GNU Linux-libre 5.19-rc6-gnu

[releases.git] / drivers / mtd / mtdcore.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Core registration and callback routines for MTD
 * drivers and users.
 *
 * Copyright © 1999-2010 David Woodhouse <dwmw2@infradead.org>
 * Copyright © 2006      Red Hat UK Limited 
 */

#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/nvmem-provider.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);
}

#define MTD_DEVICE_ATTR_RO(name) \
static DEVICE_ATTR(name, 0444, mtd_##name##_show, NULL)

#define MTD_DEVICE_ATTR_RW(name) \
static DEVICE_ATTR(name, 0644, mtd_##name##_show, mtd_##name##_store)

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 sysfs_emit(buf, "%s\n", type);
}
MTD_DEVICE_ATTR_RO(type);

static ssize_t mtd_flags_show(struct device *dev,
                struct device_attribute *attr, char *buf)
{
        struct mtd_info *mtd = dev_get_drvdata(dev);

        return sysfs_emit(buf, "0x%lx\n", (unsigned long)mtd->flags);
}
MTD_DEVICE_ATTR_RO(flags);

static ssize_t mtd_size_show(struct device *dev,
                struct device_attribute *attr, char *buf)
{
        struct mtd_info *mtd = dev_get_drvdata(dev);

        return sysfs_emit(buf, "%llu\n", (unsigned long long)mtd->size);
}
MTD_DEVICE_ATTR_RO(size);

static ssize_t mtd_erasesize_show(struct device *dev,
                struct device_attribute *attr, char *buf)
{
        struct mtd_info *mtd = dev_get_drvdata(dev);

        return sysfs_emit(buf, "%lu\n", (unsigned long)mtd->erasesize);
}
MTD_DEVICE_ATTR_RO(erasesize);

static ssize_t mtd_writesize_show(struct device *dev,
                struct device_attribute *attr, char *buf)
{
        struct mtd_info *mtd = dev_get_drvdata(dev);

        return sysfs_emit(buf, "%lu\n", (unsigned long)mtd->writesize);
}
MTD_DEVICE_ATTR_RO(writesize);

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 sysfs_emit(buf, "%u\n", subpagesize);
}
MTD_DEVICE_ATTR_RO(subpagesize);

static ssize_t mtd_oobsize_show(struct device *dev,
                struct device_attribute *attr, char *buf)
{
        struct mtd_info *mtd = dev_get_drvdata(dev);

        return sysfs_emit(buf, "%lu\n", (unsigned long)mtd->oobsize);
}
MTD_DEVICE_ATTR_RO(oobsize);

static ssize_t mtd_oobavail_show(struct device *dev,
                                 struct device_attribute *attr, char *buf)
{
        struct mtd_info *mtd = dev_get_drvdata(dev);

        return sysfs_emit(buf, "%u\n", mtd->oobavail);
}
MTD_DEVICE_ATTR_RO(oobavail);

static ssize_t mtd_numeraseregions_show(struct device *dev,
                struct device_attribute *attr, char *buf)
{
        struct mtd_info *mtd = dev_get_drvdata(dev);

        return sysfs_emit(buf, "%u\n", mtd->numeraseregions);
}
MTD_DEVICE_ATTR_RO(numeraseregions);

static ssize_t mtd_name_show(struct device *dev,
                struct device_attribute *attr, char *buf)
{
        struct mtd_info *mtd = dev_get_drvdata(dev);

        return sysfs_emit(buf, "%s\n", mtd->name);
}
MTD_DEVICE_ATTR_RO(name);

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 sysfs_emit(buf, "%u\n", mtd->ecc_strength);
}
MTD_DEVICE_ATTR_RO(ecc_strength);

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 sysfs_emit(buf, "%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;
}
MTD_DEVICE_ATTR_RW(bitflip_threshold);

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 sysfs_emit(buf, "%u\n", mtd->ecc_step_size);

