// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright © 2009 - Maxim Levitsky
 * SmartMedia/xD translation layer
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/random.h>
#include <linux/hdreg.h>
#include <linux/kthread.h>
#include <linux/freezer.h>
#include <linux/sysfs.h>
#include <linux/bitops.h>
#include <linux/slab.h>
#include <linux/mtd/nand-ecc-sw-hamming.h>
#include "nand/raw/sm_common.h"
#include "sm_ftl.h"



static struct workqueue_struct *cache_flush_workqueue;

static int cache_timeout = 1000;
module_param(cache_timeout, int, S_IRUGO);
MODULE_PARM_DESC(cache_timeout,
        "Timeout (in ms) for cache flush (1000 ms default");

static int debug;
module_param(debug, int, S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(debug, "Debug level (0-2)");


/* ------------------- sysfs attributes ---------------------------------- */
struct sm_sysfs_attribute {
        struct device_attribute dev_attr;
        char *data;
        int len;
};

static ssize_t sm_attr_show(struct device *dev, struct device_attribute *attr,
                     char *buf)
{
        struct sm_sysfs_attribute *sm_attr =
                container_of(attr, struct sm_sysfs_attribute, dev_attr);

        return sysfs_emit(buf, "%.*s", sm_attr->len, sm_attr->data);
}


#define NUM_ATTRIBUTES 1
#define SM_CIS_VENDOR_OFFSET 0x59
static struct attribute_group *sm_create_sysfs_attributes(struct sm_ftl *ftl)
{
        struct attribute_group *attr_group;
        struct attribute **attributes;
        struct sm_sysfs_attribute *vendor_attribute;
        char *vendor;

        vendor = kstrndup(ftl->cis_buffer + SM_CIS_VENDOR_OFFSET,
                          SM_SMALL_PAGE - SM_CIS_VENDOR_OFFSET, GFP_KERNEL);
        if (!vendor)
                goto error1;

        /* Initialize sysfs attributes */
        vendor_attribute =
                kzalloc_obj(struct sm_sysfs_attribute);
        if (!vendor_attribute)
                goto error2;

        sysfs_attr_init(&vendor_attribute->dev_attr.attr);

        vendor_attribute->data = vendor;
        vendor_attribute->len = strlen(vendor);
        vendor_attribute->dev_attr.attr.name = "vendor";
        vendor_attribute->dev_attr.attr.mode = S_IRUGO;
        vendor_attribute->dev_attr.show = sm_attr_show;


        /* Create array of pointers to the attributes */
        attributes = kzalloc_objs(struct attribute *, NUM_ATTRIBUTES + 1);
        if (!attributes)
                goto error3;
        attributes[0] = &vendor_attribute->dev_attr.attr;

        /* Finally create the attribute group */
        attr_group = kzalloc_obj(struct attribute_group);
        if (!attr_group)
                goto error4;
        attr_group->attrs = attributes;
        return attr_group;
error4:
        kfree(attributes);
error3:
        kfree(vendor_attribute);
error2:
        kfree(vendor);
error1:
        return NULL;
}

static void sm_delete_sysfs_attributes(struct sm_ftl *ftl)
{
        struct attribute **attributes = ftl->disk_attributes->attrs;
        int i;

        for (i = 0; attributes[i] ; i++) {

                struct device_attribute *dev_attr = container_of(attributes[i],
                        struct device_attribute, attr);

                struct sm_sysfs_attribute *sm_attr =
                        container_of(dev_attr,
                                struct sm_sysfs_attribute, dev_attr);

                kfree(sm_attr->data);
                kfree(sm_attr);
        }

        kfree(ftl->disk_attributes->attrs);
        kfree(ftl->disk_attributes);
}


/* ----------------------- oob helpers -------------------------------------- */

static int sm_get_lba(uint8_t *lba)
{
        /* check fixed bits */
        if ((lba[0] & 0xF8) != 0x10)
                return -2;

        /* check parity - endianness doesn't matter */
        if (hweight16(*(uint16_t *)lba) & 1)
                return -2;

        return (lba[1] >> 1) | ((lba[0] & 0x07) << 7);
}


/*
 * Read LBA associated with block
 * returns -1, if block is erased
 * returns -2 if error happens
 */
static int sm_read_lba(struct sm_oob *oob)
{
        static const uint32_t erased_pattern[4] = {
                0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF };

        uint16_t lba_test;
        int lba;

        /* First test for erased block */
        if (!memcmp(oob, erased_pattern, SM_OOB_SIZE))
                return -1;

        /* Now check if both copies of the LBA differ too much */
        lba_test = *(uint16_t *)oob->lba_copy1 ^ *(uint16_t*)oob->lba_copy2;
        if (lba_test && !is_power_of_2(lba_test))
                return -2;

        /* And read it */
        lba = sm_get_lba(oob->lba_copy1);

        if (lba == -2)
                lba = sm_get_lba(oob->lba_copy2);

        return lba;
}

static void sm_write_lba(struct sm_oob *oob, uint16_t lba)
{
        uint8_t tmp[2];

