aboutsummaryrefslogtreecommitdiffstats
path: root/drivers/mtd/inftlcore.c
blob: d8cf29c01cc46ce6d9c26e01f85dad1630f456b6 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
/*
 * inftlcore.c -- Linux driver for Inverse Flash Translation Layer (INFTL)
 *
 * (C) Copyright 2002, Greg Ungerer (gerg@snapgear.com)
 *
 * Based heavily on the nftlcore.c code which is:
 * (c) 1999 Machine Vision Holdings, Inc.
 * Author: David Woodhouse <dwmw2@infradead.org>
 *
 * 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
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/delay.h>
#include <linux/slab.h>
#include <linux/sched.h>
#include <linux/init.h>
#include <linux/kmod.h>
#include <linux/hdreg.h>
#include <linux/mtd/mtd.h>
#include <linux/mtd/nftl.h>
#include <linux/mtd/inftl.h>
#include <linux/mtd/nand.h>
#include <asm/uaccess.h>
#include <asm/errno.h>
#include <asm/io.h>

/*
 * Maximum number of loops while examining next block, to have a
 * chance to detect consistency problems (they should never happen
 * because of the checks done in the mounting.
 */
#define MAX_LOOPS 10000

static void inftl_add_mtd(struct mtd_blktrans_ops *tr, struct mtd_info *mtd)
{
	struct INFTLrecord *inftl;
	unsigned long temp;

	if (mtd->type != MTD_NANDFLASH || mtd->size > UINT_MAX)
		return;
	/* OK, this is moderately ugly.  But probably safe.  Alternatives? */
	if (memcmp(mtd->name, "DiskOnChip", 10))
		return;

	if (!mtd->block_isbad) {
		printk(KERN_ERR
"INFTL no longer supports the old DiskOnChip drivers loaded via docprobe.\n"
"Please use the new diskonchip driver under the NAND subsystem.\n");
		return;
	}

	DEBUG(MTD_DEBUG_LEVEL3, "INFTL: add_mtd for %s\n", mtd->name);

	inftl = kzalloc(sizeof(*inftl), GFP_KERNEL);

	if (!inftl) {
		printk(KERN_WARNING "INFTL: Out of memory for data structures\n");
		return;
	}

	inftl->mbd.mtd = mtd;
	inftl->mbd.devnum = -1;

	inftl->mbd.tr = tr;

	if (INFTL_mount(inftl) < 0) {
		printk(KERN_WARNING "INFTL: could not mount device\n");
		kfree(inftl);
		return;
	}

	/* OK, it's a new one. Set up all the data structures. */

	/* Calculate geometry */
	inftl->cylinders = 1024;
	inftl->heads = 16;

	temp = inftl->cylinders * inftl->heads;
	inftl->sectors = inftl->mbd.size / temp;
	if (inftl->mbd.size % temp) {
		inftl->sectors++;
		temp = inftl->cylinders * inftl->sectors;
		inftl->heads = inftl->mbd.size / temp;

		if (inftl->mbd.size % temp) {
			inftl->heads++;
			temp = inftl->heads * inftl->sectors;
			inftl->cylinders = inftl->mbd.size / temp;
		}
	}

	if (inftl->mbd.size != inftl->heads * inftl->cylinders * inftl->sectors) {
		/*
		  Oh no we don't have
		   mbd.size == heads * cylinders * sectors
		*/
		printk(KERN_WARNING "INFTL: cannot calculate a geometry to "
		       "match size of 0x%lx.\n", inftl->mbd.size);
		printk(KERN_WARNING "INFTL: using C:%d H:%d S:%d "
			"(== 0x%lx sects)\n",
			inftl->cylinders, inftl->heads , inftl->sectors,
			(long)inftl->cylinders * (long)inftl->heads *
			(long)inftl->sectors );
	}

	if (add_mtd_blktrans_dev(&inftl->mbd)) {
		kfree(inftl->PUtable);
		kfree(inftl->VUtable);
		kfree(inftl);
		return;
	}
#ifdef PSYCHO_DEBUG
	printk(KERN_INFO "INFTL: Found new inftl%c\n", inftl->mbd.devnum + 'a');
#endif
	return;
}

static void inftl_remove_dev(struct mtd_blktrans_dev *dev)
{
	struct INFTLrecord *inftl = (void *)dev;

