift - this->page_shift;
  
  	/* Search direction top -> down? */
  	if (td->options & NAND_BBT_LASTBLOCK) {
  		startblock = (mtd->size >> this->bbt_erase_shift) - 1;
  		dir = -1;
  	} else {
  		startblock = 0;
  		dir = 1;
  	}
  
  	/* Do we have a bbt per chip? */
  	if (td->options & NAND_BBT_PERCHIP) {
  		chips = nanddev_ntargets(&this->base);
  		bbtblocks = targetsize >> this->bbt_erase_shift;
  		startblock &= bbtblocks - 1;
  	} else {
  		chips = 1;
  		bbtblocks = mtd->size >> this->bbt_erase_shift;
  	}
  
  	for (i = 0; i < chips; i++) {
  		/* Reset version information */
  		td->version[i] = 0;
  		td->pages[i] = -1;
  		/* Scan the maximum number of blocks */
  		for (block = 0; block < td->maxblocks; block++) {
  
  			int actblock = startblock + dir * block;
  			loff_t offs = (loff_t)actblock << this->bbt_erase_shift;
  
  			/* Check if block is marked bad */
  			if (bbt_block_checkbad(this, td, offs, buf))
  				continue;
  
  			/* Read first page */
  			scan_read(this, buf, offs, mtd->writesize, td);
  			if (!check_pattern(buf, scanlen, mtd->writesize, td)) {
  				td->pages[i] = actblock << blocktopage;
  				if (td->options & NAND_BBT_VERSION) {
  					offs = bbt_get_ver_offs(this, td);
  					td->version[i] = buf[offs];
  				}
  				break;
  			}
  		}
  		startblock += targetsize >> this->bbt_erase_shift;
  	}
  	/* Check, if we found a bbt for each requested chip */
  	for (i = 0; i < chips; i++) {
  		if (td->pages[i] == -1)
  			pr_warn("Bad block table not found for chip %d\n", i);
  		else
  			pr_info("Bad block table found at page %d, version 0x%02X\n",
  				td->pages[i], td->version[i]);
  	}
  	return 0;
  }
  
  /**
   * search_read_bbts - [GENERIC] scan the device for bad block table(s)
   * @this: NAND chip object
   * @buf: temporary buffer
   * @td: descriptor for the bad block table
   * @md: descriptor for the bad block table mirror
   *
   * Search and read the bad block table(s).
   */
  static void search_read_bbts(struct nand_chip *this, uint8_t *buf,
  			     struct nand_bbt_descr *td,
  			     struct nand_bbt_descr *md)
  {
  	/* Search the primary table */
  	search_bbt(this, buf, td);
  
  	/* Search the mirror table */
  	if (md)
  		search_bbt(this, buf, md);
  }
  
  /**
   * get_bbt_block - Get the first valid eraseblock suitable to store a BBT
   * @this: the NAND device
   * @td: the BBT description
   * @md: the mirror BBT descriptor
   * @chip: the CHIP selector
   *
   * This functions returns a positive block number pointing a valid eraseblock
   * suitable to store a BBT (i.e. in the range reserved for BBT), or -ENOSPC if
   * all blocks are already used of marked bad. If td->pages[chip] was already
   * pointing to a valid block we re-use it, otherwise we search for the next
   * valid one.
   */
  static int get_bbt_block(struct nand_chip *this, struct nand_bbt_descr *td,
  			 struct nand_bbt_descr *md, int chip)
  {
  	u64 targetsize = nanddev_target_size(&this->base);
  	int startblock, dir, page, numblocks, i;
  
  	/*
  	 * There was already a version of the table, reuse the page. This
  	 * applies for absolute placement too, as we have the page number in
  	 * td->pages.
  	 */
  	if (td->pages[chip] != -1)
  		return td->pages[chip] >>
  				(this->bbt_erase_shift - this->page_shift);
  
  	numblocks = (int)(targetsize >> this->bbt_erase_shift);
  	if (!(td->options & NAND_BBT_PERCHIP))
  		numblocks *= nanddev_ntargets(&this->base);
  
