Re: FAT vs jFFS2 for NAND.

[Claudio Lanconelli <lanconelli.claudio@eptar.com>]

[-- Attachment #1: Type: text/plain, Size: 537 bytes --]

Han Chang wrote:
> Thanks! The reason for using FAT on the NAND is when the device has the NAND 
> is connected to a PC via USB, it can appear to be storage device read by the 
> PC user directly.
>
> Could you provide more details on how to get this SmartMedia Format driver?
>
> Anyone know any other source base which I can leverage to do the job?
>   
Hi,
I made some time ago a Smartmedia read only layer for MTD, since I can't 
make the current ssfdc.c working.
I attach it if you want to give a look.

Cheers,
Claudio Lanconelli


[-- Attachment #2: ssfdc_ro.c --]
[-- Type: text/x-csrc, Size: 13071 bytes --]

/*
 * Linux driver for SSFDC Flash Translation Layer (Read only)
 * (c) 2005 Eptar srl
 * Author: Claudio Lanconelli <lanconelli.claudio@eptar.com>
 *
 * Based on NTFL and MTDBLOCK_RO drivers
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * $Id: ssfdc_ro.c,v 1.5 2005/11/28 13:54:08 claudio Exp $
 */

#include <linux/config.h>
#include <linux/kernel.h>
#include <linux/module.h>

#include <linux/init.h>
#include <linux/slab.h>
#include <linux/hdreg.h>
#include <linux/mtd/mtd.h>
#include <linux/mtd/nand.h>
#include <linux/mtd/blktrans.h>

#undef 	ENABLE_GETGEO

#undef DEBUG
#define DEBUG(n, args...)					\
 	do {									\
		if (n <= SSFDC_RO_DEBUG_VERBOSE)	\
			printk(KERN_INFO args);			\
	} while(0)

#define SSFDC_RO_DEBUG_VERBOSE	0

struct ssfdcr_record {
	struct mtd_blktrans_dev mbd;
	int usecount;
#ifdef ENABLE_GETGEO
	unsigned char heads;
	unsigned char sectors;
	unsigned short cylinders;
#endif
	int cis_block;						//block n. containing CIS/IDI
	int erase_size;						//phys_block_size
	unsigned short *logic_block_map;	//all zones (max 8192 phys blocks on the 128MB)
	int map_len;						//n. phys_blocks on the card
};

static const struct nand_oobinfo ssfdc_oobinfo = {
	.useecc = MTD_NANDECC_PLACEONLY,
	.eccbytes = 6,
	.eccpos = {14, 13, 15, 9, 8, 10}
};

#define SSFDCR_MAJOR		44
#define SSFDCR_PARTN_BITS	3

#define SECTOR_SIZE		512
#define SECTOR_SHIFT	9
#define OOB_SIZE		16

#define MAX_LOGIC_BLK_PER_ZONE	1000
#define MAX_PHYS_BLK_PER_ZONE	1024

#define ArraySize(x)	( sizeof(x) / sizeof((x)[0]) )

#define KB(x)	( (x) * 1024L )
#define MB(x)	( KB(x) * 1024L )

/** CHS Table
			1MB		2MB		4MB		8MB		16MB	32MB	64MB	128MB
NCylinder	125		125		250		250		500		500		500		500
NHead		4		4		4		4		4		8		8		16
NSector		4		8		8		16		16		16		32		32
SumSector	2,000	4,000	8,000	16,000	32,000	64,000	128,000	256,000
SectorSize	512		512		512		512		512		512		512		512
**/

#ifdef ENABLE_GETGEO

typedef struct {
	unsigned long size;
	unsigned short cyl;
	unsigned char head;
	unsigned char sec;
} chs_entry_t;

//Must be ordered by size
static const chs_entry_t chs_table[] = {
	{ MB(  1), 125,  4,  4 },
	{ MB(  2), 125,  4,  8 },
	{ MB(  4), 250,  4,  8 },
	{ MB(  8), 250,  4, 16 },
	{ MB( 16), 500,  4, 16 },
	{ MB( 32), 500,  8, 16 },
	{ MB( 64), 500,  8, 32 },
	{ MB(128), 500, 16, 32 },
	{ 0 },
};

static int get_chs(unsigned long size, unsigned short *cyl, unsigned char *head, unsigned char *sec)
{
	int k;
	int found = 0;

	k = 0;
	while ( chs_table[k].size > 0 && size > chs_table[k].size )
		k++;

	if ( chs_table[k].size > 0 )
	{
		if (cyl)
			*cyl = chs_table[k].cyl;
		if (head)
			*head = chs_table[k].head;
		if (sec)
			*sec = chs_table[k].sec;
		found = 1;
	}

	return found;
}
#endif


static const unsigned char nibble_count_bits[16] = {
	0,1,1,2,1,2,2,3,1,2,2,3,2,3,3,4
};

