1// SPDX-License-Identifier: GPL-2.0-or-later
  2/*
  3 * MTD device concatenation layer
  4 *
  5 * Copyright © 2002 Robert Kaiser <rkaiser@sysgo.de>
  6 * Copyright © 2002-2010 David Woodhouse <dwmw2@infradead.org>
  7 *
  8 * NAND support by Christian Gan <cgan@iders.ca>
  9 */
 10
 11#include <linux/kernel.h>
 12#include <linux/module.h>
 13#include <linux/slab.h>
 14#include <linux/sched.h>
 15#include <linux/types.h>
 16#include <linux/backing-dev.h>
 17
 18#include <linux/mtd/mtd.h>
 19#include <linux/mtd/concat.h>
 20
 21#include <asm/div64.h>
 22
 23/*
 24 * Our storage structure:
 25 * Subdev points to an array of pointers to struct mtd_info objects
 26 * which is allocated along with this structure
 27 *
 28 */
 29struct mtd_concat {
 30	struct mtd_info mtd;
 31	int num_subdev;
 32	struct mtd_info **subdev;
 33};
 34
 35/*
 36 * how to calculate the size required for the above structure,
 37 * including the pointer array subdev points to:
 38 */
 39#define SIZEOF_STRUCT_MTD_CONCAT(num_subdev)	\
 40	((sizeof(struct mtd_concat) + (num_subdev) * sizeof(struct mtd_info *)))
 41
 42/*
 43 * Given a pointer to the MTD object in the mtd_concat structure,
 44 * we can retrieve the pointer to that structure with this macro.
 45 */
 46#define CONCAT(x)  ((struct mtd_concat *)(x))
 47
 48/*
 49 * MTD methods which look up the relevant subdevice, translate the
 50 * effective address and pass through to the subdevice.
 51 */
 52
 53static int
 54concat_read(struct mtd_info *mtd, loff_t from, size_t len,
 55	    size_t * retlen, u_char * buf)
 56{
 57	struct mtd_concat *concat = CONCAT(mtd);
 58	int ret = 0, err;
 59	int i;
 60
 61	for (i = 0; i < concat->num_subdev; i++) {
 62		struct mtd_info *subdev = concat->subdev[i];
 63		size_t size, retsize;
 64
 65		if (from >= subdev->size) {
 66			/* Not destined for this subdev */
 67			size = 0;
 68			from -= subdev->size;
 69			continue;
 70		}
 71		if (from + len > subdev->size)
 72			/* First part goes into this subdev */
 73			size = subdev->size - from;
 74		else
 75			/* Entire transaction goes into this subdev */
 76			size = len;
 77
 78		err = mtd_read(subdev, from, size, &retsize, buf);
 79
 80		/* Save information about bitflips! */
 81		if (unlikely(err)) {
 82			if (mtd_is_eccerr(err)) {
 83				mtd->ecc_stats.failed++;
 84				ret = err;
 85			} else if (mtd_is_bitflip(err)) {
 86				mtd->ecc_stats.corrected++;
 87				/* Do not overwrite -EBADMSG !! */
 88				if (!ret)
 89					ret = err;
 90			} else
 91				return err;
 92		}
 93
 94		*retlen += retsize;
 95		len -= size;
 96		if (len == 0)
 97			return ret;
 98
 99		buf += size;
100		from = 0;
101	}
102	return -EINVAL;
103}
104
105static int
106concat_write(struct mtd_info *mtd, loff_t to, size_t len,
107	     size_t * retlen, const u_char * buf)
108{
109	struct mtd_concat *concat = CONCAT(mtd);
110	int err = -EINVAL;
111	int i;
112
113	for (i = 0; i < concat->num_subdev; i++) {
114		struct mtd_info *subdev = concat->subdev[i];
115		size_t size, retsize;
116
117		if (to >= subdev->size) {
118			size = 0;
119			to -= subdev->size;
120			continue;
121		}
122		if (to + len > subdev->size)
123			size = subdev->size - to;
124		else
125			size = len;
126
