text: /*
   * Core registration and callback routines for MTD
   * drivers and users.
   *
   * Copyright © 1999-2010 David Woodhouse <dwmw2@infradead.org>
   * Copyright © 2006      Red Hat UK Limited 
   *
   * 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 of the License, 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., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
   *
   */
  
  #include <linux/module.h>
  #include <linux/kernel.h>
  #include <linux/ptrace.h>
  #include <linux/seq_file.h>
  #include <linux/string.h>
  #include <linux/timer.h>
  #include <linux/major.h>
  #include <linux/fs.h>
  #include <linux/err.h>
  #include <linux/ioctl.h>
  #include <linux/init.h>
  #include <linux/of.h>
  #include <linux/proc_fs.h>
  #include <linux/idr.h>
  #include <linux/backing-dev.h>
  #include <linux/gfp.h>
  #include <linux/slab.h>
  #include <linux/reboot.h>
  #include <linux/leds.h>
  
  #include <linux/mtd/mtd.h>
  #include <linux/mtd/partitions.h>
  
  #include "mtdcore.h"
  
  static struct backing_dev_info *mtd_bdi;
  
  #ifdef CONFIG_PM_SLEEP
  
  static int mtd_cls_suspend(struct device *dev)
  {
  	struct mtd_info *mtd = dev_get_drvdata(dev);
  
  	return mtd ? mtd_suspend(mtd) : 0;
  }
  
  static int mtd_cls_resume(struct device *dev)
  {
  	struct mtd_info *mtd = dev_get_drvdata(dev);
  
  	if (mtd)
  		mtd_resume(mtd);
  	return 0;
  }
  
  static SIMPLE_DEV_PM_OPS(mtd_cls_pm_ops, mtd_cls_suspend, mtd_cls_resume);
  #define MTD_CLS_PM_OPS (&mtd_cls_pm_ops)
  #else
  #define MTD_CLS_PM_OPS NULL
  #endif
  
  static struct class mtd_class = {
  	.name = "mtd",
  	.owner = THIS_MODULE,
  	.pm = MTD_CLS_PM_OPS,
  };
  
  static DEFINE_IDR(mtd_idr);
  
  /* These are exported solely for the purpose of mtd_blkdevs.c. You
     should not use them for _anything_ else */
  DEFINE_MUTEX(mtd_table_mutex);
  EXPORT_SYMBOL_GPL(mtd_table_mutex);
  
  struct mtd_info *__mtd_next_device(int i)
  {
  	return idr_get_next(&mtd_idr, &i);
  }
  EXPORT_SYMBOL_GPL(__mtd_next_device);
  
  static LIST_HEAD(mtd_notifiers);
  
  
  #define MTD_DEVT(index) MKDEV(MTD_CHAR_MAJOR, (index)*2)
  
  /* REVISIT once MTD uses the driver model better, whoever allocates
   * the mtd_info will probably want to use the release() hook...
   */
  static void mtd_release(struct device *dev)
  {
  	struct mtd_info *mtd = dev_get_drvdata(dev);
  	dev_t index = MTD_DEVT(mtd->index);
  
  	/* remove /dev/mtdXro node */
  	device_destroy(&mtd_class, index + 1);
  }
  
  static ssize_t mtd_type_show(struct device *dev,
  		struct device_attribute *attr, char *buf)
  {
  	struct mtd_info *mtd = dev_get_drvdata(dev);
  	char *type;
  
  	switch (mtd->type) {
  	case MTD_ABSENT:
  		type = "absent";
  		break;
  	case MTD_RAM:
  		type = "ram";
  		break;
  	case MTD_ROM:
  		type = "rom";
  		break;
  	case MTD_NORFLASH:
  		type = "nor";
  		break;
  	case MTD_NANDFLASH:
  		type = "nand";
  		break;
  	case MTD_DATAFLASH:
  		type = "dataflash";
  		break;
  	case MTD_UBIVOLUME:
  		type = "ubi";
  		break;
  	case MTD_MLCNANDFLASH:
  		type = "mlc-nand";
  		break;
  	default:
  		type = "unknown";
  	}
  
  	return snprintf(buf, PAGE_SIZE, "%s\n", type);
  }
  static DEVICE_ATTR(type, S_IRUGO, mtd_type_show, NULL);
  
  static ssize_t mtd_flags_show(struct device *dev,
  		struct device_attribute *attr, char *buf)
  {
  	struct mtd_info *mtd = dev_get_drvdata(dev);
  
  	return snprintf(buf, PAGE_SIZE, "0x%lx\n", (unsigned long)mtd->flags);
  
  }
  static DEVICE_ATTR(flags, S_IRUGO, mtd_flags_show, NULL);
  
  static ssize_t mtd_size_show(struct device *dev,
  		struct device_attribute *attr, char *buf)
  {
  	struct mtd_info *mtd = dev_get_drvdata(dev);
  
  	return snprintf(buf, PAGE_SIZE, "%llu\n",
  		(unsigned long long)mtd->size);
  
  }
  static DEVICE_ATTR(size, S_IRUGO, mtd_size_show, NULL);
  
  static ssize_t mtd_erasesize_show(struct device *dev,
  		struct device_attribute *attr, char *buf)
  {
  	struct mtd_info *mtd = dev_get_drvdata(dev);
  
  	return snprintf(buf, PAGE_SIZE, "%lu\n", (unsigned long)mtd->erasesize);
  
  }
  static DEVICE_ATTR(erasesize, S_IRUGO, mtd_erasesize_show, NULL);
  
  static ssize_t mtd_writesize_show(struct device *dev,
  		struct device_attribute *attr, char *buf)
  {
  	struct mtd_info *mtd = dev_get_drvdata(dev);
  
  	return snprintf(buf, PAGE_SIZE, "%lu\n", (unsigned long)mtd->writesize);
  
  }
  static DEVICE_ATTR(writesize, S_IRUGO, mtd_writesize_show, NULL);
  
  static ssize_t mtd_subpagesize_show(struct device *dev,
  		struct device_attribute *attr, char *buf)
  {
  	struct mtd_info *mtd = dev_get_drvdata(dev);
  	unsigned int subpagesize = mtd->writesize >> mtd->subpage_sft;
  
  	return snprintf(buf, PAGE_SIZE, "%u\n", subpagesize);
  
  }
  static DEVICE_ATTR(subpagesize, S_IRUGO, mtd_subpagesize_show, NULL);
  
  static ssize_t mtd_oobsize_show(struct device *dev,
  		struct device_attribute *attr, char *buf)
  {
  	struct mtd_info *mtd = dev_get_drvdata(dev);
  
  	return snprintf(buf, PAGE_SIZE, "%lu\n", (unsigned long)mtd->oobsize);
  
  }
  static DEVICE_ATTR(oobsize, S_IRUGO, mtd_oobsize_show, NULL);
  
  static ssize_t mtd_numeraseregions_show(struct device *dev,
  		struct device_attribute *attr, char *buf)
  {
  	struct mtd_info *mtd = dev_get_drvdata(dev);
  
  	return snprintf(buf, PAGE_SIZE, "%u\n", mtd->numeraseregions);
  
  }
  static DEVICE_ATTR(numeraseregions, S_IRUGO, mtd_numeraseregions_show,
  	NULL);
  
  static ssize_t mtd_name_show(struct device *dev,
  		struct device_attribute *attr, char *buf)
  {
  	struct mtd_info *mtd = dev_get_drvdata(dev);
  
  	return snprintf(buf, PAGE_SIZE, "%s\n", mtd->name);
  