//Counts bit 1 in a byte. Use look up table to speed up count
static int byte_count_bits(unsigned char val)
{
	return nibble_count_bits[val >> 4] + nibble_count_bits[val & 0x0f];
}

static const unsigned char cis_numbers[] = {
	0x01, 0x03, 0xD9, 0x01, 0xFF, 0x18, 0x02, 0xDF, 0x01, 0x20
};

#define OOB_BLOCKSTATUS_OFFSET	5

#define block_is_bad(x)		( byte_count_bits(x) < 7 )
#define block_is_good(x)	( !block_is_bad(x) )

//Read and check for a valid CIS sector
static int get_valid_cis_sector(struct mtd_info *mtd)
{
	int ret, k, cis_sector;
	size_t retlen;
	loff_t offset;
	unsigned char sect_buf[SECTOR_SIZE];
	unsigned char oob_buf[OOB_SIZE];

	//Look for CIS/IDI sector on the first GOOD block (give up after 4 bad blocks)
	//If the first good block doesn't contain CIS number the flash is not SSFDC formatted
	cis_sector = -1;
	for (k = 0, offset = 0; k < 4; k++, offset += mtd->erasesize)
	{
		ret = MTD_READOOB(mtd, offset, OOB_SIZE, &retlen, oob_buf);
		if ( ret < 0 || retlen != OOB_SIZE )
		{
			DEBUG(MTD_DEBUG_LEVEL0, "SSFDC_RO: can't read OOB data on sector %d\n",
							(int)(offset >> SECTOR_SHIFT));
			break;
		}

		if ( block_is_good( oob_buf[OOB_BLOCKSTATUS_OFFSET] ) )
		{
			ret = MTD_READ(mtd, offset, SECTOR_SIZE, &retlen, sect_buf);
			if ( ret < 0 || retlen != SECTOR_SIZE )
			{
				DEBUG(MTD_DEBUG_LEVEL0, "SSFDC_RO: can't read CIS/IDI sector\n");
			}
			else
			if ( !memcmp(sect_buf, cis_numbers, sizeof(cis_numbers)) )	//CIS pattern matching on the sector buffer
			{
				cis_sector = (int)(offset >> SECTOR_SHIFT);		//Found
			}
			else
			{
				DEBUG(MTD_DEBUG_LEVEL1, "SSFDC_RO: CIS/IDI sector not found on %s (mtd%d)\n",
									mtd->name, mtd->index);
			}
			break;
		}
	}

	return cis_sector;
}

//Read physical sector (just a wrapper to MTD_READ)
static int read_physical_sector(struct mtd_info *mtd, unsigned char *sect_buf, int sect_no)
{
	int ret;
	size_t retlen;
	loff_t offset = (loff_t)sect_no << SECTOR_SHIFT;

	ret = MTD_READ(mtd, offset, SECTOR_SIZE, &retlen, sect_buf);
	if ( ret < 0 || retlen != SECTOR_SIZE )
		return -1;

	return 0;
}

//Parity calculator on a word of n bit size
static int get_parity(int number, int size)
{
 	int k;
	int parity;

	parity = 1;
	for (k = 0; k < size; k++)
	{
		parity += (number >> k);
		parity &= 1;
	}
	return parity;
}

//Read and validate the logical block address field stored in the OOB
static int get_logical_address(unsigned char oob_buf[OOB_SIZE])
{
	int block_address, parity;
	int offset[2] = {6, 11};	//offset of the two address fields within OOB
	int j;
	int ok = 0;

	//First we check for good block
	if ( block_is_bad(oob_buf[OOB_BLOCKSTATUS_OFFSET]) )
	{
		DEBUG(MTD_DEBUG_LEVEL0, "SSFDC_RO: get_logical_address() Bad block\n");
		return -1;		//Bad block
	}

	//Look for the first valid logical address
	//Valid address has fixed pattern on most significant bits and parity check
	for (j = 0; j < ArraySize(offset); j++)
	{
		block_address = ((int)oob_buf[offset[j]] << 8) | oob_buf[offset[j]+1];

		//Check for the signature bits in the address field (most significant bits)
		if( (block_address & ~0x7FF) == 0x1000 )
		{
			parity = block_address & 0x01;
			block_address &= 0x7FF;
			block_address >>= 1;

			if( get_parity(block_address, 10) != parity )
			{
				DEBUG(MTD_DEBUG_LEVEL0, "SSFDC_RO: logical address field%d parity error (0x%04X)\n", j+1, block_address);
			}
			else
			{
				ok = 1;
				break;
			}
		}
	}

	if ( !ok )
		block_address = -2;