127		err = mtd_write(subdev, to, size, &retsize, buf);
128		if (err)
129			break;
130
131		*retlen += retsize;
132		len -= size;
133		if (len == 0)
134			break;
135
136		err = -EINVAL;
137		buf += size;
138		to = 0;
139	}
140	return err;
141}
142
143static int
144concat_writev(struct mtd_info *mtd, const struct kvec *vecs,
145		unsigned long count, loff_t to, size_t * retlen)
146{
147	struct mtd_concat *concat = CONCAT(mtd);
148	struct kvec *vecs_copy;
149	unsigned long entry_low, entry_high;
150	size_t total_len = 0;
151	int i;
152	int err = -EINVAL;
153
154	/* Calculate total length of data */
155	for (i = 0; i < count; i++)
156		total_len += vecs[i].iov_len;
157
158	/* Check alignment */
159	if (mtd->writesize > 1) {
160		uint64_t __to = to;
161		if (do_div(__to, mtd->writesize) || (total_len % mtd->writesize))
162			return -EINVAL;
163	}
164
165	/* make a copy of vecs */
166	vecs_copy = kmemdup(vecs, sizeof(struct kvec) * count, GFP_KERNEL);
167	if (!vecs_copy)
168		return -ENOMEM;
169
170	entry_low = 0;
171	for (i = 0; i < concat->num_subdev; i++) {
172		struct mtd_info *subdev = concat->subdev[i];
173		size_t size, wsize, retsize, old_iov_len;
174
175		if (to >= subdev->size) {
176			to -= subdev->size;
177			continue;
178		}
179
180		size = min_t(uint64_t, total_len, subdev->size - to);
181		wsize = size; /* store for future use */
182
183		entry_high = entry_low;
184		while (entry_high < count) {
185			if (size <= vecs_copy[entry_high].iov_len)
186				break;
187			size -= vecs_copy[entry_high++].iov_len;
188		}
189
190		old_iov_len = vecs_copy[entry_high].iov_len;
191		vecs_copy[entry_high].iov_len = size;
192
193		err = mtd_writev(subdev, &vecs_copy[entry_low],
194				 entry_high - entry_low + 1, to, &retsize);
195
196		vecs_copy[entry_high].iov_len = old_iov_len - size;
197		vecs_copy[entry_high].iov_base += size;
198
199		entry_low = entry_high;
200
201		if (err)
202			break;
203
204		*retlen += retsize;
205		total_len -= wsize;
206
207		if (total_len == 0)
208			break;
209
210		err = -EINVAL;
211		to = 0;
212	}
213
214	kfree(vecs_copy);
215	return err;
216}
217
218static int
219concat_read_oob(struct mtd_info *mtd, loff_t from, struct mtd_oob_ops *ops)
220{
221	struct mtd_concat *concat = CONCAT(mtd);
222	struct mtd_oob_ops devops = *ops;
223	int i, err, ret = 0;
224
225	ops->retlen = ops->oobretlen = 0;
226
227	for (i = 0; i < concat->num_subdev; i++) {
228		struct mtd_info *subdev = concat->subdev[i];
229
230		if (from >= subdev->size) {
231			from -= subdev->size;
232			continue;
233		}
234
235		/* partial read ? */
236		if (from + devops.len > subdev->size)
237			devops.len = subdev->size - from;
238
239		err = mtd_read_oob(subdev, from, &devops);
240		ops->retlen += devops.retlen;
241		ops->oobretlen += devops.oobretlen;
242
243		/* Save information about bitflips! */
244		if (unlikely(err)) {
245			if (mtd_is_eccerr(err)) {
246				mtd->ecc_stats.failed++;
247				ret = err;
248			} else if (mtd_is_bitflip(err)) {
249				mtd->ecc_stats.corrected++;
250				/* Do not overwrite -EBADMSG !! */
251				if (!ret)
252					ret = err;
253			} else
254				return err;
255		}
256
257		if (devops.datbuf) {
258			devops.len = ops->len - ops->retlen;
259			if (!devops.len)
260				return ret;