	DEBUG(MTD_DEBUG_LEVEL3, "INFTL: remove_dev (i=%d)\n", dev->devnum);

	del_mtd_blktrans_dev(dev);

	kfree(inftl->PUtable);
	kfree(inftl->VUtable);
	kfree(inftl);
}

/*
 * Actual INFTL access routines.
 */

/*
 * Read oob data from flash
 */
int inftl_read_oob(struct mtd_info *mtd, loff_t offs, size_t len,
		   size_t *retlen, uint8_t *buf)
{
	struct mtd_oob_ops ops;
	int res;

	ops.mode = MTD_OOB_PLACE;
	ops.ooboffs = offs & (mtd->writesize - 1);
	ops.ooblen = len;
	ops.oobbuf = buf;
	ops.datbuf = NULL;

	res = mtd->read_oob(mtd, offs & ~(mtd->writesize - 1), &ops);
	*retlen = ops.oobretlen;
	return res;
}

/*
 * Write oob data to flash
 */
int inftl_write_oob(struct mtd_info *mtd, loff_t offs, size_t len,
		    size_t *retlen, uint8_t *buf)
{
	struct mtd_oob_ops ops;
	int res;

	ops.mode = MTD_OOB_PLACE;
	ops.ooboffs = offs & (mtd->writesize - 1);
	ops.ooblen = len;
	ops.oobbuf = buf;
	ops.datbuf = NULL;

	res = mtd->write_oob(mtd, offs & ~(mtd->writesize - 1), &ops);
	*retlen = ops.oobretlen;
	return res;
}

/*
 * Write data and oob to flash
 */
static int inftl_write(struct mtd_info *mtd, loff_t offs, size_t len,
		       size_t *retlen, uint8_t *buf, uint8_t *oob)
{
	struct mtd_oob_ops ops;
	int res;

	ops.mode = MTD_OOB_PLACE;
	ops.ooboffs = offs;
	ops.ooblen = mtd->oobsize;
	ops.oobbuf = oob;
	ops.datbuf = buf;
	ops.len = len;

	res = mtd->write_oob(mtd, offs & ~(mtd->writesize - 1), &ops);
	*retlen = ops.retlen;
	return res;
}

/*
 * INFTL_findfreeblock: Find a free Erase Unit on the INFTL partition.
 *	This function is used when the give Virtual Unit Chain.
 */
static u16 INFTL_findfreeblock(struct INFTLrecord *inftl, int desperate)
{
	u16 pot = inftl->LastFreeEUN;
	int silly = inftl->nb_blocks;

	DEBUG(MTD_DEBUG_LEVEL3, "INFTL: INFTL_findfreeblock(inftl=%p,"
		"desperate=%d)\n", inftl, desperate);

	/*
	 * Normally, we force a fold to happen before we run out of free
	 * blocks completely.
	 */
	if (!desperate && inftl->numfreeEUNs < 2) {
		DEBUG(MTD_DEBUG_LEVEL1, "INFTL: there are too few free "
			"EUNs (%d)\n", inftl->numfreeEUNs);
		return BLOCK_NIL;
	}

	/* Scan for a free block */
	do {
		if (inftl->PUtable[pot] == BLOCK_FREE) {
			inftl->LastFreeEUN = pot;
			return pot;
		}

		if (++pot > inftl->lastEUN)
			pot = 0;

		if (!silly--) {
			printk(KERN_WARNING "INFTL: no free blocks found!  "
				"EUN range = %d - %d\n", 0, inftl->LastFreeEUN);
			return BLOCK_NIL;
		}
	} while (pot != inftl->LastFreeEUN);

	return BLOCK_NIL;
}

static u16 INFTL_foldchain(struct INFTLrecord *inftl, unsigned thisVUC, unsigned pendingblock)
{
	u16 BlockMap[MAX_SECTORS_PER_UNIT];
	unsigned char BlockDeleted[MAX_SECTORS_PER_UNIT];
	unsigned int thisEUN, prevEUN, status;
	struct mtd_info *mtd = inftl->mbd.mtd;
	int block, silly;
	unsigned int targetEUN;
	struct inftl_oob oob;
	size_t retlen;

