UBI: Unsorted Block Images

UBI (Latin: "where?") manages multiple logical volumes on a single
flash device, specifically supporting NAND flash devices. UBI provides
a flexible partitioning concept which still allows for wear-levelling
across the whole flash device.

In a sense, UBI may be compared to the Logical Volume Manager
(LVM). Whereas LVM maps logical sector numbers to physical HDD sector
numbers, UBI maps logical eraseblocks to physical eraseblocks.

More information may be found at
http://www.linux-mtd.infradead.org/doc/ubi.html

Partitioning/Re-partitioning

  An UBI volume occupies a certain number of erase blocks. This is
  limited by a configured maximum volume size, which could also be
  viewed as the partition size. Each individual UBI volume's size can
  be changed independently of the other UBI volumes, provided that the
  sum of all volume sizes doesn't exceed a certain limit.

  UBI supports dynamic volumes and static volumes. Static volumes are
  read-only and their contents are protected by CRC check sums.

Bad eraseblocks handling

  UBI transparently handles bad eraseblocks. When a physical
  eraseblock becomes bad, it is substituted by a good physical
  eraseblock, and the user does not even notice this.

Scrubbing

  On a NAND flash bit flips can occur on any write operation,
  sometimes also on read. If bit flips persist on the device, at first
  they can still be corrected by ECC, but once they accumulate,
  correction will become impossible. Thus it is best to actively scrub
  the affected eraseblock, by first copying it to a free eraseblock
  and then erasing the original. The UBI layer performs this type of
  scrubbing under the covers, transparently to the UBI volume users.

Erase Counts

  UBI maintains an erase count header per eraseblock. This frees
  higher-level layers (like file systems) from doing this and allows
  for centralized erase count management instead. The erase counts are
  used by the wear-levelling algorithm in the UBI layer. The algorithm
  itself is exchangeable.

Booting from NAND

  For booting directly from NAND flash the hardware must at least be
  capable of fetching and executing a small portion of the NAND
  flash. Some NAND flash controllers have this kind of support. They
  usually limit the window to a few kilobytes in erase block 0. This
  "initial program loader" (IPL) must then contain sufficient logic to
  load and execute the next boot phase.

  Due to bad eraseblocks, which may be randomly scattered over the
  flash device, it is problematic to store the "secondary program
  loader" (SPL) statically. Also, due to bit-flips it may become
  corrupted over time. UBI allows to solve this problem gracefully by
  storing the SPL in a small static UBI volume.

UBI volumes vs. static partitions

  UBI volumes are still very similar to static MTD partitions:

    * both consist of eraseblocks (logical eraseblocks in case of UBI
      volumes, and physical eraseblocks in case of static partitions;
    * both support three basic operations - read, write, erase.

  But UBI volumes have the following advantages over traditional
  static MTD partitions:

    * there are no eraseblock wear-leveling constraints in case of UBI
      volumes, so the user should not care about this;
    * there are no bit-flips and bad eraseblocks in case of UBI volumes.

  So, UBI volumes may be considered as flash devices with relaxed
  restrictions.

Where can it be found?

  Documentation, kernel code and applications can be found in the MTD
  gits.

What are the applications for?

  The applications help to create binary flash images for two purposes: pfi
  files (partial flash images) for in-system update of UBI volumes, and plain
  binary images, with or without OOB data in case of NAND, for a manufacturing
  step. Furthermore some tools are/and will be created that allow flash content
  analysis after a system has crashed..

Who did UBI?

  The original ideas, where UBI is based on, were developed by Andreas
  Arnez, Frank Haverkamp and Thomas Gleixner. Josh W. Boyer and some others
  were involved too. The implementation of the kernel layer was done by Artem
  B. Bityutskiy. The user-space applications and tools were written by Oliver
  Lohmann with contributions from Frank Haverkamp, Andreas Arnez, and Artem.
  Joern Engel contributed a patch which modifies JFFS2 so that it can be run on
  a UBI volume. Thomas Gleixner did modifications to the NAND layer. Alexander
  Schmidt made some testing work as well as core functionality improvements.

