Adding upstream version 4.19.249.upstream/4.19.249upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1934 insertions, 0 deletions

diff --git a/drivers/mtd/mtdcore.c b/drivers/mtd/mtdcore.c
new file mode 100644
index 000000000..a0b1a7814
--- /dev/null
+++ b/drivers/mtd/mtdcore.c
@@ -0,0 +1,1934 @@
+/*
+ * 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/debugfs.h>
+
+#include <linux/mtd/mtd.h>
+#include <linux/mtd/partitions.h>
+
+#include "mtdcore.h"
+
+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_oobavail_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->oobavail);
+}
+static DEVICE_ATTR(oobavail, S_IRUGO, mtd_oobavail_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_oobavail.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 const 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_pairing_info_to_wunit - 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);
+
+static struct dentry *dfs_dir_mtd;
+
+/**
+ *	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->dev.type, "MTD already registered\n"))
+		return -EEXIST;
+
+	BUG_ON(mtd->writesize == 0);
+
+	if (WARN_ON((!mtd->erasesize || !mtd->_erase) &&
+		    !(mtd->flags & MTD_NO_ERASE)))
+		return -EINVAL;
+
+	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;
+
+	if (!IS_ERR_OR_NULL(dfs_dir_mtd)) {
+		mtd->dbg.dfs_dir = debugfs_create_dir(dev_name(&mtd->dev), dfs_dir_mtd);
+		if (IS_ERR_OR_NULL(mtd->dbg.dfs_dir)) {
+			pr_debug("mtd device %s won't show data in debugfs\n",
+				 dev_name(&mtd->dev));
+		}
+	}
+
+	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);
+
+	debugfs_remove_recursive(mtd->dbg.dfs_dir);
+
+	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;
+}
+
+/*
+ * 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:
+ *
+ * * If the MTD_PARTITIONED_MASTER option is set, then the device as a whole is
+ *   registered first.
+ * * Then It 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 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)
+{
+	int ret;
+
+	mtd_set_dev_defaults(mtd);
+
+	if (IS_ENABLED(CONFIG_MTD_PARTITIONED_MASTER)) {
+		ret = add_mtd_device(mtd);
+		if (ret)
+			return ret;
+	}
+
+	/* Prefer parsed partitions over driver-provided fallback */
+	ret = parse_mtd_partitions(mtd, types, parser_data);
+	if (ret == -EPROBE_DEFER)
+		goto out;
+
+	if (ret > 0)
+		ret = 0;
+	else if (nr_parts)
+		ret = add_mtd_partitions(mtd, parts, nr_parts);
+	else if (!device_is_registered(&mtd->dev))
+		ret = add_mtd_device(mtd);
+	else
+		ret = 0;
+
+	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:
+	if (ret && device_is_registered(&mtd->dev))
+		del_mtd_device(mtd);
+
+	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 synchronous operation. Device drivers are epected to return a
+ * negative error code if the operation failed and update instr->fail_addr
+ * to point the portion that was not properly erased.
+ */
+int mtd_erase(struct mtd_info *mtd, struct erase_info *instr)
+{
+	instr->fail_addr = MTD_FAIL_ADDR_UNKNOWN;
+
+	if (!mtd->erasesize || !mtd->_erase)
+		return -ENOTSUPP;
+
+	if (instr->addr >= mtd->size || instr->len > mtd->size - instr->addr)
+		return -EINVAL;
+	if (!(mtd->flags & MTD_WRITEABLE))
+		return -EROFS;
+
+	if (!instr->len)
+		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->_unpoint)
+		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)
+{
+	size_t retlen;
+	void *virt;
+	int ret;
+
+	ret = mtd_point(mtd, offset, len, &retlen, &virt, NULL);
+	if (ret)
+		return ret;
+	if (retlen != len) {
+		mtd_unpoint(mtd, offset, retlen);
+		return -ENOSYS;
+	}
+	return (unsigned long)virt;
+}
+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).
