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* Copyright (c) International Business Machines Corp., 2006
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See
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* the GNU General Public License for more details.
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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* Author: Artem Bityutskiy (ŠŠøŃŃŃŠŗŠøŠ¹ ŠŃŃŃŠ¼), Joern Engel
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* This is a small driver which implements fake MTD devices on top of UBI
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* volumes. This sounds strange, but it is in fact quite useful to make
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* MTD-oriented software (including all the legacy software) work on top of
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* Gluebi emulates MTD devices of "MTD_UBIVOLUME" type. Their minimal I/O unit
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* size (@mtd->writesize) is equivalent to the UBI minimal I/O unit. The
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* eraseblock size is equivalent to the logical eraseblock size of the volume.
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#include <linux/err.h>
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#include <linux/list.h>
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#include <linux/slab.h>
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#include <linux/sched.h>
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#include <linux/math64.h>
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#include <linux/module.h>
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#include <linux/mutex.h>
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#include <linux/mtd/ubi.h>
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#include <linux/mtd/mtd.h>
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#include "ubi-media.h"
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#define err_msg(fmt, ...) \
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printk(KERN_DEBUG "gluebi (pid %d): %s: " fmt "\n", \
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current->pid, __func__, ##__VA_ARGS__)
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* struct gluebi_device - a gluebi device description data structure.
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* @mtd: emulated MTD device description object
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* @refcnt: gluebi device reference count
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* @desc: UBI volume descriptor
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* @ubi_num: UBI device number this gluebi device works on
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* @vol_id: ID of UBI volume this gluebi device works on
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* @list: link in a list of gluebi devices
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struct gluebi_device {
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struct ubi_volume_desc *desc;
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struct list_head list;
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/* List of all gluebi devices */
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static LIST_HEAD(gluebi_devices);
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static DEFINE_MUTEX(devices_mutex);
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* find_gluebi_nolock - find a gluebi device.
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* @ubi_num: UBI device number
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* This function seraches for gluebi device corresponding to UBI device
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* @ubi_num and UBI volume @vol_id. Returns the gluebi device description
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* object in case of success and %NULL in case of failure. The caller has to
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* have the &devices_mutex locked.
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static struct gluebi_device *find_gluebi_nolock(int ubi_num, int vol_id)
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struct gluebi_device *gluebi;
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list_for_each_entry(gluebi, &gluebi_devices, list)
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if (gluebi->ubi_num == ubi_num && gluebi->vol_id == vol_id)
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* gluebi_get_device - get MTD device reference.
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* @mtd: the MTD device description object
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* This function is called every time the MTD device is being opened and
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* implements the MTD get_device() operation. Returns zero in case of success
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* and a negative error code in case of failure.
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static int gluebi_get_device(struct mtd_info *mtd)
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struct gluebi_device *gluebi;
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int ubi_mode = UBI_READONLY;
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if (!try_module_get(THIS_MODULE))
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if (mtd->flags & MTD_WRITEABLE)
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ubi_mode = UBI_READWRITE;
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gluebi = container_of(mtd, struct gluebi_device, mtd);
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mutex_lock(&devices_mutex);
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if (gluebi->refcnt > 0) {
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* The MTD device is already referenced and this is just one
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* more reference. MTD allows many users to open the same
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* volume simultaneously and do not distinguish between
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* readers/writers/exclusive openers as UBI does. So we do not
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* open the UBI volume again - just increase the reference
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* counter and return.
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mutex_unlock(&devices_mutex);
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* This is the first reference to this UBI volume via the MTD device
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* interface. Open the corresponding volume in read-write mode.
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gluebi->desc = ubi_open_volume(gluebi->ubi_num, gluebi->vol_id,
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if (IS_ERR(gluebi->desc)) {
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mutex_unlock(&devices_mutex);
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module_put(THIS_MODULE);
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return PTR_ERR(gluebi->desc);
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mutex_unlock(&devices_mutex);
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* gluebi_put_device - put MTD device reference.
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* @mtd: the MTD device description object
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* This function is called every time the MTD device is being put. Returns
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* zero in case of success and a negative error code in case of failure.
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static void gluebi_put_device(struct mtd_info *mtd)
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struct gluebi_device *gluebi;
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gluebi = container_of(mtd, struct gluebi_device, mtd);
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mutex_lock(&devices_mutex);
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if (gluebi->refcnt == 0)
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ubi_close_volume(gluebi->desc);
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module_put(THIS_MODULE);
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mutex_unlock(&devices_mutex);
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* gluebi_read - read operation of emulated MTD devices.
