MTD: NAND flash simulator

We want to contribute the NAND flash simulator which we successfully use 
when developing JFFS2. It is very useful tool which helps to develop 
without real flash.

It supports several options which allow to select which flash type to 
emulate (just flash IDs which are in nand_ids.c file). See modinfo for 
other options.
Signed-off-by: Artem B. Bityuckiy <dedekind@yandex.ru>
Signed-off-by: David Woodhouse <dwmw2@infradead.org>

drivers/mtd/nand/Kconfig

 # drivers/mtd/nand/Kconfig
-# $Id: Kconfig,v 1.23 2004/11/24 19:33:56 rpurdie Exp $
+# $Id: Kconfig,v 1.24 2004/11/26 12:28:22 dedekind Exp $
 
 menu "NAND Flash Device Drivers"
 	depends on MTD!=n
@@ -197,4 +197,12 @@ config MTD_NAND_DISKONCHIP_BBTWRITE
  	bool "Support for NAND Flash on Sharp SL Series (C7xx + others)"
  	depends on MTD_NAND	&& ARCH_PXA
  
+ config MTD_NAND_NANDSIM
+ 	bool "Support for NAND Flash Simulator"
+ 	depends on MTD_NAND
+
+	help
+	  The simulator may simulate verious NAND flash chips for the
+	  MTD nand layer.
+ 
 endmenu

drivers/mtd/nand/Makefile

 #
 # linux/drivers/nand/Makefile
 #
-# $Id: Makefile.common,v 1.14 2004/11/24 19:33:56 rpurdie Exp $
+# $Id: Makefile.common,v 1.15 2004/11/26 12:28:22 dedekind Exp $
 
 obj-$(CONFIG_MTD_NAND)			+= nand.o nand_ecc.o
 obj-$(CONFIG_MTD_NAND_IDS)		+= nand_ids.o
@@ -19,5 +19,6 @@ obj-$(CONFIG_MTD_NAND_DISKONCHIP)	+= diskonchip.o
 obj-$(CONFIG_MTD_NAND_H1900)		+= h1910.o
 obj-$(CONFIG_MTD_NAND_RTC_FROM4)	+= rtc_from4.o
 obj-$(CONFIG_MTD_NAND_SHARPSL)		+= sharpsl.o
+obj-$(CONFIG_MTD_NAND_NANDSIM)		+= nandsim.o
 
 nand-objs = nand_base.o nand_bbt.o

drivers/mtd/nand/nandsim.c

+/*
+ * NAND flash simulator.
+ *
+ * Author: Artem B. Bityuckiy <dedekind@oktetlabs.ru>, <dedekind@infradead.org>
+ *
+ * Copyright (C) 2004 Nokia Corporation 
+ *
+ * Note: NS means "NAND Simulator".
+ * Note: Input means input TO flash chip, output means output FROM chip.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation; either version 2, or (at your option) any later
+ * version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
+ * Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307, USA
+ *
+ * $Id: nandsim.c,v 1.3 2004/11/26 13:00:24 dedekind Exp $
+ */
+
+#include <linux/config.h>
+#include <linux/init.h>
+#include <linux/types.h>
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/vmalloc.h>
+#include <linux/slab.h>
+#include <linux/errno.h>
+#include <linux/string.h>
+#include <linux/mtd/mtd.h>
+#include <linux/mtd/nand.h>
+#include <linux/mtd/partitions.h>
+#include <linux/delay.h>
+#ifdef CONFIG_NS_ABS_POS
+#include <asm/io.h>
+#endif
+
+
+/* Default simulator parameters values */
+#if !defined(CONFIG_NANDSIM_FIRST_ID_BYTE)  || \
+    !defined(CONFIG_NANDSIM_SECOND_ID_BYTE) || \
+    !defined(CONFIG_NANDSIM_THIRD_ID_BYTE)  || \
+    !defined(CONFIG_NANDSIM_FOURTH_ID_BYTE)
+#define CONFIG_NANDSIM_FIRST_ID_BYTE  0x98
+#define CONFIG_NANDSIM_SECOND_ID_BYTE 0x36
+#define CONFIG_NANDSIM_THIRD_ID_BYTE  0xFF /* No byte */
+#define CONFIG_NANDSIM_FOURTH_ID_BYTE 0xFF /* No byte */
+#endif
+
+#ifndef CONFIG_NANDSIM_ACCESS_DELAY
+#define CONFIG_NANDSIM_ACCESS_DELAY 25
+#endif
+#ifndef CONFIG_NANDSIM_PROGRAMM_DELAY
+#define CONFIG_NANDSIM_PROGRAMM_DELAY 200
+#endif
+#ifndef CONFIG_NANDSIM_ERASE_DELAY
+#define CONFIG_NANDSIM_ERASE_DELAY 2
+#endif
+#ifndef CONFIG_NANDSIM_OUTPUT_CYCLE
+#define CONFIG_NANDSIM_OUTPUT_CYCLE 40
+#endif
+#ifndef CONFIG_NANDSIM_INPUT_CYCLE
+#define CONFIG_NANDSIM_INPUT_CYCLE  50
+#endif
+#ifndef CONFIG_NANDSIM_BUS_WIDTH
+#define CONFIG_NANDSIM_BUS_WIDTH  8
+#endif
+#ifndef CONFIG_NANDSIM_DO_DELAYS
+#define CONFIG_NANDSIM_DO_DELAYS  0
+#endif
+#ifndef CONFIG_NANDSIM_LOG
+#define CONFIG_NANDSIM_LOG        0
+#endif
+#ifndef CONFIG_NANDSIM_DBG
+#define CONFIG_NANDSIM_DBG        0
+#endif
+
+static uint first_id_byte  = CONFIG_NANDSIM_FIRST_ID_BYTE;
+static uint second_id_byte = CONFIG_NANDSIM_SECOND_ID_BYTE;
+static uint third_id_byte  = CONFIG_NANDSIM_THIRD_ID_BYTE;
+static uint fourth_id_byte = CONFIG_NANDSIM_FOURTH_ID_BYTE;
+static uint access_delay   = CONFIG_NANDSIM_ACCESS_DELAY;
+static uint programm_delay = CONFIG_NANDSIM_PROGRAMM_DELAY;
+static uint erase_delay    = CONFIG_NANDSIM_ERASE_DELAY;
+static uint output_cycle   = CONFIG_NANDSIM_OUTPUT_CYCLE;
+static uint input_cycle    = CONFIG_NANDSIM_INPUT_CYCLE;
+static uint bus_width      = CONFIG_NANDSIM_BUS_WIDTH;
+static uint do_delays      = CONFIG_NANDSIM_DO_DELAYS;
+static uint log            = CONFIG_NANDSIM_LOG;
+static uint dbg            = CONFIG_NANDSIM_DBG;
+
+module_param(first_id_byte,  uint, 0400);
+module_param(second_id_byte, uint, 0400);
+module_param(third_id_byte,  uint, 0400);
+module_param(fourth_id_byte, uint, 0400);
+module_param(access_delay,   uint, 0400);
+module_param(programm_delay, uint, 0400);
+module_param(erase_delay,    uint, 0400);
+module_param(output_cycle,   uint, 0400);
+module_param(input_cycle,    uint, 0400);
+module_param(bus_width,      uint, 0400);
+module_param(do_delays,      uint, 0400);
+module_param(log,            uint, 0400);
+module_param(dbg,            uint, 0400);
+
+MODULE_PARM_DESC(first_id_byte,  "The fist byte returned by NAND Flash 'read ID' command (manufaturer ID)");
+MODULE_PARM_DESC(second_id_byte, "The second byte returned by NAND Flash 'read ID' command (chip ID)");
+MODULE_PARM_DESC(third_id_byte,  "The third byte returned by NAND Flash 'read ID' command");
+MODULE_PARM_DESC(fourth_id_byte, "The fourth byte returned by NAND Flash 'read ID' command");
+MODULE_PARM_DESC(access_delay,   "Initial page access delay (microiseconds)");
+MODULE_PARM_DESC(programm_delay, "Page programm delay (microseconds");
+MODULE_PARM_DESC(erase_delay,    "Sector erase delay (milliseconds)");
+MODULE_PARM_DESC(output_cycle,   "Word output (from flash) time (nanodeconds)");
+MODULE_PARM_DESC(input_cycle,    "Word input (to flash) time (nanodeconds)");
+MODULE_PARM_DESC(bus_width,      "Chip's bus width (8- or 16-bit)");
+MODULE_PARM_DESC(do_delays,      "Simulate NAND delays using busy-waits if not zero");
+MODULE_PARM_DESC(log,            "Perform logging if not zero");
+MODULE_PARM_DESC(dbg,            "Output debug information if not zero");
+
+/* 
+ * There is no macro for 0x30 command which is used in "large page"
+ * devices in standard mtd header, define it here. 
