block: move down direct IO plugging

[linux/fpc-iii.git] / drivers / mtd / ubi / build.c

/*
 * Copyright (c) International Business Machines Corp., 2006
 * Copyright (c) Nokia Corporation, 2007
 *
 * 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 *
 * Author: Artem Bityutskiy (Битюцкий Артём),
 *         Frank Haverkamp
 */

/*
 * This file includes UBI initialization and building of UBI devices.
 *
 * When UBI is initialized, it attaches all the MTD devices specified as the
 * module load parameters or the kernel boot parameters. If MTD devices were
 * specified, UBI does not attach any MTD device, but it is possible to do
 * later using the "UBI control device".
 */

#include <linux/err.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/stringify.h>
#include <linux/namei.h>
#include <linux/stat.h>
#include <linux/miscdevice.h>
#include <linux/log2.h>
#include <linux/kthread.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include "ubi.h"

/* Maximum length of the 'mtd=' parameter */
#define MTD_PARAM_LEN_MAX 64

#ifdef CONFIG_MTD_UBI_MODULE
#define ubi_is_module() 1
#else
#define ubi_is_module() 0
#endif

/**
 * struct mtd_dev_param - MTD device parameter description data structure.
 * @name: MTD character device node path, MTD device name, or MTD device number
 *        string
 * @vid_hdr_offs: VID header offset
 */
struct mtd_dev_param {
        char name[MTD_PARAM_LEN_MAX];
        int vid_hdr_offs;
};

/* Numbers of elements set in the @mtd_dev_param array */
static int __initdata mtd_devs;

/* MTD devices specification parameters */
static struct mtd_dev_param __initdata mtd_dev_param[UBI_MAX_DEVICES];

/* Root UBI "class" object (corresponds to '/<sysfs>/class/ubi/') */
struct class *ubi_class;

/* Slab cache for wear-leveling entries */
struct kmem_cache *ubi_wl_entry_slab;

/* UBI control character device */
static struct miscdevice ubi_ctrl_cdev = {
        .minor = MISC_DYNAMIC_MINOR,
        .name = "ubi_ctrl",
        .fops = &ubi_ctrl_cdev_operations,
};

/* All UBI devices in system */
static struct ubi_device *ubi_devices[UBI_MAX_DEVICES];

/* Serializes UBI devices creations and removals */
DEFINE_MUTEX(ubi_devices_mutex);

/* Protects @ubi_devices and @ubi->ref_count */
static DEFINE_SPINLOCK(ubi_devices_lock);

/* "Show" method for files in '/<sysfs>/class/ubi/' */
static ssize_t ubi_version_show(struct class *class,
                                struct class_attribute *attr, char *buf)
{
        return sprintf(buf, "%d\n", UBI_VERSION);
}

/* UBI version attribute ('/<sysfs>/class/ubi/version') */
static struct class_attribute ubi_version =
        __ATTR(version, S_IRUGO, ubi_version_show, NULL);

static ssize_t dev_attribute_show(struct device *dev,
                                  struct device_attribute *attr, char *buf);

/* UBI device attributes (correspond to files in '/<sysfs>/class/ubi/ubiX') */
static struct device_attribute dev_eraseblock_size =
        __ATTR(eraseblock_size, S_IRUGO, dev_attribute_show, NULL);
static struct device_attribute dev_avail_eraseblocks =
        __ATTR(avail_eraseblocks, S_IRUGO, dev_attribute_show, NULL);
static struct device_attribute dev_total_eraseblocks =
        __ATTR(total_eraseblocks, S_IRUGO, dev_attribute_show, NULL);
static struct device_attribute dev_volumes_count =
        __ATTR(volumes_count, S_IRUGO, dev_attribute_show, NULL);
static struct device_attribute dev_max_ec =
        __ATTR(max_ec, S_IRUGO, dev_attribute_show, NULL);
static struct device_attribute dev_reserved_for_bad =
        __ATTR(reserved_for_bad, S_IRUGO, dev_attribute_show, NULL);
static struct device_attribute dev_bad_peb_count =
        __ATTR(bad_peb_count, S_IRUGO, dev_attribute_show, NULL);
static struct device_attribute dev_max_vol_count =
        __ATTR(max_vol_count, S_IRUGO, dev_attribute_show, NULL);
static struct device_attribute dev_min_io_size =
        __ATTR(min_io_size, S_IRUGO, dev_attribute_show, NULL);
static struct device_attribute dev_bgt_enabled =
        __ATTR(bgt_enabled, S_IRUGO, dev_attribute_show, NULL);
static struct device_attribute dev_mtd_num =
        __ATTR(mtd_num, S_IRUGO, dev_attribute_show, NULL);

/**
 * ubi_volume_notify - send a volume change notification.
 * @ubi: UBI device description object
 * @vol: volume description object of the changed volume
 * @ntype: notification type to send (%UBI_VOLUME_ADDED, etc)
 *
 * This is a helper function which notifies all subscribers about a volume
 * change event (creation, removal, re-sizing, re-naming, updating). Returns
 * zero in case of success and a negative error code in case of failure.
 */
int ubi_volume_notify(struct ubi_device *ubi, struct ubi_volume *vol, int ntype)
{
        struct ubi_notification nt;

        ubi_do_get_device_info(ubi, &nt.di);
        ubi_do_get_volume_info(ubi, vol, &nt.vi);
        return blocking_notifier_call_chain(&ubi_notifiers, ntype, &nt);
}