        WARN_ON(lba >= 1000);

        tmp[0] = 0x10 | ((lba >> 7) & 0x07);
        tmp[1] = (lba << 1) & 0xFF;

        if (hweight16(*(uint16_t *)tmp) & 0x01)
                tmp[1] |= 1;

        oob->lba_copy1[0] = oob->lba_copy2[0] = tmp[0];
        oob->lba_copy1[1] = oob->lba_copy2[1] = tmp[1];
}


/* Make offset from parts */
static loff_t sm_mkoffset(struct sm_ftl *ftl, int zone, int block, int boffset)
{
        WARN_ON(boffset & (SM_SECTOR_SIZE - 1));
        WARN_ON(zone < 0 || zone >= ftl->zone_count);
        WARN_ON(block >= ftl->zone_size);
        WARN_ON(boffset >= ftl->block_size);

        if (block == -1)
                return -1;

        return (zone * SM_MAX_ZONE_SIZE + block) * ftl->block_size + boffset;
}

/* Breaks offset into parts */
static void sm_break_offset(struct sm_ftl *ftl, loff_t loffset,
                            int *zone, int *block, int *boffset)
{
        u64 offset = loffset;
        *boffset = do_div(offset, ftl->block_size);
        *block = do_div(offset, ftl->max_lba);
        *zone = offset >= ftl->zone_count ? -1 : offset;
}

/* ---------------------- low level IO ------------------------------------- */

static int sm_correct_sector(uint8_t *buffer, struct sm_oob *oob)
{
        bool sm_order = IS_ENABLED(CONFIG_MTD_NAND_ECC_SW_HAMMING_SMC);
        uint8_t ecc[3];

        ecc_sw_hamming_calculate(buffer, SM_SMALL_PAGE, ecc, sm_order);
        if (ecc_sw_hamming_correct(buffer, ecc, oob->ecc1, SM_SMALL_PAGE,
                                   sm_order) < 0)
                return -EIO;

        buffer += SM_SMALL_PAGE;

        ecc_sw_hamming_calculate(buffer, SM_SMALL_PAGE, ecc, sm_order);
        if (ecc_sw_hamming_correct(buffer, ecc, oob->ecc2, SM_SMALL_PAGE,
                                   sm_order) < 0)
                return -EIO;
        return 0;
}

/* Reads a sector + oob*/
static int sm_read_sector(struct sm_ftl *ftl,
                          int zone, int block, int boffset,
                          uint8_t *buffer, struct sm_oob *oob)
{
        struct mtd_info *mtd = ftl->trans->mtd;
        struct mtd_oob_ops ops = { };
        struct sm_oob tmp_oob;
        int ret = -EIO;
        int try = 0;

        /* FTL can contain -1 entries that are by default filled with bits */
        if (block == -1) {
                if (buffer)
                        memset(buffer, 0xFF, SM_SECTOR_SIZE);
                return 0;
        }

        /* User might not need the oob, but we do for data verification */
        if (!oob)
                oob = &tmp_oob;

        ops.mode = ftl->smallpagenand ? MTD_OPS_RAW : MTD_OPS_PLACE_OOB;
        ops.ooboffs = 0;
        ops.ooblen = SM_OOB_SIZE;
        ops.oobbuf = (void *)oob;
        ops.len = SM_SECTOR_SIZE;
        ops.datbuf = buffer;

again:
        if (try++) {
                /* Avoid infinite recursion on CIS reads, sm_recheck_media
                 * won't help anyway
                 */
                if (zone == 0 && block == ftl->cis_block && boffset ==
                        ftl->cis_boffset)
                        return ret;

                /* Test if media is stable */
                if (try == 3 || sm_recheck_media(ftl))
                        return ret;
        }

        /* Unfortunately, oob read will _always_ succeed,
         * despite card removal.....
         */
        ret = mtd_read_oob(mtd, sm_mkoffset(ftl, zone, block, boffset), &ops);

        /* Test for unknown errors */
        if (ret != 0 && !mtd_is_bitflip_or_eccerr(ret)) {
                dbg("read of block %d at zone %d, failed due to error (%d)",
                        block, zone, ret);
                goto again;
        }

        /* Do a basic test on the oob, to guard against returned garbage */
        if (oob->reserved != 0xFFFFFFFF && !is_power_of_2(~oob->reserved))
                goto again;

        /* This should never happen, unless there is a bug in the mtd driver */
        WARN_ON(ops.oobretlen != SM_OOB_SIZE);
        WARN_ON(buffer && ops.retlen != SM_SECTOR_SIZE);

        if (!buffer)
                return 0;

        /* Test if sector marked as bad */
        if (!sm_sector_valid(oob)) {
                dbg("read of block %d at zone %d, failed because it is marked"
                        " as bad" , block, zone);
                goto again;
        }