+ */
+#define NAND_CMD_READ2LP 0x30
+
+/* The largest possible page size */
+#define NS_LARGEST_PAGE_SIZE	2048
+	
+/* The prefix for simulator output */
+#define NS_OUTPUT_PREFIX "[nandsim]"
+
+/* Simulator's output macros (logging, debugging, warning, error) */
+#define NS_LOG(args...) \
+	do { if (log) printk(KERN_INFO NS_OUTPUT_PREFIX " log: " args); } while(0)
+#define NS_DBG(args...) \
+	do { if (dbg) printk(KERN_INFO NS_OUTPUT_PREFIX " debug: " args); } while(0)
+#define NS_WARN(args...) \
+	do { printk(KERN_INFO NS_OUTPUT_PREFIX " warnig: " args); } while(0)
+#define NS_ERR(args...) \
+	do { printk(KERN_INFO NS_OUTPUT_PREFIX " errorr: " args); } while(0)
+
+/* Busy-wait delay macros (microseconds, milliseconds) */
+#define NS_UDELAY(us) \
+        do { if (do_delays) udelay(us); } while(0)
+#define NS_MDELAY(us) \
+        do { if (do_delays) mdelay(us); } while(0)
+	
+/* Is the nandsim structure initialized ? */
+#define NS_IS_INITIALIZED(ns) ((ns)->geom.totsz != 0)
+
+/* Good operation completion status */
+#define NS_STATUS_OK(ns) (NAND_STATUS_READY | (NAND_STATUS_WP * ((ns)->lines.wp == 0)))
+
+/* Operation failed completion status */
+#define NS_STATUS_FAILED(ns) (NAND_STATUS_FAIL | NS_STATUS_OK(ns)) 
+
+/* Calculate the page offset in flash RAM image by (row, column) address */
+#define NS_RAW_OFFSET(ns) \
+	(((ns)->regs.row << (ns)->geom.pgshift) + ((ns)->regs.row * (ns)->geom.oobsz) + (ns)->regs.column)
+	
+/* Calculate the OOB offset in flash RAM image by (row, column) address */
+#define NS_RAW_OFFSET_OOB(ns) (NS_RAW_OFFSET(ns) + ns->geom.pgsz)
+
+/* After a command is input, the simulator goes to one of the following states */
+#define STATE_CMD_READ0        0x00000001 /* read data from the beginning of page */
+#define STATE_CMD_READ1        0x00000002 /* read data from the second half of page */
+#define STATE_CMD_READ2LP      0x00000003 /* read data second command (large page devices) */
+#define STATE_CMD_PAGEPROG     0x00000004 /* start page programm */
+#define STATE_CMD_READOOB      0x00000005 /* read OOB area */
+#define STATE_CMD_ERASE1       0x00000006 /* sector erase first command */
+#define STATE_CMD_STATUS       0x00000007 /* read status */
+#define STATE_CMD_STATUS_M     0x00000008 /* read multi-plane status (isn't implemented) */
+#define STATE_CMD_SEQIN        0x00000009 /* sequential data imput */
+#define STATE_CMD_READID       0x0000000A /* read ID */
+#define STATE_CMD_ERASE2       0x0000000B /* sector erase second command */
+#define STATE_CMD_RESET        0x0000000C /* reset */
+#define STATE_CMD_MASK         0x0000000F /* command states mask */
+
+/* After an addres is input, the simulator goes to one of these states */
+#define STATE_ADDR_PAGE        0x00000010 /* full (row, column) address is accepted */
+#define STATE_ADDR_SEC         0x00000020 /* sector address was accepted */
+#define STATE_ADDR_ZERO        0x00000030 /* one byte zero address was accepted */
+#define STATE_ADDR_MASK        0x00000030 /* address states mask */
+
+/* Durind data input/output the simulator is in these states */
+#define STATE_DATAIN           0x00000100 /* waiting for data input */
+#define STATE_DATAIN_MASK      0x00000100 /* data input states mask */
+
+#define STATE_DATAOUT          0x00001000 /* waiting for page data output */
+#define STATE_DATAOUT_ID       0x00002000 /* waiting for ID bytes output */
+#define STATE_DATAOUT_STATUS   0x00003000 /* waiting for status output */
+#define STATE_DATAOUT_STATUS_M 0x00004000 /* waiting for multi-plane status output */
+#define STATE_DATAOUT_MASK     0x00007000 /* data output states mask */
+
+/* Previous operation is done, ready to accept new requests */
+#define STATE_READY            0x00000000
+
+/* This state is used to mark that the next state isn't known yet */
+#define STATE_UNKNOWN          0x10000000
+
+/* Simulator's actions bit masks */
+#define ACTION_CPY       0x00100000 /* copy page/OOB to the internal buffer */
+#define ACTION_PRGPAGE   0x00200000 /* programm the internal buffer to flash */
+#define ACTION_SECERASE  0x00300000 /* erase sector */
+#define ACTION_ZEROOFF   0x00400000 /* don't add any offset to address */
+#define ACTION_HALFOFF   0x00500000 /* add to address half of page */
+#define ACTION_OOBOFF    0x00600000 /* add to address OOB offset */
+#define ACTION_MASK      0x00700000 /* action mask */
+
+#define NS_OPER_NUM      12 /* Number of operations supported by the simulator */
+#define NS_OPER_STATES   6  /* Maximum number of states in operation */
+
+#define OPT_ANY          0xFFFFFFFF /* any chip supports this operation */
+#define OPT_PAGE256      0x00000001 /* 256-byte  page chips */
+#define OPT_PAGE512      0x00000002 /* 512-byte  page chips */
+#define OPT_PAGE2048     0x00000008 /* 2048-byte page chips */
+#define OPT_SMARTMEDIA   0x00000010 /* SmartMedia technology chips */
+#define OPT_AUTOINCR     0x00000020 /* page number auto inctimentation is possible */
+#define OPT_PAGE512_8BIT 0x00000040 /* 512-byte page chips with 8-bit bus width */
+#define OPT_LARGEPAGE    (OPT_PAGE2048) /* 2048-byte page chips */
+#define OPT_SMALLPAGE    (OPT_PAGE256  | OPT_PAGE512)  /* 256 and 512-byte page chips */
+
+/* Remove action bits ftom state */
+#define NS_STATE(x) ((x) & ~ACTION_MASK)
+	
+/* 
+ * Maximum previous states which need to be saved. Currently saving is
+ * only needed for page programm operation with preceeded read command
+ * (which is only valid for 512-byte pages).
+ */
+#define NS_MAX_PREVSTATES 1
+
+/* 
+ * The structure which describes all the internal simulator data.
+ */
+struct nandsim {
+	struct mtd_partition part;
+
+	uint busw;              /* flash chip bus width (8 or 16) */
+	u_char ids[4];          /* chip's ID bytes */
+	uint32_t options;       /* chip's characteristic bits */
+	uint32_t state;         /* current chip state */
+	uint32_t nxstate;       /* next expected state */
+	
+	uint32_t *op;           /* current operation, NULL operations isn't known yet  */
+	uint32_t pstates[NS_MAX_PREVSTATES]; /* previous states */
+	uint16_t npstates;      /* number of previous states saved */
+	uint16_t stateidx;      /* current state index */
+
+	/* The simulated NAND flash image */
+	union flash_media {
+		u_char *byte;
+		uint16_t    *word;
+	} mem;
+
+	/* Internal buffer of page + OOB size bytes */
+	union internal_buffer {
+		u_char *byte;    /* for byte access */
+		uint16_t *word;  /* for 16-bit word access */
+	} buf;
+
+	/* NAND flash "geometry" */
+	struct nandsin_geometry {
+		uint32_t totsz;     /* total flash size, bytes */
+		uint32_t secsz;     /* flash sector (erase block) size, bytes */
+		uint pgsz;          /* NAND flash page size, bytes */
+		uint oobsz;         /* page OOB area size, bytes */
+		uint32_t totszoob;  /* total flash size including OOB, bytes */
+		uint pgszoob;       /* page size including OOB , bytes*/
+		uint secszoob;      /* sector size including OOB, bytes */
+		uint pgnum;         /* total number of pages */
+		uint pgsec;         /* number of pages per sector */
+		uint secshift;      /* bits number in sector size */
+		uint pgshift;       /* bits number in page size */
+		uint oobshift;      /* bits number in OOB size */
+		uint pgaddrbytes;   /* bytes per page address */
+		uint secaddrbytes;  /* bytes per sector address */
+		uint idbytes;       /* the number ID bytes that this chip outputs */
+	} geom;
+
+	/* NAND flash internal registers */
+	struct nandsim_regs {
+		unsigned command; /* the command register */
+		u_char   status;  /* the status register */
+		uint     row;     /* the page number */
+		uint     column;  /* the offset within page */
+		uint     count;   /* internal counter */
+		uint     num;     /* number of bytes which must be processed */
+		uint     off;     /* fixed page offset */
+	} regs;
+
+	/* NAND flash lines state */
+        struct ns_lines_status {
+                int ce;  /* chip Enable */
+                int cle; /* command Latch Enable */
+                int ale; /* address Latch Enable */
+                int wp;  /* write Protect */
+        } lines;
+};
+
+/*
+ * Operations array. To perform any operation the simulator must pass
+ * through the correspondent states chain.