/**
 * ubi_notify_all - send a notification to all volumes.
 * @ubi: UBI device description object
 * @ntype: notification type to send (%UBI_VOLUME_ADDED, etc)
 * @nb: the notifier to call
 *
 * This function walks all volumes of UBI device @ubi and sends the @ntype
 * notification for each volume. If @nb is %NULL, then all registered notifiers
 * are called, otherwise only the @nb notifier is called. Returns the number of
 * sent notifications.
 */
int ubi_notify_all(struct ubi_device *ubi, int ntype, struct notifier_block *nb)
{
        struct ubi_notification nt;
        int i, count = 0;

        ubi_do_get_device_info(ubi, &nt.di);

        mutex_lock(&ubi->device_mutex);
        for (i = 0; i < ubi->vtbl_slots; i++) {
                /*
                 * Since the @ubi->device is locked, and we are not going to
                 * change @ubi->volumes, we do not have to lock
                 * @ubi->volumes_lock.
                 */
                if (!ubi->volumes[i])
                        continue;

                ubi_do_get_volume_info(ubi, ubi->volumes[i], &nt.vi);
                if (nb)
                        nb->notifier_call(nb, ntype, &nt);
                else
                        blocking_notifier_call_chain(&ubi_notifiers, ntype,
                                                     &nt);
                count += 1;
        }
        mutex_unlock(&ubi->device_mutex);

        return count;
}

/**
 * ubi_enumerate_volumes - send "add" notification for all existing volumes.
 * @nb: the notifier to call
 *
 * This function walks all UBI devices and volumes and sends the
 * %UBI_VOLUME_ADDED notification for each volume. If @nb is %NULL, then all
 * registered notifiers are called, otherwise only the @nb notifier is called.
 * Returns the number of sent notifications.
 */
int ubi_enumerate_volumes(struct notifier_block *nb)
{
        int i, count = 0;

        /*
         * Since the @ubi_devices_mutex is locked, and we are not going to
         * change @ubi_devices, we do not have to lock @ubi_devices_lock.
         */
        for (i = 0; i < UBI_MAX_DEVICES; i++) {
                struct ubi_device *ubi = ubi_devices[i];

                if (!ubi)
                        continue;
                count += ubi_notify_all(ubi, UBI_VOLUME_ADDED, nb);
        }

        return count;
}

/**
 * ubi_get_device - get UBI device.
 * @ubi_num: UBI device number
 *
 * This function returns UBI device description object for UBI device number
 * @ubi_num, or %NULL if the device does not exist. This function increases the
 * device reference count to prevent removal of the device. In other words, the
 * device cannot be removed if its reference count is not zero.
 */
struct ubi_device *ubi_get_device(int ubi_num)
{
        struct ubi_device *ubi;

        spin_lock(&ubi_devices_lock);
        ubi = ubi_devices[ubi_num];
        if (ubi) {
                ubi_assert(ubi->ref_count >= 0);
                ubi->ref_count += 1;
                get_device(&ubi->dev);
        }
        spin_unlock(&ubi_devices_lock);

        return ubi;
}

/**
 * ubi_put_device - drop an UBI device reference.
 * @ubi: UBI device description object
 */
void ubi_put_device(struct ubi_device *ubi)
{
        spin_lock(&ubi_devices_lock);
        ubi->ref_count -= 1;
        put_device(&ubi->dev);
        spin_unlock(&ubi_devices_lock);
}

/**
 * ubi_get_by_major - get UBI device by character device major number.
 * @major: major number
 *
 * This function is similar to 'ubi_get_device()', but it searches the device
 * by its major number.
 */
struct ubi_device *ubi_get_by_major(int major)
{
        int i;
        struct ubi_device *ubi;

        spin_lock(&ubi_devices_lock);
        for (i = 0; i < UBI_MAX_DEVICES; i++) {
                ubi = ubi_devices[i];
                if (ubi && MAJOR(ubi->cdev.dev) == major) {
                        ubi_assert(ubi->ref_count >= 0);
                        ubi->ref_count += 1;
                        get_device(&ubi->dev);
                        spin_unlock(&ubi_devices_lock);
                        return ubi;
                }
        }
        spin_unlock(&ubi_devices_lock);

        return NULL;
}

/**
 * ubi_major2num - get UBI device number by character device major number.
 * @major: major number
 *
 * This function searches UBI device number object by its major number. If UBI
 * device was not found, this function returns -ENODEV, otherwise the UBI device
 * number is returned.
 */
int ubi_major2num(int major)
{
        int i, ubi_num = -ENODEV;

        spin_lock(&ubi_devices_lock);
        for (i = 0; i < UBI_MAX_DEVICES; i++) {
                struct ubi_device *ubi = ubi_devices[i];

                if (ubi && MAJOR(ubi->cdev.dev) == major) {
                        ubi_num = ubi->ubi_num;
                        break;
                }
        }
        spin_unlock(&ubi_devices_lock);

        return ubi_num;
}

/* "Show" method for files in '/<sysfs>/class/ubi/ubiX/' */
static ssize_t dev_attribute_show(struct device *dev,
                                  struct device_attribute *attr, char *buf)
{
        ssize_t ret;
        struct ubi_device *ubi;

        /*
         * The below code looks weird, but it actually makes sense. We get the
         * UBI device reference from the contained 'struct ubi_device'. But it
         * is unclear if the device was removed or not yet. Indeed, if the
         * device was removed before we increased its reference count,
         * 'ubi_get_device()' will return -ENODEV and we fail.
         *
         * Remember, 'struct ubi_device' is freed in the release function, so
         * we still can use 'ubi->ubi_num'.
         */
        ubi = container_of(dev, struct ubi_device, dev);
        ubi = ubi_get_device(ubi->ubi_num);
        if (!ubi)
                return -ENODEV;

        if (attr == &dev_eraseblock_size)
                ret = sprintf(buf, "%d\n", ubi->leb_size);
        else if (attr == &dev_avail_eraseblocks)
                ret = sprintf(buf, "%d\n", ubi->avail_pebs);
        else if (attr == &dev_total_eraseblocks)
                ret = sprintf(buf, "%d\n", ubi->good_peb_count);
        else if (attr == &dev_volumes_count)
                ret = sprintf(buf, "%d\n", ubi->vol_count - UBI_INT_VOL_COUNT);
        else if (attr == &dev_max_ec)
                ret = sprintf(buf, "%d\n", ubi->max_ec);
        else if (attr == &dev_reserved_for_bad)
                ret = sprintf(buf, "%d\n", ubi->beb_rsvd_pebs);
        else if (attr == &dev_bad_peb_count)
                ret = sprintf(buf, "%d\n", ubi->bad_peb_count);
        else if (attr == &dev_max_vol_count)
                ret = sprintf(buf, "%d\n", ubi->vtbl_slots);
        else if (attr == &dev_min_io_size)
                ret = sprintf(buf, "%d\n", ubi->min_io_size);
        else if (attr == &dev_bgt_enabled)
                ret = sprintf(buf, "%d\n", ubi->thread_enabled);
        else if (attr == &dev_mtd_num)
                ret = sprintf(buf, "%d\n", ubi->mtd->index);
        else
                ret = -EINVAL;