  	/*
  	 * Automatic placement of the bad block table. Search direction
  	 * top -> down?
  	 */
  	if (td->options & NAND_BBT_LASTBLOCK) {
  		startblock = numblocks * (chip + 1) - 1;
  		dir = -1;
  	} else {
  		startblock = chip * numblocks;
  		dir = 1;
  	}
  
  	for (i = 0; i < td->maxblocks; i++) {
  		int block = startblock + dir * i;
  
  		/* Check, if the block is bad */
  		switch (bbt_get_entry(this, block)) {
  		case BBT_BLOCK_WORN:
  		case BBT_BLOCK_FACTORY_BAD:
  			continue;
  		}
  
  		page = block << (this->bbt_erase_shift - this->page_shift);
  
  		/* Check, if the block is used by the mirror table */
  		if (!md || md->pages[chip] != page)
  			return block;
  	}
  
  	return -ENOSPC;
  }
  
  /**
   * mark_bbt_block_bad - Mark one of the block reserved for BBT bad
   * @this: the NAND device
   * @td: the BBT description
   * @chip: the CHIP selector
   * @block: the BBT block to mark
   *
   * Blocks reserved for BBT can become bad. This functions is an helper to mark
   * such blocks as bad. It takes care of updating the in-memory BBT, marking the
   * block as bad using a bad block marker and invalidating the associated
   * td->pages[] entry.
   */
  static void mark_bbt_block_bad(struct nand_chip *this,
  			       struct nand_bbt_descr *td,
  			       int chip, int block)
  {
  	loff_t to;
  	int res;
  
  	bbt_mark_entry(this, block, BBT_BLOCK_WORN);
  
  	to = (loff_t)block << this->bbt_erase_shift;
  	res = nand_markbad_bbm(this, to);
  	if (res)
  		pr_warn("nand_bbt: error %d while marking block %d bad\n",
  			res, block);
  
  	td->pages[chip] = -1;
  }
  
  /**
   * write_bbt - [GENERIC] (Re)write the bad block table
   * @this: NAND chip object
   * @buf: temporary buffer
   * @td: descriptor for the bad block table
   * @md: descriptor for the bad block table mirror
   * @chipsel: selector for a specific chip, -1 for all
   *
   * (Re)write the bad block table.
   */
  static int write_bbt(struct nand_chip *this, uint8_t *buf,
  		     struct nand_bbt_descr *td, struct nand_bbt_descr *md,
  		     int chipsel)
  {
  	u64 targetsize = nanddev_target_size(&this->base);
  	struct mtd_info *mtd = nand_to_mtd(this);
  	struct erase_info einfo;
  	int i, res, chip = 0;
  	int bits, page, offs, numblocks, sft, sftmsk;
  	int nrchips, pageoffs, ooboffs;
  	uint8_t msk[4];
  	uint8_t rcode = td->reserved_block_code;
  	size_t retlen, len = 0;
  	loff_t to;
  	struct mtd_oob_ops ops;
  
  	ops.ooblen = mtd->oobsize;
  	ops.ooboffs = 0;
  	ops.datbuf = NULL;
  	ops.mode = MTD_OPS_PLACE_OOB;
  
  	if (!rcode)
  		rcode = 0xff;
  	/* Write bad block table per chip rather than per device? */
  	if (td->options & NAND_BBT_PERCHIP) {
  		numblocks = (int)(targetsize >> this->bbt_erase_shift);
  		/* Full device write or specific chip? */
  		if (chipsel == -1) {
  			nrchips = nanddev_ntargets(&this->base);
  		} else {
  			nrchips = chipsel + 1;
  			chip = chipsel;
  		}
  	} else {
  		numblocks = (int)(mtd->size >> this->bbt_erase_shift);
  		nrchips = 1;
  	}
  
  	/* Loop through the chips */
  	while (chip < nrchips) {
  		int block;
  
  		block = get_bbt_block(this, td, md, chip);
  		if (block < 0) {
  			pr_err("No space left to write bad block table\n");
  			res = block;
  			goto outerr;
  		}
  
  		/*
  		 * get_bbt_block() returns a block number, shift the value to
  		 * get a page number.
  		 */
  		page = block << (this->bbt_erase_shift - this->page_shift);
  