Signed-off-by: Artem B. Bityutskiy <dedekind@linutronix.de>
Signed-off-by: Frank Haverkamp <haver@vnet.ibm.com>

1 files changed, 848 insertions, 0 deletions

diff --git a/drivers/mtd/ubi/build.c b/drivers/mtd/ubi/build.c
new file mode 100644
index 000000000000..555d594d1811
--- /dev/null
+++ b/drivers/mtd/ubi/build.c
@@ -0,0 +1,848 @@
+/*
+ * 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. At the
+ * moment UBI devices may only be added while UBI is initialized, but dynamic
+ * device add/remove functionality is planned. Also, at the moment we only
+ * attach UBI devices by scanning, which will become a bottleneck when flashes
+ * reach certain large size. Then one may improve UBI and add other methods.
+ */
+
+#include <linux/err.h>
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/stringify.h>
+#include <linux/stat.h>
+#include "ubi.h"
+
+/* Maximum length of the 'mtd=' parameter */
+#define MTD_PARAM_LEN_MAX 64
+
+/**
+ * struct mtd_dev_param - MTD device parameter description data structure.
+ * @name: MTD device name or number string
+ * @vid_hdr_offs: VID header offset
+ * @data_offs: data offset
+ */
+struct mtd_dev_param
+{
+        char name[MTD_PARAM_LEN_MAX];
+        int vid_hdr_offs;
+        int data_offs;
+};
+
+/* Numbers of elements set in the @mtd_dev_param array */
+static int mtd_devs = 0;
+
+/* MTD devices specification parameters */
+static struct mtd_dev_param mtd_dev_param[UBI_MAX_DEVICES];
+
+/* Number of UBI devices in system */
+int ubi_devices_cnt;
+
+/* All UBI devices in system */
+struct ubi_device *ubi_devices[UBI_MAX_DEVICES];
+
+/* Root UBI "class" object (corresponds to '/<sysfs>/class/ubi/') */
+struct class *ubi_class;
+
+/* "Show" method for files in '/<sysfs>/class/ubi/' */
+static ssize_t ubi_version_show(struct class *class, 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);
+
+/* "Show" method for files in '/<sysfs>/class/ubi/ubiX/' */
+static ssize_t dev_attribute_show(struct device *dev,
+                                  struct device_attribute *attr, char *buf)
+{
+        const struct ubi_device *ubi;
+
+        ubi = container_of(dev, struct ubi_device, dev);
+        if (attr == &dev_eraseblock_size)
+                return sprintf(buf, "%d\n", ubi->leb_size);
+        else if (attr == &dev_avail_eraseblocks)
+                return sprintf(buf, "%d\n", ubi->avail_pebs);
+        else if (attr == &dev_total_eraseblocks)
+                return sprintf(buf, "%d\n", ubi->good_peb_count);
+        else if (attr == &dev_volumes_count)
+                return sprintf(buf, "%d\n", ubi->vol_count);
+        else if (attr == &dev_max_ec)
+                return sprintf(buf, "%d\n", ubi->max_ec);
+        else if (attr == &dev_reserved_for_bad)
+                return sprintf(buf, "%d\n", ubi->beb_rsvd_pebs);
+        else if (attr == &dev_bad_peb_count)
+                return sprintf(buf, "%d\n", ubi->bad_peb_count);
+        else if (attr == &dev_max_vol_count)
+                return sprintf(buf, "%d\n", ubi->vtbl_slots);
+        else if (attr == &dev_min_io_size)
+                return sprintf(buf, "%d\n", ubi->min_io_size);
+        else if (attr == &dev_bgt_enabled)
+                return sprintf(buf, "%d\n", ubi->thread_enabled);
+        else
+                BUG();
+
+        return 0;
+}
+
+/* Fake "release" method for UBI devices */
+static void dev_release(struct device *dev) { }
+
+/**
+ * ubi_sysfs_init - initialize sysfs for an UBI device.
+ * @ubi: UBI device description object
+ *
+ * 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 err;
+
+        ubi->dev.release = dev_release;
+        ubi->dev.devt = MKDEV(ubi->major, 0);
+        ubi->dev.class = ubi_class;
+        sprintf(&ubi->dev.bus_id[0], UBI_NAME_STR"%d", ubi->ubi_num);
+        err = device_register(&ubi->dev);
+        if (err)
+                goto out;
+
+        err = device_create_file(&ubi->dev, &dev_eraseblock_size);