}
MTD_DEVICE_ATTR_RO(ecc_step_size);

static ssize_t mtd_corrected_bits_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 sysfs_emit(buf, "%u\n", ecc_stats->corrected);
}
MTD_DEVICE_ATTR_RO(corrected_bits);     /* ecc stats corrected */

static ssize_t mtd_ecc_failures_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 sysfs_emit(buf, "%u\n", ecc_stats->failed);
}
MTD_DEVICE_ATTR_RO(ecc_failures);       /* ecc stats errors */

static ssize_t mtd_bad_blocks_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 sysfs_emit(buf, "%u\n", ecc_stats->badblocks);
}
MTD_DEVICE_ATTR_RO(bad_blocks);

static ssize_t mtd_bbt_blocks_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 sysfs_emit(buf, "%u\n", ecc_stats->bbtblocks);
}
MTD_DEVICE_ATTR_RO(bbt_blocks);

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,
};

static bool mtd_expert_analysis_mode;

#ifdef CONFIG_DEBUG_FS
bool mtd_check_expert_analysis_mode(void)
{
        const char *mtd_expert_analysis_warning =
                "Bad block checks have been entirely disabled.\n"
                "This is only reserved for post-mortem forensics and debug purposes.\n"
                "Never enable this mode if you do not know what you are doing!\n";

        return WARN_ONCE(mtd_expert_analysis_mode, mtd_expert_analysis_warning);
}
EXPORT_SYMBOL_GPL(mtd_check_expert_analysis_mode);
#endif

static struct dentry *dfs_dir_mtd;

static void mtd_debugfs_populate(struct mtd_info *mtd)
{
        struct device *dev = &mtd->dev;

        if (IS_ERR_OR_NULL(dfs_dir_mtd))
                return;

        mtd->dbg.dfs_dir = debugfs_create_dir(dev_name(dev), dfs_dir_mtd);
}

#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)
{
        struct mtd_info *master = mtd_get_master(mtd);
        int npairs = mtd_wunit_per_eb(master) / mtd_pairing_groups(master);

        if (wunit < 0 || wunit >= npairs)
                return -EINVAL;

        if (master->pairing && master->pairing->get_info)
                return master->pairing->get_info(master, 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)
{
        struct mtd_info *master = mtd_get_master(mtd);
        int ngroups = mtd_pairing_groups(master);
        int npairs = mtd_wunit_per_eb(master) / ngroups;

        if (!info || info->pair < 0 || info->pair >= npairs ||
            info->group < 0 || info->group >= ngroups)
                return -EINVAL;

        if (master->pairing && master->pairing->get_wunit)
                return mtd->pairing->get_wunit(master, 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)
{
        struct mtd_info *master = mtd_get_master(mtd);

        if (!master->pairing || !master->pairing->ngroups)
                return 1;

        return master->pairing->ngroups;
}
EXPORT_SYMBOL_GPL(mtd_pairing_groups);

static int mtd_nvmem_reg_read(void *priv, unsigned int offset,
                              void *val, size_t bytes)
{
        struct mtd_info *mtd = priv;
        size_t retlen;
        int err;

        err = mtd_read(mtd, offset, bytes, &retlen, val);
        if (err && err != -EUCLEAN)
                return err;

        return retlen == bytes ? 0 : -EIO;
}

static int mtd_nvmem_add(struct mtd_info *mtd)
{
        struct device_node *node = mtd_get_of_node(mtd);
        struct nvmem_config config = {};

        config.id = -1;
        config.dev = &mtd->dev;
        config.name = dev_name(&mtd->dev);
        config.owner = THIS_MODULE;
        config.reg_read = mtd_nvmem_reg_read;
        config.size = mtd->size;
        config.word_size = 1;
        config.stride = 1;
        config.read_only = true;
        config.root_only = true;
        config.ignore_wp = true;
        config.no_of_node = !of_device_is_compatible(node, "nvmem-cells");
        config.priv = mtd;

        mtd->nvmem = nvmem_register(&config);
        if (IS_ERR(mtd->nvmem)) {
                /* Just ignore if there is no NVMEM support in the kernel */
                if (PTR_ERR(mtd->nvmem) == -EOPNOTSUPP) {
                        mtd->nvmem = NULL;
                } else {
                        dev_err(&mtd->dev, "Failed to register NVMEM device\n");
                        return PTR_ERR(mtd->nvmem);
                }
        }

        return 0;
}

/**
 *      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 device_node *np = mtd_get_of_node(mtd);
        struct mtd_info *master = mtd_get_master(mtd);
        struct mtd_notifier *not;
        int i, error, ofidx;