  }
  static DEVICE_ATTR(name, S_IRUGO, mtd_name_show, NULL);
  
  static ssize_t mtd_ecc_strength_show(struct device *dev,
  				     struct device_attribute *attr, char *buf)
  {
  	struct mtd_info *mtd = dev_get_drvdata(dev);
  
  	return snprintf(buf, PAGE_SIZE, "%u\n", mtd->ecc_strength);
  }
  static DEVICE_ATTR(ecc_strength, S_IRUGO, mtd_ecc_strength_show, NULL);
  
  static ssize_t mtd_bitflip_threshold_show(struct device *dev,
  					  struct device_attribute *attr,
  					  char *buf)
  {
  	struct mtd_info *mtd = dev_get_drvdata(dev);
  
  	return snprintf(buf, PAGE_SIZE, "%u\n", mtd->bitflip_threshold);
  }
  
  static ssize_t mtd_bitflip_threshold_store(struct device *dev,
  					   struct device_attribute *attr,
  					   const char *buf, size_t count)
  {
  	struct mtd_info *mtd = dev_get_drvdata(dev);
  	unsigned int bitflip_threshold;
  	int retval;
  
  	retval = kstrtouint(buf, 0, &bitflip_threshold);
  	if (retval)
  		return retval;
  
  	mtd->bitflip_threshold = bitflip_threshold;
  	return count;
  }
  static DEVICE_ATTR(bitflip_threshold, S_IRUGO | S_IWUSR,
  		   mtd_bitflip_threshold_show,
  		   mtd_bitflip_threshold_store);
  
  static ssize_t mtd_ecc_step_size_show(struct device *dev,
  		struct device_attribute *attr, char *buf)
  {
  	struct mtd_info *mtd = dev_get_drvdata(dev);
  
  	return snprintf(buf, PAGE_SIZE, "%u\n", mtd->ecc_step_size);
  
  }
  static DEVICE_ATTR(ecc_step_size, S_IRUGO, mtd_ecc_step_size_show, NULL);
  
  static ssize_t mtd_ecc_stats_corrected_show(struct device *dev,
  		struct device_attribute *attr, char *buf)
  {
  	struct mtd_info *mtd = dev_get_drvdata(dev);
  	struct mtd_ecc_stats *ecc_stats = &mtd->ecc_stats;
  
  	return snprintf(buf, PAGE_SIZE, "%u\n", ecc_stats->corrected);
  }
  static DEVICE_ATTR(corrected_bits, S_IRUGO,
  		   mtd_ecc_stats_corrected_show, NULL);
  
  static ssize_t mtd_ecc_stats_errors_show(struct device *dev,
  		struct device_attribute *attr, char *buf)
  {
  	struct mtd_info *mtd = dev_get_drvdata(dev);
  	struct mtd_ecc_stats *ecc_stats = &mtd->ecc_stats;
  
  	return snprintf(buf, PAGE_SIZE, "%u\n", ecc_stats->failed);
  }
  static DEVICE_ATTR(ecc_failures, S_IRUGO, mtd_ecc_stats_errors_show, NULL);
  
  static ssize_t mtd_badblocks_show(struct device *dev,
  		struct device_attribute *attr, char *buf)
  {
  	struct mtd_info *mtd = dev_get_drvdata(dev);
  	struct mtd_ecc_stats *ecc_stats = &mtd->ecc_stats;
  
  	return snprintf(buf, PAGE_SIZE, "%u\n", ecc_stats->badblocks);
  }
  static DEVICE_ATTR(bad_blocks, S_IRUGO, mtd_badblocks_show, NULL);
  
  static ssize_t mtd_bbtblocks_show(struct device *dev,
  		struct device_attribute *attr, char *buf)
  {
  	struct mtd_info *mtd = dev_get_drvdata(dev);
  	struct mtd_ecc_stats *ecc_stats = &mtd->ecc_stats;
  
  	return snprintf(buf, PAGE_SIZE, "%u\n", ecc_stats->bbtblocks);
  }
  static DEVICE_ATTR(bbt_blocks, S_IRUGO, mtd_bbtblocks_show, NULL);
  
  static struct attribute *mtd_attrs[] = {
  	&dev_attr_type.attr,
  	&dev_attr_flags.attr,
  	&dev_attr_size.attr,
  	&dev_attr_erasesize.attr,
  	&dev_attr_writesize.attr,
  	&dev_attr_subpagesize.attr,
  	&dev_attr_oobsize.attr,
  	&dev_attr_numeraseregions.attr,
  	&dev_attr_name.attr,
  	&dev_attr_ecc_strength.attr,
  	&dev_attr_ecc_step_size.attr,
  	&dev_attr_corrected_bits.attr,
  	&dev_attr_ecc_failures.attr,
  	&dev_attr_bad_blocks.attr,
  	&dev_attr_bbt_blocks.attr,
  	&dev_attr_bitflip_threshold.attr,
  	NULL,
  };
  ATTRIBUTE_GROUPS(mtd);
  
  static struct device_type mtd_devtype = {
  	.name		= "mtd",
  	.groups		= mtd_groups,
  	.release	= mtd_release,
  };
  
  #ifndef CONFIG_MMU
  unsigned mtd_mmap_capabilities(struct mtd_info *mtd)
  {
  	switch (mtd->type) {
  	case MTD_RAM:
  		return NOMMU_MAP_COPY | NOMMU_MAP_DIRECT | NOMMU_MAP_EXEC |
  			NOMMU_MAP_READ | NOMMU_MAP_WRITE;
  	case MTD_ROM:
  		return NOMMU_MAP_COPY | NOMMU_MAP_DIRECT | NOMMU_MAP_EXEC |
  			NOMMU_MAP_READ;
  	default:
  		return NOMMU_MAP_COPY;
  	}
  }
  EXPORT_SYMBOL_GPL(mtd_mmap_capabilities);
  #endif
  
  static int mtd_reboot_notifier(struct notifier_block *n, unsigned long state,
  			       void *cmd)
  {
  	struct mtd_info *mtd;
  
  	mtd = container_of(n, struct mtd_info, reboot_notifier);
  	mtd->_reboot(mtd);
  
  	return NOTIFY_DONE;
  }
  
  /**
   * mtd_wunit_to_pairing_info - get pairing information of a wunit
   * @mtd: pointer to new MTD device info structure
   * @wunit: write unit we are interested in
   * @info: returned pairing information
   *
   * Retrieve pairing information associated to the wunit.
   * This is mainly useful when dealing with MLC/TLC NANDs where pages can be
   * paired together, and where programming a page may influence the page it is
   * paired with.
   * The notion of page is replaced by the term wunit (write-unit) to stay
   * consistent with the ->writesize field.
   *
   * The @wunit argument can be extracted from an absolute offset using
   * mtd_offset_to_wunit(). @info is filled with the pairing information attached
   * to @wunit.
   *
   * From the pairing info the MTD user can find all the wunits paired with
   * @wunit using the following loop:
   *
   * for (i = 0; i < mtd_pairing_groups(mtd); i++) {
   *	info.pair = i;
   *	mtd_pairing_info_to_wunit(mtd, &info);
   *	...
   * }
   */
  int mtd_wunit_to_pairing_info(struct mtd_info *mtd, int wunit,
  			      struct mtd_pairing_info *info)
  {
  	int npairs = mtd_wunit_per_eb(mtd) / mtd_pairing_groups(mtd);
  
  	if (wunit < 0 || wunit >= npairs)
  		return -EINVAL;
  
  	if (mtd->pairing && mtd->pairing->get_info)
  		return mtd->pairing->get_info(mtd, wunit, info);
  
  	info->group = 0;
  	info->pair = wunit;
  
  	return 0;
  }
  EXPORT_SYMBOL_GPL(mtd_wunit_to_pairing_info);
  
  /**
   * mtd_wunit_to_pairing_info - get wunit from pairing information
   * @mtd: pointer to new MTD device info structure
   * @info: pairing information struct
   *
   * Returns a positive number representing the wunit associated to the info
   * struct, or a negative error code.
   *
   * This is the reverse of mtd_wunit_to_pairing_info(), and can help one to
   * iterate over all wunits of a given pair (see mtd_wunit_to_pairing_info()
   * doc).
   *
   * It can also be used to only program the first page of each pair (i.e.
   * page attached to group 0), which allows one to use an MLC NAND in
   * software-emulated SLC mode:
   *
   * info.group = 0;
   * npairs = mtd_wunit_per_eb(mtd) / mtd_pairing_groups(mtd);
   * for (info.pair = 0; info.pair < npairs; info.pair++) {
   *	wunit = mtd_pairing_info_to_wunit(mtd, &info);
   *	mtd_write(mtd, mtd_wunit_to_offset(mtd, blkoffs, wunit),
   *		  mtd->writesize, &retlen, buf + (i * mtd->writesize));
   * }
   */
  int mtd_pairing_info_to_wunit(struct mtd_info *mtd,
  			      const struct mtd_pairing_info *info)
  {
  	int ngroups = mtd_pairing_groups(mtd);
  	int npairs = mtd_wunit_per_eb(mtd) / ngroups;
  
  	if (!info || info->pair < 0 || info->pair >= npairs ||
  	    info->group < 0 || info->group >= ngroups)
  		return -EINVAL;
  
  	if (mtd->pairing && mtd->pairing->get_wunit)
  		return mtd->pairing->get_wunit(mtd, info);
  
  	return info->pair;
  }
  EXPORT_SYMBOL_GPL(mtd_pairing_info_to_wunit);
  
