Adding upstream version 6.1.76.upstream/6.1.76

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 914 insertions, 0 deletions

diff --git a/drivers/mtd/mtdconcat.c b/drivers/mtd/mtdconcat.c
new file mode 100644
index 000000000..193428de6
--- /dev/null
+++ b/drivers/mtd/mtdconcat.c
@@ -0,0 +1,914 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * MTD device concatenation layer
+ *
+ * Copyright © 2002 Robert Kaiser <rkaiser@sysgo.de>
+ * Copyright © 2002-2010 David Woodhouse <dwmw2@infradead.org>
+ *
+ * NAND support by Christian Gan <cgan@iders.ca>
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/sched.h>
+#include <linux/types.h>
+#include <linux/backing-dev.h>
+
+#include <linux/mtd/mtd.h>
+#include <linux/mtd/concat.h>
+
+#include <asm/div64.h>
+
+/*
+ * Our storage structure:
+ * Subdev points to an array of pointers to struct mtd_info objects
+ * which is allocated along with this structure
+ *
+ */
+struct mtd_concat {
+	struct mtd_info mtd;
+	int num_subdev;
+	struct mtd_info **subdev;
+};
+
+/*
+ * how to calculate the size required for the above structure,
+ * including the pointer array subdev points to:
+ */
+#define SIZEOF_STRUCT_MTD_CONCAT(num_subdev)	\
+	((sizeof(struct mtd_concat) + (num_subdev) * sizeof(struct mtd_info *)))
+
+/*
+ * Given a pointer to the MTD object in the mtd_concat structure,
+ * we can retrieve the pointer to that structure with this macro.
+ */
+#define CONCAT(x)  ((struct mtd_concat *)(x))
+
+/*
+ * MTD methods which look up the relevant subdevice, translate the
+ * effective address and pass through to the subdevice.
+ */
+
+static int
+concat_read(struct mtd_info *mtd, loff_t from, size_t len,
+	    size_t * retlen, u_char * buf)
+{
+	struct mtd_concat *concat = CONCAT(mtd);
+	int ret = 0, err;
+	int i;
+
+	for (i = 0; i < concat->num_subdev; i++) {
+		struct mtd_info *subdev = concat->subdev[i];
+		size_t size, retsize;
+
+		if (from >= subdev->size) {
+			/* Not destined for this subdev */
+			size = 0;
+			from -= subdev->size;
+			continue;
+		}
+		if (from + len > subdev->size)
+			/* First part goes into this subdev */
+			size = subdev->size - from;
+		else
+			/* Entire transaction goes into this subdev */
+			size = len;
+
+		err = mtd_read(subdev, from, size, &retsize, buf);
+
+		/* Save information about bitflips! */
+		if (unlikely(err)) {
+			if (mtd_is_eccerr(err)) {
+				mtd->ecc_stats.failed++;
+				ret = err;
+			} else if (mtd_is_bitflip(err)) {
+				mtd->ecc_stats.corrected++;
+				/* Do not overwrite -EBADMSG !! */
+				if (!ret)
+					ret = err;
+			} else
+				return err;
+		}
+
+		*retlen += retsize;
+		len -= size;
+		if (len == 0)
+			return ret;
+
+		buf += size;
+		from = 0;
+	}
+	return -EINVAL;
+}
+
+static int
+concat_panic_write(struct mtd_info *mtd, loff_t to, size_t len,
+	     size_t * retlen, const u_char * buf)
+{
+	struct mtd_concat *concat = CONCAT(mtd);
+	int err = -EINVAL;
+	int i;
+	for (i = 0; i < concat->num_subdev; i++) {
+		struct mtd_info *subdev = concat->subdev[i];
+		size_t size, retsize;
+
+		if (to >= subdev->size) {
+			to -= subdev->size;
+			continue;
+		}
+		if (to + len > subdev->size)
+			size = subdev->size - to;
+		else
+			size = len;
+