        /*
         * 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);

        /*
         * MTD drivers should implement ->_{write,read}() or
         * ->_{write,read}_oob(), but not both.
         */
        if (WARN_ON((mtd->_write && mtd->_write_oob) ||
                    (mtd->_read && mtd->_read_oob)))
                return -EINVAL;

        if (WARN_ON((!mtd->erasesize || !master->_erase) &&
                    !(mtd->flags & MTD_NO_ERASE)))
                return -EINVAL;

        /*
         * MTD_SLC_ON_MLC_EMULATION can only be set on partitions, when the
         * master is an MLC NAND and has a proper pairing scheme defined.
         * We also reject masters that implement ->_writev() for now, because
         * NAND controller drivers don't implement this hook, and adding the
         * SLC -> MLC address/length conversion to this path is useless if we
         * don't have a user.
         */
        if (mtd->flags & MTD_SLC_ON_MLC_EMULATION &&
            (!mtd_is_partition(mtd) || master->type != MTD_MLCNANDFLASH ||
             !master->pairing || master->_writev))
                return -EINVAL;

        mutex_lock(&mtd_table_mutex);

        ofidx = -1;
        if (np)
                ofidx = of_alias_get_id(np, "mtd");
        if (ofidx >= 0)
                i = idr_alloc(&mtd_idr, mtd, ofidx, ofidx + 1, GFP_KERNEL);
        else
                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 (mtd->flags & MTD_SLC_ON_MLC_EMULATION) {
                int ngroups = mtd_pairing_groups(master);

                mtd->erasesize /= ngroups;
                mtd->size = (u64)mtd_div_by_eb(mtd->size, master) *
                            mtd->erasesize;
        }

        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;

        /* Add the nvmem provider */
        error = mtd_nvmem_add(mtd);
        if (error)
                goto fail_nvmem_add;

        mtd_debugfs_populate(mtd);

        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_nvmem_add:
        device_unregister(&mtd->dev);
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 {
                debugfs_remove_recursive(mtd->dbg.dfs_dir);

                /* Try to remove the NVMEM provider */
                nvmem_unregister(mtd->nvmem);

                device_unregister(&mtd->dev);

                /* Clear dev so mtd can be safely re-registered later if desired */
                memset(&mtd->dev, 0, sizeof(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");
        }

        INIT_LIST_HEAD(&mtd->partitions);
        mutex_init(&mtd->master.partitions_lock);
        mutex_init(&mtd->master.chrdev_lock);
}

static ssize_t mtd_otp_size(struct mtd_info *mtd, bool is_user)
{
        struct otp_info *info;
        ssize_t size = 0;
        unsigned int i;
        size_t retlen;
        int ret;

        info = kmalloc(PAGE_SIZE, GFP_KERNEL);
        if (!info)
                return -ENOMEM;

        if (is_user)
                ret = mtd_get_user_prot_info(mtd, PAGE_SIZE, &retlen, info);
        else
                ret = mtd_get_fact_prot_info(mtd, PAGE_SIZE, &retlen, info);
        if (ret)
                goto err;

        for (i = 0; i < retlen / sizeof(*info); i++)
                size += info[i].length;

        kfree(info);
        return size;

err:
        kfree(info);

        /* ENODATA means there is no OTP region. */
        return ret == -ENODATA ? 0 : ret;
}

static struct nvmem_device *mtd_otp_nvmem_register(struct mtd_info *mtd,
                                                   const char *compatible,
                                                   int size,
                                                   nvmem_reg_read_t reg_read)
{
        struct nvmem_device *nvmem = NULL;
        struct nvmem_config config = {};
        struct device_node *np;

        /* DT binding is optional */
        np = of_get_compatible_child(mtd->dev.of_node, compatible);