  /**
   * mtd_pairing_groups - get the number of pairing groups
   * @mtd: pointer to new MTD device info structure
   *
   * Returns the number of pairing groups.
   *
   * This number is usually equal to the number of bits exposed by a single
   * cell, and can be used in conjunction with mtd_pairing_info_to_wunit()
   * to iterate over all pages of a given pair.
   */
  int mtd_pairing_groups(struct mtd_info *mtd)
  {
  	if (!mtd->pairing || !mtd->pairing->ngroups)
  		return 1;
  
  	return mtd->pairing->ngroups;
  }
  EXPORT_SYMBOL_GPL(mtd_pairing_groups);
  
  /**
   *	add_mtd_device - register an MTD device
   *	@mtd: pointer to new MTD device info structure
   *
   *	Add a device to the list of MTD devices present in the system, and
   *	notify each currently active MTD 'user' of its arrival. Returns
   *	zero on success or non-zero on failure.
   */
  
  int add_mtd_device(struct mtd_info *mtd)
  {
  	struct mtd_notifier *not;
  	int i, error;
  
  	/*
  	 * May occur, for instance, on buggy drivers which call
  	 * mtd_device_parse_register() multiple times on the same master MTD,
  	 * especially with CONFIG_MTD_PARTITIONED_MASTER=y.
  	 */
  	if (WARN_ONCE(mtd->backing_dev_info, "MTD already registered\n"))
  		return -EEXIST;
  
  	mtd->backing_dev_info = mtd_bdi;
  
  	BUG_ON(mtd->writesize == 0);
  	mutex_lock(&mtd_table_mutex);
  
  	i = idr_alloc(&mtd_idr, mtd, 0, 0, GFP_KERNEL);
  	if (i < 0) {
  		error = i;
  		goto fail_locked;
  	}
  
  	mtd->index = i;
  	mtd->usecount = 0;
  
  	/* default value if not set by driver */
  	if (mtd->bitflip_threshold == 0)
  		mtd->bitflip_threshold = mtd->ecc_strength;
  
  	if (is_power_of_2(mtd->erasesize))
  		mtd->erasesize_shift = ffs(mtd->erasesize) - 1;
  	else
  		mtd->erasesize_shift = 0;
  
  	if (is_power_of_2(mtd->writesize))
  		mtd->writesize_shift = ffs(mtd->writesize) - 1;
  	else
  		mtd->writesize_shift = 0;
  
  	mtd->erasesize_mask = (1 << mtd->erasesize_shift) - 1;
  	mtd->writesize_mask = (1 << mtd->writesize_shift) - 1;
  
  	/* Some chips always power up locked. Unlock them now */
  	if ((mtd->flags & MTD_WRITEABLE) && (mtd->flags & MTD_POWERUP_LOCK)) {
  		error = mtd_unlock(mtd, 0, mtd->size);
  		if (error && error != -EOPNOTSUPP)
  			printk(KERN_WARNING
  			       "%s: unlock failed, writes may not work\n",
  			       mtd->name);
  		/* Ignore unlock failures? */
  		error = 0;
  	}
  
  	/* Caller should have set dev.parent to match the
  	 * physical device, if appropriate.
  	 */
  	mtd->dev.type = &mtd_devtype;
  	mtd->dev.class = &mtd_class;
  	mtd->dev.devt = MTD_DEVT(i);
  	dev_set_name(&mtd->dev, "mtd%d", i);
  	dev_set_drvdata(&mtd->dev, mtd);
  	of_node_get(mtd_get_of_node(mtd));
  	error = device_register(&mtd->dev);
  	if (error)
  		goto fail_added;
  
  	device_create(&mtd_class, mtd->dev.parent, MTD_DEVT(i) + 1, NULL,
  		      "mtd%dro", i);
  
  	pr_debug("mtd: Giving out device %d to %s\n", i, mtd->name);
  	/* No need to get a refcount on the module containing
  	   the notifier, since we hold the mtd_table_mutex */
  	list_for_each_entry(not, &mtd_notifiers, list)
  		not->add(mtd);
  
  	mutex_unlock(&mtd_table_mutex);
  	/* We _know_ we aren't being removed, because
  	   our caller is still holding us here. So none
  	   of this try_ nonsense, and no bitching about it
  	   either. :) */
  	__module_get(THIS_MODULE);
  	return 0;
  
  fail_added:
  	of_node_put(mtd_get_of_node(mtd));
  	idr_remove(&mtd_idr, i);
  fail_locked:
  	mutex_unlock(&mtd_table_mutex);
  	return error;
  }
  
  /**
   *	del_mtd_device - unregister an MTD device
   *	@mtd: pointer to MTD device info structure
   *
   *	Remove a device from the list of MTD devices present in the system,
   *	and notify each currently active MTD 'user' of its departure.
   *	Returns zero on success or 1 on failure, which currently will happen
   *	if the requested device does not appear to be present in the list.
   */
  
  int del_mtd_device(struct mtd_info *mtd)
  {
  	int ret;
  	struct mtd_notifier *not;
  
  	mutex_lock(&mtd_table_mutex);
  
  	if (idr_find(&mtd_idr, mtd->index) != mtd) {
  		ret = -ENODEV;
  		goto out_error;
  	}
  
  	/* No need to get a refcount on the module containing
  		the notifier, since we hold the mtd_table_mutex */
  	list_for_each_entry(not, &mtd_notifiers, list)
  		not->remove(mtd);
  
  	if (mtd->usecount) {
  		printk(KERN_NOTICE "Removing MTD device #%d (%s) with use count %d\n",
  		       mtd->index, mtd->name, mtd->usecount);
  		ret = -EBUSY;
  	} else {
  		device_unregister(&mtd->dev);
  
  		idr_remove(&mtd_idr, mtd->index);
  		of_node_put(mtd_get_of_node(mtd));
  
  		module_put(THIS_MODULE);
  		ret = 0;
  	}
  
  out_error:
  	mutex_unlock(&mtd_table_mutex);
  	return ret;
  }
  
  static int mtd_add_device_partitions(struct mtd_info *mtd,
  				     struct mtd_partitions *parts)
  {
  	const struct mtd_partition *real_parts = parts->parts;
  	int nbparts = parts->nr_parts;
  	int ret;
  
  	if (nbparts == 0 || IS_ENABLED(CONFIG_MTD_PARTITIONED_MASTER)) {
  		ret = add_mtd_device(mtd);
  		if (ret)
  			return ret;
  	}
  
  	if (nbparts > 0) {
  		ret = add_mtd_partitions(mtd, real_parts, nbparts);
  		if (ret && IS_ENABLED(CONFIG_MTD_PARTITIONED_MASTER))
  			del_mtd_device(mtd);
  		return ret;
  	}
  
  	return 0;
  }
  
  /*
   * Set a few defaults based on the parent devices, if not provided by the
   * driver
   */
  static void mtd_set_dev_defaults(struct mtd_info *mtd)
  {
  	if (mtd->dev.parent) {
  		if (!mtd->owner && mtd->dev.parent->driver)
  			mtd->owner = mtd->dev.parent->driver->owner;
  		if (!mtd->name)
  			mtd->name = dev_name(mtd->dev.parent);
  	} else {
  		pr_debug("mtd device won't show a device symlink in sysfs\n");
  	}
  }
  