	DEBUG(MTD_DEBUG_LEVEL3, "INFTL: INFTL_foldchain(inftl=%p,thisVUC=%d,"
		"pending=%d)\n", inftl, thisVUC, pendingblock);

	memset(BlockMap, 0xff, sizeof(BlockMap));
	memset(BlockDeleted, 0, sizeof(BlockDeleted));

	thisEUN = targetEUN = inftl->VUtable[thisVUC];

	if (thisEUN == BLOCK_NIL) {
		printk(KERN_WARNING "INFTL: trying to fold non-existent "
		       "Virtual Unit Chain %d!\n", thisVUC);
		return BLOCK_NIL;
	}

	/*
	 * Scan to find the Erase Unit which holds the actual data for each
	 * 512-byte block within the Chain.
	 */
	silly = MAX_LOOPS;
	while (thisEUN < inftl->nb_blocks) {
		for (block = 0; block < inftl->EraseSize/SECTORSIZE; block ++) {
			if ((BlockMap[block] != BLOCK_NIL) ||
			    BlockDeleted[block])
				continue;

			if (inftl_read_oob(mtd, (thisEUN * inftl->EraseSize)
					   + (block * SECTORSIZE), 16, &retlen,
					   (char *)&oob) < 0)
				status = SECTOR_IGNORE;
			else
				status = oob.b.Status | oob.b.Status1;

			switch(status) {
			case SECTOR_FREE:
			case SECTOR_IGNORE:
				break;
			case SECTOR_USED:
				BlockMap[block] = thisEUN;
				continue;
			case SECTOR_DELETED:
				BlockDeleted[block] = 1;
				continue;
			default:
				printk(KERN_WARNING "INFTL: unknown status "
					"for block %d in EUN %d: %x\n",
					block, thisEUN, status);
				break;
			}
		}

		if (!silly--) {
			printk(KERN_WARNING "INFTL: infinite loop in Virtual "
				"Unit Chain 0x%x\n", thisVUC);
			return BLOCK_NIL;
		}

		thisEUN = inftl->PUtable[thisEUN];
	}

	/*
	 * OK. We now know the location of every block in the Virtual Unit
	 * Chain, and the Erase Unit into which we are supposed to be copying.
	 * Go for it.
	 */
	DEBUG(MTD_DEBUG_LEVEL1, "INFTL: folding chain %d into unit %d\n",
		thisVUC, targetEUN);

	for (block = 0; block < inftl->EraseSize/SECTORSIZE ; block++) {
		unsigned char movebuf[SECTORSIZE];
		int ret;

		/*
		 * If it's in the target EUN already, or if it's pending write,
		 * do nothing.
		 */
		if (BlockMap[block] == targetEUN || (pendingblock ==
		    (thisVUC * (inftl->EraseSize / SECTORSIZE) + block))) {
			continue;
		}

		/*
		 * Copy only in non free block (free blocks can only
                 * happen in case of media errors or deleted blocks).
		 */
		if (BlockMap[block] == BLOCK_NIL)
			continue;

		ret = mtd->read(mtd, (inftl->EraseSize * BlockMap[block]) +
				(block * SECTORSIZE), SECTORSIZE, &retlen,
				movebuf);
		if (ret < 0 && ret != -EUCLEAN) {
			ret = mtd->read(mtd,
					(inftl->EraseSize * BlockMap[block]) +
					(block * SECTORSIZE), SECTORSIZE,
					&retlen, movebuf);
			if (ret != -EIO)
				DEBUG(MTD_DEBUG_LEVEL1, "INFTL: error went "
				      "away on retry?\n");
		}
		memset(&oob, 0xff, sizeof(struct inftl_oob));
		oob.b.Status = oob.b.Status1 = SECTOR_USED;

		inftl_write(inftl->mbd.mtd, (inftl->EraseSize * targetEUN) +
			    (block * SECTORSIZE), SECTORSIZE, &retlen,
			    movebuf, (char *)&oob);
	}