        /* OTP nvmem will be registered on the physical device */
        config.dev = mtd->dev.parent;
        config.name = kasprintf(GFP_KERNEL, "%s-%s", dev_name(&mtd->dev), compatible);
        config.id = NVMEM_DEVID_NONE;
        config.owner = THIS_MODULE;
        config.type = NVMEM_TYPE_OTP;
        config.root_only = true;
        config.ignore_wp = true;
        config.reg_read = reg_read;
        config.size = size;
        config.of_node = np;
        config.priv = mtd;

        nvmem = nvmem_register(&config);
        /* Just ignore if there is no NVMEM support in the kernel */
        if (IS_ERR(nvmem) && PTR_ERR(nvmem) == -EOPNOTSUPP)
                nvmem = NULL;

        of_node_put(np);
        kfree(config.name);

        return nvmem;
}

static int mtd_nvmem_user_otp_reg_read(void *priv, unsigned int offset,
                                       void *val, size_t bytes)
{
        struct mtd_info *mtd = priv;
        size_t retlen;
        int ret;

        ret = mtd_read_user_prot_reg(mtd, offset, bytes, &retlen, val);
        if (ret)
                return ret;

        return retlen == bytes ? 0 : -EIO;
}

static int mtd_nvmem_fact_otp_reg_read(void *priv, unsigned int offset,
                                       void *val, size_t bytes)
{
        struct mtd_info *mtd = priv;
        size_t retlen;
        int ret;

        ret = mtd_read_fact_prot_reg(mtd, offset, bytes, &retlen, val);
        if (ret)
                return ret;

        return retlen == bytes ? 0 : -EIO;
}

static int mtd_otp_nvmem_add(struct mtd_info *mtd)
{
        struct nvmem_device *nvmem;
        ssize_t size;
        int err;

        if (mtd->_get_user_prot_info && mtd->_read_user_prot_reg) {
                size = mtd_otp_size(mtd, true);
                if (size < 0)
                        return size;

                if (size > 0) {
                        nvmem = mtd_otp_nvmem_register(mtd, "user-otp", size,
                                                       mtd_nvmem_user_otp_reg_read);
                        if (IS_ERR(nvmem)) {
                                dev_err(&mtd->dev, "Failed to register OTP NVMEM device\n");
                                return PTR_ERR(nvmem);
                        }
                        mtd->otp_user_nvmem = nvmem;
                }
        }

        if (mtd->_get_fact_prot_info && mtd->_read_fact_prot_reg) {
                size = mtd_otp_size(mtd, false);
                if (size < 0) {
                        err = size;
                        goto err;
                }

                if (size > 0) {
                        nvmem = mtd_otp_nvmem_register(mtd, "factory-otp", size,
                                                       mtd_nvmem_fact_otp_reg_read);
                        if (IS_ERR(nvmem)) {
                                dev_err(&mtd->dev, "Failed to register OTP NVMEM device\n");
                                err = PTR_ERR(nvmem);
                                goto err;
                        }
                        mtd->otp_factory_nvmem = nvmem;
                }
        }

        return 0;

err:
        nvmem_unregister(mtd->otp_user_nvmem);
        return err;
}

/**
 * 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);
        }

        ret = mtd_otp_nvmem_add(mtd);

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);
                memset(&master->reboot_notifier, 0, sizeof(master->reboot_notifier));
        }

        nvmem_unregister(master->otp_user_nvmem);
        nvmem_unregister(master->otp_factory_nvmem);

        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)
{
        struct mtd_info *master = mtd_get_master(mtd);
        int err;

        if (!try_module_get(master->owner))
                return -ENODEV;

        if (master->_get_device) {
                err = master->_get_device(mtd);

                if (err) {
                        module_put(master->owner);
                        return err;
                }
        }

        master->usecount++;

        while (mtd->parent) {
                mtd->usecount++;
                mtd = mtd->parent;
        }

        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)
{
        struct mtd_info *master = mtd_get_master(mtd);

        while (mtd->parent) {
                --mtd->usecount;
                BUG_ON(mtd->usecount < 0);
                mtd = mtd->parent;
        }

        master->usecount--;

        if (master->_put_device)
                master->_put_device(master);

        module_put(master->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)
{
        struct mtd_info *master = mtd_get_master(mtd);
        u64 mst_ofs = mtd_get_master_ofs(mtd, 0);
        struct erase_info adjinstr;
        int ret;

        instr->fail_addr = MTD_FAIL_ADDR_UNKNOWN;
        adjinstr = *instr;