+        if (err)
+                goto out_unregister;
+        err = device_create_file(&ubi->dev, &dev_avail_eraseblocks);
+        if (err)
+                goto out_eraseblock_size;
+        err = device_create_file(&ubi->dev, &dev_total_eraseblocks);
+        if (err)
+                goto out_avail_eraseblocks;
+        err = device_create_file(&ubi->dev, &dev_volumes_count);
+        if (err)
+                goto out_total_eraseblocks;
+        err = device_create_file(&ubi->dev, &dev_max_ec);
+        if (err)
+                goto out_volumes_count;
+        err = device_create_file(&ubi->dev, &dev_reserved_for_bad);
+        if (err)
+                goto out_volumes_max_ec;
+        err = device_create_file(&ubi->dev, &dev_bad_peb_count);
+        if (err)
+                goto out_reserved_for_bad;
+        err = device_create_file(&ubi->dev, &dev_max_vol_count);
+        if (err)
+                goto out_bad_peb_count;
+        err = device_create_file(&ubi->dev, &dev_min_io_size);
+        if (err)
+                goto out_max_vol_count;
+        err = device_create_file(&ubi->dev, &dev_bgt_enabled);
+        if (err)
+                goto out_min_io_size;
+
+        return 0;
+
+out_min_io_size:
+        device_remove_file(&ubi->dev, &dev_min_io_size);
+out_max_vol_count:
+        device_remove_file(&ubi->dev, &dev_max_vol_count);
+out_bad_peb_count:
+        device_remove_file(&ubi->dev, &dev_bad_peb_count);
+out_reserved_for_bad:
+        device_remove_file(&ubi->dev, &dev_reserved_for_bad);
+out_volumes_max_ec:
+        device_remove_file(&ubi->dev, &dev_max_ec);
+out_volumes_count:
+        device_remove_file(&ubi->dev, &dev_volumes_count);
+out_total_eraseblocks:
+        device_remove_file(&ubi->dev, &dev_total_eraseblocks);
+out_avail_eraseblocks:
+        device_remove_file(&ubi->dev, &dev_avail_eraseblocks);
+out_eraseblock_size:
+        device_remove_file(&ubi->dev, &dev_eraseblock_size);
+out_unregister:
+        device_unregister(&ubi->dev);
+out:
+        ubi_err("failed to initialize sysfs for %s", ubi->ubi_name);
+        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_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 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, i);
+}
+
+/**
+ * uif_init - initialize user interfaces for an UBI device.
+ * @ubi: UBI device description object
+ *
+ * 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 i, err;
+        dev_t dev;
+
+        mutex_init(&ubi->vtbl_mutex);
+        spin_lock_init(&ubi->volumes_lock);
+
+        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;
+        }
+
+        cdev_init(&ubi->cdev, &ubi_cdev_operations);
+        ubi->major = MAJOR(dev);
+        dbg_msg("%s major is %u", ubi->ubi_name, ubi->major);
+        ubi->cdev.owner = THIS_MODULE;
+
+        dev = MKDEV(ubi->major, 0);
+        err = cdev_add(&ubi->cdev, dev, 1);
+        if (err) {
+                ubi_err("cannot add character device %s", ubi->ubi_name);
+                goto out_unreg;
+        }
+
+        err = ubi_sysfs_init(ubi);
+        if (err)
+                goto out_cdev;
+
+        for (i = 0; i < ubi->vtbl_slots; i++)
+                if (ubi->volumes[i]) {
+                        err = ubi_add_volume(ubi, i);
+                        if (err)
+                                goto out_volumes;
+                }
+
+        return 0;
+
+out_volumes:
+        kill_volumes(ubi);
+        ubi_sysfs_close(ubi);
+out_cdev:
+        cdev_del(&ubi->cdev);
+out_unreg:
+        unregister_chrdev_region(MKDEV(ubi->major, 0),
+                                 ubi->vtbl_slots + 1);
+        return err;
+}
+
+/**
+ * uif_close - close user interfaces for an UBI device.
+ * @ubi: UBI device description object
+ */
+static void uif_close(struct ubi_device *ubi)
+{
+        kill_volumes(ubi);
+        ubi_sysfs_close(ubi);
+        cdev_del(&ubi->cdev);