261			devops.datbuf += devops.retlen;
262		}
263		if (devops.oobbuf) {
264			devops.ooblen = ops->ooblen - ops->oobretlen;
265			if (!devops.ooblen)
266				return ret;
267			devops.oobbuf += ops->oobretlen;
268		}
269
270		from = 0;
271	}
272	return -EINVAL;
273}
274
275static int
276concat_write_oob(struct mtd_info *mtd, loff_t to, struct mtd_oob_ops *ops)
277{
278	struct mtd_concat *concat = CONCAT(mtd);
279	struct mtd_oob_ops devops = *ops;
280	int i, err;
281
282	if (!(mtd->flags & MTD_WRITEABLE))
283		return -EROFS;
284
285	ops->retlen = ops->oobretlen = 0;
286
287	for (i = 0; i < concat->num_subdev; i++) {
288		struct mtd_info *subdev = concat->subdev[i];
289
290		if (to >= subdev->size) {
291			to -= subdev->size;
292			continue;
293		}
294
295		/* partial write ? */
296		if (to + devops.len > subdev->size)
297			devops.len = subdev->size - to;
298
299		err = mtd_write_oob(subdev, to, &devops);
300		ops->retlen += devops.retlen;
301		ops->oobretlen += devops.oobretlen;
302		if (err)
303			return err;
304
305		if (devops.datbuf) {
306			devops.len = ops->len - ops->retlen;
307			if (!devops.len)
308				return 0;
309			devops.datbuf += devops.retlen;
310		}
311		if (devops.oobbuf) {
312			devops.ooblen = ops->ooblen - ops->oobretlen;
313			if (!devops.ooblen)
314				return 0;
315			devops.oobbuf += devops.oobretlen;
316		}
317		to = 0;
318	}
319	return -EINVAL;
320}
321
322static int concat_erase(struct mtd_info *mtd, struct erase_info *instr)
323{
324	struct mtd_concat *concat = CONCAT(mtd);
325	struct mtd_info *subdev;
326	int i, err;
327	uint64_t length, offset = 0;
328	struct erase_info *erase;
329
330	/*
331	 * Check for proper erase block alignment of the to-be-erased area.
332	 * It is easier to do this based on the super device's erase
333	 * region info rather than looking at each particular sub-device
334	 * in turn.
335	 */
336	if (!concat->mtd.numeraseregions) {
337		/* the easy case: device has uniform erase block size */
338		if (instr->addr & (concat->mtd.erasesize - 1))
339			return -EINVAL;
340		if (instr->len & (concat->mtd.erasesize - 1))
341			return -EINVAL;
342	} else {
343		/* device has variable erase size */
344		struct mtd_erase_region_info *erase_regions =
345		    concat->mtd.eraseregions;
346
347		/*
348		 * Find the erase region where the to-be-erased area begins:
349		 */
350		for (i = 0; i < concat->mtd.numeraseregions &&
351		     instr->addr >= erase_regions[i].offset; i++) ;
352		--i;
353
354		/*
355		 * Now erase_regions[i] is the region in which the
356		 * to-be-erased area begins. Verify that the starting
357		 * offset is aligned to this region's erase size:
358		 */
359		if (i < 0 || instr->addr & (erase_regions[i].erasesize - 1))
360			return -EINVAL;
361
362		/*
363		 * now find the erase region where the to-be-erased area ends:
364		 */
365		for (; i < concat->mtd.numeraseregions &&
366		     (instr->addr + instr->len) >= erase_regions[i].offset;
367		     ++i) ;
368		--i;
369		/*
370		 * check if the ending offset is aligned to this region's erase size
371		 */
372		if (i < 0 || ((instr->addr + instr->len) &
373					(erase_regions[i].erasesize - 1)))
374			return -EINVAL;
375	}
376
377	/* make a local copy of instr to avoid modifying the caller's struct */
