aboutsummaryrefslogtreecommitdiffstats
path: root/drivers/mtd/nftlcore.c
blob: d7cd5fa16ba445e8d854760de615e7ec15821949 (plain)
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
/* Linux driver for NAND Flash Translation Layer      */
/* (c) 1999 Machine Vision Holdings, Inc.             */
/* Author: David Woodhouse <dwmw2@infradead.org>      */
/* $Id: nftlcore.c,v 1.98 2005/11/07 11:14:21 gleixner Exp $ */

/*
  The contents of this file are distributed under the GNU General
  Public License version 2. The author places no additional
  restrictions of any kind on it.
 */

#define PRERELEASE

#include <linux/config.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <asm/errno.h>
#include <asm/io.h>
#include <asm/uaccess.h>
#include <linux/miscdevice.h>
#include <linux/pci.h>
#include <linux/delay.h>
#include <linux/slab.h>
#include <linux/sched.h>
#include <linux/init.h>
#include <linux/hdreg.h>

#include <linux/kmod.h>
#include <linux/mtd/mtd.h>
#include <linux/mtd/nand.h>
#include <linux/mtd/nftl.h>
#include <linux/mtd/blktrans.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 nftl_add_mtd(struct mtd_blktrans_ops *tr, struct mtd_info *mtd)
{
	struct NFTLrecord *nftl;
	unsigned long temp;

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

	if (!mtd->block_isbad) {
		printk(KERN_ERR
"NFTL 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_LEVEL1, "NFTL: add_mtd for %s\n", mtd->name);

	nftl = kmalloc(sizeof(struct NFTLrecord), GFP_KERNEL);

	if (!nftl) {
		printk(KERN_WARNING "NFTL: out of memory for data structures\n");
		return;
	}
	memset(nftl, 0, sizeof(*nftl));

	nftl->mbd.mtd = mtd;
	nftl->mbd.devnum = -1;
	nftl->mbd.blksize = 512;
	nftl->mbd.tr = tr;
	memcpy(&nftl->oobinfo, &mtd->oobinfo, sizeof(struct nand_oobinfo));
	nftl->oobinfo.useecc = MTD_NANDECC_PLACEONLY;

        if (NFTL_mount(nftl) < 0) {
		printk(KERN_WARNING "NFTL: could not mount device\n");
		kfree(nftl);
		return;
        }

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

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

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

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

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

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

static void nftl_remove_dev(struct mtd_blktrans_dev *dev)
{
	struct NFTLrecord *nftl = (void *)dev;

	DEBUG(MTD_DEBUG_LEVEL1, "NFTL: remove_dev (i=%d)\n", dev->devnum);

	del_mtd_blktrans_dev(dev);
	kfree(nftl->ReplUnitTable);
	kfree(nftl->EUNtable);
	kfree(nftl);
}

#ifdef CONFIG_NFTL_RW

/* Actual NFTL access routines */
/* NFTL_findfreeblock: Find a free Erase Unit on the NFTL partition. This function is used
 *	when the give Virtual Unit Chain
 */
static u16 NFTL_findfreeblock(struct NFTLrecord *nftl, int desperate )
{
	/* For a given Virtual Unit Chain: find or create a free block and
	   add it to the chain */
	/* We're passed the number of the last EUN in the chain, to save us from
	   having to look it up again */
	u16 pot = nftl->LastFreeEUN;
	int silly = nftl->nb_blocks;

	/* Normally, we force a fold to happen before we run out of free blocks completely */
	if (!desperate && nftl->numfreeEUNs < 2) {
		DEBUG(MTD_DEBUG_LEVEL1, "NFTL_findfreeblock: there are too few free EUNs\n");
		return 0xffff;
	}