        /* Test ECC*/
        if (mtd_is_eccerr(ret) ||
                (ftl->smallpagenand && sm_correct_sector(buffer, oob))) {

                dbg("read of block %d at zone %d, failed due to ECC error",
                        block, zone);
                goto again;
        }

        return 0;
}

/* Writes a sector to media */
static int sm_write_sector(struct sm_ftl *ftl,
                           int zone, int block, int boffset,
                           uint8_t *buffer, struct sm_oob *oob)
{
        struct mtd_oob_ops ops = { };
        struct mtd_info *mtd = ftl->trans->mtd;
        int ret;

        BUG_ON(ftl->readonly);

        if (zone == 0 && (block == ftl->cis_block || block == 0)) {
                dbg("attempted to write the CIS!");
                return -EIO;
        }

        if (ftl->unstable)
                return -EIO;

        ops.mode = ftl->smallpagenand ? MTD_OPS_RAW : MTD_OPS_PLACE_OOB;
        ops.len = SM_SECTOR_SIZE;
        ops.datbuf = buffer;
        ops.ooboffs = 0;
        ops.ooblen = SM_OOB_SIZE;
        ops.oobbuf = (void *)oob;

        ret = mtd_write_oob(mtd, sm_mkoffset(ftl, zone, block, boffset), &ops);

        /* Now we assume that hardware will catch write bitflip errors */

        if (ret) {
                dbg("write to block %d at zone %d, failed with error %d",
                        block, zone, ret);

                sm_recheck_media(ftl);
                return ret;
        }

        /* This should never happen, unless there is a bug in the driver */
        WARN_ON(ops.oobretlen != SM_OOB_SIZE);
        WARN_ON(buffer && ops.retlen != SM_SECTOR_SIZE);

        return 0;
}

/* ------------------------ block IO ------------------------------------- */

/* Write a block using data and lba, and invalid sector bitmap */
static int sm_write_block(struct sm_ftl *ftl, uint8_t *buf,
                          int zone, int block, int lba,
                          unsigned long invalid_bitmap)
{
        bool sm_order = IS_ENABLED(CONFIG_MTD_NAND_ECC_SW_HAMMING_SMC);
        struct sm_oob oob;
        int boffset;
        int retry = 0;

        /* Initialize the oob with requested values */
        memset(&oob, 0xFF, SM_OOB_SIZE);
        sm_write_lba(&oob, lba);
restart:
        if (ftl->unstable)
                return -EIO;

        for (boffset = 0; boffset < ftl->block_size;
                                boffset += SM_SECTOR_SIZE) {

                oob.data_status = 0xFF;

                if (test_bit(boffset / SM_SECTOR_SIZE, &invalid_bitmap)) {

                        sm_printk("sector %d of block at LBA %d of zone %d"
                                " couldn't be read, marking it as invalid",
                                boffset / SM_SECTOR_SIZE, lba, zone);

                        oob.data_status = 0;
                }

                if (ftl->smallpagenand) {
                        ecc_sw_hamming_calculate(buf + boffset,
                                                 SM_SMALL_PAGE, oob.ecc1,
                                                 sm_order);

                        ecc_sw_hamming_calculate(buf + boffset + SM_SMALL_PAGE,
                                                 SM_SMALL_PAGE, oob.ecc2,
                                                 sm_order);
                }
                if (!sm_write_sector(ftl, zone, block, boffset,
                                                        buf + boffset, &oob))
                        continue;

                if (!retry) {

                        /* If write fails. try to erase the block */
                        /* This is safe, because we never write in blocks
                         * that contain valuable data.
                         * This is intended to repair block that are marked
                         * as erased, but that isn't fully erased
                         */

                        if (sm_erase_block(ftl, zone, block, 0))
                                return -EIO;

                        retry = 1;
                        goto restart;
                } else {
                        sm_mark_block_bad(ftl, zone, block);
                        return -EIO;
                }
        }
        return 0;
}


/* Mark whole block at offset 'offs' as bad. */
static void sm_mark_block_bad(struct sm_ftl *ftl, int zone, int block)
{
        struct sm_oob oob;
        int boffset;

        memset(&oob, 0xFF, SM_OOB_SIZE);
        oob.block_status = 0xF0;

        if (ftl->unstable)
                return;

        if (sm_recheck_media(ftl))
                return;

        sm_printk("marking block %d of zone %d as bad", block, zone);

        /* We aren't checking the return value, because we don't care */
        /* This also fails on fake xD cards, but I guess these won't expose
         * any bad blocks till fail completely
         */
        for (boffset = 0; boffset < ftl->block_size; boffset += SM_SECTOR_SIZE)
                sm_write_sector(ftl, zone, block, boffset, NULL, &oob);
}

/*
 * Erase a block within a zone
 * If erase succeeds, it updates free block fifo, otherwise marks block as bad
 */
static int sm_erase_block(struct sm_ftl *ftl, int zone_num, uint16_t block,
                          int put_free)
{
        struct ftl_zone *zone = &ftl->zones[zone_num];
        struct mtd_info *mtd = ftl->trans->mtd;
        struct erase_info erase;

        erase.addr = sm_mkoffset(ftl, zone_num, block, 0);
        erase.len = ftl->block_size;

        if (ftl->unstable)
                return -EIO;