378	erase = kmalloc(sizeof (struct erase_info), GFP_KERNEL);
379
380	if (!erase)
381		return -ENOMEM;
382
383	*erase = *instr;
384	length = instr->len;
385
386	/*
387	 * find the subdevice where the to-be-erased area begins, adjust
388	 * starting offset to be relative to the subdevice start
389	 */
390	for (i = 0; i < concat->num_subdev; i++) {
391		subdev = concat->subdev[i];
392		if (subdev->size <= erase->addr) {
393			erase->addr -= subdev->size;
394			offset += subdev->size;
395		} else {
396			break;
397		}
398	}
399
400	/* must never happen since size limit has been verified above */
401	BUG_ON(i >= concat->num_subdev);
402
403	/* now do the erase: */
404	err = 0;
405	for (; length > 0; i++) {
406		/* loop for all subdevices affected by this request */
407		subdev = concat->subdev[i];	/* get current subdevice */
408
409		/* limit length to subdevice's size: */
410		if (erase->addr + length > subdev->size)
411			erase->len = subdev->size - erase->addr;
412		else
413			erase->len = length;
414
415		length -= erase->len;
416		if ((err = mtd_erase(subdev, erase))) {
417			/* sanity check: should never happen since
418			 * block alignment has been checked above */
419			BUG_ON(err == -EINVAL);
420			if (erase->fail_addr != MTD_FAIL_ADDR_UNKNOWN)
421				instr->fail_addr = erase->fail_addr + offset;
422			break;
423		}
424		/*
425		 * erase->addr specifies the offset of the area to be
426		 * erased *within the current subdevice*. It can be
427		 * non-zero only the first time through this loop, i.e.
428		 * for the first subdevice where blocks need to be erased.
429		 * All the following erases must begin at the start of the
430		 * current subdevice, i.e. at offset zero.
431		 */
432		erase->addr = 0;
433		offset += subdev->size;
434	}
435	kfree(erase);
436
437	return err;
438}
439
440static int concat_xxlock(struct mtd_info *mtd, loff_t ofs, uint64_t len,
441			 bool is_lock)
442{
443	struct mtd_concat *concat = CONCAT(mtd);
444	int i, err = -EINVAL;
445
446	for (i = 0; i < concat->num_subdev; i++) {
447		struct mtd_info *subdev = concat->subdev[i];
448		uint64_t size;
449
450		if (ofs >= subdev->size) {
451			size = 0;
452			ofs -= subdev->size;
453			continue;
454		}
455		if (ofs + len > subdev->size)
456			size = subdev->size - ofs;
457		else
458			size = len;
459
460		if (is_lock)
461			err = mtd_lock(subdev, ofs, size);
462		else
463			err = mtd_unlock(subdev, ofs, size);
464		if (err)
465			break;
466
467		len -= size;
468		if (len == 0)
469			break;
470
471		err = -EINVAL;
472		ofs = 0;
473	}
474
475	return err;
476}
477
478static int concat_lock(struct mtd_info *mtd, loff_t ofs, uint64_t len)
479{
480	return concat_xxlock(mtd, ofs, len, true);
481}
482
483static int concat_unlock(struct mtd_info *mtd, loff_t ofs, uint64_t len)
484{
485	return concat_xxlock(mtd, ofs, len, false);
486}
487
488static int concat_is_locked(struct mtd_info *mtd, loff_t ofs, uint64_t len)
489{
490	struct mtd_concat *concat = CONCAT(mtd);
491	int i, err = -EINVAL;
492
493	for (i = 0; i < concat->num_subdev; i++) {
494		struct mtd_info *subdev = concat->subdev[i];
495
496		if (ofs >= subdev->size) {
497			ofs -= subdev->size;
498			continue;
499		}
500
