nftlcore.c

linux下的MTD设备驱动源代码,配合jffs2 yaffss2文件系统.

	   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
			 * FixMe: Update Bad Unit Table on disk
			 */
			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;
}

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;
	u8 eccbuf[6];

	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;
	}

	MTD_WRITEECC(nftl->mbd.mtd, (writeEUN * nftl->EraseSize) + blockofs,
		     512, &retlen, (char *)buffer, (char *)eccbuf, NAND_ECC_DISKONCHIP);
        /* no need to write SECTOR_USED flags since they are 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;
		u_char eccbuf[6];
		if (MTD_READECC(nftl->mbd.mtd, ptr, 512, &retlen, buffer, eccbuf, NAND_ECC_DISKONCHIP))
			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
 *
 ****************************************************************************/


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[];

int __init init_nftl(void)
{
	printk(KERN_INFO "NFTL driver: nftlcore.c $Revision: 1.94 $, 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 <[e-mail]>, Fabrice Bellard <[e-mail]> et al.");
MODULE_DESCRIPTION("Support code for NAND Flash Translation Layer, used on M-Systems DiskOnChip 2000 and Millennium");