        BUG_ON(ftl->readonly);

        if (zone_num == 0 && (block == ftl->cis_block || block == 0)) {
                sm_printk("attempted to erase the CIS!");
                return -EIO;
        }

        if (mtd_erase(mtd, &erase)) {
                sm_printk("erase of block %d in zone %d failed",
                                                        block, zone_num);
                goto error;
        }

        if (put_free)
                kfifo_in(&zone->free_sectors,
                        (const unsigned char *)&block, sizeof(block));

        return 0;
error:
        sm_mark_block_bad(ftl, zone_num, block);
        return -EIO;
}

/* Thoroughly test that block is valid. */
static int sm_check_block(struct sm_ftl *ftl, int zone, int block)
{
        int boffset;
        struct sm_oob oob;
        int lbas[] = { -3, 0, 0, 0 };
        int i = 0;
        int test_lba;


        /* First just check that block doesn't look fishy */
        /* Only blocks that are valid or are sliced in two parts, are
         * accepted
         */
        for (boffset = 0; boffset < ftl->block_size;
                                        boffset += SM_SECTOR_SIZE) {

                /* This shouldn't happen anyway */
                if (sm_read_sector(ftl, zone, block, boffset, NULL, &oob))
                        return -2;

                test_lba = sm_read_lba(&oob);

                if (lbas[i] != test_lba)
                        lbas[++i] = test_lba;

                /* If we found three different LBAs, something is fishy */
                if (i == 3)
                        return -EIO;
        }

        /* If the block is sliced (partially erased usually) erase it */
        if (i == 2) {
                sm_erase_block(ftl, zone, block, 1);
                return 1;
        }

        return 0;
}

/* ----------------- media scanning --------------------------------- */
static const struct chs_entry chs_table[] = {
        { 1,    125,  4,  4  },
        { 2,    125,  4,  8  },
        { 4,    250,  4,  8  },
        { 8,    250,  4,  16 },
        { 16,   500,  4,  16 },
        { 32,   500,  8,  16 },
        { 64,   500,  8,  32 },
        { 128,  500,  16, 32 },
        { 256,  1000, 16, 32 },
        { 512,  1015, 32, 63 },
        { 1024, 985,  33, 63 },
        { 2048, 985,  33, 63 },
        { 0 },
};


static const uint8_t cis_signature[] = {
        0x01, 0x03, 0xD9, 0x01, 0xFF, 0x18, 0x02, 0xDF, 0x01, 0x20
};
/* Find out media parameters.
 * This ideally has to be based on nand id, but for now device size is enough
 */
static int sm_get_media_info(struct sm_ftl *ftl, struct mtd_info *mtd)
{
        int i;
        int size_in_megs = mtd->size / (1024 * 1024);

        ftl->readonly = mtd->type == MTD_ROM;

        /* Manual settings for very old devices */
        ftl->zone_count = 1;
        ftl->smallpagenand = 0;

        switch (size_in_megs) {
        case 1:
                /* 1 MiB flash/rom SmartMedia card (256 byte pages)*/
                ftl->zone_size = 256;
                ftl->max_lba = 250;
                ftl->block_size = 8 * SM_SECTOR_SIZE;
                ftl->smallpagenand = 1;

                break;
        case 2:
                /* 2 MiB flash SmartMedia (256 byte pages)*/
                if (mtd->writesize == SM_SMALL_PAGE) {
                        ftl->zone_size = 512;
                        ftl->max_lba = 500;
                        ftl->block_size = 8 * SM_SECTOR_SIZE;
                        ftl->smallpagenand = 1;
                /* 2 MiB rom SmartMedia */
                } else {

                        if (!ftl->readonly)
                                return -ENODEV;

                        ftl->zone_size = 256;
                        ftl->max_lba = 250;
                        ftl->block_size = 16 * SM_SECTOR_SIZE;
                }
                break;
        case 4:
                /* 4 MiB flash/rom SmartMedia device */
                ftl->zone_size = 512;
                ftl->max_lba = 500;
                ftl->block_size = 16 * SM_SECTOR_SIZE;
                break;
        case 8:
                /* 8 MiB flash/rom SmartMedia device */
                ftl->zone_size = 1024;
                ftl->max_lba = 1000;
                ftl->block_size = 16 * SM_SECTOR_SIZE;
        }

        /* Minimum xD size is 16MiB. Also, all xD cards have standard zone
         * sizes. SmartMedia cards exist up to 128 MiB and have same layout
         */
        if (size_in_megs >= 16) {
                ftl->zone_count = size_in_megs / 16;
                ftl->zone_size = 1024;
                ftl->max_lba = 1000;
                ftl->block_size = 32 * SM_SECTOR_SIZE;
        }

        /* Test for proper write,erase and oob sizes */
        if (mtd->erasesize > ftl->block_size)
                return -ENODEV;

        if (mtd->writesize > SM_SECTOR_SIZE)
                return -ENODEV;

        if (ftl->smallpagenand && mtd->oobsize < SM_SMALL_OOB_SIZE)
                return -ENODEV;

        if (!ftl->smallpagenand && mtd->oobsize < SM_OOB_SIZE)
                return -ENODEV;