	/*
	 * Newest unit in chain now contains data from _all_ older units.
	 * So go through and erase each unit in chain, oldest first. (This
	 * is important, by doing oldest first if we crash/reboot then it
	 * it is relatively simple to clean up the mess).
	 */
	DEBUG(MTD_DEBUG_LEVEL1, "INFTL: want to erase virtual chain %d\n",
		thisVUC);

	for (;;) {
		/* Find oldest unit in chain. */
		thisEUN = inftl->VUtable[thisVUC];
		prevEUN = BLOCK_NIL;
		while (inftl->PUtable[thisEUN] != BLOCK_NIL) {
			prevEUN = thisEUN;
			thisEUN = inftl->PUtable[thisEUN];
		}

		/* Check if we are all done */
		if (thisEUN == targetEUN)
			break;

		/* Unlink the last block from the chain. */
		inftl->PUtable[prevEUN] = BLOCK_NIL;

		/* Now try to erase it. */
		if (INFTL_formatblock(inftl, thisEUN) < 0) {
			/*
			 * Could not erase : mark block as reserved.
			 */
			inftl->PUtable[thisEUN] = BLOCK_RESERVED;
		} else {
			/* Correctly erased : mark it as free */
			inftl->PUtable[thisEUN] = BLOCK_FREE;
			inftl->numfreeEUNs++;
		}
	}

	return targetEUN;
}

static u16 INFTL_makefreeblock(struct INFTLrecord *inftl, unsigned pendingblock)
{
	/*
	 * This is the part that needs some cleverness applied.
	 * For now, I'm doing the minimum applicable to actually
	 * get the thing to work.
	 * Wear-levelling and other clever stuff needs to be implemented
	 * and we also need to do some assessment of the results when
	 * the system loses power half-way through the routine.
	 */
	u16 LongestChain = 0;
	u16 ChainLength = 0, thislen;
	u16 chain, EUN;

	DEBUG(MTD_DEBUG_LEVEL3, "INFTL: INFTL_makefreeblock(inftl=%p,"
		"pending=%d)\n", inftl, pendingblock);

	for (chain = 0; chain < inftl->nb_blocks; chain++) {
		EUN = inftl->VUtable[chain];
		thislen = 0;

		while (EUN <= inftl->lastEUN) {
			thislen++;
			EUN = inftl->PUtable[EUN];
			if (thislen > 0xff00) {
				printk(KERN_WARNING "INFTL: endless loop in "
					"Virtual Chain %d: Unit %x\n",
					chain, EUN);
				/*
				 * Actually, don't return failure.
				 * Just ignore this chain and get on with it.
				 */
				thislen = 0;
				break;
			}
		}

		if (thislen > ChainLength) {
			ChainLength = thislen;
			LongestChain = chain;
		}
	}

	if (ChainLength < 2) {
		printk(KERN_WARNING "INFTL: no Virtual Unit Chains available "
			"for folding. Failing request\n");
		return BLOCK_NIL;
	}

	return INFTL_foldchain(inftl, LongestChain, pendingblock);
}

static int nrbits(unsigned int val, int bitcount)
{
	int i, total = 0;

	for (i = 0; (i < bitcount); i++)
		total += (((0x1 << i) & val) ? 1 : 0);
	return total;
}

/*
 * INFTL_findwriteunit: Return the unit number into which we can write
 *                      for this block. Make it available if it isn't already.
 */
static inline u16 INFTL_findwriteunit(struct INFTLrecord *inftl, unsigned block)
{
	unsigned int thisVUC = block / (inftl->EraseSize / SECTORSIZE);
	unsigned int thisEUN, writeEUN, prev_block, status;
	unsigned long blockofs = (block * SECTORSIZE) & (inftl->EraseSize -1);
	struct mtd_info *mtd = inftl->mbd.mtd;
	struct inftl_oob oob;
	struct inftl_bci bci;
	unsigned char anac, nacs, parity;
	size_t retlen;
	int silly, silly2 = 3;