  /**
   * mtd_device_parse_register - parse partitions and register an MTD device.
   *
   * @mtd: the MTD device to register
   * @types: the list of MTD partition probes to try, see
   *         'parse_mtd_partitions()' for more information
   * @parser_data: MTD partition parser-specific data
   * @parts: fallback partition information to register, if parsing fails;
   *         only valid if %nr_parts > %0
   * @nr_parts: the number of partitions in parts, if zero then the full
   *            MTD device is registered if no partition info is found
   *
   * This function aggregates MTD partitions parsing (done by
   * 'parse_mtd_partitions()') and MTD device and partitions registering. It
   * basically follows the most common pattern found in many MTD drivers:
   *
   * * It first tries to probe partitions on MTD device @mtd using parsers
   *   specified in @types (if @types is %NULL, then the default list of parsers
   *   is used, see 'parse_mtd_partitions()' for more information). If none are
   *   found this functions tries to fallback to information specified in
   *   @parts/@nr_parts.
   * * If any partitioning info was found, this function registers the found
   *   partitions. If the MTD_PARTITIONED_MASTER option is set, then the device
   *   as a whole is registered first.
   * * If no partitions were found this function just registers the MTD device
   *   @mtd and exits.
   *
   * Returns zero in case of success and a negative error code in case of failure.
   */
  int mtd_device_parse_register(struct mtd_info *mtd, const char * const *types,
  			      struct mtd_part_parser_data *parser_data,
  			      const struct mtd_partition *parts,
  			      int nr_parts)
  {
  	struct mtd_partitions parsed;
  	int ret;
  
  	mtd_set_dev_defaults(mtd);
  
  	memset(&parsed, 0, sizeof(parsed));
  
  	ret = parse_mtd_partitions(mtd, types, &parsed, parser_data);
  	if ((ret < 0 || parsed.nr_parts == 0) && parts && nr_parts) {
  		/* Fall back to driver-provided partitions */
  		parsed = (struct mtd_partitions){
  			.parts		= parts,
  			.nr_parts	= nr_parts,
  		};
  	} else if (ret < 0) {
  		/* Didn't come up with parsed OR fallback partitions */
  		pr_info("mtd: failed to find partitions; one or more parsers reports errors (%d)\n",
  			ret);
  		/* Don't abort on errors; we can still use unpartitioned MTD */
  		memset(&parsed, 0, sizeof(parsed));
  	}
  
  	ret = mtd_add_device_partitions(mtd, &parsed);
  	if (ret)
  		goto out;
  
  	/*
  	 * FIXME: some drivers unfortunately call this function more than once.
  	 * So we have to check if we've already assigned the reboot notifier.
  	 *
  	 * Generally, we can make multiple calls work for most cases, but it
  	 * does cause problems with parse_mtd_partitions() above (e.g.,
  	 * cmdlineparts will register partitions more than once).
  	 */
  	WARN_ONCE(mtd->_reboot && mtd->reboot_notifier.notifier_call,
  		  "MTD already registered\n");
  	if (mtd->_reboot && !mtd->reboot_notifier.notifier_call) {
  		mtd->reboot_notifier.notifier_call = mtd_reboot_notifier;
  		register_reboot_notifier(&mtd->reboot_notifier);
  	}
  
  out:
  	/* Cleanup any parsed partitions */
  	mtd_part_parser_cleanup(&parsed);
  	return ret;
  }
  EXPORT_SYMBOL_GPL(mtd_device_parse_register);
  
  /**
   * mtd_device_unregister - unregister an existing MTD device.
   *
   * @master: the MTD device to unregister.  This will unregister both the master
   *          and any partitions if registered.
   */
  int mtd_device_unregister(struct mtd_info *master)
  {
  	int err;
  
  	if (master->_reboot)
  		unregister_reboot_notifier(&master->reboot_notifier);
  
  	err = del_mtd_partitions(master);
  	if (err)
  		return err;
  
  	if (!device_is_registered(&master->dev))
  		return 0;
  
  	return del_mtd_device(master);
  }
  EXPORT_SYMBOL_GPL(mtd_device_unregister);
  
  /**
   *	register_mtd_user - register a 'user' of MTD devices.
   *	@new: pointer to notifier info structure
   *
   *	Registers a pair of callbacks function to be called upon addition
   *	or removal of MTD devices. Causes the 'add' callback to be immediately
   *	invoked for each MTD device currently present in the system.
   */
  void register_mtd_user (struct mtd_notifier *new)
  {
  	struct mtd_info *mtd;
  
  	mutex_lock(&mtd_table_mutex);
  
  	list_add(&new->list, &mtd_notifiers);
  
  	__module_get(THIS_MODULE);
  
  	mtd_for_each_device(mtd)
  		new->add(mtd);
  
  	mutex_unlock(&mtd_table_mutex);
  }
  EXPORT_SYMBOL_GPL(register_mtd_user);
  
  /**
   *	unregister_mtd_user - unregister a 'user' of MTD devices.
   *	@old: pointer to notifier info structure
   *
   *	Removes a callback function pair from the list of 'users' to be
   *	notified upon addition or removal of MTD devices. Causes the
   *	'remove' callback to be immediately invoked for each MTD device
   *	currently present in the system.
   */
  int unregister_mtd_user (struct mtd_notifier *old)
  {
  	struct mtd_info *mtd;
  
  	mutex_lock(&mtd_table_mutex);
  
  	module_put(THIS_MODULE);
  
  	mtd_for_each_device(mtd)
  		old->remove(mtd);
  
  	list_del(&old->list);
  	mutex_unlock(&mtd_table_mutex);
  	return 0;
  }
  EXPORT_SYMBOL_GPL(unregister_mtd_user);
  
  /**
   *	get_mtd_device - obtain a validated handle for an MTD device
   *	@mtd: last known address of the required MTD device
   *	@num: internal device number of the required MTD device
   *
   *	Given a number and NULL address, return the num'th entry in the device
   *	table, if any.	Given an address and num == -1, search the device table
   *	for a device with that address and return if it's still present. Given
   *	both, return the num'th driver only if its address matches. Return
   *	error code if not.
   */
  struct mtd_info *get_mtd_device(struct mtd_info *mtd, int num)
  {
  	struct mtd_info *ret = NULL, *other;
  	int err = -ENODEV;
  
  	mutex_lock(&mtd_table_mutex);
  
  	if (num == -1) {
  		mtd_for_each_device(other) {
  			if (other == mtd) {
  				ret = mtd;
  				break;
  			}
  		}
  	} else if (num >= 0) {
  		ret = idr_find(&mtd_idr, num);
  		if (mtd && mtd != ret)
  			ret = NULL;
  	}
  
  	if (!ret) {
  		ret = ERR_PTR(err);
  		goto out;
  	}
  
  	err = __get_mtd_device(ret);
  	if (err)
  		ret = ERR_PTR(err);
  out:
  	mutex_unlock(&mtd_table_mutex);
  	return ret;
  }
  EXPORT_SYMBOL_GPL(get_mtd_device);
  
  
  int __get_mtd_device(struct mtd_info *mtd)
  {
  	int err;
  
  	if (!try_module_get(mtd->owner))
  		return -ENODEV;
  
  	if (mtd->_get_device) {
  		err = mtd->_get_device(mtd);
  
  		if (err) {
  			module_put(mtd->owner);
  			return err;
  		}
  	}
  	mtd->usecount++;
  	return 0;
  }
  EXPORT_SYMBOL_GPL(__get_mtd_device);
  
  /**
   *	get_mtd_device_nm - obtain a validated handle for an MTD device by
   *	device name
   *	@name: MTD device name to open
   *
   * 	This function returns MTD device description structure in case of
   * 	success and an error code in case of failure.
   */
  struct mtd_info *get_mtd_device_nm(const char *name)
  {
  	int err = -ENODEV;
  	struct mtd_info *mtd = NULL, *other;
  
  	mutex_lock(&mtd_table_mutex);
  
  	mtd_for_each_device(other) {
  		if (!strcmp(name, other->name)) {
  			mtd = other;
  			break;
  		}
  	}
  
  	if (!mtd)
  		goto out_unlock;
  
  	err = __get_mtd_device(mtd);
  	if (err)
  		goto out_unlock;
  
  	mutex_unlock(&mtd_table_mutex);
  	return mtd;
  
  out_unlock:
  	mutex_unlock(&mtd_table_mutex);
  	return ERR_PTR(err);
  }
  EXPORT_SYMBOL_GPL(get_mtd_device_nm);
  
  void put_mtd_device(struct mtd_info *mtd)
  {
  	mutex_lock(&mtd_table_mutex);
  	__put_mtd_device(mtd);
  	mutex_unlock(&mtd_table_mutex);
  
  }
  EXPORT_SYMBOL_GPL(put_mtd_device);
  
  void __put_mtd_device(struct mtd_info *mtd)
  {
  	--mtd->usecount;
  	BUG_ON(mtd->usecount < 0);
  
  	if (mtd->_put_device)
  		mtd->_put_device(mtd);
  
  	module_put(mtd->owner);
  }
  EXPORT_SYMBOL_GPL(__put_mtd_device);
  