        /* We use OOB */
        if (!mtd_has_oob(mtd))
                return -ENODEV;

        /* Find geometry information */
        for (i = 0 ; i < ARRAY_SIZE(chs_table) ; i++) {
                if (chs_table[i].size == size_in_megs) {
                        ftl->cylinders = chs_table[i].cyl;
                        ftl->heads = chs_table[i].head;
                        ftl->sectors = chs_table[i].sec;
                        return 0;
                }
        }

        sm_printk("media has unknown size : %dMiB", size_in_megs);
        ftl->cylinders = 985;
        ftl->heads =  33;
        ftl->sectors = 63;
        return 0;
}

/* Validate the CIS */
static int sm_read_cis(struct sm_ftl *ftl)
{
        struct sm_oob oob;

        if (sm_read_sector(ftl,
                0, ftl->cis_block, ftl->cis_boffset, ftl->cis_buffer, &oob))
                        return -EIO;

        if (!sm_sector_valid(&oob) || !sm_block_valid(&oob))
                return -EIO;

        if (!memcmp(ftl->cis_buffer + ftl->cis_page_offset,
                        cis_signature, sizeof(cis_signature))) {
                return 0;
        }

        return -EIO;
}

/* Scan the media for the CIS */
static int sm_find_cis(struct sm_ftl *ftl)
{
        struct sm_oob oob;
        int block, boffset;
        int block_found = 0;
        int cis_found = 0;

        /* Search for first valid block */
        for (block = 0 ; block < ftl->zone_size - ftl->max_lba ; block++) {

                if (sm_read_sector(ftl, 0, block, 0, NULL, &oob))
                        continue;

                if (!sm_block_valid(&oob))
                        continue;
                block_found = 1;
                break;
        }

        if (!block_found)
                return -EIO;

        /* Search for first valid sector in this block */
        for (boffset = 0 ; boffset < ftl->block_size;
                                                boffset += SM_SECTOR_SIZE) {

                if (sm_read_sector(ftl, 0, block, boffset, NULL, &oob))
                        continue;

                if (!sm_sector_valid(&oob))
                        continue;
                break;
        }

        if (boffset == ftl->block_size)
                return -EIO;

        ftl->cis_block = block;
        ftl->cis_boffset = boffset;
        ftl->cis_page_offset = 0;

        cis_found = !sm_read_cis(ftl);

        if (!cis_found) {
                ftl->cis_page_offset = SM_SMALL_PAGE;
                cis_found = !sm_read_cis(ftl);
        }

        if (cis_found) {
                dbg("CIS block found at offset %x",
                        block * ftl->block_size +
                                boffset + ftl->cis_page_offset);
                return 0;
        }
        return -EIO;
}

/* Basic test to determine if underlying mtd device if functional */
static int sm_recheck_media(struct sm_ftl *ftl)
{
        if (sm_read_cis(ftl)) {

                if (!ftl->unstable) {
                        sm_printk("media unstable, not allowing writes");
                        ftl->unstable = 1;
                }
                return -EIO;
        }
        return 0;
}

/* Initialize a FTL zone */
static int sm_init_zone(struct sm_ftl *ftl, int zone_num)
{
        struct ftl_zone *zone = &ftl->zones[zone_num];
        struct sm_oob oob;
        uint16_t block;
        int lba;
        int i = 0;
        int len;

        dbg("initializing zone %d", zone_num);

        /* Allocate memory for FTL table */
        zone->lba_to_phys_table = kmalloc_array(ftl->max_lba, 2, GFP_KERNEL);

        if (!zone->lba_to_phys_table)
                return -ENOMEM;
        memset(zone->lba_to_phys_table, -1, ftl->max_lba * 2);


        /* Allocate memory for free sectors FIFO */
        if (kfifo_alloc(&zone->free_sectors, ftl->zone_size * 2, GFP_KERNEL)) {
                kfree(zone->lba_to_phys_table);
                return -ENOMEM;
        }

        /* Now scan the zone */
        for (block = 0 ; block < ftl->zone_size ; block++) {

                /* Skip blocks till the CIS (including) */
                if (zone_num == 0 && block <= ftl->cis_block)
                        continue;

                /* Read the oob of first sector */
                if (sm_read_sector(ftl, zone_num, block, 0, NULL, &oob)) {
                        kfifo_free(&zone->free_sectors);
                        kfree(zone->lba_to_phys_table);
                        return -EIO;
                }

                /* Test to see if block is erased. It is enough to test
                 * first sector, because erase happens in one shot
                 */
                if (sm_block_erased(&oob)) {
                        kfifo_in(&zone->free_sectors,
                                (unsigned char *)&block, 2);
                        continue;
                }