+		err = mtd_panic_write(subdev, to, size, &retsize, buf);
+		if (err == -EOPNOTSUPP) {
+			printk(KERN_ERR "mtdconcat: Cannot write from panic without panic_write\n");
+			return err;
+		}
+		if (err)
+			break;
+
+		*retlen += retsize;
+		len -= size;
+		if (len == 0)
+			break;
+
+		err = -EINVAL;
+		buf += size;
+		to = 0;
+	}
+	return err;
+}
+
+
+static int
+concat_write(struct mtd_info *mtd, loff_t to, size_t len,
+	     size_t * retlen, const u_char * buf)
+{
+	struct mtd_concat *concat = CONCAT(mtd);
+	int err = -EINVAL;
+	int i;
+
+	for (i = 0; i < concat->num_subdev; i++) {
+		struct mtd_info *subdev = concat->subdev[i];
+		size_t size, retsize;
+
+		if (to >= subdev->size) {
+			size = 0;
+			to -= subdev->size;
+			continue;
+		}
+		if (to + len > subdev->size)
+			size = subdev->size - to;
+		else
+			size = len;
+
+		err = mtd_write(subdev, to, size, &retsize, buf);
+		if (err)
+			break;
+
+		*retlen += retsize;
+		len -= size;
+		if (len == 0)
+			break;
+
+		err = -EINVAL;
+		buf += size;
+		to = 0;
+	}
+	return err;
+}
+
+static int
+concat_writev(struct mtd_info *mtd, const struct kvec *vecs,
+		unsigned long count, loff_t to, size_t * retlen)
+{
+	struct mtd_concat *concat = CONCAT(mtd);
+	struct kvec *vecs_copy;
+	unsigned long entry_low, entry_high;
+	size_t total_len = 0;
+	int i;
+	int err = -EINVAL;
+
+	/* Calculate total length of data */
+	for (i = 0; i < count; i++)
+		total_len += vecs[i].iov_len;
+
+	/* Check alignment */
+	if (mtd->writesize > 1) {
+		uint64_t __to = to;
+		if (do_div(__to, mtd->writesize) || (total_len % mtd->writesize))
+			return -EINVAL;
+	}
+
+	/* make a copy of vecs */
+	vecs_copy = kmemdup(vecs, sizeof(struct kvec) * count, GFP_KERNEL);
+	if (!vecs_copy)
+		return -ENOMEM;
+
+	entry_low = 0;
+	for (i = 0; i < concat->num_subdev; i++) {
+		struct mtd_info *subdev = concat->subdev[i];
+		size_t size, wsize, retsize, old_iov_len;
+
+		if (to >= subdev->size) {
+			to -= subdev->size;
+			continue;
+		}
+
+		size = min_t(uint64_t, total_len, subdev->size - to);
+		wsize = size; /* store for future use */
+
+		entry_high = entry_low;
+		while (entry_high < count) {
+			if (size <= vecs_copy[entry_high].iov_len)
+				break;
+			size -= vecs_copy[entry_high++].iov_len;
+		}
+
+		old_iov_len = vecs_copy[entry_high].iov_len;
+		vecs_copy[entry_high].iov_len = size;
+
+		err = mtd_writev(subdev, &vecs_copy[entry_low],
+				 entry_high - entry_low + 1, to, &retsize);
+
+		vecs_copy[entry_high].iov_len = old_iov_len - size;
+		vecs_copy[entry_high].iov_base += size;
+
+		entry_low = entry_high;
+
+		if (err)
+			break;
+
+		*retlen += retsize;
+		total_len -= wsize;
+
+		if (total_len == 0)
+			break;
+
+		err = -EINVAL;
+		to = 0;
+	}
+
+	kfree(vecs_copy);
+	return err;
+}
+
+static int
+concat_read_oob(struct mtd_info *mtd, loff_t from, struct mtd_oob_ops *ops)
+{
+	struct mtd_concat *concat = CONCAT(mtd);
+	struct mtd_oob_ops devops = *ops;
+	int i, err, ret = 0;
+
+	ops->retlen = ops->oobretlen = 0;
+
+	for (i = 0; i < concat->num_subdev; i++) {
+		struct mtd_info *subdev = concat->subdev[i];
+
+		if (from >= subdev->size) {
+			from -= subdev->size;
+			continue;
+		}
+
+		/* partial read ? */