501		if (ofs + len > subdev->size)
502			break;
503
504		return mtd_is_locked(subdev, ofs, len);
505	}
506
507	return err;
508}
509
510static void concat_sync(struct mtd_info *mtd)
511{
512	struct mtd_concat *concat = CONCAT(mtd);
513	int i;
514
515	for (i = 0; i < concat->num_subdev; i++) {
516		struct mtd_info *subdev = concat->subdev[i];
517		mtd_sync(subdev);
518	}
519}
520
521static int concat_suspend(struct mtd_info *mtd)
522{
523	struct mtd_concat *concat = CONCAT(mtd);
524	int i, rc = 0;
525
526	for (i = 0; i < concat->num_subdev; i++) {
527		struct mtd_info *subdev = concat->subdev[i];
528		if ((rc = mtd_suspend(subdev)) < 0)
529			return rc;
530	}
531	return rc;
532}
533
534static void concat_resume(struct mtd_info *mtd)
535{
536	struct mtd_concat *concat = CONCAT(mtd);
537	int i;
538
539	for (i = 0; i < concat->num_subdev; i++) {
540		struct mtd_info *subdev = concat->subdev[i];
541		mtd_resume(subdev);
542	}
543}
544
545static int concat_block_isbad(struct mtd_info *mtd, loff_t ofs)
546{
547	struct mtd_concat *concat = CONCAT(mtd);
548	int i, res = 0;
549
550	if (!mtd_can_have_bb(concat->subdev[0]))
551		return res;
552
553	for (i = 0; i < concat->num_subdev; i++) {
554		struct mtd_info *subdev = concat->subdev[i];
555
556		if (ofs >= subdev->size) {
557			ofs -= subdev->size;
558			continue;
559		}
560
561		res = mtd_block_isbad(subdev, ofs);
562		break;
563	}
564
565	return res;
566}
567
568static int concat_block_markbad(struct mtd_info *mtd, loff_t ofs)
569{
570	struct mtd_concat *concat = CONCAT(mtd);
571	int i, err = -EINVAL;
572
573	for (i = 0; i < concat->num_subdev; i++) {
574		struct mtd_info *subdev = concat->subdev[i];
575
576		if (ofs >= subdev->size) {
577			ofs -= subdev->size;
578			continue;
579		}
580
581		err = mtd_block_markbad(subdev, ofs);
582		if (!err)
583			mtd->ecc_stats.badblocks++;
584		break;
585	}
586
587	return err;
588}
589
590/*
591 * This function constructs a virtual MTD device by concatenating
592 * num_devs MTD devices. A pointer to the new device object is
593 * stored to *new_dev upon success. This function does _not_
594 * register any devices: this is the caller's responsibility.
595 */
596struct mtd_info *mtd_concat_create(struct mtd_info *subdev[],	/* subdevices to concatenate */
597				   int num_devs,	/* number of subdevices      */
598				   const char *name)
599{				/* name for the new device   */
600	int i;
601	size_t size;
602	struct mtd_concat *concat;
603	uint32_t max_erasesize, curr_erasesize;
604	int num_erase_region;
605	int max_writebufsize = 0;
606
607	printk(KERN_NOTICE "Concatenating MTD devices:\n");
608	for (i = 0; i < num_devs; i++)
609		printk(KERN_NOTICE "(%d): \"%s\"\n", i, subdev[i]->name);
610	printk(KERN_NOTICE "into device \"%s\"\n", name);
611
612	/* allocate the device structure */
613	size = SIZEOF_STRUCT_MTD_CONCAT(num_devs);
614	concat = kzalloc(size, GFP_KERNEL);
615	if (!concat) {
616		printk
617		    ("memory allocation error while creating concatenated device \"%s\"\n",
618		     name);
619		return NULL;
620	}
621	concat->subdev = (struct mtd_info **) (concat + 1);
622
623	/*
624	 * Set up the new "super" device's MTD object structure, check for
625	 * incompatibilities between the subdevices.