                /* If block is marked as bad, skip it */
                /* This assumes we can trust first sector*/
                /* However the way the block valid status is defined, ensures
                 * very low probability of failure here
                 */
                if (!sm_block_valid(&oob)) {
                        dbg("PH %04d <-> <marked bad>", block);
                        continue;
                }


                lba = sm_read_lba(&oob);

                /* Invalid LBA means that block is damaged. */
                /* We can try to erase it, or mark it as bad, but
                 * lets leave that to recovery application
                 */
                if (lba == -2 || lba >= ftl->max_lba) {
                        dbg("PH %04d <-> LBA %04d(bad)", block, lba);
                        continue;
                }


                /* If there is no collision,
                 * just put the sector in the FTL table
                 */
                if (zone->lba_to_phys_table[lba] < 0) {
                        dbg_verbose("PH %04d <-> LBA %04d", block, lba);
                        zone->lba_to_phys_table[lba] = block;
                        continue;
                }

                sm_printk("collision"
                        " of LBA %d between blocks %d and %d in zone %d",
                        lba, zone->lba_to_phys_table[lba], block, zone_num);

                /* Test that this block is valid*/
                if (sm_check_block(ftl, zone_num, block))
                        continue;

                /* Test now the old block */
                if (sm_check_block(ftl, zone_num,
                                        zone->lba_to_phys_table[lba])) {
                        zone->lba_to_phys_table[lba] = block;
                        continue;
                }

                /* If both blocks are valid and share same LBA, it means that
                 * they hold different versions of same data. It not
                 * known which is more recent, thus just erase one of them
                 */
                sm_printk("both blocks are valid, erasing the later");
                sm_erase_block(ftl, zone_num, block, 1);
        }

        dbg("zone initialized");
        zone->initialized = 1;

        /* No free sectors, means that the zone is heavily damaged, write won't
         * work, but it can still can be (partially) read
         */
        if (!kfifo_len(&zone->free_sectors)) {
                sm_printk("no free blocks in zone %d", zone_num);
                return 0;
        }

        /* Randomize first block we write to */
        get_random_bytes(&i, 2);
        i %= (kfifo_len(&zone->free_sectors) / 2);

        while (i--) {
                len = kfifo_out(&zone->free_sectors,
                                        (unsigned char *)&block, 2);
                WARN_ON(len != 2);
                kfifo_in(&zone->free_sectors, (const unsigned char *)&block, 2);
        }
        return 0;
}

/* Get and automatically initialize an FTL mapping for one zone */
static struct ftl_zone *sm_get_zone(struct sm_ftl *ftl, int zone_num)
{
        struct ftl_zone *zone;
        int error;

        BUG_ON(zone_num >= ftl->zone_count);
        zone = &ftl->zones[zone_num];

        if (!zone->initialized) {
                error = sm_init_zone(ftl, zone_num);

                if (error)
                        return ERR_PTR(error);
        }
        return zone;
}


/* ----------------- cache handling ------------------------------------------*/

/* Initialize the one block cache */
static void sm_cache_init(struct sm_ftl *ftl)
{
        ftl->cache_data_invalid_bitmap = 0xFFFFFFFF;
        ftl->cache_clean = 1;
        ftl->cache_zone = -1;
        ftl->cache_block = -1;
        /*memset(ftl->cache_data, 0xAA, ftl->block_size);*/
}

/* Put sector in one block cache */
static void sm_cache_put(struct sm_ftl *ftl, char *buffer, int boffset)
{
        memcpy(ftl->cache_data + boffset, buffer, SM_SECTOR_SIZE);
        clear_bit(boffset / SM_SECTOR_SIZE, &ftl->cache_data_invalid_bitmap);
        ftl->cache_clean = 0;
}

/* Read a sector from the cache */
static int sm_cache_get(struct sm_ftl *ftl, char *buffer, int boffset)
{
        if (test_bit(boffset / SM_SECTOR_SIZE,
                &ftl->cache_data_invalid_bitmap))
                        return -1;

        memcpy(buffer, ftl->cache_data + boffset, SM_SECTOR_SIZE);
        return 0;
}

/* Write the cache to hardware */
static int sm_cache_flush(struct sm_ftl *ftl)
{
        struct ftl_zone *zone;

        int sector_num;
        uint16_t write_sector;
        int zone_num = ftl->cache_zone;
        int block_num;

        if (ftl->cache_clean)
                return 0;

        if (ftl->unstable)
                return -EIO;

        BUG_ON(zone_num < 0);
        zone = &ftl->zones[zone_num];
        block_num = zone->lba_to_phys_table[ftl->cache_block];


        /* Try to read all unread areas of the cache block*/
        for_each_set_bit(sector_num, &ftl->cache_data_invalid_bitmap,
                ftl->block_size / SM_SECTOR_SIZE) {

                if (!sm_read_sector(ftl,
                        zone_num, block_num, sector_num * SM_SECTOR_SIZE,
                        ftl->cache_data + sector_num * SM_SECTOR_SIZE, NULL))
                                clear_bit(sector_num,
                                        &ftl->cache_data_invalid_bitmap);
        }
restart:

        if (ftl->unstable)
                return -EIO;