  		/* Set up shift count and masks for the flash table */
  		bits = td->options & NAND_BBT_NRBITS_MSK;
  		msk[2] = ~rcode;
  		switch (bits) {
  		case 1: sft = 3; sftmsk = 0x07; msk[0] = 0x00; msk[1] = 0x01;
  			msk[3] = 0x01;
  			break;
  		case 2: sft = 2; sftmsk = 0x06; msk[0] = 0x00; msk[1] = 0x01;
  			msk[3] = 0x03;
  			break;
  		case 4: sft = 1; sftmsk = 0x04; msk[0] = 0x00; msk[1] = 0x0C;
  			msk[3] = 0x0f;
  			break;
  		case 8: sft = 0; sftmsk = 0x00; msk[0] = 0x00; msk[1] = 0x0F;
  			msk[3] = 0xff;
  			break;
  		default: return -EINVAL;
  		}
  
  		to = ((loff_t)page) << this->page_shift;
  
  		/* Must we save the block contents? */
  		if (td->options & NAND_BBT_SAVECONTENT) {
  			/* Make it block aligned */
  			to &= ~(((loff_t)1 << this->bbt_erase_shift) - 1);
  			len = 1 << this->bbt_erase_shift;
  			res = mtd_read(mtd, to, len, &retlen, buf);
  			if (res < 0) {
  				if (retlen != len) {
  					pr_info("nand_bbt: error reading block for writing the bad block table\n");
  					return res;
  				}
  				pr_warn("nand_bbt: ECC error while reading block for writing bad block table\n");
  			}
  			/* Read oob data */
  			ops.ooblen = (len >> this->page_shift) * mtd->oobsize;
  			ops.oobbuf = &buf[len];
  			res = mtd_read_oob(mtd, to + mtd->writesize, &ops);
  			if (res < 0 || ops.oobretlen != ops.ooblen)
  				goto outerr;
  
  			/* Calc the byte offset in the buffer */
  			pageoffs = page - (int)(to >> this->page_shift);
  			offs = pageoffs << this->page_shift;
  			/* Preset the bbt area with 0xff */
  			memset(&buf[offs], 0xff, (size_t)(numblocks >> sft));
  			ooboffs = len + (pageoffs * mtd->oobsize);
  
  		} else if (td->options & NAND_BBT_NO_OOB) {
  			ooboffs = 0;
  			offs = td->len;
  			/* The version byte */
  			if (td->options & NAND_BBT_VERSION)
  				offs++;
  			/* Calc length */
  			len = (size_t)(numblocks >> sft);
  			len += offs;
  			/* Make it page aligned! */
  			len = ALIGN(len, mtd->writesize);
  			/* Preset the buffer with 0xff */
  			memset(buf, 0xff, len);
  			/* Pattern is located at the begin of first page */
  			memcpy(buf, td->pattern, td->len);
  		} else {
  			/* Calc length */
  			len = (size_t)(numblocks >> sft);
  			/* Make it page aligned! */
  			len = ALIGN(len, mtd->writesize);
  			/* Preset the buffer with 0xff */
  			memset(buf, 0xff, len +
  			       (len >> this->page_shift)* mtd->oobsize);
  			offs = 0;
  			ooboffs = len;
  			/* Pattern is located in oob area of first page */
  			memcpy(&buf[ooboffs + td->offs], td->pattern, td->len);
  		}
  
  		if (td->options & NAND_BBT_VERSION)
  			buf[ooboffs + td->veroffs] = td->version[chip];
  
  		/* Walk through the memory table */
  		for (i = 0; i < numblocks; i++) {
  			uint8_t dat;
  			int sftcnt = (i << (3 - sft)) & sftmsk;
  			dat = bbt_get_entry(this, chip * numblocks + i);
  			/* Do not store the reserved bbt blocks! */
  			buf[offs + (i >> sft)] &= ~(msk[dat] << sftcnt);
  		}
  
  		memset(&einfo, 0, sizeof(einfo));
  		einfo.addr = to;
  		einfo.len = 1 << this->bbt_erase_shift;
  		res = nand_erase_nand(this, &einfo, 1);
  		if (res < 0) {
  			pr_warn("nand_bbt: error while erasing BBT block %d\n",
  				res);
  			mark_bbt_block_bad(this, td, chip, block);
  			continue;
  		}
  
  		res = scan_write_bbt(this, to, len, buf,
  				     td->options & NAND_BBT_NO_OOB ?
  				     NULL : &buf[len]);
  		if (res < 0) {
  			pr_warn("nand_bbt: error while writing BBT block %d\n",
  				res);
  			mark_bbt_block_bad(this, td, chip, block);
  			continue;
  		}
  
  		pr_info("Bad block table written to 0x%012llx, version 0x%02X\n",
  			 (unsigned long long)to, td->version[chip]);
  