+ */
+static struct nandsim_operations {
+	uint32_t reqopts;  /* options which are required to perform the operation */
+	uint32_t states[NS_OPER_STATES]; /* operation's states */
+} ops[NS_OPER_NUM] = {
+	/* Read page + OOB from the beginning */
+	{OPT_SMALLPAGE, {STATE_CMD_READ0 | ACTION_ZEROOFF, STATE_ADDR_PAGE | ACTION_CPY,
+			STATE_DATAOUT, STATE_READY}},
+	/* Read page + OOB from the second half */
+	{OPT_PAGE512_8BIT, {STATE_CMD_READ1 | ACTION_HALFOFF, STATE_ADDR_PAGE | ACTION_CPY,
+			STATE_DATAOUT, STATE_READY}},
+	/* Read OOB */
+	{OPT_SMALLPAGE, {STATE_CMD_READOOB | ACTION_OOBOFF, STATE_ADDR_PAGE | ACTION_CPY,
+			STATE_DATAOUT, STATE_READY}},
+	/* Programm page starting from the beginning */
+	{OPT_ANY, {STATE_CMD_SEQIN, STATE_ADDR_PAGE, STATE_DATAIN,
+			STATE_CMD_PAGEPROG | ACTION_PRGPAGE, STATE_READY}},
+	/* Programm page starting from the beginning */
+	{OPT_SMALLPAGE, {STATE_CMD_READ0, STATE_CMD_SEQIN | ACTION_ZEROOFF, STATE_ADDR_PAGE,
+			      STATE_DATAIN, STATE_CMD_PAGEPROG | ACTION_PRGPAGE, STATE_READY}},
+	/* Programm page starting from the second half */
+	{OPT_PAGE512, {STATE_CMD_READ1, STATE_CMD_SEQIN | ACTION_HALFOFF, STATE_ADDR_PAGE,
+			      STATE_DATAIN, STATE_CMD_PAGEPROG | ACTION_PRGPAGE, STATE_READY}},
+	/* Programm OOB */
+	{OPT_SMALLPAGE, {STATE_CMD_READOOB, STATE_CMD_SEQIN | ACTION_OOBOFF, STATE_ADDR_PAGE,
+			      STATE_DATAIN, STATE_CMD_PAGEPROG | ACTION_PRGPAGE, STATE_READY}},
+	/* Erase sector */
+	{OPT_ANY, {STATE_CMD_ERASE1, STATE_ADDR_SEC, STATE_CMD_ERASE2 | ACTION_SECERASE, STATE_READY}},
+	/* Read status */
+	{OPT_ANY, {STATE_CMD_STATUS, STATE_DATAOUT_STATUS, STATE_READY}},
+	/* Read multi-plane status */
+	{OPT_SMARTMEDIA, {STATE_CMD_STATUS_M, STATE_DATAOUT_STATUS_M, STATE_READY}},
+	/* Read ID */
+	{OPT_ANY, {STATE_CMD_READID, STATE_ADDR_ZERO, STATE_DATAOUT_ID, STATE_READY}},
+	/* Large page devices read page */
+	{OPT_LARGEPAGE, {STATE_CMD_READ0, STATE_ADDR_PAGE, STATE_CMD_READ2LP | ACTION_CPY,
+			       STATE_DATAOUT, STATE_READY}}
+};
+
+/* MTD structure for NAND controller */
+static struct mtd_info *nsmtd;
+
+static u_char ns_verify_buf[NS_LARGEST_PAGE_SIZE];
+
+/*
+ * Initialize the nandsim structure.
+ *
+ * RETURNS: 0 if success, -ERRNO if failure.
+ */
+static int
+init_nandsim(struct mtd_info *mtd)
+{
+	struct nand_chip *chip = (struct nand_chip *)mtd->priv;
+	struct nandsim   *ns   = (struct nandsim *)(chip->priv);
+	int i;
+
+	if (NS_IS_INITIALIZED(ns)) {
+		NS_ERR("init_nandsim: nandsim is already initialized\n");
+		return -EIO;
+	}
+
+	/* Force mtd to not do delays */
+	chip->chip_delay = 0;
+
+	/* Initialize the NAND flash parameters */
+	ns->busw = chip->options & NAND_BUSWIDTH_16 ? 16 : 8;
+	ns->geom.totsz    = mtd->size;
+	ns->geom.pgsz     = mtd->oobblock;
+	ns->geom.oobsz    = mtd->oobsize;
+	ns->geom.secsz    = mtd->erasesize;
+	ns->geom.pgszoob  = ns->geom.pgsz + ns->geom.oobsz;
+	ns->geom.pgnum    = ns->geom.totsz / ns->geom.pgsz;
+	ns->geom.totszoob = ns->geom.totsz + ns->geom.pgnum * ns->geom.oobsz;
+	ns->geom.secshift = ffs(ns->geom.secsz) - 1;
+	ns->geom.pgshift  = chip->page_shift;
+	ns->geom.oobshift = ffs(ns->geom.oobsz) - 1;
+	ns->geom.pgsec    = ns->geom.secsz / ns->geom.pgsz;
+	ns->geom.secszoob = ns->geom.secsz + ns->geom.oobsz * ns->geom.pgsec;
+	ns->options = 0;
+
+	if (ns->geom.pgsz == 256) {
+		ns->options |= OPT_PAGE256;
+	}
+	else if (ns->geom.pgsz == 512) {
+		ns->options |= (OPT_PAGE512 | OPT_AUTOINCR);
+		if (ns->busw == 8)
+			ns->options |= OPT_PAGE512_8BIT;
+	} else if (ns->geom.pgsz == 2048) {
+		ns->options |= OPT_PAGE2048;
+	} else {
+		NS_ERR("init_nandsim: unknown page size %u\n", ns->geom.pgsz);
+		return -EIO;
+	}
+
+	if (ns->options & OPT_SMALLPAGE) {
+		if (ns->geom.totsz < (64 << 20)) {
+			ns->geom.pgaddrbytes  = 3;
+			ns->geom.secaddrbytes = 2;
+		} else {
+			ns->geom.pgaddrbytes  = 4;
+			ns->geom.secaddrbytes = 3;
+		}
+	} else {
+		if (ns->geom.totsz <= (128 << 20)) {
+			ns->geom.pgaddrbytes  = 5;
+			ns->geom.secaddrbytes = 2;
+		} else {
+			ns->geom.pgaddrbytes  = 5;
+			ns->geom.secaddrbytes = 3;
+		}
+	}
+	
+	/* Detect how many ID bytes the NAND chip outputs */
+        for (i = 0; nand_flash_ids[i].name != NULL; i++) {
+                if (second_id_byte != nand_flash_ids[i].id)
+                        continue;
+		if (!(nand_flash_ids[i].options & NAND_NO_AUTOINCR))
+			ns->options |= OPT_AUTOINCR;
+	}
+
+	if (ns->busw == 16)
+		NS_WARN("16-bit flashes support wasn't tested\n");
+
+	printk("flash size: %u MiB\n",          ns->geom.totsz >> 20);
+	printk("page size: %u bytes\n",         ns->geom.pgsz);
+	printk("OOB area size: %u bytes\n",     ns->geom.oobsz);
+	printk("sector size: %u KiB\n",         ns->geom.secsz >> 10);
+	printk("pages number: %u\n",            ns->geom.pgnum);
+	printk("pages per sector: %u\n",        ns->geom.pgsec);
+	printk("bus width: %u\n",               ns->busw);
+	printk("bits in sector size: %u\n",     ns->geom.secshift);
+	printk("bits in page size: %u\n",       ns->geom.pgshift);
+	printk("bits in OOB size: %u\n",        ns->geom.oobshift);
+	printk("flash size with OOB: %u KiB\n", ns->geom.totszoob >> 10);
+	printk("page address bytes: %u\n",      ns->geom.pgaddrbytes);
+	printk("sector address bytes: %u\n",    ns->geom.secaddrbytes);
+	printk("options: %#x\n",                ns->options);
+
+	/* Map / allocate and initialize the flash image */
+#ifdef CONFIG_NS_ABS_POS
+	ns->mem.byte = ioremap(CONFIG_NS_ABS_POS, ns->geom.totszoob);
+	if (!ns->mem.byte) {
+		NS_ERR("init_nandsim: failed to map the NAND flash image at address %p\n", 
+			(void *)CONFIG_NS_ABS_POS);
+		return -ENOMEM;
+	}
+#else
+	ns->mem.byte = vmalloc(ns->geom.totszoob);
+	if (!ns->mem.byte) {
+		NS_ERR("init_nandsim: unable to allocate %u bytes for flash image\n",
+			ns->geom.totszoob);
+		return -ENOMEM;
+	}
+	memset(ns->mem.byte, 0xFF, ns->geom.totszoob);
+#endif
+
+	/* Allocate / initialize the internal buffer */
+	ns->buf.byte = kmalloc(ns->geom.pgszoob, GFP_KERNEL);
+	if (!ns->buf.byte) {
+		NS_ERR("init_nandsim: unable to allocate %u bytes for the internal buffer\n",
+			ns->geom.pgszoob);
+		goto error;
+	}
+	memset(ns->buf.byte, 0xFF, ns->geom.pgszoob);
+
+	/* Fill the partition_info structure */
+	ns->part.name   = "NAND simulator partition";
+	ns->part.offset = 0;
+	ns->part.size   = ns->geom.totsz;
+
+	return 0;
+
+error:
+#ifdef CONFIG_NS_ABS_POS
+	iounmap(ns->mem.byte);
+#else
+	vfree(ns->mem.byte);
+#endif
+
+	return -ENOMEM;
+}
+
+/*
+ * Free the nandsim structure.