        /* If there are no spare blocks, */
        /* we could still continue by erasing/writing the current block,
         * but for such worn out media it doesn't worth the trouble,
         * and the dangers
         */
        if (kfifo_out(&zone->free_sectors,
                                (unsigned char *)&write_sector, 2) != 2) {
                dbg("no free sectors for write!");
                return -EIO;
        }


        if (sm_write_block(ftl, ftl->cache_data, zone_num, write_sector,
                ftl->cache_block, ftl->cache_data_invalid_bitmap))
                        goto restart;

        /* Update the FTL table */
        zone->lba_to_phys_table[ftl->cache_block] = write_sector;

        /* Write successful, so erase and free the old block */
        if (block_num > 0)
                sm_erase_block(ftl, zone_num, block_num, 1);

        sm_cache_init(ftl);
        return 0;
}


/* flush timer, runs a second after last write */
static void sm_cache_flush_timer(struct timer_list *t)
{
        struct sm_ftl *ftl = timer_container_of(ftl, t, timer);
        queue_work(cache_flush_workqueue, &ftl->flush_work);
}

/* cache flush work, kicked by timer */
static void sm_cache_flush_work(struct work_struct *work)
{
        struct sm_ftl *ftl = container_of(work, struct sm_ftl, flush_work);
        mutex_lock(&ftl->mutex);
        sm_cache_flush(ftl);
        mutex_unlock(&ftl->mutex);
        return;
}

/* ---------------- outside interface -------------------------------------- */

/* outside interface: read a sector */
static int sm_read(struct mtd_blktrans_dev *dev,
                   unsigned long sect_no, char *buf)
{
        struct sm_ftl *ftl = dev->priv;
        struct ftl_zone *zone;
        int error = 0, in_cache = 0;
        int zone_num, block, boffset;

        sm_break_offset(ftl, sect_no << 9, &zone_num, &block, &boffset);
        mutex_lock(&ftl->mutex);


        zone = sm_get_zone(ftl, zone_num);
        if (IS_ERR(zone)) {
                error = PTR_ERR(zone);
                goto unlock;
        }

        /* Have to look at cache first */
        if (ftl->cache_zone == zone_num && ftl->cache_block == block) {
                in_cache = 1;
                if (!sm_cache_get(ftl, buf, boffset))
                        goto unlock;
        }

        /* Translate the block and return if doesn't exist in the table */
        block = zone->lba_to_phys_table[block];

        if (block == -1) {
                memset(buf, 0xFF, SM_SECTOR_SIZE);
                goto unlock;
        }

        if (sm_read_sector(ftl, zone_num, block, boffset, buf, NULL)) {
                error = -EIO;
                goto unlock;
        }

        if (in_cache)
                sm_cache_put(ftl, buf, boffset);
unlock:
        mutex_unlock(&ftl->mutex);
        return error;
}

/* outside interface: write a sector */
static int sm_write(struct mtd_blktrans_dev *dev,
                                unsigned long sec_no, char *buf)
{
        struct sm_ftl *ftl = dev->priv;
        struct ftl_zone *zone;
        int error = 0, zone_num, block, boffset;

        BUG_ON(ftl->readonly);
        sm_break_offset(ftl, sec_no << 9, &zone_num, &block, &boffset);

        /* No need in flush thread running now */
        timer_delete(&ftl->timer);
        mutex_lock(&ftl->mutex);

        zone = sm_get_zone(ftl, zone_num);
        if (IS_ERR(zone)) {
                error = PTR_ERR(zone);
                goto unlock;
        }

        /* If entry is not in cache, flush it */
        if (ftl->cache_block != block || ftl->cache_zone != zone_num) {

                error = sm_cache_flush(ftl);
                if (error)
                        goto unlock;

                ftl->cache_block = block;
                ftl->cache_zone = zone_num;
        }

        sm_cache_put(ftl, buf, boffset);
unlock:
        mod_timer(&ftl->timer, jiffies + msecs_to_jiffies(cache_timeout));
        mutex_unlock(&ftl->mutex);
        return error;
}

/* outside interface: flush everything */
static int sm_flush(struct mtd_blktrans_dev *dev)
{
        struct sm_ftl *ftl = dev->priv;
        int retval;

        mutex_lock(&ftl->mutex);
        retval =  sm_cache_flush(ftl);
        mutex_unlock(&ftl->mutex);
        return retval;
}

/* outside interface: device is released */
static void sm_release(struct mtd_blktrans_dev *dev)
{
        struct sm_ftl *ftl = dev->priv;

        timer_delete_sync(&ftl->timer);
        cancel_work_sync(&ftl->flush_work);
        mutex_lock(&ftl->mutex);
        sm_cache_flush(ftl);
        mutex_unlock(&ftl->mutex);
}

/* outside interface: get geometry */
static int sm_getgeo(struct mtd_blktrans_dev *dev, struct hd_geometry *geo)
{
        struct sm_ftl *ftl = dev->priv;
        geo->heads = ftl->heads;
        geo->sectors = ftl->sectors;
        geo->cylinders = ftl->cylinders;
        return 0;
}