  		/* Mark it as used */
  		td->pages[chip++] = page;
  	}
  	return 0;
  
   outerr:
  	pr_warn("nand_bbt: error while writing bad block table %d\n", res);
  	return res;
  }
  
  /**
   * nand_memory_bbt - [GENERIC] create a memory based bad block table
   * @this: NAND chip object
   * @bd: descriptor for the good/bad block search pattern
   *
   * The function creates a memory based bbt by scanning the device for
   * manufacturer / software marked good / bad blocks.
   */
  static inline int nand_memory_bbt(struct nand_chip *this,
  				  struct nand_bbt_descr *bd)
  {
  	u8 *pagebuf = nand_get_data_buf(this);
  
  	return create_bbt(this, pagebuf, bd, -1);
  }
  
  /**
   * check_create - [GENERIC] create and write bbt(s) if necessary
   * @this: the NAND device
   * @buf: temporary buffer
   * @bd: descriptor for the good/bad block search pattern
   *
   * The function checks the results of the previous call to read_bbt and creates
   * / updates the bbt(s) if necessary. Creation is necessary if no bbt was found
   * for the chip/device. Update is necessary if one of the tables is missing or
   * the version nr. of one table is less than the other.
   */
  static int check_create(struct nand_chip *this, uint8_t *buf,
  			struct nand_bbt_descr *bd)
  {
  	int i, chips, writeops, create, chipsel, res, res2;
  	struct nand_bbt_descr *td = this->bbt_td;
  	struct nand_bbt_descr *md = this->bbt_md;
  	struct nand_bbt_descr *rd, *rd2;
  
  	/* Do we have a bbt per chip? */
  	if (td->options & NAND_BBT_PERCHIP)
  		chips = nanddev_ntargets(&this->base);
  	else
  		chips = 1;
  
  	for (i = 0; i < chips; i++) {
  		writeops = 0;
  		create = 0;
  		rd = NULL;
  		rd2 = NULL;
  		res = res2 = 0;
  		/* Per chip or per device? */
  		chipsel = (td->options & NAND_BBT_PERCHIP) ? i : -1;
  		/* Mirrored table available? */
  		if (md) {
  			if (td->pages[i] == -1 && md->pages[i] == -1) {
  				create = 1;
  				writeops = 0x03;
  			} else if (td->pages[i] == -1) {
  				rd = md;
  				writeops = 0x01;
  			} else if (md->pages[i] == -1) {
  				rd = td;
  				writeops = 0x02;
  			} else if (td->version[i] == md->version[i]) {
  				rd = td;
  				if (!(td->options & NAND_BBT_VERSION))
  					rd2 = md;
  			} else if (((int8_t)(td->version[i] - md->version[i])) > 0) {
  				rd = td;
  				writeops = 0x02;
  			} else {
  				rd = md;
  				writeops = 0x01;
  			}
  		} else {
  			if (td->pages[i] == -1) {
  				create = 1;
  				writeops = 0x01;
  			} else {
  				rd = td;
  			}
  		}
  
  		if (create) {
  			/* Create the bad block table by scanning the device? */
  			if (!(td->options & NAND_BBT_CREATE))
  				continue;
  
  			/* Create the table in memory by scanning the chip(s) */
  			if (!(this->bbt_options & NAND_BBT_CREATE_EMPTY))
  				create_bbt(this, buf, bd, chipsel);
  
  			td->version[i] = 1;
  			if (md)
  				md->version[i] = 1;
  		}
  
  		/* Read back first? */
  		if (rd) {
  			res = read_abs_bbt(this, buf, rd, chipsel);
  			if (mtd_is_eccerr(res)) {
  				/* Mark table as invalid */
  				rd->pages[i] = -1;
  				rd->version[i] = 0;
  				i--;
  				continue;
  			}
  		}
  		/* If they weren't versioned, read both */
  		if (rd2) {
  			res2 = read_abs_bbt(this, buf, rd2, chipsel);
  			if (mtd_is_eccerr(res2)) {
  				/* Mark table as invalid */
  				rd2->pages[i] = -1;
  				rd2->version[i] = 0;
  				i--;
  				continue;
  			}
  		}
  