+ */
+static void
+free_nandsim(struct nandsim *ns)
+{
+	kfree(ns->buf.byte);
+
+#ifdef CONFIG_NS_ABS_POS
+	iounmap(ns->mem.byte);
+#else
+	vfree(ns->mem.byte);
+#endif
+
+	return;
+}
+
+/*
+ * Returns the string representation of 'state' state.
+ */
+static char *
+get_state_name(uint32_t state)
+{
+	switch (NS_STATE(state)) {
+		case STATE_CMD_READ0:
+			return "STATE_CMD_READ0";
+		case STATE_CMD_READ1:
+			return "STATE_CMD_READ1";
+		case STATE_CMD_PAGEPROG:
+			return "STATE_CMD_PAGEPROG";
+		case STATE_CMD_READOOB:
+			return "STATE_CMD_READOOB";
+		case STATE_CMD_READ2LP:
+			return "STATE_CMD_READ2LP";
+		case STATE_CMD_ERASE1:
+			return "STATE_CMD_ERASE1";
+		case STATE_CMD_STATUS:
+			return "STATE_CMD_STATUS";
+		case STATE_CMD_STATUS_M:
+			return "STATE_CMD_STATUS_M";
+		case STATE_CMD_SEQIN:
+			return "STATE_CMD_SEQIN";
+		case STATE_CMD_READID:
+			return "STATE_CMD_READID";
+		case STATE_CMD_ERASE2:
+			return "STATE_CMD_ERASE2";
+		case STATE_CMD_RESET:
+			return "STATE_CMD_RESET";
+		case STATE_ADDR_PAGE:
+			return "STATE_ADDR_PAGE";
+		case STATE_ADDR_SEC:
+			return "STATE_ADDR_SEC";
+		case STATE_ADDR_ZERO:
+			return "STATE_ADDR_ZERO";
+		case STATE_DATAIN:
+			return "STATE_DATAIN";
+		case STATE_DATAOUT:
+			return "STATE_DATAOUT";
+		case STATE_DATAOUT_ID:
+			return "STATE_DATAOUT_ID";
+		case STATE_DATAOUT_STATUS:
+			return "STATE_DATAOUT_STATUS";
+		case STATE_DATAOUT_STATUS_M:
+			return "STATE_DATAOUT_STATUS_M";
+		case STATE_READY:
+			return "STATE_READY";
+		case STATE_UNKNOWN:
+			return "STATE_UNKNOWN";
+	}
+
+	NS_ERR("get_state_name: unknown state, BUG\n");
+	return NULL;
+}
+
+/*
+ * Check if command is valid.
+ *
+ * RETURNS: 1 if wrong command, 0 if right.
+ */
+static int
+check_command(int cmd)
+{
+	switch (cmd) {
+		
+	case NAND_CMD_READ0:
+	case NAND_CMD_READ2LP:
+	case NAND_CMD_PAGEPROG:
+	case NAND_CMD_READOOB:
+	case NAND_CMD_ERASE1:
+	case NAND_CMD_STATUS:
+	case NAND_CMD_SEQIN:
+	case NAND_CMD_READID:
+	case NAND_CMD_ERASE2:
+	case NAND_CMD_RESET:
+	case NAND_CMD_READ1:
+		return 0;
+		
+	case NAND_CMD_STATUS_MULTI:
+	default:
+		return 1;
+	}
+}
+
+/*
+ * Returns state after command is accepted by command number.
+ */
+static uint32_t
+get_state_by_command(unsigned command)
+{
+	switch (command) {
+		case NAND_CMD_READ0:
+			return STATE_CMD_READ0;
+		case NAND_CMD_READ1:
+			return STATE_CMD_READ1;
+		case NAND_CMD_PAGEPROG:
+			return STATE_CMD_PAGEPROG;
+		case NAND_CMD_READ2LP:
+			return STATE_CMD_READ2LP;
+		case NAND_CMD_READOOB:
+			return STATE_CMD_READOOB;
+		case NAND_CMD_ERASE1:
+			return STATE_CMD_ERASE1;
+		case NAND_CMD_STATUS:
+			return STATE_CMD_STATUS;
+		case NAND_CMD_STATUS_MULTI:
+			return STATE_CMD_STATUS_M;
+		case NAND_CMD_SEQIN:
+			return STATE_CMD_SEQIN;
+		case NAND_CMD_READID:
+			return STATE_CMD_READID;
+		case NAND_CMD_ERASE2:
+			return STATE_CMD_ERASE2;
+		case NAND_CMD_RESET:
+			return STATE_CMD_RESET;
+	}
+
+	NS_ERR("get_state_by_command: unknown command, BUG\n");
+	return 0;
+}
+
+/*
+ * Move an address byte to the correspondent internal register.
+ */
+static inline void
+accept_addr_byte(struct nandsim *ns, u_char bt)
+{
+	uint byte = (uint)bt;
+	
+	if (ns->regs.count < (ns->geom.pgaddrbytes - ns->geom.secaddrbytes))
+		ns->regs.column |= (byte << 8 * ns->regs.count);
+	else {
+		ns->regs.row |= (byte << 8 * (ns->regs.count -
+						ns->geom.pgaddrbytes +
+						ns->geom.secaddrbytes));
+	}
+
+	return;
+}
+		
+/*
+ * Switch to STATE_READY state.
+ */
+static inline void 
+switch_to_ready_state(struct nandsim *ns, u_char status)
+{
+	NS_DBG("switch_to_ready_state: switch to %s state\n", get_state_name(STATE_READY));
+
+	ns->state       = STATE_READY;
+	ns->nxstate     = STATE_UNKNOWN;
+	ns->op          = NULL;
+	ns->npstates    = 0;
+	ns->stateidx    = 0;
+	ns->regs.num    = 0;
+	ns->regs.count  = 0;
+	ns->regs.off    = 0;
+	ns->regs.row    = 0;
+	ns->regs.column = 0;
+	ns->regs.status = status;
+}
+
+/*
+ * If the operation isn't known yet, try to find it in the global array
+ * of supported operations.
+ *
+ * Operation can be unknown because of the following.