/* external interface: main initialization function */
static void sm_add_mtd(struct mtd_blktrans_ops *tr, struct mtd_info *mtd)
{
        struct mtd_blktrans_dev *trans;
        struct sm_ftl *ftl;

        /* Allocate & initialize our private structure */
        ftl = kzalloc_obj(struct sm_ftl);
        if (!ftl)
                goto error1;


        mutex_init(&ftl->mutex);
        timer_setup(&ftl->timer, sm_cache_flush_timer, 0);
        INIT_WORK(&ftl->flush_work, sm_cache_flush_work);

        /* Read media information */
        if (sm_get_media_info(ftl, mtd)) {
                dbg("found unsupported mtd device, aborting");
                goto error2;
        }


        /* Allocate temporary CIS buffer for read retry support */
        ftl->cis_buffer = kzalloc(SM_SECTOR_SIZE, GFP_KERNEL);
        if (!ftl->cis_buffer)
                goto error2;

        /* Allocate zone array, it will be initialized on demand */
        ftl->zones = kzalloc_objs(struct ftl_zone, ftl->zone_count);
        if (!ftl->zones)
                goto error3;

        /* Allocate the cache*/
        ftl->cache_data = kzalloc(ftl->block_size, GFP_KERNEL);

        if (!ftl->cache_data)
                goto error4;

        sm_cache_init(ftl);


        /* Allocate upper layer structure and initialize it */
        trans = kzalloc_obj(struct mtd_blktrans_dev);
        if (!trans)
                goto error5;

        ftl->trans = trans;
        trans->priv = ftl;

        trans->tr = tr;
        trans->mtd = mtd;
        trans->devnum = -1;
        trans->size = (ftl->block_size * ftl->max_lba * ftl->zone_count) >> 9;
        trans->readonly = ftl->readonly;

        if (sm_find_cis(ftl)) {
                dbg("CIS not found on mtd device, aborting");
                goto error6;
        }

        ftl->disk_attributes = sm_create_sysfs_attributes(ftl);
        if (!ftl->disk_attributes)
                goto error6;
        trans->disk_attributes = ftl->disk_attributes;

        sm_printk("Found %d MiB xD/SmartMedia FTL on mtd%d",
                (int)(mtd->size / (1024 * 1024)), mtd->index);

        dbg("FTL layout:");
        dbg("%d zone(s), each consists of %d blocks (+%d spares)",
                ftl->zone_count, ftl->max_lba,
                ftl->zone_size - ftl->max_lba);
        dbg("each block consists of %d bytes",
                ftl->block_size);


        /* Register device*/
        if (add_mtd_blktrans_dev(trans)) {
                dbg("error in mtdblktrans layer");
                goto error6;
        }
        return;
error6:
        kfree(trans);
error5:
        kfree(ftl->cache_data);
error4:
        kfree(ftl->zones);
error3:
        kfree(ftl->cis_buffer);
error2:
        kfree(ftl);
error1:
        return;
}

/* main interface: device {surprise,} removal */
static void sm_remove_dev(struct mtd_blktrans_dev *dev)
{
        struct sm_ftl *ftl = dev->priv;
        int i;

        del_mtd_blktrans_dev(dev);
        ftl->trans = NULL;

        for (i = 0 ; i < ftl->zone_count; i++) {

                if (!ftl->zones[i].initialized)
                        continue;

                kfree(ftl->zones[i].lba_to_phys_table);
                kfifo_free(&ftl->zones[i].free_sectors);
        }

        sm_delete_sysfs_attributes(ftl);
        kfree(ftl->cis_buffer);
        kfree(ftl->zones);
        kfree(ftl->cache_data);
        kfree(ftl);
}

static struct mtd_blktrans_ops sm_ftl_ops = {
        .name           = "smblk",
        .major          = 0,
        .part_bits      = SM_FTL_PARTN_BITS,
        .blksize        = SM_SECTOR_SIZE,
        .getgeo         = sm_getgeo,

        .add_mtd        = sm_add_mtd,
        .remove_dev     = sm_remove_dev,

        .readsect       = sm_read,
        .writesect      = sm_write,

        .flush          = sm_flush,
        .release        = sm_release,

        .owner          = THIS_MODULE,
};

static __init int sm_module_init(void)
{
        int error = 0;

        cache_flush_workqueue = create_freezable_workqueue("smflush");
        if (!cache_flush_workqueue)
                return -ENOMEM;

        error = register_mtd_blktrans(&sm_ftl_ops);
        if (error)
                destroy_workqueue(cache_flush_workqueue);
        return error;

}

static void __exit sm_module_exit(void)
{
        destroy_workqueue(cache_flush_workqueue);
        deregister_mtd_blktrans(&sm_ftl_ops);
}

module_init(sm_module_init);
module_exit(sm_module_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Maxim Levitsky <maximlevitsky@gmail.com>");
MODULE_DESCRIPTION("Smartmedia/xD mtd translation layer");