626	 */
627	concat->mtd.type = subdev[0]->type;
628	concat->mtd.flags = subdev[0]->flags;
629	concat->mtd.size = subdev[0]->size;
630	concat->mtd.erasesize = subdev[0]->erasesize;
631	concat->mtd.writesize = subdev[0]->writesize;
632
633	for (i = 0; i < num_devs; i++)
634		if (max_writebufsize < subdev[i]->writebufsize)
635			max_writebufsize = subdev[i]->writebufsize;
636	concat->mtd.writebufsize = max_writebufsize;
637
638	concat->mtd.subpage_sft = subdev[0]->subpage_sft;
639	concat->mtd.oobsize = subdev[0]->oobsize;
640	concat->mtd.oobavail = subdev[0]->oobavail;
641	if (subdev[0]->_writev)
642		concat->mtd._writev = concat_writev;
643	if (subdev[0]->_read_oob)
644		concat->mtd._read_oob = concat_read_oob;
645	if (subdev[0]->_write_oob)
646		concat->mtd._write_oob = concat_write_oob;
647	if (subdev[0]->_block_isbad)
648		concat->mtd._block_isbad = concat_block_isbad;
649	if (subdev[0]->_block_markbad)
650		concat->mtd._block_markbad = concat_block_markbad;
651
652	concat->mtd.ecc_stats.badblocks = subdev[0]->ecc_stats.badblocks;
653
654	concat->subdev[0] = subdev[0];
655
656	for (i = 1; i < num_devs; i++) {
657		if (concat->mtd.type != subdev[i]->type) {
658			kfree(concat);
659			printk("Incompatible device type on \"%s\"\n",
660			       subdev[i]->name);
661			return NULL;
662		}
663		if (concat->mtd.flags != subdev[i]->flags) {
664			/*
665			 * Expect all flags except MTD_WRITEABLE to be
666			 * equal on all subdevices.
667			 */
668			if ((concat->mtd.flags ^ subdev[i]->
669			     flags) & ~MTD_WRITEABLE) {
670				kfree(concat);
671				printk("Incompatible device flags on \"%s\"\n",
672				       subdev[i]->name);
673				return NULL;
674			} else
675				/* if writeable attribute differs,
676				   make super device writeable */
677				concat->mtd.flags |=
678				    subdev[i]->flags & MTD_WRITEABLE;
679		}
680
681		concat->mtd.size += subdev[i]->size;
682		concat->mtd.ecc_stats.badblocks +=
683			subdev[i]->ecc_stats.badblocks;
684		if (concat->mtd.writesize   !=  subdev[i]->writesize ||
685		    concat->mtd.subpage_sft != subdev[i]->subpage_sft ||
686		    concat->mtd.oobsize    !=  subdev[i]->oobsize ||
687		    !concat->mtd._read_oob  != !subdev[i]->_read_oob ||
688		    !concat->mtd._write_oob != !subdev[i]->_write_oob) {
689			kfree(concat);
690			printk("Incompatible OOB or ECC data on \"%s\"\n",
691			       subdev[i]->name);
692			return NULL;
693		}
694		concat->subdev[i] = subdev[i];
695
696	}
697
698	mtd_set_ooblayout(&concat->mtd, subdev[0]->ooblayout);
699
700	concat->num_subdev = num_devs;
701	concat->mtd.name = name;
702
703	concat->mtd._erase = concat_erase;
704	concat->mtd._read = concat_read;
705	concat->mtd._write = concat_write;
706	concat->mtd._sync = concat_sync;
707	concat->mtd._lock = concat_lock;
708	concat->mtd._unlock = concat_unlock;
709	concat->mtd._is_locked = concat_is_locked;
710	concat->mtd._suspend = concat_suspend;
711	concat->mtd._resume = concat_resume;
712
713	/*
714	 * Combine the erase block size info of the subdevices:
715	 *
716	 * first, walk the map of the new device and see how
717	 * many changes in erase size we have
718	 */
719	max_erasesize = curr_erasesize = subdev[0]->erasesize;
720	num_erase_region = 1;
721	for (i = 0; i < num_devs; i++) {
722		if (subdev[i]->numeraseregions == 0) {
723			/* current subdevice has uniform erase size */
724			if (subdev[i]->erasesize != curr_erasesize) {
725				/* if it differs from the last subdevice's erase size, count it */
726				++num_erase_region;
727				curr_erasesize = subdev[i]->erasesize;
728				if (curr_erasesize > max_erasesize)
729					max_erasesize = curr_erasesize;
730			}
731		} else {
732			/* current subdevice has variable erase size */
733			int j;
734			for (j = 0; j < subdev[i]->numeraseregions; j++) {
735
736				/* walk the list of erase regions, count any changes */
737				if (subdev[i]->eraseregions[j].erasesize !=
738				    curr_erasesize) {
739					++num_erase_region;
740					curr_erasesize =
741					    subdev[i]->eraseregions[j].