+        unregister_chrdev_region(MKDEV(ubi->major, 0), ubi->vtbl_slots + 1);
+}
+
+/**
+ * attach_by_scanning - attach an MTD device using scanning method.
+ * @ubi: UBI device descriptor
+ *
+ * This function returns zero in case of success and a negative error code in
+ * case of failure.
+ *
+ * Note, currently this is the only method to attach UBI devices. Hopefully in
+ * the future we'll have more scalable attaching methods and avoid full media
+ * scanning. But even in this case scanning will be needed as a fall-back
+ * attaching method if there are some on-flash table corruptions.
+ */
+static int attach_by_scanning(struct ubi_device *ubi)
+{
+        int err;
+        struct ubi_scan_info *si;
+
+        si = ubi_scan(ubi);
+        if (IS_ERR(si))
+                return PTR_ERR(si);
+
+        ubi->bad_peb_count = si->bad_peb_count;
+        ubi->good_peb_count = ubi->peb_count - ubi->bad_peb_count;
+        ubi->max_ec = si->max_ec;
+        ubi->mean_ec = si->mean_ec;
+
+        err = ubi_read_volume_table(ubi, si);
+        if (err)
+                goto out_si;
+
+        err = ubi_wl_init_scan(ubi, si);
+        if (err)
+                goto out_vtbl;
+
+        err = ubi_eba_init_scan(ubi, si);
+        if (err)
+                goto out_wl;
+
+        ubi_scan_destroy_si(si);
+        return 0;
+
+out_wl:
+        ubi_wl_close(ubi);
+out_vtbl:
+        kfree(ubi->vtbl);
+out_si:
+        ubi_scan_destroy_si(si);
+        return err;
+}
+
+/**
+ * io_init - initialize I/O unit 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;
+        }
+
+        /*
+         * Note, in this implementation we support MTD devices with 0x7FFFFFFF
+         * physical eraseblocks maximum.
+         */
+
+        ubi->peb_size   = ubi->mtd->erasesize;
+        ubi->peb_count  = ubi->mtd->size / ubi->mtd->erasesize;
+        ubi->flash_size = ubi->mtd->size;
+
+        if (ubi->mtd->block_isbad && ubi->mtd->block_markbad)
+                ubi->bad_allowed = 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 */
+        if (ubi->min_io_size == 0 ||
+            (ubi->min_io_size & (ubi->min_io_size - 1))) {
+                ubi_err("bad min. I/O unit");
+                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);
+
+        /* 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("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 */
+        if (ubi->leb_start == 0) {
+                ubi->leb_start = ubi->vid_hdr_offset + ubi->vid_hdr_alsize;
+                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) {
+                ubi_err("bad VID header (%d) or data offsets (%d)",
+                        ubi->vid_hdr_offset, ubi->leb_start);
+                return -EINVAL;
+        }
+
+        /*
+         * 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;
+        }
+
+        dbg_msg("leb_size         %d", ubi->leb_size);
+        dbg_msg("ro_mode          %d", ubi->ro_mode);
+
+        /*
+         * 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 skip ubi->bad_peb_count
+         * uninitialized and initialize it after scanning.
+         */
+
+        return 0;
+}
+
+/**
+ * attach_mtd_dev - attach an MTD device.
+ * @mtd_dev: MTD device name or number string
+ * @vid_hdr_offset: VID header offset
+ * @data_offset: data offset
+ *
+ * This function attaches an MTD device to UBI. It first treats @mtd_dev as the
+ * MTD device name, and tries to open it by this name. If it is unable to open,
+ * it tries to convert @mtd_dev to an integer and open the MTD device by its
+ * number. Returns zero in case of success and a negative error code in case of
+ * failure.
+ */
+static int attach_mtd_dev(const char *mtd_dev, int vid_hdr_offset,
+                          int data_offset)
+{
+        struct ubi_device *ubi;
+        struct mtd_info *mtd;
+        int i, err;
+
+        mtd = get_mtd_device_nm(mtd_dev);
+        if (IS_ERR(mtd)) {