        ubi_put_device(ubi);
        return ret;
}

static void dev_release(struct device *dev)
{
        struct ubi_device *ubi = container_of(dev, struct ubi_device, dev);

        kfree(ubi);
}

/**
 * ubi_sysfs_init - initialize sysfs for an UBI device.
 * @ubi: UBI device description object
 * @ref: set to %1 on exit in case of failure if a reference to @ubi->dev was
 *       taken
 *
 * This function returns zero in case of success and a negative error code in
 * case of failure.
 */
static int ubi_sysfs_init(struct ubi_device *ubi, int *ref)
{
        int err;

        ubi->dev.release = dev_release;
        ubi->dev.devt = ubi->cdev.dev;
        ubi->dev.class = ubi_class;
        dev_set_name(&ubi->dev, UBI_NAME_STR"%d", ubi->ubi_num);
        err = device_register(&ubi->dev);
        if (err)
                return err;

        *ref = 1;
        err = device_create_file(&ubi->dev, &dev_eraseblock_size);
        if (err)
                return err;
        err = device_create_file(&ubi->dev, &dev_avail_eraseblocks);
        if (err)
                return err;
        err = device_create_file(&ubi->dev, &dev_total_eraseblocks);
        if (err)
                return err;
        err = device_create_file(&ubi->dev, &dev_volumes_count);
        if (err)
                return err;
        err = device_create_file(&ubi->dev, &dev_max_ec);
        if (err)
                return err;
        err = device_create_file(&ubi->dev, &dev_reserved_for_bad);
        if (err)
                return err;
        err = device_create_file(&ubi->dev, &dev_bad_peb_count);
        if (err)
                return err;
        err = device_create_file(&ubi->dev, &dev_max_vol_count);
        if (err)
                return err;
        err = device_create_file(&ubi->dev, &dev_min_io_size);
        if (err)
                return err;
        err = device_create_file(&ubi->dev, &dev_bgt_enabled);
        if (err)
                return err;
        err = device_create_file(&ubi->dev, &dev_mtd_num);
        return err;
}

/**
 * ubi_sysfs_close - close sysfs for an UBI device.
 * @ubi: UBI device description object
 */
static void ubi_sysfs_close(struct ubi_device *ubi)
{
        device_remove_file(&ubi->dev, &dev_mtd_num);
        device_remove_file(&ubi->dev, &dev_bgt_enabled);
        device_remove_file(&ubi->dev, &dev_min_io_size);
        device_remove_file(&ubi->dev, &dev_max_vol_count);
        device_remove_file(&ubi->dev, &dev_bad_peb_count);
        device_remove_file(&ubi->dev, &dev_reserved_for_bad);
        device_remove_file(&ubi->dev, &dev_max_ec);
        device_remove_file(&ubi->dev, &dev_volumes_count);
        device_remove_file(&ubi->dev, &dev_total_eraseblocks);
        device_remove_file(&ubi->dev, &dev_avail_eraseblocks);
        device_remove_file(&ubi->dev, &dev_eraseblock_size);
        device_unregister(&ubi->dev);
}

/**
 * kill_volumes - destroy all user volumes.
 * @ubi: UBI device description object
 */
static void kill_volumes(struct ubi_device *ubi)
{
        int i;

        for (i = 0; i < ubi->vtbl_slots; i++)
                if (ubi->volumes[i])
                        ubi_free_volume(ubi, ubi->volumes[i]);
}

/**
 * uif_init - initialize user interfaces for an UBI device.
 * @ubi: UBI device description object
 * @ref: set to %1 on exit in case of failure if a reference to @ubi->dev was
 *       taken, otherwise set to %0
 *
 * This function initializes various user interfaces for an UBI device. If the
 * initialization fails at an early stage, this function frees all the
 * resources it allocated, returns an error, and @ref is set to %0. However,
 * if the initialization fails after the UBI device was registered in the
 * driver core subsystem, this function takes a reference to @ubi->dev, because
 * otherwise the release function ('dev_release()') would free whole @ubi
 * object. The @ref argument is set to %1 in this case. The caller has to put
 * this reference.
 *
 * This function returns zero in case of success and a negative error code in
 * case of failure.
 */
static int uif_init(struct ubi_device *ubi, int *ref)
{
        int i, err;
        dev_t dev;

        *ref = 0;
        sprintf(ubi->ubi_name, UBI_NAME_STR "%d", ubi->ubi_num);

        /*
         * Major numbers for the UBI character devices are allocated
         * dynamically. Major numbers of volume character devices are
         * equivalent to ones of the corresponding UBI character device. Minor
         * numbers of UBI character devices are 0, while minor numbers of
         * volume character devices start from 1. Thus, we allocate one major
         * number and ubi->vtbl_slots + 1 minor numbers.
         */
        err = alloc_chrdev_region(&dev, 0, ubi->vtbl_slots + 1, ubi->ubi_name);
        if (err) {
                ubi_err("cannot register UBI character devices");
                return err;
        }

        ubi_assert(MINOR(dev) == 0);
        cdev_init(&ubi->cdev, &ubi_cdev_operations);
        dbg_gen("%s major is %u", ubi->ubi_name, MAJOR(dev));
        ubi->cdev.owner = THIS_MODULE;

        err = cdev_add(&ubi->cdev, dev, 1);
        if (err) {
                ubi_err("cannot add character device");
                goto out_unreg;
        }

        err = ubi_sysfs_init(ubi, ref);
        if (err)
                goto out_sysfs;

        for (i = 0; i < ubi->vtbl_slots; i++)
                if (ubi->volumes[i]) {
                        err = ubi_add_volume(ubi, ubi->volumes[i]);
                        if (err) {
                                ubi_err("cannot add volume %d", i);
                                goto out_volumes;
                        }
                }

        return 0;

out_volumes:
        kill_volumes(ubi);
out_sysfs:
        if (*ref)
                get_device(&ubi->dev);
        ubi_sysfs_close(ubi);
        cdev_del(&ubi->cdev);
out_unreg:
        unregister_chrdev_region(ubi->cdev.dev, ubi->vtbl_slots + 1);
        ubi_err("cannot initialize UBI %s, error %d", ubi->ubi_name, err);
        return err;
}

