// SPDX-License-Identifier: GPL-2.0-only
/*
 * Linux driver for SSFDC Flash Translation Layer (Read only)
 * © 2005 Eptar srl
 * Author: Claudio Lanconelli <lanconelli.claudio@eptar.com>
 *
 * Based on NTFL and MTDBLOCK_RO drivers
 */

#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/rawnand.h>
#include <linux/mtd/blktrans.h>

struct ssfdcr_record {
        struct mtd_blktrans_dev mbd;
        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 )

/** CHS Table
                1MiB    2MiB    4MiB    8MiB    16MiB   32MiB   64MiB   128MiB
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
**/

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_is_nand(mtd) || 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_obj(*ssfdc);
        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_array(ssfdc->map_len,
                              sizeof(ssfdc->logic_block_map[0]), GFP_KERNEL);
        if (!ssfdc->logic_block_map)
                goto out_free_ssfdc;
        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);
out_free_ssfdc:
        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);

        BUG_ON(block_address >= ssfdc->map_len);

        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 <lanconelli.claudio@eptar.com>");
MODULE_DESCRIPTION("Flash Translation Layer for read-only SSFDC SmartMedia card");