Re: FAT vs jFFS2 for NAND.

Claudio Lanconelli
2006-06-20T11:41:03Z

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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 --]
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/*
* 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");