	DEBUG(MTD_DEBUG_LEVEL3, "INFTL: INFTL_findwriteunit(inftl=%p,"
		"block=%d)\n", inftl, block);

	do {
		/*
		 * Scan the media to find a unit in the VUC which has
		 * a free space for the block in question.
		 */
		writeEUN = BLOCK_NIL;
		thisEUN = inftl->VUtable[thisVUC];
		silly = MAX_LOOPS;

		while (thisEUN <= inftl->lastEUN) {
			inftl_read_oob(mtd, (thisEUN * inftl->EraseSize) +
				       blockofs, 8, &retlen, (char *)&bci);

			status = bci.Status | bci.Status1;
			DEBUG(MTD_DEBUG_LEVEL3, "INFTL: status of block %d in "
				"EUN %d is %x\n", block , writeEUN, status);

			switch(status) {
			case SECTOR_FREE:
				writeEUN = thisEUN;
				break;
			case SECTOR_DELETED:
			case SECTOR_USED:
				/* Can't go any further */
				goto hitused;
			case SECTOR_IGNORE:
				break;
			default:
				/*
				 * Invalid block. Don't use it any more.
				 * Must implement.
				 */
				break;
			}

			if (!silly--) {
				printk(KERN_WARNING "INFTL: infinite loop in "
					"Virtual Unit Chain 0x%x\n", thisVUC);
				return BLOCK_NIL;
			}

			/* Skip to next block in chain */
			thisEUN = inftl->PUtable[thisEUN];
		}

hitused:
		if (writeEUN != BLOCK_NIL)
			return writeEUN;


		/*
		 * OK. We didn't find one in the existing chain, or there
		 * is no existing chain. Allocate a new one.
		 */
		writeEUN = INFTL_findfreeblock(inftl, 0);

		if (writeEUN == BLOCK_NIL) {
			/*
			 * That didn't work - there were no free blocks just
			 * waiting to be picked up. We're going to have to fold
			 * a chain to make room.
			 */
			thisEUN = INFTL_makefreeblock(inftl, BLOCK_NIL);

			/*
			 * Hopefully we free something, lets try again.
			 * This time we are desperate...
			 */
			DEBUG(MTD_DEBUG_LEVEL1, "INFTL: using desperate==1 "
				"to find free EUN to accommodate write to "
				"VUC %d\n", thisVUC);
			writeEUN = INFTL_findfreeblock(inftl, 1);
			if (writeEUN == BLOCK_NIL) {
				/*
				 * Ouch. This should never happen - we should
				 * always be able to make some room somehow.
				 * If we get here, we've allocated more storage
				 * space than actual media, or our makefreeblock
				 * routine is missing something.
				 */
				printk(KERN_WARNING "INFTL: cannot make free "
					"space.\n");
#ifdef DEBUG
				INFTL_dumptables(inftl);
				INFTL_dumpVUchains(inftl);
#endif
				return BLOCK_NIL;
			}
		}

		/*
		 * Insert new block into virtual chain. Firstly update the
		 * block headers in flash...
		 */
		anac = 0;
		nacs = 0;
		thisEUN = inftl->VUtable[thisVUC];
		if (thisEUN != BLOCK_NIL) {
			inftl_read_oob(mtd, thisEUN * inftl->EraseSize
				       + 8, 8, &retlen, (char *)&oob.u);
			anac = oob.u.a.ANAC + 1;
			nacs = oob.u.a.NACs + 1;
		}

		prev_block = inftl->VUtable[thisVUC];
		if (prev_block < inftl->nb_blocks)
			prev_block -= inftl->firstEUN;

		parity = (nrbits(thisVUC, 16) & 0x1) ? 0x1 : 0;
		parity |= (nrbits(prev_block, 16) & 0x1) ? 0x2 : 0;
		parity |= (nrbits(anac, 8) & 0x1) ? 0x4 : 0;
		parity |= (nrbits(nacs, 8) & 0x1) ? 0x8 : 0;

		oob.u.a.virtualUnitNo = cpu_to_le16(thisVUC);
		oob.u.a.prevUnitNo = cpu_to_le16(prev_block);
		oob.u.a.ANAC = anac;
		oob.u.a.NACs = nacs;
		oob.u.a.parityPerField = parity;
		oob.u.a.discarded = 0xaa;

		inftl_write_oob(mtd, writeEUN * inftl->EraseSize + 8, 8,
				&retlen, (char *)&oob.u);