/**
 * uif_close - close user interfaces for an UBI device.
 * @ubi: UBI device description object
 *
 * Note, since this function un-registers UBI volume device objects (@vol->dev),
 * the memory allocated voe the volumes is freed as well (in the release
 * function).
 */
static void uif_close(struct ubi_device *ubi)
{
        kill_volumes(ubi);
        ubi_sysfs_close(ubi);
        cdev_del(&ubi->cdev);
        unregister_chrdev_region(ubi->cdev.dev, ubi->vtbl_slots + 1);
}

/**
 * ubi_free_internal_volumes - free internal volumes.
 * @ubi: UBI device description object
 */
void ubi_free_internal_volumes(struct ubi_device *ubi)
{
        int i;

        for (i = ubi->vtbl_slots;
             i < ubi->vtbl_slots + UBI_INT_VOL_COUNT; i++) {
                kfree(ubi->volumes[i]->eba_tbl);
                kfree(ubi->volumes[i]);
        }
}

/**
 * io_init - initialize I/O sub-system for a given UBI device.
 * @ubi: UBI device description object
 *
 * If @ubi->vid_hdr_offset or @ubi->leb_start is zero, default offsets are
 * assumed:
 *   o EC header is always at offset zero - this cannot be changed;
 *   o VID header starts just after the EC header at the closest address
 *     aligned to @io->hdrs_min_io_size;
 *   o data starts just after the VID header at the closest address aligned to
 *     @io->min_io_size
 *
 * This function returns zero in case of success and a negative error code in
 * case of failure.
 */
static int io_init(struct ubi_device *ubi)
{
        if (ubi->mtd->numeraseregions != 0) {
                /*
                 * Some flashes have several erase regions. Different regions
                 * may have different eraseblock size and other
                 * characteristics. It looks like mostly multi-region flashes
                 * have one "main" region and one or more small regions to
                 * store boot loader code or boot parameters or whatever. I
                 * guess we should just pick the largest region. But this is
                 * not implemented.
                 */
                ubi_err("multiple regions, not implemented");
                return -EINVAL;
        }

        if (ubi->vid_hdr_offset < 0)
                return -EINVAL;

        /*
         * Note, in this implementation we support MTD devices with 0x7FFFFFFF
         * physical eraseblocks maximum.
         */

        ubi->peb_size   = ubi->mtd->erasesize;
        ubi->peb_count  = mtd_div_by_eb(ubi->mtd->size, ubi->mtd);
        ubi->flash_size = ubi->mtd->size;

        if (mtd_can_have_bb(ubi->mtd))
                ubi->bad_allowed = 1;

        if (ubi->mtd->type == MTD_NORFLASH) {
                ubi_assert(ubi->mtd->writesize == 1);
                ubi->nor_flash = 1;
        }

        ubi->min_io_size = ubi->mtd->writesize;
        ubi->hdrs_min_io_size = ubi->mtd->writesize >> ubi->mtd->subpage_sft;

        /*
         * Make sure minimal I/O unit is power of 2. Note, there is no
         * fundamental reason for this assumption. It is just an optimization
         * which allows us to avoid costly division operations.
         */
        if (!is_power_of_2(ubi->min_io_size)) {
                ubi_err("min. I/O unit (%d) is not power of 2",
                        ubi->min_io_size);
                return -EINVAL;
        }

        ubi_assert(ubi->hdrs_min_io_size > 0);
        ubi_assert(ubi->hdrs_min_io_size <= ubi->min_io_size);
        ubi_assert(ubi->min_io_size % ubi->hdrs_min_io_size == 0);

        ubi->max_write_size = ubi->mtd->writebufsize;
        /*
         * Maximum write size has to be greater or equivalent to min. I/O
         * size, and be multiple of min. I/O size.
         */
        if (ubi->max_write_size < ubi->min_io_size ||
            ubi->max_write_size % ubi->min_io_size ||
            !is_power_of_2(ubi->max_write_size)) {
                ubi_err("bad write buffer size %d for %d min. I/O unit",
                        ubi->max_write_size, ubi->min_io_size);
                return -EINVAL;
        }

        /* Calculate default aligned sizes of EC and VID headers */
        ubi->ec_hdr_alsize = ALIGN(UBI_EC_HDR_SIZE, ubi->hdrs_min_io_size);
        ubi->vid_hdr_alsize = ALIGN(UBI_VID_HDR_SIZE, ubi->hdrs_min_io_size);

        dbg_msg("min_io_size      %d", ubi->min_io_size);
        dbg_msg("max_write_size   %d", ubi->max_write_size);
        dbg_msg("hdrs_min_io_size %d", ubi->hdrs_min_io_size);
        dbg_msg("ec_hdr_alsize    %d", ubi->ec_hdr_alsize);
        dbg_msg("vid_hdr_alsize   %d", ubi->vid_hdr_alsize);

        if (ubi->vid_hdr_offset == 0)
                /* Default offset */
                ubi->vid_hdr_offset = ubi->vid_hdr_aloffset =
                                      ubi->ec_hdr_alsize;
        else {
                ubi->vid_hdr_aloffset = ubi->vid_hdr_offset &
                                                ~(ubi->hdrs_min_io_size - 1);
                ubi->vid_hdr_shift = ubi->vid_hdr_offset -
                                                ubi->vid_hdr_aloffset;
        }

        /* Similar for the data offset */
        ubi->leb_start = ubi->vid_hdr_offset + UBI_VID_HDR_SIZE;
        ubi->leb_start = ALIGN(ubi->leb_start, ubi->min_io_size);

        dbg_msg("vid_hdr_offset   %d", ubi->vid_hdr_offset);
        dbg_msg("vid_hdr_aloffset %d", ubi->vid_hdr_aloffset);
        dbg_msg("vid_hdr_shift    %d", ubi->vid_hdr_shift);
        dbg_msg("leb_start        %d", ubi->leb_start);