  /*
   * Erase is an asynchronous operation.  Device drivers are supposed
   * to call instr->callback() whenever the operation completes, even
   * if it completes with a failure.
   * Callers are supposed to pass a callback function and wait for it
   * to be called before writing to the block.
   */
  int mtd_erase(struct mtd_info *mtd, struct erase_info *instr)
  {
  	if (instr->addr >= mtd->size || instr->len > mtd->size - instr->addr)
  		return -EINVAL;
  	if (!(mtd->flags & MTD_WRITEABLE))
  		return -EROFS;
  	instr->fail_addr = MTD_FAIL_ADDR_UNKNOWN;
  	if (!instr->len) {
  		instr->state = MTD_ERASE_DONE;
  		mtd_erase_callback(instr);
  		return 0;
  	}
  	ledtrig_mtd_activity();
  	return mtd->_erase(mtd, instr);
  }
  EXPORT_SYMBOL_GPL(mtd_erase);
  
  /*
   * This stuff for eXecute-In-Place. phys is optional and may be set to NULL.
   */
  int mtd_point(struct mtd_info *mtd, loff_t from, size_t len, size_t *retlen,
  	      void **virt, resource_size_t *phys)
  {
  	*retlen = 0;
  	*virt = NULL;
  	if (phys)
  		*phys = 0;
  	if (!mtd->_point)
  		return -EOPNOTSUPP;
  	if (from < 0 || from >= mtd->size || len > mtd->size - from)
  		return -EINVAL;
  	if (!len)
  		return 0;
  	return mtd->_point(mtd, from, len, retlen, virt, phys);
  }
  EXPORT_SYMBOL_GPL(mtd_point);
  
  /* We probably shouldn't allow XIP if the unpoint isn't a NULL */
  int mtd_unpoint(struct mtd_info *mtd, loff_t from, size_t len)
  {
  	if (!mtd->_point)
  		return -EOPNOTSUPP;
  	if (from < 0 || from >= mtd->size || len > mtd->size - from)
  		return -EINVAL;
  	if (!len)
  		return 0;
  	return mtd->_unpoint(mtd, from, len);
  }
  EXPORT_SYMBOL_GPL(mtd_unpoint);
  
  /*
   * Allow NOMMU mmap() to directly map the device (if not NULL)
   * - return the address to which the offset maps
   * - return -ENOSYS to indicate refusal to do the mapping
   */
  unsigned long mtd_get_unmapped_area(struct mtd_info *mtd, unsigned long len,
  				    unsigned long offset, unsigned long flags)
  {
  	if (!mtd->_get_unmapped_area)
  		return -EOPNOTSUPP;
  	if (offset >= mtd->size || len > mtd->size - offset)
  		return -EINVAL;
  	return mtd->_get_unmapped_area(mtd, len, offset, flags);
  }
  EXPORT_SYMBOL_GPL(mtd_get_unmapped_area);
  
  int mtd_read(struct mtd_info *mtd, loff_t from, size_t len, size_t *retlen,
  	     u_char *buf)
  {
  	int ret_code;
  	*retlen = 0;
  	if (from < 0 || from >= mtd->size || len > mtd->size - from)
  		return -EINVAL;
  	if (!len)
  		return 0;
  
  	ledtrig_mtd_activity();
  	/*
  	 * In the absence of an error, drivers return a non-negative integer
  	 * representing the maximum number of bitflips that were corrected on
  	 * any one ecc region (if applicable; zero otherwise).
  	 */
  	ret_code = mtd->_read(mtd, from, len, retlen, buf);
  	if (unlikely(ret_code < 0))
  		return ret_code;
  	if (mtd->ecc_strength == 0)
  		return 0;	/* device lacks ecc */
  	return ret_code >= mtd->bitflip_threshold ? -EUCLEAN : 0;
  }
  EXPORT_SYMBOL_GPL(mtd_read);
  
  int mtd_write(struct mtd_info *mtd, loff_t to, size_t len, size_t *retlen,
  	      const u_char *buf)
  {
  	*retlen = 0;
  	if (to < 0 || to >= mtd->size || len > mtd->size - to)
  		return -EINVAL;
  	if (!mtd->_write || !(mtd->flags & MTD_WRITEABLE))
  		return -EROFS;
  	if (!len)
  		return 0;
  	ledtrig_mtd_activity();
  	return mtd->_write(mtd, to, len, retlen, buf);
  }
  EXPORT_SYMBOL_GPL(mtd_write);
  
  /*
   * In blackbox flight recorder like scenarios we want to make successful writes
   * in interrupt context. panic_write() is only intended to be called when its
   * known the kernel is about to panic and we need the write to succeed. Since
   * the kernel is not going to be running for much longer, this function can
   * break locks and delay to ensure the write succeeds (but not sleep).
   */
  int mtd_panic_write(struct mtd_info *mtd, loff_t to, size_t len, size_t *retlen,
  		    const u_char *buf)
  {
  	*retlen = 0;
  	if (!mtd->_panic_write)
  		return -EOPNOTSUPP;
  	if (to < 0 || to >= mtd->size || len > mtd->size - to)
  		return -EINVAL;
  	if (!(mtd->flags & MTD_WRITEABLE))
  		return -EROFS;
  	if (!len)
  		return 0;
  	return mtd->_panic_write(mtd, to, len, retlen, buf);
  }
  EXPORT_SYMBOL_GPL(mtd_panic_write);
  
  int mtd_read_oob(struct mtd_info *mtd, loff_t from, struct mtd_oob_ops *ops)
  {
  	int ret_code;
  	ops->retlen = ops->oobretlen = 0;
  	if (!mtd->_read_oob)
  		return -EOPNOTSUPP;
  
  	ledtrig_mtd_activity();
  	/*
  	 * In cases where ops->datbuf != NULL, mtd->_read_oob() has semantics
  	 * similar to mtd->_read(), returning a non-negative integer
  	 * representing max bitflips. In other cases, mtd->_read_oob() may
  	 * return -EUCLEAN. In all cases, perform similar logic to mtd_read().
  	 */
  	ret_code = mtd->_read_oob(mtd, from, ops);
  	if (unlikely(ret_code < 0))
  		return ret_code;
  	if (mtd->ecc_strength == 0)
  		return 0;	/* device lacks ecc */
  	return ret_code >= mtd->bitflip_threshold ? -EUCLEAN : 0;
  }
  EXPORT_SYMBOL_GPL(mtd_read_oob);
  
  int mtd_write_oob(struct mtd_info *mtd, loff_t to,
  				struct mtd_oob_ops *ops)
  {
  	ops->retlen = ops->oobretlen = 0;
  	if (!mtd->_write_oob)
  		return -EOPNOTSUPP;
  	if (!(mtd->flags & MTD_WRITEABLE))
  		return -EROFS;
  	ledtrig_mtd_activity();
  	return mtd->_write_oob(mtd, to, ops);
  }
  EXPORT_SYMBOL_GPL(mtd_write_oob);
  
  /**
   * mtd_ooblayout_ecc - Get the OOB region definition of a specific ECC section
   * @mtd: MTD device structure
   * @section: ECC section. Depending on the layout you may have all the ECC
   *	     bytes stored in a single contiguous section, or one section
   *	     per ECC chunk (and sometime several sections for a single ECC
   *	     ECC chunk)
   * @oobecc: OOB region struct filled with the appropriate ECC position
   *	    information
   *
   * This function returns ECC section information in the OOB area. If you want
   * to get all the ECC bytes information, then you should call
   * mtd_ooblayout_ecc(mtd, section++, oobecc) until it returns -ERANGE.
   *
   * Returns zero on success, a negative error code otherwise.
   */
  int mtd_ooblayout_ecc(struct mtd_info *mtd, int section,
  		      struct mtd_oob_region *oobecc)
  {
  	memset(oobecc, 0, sizeof(*oobecc));
  
  	if (!mtd || section < 0)
  		return -EINVAL;
  
  	if (!mtd->ooblayout || !mtd->ooblayout->ecc)
  		return -ENOTSUPP;
  
  	return mtd->ooblayout->ecc(mtd, section, oobecc);
  }
  EXPORT_SYMBOL_GPL(mtd_ooblayout_ecc);
  