742					    erasesize;
743					if (curr_erasesize > max_erasesize)
744						max_erasesize = curr_erasesize;
745				}
746			}
747		}
748	}
749
750	if (num_erase_region == 1) {
751		/*
752		 * All subdevices have the same uniform erase size.
753		 * This is easy:
754		 */
755		concat->mtd.erasesize = curr_erasesize;
756		concat->mtd.numeraseregions = 0;
757	} else {
758		uint64_t tmp64;
759
760		/*
761		 * erase block size varies across the subdevices: allocate
762		 * space to store the data describing the variable erase regions
763		 */
764		struct mtd_erase_region_info *erase_region_p;
765		uint64_t begin, position;
766
767		concat->mtd.erasesize = max_erasesize;
768		concat->mtd.numeraseregions = num_erase_region;
769		concat->mtd.eraseregions = erase_region_p =
770		    kmalloc_array(num_erase_region,
771				  sizeof(struct mtd_erase_region_info),
772				  GFP_KERNEL);
773		if (!erase_region_p) {
774			kfree(concat);
775			printk
776			    ("memory allocation error while creating erase region list"
777			     " for device \"%s\"\n", name);
778			return NULL;
779		}
780
781		/*
782		 * walk the map of the new device once more and fill in
783		 * in erase region info:
784		 */
785		curr_erasesize = subdev[0]->erasesize;
786		begin = position = 0;
787		for (i = 0; i < num_devs; i++) {
788			if (subdev[i]->numeraseregions == 0) {
789				/* current subdevice has uniform erase size */
790				if (subdev[i]->erasesize != curr_erasesize) {
791					/*
792					 *  fill in an mtd_erase_region_info structure for the area
793					 *  we have walked so far:
794					 */
795					erase_region_p->offset = begin;
796					erase_region_p->erasesize =
797					    curr_erasesize;
798					tmp64 = position - begin;
799					do_div(tmp64, curr_erasesize);
800					erase_region_p->numblocks = tmp64;
801					begin = position;
802
803					curr_erasesize = subdev[i]->erasesize;
804					++erase_region_p;
805				}
806				position += subdev[i]->size;
807			} else {
808				/* current subdevice has variable erase size */
809				int j;
810				for (j = 0; j < subdev[i]->numeraseregions; j++) {
811					/* walk the list of erase regions, count any changes */
812					if (subdev[i]->eraseregions[j].
813					    erasesize != curr_erasesize) {
814						erase_region_p->offset = begin;
815						erase_region_p->erasesize =
816						    curr_erasesize;
817						tmp64 = position - begin;
818						do_div(tmp64, curr_erasesize);
819						erase_region_p->numblocks = tmp64;
820						begin = position;
821
822						curr_erasesize =
823						    subdev[i]->eraseregions[j].
824						    erasesize;
825						++erase_region_p;
826					}
827					position +=
828					    subdev[i]->eraseregions[j].
829					    numblocks * (uint64_t)curr_erasesize;
830				}
831			}
832		}
833		/* Now write the final entry */
834		erase_region_p->offset = begin;
835		erase_region_p->erasesize = curr_erasesize;
836		tmp64 = position - begin;
837		do_div(tmp64, curr_erasesize);
838		erase_region_p->numblocks = tmp64;
839	}
840
841	return &concat->mtd;
842}
843
844/* Cleans the context obtained from mtd_concat_create() */
 
 
 
845void mtd_concat_destroy(struct mtd_info *mtd)
846{
847	struct mtd_concat *concat = CONCAT(mtd);
848	if (concat->mtd.numeraseregions)
849		kfree(concat->mtd.eraseregions);
850	kfree(concat);
851}
852
853EXPORT_SYMBOL(mtd_concat_create);
854EXPORT_SYMBOL(mtd_concat_destroy);
855
856MODULE_LICENSE("GPL");
857MODULE_AUTHOR("Robert Kaiser <rkaiser@sysgo.de>");
858MODULE_DESCRIPTION("Generic support for concatenating of MTD devices");