		/* Also back up header... */
		oob.u.b.virtualUnitNo = cpu_to_le16(thisVUC);
		oob.u.b.prevUnitNo = cpu_to_le16(prev_block);
		oob.u.b.ANAC = anac;
		oob.u.b.NACs = nacs;
		oob.u.b.parityPerField = parity;
		oob.u.b.discarded = 0xaa;

		inftl_write_oob(mtd, writeEUN * inftl->EraseSize +
				SECTORSIZE * 4 + 8, 8, &retlen, (char *)&oob.u);

		inftl->PUtable[writeEUN] = inftl->VUtable[thisVUC];
		inftl->VUtable[thisVUC] = writeEUN;

		inftl->numfreeEUNs--;
		return writeEUN;

	} while (silly2--);

	printk(KERN_WARNING "INFTL: error folding to make room for Virtual "
		"Unit Chain 0x%x\n", thisVUC);
	return BLOCK_NIL;
}

/*
 * Given a Virtual Unit Chain, see if it can be deleted, and if so do it.
 */
static void INFTL_trydeletechain(struct INFTLrecord *inftl, unsigned thisVUC)
{
	struct mtd_info *mtd = inftl->mbd.mtd;
	unsigned char BlockUsed[MAX_SECTORS_PER_UNIT];
	unsigned char BlockDeleted[MAX_SECTORS_PER_UNIT];
	unsigned int thisEUN, status;
	int block, silly;
	struct inftl_bci bci;
	size_t retlen;

	DEBUG(MTD_DEBUG_LEVEL3, "INFTL: INFTL_trydeletechain(inftl=%p,"
		"thisVUC=%d)\n", inftl, thisVUC);

	memset(BlockUsed, 0, sizeof(BlockUsed));
	memset(BlockDeleted, 0, sizeof(BlockDeleted));

	thisEUN = inftl->VUtable[thisVUC];
	if (thisEUN == BLOCK_NIL) {
		printk(KERN_WARNING "INFTL: trying to delete non-existent "
		       "Virtual Unit Chain %d!\n", thisVUC);
		return;
	}

	/*
	 * Scan through the Erase Units to determine whether any data is in
	 * each of the 512-byte blocks within the Chain.
	 */
	silly = MAX_LOOPS;
	while (thisEUN < inftl->nb_blocks) {
		for (block = 0; block < inftl->EraseSize/SECTORSIZE; block++) {
			if (BlockUsed[block] || BlockDeleted[block])
				continue;

			if (inftl_read_oob(mtd, (thisEUN * inftl->EraseSize)
					   + (block * SECTORSIZE), 8 , &retlen,
					  (char *)&bci) < 0)
				status = SECTOR_IGNORE;
			else
				status = bci.Status | bci.Status1;

			switch(status) {
			case SECTOR_FREE:
			case SECTOR_IGNORE:
				break;
			case SECTOR_USED:
				BlockUsed[block] = 1;
				continue;
			case SECTOR_DELETED:
				BlockDeleted[block] = 1;
				continue;
			default:
				printk(KERN_WARNING "INFTL: unknown status "
					"for block %d in EUN %d: 0x%x\n",
					block, thisEUN, status);
			}
		}

		if (!silly--) {
			printk(KERN_WARNING "INFTL: infinite loop in Virtual "
				"Unit Chain 0x%x\n", thisVUC);
			return;
		}

		thisEUN = inftl->PUtable[thisEUN];
	}

	for (block = 0; block < inftl->EraseSize/SECTORSIZE; block++)
		if (BlockUsed[block])
			return;

	/*
	 * For each block in the chain free it and make it available
	 * for future use. Erase from the oldest unit first.
	 */
	DEBUG(MTD_DEBUG_LEVEL1, "INFTL: deleting empty VUC %d\n", thisVUC);

	for (;;) {
		u16 *prevEUN = &inftl->VUtable[thisVUC];
		thisEUN = *prevEUN;

		/* If the chain is all gone already, we're done */
		if (thisEUN == BLOCK_NIL) {
			DEBUG(MTD_DEBUG_LEVEL2, "INFTL: Empty VUC %d for deletion was already absent\n", thisEUN);
			return;
		}