  /**
   * mtd_ooblayout_free - Get the OOB region definition of a specific free
   *			section
   * @mtd: MTD device structure
   * @section: Free section you are interested in. Depending on the layout
   *	     you may have all the free bytes stored in a single contiguous
   *	     section, or one section per ECC chunk plus an extra section
   *	     for the remaining bytes (or other funky layout).
   * @oobfree: OOB region struct filled with the appropriate free position
   *	     information
   *
   * This function returns free bytes position in the OOB area. If you want
   * to get all the free bytes information, then you should call
   * mtd_ooblayout_free(mtd, section++, oobfree) until it returns -ERANGE.
   *
   * Returns zero on success, a negative error code otherwise.
   */
  int mtd_ooblayout_free(struct mtd_info *mtd, int section,
  		       struct mtd_oob_region *oobfree)
  {
  	memset(oobfree, 0, sizeof(*oobfree));
  
  	if (!mtd || section < 0)
  		return -EINVAL;
  
  	if (!mtd->ooblayout || !mtd->ooblayout->free)
  		return -ENOTSUPP;
  
  	return mtd->ooblayout->free(mtd, section, oobfree);
  }
  EXPORT_SYMBOL_GPL(mtd_ooblayout_free);
  
  /**
   * mtd_ooblayout_find_region - Find the region attached to a specific byte
   * @mtd: mtd info structure
   * @byte: the byte we are searching for
   * @sectionp: pointer where the section id will be stored
   * @oobregion: used to retrieve the ECC position
   * @iter: iterator function. Should be either mtd_ooblayout_free or
   *	  mtd_ooblayout_ecc depending on the region type you're searching for
   *
   * This function returns the section id and oobregion information of a
   * specific byte. For example, say you want to know where the 4th ECC byte is
   * stored, you'll use:
   *
   * mtd_ooblayout_find_region(mtd, 3, &section, &oobregion, mtd_ooblayout_ecc);
   *
   * Returns zero on success, a negative error code otherwise.
   */
  static int mtd_ooblayout_find_region(struct mtd_info *mtd, int byte,
  				int *sectionp, struct mtd_oob_region *oobregion,
  				int (*iter)(struct mtd_info *,
  					    int section,
  					    struct mtd_oob_region *oobregion))
  {
  	int pos = 0, ret, section = 0;
  
  	memset(oobregion, 0, sizeof(*oobregion));
  
  	while (1) {
  		ret = iter(mtd, section, oobregion);
  		if (ret)
  			return ret;
  
  		if (pos + oobregion->length > byte)
  			break;
  
  		pos += oobregion->length;
  		section++;
  	}
  
  	/*
  	 * Adjust region info to make it start at the beginning at the
  	 * 'start' ECC byte.
  	 */
  	oobregion->offset += byte - pos;
  	oobregion->length -= byte - pos;
  	*sectionp = section;
  
  	return 0;
  }
  
  /**
   * mtd_ooblayout_find_eccregion - Find the ECC region attached to a specific
   *				  ECC byte
   * @mtd: mtd info structure
   * @eccbyte: the byte we are searching for
   * @sectionp: pointer where the section id will be stored
   * @oobregion: OOB region information
   *
   * Works like mtd_ooblayout_find_region() except it searches for a specific ECC
   * byte.
   *
   * Returns zero on success, a negative error code otherwise.
   */
  int mtd_ooblayout_find_eccregion(struct mtd_info *mtd, int eccbyte,
  				 int *section,
  				 struct mtd_oob_region *oobregion)
  {
  	return mtd_ooblayout_find_region(mtd, eccbyte, section, oobregion,
  					 mtd_ooblayout_ecc);
  }
  EXPORT_SYMBOL_GPL(mtd_ooblayout_find_eccregion);
  
  /**
   * mtd_ooblayout_get_bytes - Extract OOB bytes from the oob buffer
   * @mtd: mtd info structure
   * @buf: destination buffer to store OOB bytes
   * @oobbuf: OOB buffer
   * @start: first byte to retrieve
   * @nbytes: number of bytes to retrieve
   * @iter: section iterator
   *
   * Extract bytes attached to a specific category (ECC or free)
   * from the OOB buffer and copy them into buf.
   *
   * Returns zero on success, a negative error code otherwise.
   */
  static int mtd_ooblayout_get_bytes(struct mtd_info *mtd, u8 *buf,
  				const u8 *oobbuf, int start, int nbytes,
  				int (*iter)(struct mtd_info *,
  					    int section,
  					    struct mtd_oob_region *oobregion))
  {
  	struct mtd_oob_region oobregion;
  	int section, ret;
  
  	ret = mtd_ooblayout_find_region(mtd, start, &section,
  					&oobregion, iter);
  
  	while (!ret) {
  		int cnt;
  
  		cnt = min_t(int, nbytes, oobregion.length);
  		memcpy(buf, oobbuf + oobregion.offset, cnt);
  		buf += cnt;
  		nbytes -= cnt;
  
  		if (!nbytes)
  			break;
  
  		ret = iter(mtd, ++section, &oobregion);
  	}
  
  	return ret;
  }
  
  /**
   * mtd_ooblayout_set_bytes - put OOB bytes into the oob buffer
   * @mtd: mtd info structure
   * @buf: source buffer to get OOB bytes from
   * @oobbuf: OOB buffer
   * @start: first OOB byte to set
   * @nbytes: number of OOB bytes to set
   * @iter: section iterator
   *
   * Fill the OOB buffer with data provided in buf. The category (ECC or free)
   * is selected by passing the appropriate iterator.
   *
   * Returns zero on success, a negative error code otherwise.
   */
  static int mtd_ooblayout_set_bytes(struct mtd_info *mtd, const u8 *buf,
  				u8 *oobbuf, int start, int nbytes,
  				int (*iter)(struct mtd_info *,
  					    int section,
  					    struct mtd_oob_region *oobregion))
  {
  	struct mtd_oob_region oobregion;
  	int section, ret;
  
  	ret = mtd_ooblayout_find_region(mtd, start, &section,
  					&oobregion, iter);
  
  	while (!ret) {
  		int cnt;
  
  		cnt = min_t(int, nbytes, oobregion.length);
  		memcpy(oobbuf + oobregion.offset, buf, cnt);
  		buf += cnt;
  		nbytes -= cnt;
  
  		if (!nbytes)
  			break;
  
  		ret = iter(mtd, ++section, &oobregion);
  	}
  
  	return ret;
  }
  
  /**
   * mtd_ooblayout_count_bytes - count the number of bytes in a OOB category
   * @mtd: mtd info structure
   * @iter: category iterator
   *
   * Count the number of bytes in a given category.
   *
   * Returns a positive value on success, a negative error code otherwise.
   */
  static int mtd_ooblayout_count_bytes(struct mtd_info *mtd,
  				int (*iter)(struct mtd_info *,
  					    int section,
  					    struct mtd_oob_region *oobregion))
  {
  	struct mtd_oob_region oobregion;
  	int section = 0, ret, nbytes = 0;
  
  	while (1) {
  		ret = iter(mtd, section++, &oobregion);
  		if (ret) {
  			if (ret == -ERANGE)
  				ret = nbytes;
  			break;
  		}
  
  		nbytes += oobregion.length;
  	}
  
  	return ret;
  }
  
  /**
   * mtd_ooblayout_get_eccbytes - extract ECC bytes from the oob buffer
   * @mtd: mtd info structure
   * @eccbuf: destination buffer to store ECC bytes
   * @oobbuf: OOB buffer
   * @start: first ECC byte to retrieve
   * @nbytes: number of ECC bytes to retrieve
   *
   * Works like mtd_ooblayout_get_bytes(), except it acts on ECC bytes.
   *
   * Returns zero on success, a negative error code otherwise.
   */
  int mtd_ooblayout_get_eccbytes(struct mtd_info *mtd, u8 *eccbuf,
  			       const u8 *oobbuf, int start, int nbytes)
  {
  	return mtd_ooblayout_get_bytes(mtd, eccbuf, oobbuf, start, nbytes,
  				       mtd_ooblayout_ecc);
  }
  EXPORT_SYMBOL_GPL(mtd_ooblayout_get_eccbytes);
  