+		if (from + devops.len > subdev->size)
+			devops.len = subdev->size - from;
+
+		err = mtd_read_oob(subdev, from, &devops);
+		ops->retlen += devops.retlen;
+		ops->oobretlen += devops.oobretlen;
+
+		/* Save information about bitflips! */
+		if (unlikely(err)) {
+			if (mtd_is_eccerr(err)) {
+				mtd->ecc_stats.failed++;
+				ret = err;
+			} else if (mtd_is_bitflip(err)) {
+				mtd->ecc_stats.corrected++;
+				/* Do not overwrite -EBADMSG !! */
+				if (!ret)
+					ret = err;
+			} else
+				return err;
+		}
+
+		if (devops.datbuf) {
+			devops.len = ops->len - ops->retlen;
+			if (!devops.len)
+				return ret;
+			devops.datbuf += devops.retlen;
+		}
+		if (devops.oobbuf) {
+			devops.ooblen = ops->ooblen - ops->oobretlen;
+			if (!devops.ooblen)
+				return ret;
+			devops.oobbuf += ops->oobretlen;
+		}
+
+		from = 0;
+	}
+	return -EINVAL;
+}
+
+static int
+concat_write_oob(struct mtd_info *mtd, loff_t to, struct mtd_oob_ops *ops)
+{
+	struct mtd_concat *concat = CONCAT(mtd);
+	struct mtd_oob_ops devops = *ops;
+	int i, err;
+
+	if (!(mtd->flags & MTD_WRITEABLE))
+		return -EROFS;
+
+	ops->retlen = ops->oobretlen = 0;
+
+	for (i = 0; i < concat->num_subdev; i++) {
+		struct mtd_info *subdev = concat->subdev[i];
+
+		if (to >= subdev->size) {
+			to -= subdev->size;
+			continue;
+		}
+
+		/* partial write ? */
+		if (to + devops.len > subdev->size)
+			devops.len = subdev->size - to;
+
+		err = mtd_write_oob(subdev, to, &devops);
+		ops->retlen += devops.retlen;
+		ops->oobretlen += devops.oobretlen;
+		if (err)
+			return err;
+
+		if (devops.datbuf) {
+			devops.len = ops->len - ops->retlen;
+			if (!devops.len)
+				return 0;
+			devops.datbuf += devops.retlen;
+		}
+		if (devops.oobbuf) {
+			devops.ooblen = ops->ooblen - ops->oobretlen;
+			if (!devops.ooblen)
+				return 0;
+			devops.oobbuf += devops.oobretlen;
+		}
+		to = 0;
+	}
+	return -EINVAL;
+}
+
+static int concat_erase(struct mtd_info *mtd, struct erase_info *instr)
+{
+	struct mtd_concat *concat = CONCAT(mtd);
+	struct mtd_info *subdev;
+	int i, err;
+	uint64_t length, offset = 0;
+	struct erase_info *erase;
+
+	/*
+	 * Check for proper erase block alignment of the to-be-erased area.
+	 * It is easier to do this based on the super device's erase
+	 * region info rather than looking at each particular sub-device
+	 * in turn.
+	 */
+	if (!concat->mtd.numeraseregions) {
+		/* the easy case: device has uniform erase block size */
+		if (instr->addr & (concat->mtd.erasesize - 1))
+			return -EINVAL;
+		if (instr->len & (concat->mtd.erasesize - 1))
+			return -EINVAL;
+	} else {
+		/* device has variable erase size */
+		struct mtd_erase_region_info *erase_regions =
+		    concat->mtd.eraseregions;
+
+		/*
+		 * Find the erase region where the to-be-erased area begins:
+		 */
+		for (i = 0; i < concat->mtd.numeraseregions &&
+		     instr->addr >= erase_regions[i].offset; i++) ;
+		--i;
+
+		/*
+		 * Now erase_regions[i] is the region in which the
+		 * to-be-erased area begins. Verify that the starting
+		 * offset is aligned to this region's erase size:
+		 */
+		if (i < 0 || instr->addr & (erase_regions[i].erasesize - 1))
+			return -EINVAL;
+
+		/*
+		 * now find the erase region where the to-be-erased area ends:
+		 */
+		for (; i < concat->mtd.numeraseregions &&
+		     (instr->addr + instr->len) >= erase_regions[i].offset;
+		     ++i) ;
+		--i;
+		/*
+		 * check if the ending offset is aligned to this region's erase size
+		 */
+		if (i < 0 || ((instr->addr + instr->len) &
+					(erase_regions[i].erasesize - 1)))
+			return -EINVAL;
+	}
+
+	/* make a local copy of instr to avoid modifying the caller's struct */
+	erase = kmalloc(sizeof (struct erase_info), GFP_KERNEL);
+
+	if (!erase)
+		return -ENOMEM;
+
+	*erase = *instr;
+	length = instr->len;
+
+	/*
+	 * find the subdevice where the to-be-erased area begins, adjust
+	 * starting offset to be relative to the subdevice start
+	 */
+	for (i = 0; i < concat->num_subdev; i++) {
+		subdev = concat->subdev[i];
+		if (subdev->size <= erase->addr) {
+			erase->addr -= subdev->size;
+			offset += subdev->size;
+		} else {
+			break;
+		}
+	}
+
+	/* must never happen since size limit has been verified above */
+	BUG_ON(i >= concat->num_subdev);
+
+	/* now do the erase: */
+	err = 0;
+	for (; length > 0; i++) {
+		/* loop for all subdevices affected by this request */
+		subdev = concat->subdev[i];	/* get current subdevice */
+
+		/* limit length to subdevice's size: */
+		if (erase->addr + length > subdev->size)
+			erase->len = subdev->size - erase->addr;
+		else
+			erase->len = length;
+
+		length -= erase->len;
+		if ((err = mtd_erase(subdev, erase))) {
+			/* sanity check: should never happen since
+			 * block alignment has been checked above */
+			BUG_ON(err == -EINVAL);
+			if (erase->fail_addr != MTD_FAIL_ADDR_UNKNOWN)
+				instr->fail_addr = erase->fail_addr + offset;
+			break;
+		}
+		/*
+		 * erase->addr specifies the offset of the area to be
+		 * erased *within the current subdevice*. It can be
+		 * non-zero only the first time through this loop, i.e.
+		 * for the first subdevice where blocks need to be erased.
+		 * All the following erases must begin at the start of the
+		 * current subdevice, i.e. at offset zero.
+		 */
+		erase->addr = 0;
+		offset += subdev->size;
+	}
+	kfree(erase);
+
+	return err;
+}
+
+static int concat_xxlock(struct mtd_info *mtd, loff_t ofs, uint64_t len,
+			 bool is_lock)
+{
+	struct mtd_concat *concat = CONCAT(mtd);
+	int i, err = -EINVAL;
+
+	for (i = 0; i < concat->num_subdev; i++) {
+		struct mtd_info *subdev = concat->subdev[i];
+		uint64_t size;
+
+		if (ofs >= subdev->size) {
+			size = 0;
+			ofs -= subdev->size;
+			continue;
+		}
+		if (ofs + len > subdev->size)
+			size = subdev->size - ofs;
+		else
+			size = len;
+
+		if (is_lock)
+			err = mtd_lock(subdev, ofs, size);
+		else
+			err = mtd_unlock(subdev, ofs, size);
+		if (err)
+			break;
+
+		len -= size;
+		if (len == 0)
+			break;
+
+		err = -EINVAL;
+		ofs = 0;
+	}
+
+	return err;
+}
+
+static int concat_lock(struct mtd_info *mtd, loff_t ofs, uint64_t len)
+{
+	return concat_xxlock(mtd, ofs, len, true);
+}
+
+static int concat_unlock(struct mtd_info *mtd, loff_t ofs, uint64_t len)
+{
+	return concat_xxlock(mtd, ofs, len, false);
+}
+
+static int concat_is_locked(struct mtd_info *mtd, loff_t ofs, uint64_t len)
+{
+	struct mtd_concat *concat = CONCAT(mtd);
+	int i, err = -EINVAL;