        if (!mtd->erasesize || !master->_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();

        if (mtd->flags & MTD_SLC_ON_MLC_EMULATION) {
                adjinstr.addr = (loff_t)mtd_div_by_eb(instr->addr, mtd) *
                                master->erasesize;
                adjinstr.len = ((u64)mtd_div_by_eb(instr->addr + instr->len, mtd) *
                                master->erasesize) -
                               adjinstr.addr;
        }

        adjinstr.addr += mst_ofs;

        ret = master->_erase(master, &adjinstr);

        if (adjinstr.fail_addr != MTD_FAIL_ADDR_UNKNOWN) {
                instr->fail_addr = adjinstr.fail_addr - mst_ofs;
                if (mtd->flags & MTD_SLC_ON_MLC_EMULATION) {
                        instr->fail_addr = mtd_div_by_eb(instr->fail_addr,
                                                         master);
                        instr->fail_addr *= mtd->erasesize;
                }
        }

        return ret;
}
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)
{
        struct mtd_info *master = mtd_get_master(mtd);

        *retlen = 0;
        *virt = NULL;
        if (phys)
                *phys = 0;
        if (!master->_point)
                return -EOPNOTSUPP;
        if (from < 0 || from >= mtd->size || len > mtd->size - from)
                return -EINVAL;
        if (!len)
                return 0;

        from = mtd_get_master_ofs(mtd, from);
        return master->_point(master, 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)
{
        struct mtd_info *master = mtd_get_master(mtd);

        if (!master->_unpoint)
                return -EOPNOTSUPP;
        if (from < 0 || from >= mtd->size || len > mtd->size - from)
                return -EINVAL;
        if (!len)
                return 0;
        return master->_unpoint(master, mtd_get_master_ofs(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);

static void mtd_update_ecc_stats(struct mtd_info *mtd, struct mtd_info *master,
                                 const struct mtd_ecc_stats *old_stats)
{
        struct mtd_ecc_stats diff;

        if (master == mtd)
                return;

        diff = master->ecc_stats;
        diff.failed -= old_stats->failed;
        diff.corrected -= old_stats->corrected;

        while (mtd->parent) {
                mtd->ecc_stats.failed += diff.failed;
                mtd->ecc_stats.corrected += diff.corrected;
                mtd = mtd->parent;
        }
}

int mtd_read(struct mtd_info *mtd, loff_t from, size_t len, size_t *retlen,
             u_char *buf)
{
        struct mtd_oob_ops ops = {
                .len = len,
                .datbuf = buf,
        };
        int ret;

        ret = mtd_read_oob(mtd, from, &ops);
        *retlen = ops.retlen;

        return ret;
}
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)
{
        struct mtd_oob_ops ops = {
                .len = len,
                .datbuf = (u8 *)buf,
        };
        int ret;

        ret = mtd_write_oob(mtd, to, &ops);
        *retlen = ops.retlen;

        return ret;
}
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)
{
        struct mtd_info *master = mtd_get_master(mtd);

        *retlen = 0;
        if (!master->_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;
        if (!master->oops_panic_write)
                master->oops_panic_write = true;

        return master->_panic_write(master, mtd_get_master_ofs(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) {
                size_t maxooblen;

                if (ops->ooboffs >= mtd_oobavail(mtd, ops))
                        return -EINVAL;

                maxooblen = ((size_t)(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;
}

static int mtd_read_oob_std(struct mtd_info *mtd, loff_t from,
                            struct mtd_oob_ops *ops)
{
        struct mtd_info *master = mtd_get_master(mtd);
        int ret;

        from = mtd_get_master_ofs(mtd, from);
        if (master->_read_oob)
                ret = master->_read_oob(master, from, ops);
        else
                ret = master->_read(master, from, ops->len, &ops->retlen,
                                    ops->datbuf);

        return ret;
}

static int mtd_write_oob_std(struct mtd_info *mtd, loff_t to,
                             struct mtd_oob_ops *ops)
{
        struct mtd_info *master = mtd_get_master(mtd);
        int ret;

        to = mtd_get_master_ofs(mtd, to);
        if (master->_write_oob)
                ret = master->_write_oob(master, to, ops);
        else
                ret = master->_write(master, to, ops->len, &ops->retlen,
                                     ops->datbuf);