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

		/* This will probably point to the MediaHdr unit itself,
		   right at the beginning of the partition. But that unit
		   (and the backup unit too) should have the UCI set
		   up so that it's not selected for overwriting */
		if (++pot > nftl->lastEUN)
			pot = le16_to_cpu(nftl->MediaHdr.FirstPhysicalEUN);

		if (!silly--) {
			printk("Argh! No free blocks found! LastFreeEUN = %d, "
			       "FirstEUN = %d\n", nftl->LastFreeEUN,
			       le16_to_cpu(nftl->MediaHdr.FirstPhysicalEUN));
			return 0xffff;
		}
	} while (pot != nftl->LastFreeEUN);

	return 0xffff;
}

static u16 NFTL_foldchain (struct NFTLrecord *nftl, unsigned thisVUC, unsigned pendingblock )
{
	u16 BlockMap[MAX_SECTORS_PER_UNIT];
	unsigned char BlockLastState[MAX_SECTORS_PER_UNIT];
	unsigned char BlockFreeFound[MAX_SECTORS_PER_UNIT];
	unsigned int thisEUN;
	int block;
	int silly;
	unsigned int targetEUN;
	struct nftl_oob oob;
	int inplace = 1;
        size_t retlen;

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

	thisEUN = nftl->EUNtable[thisVUC];

	if (thisEUN == BLOCK_NIL) {
		printk(KERN_WARNING "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;
	targetEUN = BLOCK_NIL;
	while (thisEUN <= nftl->lastEUN ) {
                unsigned int status, foldmark;

		targetEUN = thisEUN;
		for (block = 0; block < nftl->EraseSize / 512; block ++) {
			MTD_READOOB(nftl->mbd.mtd,
				    (thisEUN * nftl->EraseSize) + (block * 512),
				    16 , &retlen, (char *)&oob);
			if (block == 2) {
                                foldmark = oob.u.c.FoldMark | oob.u.c.FoldMark1;
                                if (foldmark == FOLD_MARK_IN_PROGRESS) {
                                        DEBUG(MTD_DEBUG_LEVEL1,
                                              "Write Inhibited on EUN %d\n", thisEUN);
					inplace = 0;
				} else {
					/* There's no other reason not to do inplace,
					   except ones that come later. So we don't need
					   to preserve inplace */
					inplace = 1;
				}
			}
                        status = oob.b.Status | oob.b.Status1;
			BlockLastState[block] = status;

			switch(status) {
			case SECTOR_FREE:
				BlockFreeFound[block] = 1;
				break;

			case SECTOR_USED:
				if (!BlockFreeFound[block])
					BlockMap[block] = thisEUN;
				else
					printk(KERN_WARNING
					       "SECTOR_USED found after SECTOR_FREE "
					       "in Virtual Unit Chain %d for block %d\n",
					       thisVUC, block);
				break;
			case SECTOR_DELETED:
				if (!BlockFreeFound[block])
					BlockMap[block] = BLOCK_NIL;
				else
					printk(KERN_WARNING
					       "SECTOR_DELETED found after SECTOR_FREE "
					       "in Virtual Unit Chain %d for block %d\n",
					       thisVUC, block);
				break;

			case SECTOR_IGNORE:
				break;
			default:
				printk("Unknown status for block %d in EUN %d: %x\n",
				       block, thisEUN, status);
			}
		}

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

		thisEUN = nftl->ReplUnitTable[thisEUN];
	}

	if (inplace) {
		/* We're being asked to be a fold-in-place. Check
		   that all blocks which actually have data associated
		   with them (i.e. BlockMap[block] != BLOCK_NIL) are
		   either already present or SECTOR_FREE in the target
		   block. If not, we're going to have to fold out-of-place
		   anyway.
		*/
		for (block = 0; block < nftl->EraseSize / 512 ; block++) {
			if (BlockLastState[block] != SECTOR_FREE &&
			    BlockMap[block] != BLOCK_NIL &&
			    BlockMap[block] != targetEUN) {
				DEBUG(MTD_DEBUG_LEVEL1, "Setting inplace to 0. VUC %d, "
				      "block %d was %x lastEUN, "
				      "and is in EUN %d (%s) %d\n",
				      thisVUC, block, BlockLastState[block],
				      BlockMap[block],
				      BlockMap[block]== targetEUN ? "==" : "!=",
				      targetEUN);
				inplace = 0;
				break;
			}
		}