  /**
   * mtd_ooblayout_set_eccbytes - set ECC bytes into the oob buffer
   * @mtd: mtd info structure
   * @eccbuf: source buffer to get ECC bytes from
   * @oobbuf: OOB buffer
   * @start: first ECC byte to set
   * @nbytes: number of ECC bytes to set
   *
   * Works like mtd_ooblayout_set_bytes(), except it acts on ECC bytes.
   *
   * Returns zero on success, a negative error code otherwise.
   */
  int mtd_ooblayout_set_eccbytes(struct mtd_info *mtd, const u8 *eccbuf,
  			       u8 *oobbuf, int start, int nbytes)
  {
  	return mtd_ooblayout_set_bytes(mtd, eccbuf, oobbuf, start, nbytes,
  				       mtd_ooblayout_ecc);
  }
  EXPORT_SYMBOL_GPL(mtd_ooblayout_set_eccbytes);
  
  /**
   * mtd_ooblayout_get_databytes - extract data bytes from the oob buffer
   * @mtd: mtd info structure
   * @databuf: destination buffer to store ECC bytes
   * @oobbuf: OOB buffer
   * @start: first ECC byte to retrieve
   * @nbytes: number of ECC bytes to retrieve
   *
   * Works like mtd_ooblayout_get_bytes(), except it acts on free bytes.
   *
   * Returns zero on success, a negative error code otherwise.
   */
  int mtd_ooblayout_get_databytes(struct mtd_info *mtd, u8 *databuf,
  				const u8 *oobbuf, int start, int nbytes)
  {
  	return mtd_ooblayout_get_bytes(mtd, databuf, oobbuf, start, nbytes,
  				       mtd_ooblayout_free);
  }
  EXPORT_SYMBOL_GPL(mtd_ooblayout_get_databytes);
  
  /**
   * mtd_ooblayout_get_eccbytes - set data bytes into the oob buffer
   * @mtd: mtd info structure
   * @eccbuf: source buffer to get data bytes from
   * @oobbuf: OOB buffer
   * @start: first ECC byte to set
   * @nbytes: number of ECC bytes to set
   *
   * Works like mtd_ooblayout_get_bytes(), except it acts on free bytes.
   *
   * Returns zero on success, a negative error code otherwise.
   */
  int mtd_ooblayout_set_databytes(struct mtd_info *mtd, const u8 *databuf,
  				u8 *oobbuf, int start, int nbytes)
  {
  	return mtd_ooblayout_set_bytes(mtd, databuf, oobbuf, start, nbytes,
  				       mtd_ooblayout_free);
  }
  EXPORT_SYMBOL_GPL(mtd_ooblayout_set_databytes);
  
  /**
   * mtd_ooblayout_count_freebytes - count the number of free bytes in OOB
   * @mtd: mtd info structure
   *
   * Works like mtd_ooblayout_count_bytes(), except it count free bytes.
   *
   * Returns zero on success, a negative error code otherwise.
   */
  int mtd_ooblayout_count_freebytes(struct mtd_info *mtd)
  {
  	return mtd_ooblayout_count_bytes(mtd, mtd_ooblayout_free);
  }
  EXPORT_SYMBOL_GPL(mtd_ooblayout_count_freebytes);
  
  /**
   * mtd_ooblayout_count_freebytes - count the number of ECC bytes in OOB
   * @mtd: mtd info structure
   *
   * Works like mtd_ooblayout_count_bytes(), except it count ECC bytes.
   *
   * Returns zero on success, a negative error code otherwise.
   */
  int mtd_ooblayout_count_eccbytes(struct mtd_info *mtd)
  {
  	return mtd_ooblayout_count_bytes(mtd, mtd_ooblayout_ecc);
  }
  EXPORT_SYMBOL_GPL(mtd_ooblayout_count_eccbytes);
  
  /*
   * Method to access the protection register area, present in some flash
   * devices. The user data is one time programmable but the factory data is read
   * only.
   */
  int mtd_get_fact_prot_info(struct mtd_info *mtd, size_t len, size_t *retlen,
  			   struct otp_info *buf)
  {
  	if (!mtd->_get_fact_prot_info)
  		return -EOPNOTSUPP;
  	if (!len)
  		return 0;
  	return mtd->_get_fact_prot_info(mtd, len, retlen, buf);
  }
  EXPORT_SYMBOL_GPL(mtd_get_fact_prot_info);
  
  int mtd_read_fact_prot_reg(struct mtd_info *mtd, loff_t from, size_t len,
  			   size_t *retlen, u_char *buf)
  {
  	*retlen = 0;
  	if (!mtd->_read_fact_prot_reg)
  		return -EOPNOTSUPP;
  	if (!len)
  		return 0;
  	return mtd->_read_fact_prot_reg(mtd, from, len, retlen, buf);
  }
  EXPORT_SYMBOL_GPL(mtd_read_fact_prot_reg);
  
  int mtd_get_user_prot_info(struct mtd_info *mtd, size_t len, size_t *retlen,
  			   struct otp_info *buf)
  {
  	if (!mtd->_get_user_prot_info)
  		return -EOPNOTSUPP;
  	if (!len)
  		return 0;
  	return mtd->_get_user_prot_info(mtd, len, retlen, buf);
  }
  EXPORT_SYMBOL_GPL(mtd_get_user_prot_info);
  
  int mtd_read_user_prot_reg(struct mtd_info *mtd, loff_t from, size_t len,
  			   size_t *retlen, u_char *buf)
  {
  	*retlen = 0;
  	if (!mtd->_read_user_prot_reg)
  		return -EOPNOTSUPP;
  	if (!len)
  		return 0;
  	return mtd->_read_user_prot_reg(mtd, from, len, retlen, buf);
  }
  EXPORT_SYMBOL_GPL(mtd_read_user_prot_reg);
  
  int mtd_write_user_prot_reg(struct mtd_info *mtd, loff_t to, size_t len,
  			    size_t *retlen, u_char *buf)
  {
  	int ret;
  
  	*retlen = 0;
  	if (!mtd->_write_user_prot_reg)
  		return -EOPNOTSUPP;
  	if (!len)
  		return 0;
  	ret = mtd->_write_user_prot_reg(mtd, to, len, retlen, buf);
  	if (ret)
  		return ret;
  
  	/*
  	 * If no data could be written at all, we are out of memory and
  	 * must return -ENOSPC.
  	 */
  	return (*retlen) ? 0 : -ENOSPC;
  }
  EXPORT_SYMBOL_GPL(mtd_write_user_prot_reg);
  
  int mtd_lock_user_prot_reg(struct mtd_info *mtd, loff_t from, size_t len)
  {
  	if (!mtd->_lock_user_prot_reg)
  		return -EOPNOTSUPP;
  	if (!len)
  		return 0;
  	return mtd->_lock_user_prot_reg(mtd, from, len);
  }
  EXPORT_SYMBOL_GPL(mtd_lock_user_prot_reg);
  
  /* Chip-supported device locking */
  int mtd_lock(struct mtd_info *mtd, loff_t ofs, uint64_t len)
  {
  	if (!mtd->_lock)
  		return -EOPNOTSUPP;
  	if (ofs < 0 || ofs >= mtd->size || len > mtd->size - ofs)
  		return -EINVAL;
  	if (!len)
  		return 0;
  	return mtd->_lock(mtd, ofs, len);
  }
  EXPORT_SYMBOL_GPL(mtd_lock);
  
  int mtd_unlock(struct mtd_info *mtd, loff_t ofs, uint64_t len)
  {
  	if (!mtd->_unlock)
  		return -EOPNOTSUPP;
  	if (ofs < 0 || ofs >= mtd->size || len > mtd->size - ofs)
  		return -EINVAL;
  	if (!len)
  		return 0;
  	return mtd->_unlock(mtd, ofs, len);
  }
  EXPORT_SYMBOL_GPL(mtd_unlock);
  
  int mtd_is_locked(struct mtd_info *mtd, loff_t ofs, uint64_t len)
  {
  	if (!mtd->_is_locked)
  		return -EOPNOTSUPP;
  	if (ofs < 0 || ofs >= mtd->size || len > mtd->size - ofs)
  		return -EINVAL;
  	if (!len)
  		return 0;
  	return mtd->_is_locked(mtd, ofs, len);
  }
  EXPORT_SYMBOL_GPL(mtd_is_locked);
  
  int mtd_block_isreserved(struct mtd_info *mtd, loff_t ofs)
  {
  	if (ofs < 0 || ofs >= mtd->size)
  		return -EINVAL;
  	if (!mtd->_block_isreserved)
  		return 0;
  	return mtd->_block_isreserved(mtd, ofs);
  }
  EXPORT_SYMBOL_GPL(mtd_block_isreserved);
  
  int mtd_block_isbad(struct mtd_info *mtd, loff_t ofs)
  {
  	if (ofs < 0 || ofs >= mtd->size)
  		return -EINVAL;
  	if (!mtd->_block_isbad)
  		return 0;
  	return mtd->_block_isbad(mtd, ofs);
  }
  EXPORT_SYMBOL_GPL(mtd_block_isbad);
  
  int mtd_block_markbad(struct mtd_info *mtd, loff_t ofs)
  {
  	if (!mtd->_block_markbad)
  		return -EOPNOTSUPP;
  	if (ofs < 0 || ofs >= mtd->size)
  		return -EINVAL;
  	if (!(mtd->flags & MTD_WRITEABLE))
  		return -EROFS;
  	return mtd->_block_markbad(mtd, ofs);
  }
  EXPORT_SYMBOL_GPL(mtd_block_markbad);
  