        return ret;
}

static int mtd_io_emulated_slc(struct mtd_info *mtd, loff_t start, bool read,
                               struct mtd_oob_ops *ops)
{
        struct mtd_info *master = mtd_get_master(mtd);
        int ngroups = mtd_pairing_groups(master);
        int npairs = mtd_wunit_per_eb(master) / ngroups;
        struct mtd_oob_ops adjops = *ops;
        unsigned int wunit, oobavail;
        struct mtd_pairing_info info;
        int max_bitflips = 0;
        u32 ebofs, pageofs;
        loff_t base, pos;

        ebofs = mtd_mod_by_eb(start, mtd);
        base = (loff_t)mtd_div_by_eb(start, mtd) * master->erasesize;
        info.group = 0;
        info.pair = mtd_div_by_ws(ebofs, mtd);
        pageofs = mtd_mod_by_ws(ebofs, mtd);
        oobavail = mtd_oobavail(mtd, ops);

        while (ops->retlen < ops->len || ops->oobretlen < ops->ooblen) {
                int ret;

                if (info.pair >= npairs) {
                        info.pair = 0;
                        base += master->erasesize;
                }

                wunit = mtd_pairing_info_to_wunit(master, &info);
                pos = mtd_wunit_to_offset(mtd, base, wunit);

                adjops.len = ops->len - ops->retlen;
                if (adjops.len > mtd->writesize - pageofs)
                        adjops.len = mtd->writesize - pageofs;

                adjops.ooblen = ops->ooblen - ops->oobretlen;
                if (adjops.ooblen > oobavail - adjops.ooboffs)
                        adjops.ooblen = oobavail - adjops.ooboffs;

                if (read) {
                        ret = mtd_read_oob_std(mtd, pos + pageofs, &adjops);
                        if (ret > 0)
                                max_bitflips = max(max_bitflips, ret);
                } else {
                        ret = mtd_write_oob_std(mtd, pos + pageofs, &adjops);
                }

                if (ret < 0)
                        return ret;

                max_bitflips = max(max_bitflips, ret);
                ops->retlen += adjops.retlen;
                ops->oobretlen += adjops.oobretlen;
                adjops.datbuf += adjops.retlen;
                adjops.oobbuf += adjops.oobretlen;
                adjops.ooboffs = 0;
                pageofs = 0;
                info.pair++;
        }

        return max_bitflips;
}

int mtd_read_oob(struct mtd_info *mtd, loff_t from, struct mtd_oob_ops *ops)
{
        struct mtd_info *master = mtd_get_master(mtd);
        struct mtd_ecc_stats old_stats = master->ecc_stats;
        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 (!master->_read_oob && (!master->_read || ops->oobbuf))
                return -EOPNOTSUPP;

        if (mtd->flags & MTD_SLC_ON_MLC_EMULATION)
                ret_code = mtd_io_emulated_slc(mtd, from, true, ops);
        else
                ret_code = mtd_read_oob_std(mtd, from, ops);

        mtd_update_ecc_stats(mtd, master, &old_stats);

        /*
         * 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)
{
        struct mtd_info *master = mtd_get_master(mtd);
        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 (!master->_write_oob && (!master->_write || ops->oobbuf))
                return -EOPNOTSUPP;

        if (mtd->flags & MTD_SLC_ON_MLC_EMULATION)
                return mtd_io_emulated_slc(mtd, to, false, ops);

        return mtd_write_oob_std(mtd, to, ops);
}
EXPORT_SYMBOL_GPL(mtd_write_oob);