+ *   1. New command was accepted and this is the firs call to find the
+ *      correspondent states chain. In this case ns->npstates = 0;
+ *   2. There is several operations which begin with the same command(s)
+ *      (for example program from the second half and read from the
+ *      second half operations both begin with the READ1 command). In this
+ *      case the ns->pstates[] array contains previous states.
+ * 
+ * Thus, the function tries to find operation containing the following
+ * states (if the 'flag' parameter is 0):
+ *    ns->pstates[0], ... ns->pstates[ns->npstates], ns->state
+ *
+ * If (one and only one) matching operation is found, it is accepted (
+ * ns->ops, ns->state, ns->nxstate are initialized, ns->npstate is
+ * zeroed).
+ * 
+ * If there are several maches, the current state is pushed to the
+ * ns->pstates.
+ *
+ * The operation can be unknown only while commands are input to the chip.
+ * As soon as address command is accepted, the operation must be known.
+ * In such situation the function is called with 'flag' != 0, and the
+ * operation is searched using the following pattern:
+ *     ns->pstates[0], ... ns->pstates[ns->npstates], <address input>
+ * 
+ * It is supposed that this pattern must either match one operation on
+ * none. There can't be ambiguity in that case.
+ *
+ * If no matches found, the functions does the following:
+ *   1. if there are saved states present, try to ignore them and search
+ *      again only using the last command. If nothing was found, switch
+ *      to the STATE_READY state.
+ *   2. if there are no saved states, switch to the STATE_READY state.
+ *
+ * RETURNS: -2 - no matched operations found.
+ *          -1 - several matches.
+ *           0 - operation is found.
+ */
+static int
+find_operation(struct nandsim *ns, uint32_t flag)
+{
+	int opsfound = 0;
+	int i, j, idx = 0;
+	
+	for (i = 0; i < NS_OPER_NUM; i++) {
+
+		int found = 1;
+	
+		if (!(ns->options & ops[i].reqopts))
+			/* Ignore operations we can't perform */
+			continue;
+			
+		if (flag) {
+			if (!(ops[i].states[ns->npstates] & STATE_ADDR_MASK))
+				continue;
+		} else {
+			if (NS_STATE(ns->state) != NS_STATE(ops[i].states[ns->npstates]))
+				continue;
+		}
+
+		for (j = 0; j < ns->npstates; j++) 
+			if (NS_STATE(ops[i].states[j]) != NS_STATE(ns->pstates[j])
+				&& (ns->options & ops[idx].reqopts)) {
+				found = 0;
+				break;
+			}
+
+		if (found) {
+			idx = i;
+			opsfound += 1;
+		}
+	}
+
+	if (opsfound == 1) {
+		/* Exact match */
+		ns->op = &ops[idx].states[0];
+		if (flag) {
+			/* 
+			 * In this case the find_operation function was
+			 * called when address has just began input. But it isn't
+			 * yet fully input and the current state must
+			 * not be one of STATE_ADDR_*, but the STATE_ADDR_*
+			 * state must be the next state (ns->nxstate).
+			 */
+			ns->stateidx = ns->npstates - 1;
+		} else {
+			ns->stateidx = ns->npstates;
+		}
+		ns->npstates = 0;
+		ns->state = ns->op[ns->stateidx];
+		ns->nxstate = ns->op[ns->stateidx + 1];
+		NS_DBG("find_operation: operation found, index: %d, state: %s, nxstate %s\n",
+				idx, get_state_name(ns->state), get_state_name(ns->nxstate));
+		return 0;
+	}
+	
+	if (opsfound == 0) {
+		/* Nothing was found. Try to ignore previous commands (if any) and search again */
+		if (ns->npstates != 0) {
+			NS_DBG("find_operation: no operation found, try again with state %s\n",
+					get_state_name(ns->state));
+			ns->npstates = 0;
+			return find_operation(ns, 0);
+
+		}
+		NS_DBG("find_operation: no operations found\n");
+		switch_to_ready_state(ns, NS_STATUS_FAILED(ns));
+		return -2;
+	}
+	
+	if (flag) {
+		/* This shouldn't happen */
+		NS_DBG("find_operation: BUG, operation must be known if address is input\n");
+		return -2;
+	}
+	
+	NS_DBG("find_operation: there is still ambiguity\n");
+
+	ns->pstates[ns->npstates++] = ns->state;
+
+	return -1;
+}
+
+/*
+ * If state has any action bit, perform this action.
+ *
+ * RETURNS: 0 if success, -1 if error.
+ */
+static int
+do_state_action(struct nandsim *ns, uint32_t action)
+{
+	int i, num;
+	int busdiv = ns->busw == 8 ? 1 : 2;
+
+	action &= ACTION_MASK;
+	
+	/* Check that page address input is correct */
+	if (action != ACTION_SECERASE && ns->regs.row >= ns->geom.pgnum) {
+		NS_WARN("do_state_action: wrong page number (%#x)\n", ns->regs.row);
+		return -1;
+	}
+
+	switch (action) {
+
+	case ACTION_CPY:
+		/*
+		 * Copy page data to the internal buffer.
+		 */
+
+		/* Column shouldn't be very large */
+		if (ns->regs.column >= (ns->geom.pgszoob - ns->regs.off)) {
+			NS_ERR("do_state_action: column number is too large\n");
+			break;
+		}
+		num = ns->geom.pgszoob - ns->regs.off - ns->regs.column;
+		memcpy(ns->buf.byte, ns->mem.byte + NS_RAW_OFFSET(ns) + ns->regs.off, num);
+
+		NS_DBG("do_state_action: (ACTION_CPY:) copy %d bytes to int buf, raw offset %d\n",
+			num, NS_RAW_OFFSET(ns) + ns->regs.off);
+		
+		if (ns->regs.off == 0)
+			NS_LOG("read page %d\n", ns->regs.row);
+		else if (ns->regs.off < ns->geom.pgsz)
+			NS_LOG("read page %d (second half)\n", ns->regs.row);
+		else
+			NS_LOG("read OOB of page %d\n", ns->regs.row);
+		
+		NS_UDELAY(access_delay);
+		NS_UDELAY(input_cycle * ns->geom.pgsz / 1000 / busdiv);
+
+		break;
+
+	case ACTION_SECERASE:
+		/*
+		 * Erase sector.
+		 */
+		
+		if (ns->lines.wp) {
+			NS_ERR("do_state_action: device is write-protected, ignore sector erase\n");
+			return -1;
+		}
+		
+		if (ns->regs.row >= ns->geom.pgnum - ns->geom.pgsec
+			|| (ns->regs.row & ~(ns->geom.secsz - 1))) {
+			NS_ERR("do_state_action: wrong sector address (%#x)\n", ns->regs.row);
+			return -1;
+		}
+		
+		ns->regs.row = (ns->regs.row <<
+				8 * (ns->geom.pgaddrbytes - ns->geom.secaddrbytes)) | ns->regs.column;
+		ns->regs.column = 0;
+		
+		NS_DBG("do_state_action: erase sector at address %#x, off = %d\n",
+				ns->regs.row, NS_RAW_OFFSET(ns));
+		NS_LOG("erase sector %d\n", ns->regs.row >> (ns->geom.secshift - ns->geom.pgshift));
+
+		memset(ns->mem.byte + NS_RAW_OFFSET(ns), 0xFF, ns->geom.secszoob);
+		
+		NS_MDELAY(erase_delay);
+		
+		break;
+
+	case ACTION_PRGPAGE:
+		/*
+		 * Programm page - move internal buffer data to the page.