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* @mtd: MTD device description object
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* @from: absolute offset from where to read
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* @len: how many bytes to read
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* @retlen: count of read bytes is returned here
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* @buf: buffer to store the read data
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* This function returns zero in case of success and a negative error code in
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static int gluebi_read(struct mtd_info *mtd, loff_t from, size_t len,
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size_t *retlen, unsigned char *buf)
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int err = 0, lnum, offs, total_read;
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struct gluebi_device *gluebi;
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if (len < 0 || from < 0 || from + len > mtd->size)
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gluebi = container_of(mtd, struct gluebi_device, mtd);
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lnum = div_u64_rem(from, mtd->erasesize, &offs);
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size_t to_read = mtd->erasesize - offs;
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if (to_read > total_read)
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to_read = total_read;
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err = ubi_read(gluebi->desc, lnum, buf, offs, to_read);
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total_read -= to_read;
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*retlen = len - total_read;
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* gluebi_write - write operation of emulated MTD devices.
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* @mtd: MTD device description object
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* @to: absolute offset where to write
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* @len: how many bytes to write
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* @retlen: count of written bytes is returned here
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* @buf: buffer with data to write
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* This function returns zero in case of success and a negative error code in
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static int gluebi_write(struct mtd_info *mtd, loff_t to, size_t len,
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size_t *retlen, const u_char *buf)
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int err = 0, lnum, offs, total_written;
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struct gluebi_device *gluebi;
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if (len < 0 || to < 0 || len + to > mtd->size)
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gluebi = container_of(mtd, struct gluebi_device, mtd);
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if (!(mtd->flags & MTD_WRITEABLE))
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lnum = div_u64_rem(to, mtd->erasesize, &offs);
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if (len % mtd->writesize || offs % mtd->writesize)
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while (total_written) {
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size_t to_write = mtd->erasesize - offs;
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if (to_write > total_written)
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to_write = total_written;
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err = ubi_write(gluebi->desc, lnum, buf, offs, to_write);
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total_written -= to_write;
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*retlen = len - total_written;
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* gluebi_erase - erase operation of emulated MTD devices.
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* @mtd: the MTD device description object
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* @instr: the erase operation description
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* This function calls the erase callback when finishes. Returns zero in case
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* of success and a negative error code in case of failure.
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static int gluebi_erase(struct mtd_info *mtd, struct erase_info *instr)
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int err, i, lnum, count;
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struct gluebi_device *gluebi;
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if (instr->addr < 0 || instr->addr > mtd->size - mtd->erasesize)
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if (instr->len < 0 || instr->addr + instr->len > mtd->size)
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if (mtd_mod_by_ws(instr->addr, mtd) || mtd_mod_by_ws(instr->len, mtd))
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lnum = mtd_div_by_eb(instr->addr, mtd);
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count = mtd_div_by_eb(instr->len, mtd);
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gluebi = container_of(mtd, struct gluebi_device, mtd);
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if (!(mtd->flags & MTD_WRITEABLE))
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for (i = 0; i < count - 1; i++) {
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err = ubi_leb_unmap(gluebi->desc, lnum + i);
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* MTD erase operations are synchronous, so we have to make sure the
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* physical eraseblock is wiped out.
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* Thus, perform leb_erase instead of leb_unmap operation - leb_erase
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* will wait for the end of operations
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err = ubi_leb_erase(gluebi->desc, lnum + i);
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instr->state = MTD_ERASE_DONE;
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mtd_erase_callback(instr);
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instr->state = MTD_ERASE_FAILED;
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instr->fail_addr = (long long)lnum * mtd->erasesize;
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* gluebi_create - create a gluebi device for an UBI volume.
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* @di: UBI device description object
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* @vi: UBI volume description object
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* This function is called when a new UBI volume is created in order to create
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* corresponding fake MTD device. Returns zero in case of success and a
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* negative error code in case of failure.
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static int gluebi_create(struct ubi_device_info *di,
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struct ubi_volume_info *vi)
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struct gluebi_device *gluebi, *g;
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struct mtd_info *mtd;
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gluebi = kzalloc(sizeof(struct gluebi_device), GFP_KERNEL);
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mtd->name = kmemdup(vi->name, vi->name_len + 1, GFP_KERNEL);
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gluebi->vol_id = vi->vol_id;
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gluebi->ubi_num = vi->ubi_num;
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mtd->type = MTD_UBIVOLUME;
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mtd->flags = MTD_WRITEABLE;
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mtd->owner = THIS_MODULE;
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mtd->writesize = di->min_io_size;
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mtd->erasesize = vi->usable_leb_size;
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mtd->read = gluebi_read;
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mtd->write = gluebi_write;
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mtd->erase = gluebi_erase;
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mtd->get_device = gluebi_get_device;
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mtd->put_device = gluebi_put_device;
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* In case of dynamic a volume, MTD device size is just volume size. In
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* case of a static volume the size is equivalent to the amount of data
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if (vi->vol_type == UBI_DYNAMIC_VOLUME)
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mtd->size = (unsigned long long)vi->usable_leb_size * vi->size;
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mtd->size = vi->used_bytes;
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/* Just a sanity check - make sure this gluebi device does not exist */
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mutex_lock(&devices_mutex);
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g = find_gluebi_nolock(vi->ubi_num, vi->vol_id);
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err_msg("gluebi MTD device %d form UBI device %d volume %d "
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"already exists", g->mtd.index, vi->ubi_num,
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mutex_unlock(&devices_mutex);
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if (mtd_device_register(mtd, NULL, 0)) {
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err_msg("cannot add MTD device");
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mutex_lock(&devices_mutex);
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list_add_tail(&gluebi->list, &gluebi_devices);
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mutex_unlock(&devices_mutex);
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* gluebi_remove - remove a gluebi device.