        /* The shift must be aligned to 32-bit boundary */
        if (ubi->vid_hdr_shift % 4) {
                ubi_err("unaligned VID header shift %d",
                        ubi->vid_hdr_shift);
                return -EINVAL;
        }

        /* Check sanity */
        if (ubi->vid_hdr_offset < UBI_EC_HDR_SIZE ||
            ubi->leb_start < ubi->vid_hdr_offset + UBI_VID_HDR_SIZE ||
            ubi->leb_start > ubi->peb_size - UBI_VID_HDR_SIZE ||
            ubi->leb_start & (ubi->min_io_size - 1)) {
                ubi_err("bad VID header (%d) or data offsets (%d)",
                        ubi->vid_hdr_offset, ubi->leb_start);
                return -EINVAL;
        }

        /*
         * Set maximum amount of physical erroneous eraseblocks to be 10%.
         * Erroneous PEB are those which have read errors.
         */
        ubi->max_erroneous = ubi->peb_count / 10;
        if (ubi->max_erroneous < 16)
                ubi->max_erroneous = 16;
        dbg_msg("max_erroneous    %d", ubi->max_erroneous);

        /*
         * It may happen that EC and VID headers are situated in one minimal
         * I/O unit. In this case we can only accept this UBI image in
         * read-only mode.
         */
        if (ubi->vid_hdr_offset + UBI_VID_HDR_SIZE <= ubi->hdrs_min_io_size) {
                ubi_warn("EC and VID headers are in the same minimal I/O unit, "
                         "switch to read-only mode");
                ubi->ro_mode = 1;
        }

        ubi->leb_size = ubi->peb_size - ubi->leb_start;

        if (!(ubi->mtd->flags & MTD_WRITEABLE)) {
                ubi_msg("MTD device %d is write-protected, attach in "
                        "read-only mode", ubi->mtd->index);
                ubi->ro_mode = 1;
        }

        ubi_msg("physical eraseblock size:   %d bytes (%d KiB)",
                ubi->peb_size, ubi->peb_size >> 10);
        ubi_msg("logical eraseblock size:    %d bytes", ubi->leb_size);
        ubi_msg("smallest flash I/O unit:    %d", ubi->min_io_size);
        if (ubi->hdrs_min_io_size != ubi->min_io_size)
                ubi_msg("sub-page size:              %d",
                        ubi->hdrs_min_io_size);
        ubi_msg("VID header offset:          %d (aligned %d)",
                ubi->vid_hdr_offset, ubi->vid_hdr_aloffset);
        ubi_msg("data offset:                %d", ubi->leb_start);

        /*
         * Note, ideally, we have to initialize @ubi->bad_peb_count here. But
         * unfortunately, MTD does not provide this information. We should loop
         * over all physical eraseblocks and invoke mtd->block_is_bad() for
         * each physical eraseblock. So, we leave @ubi->bad_peb_count
         * uninitialized so far.
         */

        return 0;
}

/**
 * autoresize - re-size the volume which has the "auto-resize" flag set.
 * @ubi: UBI device description object
 * @vol_id: ID of the volume to re-size
 *
 * This function re-sizes the volume marked by the %UBI_VTBL_AUTORESIZE_FLG in
 * the volume table to the largest possible size. See comments in ubi-header.h
 * for more description of the flag. Returns zero in case of success and a
 * negative error code in case of failure.
 */
static int autoresize(struct ubi_device *ubi, int vol_id)
{
        struct ubi_volume_desc desc;
        struct ubi_volume *vol = ubi->volumes[vol_id];
        int err, old_reserved_pebs = vol->reserved_pebs;

        /*
         * Clear the auto-resize flag in the volume in-memory copy of the
         * volume table, and 'ubi_resize_volume()' will propagate this change
         * to the flash.
         */
        ubi->vtbl[vol_id].flags &= ~UBI_VTBL_AUTORESIZE_FLG;

        if (ubi->avail_pebs == 0) {
                struct ubi_vtbl_record vtbl_rec;

                /*
                 * No available PEBs to re-size the volume, clear the flag on
                 * flash and exit.
                 */
                memcpy(&vtbl_rec, &ubi->vtbl[vol_id],
                       sizeof(struct ubi_vtbl_record));
                err = ubi_change_vtbl_record(ubi, vol_id, &vtbl_rec);
                if (err)
                        ubi_err("cannot clean auto-resize flag for volume %d",
                                vol_id);
        } else {
                desc.vol = vol;
                err = ubi_resize_volume(&desc,
                                        old_reserved_pebs + ubi->avail_pebs);
                if (err)
                        ubi_err("cannot auto-resize volume %d", vol_id);
        }

        if (err)
                return err;

        ubi_msg("volume %d (\"%s\") re-sized from %d to %d LEBs", vol_id,
                vol->name, old_reserved_pebs, vol->reserved_pebs);
        return 0;
}

/**
 * ubi_attach_mtd_dev - attach an MTD device.
 * @mtd: MTD device description object
 * @ubi_num: number to assign to the new UBI device
 * @vid_hdr_offset: VID header offset
 *
 * This function attaches MTD device @mtd_dev to UBI and assign @ubi_num number
 * to the newly created UBI device, unless @ubi_num is %UBI_DEV_NUM_AUTO, in
 * which case this function finds a vacant device number and assigns it
 * automatically. Returns the new UBI device number in case of success and a
 * negative error code in case of failure.
 *
 * Note, the invocations of this function has to be serialized by the
 * @ubi_devices_mutex.
 */
int ubi_attach_mtd_dev(struct mtd_info *mtd, int ubi_num, int vid_hdr_offset)
{
        struct ubi_device *ubi;
        int i, err, ref = 0;

        /*
         * Check if we already have the same MTD device attached.
         *
         * Note, this function assumes that UBI devices creations and deletions
         * are serialized, so it does not take the &ubi_devices_lock.
         */
        for (i = 0; i < UBI_MAX_DEVICES; i++) {
                ubi = ubi_devices[i];
                if (ubi && mtd->index == ubi->mtd->index) {
                        ubi_err("mtd%d is already attached to ubi%d",
                                mtd->index, i);
                        return -EEXIST;
                }
        }