+		 */
+
+		if (ns->lines.wp) {
+			NS_WARN("do_state_action: device is write-protected, programm\n");
+			return -1;
+		}
+
+		num = ns->geom.pgszoob - ns->regs.off - ns->regs.column;
+		if (num != ns->regs.count) {
+			NS_ERR("do_state_action: too few bytes were input (%d instead of %d)\n",
+					ns->regs.count, num);
+			return -1;
+		}
+
+		for (i = 0; i < num; i++)
+			ns->mem.byte[NS_RAW_OFFSET(ns) + ns->regs.off + i] &= ns->buf.byte[i];
+
+		NS_DBG("do_state_action: copy %d bytes from int buf to (%#x, %#x), raw off = %d\n",
+			num, ns->regs.row, ns->regs.column, NS_RAW_OFFSET(ns) + ns->regs.off);
+		NS_LOG("programm page %d\n", ns->regs.row);
+		
+		NS_UDELAY(programm_delay);
+		NS_UDELAY(output_cycle * ns->geom.pgsz / 1000 / busdiv);
+		
+		break;
+	
+	case ACTION_ZEROOFF:
+		NS_DBG("do_state_action: set internal offset to 0\n");
+		ns->regs.off = 0;
+		break;
+
+	case ACTION_HALFOFF:
+		if (!(ns->options & OPT_PAGE512_8BIT)) {
+			NS_ERR("do_state_action: BUG! can't skip half of page for non-512"
+				"byte page size 8x chips\n");
+			return -1;
+		}
+		NS_DBG("do_state_action: set internal offset to %d\n", ns->geom.pgsz/2);
+		ns->regs.off = ns->geom.pgsz/2;
+		break;
+
+	case ACTION_OOBOFF:
+		NS_DBG("do_state_action: set internal offset to %d\n", ns->geom.pgsz);
+		ns->regs.off = ns->geom.pgsz;
+		break;
+		
+	default:
+		NS_DBG("do_state_action: BUG! unknown action\n");
+	}
+
+	return 0;
+}
+
+/*
+ * Switch simulator's state.
+ */
+static void
+switch_state(struct nandsim *ns)
+{
+	if (ns->op) {
+		/*
+		 * The current operation have already been identified.
+		 * Just follow the states chain.
+		 */
+		
+		ns->stateidx += 1;
+		ns->state = ns->nxstate;
+		ns->nxstate = ns->op[ns->stateidx + 1];
+
+		NS_DBG("switch_state: operation is known, switch to the next state, "
+			"state: %s, nxstate: %s\n",
+			get_state_name(ns->state), get_state_name(ns->nxstate));
+
+		/* See, whether we need to do some action */
+		if ((ns->state & ACTION_MASK) && do_state_action(ns, ns->state) < 0) {
+			switch_to_ready_state(ns, NS_STATUS_FAILED(ns));
+			return;
+		}
+		
+	} else {
+		/*
+		 * We don't yet know which operation we perform.
+		 * Try to identify it.
+		 */
+
+		/*  
+		 *  The only event causing the switch_state function to
+		 *  be called with yet unknown operation is new command.
+		 */
+		ns->state = get_state_by_command(ns->regs.command);
+
+		NS_DBG("switch_state: operation is unknown, try to find it\n");
+
+		if (find_operation(ns, 0) != 0)
+			return;
+
+		if ((ns->state & ACTION_MASK) && do_state_action(ns, ns->state) < 0) {
+			switch_to_ready_state(ns, NS_STATUS_FAILED(ns));
+			return;
+		}
+	}
+
+	/* For 16x devices column means the page offset in words */
+	if ((ns->nxstate & STATE_ADDR_MASK) && ns->busw == 16) {
+		NS_DBG("switch_state: double the column number for 16x device\n");
+		ns->regs.column <<= 1;
+	}
+
+	if (NS_STATE(ns->nxstate) == STATE_READY) {
+		/*
+		 * The current state is the last. Return to STATE_READY
+		 */
+
+		u_char status = NS_STATUS_OK(ns);
+		
+		/* In case of data states, see if all bytes were input/output */
+		if ((ns->state & (STATE_DATAIN_MASK | STATE_DATAOUT_MASK))
+			&& ns->regs.count != ns->regs.num) {
+			NS_WARN("switch_state: not all bytes were processed, %d left\n",
+					ns->regs.num - ns->regs.count);
+			status = NS_STATUS_FAILED(ns);
+		}
+				
+		NS_DBG("switch_state: operation complete, switch to STATE_READY state\n");
+
+		switch_to_ready_state(ns, status);
+
+		return;
+	} else if (ns->nxstate & (STATE_DATAIN_MASK | STATE_DATAOUT_MASK)) {
+		/* 
+		 * If the next state is data input/output, switch to it now
+		 */
+		
+		ns->state      = ns->nxstate;
+		ns->nxstate    = ns->op[++ns->stateidx + 1];
+		ns->regs.num   = ns->regs.count = 0;
+
+		NS_DBG("switch_state: the next state is data I/O, switch, "
+			"state: %s, nxstate: %s\n",
+			get_state_name(ns->state), get_state_name(ns->nxstate));
+
+		/*
+		 * Set the internal register to the count of bytes which
+		 * are expected to be input or output
+		 */
+		switch (NS_STATE(ns->state)) {
+			case STATE_DATAIN:
+			case STATE_DATAOUT:
+				ns->regs.num = ns->geom.pgszoob - ns->regs.off - ns->regs.column;
+				break;
+				
+			case STATE_DATAOUT_ID:
+				ns->regs.num = ns->geom.idbytes;
+				break;
+				
+			case STATE_DATAOUT_STATUS:
+			case STATE_DATAOUT_STATUS_M:
+				ns->regs.count = ns->regs.num = 0;
+				break;
+				
+			default:
+				NS_ERR("switch_state: BUG! unknown data state\n");
+		}
+
+	} else if (ns->nxstate & STATE_ADDR_MASK) {
+		/*
+		 * If the next state is address input, set the internal
+		 * register to the number of expected address bytes
+		 */
+
+		ns->regs.count = 0;
+		
+		switch (NS_STATE(ns->nxstate)) {
+			case STATE_ADDR_PAGE:
+				ns->regs.num = ns->geom.pgaddrbytes;
+		
+				break;
+			case STATE_ADDR_SEC:
+				ns->regs.num = ns->geom.secaddrbytes;
+				break;
+	
+			case STATE_ADDR_ZERO:
+				ns->regs.num = 1;
+				break;
+
+			default:
+				NS_ERR("switch_state: BUG! unknown address state\n");
+		}
+	} else {
+		/* 
+		 * Just reset internal counters.
+		 */
+
+		ns->regs.num = 0;
+		ns->regs.count = 0;
+	}
+}
+
+static void
+ns_hwcontrol(struct mtd_info *mtd, int cmd)
+{
+	struct nandsim *ns = (struct nandsim *)((struct nand_chip *)mtd->priv)->priv;
+
+	switch (cmd) {
+
+	/* set CLE line high */
+	case NAND_CTL_SETCLE:
+		NS_DBG("ns_hwcontrol: start command latch cycles\n");
+		ns->lines.cle  = 1;
+		break;
+
+	/* set CLE line low */
+	case NAND_CTL_CLRCLE:
+		NS_DBG("ns_hwcontrol: stop command latch cycles\n");
+		ns->lines.cle  = 0;
+		break;
+
+	/* set ALE line high */
+	case NAND_CTL_SETALE:
+		NS_DBG("ns_hwcontrol: start address latch cycles\n");
+		ns->lines.ale   = 1;
+		break;
+
+	/* set ALE line low */
+	case NAND_CTL_CLRALE:
+		NS_DBG("ns_hwcontrol: stop address latch cycles\n");
+		ns->lines.ale  = 0;
+		break;
+
+	/* set WP line high */
+	case NAND_CTL_SETWP:
+		NS_DBG("ns_hwcontrol: enable write protection\n");
+		ns->lines.wp = 1;
+		break;
+
+	/* set WP line low */
+	case NAND_CTL_CLRWP:
+		NS_DBG("ns_hwcontrol: disable write protection\n");
+		ns->lines.wp = 0;
+		break;
+
+	/* set CE line low */
+	case NAND_CTL_SETNCE:
+		NS_DBG("ns_hwcontrol: enable chip\n");
+		ns->lines.ce = 1;
+		break;
+
+	/* set CE line high */
+	case NAND_CTL_CLRNCE:
+		NS_DBG("ns_hwcontrol: disable chip\n");
+		ns->lines.ce = 0;
+		break;
+
+	default:
+		NS_ERR("hwcontrol: unknown command\n");
+        }
+
+	return;
+}
+
+static u_char
+ns_nand_read_byte(struct mtd_info *mtd)
+{
+        struct nandsim *ns = (struct nandsim *)((struct nand_chip *)mtd->priv)->priv;
+	u_char outb = 0x00;
+
+	/* Sanity and correctness checks */
+	if (!ns->lines.ce) {
+		NS_ERR("read_byte: chip is disabled, return %#x\n", (uint)outb);
+		return outb;
+	}
+	if (ns->lines.ale || ns->lines.cle) {
+		NS_ERR("read_byte: ALE or CLE pin is high, return %#x\n", (uint)outb);
+		return outb;
+	}
+	if (!(ns->state & STATE_DATAOUT_MASK)) {
+		NS_WARN("read_byte: unexpected data output cycle, state is %s "
+			"return %#x\n", get_state_name(ns->state), (uint)outb);
+		return outb;
+	}
+
+	/* Status register may be read as many times as it is wanted */
+	if (NS_STATE(ns->state) == STATE_DATAOUT_STATUS) {
+		NS_DBG("read_byte: return %#x status\n", ns->regs.status);
+		return ns->regs.status;
+	}
+
+	/* Check if there is any data in the internal buffer which may be read */
+	if (ns->regs.count == ns->regs.num) {
+		NS_WARN("read_byte: no more data to output, return %#x\n", (uint)outb);
+		return outb;
+	}
+
+	switch (NS_STATE(ns->state)) {
+		case STATE_DATAOUT:
+			if (ns->busw == 8) {
+				outb = ns->buf.byte[ns->regs.count];
+				ns->regs.count += 1;
+			} else {
+				outb = (u_char)cpu_to_le16(ns->buf.word[ns->regs.count >> 1]);
+				ns->regs.count += 2;
+			}
+			break;
+		case STATE_DATAOUT_ID:
+			NS_DBG("read_byte: read ID byte %d, total = %d\n", ns->regs.count, ns->regs.num);
+			outb = ns->ids[ns->regs.count];
+			ns->regs.count += 1;
+			break;
+		default:
+			BUG();
+	}
+	
+	if (ns->regs.count == ns->regs.num) {
+		NS_DBG("read_byte: all bytes were read\n");
+
+		/*
+		 * The OPT_AUTOINCR allows to read next conseqitive pages without
+		 * new read operation cycle.