  		/* Scrub the flash table(s)? */
  		if (mtd_is_bitflip(res) || mtd_is_bitflip(res2))
  			writeops = 0x03;
  
  		/* Update version numbers before writing */
  		if (md) {
  			td->version[i] = max(td->version[i], md->version[i]);
  			md->version[i] = td->version[i];
  		}
  
  		/* Write the bad block table to the device? */
  		if ((writeops & 0x01) && (td->options & NAND_BBT_WRITE)) {
  			res = write_bbt(this, buf, td, md, chipsel);
  			if (res < 0)
  				return res;
  		}
  
  		/* Write the mirror bad block table to the device? */
  		if ((writeops & 0x02) && md && (md->options & NAND_BBT_WRITE)) {
  			res = write_bbt(this, buf, md, td, chipsel);
  			if (res < 0)
  				return res;
  		}
  	}
  	return 0;
  }
  
  /**
   * nand_update_bbt - update bad block table(s)
   * @this: the NAND device
   * @offs: the offset of the newly marked block
   *
   * The function updates the bad block table(s).
   */
  static int nand_update_bbt(struct nand_chip *this, loff_t offs)
  {
  	struct mtd_info *mtd = nand_to_mtd(this);
  	int len, res = 0;
  	int chip, chipsel;
  	uint8_t *buf;
  	struct nand_bbt_descr *td = this->bbt_td;
  	struct nand_bbt_descr *md = this->bbt_md;
  
  	if (!this->bbt || !td)
  		return -EINVAL;
  
  	/* Allocate a temporary buffer for one eraseblock incl. oob */
  	len = (1 << this->bbt_erase_shift);
  	len += (len >> this->page_shift) * mtd->oobsize;
  	buf = kmalloc(len, GFP_KERNEL);
  	if (!buf)
  		return -ENOMEM;
  
  	/* Do we have a bbt per chip? */
  	if (td->options & NAND_BBT_PERCHIP) {
  		chip = (int)(offs >> this->chip_shift);
  		chipsel = chip;
  	} else {
  		chip = 0;
  		chipsel = -1;
  	}
  
  	td->version[chip]++;
  	if (md)
  		md->version[chip]++;
  
  	/* Write the bad block table to the device? */
  	if (td->options & NAND_BBT_WRITE) {
  		res = write_bbt(this, buf, td, md, chipsel);
  		if (res < 0)
  			goto out;
  	}
  	/* Write the mirror bad block table to the device? */
  	if (md && (md->options & NAND_BBT_WRITE)) {
  		res = write_bbt(this, buf, md, td, chipsel);
  	}
  
   out:
  	kfree(buf);
  	return res;
  }
  
  /**
   * mark_bbt_region - [GENERIC] mark the bad block table regions
   * @this: the NAND device
   * @td: bad block table descriptor
   *
   * The bad block table regions are marked as "bad" to prevent accidental
   * erasures / writes. The regions are identified by the mark 0x02.
   */
  static void mark_bbt_region(struct nand_chip *this, struct nand_bbt_descr *td)
  {
  	u64 targetsize = nanddev_target_size(&this->base);
  	struct mtd_info *mtd = nand_to_mtd(this);
  	int i, j, chips, block, nrblocks, update;
  	uint8_t oldval;
  
  	/* Do we have a bbt per chip? */
  	if (td->options & NAND_BBT_PERCHIP) {
  		chips = nanddev_ntargets(&this->base);
  		nrblocks = (int)(targetsize >> this->bbt_erase_shift);
  	} else {
  		chips = 1;
  		nrblocks = (int)(mtd->size >> this->bbt_erase_shift);
  	}
  