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* @vi: UBI volume description object
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* This function is called when an UBI volume is removed and it removes
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* corresponding fake MTD device. Returns zero in case of success and a
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* negative error code in case of failure.
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static int gluebi_remove(struct ubi_volume_info *vi)
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struct mtd_info *mtd;
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struct gluebi_device *gluebi;
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mutex_lock(&devices_mutex);
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gluebi = find_gluebi_nolock(vi->ubi_num, vi->vol_id);
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err_msg("got remove notification for unknown UBI device %d "
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"volume %d", vi->ubi_num, vi->vol_id);
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} else if (gluebi->refcnt)
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list_del(&gluebi->list);
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mutex_unlock(&devices_mutex);
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err = mtd_device_unregister(mtd);
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err_msg("cannot remove fake MTD device %d, UBI device %d, "
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"volume %d, error %d", mtd->index, gluebi->ubi_num,
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gluebi->vol_id, err);
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mutex_lock(&devices_mutex);
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list_add_tail(&gluebi->list, &gluebi_devices);
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mutex_unlock(&devices_mutex);
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* gluebi_updated - UBI volume was updated notifier.
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* @vi: volume info structure
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* This function is called every time an UBI volume is updated. It does nothing
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* if te volume @vol is dynamic, and changes MTD device size if the
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* volume is static. This is needed because static volumes cannot be read past
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* data they contain. This function returns zero in case of success and a
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* negative error code in case of error.
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static int gluebi_updated(struct ubi_volume_info *vi)
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struct gluebi_device *gluebi;
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mutex_lock(&devices_mutex);
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gluebi = find_gluebi_nolock(vi->ubi_num, vi->vol_id);
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mutex_unlock(&devices_mutex);
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err_msg("got update notification for unknown UBI device %d "
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"volume %d", vi->ubi_num, vi->vol_id);
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if (vi->vol_type == UBI_STATIC_VOLUME)
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gluebi->mtd.size = vi->used_bytes;
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mutex_unlock(&devices_mutex);
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* gluebi_resized - UBI volume was re-sized notifier.
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* @vi: volume info structure
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* This function is called every time an UBI volume is re-size. It changes the
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* corresponding fake MTD device size. This function returns zero in case of
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* success and a negative error code in case of error.
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static int gluebi_resized(struct ubi_volume_info *vi)
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struct gluebi_device *gluebi;
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mutex_lock(&devices_mutex);
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gluebi = find_gluebi_nolock(vi->ubi_num, vi->vol_id);
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mutex_unlock(&devices_mutex);
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err_msg("got update notification for unknown UBI device %d "
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"volume %d", vi->ubi_num, vi->vol_id);
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gluebi->mtd.size = vi->used_bytes;
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mutex_unlock(&devices_mutex);
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* gluebi_notify - UBI notification handler.
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* @nb: registered notifier block
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* @l: notification type
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* @ptr: pointer to the &struct ubi_notification object
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static int gluebi_notify(struct notifier_block *nb, unsigned long l,
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struct ubi_notification *nt = ns_ptr;
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case UBI_VOLUME_ADDED:
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gluebi_create(&nt->di, &nt->vi);
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case UBI_VOLUME_REMOVED:
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gluebi_remove(&nt->vi);
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case UBI_VOLUME_RESIZED:
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gluebi_resized(&nt->vi);
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case UBI_VOLUME_UPDATED:
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gluebi_updated(&nt->vi);
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static struct notifier_block gluebi_notifier = {
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.notifier_call = gluebi_notify,
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static int __init ubi_gluebi_init(void)
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return ubi_register_volume_notifier(&gluebi_notifier, 0);
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static void __exit ubi_gluebi_exit(void)
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struct gluebi_device *gluebi, *g;
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list_for_each_entry_safe(gluebi, g, &gluebi_devices, list) {
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struct mtd_info *mtd = &gluebi->mtd;
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err = mtd_device_unregister(mtd);
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err_msg("error %d while removing gluebi MTD device %d, "
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"UBI device %d, volume %d - ignoring", err,
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mtd->index, gluebi->ubi_num, gluebi->vol_id);
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ubi_unregister_volume_notifier(&gluebi_notifier);
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module_init(ubi_gluebi_init);
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module_exit(ubi_gluebi_exit);
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MODULE_DESCRIPTION("MTD emulation layer over UBI volumes");
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MODULE_AUTHOR("Artem Bityutskiy, Joern Engel");
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MODULE_LICENSE("GPL");