		if (pendingblock >= (thisVUC * (nftl->EraseSize / 512)) &&
		    pendingblock < ((thisVUC + 1)* (nftl->EraseSize / 512)) &&
		    BlockLastState[pendingblock - (thisVUC * (nftl->EraseSize / 512))] !=
		    SECTOR_FREE) {
			DEBUG(MTD_DEBUG_LEVEL1, "Pending write not free in EUN %d. "
			      "Folding out of place.\n", targetEUN);
			inplace = 0;
		}
	}

	if (!inplace) {
		DEBUG(MTD_DEBUG_LEVEL1, "Cannot fold Virtual Unit Chain %d in place. "
		      "Trying out-of-place\n", thisVUC);
		/* We need to find a targetEUN to fold into. */
		targetEUN = NFTL_findfreeblock(nftl, 1);
		if (targetEUN == BLOCK_NIL) {
			/* Ouch. Now we're screwed. We need to do a
			   fold-in-place of another chain to make room
			   for this one. We need a better way of selecting
			   which chain to fold, because makefreeblock will
			   only ask us to fold the same one again.
			*/
			printk(KERN_WARNING
			       "NFTL_findfreeblock(desperate) returns 0xffff.\n");
			return BLOCK_NIL;
		}
	} else {
            /* We put a fold mark in the chain we are folding only if
               we fold in place to help the mount check code. If we do
               not fold in place, it is possible to find the valid
               chain by selecting the longer one */
            oob.u.c.FoldMark = oob.u.c.FoldMark1 = cpu_to_le16(FOLD_MARK_IN_PROGRESS);
            oob.u.c.unused = 0xffffffff;
            MTD_WRITEOOB(nftl->mbd.mtd, (nftl->EraseSize * targetEUN) + 2 * 512 + 8,
                         8, &retlen, (char *)&oob.u);
        }

	/* 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,"Folding chain %d into unit %d\n", thisVUC, targetEUN);
	for (block = 0; block < nftl->EraseSize / 512 ; block++) {
		unsigned char movebuf[512];
		int ret;

		/* If it's in the target EUN already, or if it's pending write, do nothing */
		if (BlockMap[block] == targetEUN ||
		    (pendingblock == (thisVUC * (nftl->EraseSize / 512) + 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(nftl->mbd.mtd, (nftl->EraseSize * BlockMap[block]) + (block * 512),
				  512, &retlen, movebuf);
                if (ret < 0) {
                    ret = MTD_READ(nftl->mbd.mtd, (nftl->EraseSize * BlockMap[block])
                                      + (block * 512), 512, &retlen,
                                      movebuf);
                    if (ret != -EIO)
                        printk("Error went away on retry.\n");
                }
		memset(&oob, 0xff, sizeof(struct nftl_oob));
		oob.b.Status = oob.b.Status1 = SECTOR_USED;
                MTD_WRITEECC(nftl->mbd.mtd, (nftl->EraseSize * targetEUN) + (block * 512),
                             512, &retlen, movebuf, (char *)&oob, &nftl->oobinfo);
	}

        /* add the header so that it is now a valid chain */
        oob.u.a.VirtUnitNum = oob.u.a.SpareVirtUnitNum
                = cpu_to_le16(thisVUC);
        oob.u.a.ReplUnitNum = oob.u.a.SpareReplUnitNum = 0xffff;

        MTD_WRITEOOB(nftl->mbd.mtd, (nftl->EraseSize * targetEUN) + 8,
                     8, &retlen, (char *)&oob.u);