/**
 * mtd_ooblayout_ecc - Get the OOB region definition of a specific ECC section
 * @mtd: MTD device structure
 * @section: ECC section. Depending on the layout you may have all the ECC
 *           bytes stored in a single contiguous section, or one section
 *           per ECC chunk (and sometime several sections for a single ECC
 *           ECC chunk)
 * @oobecc: OOB region struct filled with the appropriate ECC position
 *          information
 *
 * This function returns ECC section information in the OOB area. If you want
 * to get all the ECC bytes information, then you should call
 * mtd_ooblayout_ecc(mtd, section++, oobecc) until it returns -ERANGE.
 *
 * Returns zero on success, a negative error code otherwise.
 */
int mtd_ooblayout_ecc(struct mtd_info *mtd, int section,
                      struct mtd_oob_region *oobecc)
{
        struct mtd_info *master = mtd_get_master(mtd);

        memset(oobecc, 0, sizeof(*oobecc));

        if (!master || section < 0)
                return -EINVAL;

        if (!master->ooblayout || !master->ooblayout->ecc)
                return -ENOTSUPP;

        return master->ooblayout->ecc(master, 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)
{
        struct mtd_info *master = mtd_get_master(mtd);

        memset(oobfree, 0, sizeof(*oobfree));

        if (!master || section < 0)
                return -EINVAL;

        if (!master->ooblayout || !master->ooblayout->free)
                return -ENOTSUPP;

        return master->ooblayout->free(master, 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
 * @section: 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_set_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)
{
        struct mtd_info *master = mtd_get_master(mtd);

        if (!master->_get_fact_prot_info)
                return -EOPNOTSUPP;
        if (!len)
                return 0;
        return master->_get_fact_prot_info(master, 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)
{
        struct mtd_info *master = mtd_get_master(mtd);

        *retlen = 0;
        if (!master->_read_fact_prot_reg)
                return -EOPNOTSUPP;
        if (!len)
                return 0;
        return master->_read_fact_prot_reg(master, 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)
{
        struct mtd_info *master = mtd_get_master(mtd);

        if (!master->_get_user_prot_info)
                return -EOPNOTSUPP;
        if (!len)
                return 0;
        return master->_get_user_prot_info(master, 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)
{
        struct mtd_info *master = mtd_get_master(mtd);

        *retlen = 0;
        if (!master->_read_user_prot_reg)
                return -EOPNOTSUPP;
        if (!len)
                return 0;
        return master->_read_user_prot_reg(master, 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, const u_char *buf)
{
        struct mtd_info *master = mtd_get_master(mtd);
        int ret;

        *retlen = 0;
        if (!master->_write_user_prot_reg)
                return -EOPNOTSUPP;
        if (!len)
                return 0;
        ret = master->_write_user_prot_reg(master, 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)
{
        struct mtd_info *master = mtd_get_master(mtd);

        if (!master->_lock_user_prot_reg)
                return -EOPNOTSUPP;
        if (!len)
                return 0;
        return master->_lock_user_prot_reg(master, from, len);
}
EXPORT_SYMBOL_GPL(mtd_lock_user_prot_reg);

int mtd_erase_user_prot_reg(struct mtd_info *mtd, loff_t from, size_t len)
{
        struct mtd_info *master = mtd_get_master(mtd);

        if (!master->_erase_user_prot_reg)
                return -EOPNOTSUPP;
        if (!len)
                return 0;
        return master->_erase_user_prot_reg(master, from, len);
}
EXPORT_SYMBOL_GPL(mtd_erase_user_prot_reg);

/* Chip-supported device locking */
int mtd_lock(struct mtd_info *mtd, loff_t ofs, uint64_t len)
{
        struct mtd_info *master = mtd_get_master(mtd);

        if (!master->_lock)
                return -EOPNOTSUPP;
        if (ofs < 0 || ofs >= mtd->size || len > mtd->size - ofs)
                return -EINVAL;
        if (!len)
                return 0;

        if (mtd->flags & MTD_SLC_ON_MLC_EMULATION) {
                ofs = (loff_t)mtd_div_by_eb(ofs, mtd) * master->erasesize;
                len = (u64)mtd_div_by_eb(len, mtd) * master->erasesize;
        }

        return master->_lock(master, mtd_get_master_ofs(mtd, ofs), len);
}
EXPORT_SYMBOL_GPL(mtd_lock);

int mtd_unlock(struct mtd_info *mtd, loff_t ofs, uint64_t len)
{
        struct mtd_info *master = mtd_get_master(mtd);

        if (!master->_unlock)
                return -EOPNOTSUPP;
        if (ofs < 0 || ofs >= mtd->size || len > mtd->size - ofs)
                return -EINVAL;
        if (!len)
                return 0;