  	for (i = 0; i < chips; i++) {
  		if ((td->options & NAND_BBT_ABSPAGE) ||
  		    !(td->options & NAND_BBT_WRITE)) {
  			if (td->pages[i] == -1)
  				continue;
  			block = td->pages[i] >> (this->bbt_erase_shift - this->page_shift);
  			oldval = bbt_get_entry(this, block);
  			bbt_mark_entry(this, block, BBT_BLOCK_RESERVED);
  			if ((oldval != BBT_BLOCK_RESERVED) &&
  					td->reserved_block_code)
  				nand_update_bbt(this, (loff_t)block <<
  						this->bbt_erase_shift);
  			continue;
  		}
  		update = 0;
  		if (td->options & NAND_BBT_LASTBLOCK)
  			block = ((i + 1) * nrblocks) - td->maxblocks;
  		else
  			block = i * nrblocks;
  		for (j = 0; j < td->maxblocks; j++) {
  			oldval = bbt_get_entry(this, block);
  			bbt_mark_entry(this, block, BBT_BLOCK_RESERVED);
  			if (oldval != BBT_BLOCK_RESERVED)
  				update = 1;
  			block++;
  		}
  		/*
  		 * If we want reserved blocks to be recorded to flash, and some
  		 * new ones have been marked, then we need to update the stored
  		 * bbts.  This should only happen once.
  		 */
  		if (update && td->reserved_block_code)
  			nand_update_bbt(this, (loff_t)(block - 1) <<
  					this->bbt_erase_shift);
  	}
  }
  
  /**
   * verify_bbt_descr - verify the bad block description
   * @this: the NAND device
   * @bd: the table to verify
   *
   * This functions performs a few sanity checks on the bad block description
   * table.
   */
  static void verify_bbt_descr(struct nand_chip *this, struct nand_bbt_descr *bd)
  {
  	u64 targetsize = nanddev_target_size(&this->base);
  	struct mtd_info *mtd = nand_to_mtd(this);
  	u32 pattern_len;
  	u32 bits;
  	u32 table_size;
  
  	if (!bd)
  		return;
  
  	pattern_len = bd->len;
  	bits = bd->options & NAND_BBT_NRBITS_MSK;
  
  	BUG_ON((this->bbt_options & NAND_BBT_NO_OOB) &&
  			!(this->bbt_options & NAND_BBT_USE_FLASH));
  	BUG_ON(!bits);
  
  	if (bd->options & NAND_BBT_VERSION)
  		pattern_len++;
  
  	if (bd->options & NAND_BBT_NO_OOB) {
  		BUG_ON(!(this->bbt_options & NAND_BBT_USE_FLASH));
  		BUG_ON(!(this->bbt_options & NAND_BBT_NO_OOB));
  		BUG_ON(bd->offs);
  		if (bd->options & NAND_BBT_VERSION)
  			BUG_ON(bd->veroffs != bd->len);
  		BUG_ON(bd->options & NAND_BBT_SAVECONTENT);
  	}
  
  	if (bd->options & NAND_BBT_PERCHIP)
  		table_size = targetsize >> this->bbt_erase_shift;
  	else
  		table_size = mtd->size >> this->bbt_erase_shift;
  	table_size >>= 3;
  	table_size *= bits;
  	if (bd->options & NAND_BBT_NO_OOB)
  		table_size += pattern_len;
  	BUG_ON(table_size > (1 << this->bbt_erase_shift));
  }
  
  /**
   * nand_scan_bbt - [NAND Interface] scan, find, read and maybe create bad block table(s)
   * @this: the NAND device
   * @bd: descriptor for the good/bad block search pattern
   *
   * The function checks, if a bad block table(s) is/are already available. If
   * not it scans the device for manufacturer marked good / bad blocks and writes
   * the bad block table(s) to the selected place.
   *
   * The bad block table memory is allocated here. It must be freed by calling
   * the nand_free_bbt function.
   */
  static int nand_scan_bbt(struct nand_chip *this, struct nand_bbt_descr *bd)
  {
  	struct mtd_info *mtd = nand_to_mtd(this);
  	int len, res;
  	uint8_t *buf;
  	struct nand_bbt_descr *td = this->bbt_td;
  	struct nand_bbt_descr *md = this->bbt_md;
  
  	len = (mtd->size >> (this->bbt_erase_shift + 2)) ? : 1;
  	/*
  	 * Allocate memory (2bit per block) and clear the memory bad block
  	 * table.
  	 */
  	this->bbt = kzalloc(len, GFP_KERNEL);
  	if (!this->bbt)
  		return -ENOMEM;
  