	/* OK. We've moved the whole lot into the new block. Now we have to free the original blocks. */

	/* At this point, we have two different chains for this Virtual Unit, and no way to tell
	   them apart. If we crash now, we get confused. However, both contain the same data, so we
	   shouldn't actually lose data in this case. It's just that when we load up on a medium which
	   has duplicate chains, we need to free one of the chains because it's not necessary any more.
	*/
	thisEUN = nftl->EUNtable[thisVUC];
	DEBUG(MTD_DEBUG_LEVEL1,"Want to erase\n");

	/* For each block in the old chain (except the targetEUN of course),
	   free it and make it available for future use */
	while (thisEUN <= nftl->lastEUN && thisEUN != targetEUN) {
		unsigned int EUNtmp;

                EUNtmp = nftl->ReplUnitTable[thisEUN];

                if (NFTL_formatblock(nftl, thisEUN) < 0) {
			/* could not erase : mark block as reserved
			 */
			nftl->ReplUnitTable[thisEUN] = BLOCK_RESERVED;
                } else {
			/* correctly erased : mark it as free */
			nftl->ReplUnitTable[thisEUN] = BLOCK_FREE;
			nftl->numfreeEUNs++;
                }
                thisEUN = EUNtmp;
	}

	/* Make this the new start of chain for thisVUC */
	nftl->ReplUnitTable[targetEUN] = BLOCK_NIL;
	nftl->EUNtable[thisVUC] = targetEUN;

	return targetEUN;
}

static u16 NFTL_makefreeblock( struct NFTLrecord *nftl , 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;

	for (chain = 0; chain < le32_to_cpu(nftl->MediaHdr.FormattedSize) / nftl->EraseSize; chain++) {
		EUN = nftl->EUNtable[chain];
		thislen = 0;

		while (EUN <= nftl->lastEUN) {
			thislen++;
			//printk("VUC %d reaches len %d with EUN %d\n", chain, thislen, EUN);
			EUN = nftl->ReplUnitTable[EUN] & 0x7fff;
			if (thislen > 0xff00) {
				printk("Endless loop in Virtual Chain %d: Unit %x\n",
				       chain, EUN);
			}
			if (thislen > 0xff10) {
				/* Actually, don't return failure. Just ignore this chain and
				   get on with it. */
				thislen = 0;
				break;
			}
		}

		if (thislen > ChainLength) {
			//printk("New longest chain is %d with length %d\n", chain, thislen);
			ChainLength = thislen;
			LongestChain = chain;
		}
	}

	if (ChainLength < 2) {
		printk(KERN_WARNING "No Virtual Unit Chains available for folding. "
		       "Failing request\n");
		return 0xffff;
	}

	return NFTL_foldchain (nftl, LongestChain, pendingblock);
}

/* NFTL_findwriteunit: Return the unit number into which we can write
                       for this block. Make it available if it isn't already
*/
static inline u16 NFTL_findwriteunit(struct NFTLrecord *nftl, unsigned block)
{
	u16 lastEUN;
	u16 thisVUC = block / (nftl->EraseSize / 512);
	unsigned int writeEUN;
	unsigned long blockofs = (block * 512) & (nftl->EraseSize -1);
	size_t retlen;
	int silly, silly2 = 3;
	struct nftl_oob oob;

	do {
		/* Scan the media to find a unit in the VUC which has
		   a free space for the block in question.
		*/

		/* This condition catches the 0x[7f]fff cases, as well as
		   being a sanity check for past-end-of-media access
		*/
		lastEUN = BLOCK_NIL;
		writeEUN = nftl->EUNtable[thisVUC];
                silly = MAX_LOOPS;
		while (writeEUN <= nftl->lastEUN) {
			struct nftl_bci bci;
			size_t retlen;
                        unsigned int status;

			lastEUN = writeEUN;