        if (mtd->flags & MTD_SLC_ON_MLC_EMULATION) {
                ofs = (loff_t)mtd_div_by_eb(ofs, mtd) * master->erasesize;
                len = (u64)mtd_div_by_eb(len, mtd) * master->erasesize;
        }

        return master->_unlock(master, mtd_get_master_ofs(mtd, ofs), len);
}
EXPORT_SYMBOL_GPL(mtd_unlock);

int mtd_is_locked(struct mtd_info *mtd, loff_t ofs, uint64_t len)
{
        struct mtd_info *master = mtd_get_master(mtd);

        if (!master->_is_locked)
                return -EOPNOTSUPP;
        if (ofs < 0 || ofs >= mtd->size || len > mtd->size - ofs)
                return -EINVAL;
        if (!len)
                return 0;

        if (mtd->flags & MTD_SLC_ON_MLC_EMULATION) {
                ofs = (loff_t)mtd_div_by_eb(ofs, mtd) * master->erasesize;
                len = (u64)mtd_div_by_eb(len, mtd) * master->erasesize;
        }

        return master->_is_locked(master, mtd_get_master_ofs(mtd, ofs), len);
}
EXPORT_SYMBOL_GPL(mtd_is_locked);

int mtd_block_isreserved(struct mtd_info *mtd, loff_t ofs)
{
        struct mtd_info *master = mtd_get_master(mtd);

        if (ofs < 0 || ofs >= mtd->size)
                return -EINVAL;
        if (!master->_block_isreserved)
                return 0;

        if (mtd->flags & MTD_SLC_ON_MLC_EMULATION)
                ofs = (loff_t)mtd_div_by_eb(ofs, mtd) * master->erasesize;

        return master->_block_isreserved(master, mtd_get_master_ofs(mtd, ofs));
}
EXPORT_SYMBOL_GPL(mtd_block_isreserved);

int mtd_block_isbad(struct mtd_info *mtd, loff_t ofs)
{
        struct mtd_info *master = mtd_get_master(mtd);

        if (ofs < 0 || ofs >= mtd->size)
                return -EINVAL;
        if (!master->_block_isbad)
                return 0;

        if (mtd->flags & MTD_SLC_ON_MLC_EMULATION)
                ofs = (loff_t)mtd_div_by_eb(ofs, mtd) * master->erasesize;

        return master->_block_isbad(master, mtd_get_master_ofs(mtd, ofs));
}
EXPORT_SYMBOL_GPL(mtd_block_isbad);

int mtd_block_markbad(struct mtd_info *mtd, loff_t ofs)
{
        struct mtd_info *master = mtd_get_master(mtd);
        int ret;

        if (!master->_block_markbad)
                return -EOPNOTSUPP;
        if (ofs < 0 || ofs >= mtd->size)
                return -EINVAL;
        if (!(mtd->flags & MTD_WRITEABLE))
                return -EROFS;

        if (mtd->flags & MTD_SLC_ON_MLC_EMULATION)
                ofs = (loff_t)mtd_div_by_eb(ofs, mtd) * master->erasesize;

        ret = master->_block_markbad(master, mtd_get_master_ofs(mtd, ofs));
        if (ret)
                return ret;

        while (mtd->parent) {
                mtd->ecc_stats.badblocks++;
                mtd = mtd->parent;
        }

        return 0;
}
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)
{
        struct mtd_info *master = mtd_get_master(mtd);

        *retlen = 0;
        if (!(mtd->flags & MTD_WRITEABLE))
                return -EROFS;

        if (!master->_writev)
                return default_mtd_writev(mtd, vecs, count, to, retlen);

        return master->_writev(master, vecs, count,
                               mtd_get_master_ofs(mtd, 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(const char *name)
{
        struct backing_dev_info *bdi;
        int ret;

        bdi = bdi_alloc(NUMA_NO_NODE);
        if (!bdi)
                return ERR_PTR(-ENOMEM);
        bdi->ra_pages = 0;
        bdi->io_pages = 0;

        /*
         * 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);
        debugfs_create_bool("expert_analysis_mode", 0600, dfs_dir_mtd,
                            &mtd_expert_analysis_mode);

        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_unregister(mtd_bdi);
        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");