ssfdc.c

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/*
 * Linux driver for SSFDC Flash Translation Layer (Read only)
 * © 2005 Eptar srl
 * Author: Claudio Lanconelli <[email protected]>
 *
 * 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.
 */

#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>

struct ssfdcr_record {
    struct mtd_blktrans_dev mbd;
    int usecount;
    unsigned char heads;
    unsigned char sectors;
    unsigned short cylinders;
    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 128MiB) */
    int map_len;            /* n. phys_blocks on the card */
};

#define SSFDCR_MAJOR        257
#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 KiB(x)  ( (x) * 1024L )
#define MiB(x)  ( KiB(x) * 1024L )

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[] = {
    { MiB(  1), 125,  4,  4 },
    { MiB(  2), 125,  4,  8 },
    { MiB(  4), 250,  4,  8 },
    { MiB(  8), 250,  4, 16 },
    { MiB( 16), 500,  4, 16 },
    { MiB( 32), 500,  8, 16 },
    { MiB( 64), 500,  8, 32 },
    { MiB(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;
}

/* These bytes are the signature for the CIS/IDI sector */
static const uint8_t cis_numbers[] = {
    0x01, 0x03, 0xD9, 0x01, 0xFF, 0x18, 0x02, 0xDF, 0x01, 0x20
};

/* 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;
    uint8_t *sect_buf;

    cis_sector = -1;

    sect_buf = kmalloc(SECTOR_SIZE, GFP_KERNEL);
    if (!sect_buf)
        goto out;

    /*
     * 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
     */
    for (k = 0, offset = 0; k < 4; k++, offset += mtd->erasesize) {
        if (mtd_block_isbad(mtd, offset)) {
            ret = mtd_read(mtd, offset, SECTOR_SIZE, &retlen,
                       sect_buf);

            /* CIS pattern match on the sector buffer */
            if (ret < 0 || retlen != SECTOR_SIZE) {
                printk(KERN_WARNING
                    "SSFDC_RO:can't read CIS/IDI sector\n");
            } else if (!memcmp(sect_buf, cis_numbers,
                    sizeof(cis_numbers))) {
                /* Found */
                cis_sector = (int)(offset >> SECTOR_SHIFT);
            } else {
                pr_debug("SSFDC_RO: CIS/IDI sector not found"
                    " on %s (mtd%d)\n", mtd->name,
                    mtd->index);
            }
            break;
        }
    }

    kfree(sect_buf);
 out:
    return cis_sector;
}

/* Read physical sector (wrapper to MTD_READ) */
static int read_physical_sector(struct mtd_info *mtd, uint8_t *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;
}

/* Read redundancy area (wrapper to MTD_READ_OOB */
static int read_raw_oob(struct mtd_info *mtd, loff_t offs, uint8_t *buf)
{
    struct mtd_oob_ops ops;
    int ret;

    ops.mode = MTD_OPS_RAW;
    ops.ooboffs = 0;
    ops.ooblen = OOB_SIZE;
    ops.oobbuf = buf;
    ops.datbuf = NULL;

    ret = mtd_read_oob(mtd, offs, &ops);
    if (ret < 0 || ops.oobretlen != OOB_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(uint8_t *oob_buf)
{
    int block_address, parity;
    int offset[2] = {6, 11}; /* offset of the 2 address fields within OOB */
    int j;
    int ok = 0;

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

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

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

    if (!ok)
        block_address = -2;

    pr_debug("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;
    uint8_t oob_buf[OOB_SIZE];
    int ret, block_address, phys_block;
    struct mtd_info *mtd = ssfdc->mbd.mtd;

    pr_debug("SSFDC_RO: build_block_map() nblks=%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;
        if (mtd_block_isbad(mtd, offset))
            continue;   /* skip bad blocks */

        ret = read_raw_oob(mtd, offset, oob_buf);
        if (ret < 0) {
            pr_debug("SSFDC_RO: mtd read_oob() failed at %lu\n",
                offset);
            return -1;
        }
        block_address = get_logical_address(oob_buf);

        /* Skip 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;

            pr_debug("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 small page NAND flash */
    if (mtd->type != MTD_NANDFLASH || mtd->oobsize != OOB_SIZE ||
        mtd->size > UINT_MAX)
        return;

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

    ssfdc = kzalloc(sizeof(struct ssfdcr_record), GFP_KERNEL);
    if (!ssfdc)
        return;

    ssfdc->mbd.mtd = mtd;
    ssfdc->mbd.devnum = -1;
    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 = (u32)mtd->size / mtd->erasesize;

    pr_debug("SSFDC_RO: cis_block=%d,erase_size=%d,map_len=%d,n_zones=%d\n",
        ssfdc->cis_block, ssfdc->erase_size, ssfdc->map_len,
        DIV_ROUND_UP(ssfdc->map_len, MAX_PHYS_BLK_PER_ZONE));

    /* Set geometry */
    ssfdc->heads = 16;
    ssfdc->sectors = 32;
    get_chs(mtd->size, NULL, &ssfdc->heads, &ssfdc->sectors);
    ssfdc->cylinders = (unsigned short)(((u32)mtd->size >> SECTOR_SHIFT) /
            ((long)ssfdc->sectors * (long)ssfdc->heads));

    pr_debug("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;

    /* 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)
        goto out_err;
    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)
        goto out_err;

    /* Register device + partitions */
    if (add_mtd_blktrans_dev(&ssfdc->mbd))
        goto out_err;

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

out_err:
    kfree(ssfdc->logic_block_map);
        kfree(ssfdc);
}

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

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

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

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);

    pr_debug("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];

    pr_debug("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;

        pr_debug("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;
}

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

    pr_debug("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;
}

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

static struct mtd_blktrans_ops ssfdcr_tr = {
    .name       = "ssfdc",
    .major      = SSFDCR_MAJOR,
    .part_bits  = SSFDCR_PARTN_BITS,
    .blksize    = SECTOR_SIZE,
    .getgeo     = ssfdcr_getgeo,
    .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\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 <[email protected]>");
MODULE_DESCRIPTION("Flash Translation Layer for read-only SSFDC SmartMedia card");