			MTD_READOOB(nftl->mbd.mtd, (writeEUN * nftl->EraseSize) + blockofs,
				    8, &retlen, (char *)&bci);

			DEBUG(MTD_DEBUG_LEVEL2, "Status of block %d in EUN %d is %x\n",
			      block , writeEUN, le16_to_cpu(bci.Status));

                        status = bci.Status | bci.Status1;
			switch(status) {
			case SECTOR_FREE:
				return writeEUN;

			case SECTOR_DELETED:
			case SECTOR_USED:
			case SECTOR_IGNORE:
				break;
			default:
				// Invalid block. Don't use it any more. Must implement.
				break;
			}

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

			/* Skip to next block in chain */
			writeEUN = nftl->ReplUnitTable[writeEUN];
		}

		/* OK. We didn't find one in the existing chain, or there
		   is no existing chain. */

		/* Try to find an already-free block */
		writeEUN = NFTL_findfreeblock(nftl, 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.
			*/

			/* First remember the start of this chain */
			//u16 startEUN = nftl->EUNtable[thisVUC];

			//printk("Write to VirtualUnitChain %d, calling makefreeblock()\n", thisVUC);
			writeEUN = NFTL_makefreeblock(nftl, 0xffff);

			if (writeEUN == BLOCK_NIL) {
				/* OK, we accept that the above comment is
				   lying - there may have been free blocks
				   last time we called NFTL_findfreeblock(),
				   but they are reserved for when we're
				   desperate. Well, now we're desperate.
				*/
				DEBUG(MTD_DEBUG_LEVEL1, "Using desperate==1 to find free EUN to accommodate write to VUC %d\n", thisVUC);
				writeEUN = NFTL_findfreeblock(nftl, 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 "Cannot make free space.\n");
				return BLOCK_NIL;
			}
			//printk("Restarting scan\n");
			lastEUN = BLOCK_NIL;
			continue;
		}

		/* We've found a free block. Insert it into the chain. */

		if (lastEUN != BLOCK_NIL) {
                    thisVUC |= 0x8000; /* It's a replacement block */
		} else {
                    /* The first block in a new chain */
                    nftl->EUNtable[thisVUC] = writeEUN;
		}

		/* set up the actual EUN we're writing into */
		/* Both in our cache... */
		nftl->ReplUnitTable[writeEUN] = BLOCK_NIL;

		/* ... and on the flash itself */
		MTD_READOOB(nftl->mbd.mtd, writeEUN * nftl->EraseSize + 8, 8,
			    &retlen, (char *)&oob.u);

		oob.u.a.VirtUnitNum = oob.u.a.SpareVirtUnitNum = cpu_to_le16(thisVUC);

		MTD_WRITEOOB(nftl->mbd.mtd, writeEUN * nftl->EraseSize + 8, 8,
                             &retlen, (char *)&oob.u);

                /* we link the new block to the chain only after the
                   block is ready. It avoids the case where the chain
                   could point to a free block */
                if (lastEUN != BLOCK_NIL) {
			/* Both in our cache... */
			nftl->ReplUnitTable[lastEUN] = writeEUN;
			/* ... and on the flash itself */
			MTD_READOOB(nftl->mbd.mtd, (lastEUN * nftl->EraseSize) + 8,
				    8, &retlen, (char *)&oob.u);

			oob.u.a.ReplUnitNum = oob.u.a.SpareReplUnitNum
				= cpu_to_le16(writeEUN);

			MTD_WRITEOOB(nftl->mbd.mtd, (lastEUN * nftl->EraseSize) + 8,
				     8, &retlen, (char *)&oob.u);
		}

		return writeEUN;