        /*
         * Make sure this MTD device is not emulated on top of an UBI volume
         * already. Well, generally this recursion works fine, but there are
         * different problems like the UBI module takes a reference to itself
         * by attaching (and thus, opening) the emulated MTD device. This
         * results in inability to unload the module. And in general it makes
         * no sense to attach emulated MTD devices, so we prohibit this.
         */
        if (mtd->type == MTD_UBIVOLUME) {
                ubi_err("refuse attaching mtd%d - it is already emulated on "
                        "top of UBI", mtd->index);
                return -EINVAL;
        }

        if (ubi_num == UBI_DEV_NUM_AUTO) {
                /* Search for an empty slot in the @ubi_devices array */
                for (ubi_num = 0; ubi_num < UBI_MAX_DEVICES; ubi_num++)
                        if (!ubi_devices[ubi_num])
                                break;
                if (ubi_num == UBI_MAX_DEVICES) {
                        ubi_err("only %d UBI devices may be created",
                                UBI_MAX_DEVICES);
                        return -ENFILE;
                }
        } else {
                if (ubi_num >= UBI_MAX_DEVICES)
                        return -EINVAL;

                /* Make sure ubi_num is not busy */
                if (ubi_devices[ubi_num]) {
                        ubi_err("ubi%d already exists", ubi_num);
                        return -EEXIST;
                }
        }

        ubi = kzalloc(sizeof(struct ubi_device), GFP_KERNEL);
        if (!ubi)
                return -ENOMEM;

        ubi->mtd = mtd;
        ubi->ubi_num = ubi_num;
        ubi->vid_hdr_offset = vid_hdr_offset;
        ubi->autoresize_vol_id = -1;

        mutex_init(&ubi->buf_mutex);
        mutex_init(&ubi->ckvol_mutex);
        mutex_init(&ubi->device_mutex);
        spin_lock_init(&ubi->volumes_lock);

        ubi_msg("attaching mtd%d to ubi%d", mtd->index, ubi_num);
        dbg_msg("sizeof(struct ubi_ainf_peb) %zu", sizeof(struct ubi_ainf_peb));
        dbg_msg("sizeof(struct ubi_wl_entry) %zu", sizeof(struct ubi_wl_entry));

        err = io_init(ubi);
        if (err)
                goto out_free;

        err = -ENOMEM;
        ubi->peb_buf = vmalloc(ubi->peb_size);
        if (!ubi->peb_buf)
                goto out_free;

        err = ubi_debugging_init_dev(ubi);
        if (err)
                goto out_free;

        err = ubi_attach(ubi);
        if (err) {
                ubi_err("failed to attach mtd%d, error %d", mtd->index, err);
                goto out_debugging;
        }

        if (ubi->autoresize_vol_id != -1) {
                err = autoresize(ubi, ubi->autoresize_vol_id);
                if (err)
                        goto out_detach;
        }

        err = uif_init(ubi, &ref);
        if (err)
                goto out_detach;

        err = ubi_debugfs_init_dev(ubi);
        if (err)
                goto out_uif;

        ubi->bgt_thread = kthread_create(ubi_thread, ubi, ubi->bgt_name);
        if (IS_ERR(ubi->bgt_thread)) {
                err = PTR_ERR(ubi->bgt_thread);
                ubi_err("cannot spawn \"%s\", error %d", ubi->bgt_name,
                        err);
                goto out_debugfs;
        }

        ubi_msg("attached mtd%d to ubi%d", mtd->index, ubi_num);
        ubi_msg("MTD device name:            \"%s\"", mtd->name);
        ubi_msg("MTD device size:            %llu MiB", ubi->flash_size >> 20);
        ubi_msg("number of good PEBs:        %d", ubi->good_peb_count);
        ubi_msg("number of bad PEBs:         %d", ubi->bad_peb_count);
        ubi_msg("number of corrupted PEBs:   %d", ubi->corr_peb_count);
        ubi_msg("max. allowed volumes:       %d", ubi->vtbl_slots);
        ubi_msg("wear-leveling threshold:    %d", CONFIG_MTD_UBI_WL_THRESHOLD);
        ubi_msg("number of internal volumes: %d", UBI_INT_VOL_COUNT);
        ubi_msg("number of user volumes:     %d",
                ubi->vol_count - UBI_INT_VOL_COUNT);
        ubi_msg("available PEBs:             %d", ubi->avail_pebs);
        ubi_msg("total number of reserved PEBs: %d", ubi->rsvd_pebs);
        ubi_msg("number of PEBs reserved for bad PEB handling: %d",
                ubi->beb_rsvd_pebs);
        ubi_msg("max/mean erase counter: %d/%d", ubi->max_ec, ubi->mean_ec);
        ubi_msg("image sequence number:  %d", ubi->image_seq);

        /*
         * The below lock makes sure we do not race with 'ubi_thread()' which
         * checks @ubi->thread_enabled. Otherwise we may fail to wake it up.
         */
        spin_lock(&ubi->wl_lock);
        ubi->thread_enabled = 1;
        wake_up_process(ubi->bgt_thread);
        spin_unlock(&ubi->wl_lock);

        ubi_devices[ubi_num] = ubi;
        ubi_notify_all(ubi, UBI_VOLUME_ADDED, NULL);
        return ubi_num;

out_debugfs:
        ubi_debugfs_exit_dev(ubi);
out_uif:
        get_device(&ubi->dev);
        ubi_assert(ref);
        uif_close(ubi);
out_detach:
        ubi_wl_close(ubi);
        ubi_free_internal_volumes(ubi);
        vfree(ubi->vtbl);
out_debugging:
        ubi_debugging_exit_dev(ubi);
out_free:
        vfree(ubi->peb_buf);
        if (ref)
                put_device(&ubi->dev);
        else
                kfree(ubi);
        return err;
}