	DEBUG(MTD_DEBUG_LEVEL3, "SSFDC_RO: get_logical_address() %d\n", block_address);

	return block_address;
}

//Build the logic block map
static int build_logical_block_map(struct ssfdcr_record *ssfdc)
{
	unsigned long offset;
	unsigned char oob_buf[OOB_SIZE];
	int ret, block_address, phys_block;
	size_t retlen;

	DEBUG(MTD_DEBUG_LEVEL1, "SSFDC_RO: build_block_map() n.blocks = %d (%luK)\n",
						ssfdc->map_len, (unsigned long)ssfdc->map_len * ssfdc->erase_size / 1024 );

	//Scan every physical block, skip CIS block
	for (phys_block = ssfdc->cis_block + 1; phys_block < ssfdc->map_len; phys_block++)
	{
		offset = (unsigned long)phys_block * ssfdc->erase_size;
		ret = MTD_READOOB(ssfdc->mbd.mtd, offset, OOB_SIZE, &retlen, oob_buf);
		if ( ret < 0 || retlen != OOB_SIZE )
		{
			DEBUG(MTD_DEBUG_LEVEL0, "SSFDC_RO: mtd read_oob() failed at %lu\n", offset);
			return -1;
		}
		block_address = get_logical_address(oob_buf);

		//Skip bad blocks and invalid addresses
		if ( block_address >= 0 && block_address < MAX_LOGIC_BLK_PER_ZONE )
		{
			int zone_index;

			zone_index = phys_block / MAX_PHYS_BLK_PER_ZONE;
			block_address += zone_index * MAX_LOGIC_BLK_PER_ZONE;
			ssfdc->logic_block_map[block_address] = (unsigned short)phys_block;

			DEBUG(MTD_DEBUG_LEVEL2, "SSFDC_RO: build_block_map() phys_block=%d, logic_block_addr=%d, zone=%d\n",
									phys_block, block_address, zone_index);
		}
	}
	return 0;
}

static void ssfdcr_add_mtd(struct mtd_blktrans_ops *tr, struct mtd_info *mtd)
{
	struct ssfdcr_record *ssfdc;
	int cis_sector;

	//Check for NAND flash
	if (mtd->type != MTD_NANDFLASH)
		return;

	//Check for SSDFC format by reading CIS/IDI sector
	cis_sector = get_valid_cis_sector(mtd);
	if ( cis_sector == -1 )
		return;

	ssfdc = kmalloc(sizeof(struct ssfdcr_record), GFP_KERNEL);
	if ( !ssfdc )
	{
		printk(KERN_WARNING "SSFDC_RO: out of memory for data structures\n");
		return;
	}
	memset(ssfdc, 0, sizeof(*ssfdc));
	
	ssfdc->mbd.mtd = mtd;
	ssfdc->mbd.devnum = -1;
	ssfdc->mbd.blksize = SECTOR_SIZE;
	ssfdc->mbd.tr = tr;
	ssfdc->mbd.readonly = 1;

	ssfdc->cis_block = cis_sector / (mtd->erasesize >> SECTOR_SHIFT);
	ssfdc->erase_size = mtd->erasesize;
	ssfdc->map_len = mtd->size / mtd->erasesize;

	DEBUG(MTD_DEBUG_LEVEL1, "SSFDC_RO: cis_block=%d, erase_size=%d, map_len=%d, n_zones=%d\n",
						ssfdc->cis_block, ssfdc->erase_size, ssfdc->map_len,
						(ssfdc->map_len + MAX_PHYS_BLK_PER_ZONE - 1) / MAX_PHYS_BLK_PER_ZONE);

#ifdef ENABLE_GETGEO
	// Set geometry
	get_chs( mtd->size, NULL, &ssfdc->heads, &ssfdc->sectors);
	ssfdc->cylinders = (unsigned short)((mtd->size >> SECTOR_SHIFT) /
						((long)ssfdc->sectors * (long)ssfdc->heads));

	DEBUG(MTD_DEBUG_LEVEL1, "SSFDC_RO: using C:%d H:%d S:%d == %ld sects\n",
					ssfdc->cylinders, ssfdc->heads , ssfdc->sectors, 
					(long)ssfdc->cylinders * (long)ssfdc->heads *
					(long)ssfdc->sectors );

	ssfdc->mbd.size = (long)ssfdc->heads * (long)ssfdc->cylinders * (long)ssfdc->sectors;
#else
	ssfdc->mbd.size  = ssfdc->map_len * (ssfdc->erase_size >> SECTOR_SHIFT);
#endif