+                int mtd_num;
+                char *endp;
+
+                if (PTR_ERR(mtd) != -ENODEV)
+                        return PTR_ERR(mtd);
+
+                /*
+                 * Probably this is not MTD device name but MTD device number -
+                 * check this out.
+                 */
+                mtd_num = simple_strtoul(mtd_dev, &endp, 0);
+                if (*endp != '\0' || mtd_dev == endp) {
+                        ubi_err("incorrect MTD device: \"%s\"", mtd_dev);
+                        return -ENODEV;
+                }
+
+                mtd = get_mtd_device(NULL, mtd_num);
+                if (IS_ERR(mtd))
+                        return PTR_ERR(mtd);
+        }
+
+        /* Check if we already have the same MTD device attached */
+        for (i = 0; i < ubi_devices_cnt; i++)
+                if (ubi_devices[i]->mtd->index == mtd->index) {
+                        ubi_err("mtd%d is already attached to ubi%d",
+                                mtd->index, i);
+                        err = -EINVAL;
+                        goto out_mtd;
+                }
+
+        ubi = ubi_devices[ubi_devices_cnt] = kzalloc(sizeof(struct ubi_device),
+                                                      GFP_KERNEL);
+        if (!ubi) {
+                err = -ENOMEM;
+                goto out_mtd;
+        }
+
+        ubi->ubi_num = ubi_devices_cnt;
+        ubi->mtd = mtd;
+
+        dbg_msg("attaching mtd%d to ubi%d: VID header offset %d data offset %d",
+                ubi->mtd->index, ubi_devices_cnt, vid_hdr_offset, data_offset);
+
+        ubi->vid_hdr_offset = vid_hdr_offset;
+        ubi->leb_start = data_offset;
+        err = io_init(ubi);
+        if (err)
+                goto out_free;
+
+        err = attach_by_scanning(ubi);
+        if (err) {
+                dbg_err("failed to attach by scanning, error %d", err);
+                goto out_free;
+        }
+
+        err = uif_init(ubi);
+        if (err)
+                goto out_detach;
+
+        ubi_devices_cnt += 1;
+
+        ubi_msg("attached mtd%d to ubi%d", ubi->mtd->index, ubi_devices_cnt);
+        ubi_msg("MTD device name:            \"%s\"", ubi->mtd->name);
+        ubi_msg("MTD device size:            %llu MiB", ubi->flash_size >> 20);
+        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("number of good PEBs:        %d", ubi->good_peb_count);
+        ubi_msg("number of bad PEBs:         %d", ubi->bad_peb_count);
+        ubi_msg("smallest flash I/O unit:    %d", ubi->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);
+        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);
+
+        /* Enable the background thread */
+        if (!DBG_DISABLE_BGT) {
+                ubi->thread_enabled = 1;
+                wake_up_process(ubi->bgt_thread);
+        }
+
+        return 0;
+
+out_detach:
+        ubi_eba_close(ubi);
+        ubi_wl_close(ubi);
+        kfree(ubi->vtbl);
+out_free:
+        kfree(ubi);
+out_mtd:
+        put_mtd_device(mtd);
+        ubi_devices[ubi_devices_cnt] = NULL;
+        return err;
+}
+
+/**
+ * detach_mtd_dev - detach an MTD device.
+ * @ubi: UBI device description object
+ */
+static void detach_mtd_dev(struct ubi_device *ubi)
+{
+        int ubi_num = ubi->ubi_num, mtd_num = ubi->mtd->index;
+
+        dbg_msg("detaching mtd%d from ubi%d", ubi->mtd->index, ubi_num);
+        uif_close(ubi);
+        ubi_eba_close(ubi);
+        ubi_wl_close(ubi);
+        kfree(ubi->vtbl);
+        put_mtd_device(ubi->mtd);
+        kfree(ubi_devices[ubi_num]);
+        ubi_devices[ubi_num] = NULL;
+        ubi_devices_cnt -= 1;
+        ubi_assert(ubi_devices_cnt >= 0);
+        ubi_msg("mtd%d is detached from ubi%d", mtd_num, ubi_num);
+}
+
+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) {
+                printk("UBI error: too many MTD devices, maximum is %d\n",
+                       UBI_MAX_DEVICES);