  	/*
  	 * If no primary table descriptor is given, scan the device to build a
  	 * memory based bad block table.
  	 */
  	if (!td) {
  		if ((res = nand_memory_bbt(this, bd))) {
  			pr_err("nand_bbt: can't scan flash and build the RAM-based BBT\n");
  			goto err_free_bbt;
  		}
  		return 0;
  	}
  	verify_bbt_descr(this, td);
  	verify_bbt_descr(this, md);
  
  	/* Allocate a temporary buffer for one eraseblock incl. oob */
  	len = (1 << this->bbt_erase_shift);
  	len += (len >> this->page_shift) * mtd->oobsize;
  	buf = vmalloc(len);
  	if (!buf) {
  		res = -ENOMEM;
  		goto err_free_bbt;
  	}
  
  	/* Is the bbt at a given page? */
  	if (td->options & NAND_BBT_ABSPAGE) {
  		read_abs_bbts(this, buf, td, md);
  	} else {
  		/* Search the bad block table using a pattern in oob */
  		search_read_bbts(this, buf, td, md);
  	}
  
  	res = check_create(this, buf, bd);
  	if (res)
  		goto err_free_buf;
  
  	/* Prevent the bbt regions from erasing / writing */
  	mark_bbt_region(this, td);
  	if (md)
  		mark_bbt_region(this, md);
  
  	vfree(buf);
  	return 0;
  
  err_free_buf:
  	vfree(buf);
  err_free_bbt:
  	kfree(this->bbt);
  	this->bbt = NULL;
  	return res;
  }
  
  /*
   * Define some generic bad / good block scan pattern which are used
   * while scanning a device for factory marked good / bad blocks.
   */
  static uint8_t scan_ff_pattern[] = { 0xff, 0xff };
  
  /* Generic flash bbt descriptors */
  static uint8_t bbt_pattern[] = {'B', 'b', 't', '0' };
  static uint8_t mirror_pattern[] = {'1', 't', 'b', 'B' };
  
  static struct nand_bbt_descr bbt_main_descr = {
  	.options = NAND_BBT_LASTBLOCK | NAND_BBT_CREATE | NAND_BBT_WRITE
  		| NAND_BBT_2BIT | NAND_BBT_VERSION | NAND_BBT_PERCHIP,
  	.offs =	8,
  	.len = 4,
  	.veroffs = 12,
  	.maxblocks = NAND_BBT_SCAN_MAXBLOCKS,
  	.pattern = bbt_pattern
  };
  
  static struct nand_bbt_descr bbt_mirror_descr = {
  	.options = NAND_BBT_LASTBLOCK | NAND_BBT_CREATE | NAND_BBT_WRITE
  		| NAND_BBT_2BIT | NAND_BBT_VERSION | NAND_BBT_PERCHIP,
  	.offs =	8,
  	.len = 4,
  	.veroffs = 12,
  	.maxblocks = NAND_BBT_SCAN_MAXBLOCKS,
  	.pattern = mirror_pattern
  };
  
  static struct nand_bbt_descr bbt_main_no_oob_descr = {
  	.options = NAND_BBT_LASTBLOCK | NAND_BBT_CREATE | NAND_BBT_WRITE
  		| NAND_BBT_2BIT | NAND_BBT_VERSION | NAND_BBT_PERCHIP
  		| NAND_BBT_NO_OOB,
  	.len = 4,
  	.veroffs = 4,
  	.maxblocks = NAND_BBT_SCAN_MAXBLOCKS,
  	.pattern = bbt_pattern
  };
  
  static struct nand_bbt_descr bbt_mirror_no_oob_descr = {
  	.options = NAND_BBT_LASTBLOCK | NAND_BBT_CREATE | NAND_BBT_WRITE
  		| NAND_BBT_2BIT | NAND_BBT_VERSION | NAND_BBT_PERCHIP
  		| NAND_BBT_NO_OOB,
  	.len = 4,
  	.veroffs = 4,
  	.maxblocks = NAND_BBT_SCAN_MAXBLOCKS,
  	.pattern = mirror_pattern
  };
  