/**
 * ubi_detach_mtd_dev - detach an MTD device.
 * @ubi_num: UBI device number to detach from
 * @anyway: detach MTD even if device reference count is not zero
 *
 * This function destroys an UBI device number @ubi_num and detaches the
 * underlying MTD device. Returns zero in case of success and %-EBUSY if the
 * UBI device is busy and cannot be destroyed, and %-EINVAL if it does not
 * exist.
 *
 * Note, the invocations of this function has to be serialized by the
 * @ubi_devices_mutex.
 */
int ubi_detach_mtd_dev(int ubi_num, int anyway)
{
        struct ubi_device *ubi;

        if (ubi_num < 0 || ubi_num >= UBI_MAX_DEVICES)
                return -EINVAL;

        ubi = ubi_get_device(ubi_num);
        if (!ubi)
                return -EINVAL;

        spin_lock(&ubi_devices_lock);
        put_device(&ubi->dev);
        ubi->ref_count -= 1;
        if (ubi->ref_count) {
                if (!anyway) {
                        spin_unlock(&ubi_devices_lock);
                        return -EBUSY;
                }
                /* This may only happen if there is a bug */
                ubi_err("%s reference count %d, destroy anyway",
                        ubi->ubi_name, ubi->ref_count);
        }
        ubi_devices[ubi_num] = NULL;
        spin_unlock(&ubi_devices_lock);

        ubi_assert(ubi_num == ubi->ubi_num);
        ubi_notify_all(ubi, UBI_VOLUME_REMOVED, NULL);
        dbg_msg("detaching mtd%d from ubi%d", ubi->mtd->index, ubi_num);

        /*
         * Before freeing anything, we have to stop the background thread to
         * prevent it from doing anything on this device while we are freeing.
         */
        if (ubi->bgt_thread)
                kthread_stop(ubi->bgt_thread);

        /*
         * Get a reference to the device in order to prevent 'dev_release()'
         * from freeing the @ubi object.
         */
        get_device(&ubi->dev);

        ubi_debugfs_exit_dev(ubi);
        uif_close(ubi);
        ubi_wl_close(ubi);
        ubi_free_internal_volumes(ubi);
        vfree(ubi->vtbl);
        put_mtd_device(ubi->mtd);
        ubi_debugging_exit_dev(ubi);
        vfree(ubi->peb_buf);
        ubi_msg("mtd%d is detached from ubi%d", ubi->mtd->index, ubi->ubi_num);
        put_device(&ubi->dev);
        return 0;
}

/**
 * open_mtd_by_chdev - open an MTD device by its character device node path.
 * @mtd_dev: MTD character device node path
 *
 * This helper function opens an MTD device by its character node device path.
 * Returns MTD device description object in case of success and a negative
 * error code in case of failure.
 */
static struct mtd_info * __init open_mtd_by_chdev(const char *mtd_dev)
{
        int err, major, minor, mode;
        struct path path;

        /* Probably this is an MTD character device node path */
        err = kern_path(mtd_dev, LOOKUP_FOLLOW, &path);
        if (err)
                return ERR_PTR(err);

        /* MTD device number is defined by the major / minor numbers */
        major = imajor(path.dentry->d_inode);
        minor = iminor(path.dentry->d_inode);
        mode = path.dentry->d_inode->i_mode;
        path_put(&path);
        if (major != MTD_CHAR_MAJOR || !S_ISCHR(mode))
                return ERR_PTR(-EINVAL);

        if (minor & 1)
                /*
                 * Just do not think the "/dev/mtdrX" devices support is need,
                 * so do not support them to avoid doing extra work.
                 */
                return ERR_PTR(-EINVAL);

        return get_mtd_device(NULL, minor / 2);
}

/**
 * open_mtd_device - open MTD device by name, character device path, or number.
 * @mtd_dev: name, character device node path, or MTD device device number
 *
 * This function tries to open and MTD device described by @mtd_dev string,
 * which is first treated as ASCII MTD device number, and if it is not true, it
 * is treated as MTD device name, and if that is also not true, it is treated
 * as MTD character device node path. Returns MTD device description object in
 * case of success and a negative error code in case of failure.
 */
static struct mtd_info * __init open_mtd_device(const char *mtd_dev)
{
        struct mtd_info *mtd;
        int mtd_num;
        char *endp;

        mtd_num = simple_strtoul(mtd_dev, &endp, 0);
        if (*endp != '\0' || mtd_dev == endp) {
                /*
                 * This does not look like an ASCII integer, probably this is
                 * MTD device name.
                 */
                mtd = get_mtd_device_nm(mtd_dev);
                if (IS_ERR(mtd) && PTR_ERR(mtd) == -ENODEV)
                        /* Probably this is an MTD character device node path */
                        mtd = open_mtd_by_chdev(mtd_dev);
        } else
                mtd = get_mtd_device(NULL, mtd_num);

        return mtd;
}

static int __init ubi_init(void)
{
        int err, i, k;

        /* Ensure that EC and VID headers have correct size */
        BUILD_BUG_ON(sizeof(struct ubi_ec_hdr) != 64);
        BUILD_BUG_ON(sizeof(struct ubi_vid_hdr) != 64);

        if (mtd_devs > UBI_MAX_DEVICES) {
                ubi_err("too many MTD devices, maximum is %d", UBI_MAX_DEVICES);
                return -EINVAL;
        }

        /* Create base sysfs directory and sysfs files */
        ubi_class = class_create(THIS_MODULE, UBI_NAME_STR);
        if (IS_ERR(ubi_class)) {
                err = PTR_ERR(ubi_class);
                ubi_err("cannot create UBI class");
                goto out;
        }

        err = class_create_file(ubi_class, &ubi_version);
        if (err) {
                ubi_err("cannot create sysfs file");
                goto out_class;
        }

        err = misc_register(&ubi_ctrl_cdev);
        if (err) {
                ubi_err("cannot register device");
                goto out_version;
        }

        ubi_wl_entry_slab = kmem_cache_create("ubi_wl_entry_slab",
                                              sizeof(struct ubi_wl_entry),
                                              0, 0, NULL);
        if (!ubi_wl_entry_slab)
                goto out_dev_unreg;

        err = ubi_debugfs_init();
        if (err)
                goto out_slab;


        /* Attach MTD devices */
        for (i = 0; i < mtd_devs; i++) {
                struct mtd_dev_param *p = &mtd_dev_param[i];
                struct mtd_info *mtd;

                cond_resched();

                mtd = open_mtd_device(p->name);
                if (IS_ERR(mtd)) {
                        err = PTR_ERR(mtd);
                        goto out_detach;
                }

                mutex_lock(&ubi_devices_mutex);
                err = ubi_attach_mtd_dev(mtd, UBI_DEV_NUM_AUTO,
                                         p->vid_hdr_offs);
                mutex_unlock(&ubi_devices_mutex);
                if (err < 0) {
                        ubi_err("cannot attach mtd%d", mtd->index);
                        put_mtd_device(mtd);