+                return -EINVAL;
+        }
+
+        ubi_class = class_create(THIS_MODULE, UBI_NAME_STR);
+        if (IS_ERR(ubi_class))
+                return PTR_ERR(ubi_class);
+
+        err = class_create_file(ubi_class, &ubi_version);
+        if (err)
+                goto out_class;
+
+        /* Attach MTD devices */
+        for (i = 0; i < mtd_devs; i++) {
+                struct mtd_dev_param *p = &mtd_dev_param[i];
+
+                cond_resched();
+
+                if (!p->name) {
+                        dbg_err("empty name");
+                        err = -EINVAL;
+                        goto out_detach;
+                }
+
+                err = attach_mtd_dev(p->name, p->vid_hdr_offs, p->data_offs);
+                if (err)
+                        goto out_detach;
+        }
+
+        return 0;
+
+out_detach:
+        for (k = 0; k < i; k++)
+                detach_mtd_dev(ubi_devices[k]);
+        class_remove_file(ubi_class, &ubi_version);
+out_class:
+        class_destroy(ubi_class);
+        return err;
+}
+module_init(ubi_init);
+
+static void __exit ubi_exit(void)
+{
+        int i, n = ubi_devices_cnt;
+
+        for (i = 0; i < n; i++)
+                detach_mtd_dev(ubi_devices[i]);
+        class_remove_file(ubi_class, &ubi_version);
+        class_destroy(ubi_class);
+}
+module_exit(ubi_exit);
+
+/**
+ * bytes_str_to_int - convert a string representing number of bytes to 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 < 0) {
+                printk("UBI error: incorrect bytes count: \"%s\"\n", str);
+                return -EINVAL;
+        }
+
+        switch (*endp) {
+        case 'G':
+                result *= 1024;
+        case 'M':
+                result *= 1024;
+        case 'K':
+        case 'k':
+                result *= 1024;
+                if (endp[1] == 'i' && (endp[2] == '\0' ||
+                          endp[2] == 'B'  || endp[2] == 'b'))
+                        endp += 2;
+        case '\0':
+                break;
+        default:
+                printk("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[3] = {NULL, NULL, NULL};
+
+        if (mtd_devs == UBI_MAX_DEVICES) {
+                printk("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("UBI error: parameter \"%s\" is too long, max. is %d\n",
+                       val, MTD_PARAM_LEN_MAX);
+                return -EINVAL;
+        }
+
+        if (len == 0) {
+                printk("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 < 3; i++)
+                tokens[i] = strsep(&pbuf, ",");
+
+        if (pbuf) {
+                printk("UBI error: too many arguments at \"%s\"\n", val);
+                return -EINVAL;
+        }
+
+        if (tokens[0] == '\0')
+                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 (tokens[2])
+                p->data_offs = bytes_str_to_int(tokens[2]);
+
+        if (p->vid_hdr_offs < 0)
+                return p->vid_hdr_offs;
+        if (p->data_offs < 0)
+                return p->data_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>[,<vid_hdr_offs>,<data_offs>]. "
+                      "Multiple \"mtd\" parameters may be specified.\n"
+                      "MTD devices may be specified by their number or name. "
+                      "Optional \"vid_hdr_offs\" and \"data_offs\" parameters "
+                      "specify UBI VID header position and data starting "
+                      "position to be used by UBI.\n"
+                      "Example: mtd=content,1984,2048 mtd=4 - attach MTD device"
+                      "with name content using VID header offset 1984 and data "
+                      "start 2048, and MTD device number 4 using default "
+                      "offsets");
+
+MODULE_VERSION(__stringify(UBI_VERSION));
+MODULE_DESCRIPTION("UBI - Unsorted Block Images");
+MODULE_AUTHOR("Artem Bityutskiy");
+MODULE_LICENSE("GPL");