  /*
   * default_mtd_writev - the default writev method
   * @mtd: mtd device description object pointer
   * @vecs: the vectors to write
   * @count: count of vectors in @vecs
   * @to: the MTD device offset to write to
   * @retlen: on exit contains the count of bytes written to the MTD device.
   *
   * This function returns zero in case of success and a negative error code in
   * case of failure.
   */
  static int default_mtd_writev(struct mtd_info *mtd, const struct kvec *vecs,
  			      unsigned long count, loff_t to, size_t *retlen)
  {
  	unsigned long i;
  	size_t totlen = 0, thislen;
  	int ret = 0;
  
  	for (i = 0; i < count; i++) {
  		if (!vecs[i].iov_len)
  			continue;
  		ret = mtd_write(mtd, to, vecs[i].iov_len, &thislen,
  				vecs[i].iov_base);
  		totlen += thislen;
  		if (ret || thislen != vecs[i].iov_len)
  			break;
  		to += vecs[i].iov_len;
  	}
  	*retlen = totlen;
  	return ret;
  }
  
  /*
   * mtd_writev - the vector-based MTD write method
   * @mtd: mtd device description object pointer
   * @vecs: the vectors to write
   * @count: count of vectors in @vecs
   * @to: the MTD device offset to write to
   * @retlen: on exit contains the count of bytes written to the MTD device.
   *
   * This function returns zero in case of success and a negative error code in
   * case of failure.
   */
  int mtd_writev(struct mtd_info *mtd, const struct kvec *vecs,
  	       unsigned long count, loff_t to, size_t *retlen)
  {
  	*retlen = 0;
  	if (!(mtd->flags & MTD_WRITEABLE))
  		return -EROFS;
  	if (!mtd->_writev)
  		return default_mtd_writev(mtd, vecs, count, to, retlen);
  	return mtd->_writev(mtd, vecs, count, to, retlen);
  }
  EXPORT_SYMBOL_GPL(mtd_writev);
  
  /**
   * mtd_kmalloc_up_to - allocate a contiguous buffer up to the specified size
   * @mtd: mtd device description object pointer
   * @size: a pointer to the ideal or maximum size of the allocation, points
   *        to the actual allocation size on success.
   *
   * This routine attempts to allocate a contiguous kernel buffer up to
   * the specified size, backing off the size of the request exponentially
   * until the request succeeds or until the allocation size falls below
   * the system page size. This attempts to make sure it does not adversely
   * impact system performance, so when allocating more than one page, we
   * ask the memory allocator to avoid re-trying, swapping, writing back
   * or performing I/O.
   *
   * Note, this function also makes sure that the allocated buffer is aligned to
   * the MTD device's min. I/O unit, i.e. the "mtd->writesize" value.
   *
   * This is called, for example by mtd_{read,write} and jffs2_scan_medium,
   * to handle smaller (i.e. degraded) buffer allocations under low- or
   * fragmented-memory situations where such reduced allocations, from a
   * requested ideal, are allowed.
   *
   * Returns a pointer to the allocated buffer on success; otherwise, NULL.
   */
  void *mtd_kmalloc_up_to(const struct mtd_info *mtd, size_t *size)
  {
  	gfp_t flags = __GFP_NOWARN | __GFP_DIRECT_RECLAIM | __GFP_NORETRY;
  	size_t min_alloc = max_t(size_t, mtd->writesize, PAGE_SIZE);
  	void *kbuf;
  
  	*size = min_t(size_t, *size, KMALLOC_MAX_SIZE);
  
  	while (*size > min_alloc) {
  		kbuf = kmalloc(*size, flags);
  		if (kbuf)
  			return kbuf;
  
  		*size >>= 1;
  		*size = ALIGN(*size, mtd->writesize);
  	}
  
  	/*
  	 * For the last resort allocation allow 'kmalloc()' to do all sorts of
  	 * things (write-back, dropping caches, etc) by using GFP_KERNEL.
  	 */
  	return kmalloc(*size, GFP_KERNEL);
  }
  EXPORT_SYMBOL_GPL(mtd_kmalloc_up_to);
  
  #ifdef CONFIG_PROC_FS
  
  /*====================================================================*/
  /* Support for /proc/mtd */
  
  static int mtd_proc_show(struct seq_file *m, void *v)
  {
  	struct mtd_info *mtd;
  
  	seq_puts(m, "dev:    size   erasesize  name\n");
  	mutex_lock(&mtd_table_mutex);
  	mtd_for_each_device(mtd) {
  		seq_printf(m, "mtd%d: %8.8llx %8.8x \"%s\"\n",
  			   mtd->index, (unsigned long long)mtd->size,
  			   mtd->erasesize, mtd->name);
  	}
  	mutex_unlock(&mtd_table_mutex);
  	return 0;
  }
  
  static int mtd_proc_open(struct inode *inode, struct file *file)
  {
  	return single_open(file, mtd_proc_show, NULL);
  }
  
  static const struct file_operations mtd_proc_ops = {
  	.open		= mtd_proc_open,
  	.read		= seq_read,
  	.llseek		= seq_lseek,
  	.release	= single_release,
  };
  #endif /* CONFIG_PROC_FS */
  
  /*====================================================================*/
  /* Init code */
  
  static struct backing_dev_info * __init mtd_bdi_init(char *name)
  {
  	struct backing_dev_info *bdi;
  	int ret;
  
  	bdi = kzalloc(sizeof(*bdi), GFP_KERNEL);
  	if (!bdi)
  		return ERR_PTR(-ENOMEM);
  
  	ret = bdi_setup_and_register(bdi, name);
  	if (ret)
  		kfree(bdi);
  
  	return ret ? ERR_PTR(ret) : bdi;
  }
  
  static struct proc_dir_entry *proc_mtd;
  
  static int __init init_mtd(void)
  {
  	int ret;
  
  	ret = class_register(&mtd_class);
  	if (ret)
  		goto err_reg;
  
  	mtd_bdi = mtd_bdi_init("mtd");
  	if (IS_ERR(mtd_bdi)) {
  		ret = PTR_ERR(mtd_bdi);
  		goto err_bdi;
  	}
  
  	proc_mtd = proc_create("mtd", 0, NULL, &mtd_proc_ops);
  
  	ret = init_mtdchar();
  	if (ret)
  		goto out_procfs;
  
  	return 0;
  
  out_procfs:
  	if (proc_mtd)
  		remove_proc_entry("mtd", NULL);
  	bdi_destroy(mtd_bdi);
  	kfree(mtd_bdi);
  err_bdi:
  	class_unregister(&mtd_class);
  err_reg:
  	pr_err("Error registering mtd class or bdi: %d\n", ret);
  	return ret;
  }
  
  static void __exit cleanup_mtd(void)
  {
  	cleanup_mtdchar();
  	if (proc_mtd)
  		remove_proc_entry("mtd", NULL);
  	class_unregister(&mtd_class);
  	bdi_destroy(mtd_bdi);
  	kfree(mtd_bdi);
  	idr_destroy(&mtd_idr);
  }
  
  module_init(init_mtd);
  module_exit(cleanup_mtd);
  
  MODULE_LICENSE("GPL");
  MODULE_AUTHOR("David Woodhouse <dwmw2@infradead.org>");
  MODULE_DESCRIPTION("Core MTD registration and access routines");
  