+		 */
+		if ((ns->options & OPT_AUTOINCR) && NS_STATE(ns->state) == STATE_DATAOUT) {
+			ns->regs.count = 0;
+			if (ns->regs.row + 1 < ns->geom.pgnum)
+				ns->regs.row += 1;
+			NS_DBG("read_byte: switch to the next page (%#x)\n", ns->regs.row);
+			do_state_action(ns, ACTION_CPY);
+		}
+		else if (NS_STATE(ns->nxstate) == STATE_READY)
+			switch_state(ns);
+		
+	}
+	
+	return outb;
+}
+
+static void
+ns_nand_write_byte(struct mtd_info *mtd, u_char byte)
+{
+        struct nandsim *ns = (struct nandsim *)((struct nand_chip *)mtd->priv)->priv;
+	
+	/* Sanity and correctness checks */
+	if (!ns->lines.ce) {
+		NS_ERR("write_byte: chip is disabled, ignore write\n");
+		return;
+	}
+	if (ns->lines.ale && ns->lines.cle) {
+		NS_ERR("write_byte: ALE and CLE pins are high simultaneously, ignore write\n");
+		return;
+	}
+			
+	if (ns->lines.cle == 1) {
+		/*
+		 * The byte written is a command.
+		 */
+
+		if (byte == NAND_CMD_RESET) {
+			NS_LOG("reset chip\n");
+			switch_to_ready_state(ns, NS_STATUS_OK(ns));
+			return;
+		}
+
+		/* 
+		 * Chip might still be in STATE_DATAOUT
+		 * (if OPT_AUTOINCR feature is supported), STATE_DATAOUT_STATUS or
+		 * STATE_DATAOUT_STATUS_M state. If so, switch state.
+		 */
+		if (NS_STATE(ns->state) == STATE_DATAOUT_STATUS
+			|| NS_STATE(ns->state) == STATE_DATAOUT_STATUS_M
+			|| ((ns->options & OPT_AUTOINCR) && NS_STATE(ns->state) == STATE_DATAOUT))
+			switch_state(ns);
+
+		/* Check if chip is expecting command */
+		if (NS_STATE(ns->nxstate) != STATE_UNKNOWN && !(ns->nxstate & STATE_CMD_MASK)) {
+			/*
+			 * We are in situation when something else (not command)
+			 * was expected but command was input. In this case ignore
+			 * previous command(s)/state(s) and accept the last one.
+			 */
+			NS_WARN("write_byte: command (%#x) wasn't expected, expected state is %s, "
+				"ignore previous states\n", (uint)byte, get_state_name(ns->nxstate));
+			switch_to_ready_state(ns, NS_STATUS_FAILED(ns));
+		}
+		
+		/* Check that the command byte is correct */
+		if (check_command(byte)) {
+			NS_ERR("write_byte: unknown command %#x\n", (uint)byte);
+			return;
+		}
+		
+		NS_DBG("command byte corresponding to %s state accepted\n",
+			get_state_name(get_state_by_command(byte)));
+		ns->regs.command = byte;
+		switch_state(ns);
+
+	} else if (ns->lines.ale == 1) {
+		/*
+		 * The byte written is an address.
+		 */
+
+		if (NS_STATE(ns->nxstate) == STATE_UNKNOWN) {
+
+			NS_DBG("write_byte: operation isn't known yet, identify it\n");
+
+			if (find_operation(ns, 1) < 0)
+				return;
+			
+			if ((ns->state & ACTION_MASK) && do_state_action(ns, ns->state) < 0) {
+				switch_to_ready_state(ns, NS_STATUS_FAILED(ns));
+				return;
+			}
+				
+			ns->regs.count = 0;
+			switch (NS_STATE(ns->nxstate)) {
+				case STATE_ADDR_PAGE:
+					ns->regs.num = ns->geom.pgaddrbytes;
+					break;
+				case STATE_ADDR_SEC:
+					ns->regs.num = ns->geom.secaddrbytes;
+					break;
+				case STATE_ADDR_ZERO:
+					ns->regs.num = 1;
+					break;
+				default:
+					BUG();
+			}
+		}
+
+		/* Check that chip is expecting address */
+		if (!(ns->nxstate & STATE_ADDR_MASK)) {
+			NS_ERR("write_byte: address (%#x) isn't expected, expected state is %s, "
+				"switch to STATE_READY\n", (uint)byte, get_state_name(ns->nxstate));
+			switch_to_ready_state(ns, NS_STATUS_FAILED(ns));
+			return;
+		}
+		
+		/* Check if this is expected byte */
+		if (ns->regs.count == ns->regs.num) {
+			NS_ERR("write_byte: no more address bytes expected\n");
+			switch_to_ready_state(ns, NS_STATUS_FAILED(ns));
+			return;
+		}
+
+		accept_addr_byte(ns, byte);
+
+		ns->regs.count += 1;
+
+		NS_DBG("write_byte: address byte %#x was accepted (%d bytes input, %d expected)\n",
+				(uint)byte, ns->regs.count, ns->regs.num);
+
+		if (ns->regs.count == ns->regs.num) {
+			NS_DBG("address (%#x, %#x) is accepted\n", ns->regs.row, ns->regs.column);
+			switch_state(ns);
+		}
+		
+	} else {
+		/*
+		 * The byte written is an input data.
