Merge tag 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/dledford/rdma

[deliverable/linux.git] / drivers / mtd / mtdcore.c

/*
 * 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/kconfig.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;
}

/**
 *      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;
        }
        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;

        /*
         * 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;
        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;
        /*
         * 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);

/*
 * 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 int __init mtd_bdi_init(struct backing_dev_info *bdi, const char *name)
{
        int ret;

        ret = bdi_init(bdi);
        if (!ret)
                ret = bdi_register(bdi, NULL, "%s", name);

        if (ret)
                bdi_destroy(bdi);

        return ret;
}

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;

        ret = mtd_bdi_init(&mtd_bdi, "mtd");
        if (ret)
                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);
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);
        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");