+
+	for (i = 0; i < concat->num_subdev; i++) {
+		struct mtd_info *subdev = concat->subdev[i];
+
+		if (ofs >= subdev->size) {
+			ofs -= subdev->size;
+			continue;
+		}
+
+		if (ofs + len > subdev->size)
+			break;
+
+		return mtd_is_locked(subdev, ofs, len);
+	}
+
+	return err;
+}
+
+static void concat_sync(struct mtd_info *mtd)
+{
+	struct mtd_concat *concat = CONCAT(mtd);
+	int i;
+
+	for (i = 0; i < concat->num_subdev; i++) {
+		struct mtd_info *subdev = concat->subdev[i];
+		mtd_sync(subdev);
+	}
+}
+
+static int concat_suspend(struct mtd_info *mtd)
+{
+	struct mtd_concat *concat = CONCAT(mtd);
+	int i, rc = 0;
+
+	for (i = 0; i < concat->num_subdev; i++) {
+		struct mtd_info *subdev = concat->subdev[i];
+		if ((rc = mtd_suspend(subdev)) < 0)
+			return rc;
+	}
+	return rc;
+}
+
+static void concat_resume(struct mtd_info *mtd)
+{
+	struct mtd_concat *concat = CONCAT(mtd);
+	int i;
+
+	for (i = 0; i < concat->num_subdev; i++) {
+		struct mtd_info *subdev = concat->subdev[i];
+		mtd_resume(subdev);
+	}
+}
+
+static int concat_block_isbad(struct mtd_info *mtd, loff_t ofs)
+{
+	struct mtd_concat *concat = CONCAT(mtd);
+	int i, res = 0;
+
+	if (!mtd_can_have_bb(concat->subdev[0]))
+		return res;
+
+	for (i = 0; i < concat->num_subdev; i++) {
+		struct mtd_info *subdev = concat->subdev[i];
+
+		if (ofs >= subdev->size) {
+			ofs -= subdev->size;
+			continue;
+		}
+
+		res = mtd_block_isbad(subdev, ofs);
+		break;
+	}
+
+	return res;
+}
+
+static int concat_block_markbad(struct mtd_info *mtd, loff_t ofs)
+{
+	struct mtd_concat *concat = CONCAT(mtd);
+	int i, err = -EINVAL;
+
+	for (i = 0; i < concat->num_subdev; i++) {
+		struct mtd_info *subdev = concat->subdev[i];
+
+		if (ofs >= subdev->size) {
+			ofs -= subdev->size;
+			continue;
+		}
+
+		err = mtd_block_markbad(subdev, ofs);
+		if (!err)
+			mtd->ecc_stats.badblocks++;
+		break;
+	}
+
+	return err;
+}
+
+/*
+ * This function constructs a virtual MTD device by concatenating
+ * num_devs MTD devices. A pointer to the new device object is
+ * stored to *new_dev upon success. This function does _not_
+ * register any devices: this is the caller's responsibility.
+ */
+struct mtd_info *mtd_concat_create(struct mtd_info *subdev[],	/* subdevices to concatenate */
+				   int num_devs,	/* number of subdevices      */
+				   const char *name)
+{				/* name for the new device   */
+	int i;
+	size_t size;
+	struct mtd_concat *concat;
+	struct mtd_info *subdev_master = NULL;
+	uint32_t max_erasesize, curr_erasesize;
+	int num_erase_region;
+	int max_writebufsize = 0;
+
+	printk(KERN_NOTICE "Concatenating MTD devices:\n");
+	for (i = 0; i < num_devs; i++)
+		printk(KERN_NOTICE "(%d): \"%s\"\n", i, subdev[i]->name);
+	printk(KERN_NOTICE "into device \"%s\"\n", name);
+
+	/* allocate the device structure */
+	size = SIZEOF_STRUCT_MTD_CONCAT(num_devs);
+	concat = kzalloc(size, GFP_KERNEL);
+	if (!concat) {
+		printk
+		    ("memory allocation error while creating concatenated device \"%s\"\n",
+		     name);
+		return NULL;
+	}
+	concat->subdev = (struct mtd_info **) (concat + 1);
+
+	/*
+	 * Set up the new "super" device's MTD object structure, check for
+	 * incompatibilities between the subdevices.