                        /*
                         * Originally UBI stopped initializing on any error.
                         * However, later on it was found out that this
                         * behavior is not very good when UBI is compiled into
                         * the kernel and the MTD devices to attach are passed
                         * through the command line. Indeed, UBI failure
                         * stopped whole boot sequence.
                         *
                         * To fix this, we changed the behavior for the
                         * non-module case, but preserved the old behavior for
                         * the module case, just for compatibility. This is a
                         * little inconsistent, though.
                         */
                        if (ubi_is_module())
                                goto out_detach;
                }
        }

        return 0;

out_detach:
        for (k = 0; k < i; k++)
                if (ubi_devices[k]) {
                        mutex_lock(&ubi_devices_mutex);
                        ubi_detach_mtd_dev(ubi_devices[k]->ubi_num, 1);
                        mutex_unlock(&ubi_devices_mutex);
                }
        ubi_debugfs_exit();
out_slab:
        kmem_cache_destroy(ubi_wl_entry_slab);
out_dev_unreg:
        misc_deregister(&ubi_ctrl_cdev);
out_version:
        class_remove_file(ubi_class, &ubi_version);
out_class:
        class_destroy(ubi_class);
out:
        ubi_err("UBI error: cannot initialize UBI, error %d", err);
        return err;
}
module_init(ubi_init);

static void __exit ubi_exit(void)
{
        int i;

        for (i = 0; i < UBI_MAX_DEVICES; i++)
                if (ubi_devices[i]) {
                        mutex_lock(&ubi_devices_mutex);
                        ubi_detach_mtd_dev(ubi_devices[i]->ubi_num, 1);
                        mutex_unlock(&ubi_devices_mutex);
                }
        ubi_debugfs_exit();
        kmem_cache_destroy(ubi_wl_entry_slab);
        misc_deregister(&ubi_ctrl_cdev);
        class_remove_file(ubi_class, &ubi_version);
        class_destroy(ubi_class);
}
module_exit(ubi_exit);

/**
 * bytes_str_to_int - convert a number of bytes string into an integer.
 * @str: the string to convert
 *
 * This function returns positive resulting integer in case of success and a
 * negative error code in case of failure.
 */
static int __init bytes_str_to_int(const char *str)
{
        char *endp;
        unsigned long result;

        result = simple_strtoul(str, &endp, 0);
        if (str == endp || result >= INT_MAX) {
                printk(KERN_ERR "UBI error: incorrect bytes count: \"%s\"\n",
                       str);
                return -EINVAL;
        }

        switch (*endp) {
        case 'G':
                result *= 1024;
        case 'M':
                result *= 1024;
        case 'K':
                result *= 1024;
                if (endp[1] == 'i' && endp[2] == 'B')
                        endp += 2;
        case '\0':
                break;
        default:
                printk(KERN_ERR "UBI error: incorrect bytes count: \"%s\"\n",
                       str);
                return -EINVAL;
        }

        return result;
}

/**
 * ubi_mtd_param_parse - parse the 'mtd=' UBI parameter.
 * @val: the parameter value to parse
 * @kp: not used
 *
 * This function returns zero in case of success and a negative error code in
 * case of error.
 */
static int __init ubi_mtd_param_parse(const char *val, struct kernel_param *kp)
{
        int i, len;
        struct mtd_dev_param *p;
        char buf[MTD_PARAM_LEN_MAX];
        char *pbuf = &buf[0];
        char *tokens[2] = {NULL, NULL};

        if (!val)
                return -EINVAL;

        if (mtd_devs == UBI_MAX_DEVICES) {
                printk(KERN_ERR "UBI error: too many parameters, max. is %d\n",
                       UBI_MAX_DEVICES);
                return -EINVAL;
        }

        len = strnlen(val, MTD_PARAM_LEN_MAX);
        if (len == MTD_PARAM_LEN_MAX) {
                printk(KERN_ERR "UBI error: parameter \"%s\" is too long, "
                       "max. is %d\n", val, MTD_PARAM_LEN_MAX);
                return -EINVAL;
        }

        if (len == 0) {
                printk(KERN_WARNING "UBI warning: empty 'mtd=' parameter - "
                       "ignored\n");
                return 0;
        }

        strcpy(buf, val);

        /* Get rid of the final newline */
        if (buf[len - 1] == '\n')
                buf[len - 1] = '\0';

        for (i = 0; i < 2; i++)
                tokens[i] = strsep(&pbuf, ",");

        if (pbuf) {
                printk(KERN_ERR "UBI error: too many arguments at \"%s\"\n",
                       val);
                return -EINVAL;
        }

        p = &mtd_dev_param[mtd_devs];
        strcpy(&p->name[0], tokens[0]);

        if (tokens[1])
                p->vid_hdr_offs = bytes_str_to_int(tokens[1]);

        if (p->vid_hdr_offs < 0)
                return p->vid_hdr_offs;

        mtd_devs += 1;
        return 0;
}

module_param_call(mtd, ubi_mtd_param_parse, NULL, NULL, 000);
MODULE_PARM_DESC(mtd, "MTD devices to attach. Parameter format: "
                      "mtd=<name|num|path>[,<vid_hdr_offs>].\n"
                      "Multiple \"mtd\" parameters may be specified.\n"
                      "MTD devices may be specified by their number, name, or "
                      "path to the MTD character device node.\n"
                      "Optional \"vid_hdr_offs\" parameter specifies UBI VID "
                      "header position to be used by UBI.\n"
                      "Example 1: mtd=/dev/mtd0 - attach MTD device "
                      "/dev/mtd0.\n"
                      "Example 2: mtd=content,1984 mtd=4 - attach MTD device "
                      "with name \"content\" using VID header offset 1984, and "
                      "MTD device number 4 with default VID header offset.");

MODULE_VERSION(__stringify(UBI_VERSION));
MODULE_DESCRIPTION("UBI - Unsorted Block Images");
MODULE_AUTHOR("Artem Bityutskiy");
MODULE_LICENSE("GPL");