	//Allocate logical block map
	ssfdc->logic_block_map = kmalloc( sizeof(ssfdc->logic_block_map[0]) * ssfdc->map_len, GFP_KERNEL);
	if (!ssfdc->logic_block_map)
	{
		printk(KERN_WARNING "SSFDC_RO: out of memory for data structures\n");
		kfree(ssfdc);
		return;
	}
	memset(ssfdc->logic_block_map, 0xff, sizeof(ssfdc->logic_block_map[0]) * ssfdc->map_len);

	//Build logical block map
	if( build_logical_block_map(ssfdc) < 0 )
	{
		if ( ssfdc->logic_block_map )
			kfree(ssfdc->logic_block_map);
		kfree(ssfdc);
		return;
	}

	//Register device + partitions
	if (add_mtd_blktrans_dev(&ssfdc->mbd))
	{
		if ( ssfdc->logic_block_map )
			kfree(ssfdc->logic_block_map);
		kfree(ssfdc);
		return;
	}

	printk(KERN_INFO "SSFDC_RO: Found ssfdc%c on mtd%d (%s)\n",
					ssfdc->mbd.devnum + 'a', mtd->index, mtd->name);
}

static void ssfdcr_remove_dev(struct mtd_blktrans_dev *dev)
{
	struct ssfdcr_record *ssfdc = (struct ssfdcr_record *)dev;

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

	del_mtd_blktrans_dev(dev);
	if (ssfdc->logic_block_map)
		kfree(ssfdc->logic_block_map);
	kfree(ssfdc);
}

static int ssfdcr_readsect(struct mtd_blktrans_dev *dev, unsigned long logic_sect_no, char *buf)
{
	struct ssfdcr_record *ssfdc = (struct ssfdcr_record *)dev;
	int sectors_per_block, offset, block_address;

	sectors_per_block = ssfdc->erase_size >> SECTOR_SHIFT;
	offset = (int)(logic_sect_no % sectors_per_block);
	block_address = (int)(logic_sect_no / sectors_per_block);

	DEBUG(MTD_DEBUG_LEVEL3, "SSFDC_RO: ssfdcr_readsect(%lu) sec_per_blk=%d, ofst=%d, block_addr=%d\n",
						logic_sect_no, sectors_per_block, offset, block_address);

	if ( block_address >= ssfdc->map_len )
		BUG();

	block_address = ssfdc->logic_block_map[block_address];

	DEBUG(MTD_DEBUG_LEVEL3, "SSFDC_RO: ssfdcr_readsect() phys_block_addr=%d\n", block_address);

	if ( block_address < 0xffff )
	{
		unsigned long sect_no;

		sect_no = (unsigned long)block_address * sectors_per_block + offset;

		DEBUG(MTD_DEBUG_LEVEL3, "SSFDC_RO: ssfdcr_readsect() phys_sect_no=%lu\n", sect_no);

		if ( read_physical_sector( ssfdc->mbd.mtd, buf, sect_no ) < 0 )
			return -EIO;
	}
	else
	{
		memset(buf, 0xff, SECTOR_SIZE);
	}

	return 0;
}

#ifdef ENABLE_GETGEO
static int ssfdcr_getgeo(struct mtd_blktrans_dev *dev,  struct hd_geometry *geo)
{
	struct ssfdcr_record *ssfdc = (struct ssfdcr_record *)dev;

	DEBUG(MTD_DEBUG_LEVEL1, "SSFDC_RO: ssfdcr_getgeo() C=%d, H=%d, S=%d\n",
						ssfdc->cylinders, ssfdc->heads, ssfdc->sectors);

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

	return 0;
}
#endif

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

static struct mtd_blktrans_ops ssfdcr_tr = {
	.name		= "ssfdc",
	.major		= SSFDCR_MAJOR,
	.part_bits	= SSFDCR_PARTN_BITS,
#ifdef ENABLE_GETGEO
	.getgeo		= ssfdcr_getgeo,
#endif
	.readsect	= ssfdcr_readsect,
	.add_mtd	= ssfdcr_add_mtd,
	.remove_dev	= ssfdcr_remove_dev,
	.owner		= THIS_MODULE,
};

static int __init init_ssfdcr(void)
{
	printk(KERN_INFO "SSFDC Read only Flash Translation layer $Revision: 1.5 $\n");

	return register_mtd_blktrans(&ssfdcr_tr);
}

static void __exit cleanup_ssfdcr(void)
{
	deregister_mtd_blktrans(&ssfdcr_tr);
}

module_init(init_ssfdcr);
module_exit(cleanup_ssfdcr);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Claudio Lanconelli <lanconelli.claudio@eptar.com>");
MODULE_DESCRIPTION("Flash Translation Layer for read-only SSDFC SmartMedia card");