+	 */
+	concat->mtd.type = subdev[0]->type;
+	concat->mtd.flags = subdev[0]->flags;
+	concat->mtd.size = subdev[0]->size;
+	concat->mtd.erasesize = subdev[0]->erasesize;
+	concat->mtd.writesize = subdev[0]->writesize;
+
+	for (i = 0; i < num_devs; i++)
+		if (max_writebufsize < subdev[i]->writebufsize)
+			max_writebufsize = subdev[i]->writebufsize;
+	concat->mtd.writebufsize = max_writebufsize;
+
+	concat->mtd.subpage_sft = subdev[0]->subpage_sft;
+	concat->mtd.oobsize = subdev[0]->oobsize;
+	concat->mtd.oobavail = subdev[0]->oobavail;
+
+	subdev_master = mtd_get_master(subdev[0]);
+	if (subdev_master->_writev)
+		concat->mtd._writev = concat_writev;
+	if (subdev_master->_read_oob)
+		concat->mtd._read_oob = concat_read_oob;
+	if (subdev_master->_write_oob)
+		concat->mtd._write_oob = concat_write_oob;
+	if (subdev_master->_block_isbad)
+		concat->mtd._block_isbad = concat_block_isbad;
+	if (subdev_master->_block_markbad)
+		concat->mtd._block_markbad = concat_block_markbad;
+	if (subdev_master->_panic_write)
+		concat->mtd._panic_write = concat_panic_write;
+	if (subdev_master->_read)
+		concat->mtd._read = concat_read;
+	if (subdev_master->_write)
+		concat->mtd._write = concat_write;
+
+	concat->mtd.ecc_stats.badblocks = subdev[0]->ecc_stats.badblocks;
+
+	concat->subdev[0] = subdev[0];
+
+	for (i = 1; i < num_devs; i++) {
+		if (concat->mtd.type != subdev[i]->type) {
+			kfree(concat);
+			printk("Incompatible device type on \"%s\"\n",
+			       subdev[i]->name);
+			return NULL;
+		}
+		if (concat->mtd.flags != subdev[i]->flags) {
+			/*
+			 * Expect all flags except MTD_WRITEABLE to be
+			 * equal on all subdevices.
+			 */
+			if ((concat->mtd.flags ^ subdev[i]->
+			     flags) & ~MTD_WRITEABLE) {
+				kfree(concat);
+				printk("Incompatible device flags on \"%s\"\n",
+				       subdev[i]->name);
+				return NULL;
+			} else
+				/* if writeable attribute differs,
+				   make super device writeable */
+				concat->mtd.flags |=
+				    subdev[i]->flags & MTD_WRITEABLE;
+		}
+
+		subdev_master = mtd_get_master(subdev[i]);
+		concat->mtd.size += subdev[i]->size;
+		concat->mtd.ecc_stats.badblocks +=
+			subdev[i]->ecc_stats.badblocks;
+		if (concat->mtd.writesize   !=  subdev[i]->writesize ||
+		    concat->mtd.subpage_sft != subdev[i]->subpage_sft ||
+		    concat->mtd.oobsize    !=  subdev[i]->oobsize ||
+		    !concat->mtd._read_oob  != !subdev_master->_read_oob ||
+		    !concat->mtd._write_oob != !subdev_master->_write_oob) {
+			/*
+			 * Check against subdev[i] for data members, because
+			 * subdev's attributes may be different from master
+			 * mtd device. Check against subdev's master mtd
+			 * device for callbacks, because the existence of
+			 * subdev's callbacks is decided by master mtd device.
+			 */
+			kfree(concat);
+			printk("Incompatible OOB or ECC data on \"%s\"\n",
+			       subdev[i]->name);
+			return NULL;
+		}
+		concat->subdev[i] = subdev[i];
+
+	}
+
+	mtd_set_ooblayout(&concat->mtd, subdev[0]->ooblayout);
+
+	concat->num_subdev = num_devs;
+	concat->mtd.name = name;
+
+	concat->mtd._erase = concat_erase;
+	concat->mtd._sync = concat_sync;
+	concat->mtd._lock = concat_lock;
+	concat->mtd._unlock = concat_unlock;
+	concat->mtd._is_locked = concat_is_locked;
+	concat->mtd._suspend = concat_suspend;
+	concat->mtd._resume = concat_resume;
+
+	/*
+	 * Combine the erase block size info of the subdevices:
+	 *
+	 * first, walk the map of the new device and see how
+	 * many changes in erase size we have
+	 */
+	max_erasesize = curr_erasesize = subdev[0]->erasesize;
+	num_erase_region = 1;
+	for (i = 0; i < num_devs; i++) {
+		if (subdev[i]->numeraseregions == 0) {
+			/* current subdevice has uniform erase size */
+			if (subdev[i]->erasesize != curr_erasesize) {
+				/* if it differs from the last subdevice's erase size, count it */
+				++num_erase_region;
+				curr_erasesize = subdev[i]->erasesize;
+				if (curr_erasesize > max_erasesize)
+					max_erasesize = curr_erasesize;
+			}
+		} else {
+			/* current subdevice has variable erase size */
+			int j;
+			for (j = 0; j < subdev[i]->numeraseregions; j++) {
+
+				/* walk the list of erase regions, count any changes */
+				if (subdev[i]->eraseregions[j].erasesize !=
+				    curr_erasesize) {
+					++num_erase_region;
+					curr_erasesize =
+					    subdev[i]->eraseregions[j].