		/* Find oldest unit in chain. */
		while (inftl->PUtable[thisEUN] != BLOCK_NIL) {
			BUG_ON(thisEUN >= inftl->nb_blocks);

			prevEUN = &inftl->PUtable[thisEUN];
			thisEUN = *prevEUN;
		}

		DEBUG(MTD_DEBUG_LEVEL3, "Deleting EUN %d from VUC %d\n",
		      thisEUN, thisVUC);

		if (INFTL_formatblock(inftl, thisEUN) < 0) {
			/*
			 * Could not erase : mark block as reserved.
			 */
			inftl->PUtable[thisEUN] = BLOCK_RESERVED;
		} else {
			/* Correctly erased : mark it as free */
			inftl->PUtable[thisEUN] = BLOCK_FREE;
			inftl->numfreeEUNs++;
		}

		/* Now sort out whatever was pointing to it... */
		*prevEUN = BLOCK_NIL;

		/* Ideally we'd actually be responsive to new
		   requests while we're doing this -- if there's
		   free space why should others be made to wait? */
		cond_resched();
	}

	inftl->VUtable[thisVUC] = BLOCK_NIL;
}

static int INFTL_deleteblock(struct INFTLrecord *inftl, unsigned block)
{
	unsigned int thisEUN = inftl->VUtable[block / (inftl->EraseSize / SECTORSIZE)];
	unsigned long blockofs = (block * SECTORSIZE) & (inftl->EraseSize - 1);
	struct mtd_info *mtd = inftl->mbd.mtd;
	unsigned int status;
	int silly = MAX_LOOPS;
	size_t retlen;
	struct inftl_bci bci;

	DEBUG(MTD_DEBUG_LEVEL3, "INFTL: INFTL_deleteblock(inftl=%p,"
		"block=%d)\n", inftl, block);

	while (thisEUN < inftl->nb_blocks) {
		if (inftl_read_oob(mtd, (thisEUN * inftl->EraseSize) +
				   blockofs, 8, &retlen, (char *)&bci) < 0)
			status = SECTOR_IGNORE;
		else
			status = bci.Status | bci.Status1;

		switch (status) {
		case SECTOR_FREE:
		case SECTOR_IGNORE:
			break;
		case SECTOR_DELETED:
			thisEUN = BLOCK_NIL;
			goto foundit;
		case SECTOR_USED:
			goto foundit;
		default:
			printk(KERN_WARNING "INFTL: unknown status for "
				"block %d in EUN %d: 0x%x\n",
				block, thisEUN, status);
			break;
		}

		if (!silly--) {
			printk(KERN_WARNING "INFTL: infinite loop in Virtual "
				"Unit Chain 0x%x\n",
				block / (inftl->EraseSize / SECTORSIZE));
			return 1;
		}
		thisEUN = inftl->PUtable[thisEUN];
	}

foundit:
	if (thisEUN != BLOCK_NIL) {
		loff_t ptr = (thisEUN * inftl->EraseSize) + blockofs;

		if (inftl_read_oob(mtd, ptr, 8, &retlen, (char *)&bci) < 0)
			return -EIO;
		bci.Status = bci.Status1 = SECTOR_DELETED;
		if (inftl_write_oob(mtd, ptr, 8, &retlen, (char *)&bci) < 0)
			return -EIO;
		INFTL_trydeletechain(inftl, block / (inftl->EraseSize / SECTORSIZE));
	}
	return 0;
}

static int inftl_writeblock(struct mtd_blktrans_dev *mbd, unsigned long block,
			    char *buffer)
{
	struct INFTLrecord *inftl = (void *)mbd;
	unsigned int writeEUN;
	unsigned long blockofs = (block * SECTORSIZE) & (inftl->EraseSize - 1);
	size_t retlen;
	struct inftl_oob oob;
	char *p, *pend;

	DEBUG(MTD_DEBUG_LEVEL3, "INFTL: inftl_writeblock(inftl=%p,block=%ld,"
		"buffer=%p)\n", inftl, block, buffer);