+		 */
+		
+		/* Check that chip is expecting data input */
+		if (!(ns->state & STATE_DATAIN_MASK)) {
+			NS_ERR("write_byte: data input (%#x) isn't expected, state is %s, "
+				"switch to %s\n", (uint)byte,
+				get_state_name(ns->state), get_state_name(STATE_READY));
+			switch_to_ready_state(ns, NS_STATUS_FAILED(ns));
+			return;
+		}
+
+		/* Check if this is expected byte */
+		if (ns->regs.count == ns->regs.num) {
+			NS_WARN("write_byte: %u input bytes has already been accepted, ignore write\n",
+					ns->regs.num);
+			return;
+		}
+
+		if (ns->busw == 8) {
+			ns->buf.byte[ns->regs.count] = byte;
+			ns->regs.count += 1;
+		} else {
+			ns->buf.word[ns->regs.count >> 1] = cpu_to_le16((uint16_t)byte);
+			ns->regs.count += 2;
+		}
+	}
+
+	return;
+}
+
+static int
+ns_device_ready(struct mtd_info *mtd)
+{
+	NS_DBG("device_ready\n");
+	return 1;
+}
+
+static uint16_t
+ns_nand_read_word(struct mtd_info *mtd)
+{
+	struct nand_chip *chip = (struct nand_chip *)mtd->priv;
+
+	NS_DBG("read_word\n");
+	
+	return chip->read_byte(mtd) | (chip->read_byte(mtd) << 8);
+}
+
+static void
+ns_nand_write_word(struct mtd_info *mtd, uint16_t word)
+{
+	struct nand_chip *chip = (struct nand_chip *)mtd->priv;
+	
+	NS_DBG("write_word\n");
+	
+	chip->write_byte(mtd, word & 0xFF);
+	chip->write_byte(mtd, word >> 8);
+}
+
+static void 
+ns_nand_write_buf(struct mtd_info *mtd, const u_char *buf, int len)
+{
+        struct nandsim *ns = (struct nandsim *)((struct nand_chip *)mtd->priv)->priv;
+
+	/* Check that chip is expecting data input */
+	if (!(ns->state & STATE_DATAIN_MASK)) {
+		NS_ERR("write_buf: data input isn't expected, state is %s, "
+			"switch to STATE_READY\n", get_state_name(ns->state));
+		switch_to_ready_state(ns, NS_STATUS_FAILED(ns));
+		return;
+	}
+
+	/* Check if these are expected bytes */
+	if (ns->regs.count + len > ns->regs.num) {
+		NS_ERR("write_buf: too many input bytes\n");
+		switch_to_ready_state(ns, NS_STATUS_FAILED(ns));
+		return;
+	}
+
+	memcpy(ns->buf.byte + ns->regs.count, buf, len);
+	ns->regs.count += len;
+	
+	if (ns->regs.count == ns->regs.num) {
+		NS_DBG("write_buf: %d bytes were written\n", ns->regs.count);
+	}
+}
+
+static void 
+ns_nand_read_buf(struct mtd_info *mtd, u_char *buf, int len)
+{
+        struct nandsim *ns = (struct nandsim *)((struct nand_chip *)mtd->priv)->priv;
+
+	/* Sanity and correctness checks */
+	if (!ns->lines.ce) {
+		NS_ERR("read_buf: chip is disabled\n");
+		return;
+	}
+	if (ns->lines.ale || ns->lines.cle) {
+		NS_ERR("read_buf: ALE or CLE pin is high\n");
+		return;
+	}
+	if (!(ns->state & STATE_DATAOUT_MASK)) {
+		NS_WARN("read_buf: unexpected data output cycle, current state is %s\n",
+			get_state_name(ns->state));
+		return;
+	}
+
+	if (NS_STATE(ns->state) != STATE_DATAOUT) {
+		int i;
+
+		for (i = 0; i < len; i++)
+			buf[i] = ((struct nand_chip *)mtd->priv)->read_byte(mtd);
+
+		return;
+	}
+
+	/* Check if these are expected bytes */
+	if (ns->regs.count + len > ns->regs.num) {
+		NS_ERR("read_buf: too many bytes to read\n");
+		switch_to_ready_state(ns, NS_STATUS_FAILED(ns));
+		return;
+	}
+
+	memcpy(buf, ns->buf.byte + ns->regs.count, len);
+	ns->regs.count += len;
+	
+	if (ns->regs.count == ns->regs.num) {
+		if ((ns->options & OPT_AUTOINCR) && NS_STATE(ns->state) == STATE_DATAOUT) {
+			ns->regs.count = 0;
+			if (ns->regs.row + 1 < ns->geom.pgnum)
+				ns->regs.row += 1;
+			NS_DBG("read_buf: switch to the next page (%#x)\n", ns->regs.row);
+			do_state_action(ns, ACTION_CPY);
+		}
+		else if (NS_STATE(ns->nxstate) == STATE_READY)
+			switch_state(ns);
+	}
+	
+	return;
+}
+
+static int 
+ns_nand_verify_buf(struct mtd_info *mtd, const u_char *buf, int len)
+{
+	ns_nand_read_buf(mtd, (u_char *)&ns_verify_buf[0], len);
+
+	if (!memcmp(buf, &ns_verify_buf[0], len)) {
+		NS_DBG("verify_buf: the buffer is OK\n");
+		return 0;
+	} else {
+		NS_DBG("verify_buf: the buffer is wrong\n");
+		return -EFAULT;
+	}
+}
+
+/*
+ * Having only NAND chip IDs we call nand_scan which detects NAND flash
+ * parameters and then calls scan_bbt in order to scan/find/build the
+ * NAND flash bad block table. But since at that moment the NAND flash
+ * image isn't allocated in the simulator, errors arise. To avoid this
+ * we redefine the scan_bbt callback and initialize the nandsim structure
+ * before the flash media scanning.
+ */
+int ns_scan_bbt(struct mtd_info *mtd)
+{ 
+	struct nand_chip *chip = (struct nand_chip *)mtd->priv;
+	struct nandsim   *ns   = (struct nandsim *)(chip->priv);
+	int retval;
+
+	if (!NS_IS_INITIALIZED(ns))
+		if ((retval = init_nandsim(mtd)) != 0) {
+			NS_ERR("scan_bbt: can't initialize the nandsim structure\n");
+			return retval;
+		}
+	if ((retval = nand_default_bbt(mtd)) != 0) {
+		free_nandsim(ns);
+		return retval;
+	}
+
+	return 0;
+}
+
+/*
+ * Module initialization function
+ */
+int __init ns_init_module(void)
+{
+	struct nand_chip *chip;
+	struct nandsim *nand;
+	int retval = -ENOMEM;
+
+	if (bus_width != 8 && bus_width != 16) {
+		NS_ERR("wrong bus width (%d), use only 8 or 16\n", bus_width);
+		return -EINVAL;
+	}
+	
+	/* Allocate and initialize mtd_info, nand_chip and nandsim structures */
+	nsmtd = kmalloc(sizeof(struct mtd_info) + sizeof(struct nand_chip)
+				+ sizeof(struct nandsim), GFP_KERNEL);
+	if (!nsmtd) {
+		NS_ERR("unable to allocate core structures.\n");
+		return -ENOMEM;
+	}
+	memset(nsmtd, 0, sizeof(struct mtd_info) + sizeof(struct nand_chip) +
+			sizeof(struct nandsim));
+	chip        = (struct nand_chip *)(nsmtd + 1);
+        nsmtd->priv = (void *)chip;
+	nand        = (struct nandsim *)(chip + 1);
+	chip->priv  = (void *)nand;	
+
+	/*
+	 * Register simulator's callbacks.
+	 */
+	chip->hwcontrol  = ns_hwcontrol;
+	chip->read_byte  = ns_nand_read_byte;
+	chip->dev_ready  = ns_device_ready;
+	chip->scan_bbt   = ns_scan_bbt;
+	chip->write_byte = ns_nand_write_byte;
+	chip->write_buf  = ns_nand_write_buf;
+	chip->read_buf   = ns_nand_read_buf;
+	chip->verify_buf = ns_nand_verify_buf;
+	chip->write_word = ns_nand_write_word;
+	chip->read_word  = ns_nand_read_word;
+	chip->eccmode    = NAND_ECC_SOFT;
+
+	/* 
+	 * Perform minimum nandsim structure initialization to handle
+	 * the initial ID read command correctly 
+	 */
+	if (third_id_byte != 0xFF || fourth_id_byte != 0xFF)
+		nand->geom.idbytes = 4;
+	else
+		nand->geom.idbytes = 2;
+	nand->regs.status = NS_STATUS_OK(nand);
+	nand->nxstate = STATE_UNKNOWN;
+	nand->options |= OPT_PAGE256; /* temporary value */
+	nand->ids[0] = first_id_byte;
+	nand->ids[1] = second_id_byte;
+	nand->ids[2] = third_id_byte;
+	nand->ids[3] = fourth_id_byte;
+	if (bus_width == 16) {
+		nand->busw = 16;
+		chip->options |= NAND_BUSWIDTH_16;
+	}
+
+	if ((retval = nand_scan(nsmtd, 1)) != 0) {
+		NS_ERR("can't register NAND Simulator\n");
+		if (retval > 0)
+			retval = -ENXIO;
+		goto error;
+	}
+
+	/* Register NAND as one big partition */
+	add_mtd_partitions(nsmtd, &nand->part, 1);
+
+        return 0;
+
+error:
+	kfree(nsmtd);
+
+	return retval;
+}
+
+module_init(ns_init_module);
+
+/*
+ * Module clean-up function
+ */
+static void __exit ns_cleanup_module(void)
+{
+	struct nandsim *ns = (struct nandsim *)(((struct nand_chip *)nsmtd->priv)->priv);
+
+	free_nandsim(ns);    /* Free nandsim private resources */
+	nand_release(nsmtd); /* Unregisterd drived */
+	kfree(nsmtd);        /* Free other structures */
+}
+
+module_exit(ns_cleanup_module);
+
+MODULE_LICENSE ("GPL");
+MODULE_AUTHOR ("Artem B. Bityuckiy");
+MODULE_DESCRIPTION ("The NAND flash simulator");
+