  #define BADBLOCK_SCAN_MASK (~NAND_BBT_NO_OOB)
  /**
   * nand_create_badblock_pattern - [INTERN] Creates a BBT descriptor structure
   * @this: NAND chip to create descriptor for
   *
   * This function allocates and initializes a nand_bbt_descr for BBM detection
   * based on the properties of @this. The new descriptor is stored in
   * this->badblock_pattern. Thus, this->badblock_pattern should be NULL when
   * passed to this function.
   */
  static int nand_create_badblock_pattern(struct nand_chip *this)
  {
  	struct nand_bbt_descr *bd;
  	if (this->badblock_pattern) {
  		pr_warn("Bad block pattern already allocated; not replacing\n");
  		return -EINVAL;
  	}
  	bd = kzalloc(sizeof(*bd), GFP_KERNEL);
  	if (!bd)
  		return -ENOMEM;
  	bd->options = this->bbt_options & BADBLOCK_SCAN_MASK;
  	bd->offs = this->badblockpos;
  	bd->len = (this->options & NAND_BUSWIDTH_16) ? 2 : 1;
  	bd->pattern = scan_ff_pattern;
  	bd->options |= NAND_BBT_DYNAMICSTRUCT;
  	this->badblock_pattern = bd;
  	return 0;
  }
  
  /**
   * nand_create_bbt - [NAND Interface] Select a default bad block table for the device
   * @this: NAND chip object
   *
   * This function selects the default bad block table support for the device and
   * calls the nand_scan_bbt function.
   */
  int nand_create_bbt(struct nand_chip *this)
  {
  	int ret;
  
  	/* Is a flash based bad block table requested? */
  	if (this->bbt_options & NAND_BBT_USE_FLASH) {
  		/* Use the default pattern descriptors */
  		if (!this->bbt_td) {
  			if (this->bbt_options & NAND_BBT_NO_OOB) {
  				this->bbt_td = &bbt_main_no_oob_descr;
  				this->bbt_md = &bbt_mirror_no_oob_descr;
  			} else {
  				this->bbt_td = &bbt_main_descr;
  				this->bbt_md = &bbt_mirror_descr;
  			}
  		}
  	} else {
  		this->bbt_td = NULL;
  		this->bbt_md = NULL;
  	}
  
  	if (!this->badblock_pattern) {
  		ret = nand_create_badblock_pattern(this);
  		if (ret)
  			return ret;
  	}
  
  	return nand_scan_bbt(this, this->badblock_pattern);
  }
  EXPORT_SYMBOL(nand_create_bbt);
  
  /**
   * nand_isreserved_bbt - [NAND Interface] Check if a block is reserved
   * @this: NAND chip object
   * @offs: offset in the device
   */
  int nand_isreserved_bbt(struct nand_chip *this, loff_t offs)
  {
  	int block;
  
  	block = (int)(offs >> this->bbt_erase_shift);
  	return bbt_get_entry(this, block) == BBT_BLOCK_RESERVED;
  }
  
  /**
   * nand_isbad_bbt - [NAND Interface] Check if a block is bad
   * @this: NAND chip object
   * @offs: offset in the device
   * @allowbbt: allow access to bad block table region
   */
  int nand_isbad_bbt(struct nand_chip *this, loff_t offs, int allowbbt)
  {
  	int block, res;
  
  	block = (int)(offs >> this->bbt_erase_shift);
  	res = bbt_get_entry(this, block);
  
  	pr_debug("nand_isbad_bbt(): bbt info for offs 0x%08x: (block %d) 0x%02x\n",
  		 (unsigned int)offs, block, res);
  
  	switch (res) {
  	case BBT_BLOCK_GOOD:
  		return 0;
  	case BBT_BLOCK_WORN:
  		return 1;
  	case BBT_BLOCK_RESERVED:
  		return allowbbt ? 0 : 1;
  	}
  	return 1;
  }
  
  /**
   * nand_markbad_bbt - [NAND Interface] Mark a block bad in the BBT
   * @this: NAND chip object
   * @offs: offset of the bad block
   */
  int nand_markbad_bbt(struct nand_chip *this, loff_t offs)
  {
  	int block, ret = 0;
  
  	block = (int)(offs >> this->bbt_erase_shift);
  
  	/* Mark bad block in memory */
  	bbt_mark_entry(this, block, BBT_BLOCK_WORN);
  
  	/* Update flash-based bad block table */
  	if (this->bbt_options & NAND_BBT_USE_FLASH)
  		ret = nand_update_bbt(this, offs);
  
  	return ret;
  }
  