+					    erasesize;
+					if (curr_erasesize > max_erasesize)
+						max_erasesize = curr_erasesize;
+				}
+			}
+		}
+	}
+
+	if (num_erase_region == 1) {
+		/*
+		 * All subdevices have the same uniform erase size.
+		 * This is easy:
+		 */
+		concat->mtd.erasesize = curr_erasesize;
+		concat->mtd.numeraseregions = 0;
+	} else {
+		uint64_t tmp64;
+
+		/*
+		 * erase block size varies across the subdevices: allocate
+		 * space to store the data describing the variable erase regions
+		 */
+		struct mtd_erase_region_info *erase_region_p;
+		uint64_t begin, position;
+
+		concat->mtd.erasesize = max_erasesize;
+		concat->mtd.numeraseregions = num_erase_region;
+		concat->mtd.eraseregions = erase_region_p =
+		    kmalloc_array(num_erase_region,
+				  sizeof(struct mtd_erase_region_info),
+				  GFP_KERNEL);
+		if (!erase_region_p) {
+			kfree(concat);
+			printk
+			    ("memory allocation error while creating erase region list"
+			     " for device \"%s\"\n", name);
+			return NULL;
+		}
+
+		/*
+		 * walk the map of the new device once more and fill in
+		 * erase region info:
+		 */
+		curr_erasesize = subdev[0]->erasesize;
+		begin = position = 0;
+		for (i = 0; i < num_devs; i++) {
+			if (subdev[i]->numeraseregions == 0) {
+				/* current subdevice has uniform erase size */
+				if (subdev[i]->erasesize != curr_erasesize) {
+					/*
+					 *  fill in an mtd_erase_region_info structure for the area
+					 *  we have walked so far:
+					 */
+					erase_region_p->offset = begin;
+					erase_region_p->erasesize =
+					    curr_erasesize;
+					tmp64 = position - begin;
+					do_div(tmp64, curr_erasesize);
+					erase_region_p->numblocks = tmp64;
+					begin = position;
+
+					curr_erasesize = subdev[i]->erasesize;
+					++erase_region_p;
+				}
+				position += subdev[i]->size;
+			} else {
+				/* current subdevice has variable erase size */
+				int j;
+				for (j = 0; j < subdev[i]->numeraseregions; j++) {
+					/* walk the list of erase regions, count any changes */
+					if (subdev[i]->eraseregions[j].
+					    erasesize != curr_erasesize) {
+						erase_region_p->offset = begin;
+						erase_region_p->erasesize =
+						    curr_erasesize;
+						tmp64 = position - begin;
+						do_div(tmp64, curr_erasesize);
+						erase_region_p->numblocks = tmp64;
+						begin = position;
+
+						curr_erasesize =
+						    subdev[i]->eraseregions[j].
+						    erasesize;
+						++erase_region_p;
+					}
+					position +=
+					    subdev[i]->eraseregions[j].
+					    numblocks * (uint64_t)curr_erasesize;
+				}
+			}
+		}
+		/* Now write the final entry */
+		erase_region_p->offset = begin;
+		erase_region_p->erasesize = curr_erasesize;
+		tmp64 = position - begin;
+		do_div(tmp64, curr_erasesize);
+		erase_region_p->numblocks = tmp64;
+	}
+
+	return &concat->mtd;
+}
+
+/* Cleans the context obtained from mtd_concat_create() */
+void mtd_concat_destroy(struct mtd_info *mtd)
+{
+	struct mtd_concat *concat = CONCAT(mtd);
+	if (concat->mtd.numeraseregions)
+		kfree(concat->mtd.eraseregions);
+	kfree(concat);
+}
+
+EXPORT_SYMBOL(mtd_concat_create);
+EXPORT_SYMBOL(mtd_concat_destroy);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Robert Kaiser <rkaiser@sysgo.de>");
+MODULE_DESCRIPTION("Generic support for concatenating of MTD devices");