+	 */
+	if (mtd->_read) {
+		ret_code = mtd->_read(mtd, from, len, retlen, buf);
+	} else if (mtd->_read_oob) {
+		struct mtd_oob_ops ops = {
+			.len = len,
+			.datbuf = buf,
+		};
+
+		ret_code = mtd->_read_oob(mtd, from, &ops);
+		*retlen = ops.retlen;
+	} else {
+		return -ENOTSUPP;
+	}
+
+	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->_write_oob) ||
+	    !(mtd->flags & MTD_WRITEABLE))
+		return -EROFS;
+	if (!len)
+		return 0;
+	ledtrig_mtd_activity();
+
+	if (!mtd->_write) {
+		struct mtd_oob_ops ops = {
+			.len = len,
+			.datbuf = (u8 *)buf,
+		};
+		int ret;
+
+		ret = mtd->_write_oob(mtd, to, &ops);
+		*retlen = ops.retlen;
+		return ret;
+	}
+
+	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);
+
+static int mtd_check_oob_ops(struct mtd_info *mtd, loff_t offs,
+			     struct mtd_oob_ops *ops)
+{
+	/*
+	 * Some users are setting ->datbuf or ->oobbuf to NULL, but are leaving
+	 * ->len or ->ooblen uninitialized. Force ->len and ->ooblen to 0 in
+	 *  this case.
+	 */
+	if (!ops->datbuf)
+		ops->len = 0;
+
+	if (!ops->oobbuf)
+		ops->ooblen = 0;
+
+	if (offs < 0 || offs + ops->len > mtd->size)
+		return -EINVAL;
+
+	if (ops->ooblen) {
+		u64 maxooblen;
+
+		if (ops->ooboffs >= mtd_oobavail(mtd, ops))
+			return -EINVAL;
+
+		maxooblen = ((mtd_div_by_ws(mtd->size, mtd) -
+			      mtd_div_by_ws(offs, mtd)) *
+			     mtd_oobavail(mtd, ops)) - ops->ooboffs;
+		if (ops->ooblen > maxooblen)
+			return -EINVAL;
+	}
+
+	return 0;
+}
+
+int mtd_read_oob(struct mtd_info *mtd, loff_t from, struct mtd_oob_ops *ops)
+{
+	int ret_code;
+	ops->retlen = ops->oobretlen = 0;
+
+	ret_code = mtd_check_oob_ops(mtd, from, ops);
+	if (ret_code)
+		return ret_code;
+
+	ledtrig_mtd_activity();
+
+	/* Check the validity of a potential fallback on mtd->_read */
+	if (!mtd->_read_oob && (!mtd->_read || ops->oobbuf))
+		return -EOPNOTSUPP;
+
+	if (mtd->_read_oob)
+		ret_code = mtd->_read_oob(mtd, from, ops);
+	else
+		ret_code = mtd->_read(mtd, from, ops->len, &ops->retlen,
+				      ops->datbuf);
+
+	/*
+	 * 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().
+	 */
+	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)
+{
+	int ret;
+
+	ops->retlen = ops->oobretlen = 0;
+
+	if (!(mtd->flags & MTD_WRITEABLE))
+		return -EROFS;
+
+	ret = mtd_check_oob_ops(mtd, to, ops);
+	if (ret)
+		return ret;
+
+	ledtrig_mtd_activity();
+
+	/* Check the validity of a potential fallback on mtd->_write */
+	if (!mtd->_write_oob && (!mtd->_write || ops->oobbuf))
+		return -EOPNOTSUPP;
+
+	if (mtd->_write_oob)
+		return mtd->_write_oob(mtd, to, ops);
+	else
+		return mtd->_write(mtd, to, ops->len, &ops->retlen,
+				   ops->datbuf);
+}
+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_set_databytes - set data bytes into the oob buffer
+ * @mtd: mtd info structure
+ * @databuf: 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_eccbytes - 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;
+}
+#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 = bdi_alloc(GFP_KERNEL);
+	if (!bdi)
+		return ERR_PTR(-ENOMEM);
+
+	bdi->name = name;
+	/*
+	 * We put '-0' suffix to the name to get the same name format as we
+	 * used to get. Since this is called only once, we get a unique name. 
+	 */
+	ret = bdi_register(bdi, "%.28s-0", name);
+	if (ret)
+		bdi_put(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_single("mtd", 0, NULL, mtd_proc_show);
+
+	ret = init_mtdchar();
+	if (ret)
+		goto out_procfs;
+
+	dfs_dir_mtd = debugfs_create_dir("mtd", NULL);
+
+	return 0;
+
+out_procfs:
+	if (proc_mtd)
+		remove_proc_entry("mtd", NULL);
+	bdi_put(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)
+{
+	debugfs_remove_recursive(dfs_dir_mtd);
+	cleanup_mtdchar();
+	if (proc_mtd)
+		remove_proc_entry("mtd", NULL);
+	class_unregister(&mtd_class);
+	bdi_put(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");