	/* Is block all zero? */
	pend = buffer + SECTORSIZE;
	for (p = buffer; p < pend && !*p; p++)
		;

	if (p < pend) {
		writeEUN = INFTL_findwriteunit(inftl, block);

		if (writeEUN == BLOCK_NIL) {
			printk(KERN_WARNING "inftl_writeblock(): cannot find "
				"block to write to\n");
			/*
			 * If we _still_ haven't got a block to use,
			 * we're screwed.
			 */
			return 1;
		}

		memset(&oob, 0xff, sizeof(struct inftl_oob));
		oob.b.Status = oob.b.Status1 = SECTOR_USED;

		inftl_write(inftl->mbd.mtd, (writeEUN * inftl->EraseSize) +
			    blockofs, SECTORSIZE, &retlen, (char *)buffer,
			    (char *)&oob);
		/*
		 * need to write SECTOR_USED flags since they are not written
		 * in mtd_writeecc
		 */
	} else {
		INFTL_deleteblock(inftl, block);
	}

	return 0;
}

static int inftl_readblock(struct mtd_blktrans_dev *mbd, unsigned long block,
			   char *buffer)
{
	struct INFTLrecord *inftl = (void *)mbd;
	unsigned int thisEUN = inftl->VUtable[block / (inftl->EraseSize / SECTORSIZE)];
	unsigned long blockofs = (block * SECTORSIZE) & (inftl->EraseSize - 1);
	struct mtd_info *mtd = inftl->mbd.mtd;
	unsigned int status;
	int silly = MAX_LOOPS;
	struct inftl_bci bci;
	size_t retlen;

	DEBUG(MTD_DEBUG_LEVEL3, "INFTL: inftl_readblock(inftl=%p,block=%ld,"
		"buffer=%p)\n", inftl, block, buffer);

	while (thisEUN < inftl->nb_blocks) {
		if (inftl_read_oob(mtd, (thisEUN * inftl->EraseSize) +
				  blockofs, 8, &retlen, (char *)&bci) < 0)
			status = SECTOR_IGNORE;
		else
			status = bci.Status | bci.Status1;

		switch (status) {
		case SECTOR_DELETED:
			thisEUN = BLOCK_NIL;
			goto foundit;
		case SECTOR_USED:
			goto foundit;
		case SECTOR_FREE:
		case SECTOR_IGNORE:
			break;
		default:
			printk(KERN_WARNING "INFTL: unknown status for "
				"block %ld in EUN %d: 0x%04x\n",
				block, thisEUN, status);
			break;
		}

		if (!silly--) {
			printk(KERN_WARNING "INFTL: infinite loop in "
				"Virtual Unit Chain 0x%lx\n",
				block / (inftl->EraseSize / SECTORSIZE));
			return 1;
		}

		thisEUN = inftl->PUtable[thisEUN];
	}

foundit:
	if (thisEUN == BLOCK_NIL) {
		/* The requested block is not on the media, return all 0x00 */
		memset(buffer, 0, SECTORSIZE);
	} else {
		size_t retlen;
		loff_t ptr = (thisEUN * inftl->EraseSize) + blockofs;
		int ret = mtd->read(mtd, ptr, SECTORSIZE, &retlen, buffer);

		/* Handle corrected bit flips gracefully */
		if (ret < 0 && ret != -EUCLEAN)
			return -EIO;
	}
	return 0;
}

static int inftl_getgeo(struct mtd_blktrans_dev *dev, struct hd_geometry *geo)
{
	struct INFTLrecord *inftl = (void *)dev;

	geo->heads = inftl->heads;
	geo->sectors = inftl->sectors;
	geo->cylinders = inftl->cylinders;

	return 0;
}

static struct mtd_blktrans_ops inftl_tr = {
	.name		= "inftl",
	.major		= INFTL_MAJOR,
	.part_bits	= INFTL_PARTN_BITS,
	.blksize 	= 512,
	.getgeo		= inftl_getgeo,
	.readsect	= inftl_readblock,
	.writesect	= inftl_writeblock,
	.add_mtd	= inftl_add_mtd,
	.remove_dev	= inftl_remove_dev,
	.owner		= THIS_MODULE,
};

static int __init init_inftl(void)
{
	return register_mtd_blktrans(&inftl_tr);
}

static void __exit cleanup_inftl(void)
{
	deregister_mtd_blktrans(&inftl_tr);
}

module_init(init_inftl);
module_exit(cleanup_inftl);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Greg Ungerer <gerg@snapgear.com>, David Woodhouse <dwmw2@infradead.org>, Fabrice Bellard <fabrice.bellard@netgem.com> et al.");
MODULE_DESCRIPTION("Support code for Inverse Flash Translation Layer, used on M-Systems DiskOnChip 2000, Millennium and Millennium Plus");