	} while (silly2--);

	printk(KERN_WARNING "Error folding to make room for Virtual Unit Chain 0x%x\n",
	       thisVUC);
	return 0xffff;
}

static int nftl_writeblock(struct mtd_blktrans_dev *mbd, unsigned long block,
			   char *buffer)
{
	struct NFTLrecord *nftl = (void *)mbd;
	u16 writeEUN;
	unsigned long blockofs = (block * 512) & (nftl->EraseSize - 1);
	size_t retlen;
	struct nftl_oob oob;

	writeEUN = NFTL_findwriteunit(nftl, block);

	if (writeEUN == BLOCK_NIL) {
		printk(KERN_WARNING
		       "NFTL_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 nftl_oob));
	oob.b.Status = oob.b.Status1 = SECTOR_USED;
	MTD_WRITEECC(nftl->mbd.mtd, (writeEUN * nftl->EraseSize) + blockofs,
		     512, &retlen, (char *)buffer, (char *)&oob, &nftl->oobinfo);
        /* need to write SECTOR_USED flags since they are not written in mtd_writeecc */

	return 0;
}
#endif /* CONFIG_NFTL_RW */

static int nftl_readblock(struct mtd_blktrans_dev *mbd, unsigned long block,
			  char *buffer)
{
	struct NFTLrecord *nftl = (void *)mbd;
	u16 lastgoodEUN;
	u16 thisEUN = nftl->EUNtable[block / (nftl->EraseSize / 512)];
	unsigned long blockofs = (block * 512) & (nftl->EraseSize - 1);
        unsigned int status;
	int silly = MAX_LOOPS;
        size_t retlen;
        struct nftl_bci bci;

	lastgoodEUN = BLOCK_NIL;

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

			switch (status) {
			case SECTOR_FREE:
				/* no modification of a sector should follow a free sector */
				goto the_end;
			case SECTOR_DELETED:
				lastgoodEUN = BLOCK_NIL;
				break;
			case SECTOR_USED:
				lastgoodEUN = thisEUN;
				break;
			case SECTOR_IGNORE:
				break;
			default:
				printk("Unknown status for block %ld in EUN %d: %x\n",
				       block, thisEUN, status);
				break;
			}

			if (!silly--) {
				printk(KERN_WARNING "Infinite loop in Virtual Unit Chain 0x%lx\n",
				       block / (nftl->EraseSize / 512));
				return 1;
			}
			thisEUN = nftl->ReplUnitTable[thisEUN];
		}
        }

 the_end:
	if (lastgoodEUN == BLOCK_NIL) {
		/* the requested block is not on the media, return all 0x00 */
		memset(buffer, 0, 512);
	} else {
		loff_t ptr = (lastgoodEUN * nftl->EraseSize) + blockofs;
		size_t retlen;
		if (MTD_READ(nftl->mbd.mtd, ptr, 512, &retlen, buffer))
			return -EIO;
	}
	return 0;
}

static int nftl_getgeo(struct mtd_blktrans_dev *dev,  struct hd_geometry *geo)
{
	struct NFTLrecord *nftl = (void *)dev;

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

	return 0;
}

/****************************************************************************
 *
 * Module stuff
 *
 ****************************************************************************/


static struct mtd_blktrans_ops nftl_tr = {
	.name		= "nftl",
	.major		= NFTL_MAJOR,
	.part_bits	= NFTL_PARTN_BITS,
	.getgeo		= nftl_getgeo,
	.readsect	= nftl_readblock,
#ifdef CONFIG_NFTL_RW
	.writesect	= nftl_writeblock,
#endif
	.add_mtd	= nftl_add_mtd,
	.remove_dev	= nftl_remove_dev,
	.owner		= THIS_MODULE,
};

extern char nftlmountrev[];

static int __init init_nftl(void)
{
	printk(KERN_INFO "NFTL driver: nftlcore.c $Revision: 1.98 $, nftlmount.c %s\n", nftlmountrev);

	return register_mtd_blktrans(&nftl_tr);
}

static void __exit cleanup_nftl(void)
{
	deregister_mtd_blktrans(&nftl_tr);
}

module_init(init_nftl);
module_exit(cleanup_nftl);

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