// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Copyright © 1999-2010 David Woodhouse <dwmw2@infradead.org>
 */

#include <linux/device.h>
#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/err.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/sched.h>
#include <linux/mutex.h>
#include <linux/backing-dev.h>
#include <linux/compat.h>
#include <linux/mount.h>
#include <linux/blkpg.h>
#include <linux/magic.h>
#include <linux/major.h>
#include <linux/mtd/mtd.h>
#include <linux/mtd/partitions.h>
#include <linux/mtd/map.h>

#include <linux/uaccess.h>

#include "mtdcore.h"

/*
 * Data structure to hold the pointer to the mtd device as well
 * as mode information of various use cases.
 */
struct mtd_file_info {
        struct mtd_info *mtd;
        enum mtd_file_modes mode;
};

static loff_t mtdchar_lseek(struct file *file, loff_t offset, int orig)
{
        struct mtd_file_info *mfi = file->private_data;
        return fixed_size_llseek(file, offset, orig, mfi->mtd->size);
}

static int mtdchar_open(struct inode *inode, struct file *file)
{
        int minor = iminor(inode);
        int devnum = minor >> 1;
        int ret = 0;
        struct mtd_info *mtd;
        struct mtd_file_info *mfi;

        pr_debug("MTD_open\n");

        /* You can't open the RO devices RW */
        if ((file->f_mode & FMODE_WRITE) && (minor & 1))
                return -EACCES;

        mtd = get_mtd_device(NULL, devnum);

        if (IS_ERR(mtd))
                return PTR_ERR(mtd);

        if (mtd->type == MTD_ABSENT) {
                ret = -ENODEV;
                goto out1;
        }

        /* You can't open it RW if it's not a writeable device */
        if ((file->f_mode & FMODE_WRITE) && !(mtd->flags & MTD_WRITEABLE)) {
                ret = -EACCES;
                goto out1;
        }

        mfi = kzalloc_obj(*mfi);
        if (!mfi) {
                ret = -ENOMEM;
                goto out1;
        }
        mfi->mtd = mtd;
        file->private_data = mfi;
        return 0;

out1:
        put_mtd_device(mtd);
        return ret;
} /* mtdchar_open */

/*====================================================================*/

static int mtdchar_close(struct inode *inode, struct file *file)
{
        struct mtd_file_info *mfi = file->private_data;
        struct mtd_info *mtd = mfi->mtd;

        pr_debug("MTD_close\n");

        /* Only sync if opened RW */
        if ((file->f_mode & FMODE_WRITE))
                mtd_sync(mtd);

        put_mtd_device(mtd);
        file->private_data = NULL;
        kfree(mfi);

        return 0;
} /* mtdchar_close */

/* Back in June 2001, dwmw2 wrote:
 *
 *   FIXME: This _really_ needs to die. In 2.5, we should lock the
 *   userspace buffer down and use it directly with readv/writev.
 *
 * The implementation below, using mtd_kmalloc_up_to, mitigates
 * allocation failures when the system is under low-memory situations
 * or if memory is highly fragmented at the cost of reducing the
 * performance of the requested transfer due to a smaller buffer size.
 *
 * A more complex but more memory-efficient implementation based on
 * get_user_pages and iovecs to cover extents of those pages is a
 * longer-term goal, as intimated by dwmw2 above. However, for the
 * write case, this requires yet more complex head and tail transfer
 * handling when those head and tail offsets and sizes are such that
 * alignment requirements are not met in the NAND subdriver.
 */

static ssize_t mtdchar_read(struct file *file, char __user *buf, size_t count,
                        loff_t *ppos)
{
        struct mtd_file_info *mfi = file->private_data;
        struct mtd_info *mtd = mfi->mtd;
        size_t retlen;
        size_t total_retlen=0;
        int ret=0;
        int len;
        size_t size = count;
        char *kbuf;

        pr_debug("MTD_read\n");

        if (*ppos + count > mtd->size) {
                if (*ppos < mtd->size)
                        count = mtd->size - *ppos;
                else
                        count = 0;
        }

        if (!count)
                return 0;

        kbuf = mtd_kmalloc_up_to(mtd, &size);
        if (!kbuf)
                return -ENOMEM;

        while (count) {
                len = min_t(size_t, count, size);

                switch (mfi->mode) {
                case MTD_FILE_MODE_OTP_FACTORY:
                        ret = mtd_read_fact_prot_reg(mtd, *ppos, len,
                                                     &retlen, kbuf);
                        break;
                case MTD_FILE_MODE_OTP_USER:
                        ret = mtd_read_user_prot_reg(mtd, *ppos, len,
                                                     &retlen, kbuf);
                        break;
                case MTD_FILE_MODE_RAW:
                {
                        struct mtd_oob_ops ops = {};

                        ops.mode = MTD_OPS_RAW;
                        ops.datbuf = kbuf;
                        ops.oobbuf = NULL;
                        ops.len = len;

                        ret = mtd_read_oob(mtd, *ppos, &ops);
                        retlen = ops.retlen;
                        break;
                }
                default:
                        ret = mtd_read(mtd, *ppos, len, &retlen, kbuf);
                }
                /* Nand returns -EBADMSG on ECC errors, but it returns
                 * the data. For our userspace tools it is important
                 * to dump areas with ECC errors!
                 * For kernel internal usage it also might return -EUCLEAN
                 * to signal the caller that a bitflip has occurred and has
                 * been corrected by the ECC algorithm.
                 * Userspace software which accesses NAND this way
                 * must be aware of the fact that it deals with NAND
                 */
                if (!ret || mtd_is_bitflip_or_eccerr(ret)) {
                        *ppos += retlen;
                        if (copy_to_user(buf, kbuf, retlen)) {
                                kfree(kbuf);
                                return -EFAULT;
                        }
                        else
                                total_retlen += retlen;

                        count -= retlen;
                        buf += retlen;
                        if (retlen == 0)
                                count = 0;
                }
                else {
                        kfree(kbuf);
                        return ret;
                }

        }

        kfree(kbuf);
        return total_retlen;
} /* mtdchar_read */

static ssize_t mtdchar_write(struct file *file, const char __user *buf, size_t count,
                        loff_t *ppos)
{
        struct mtd_file_info *mfi = file->private_data;
        struct mtd_info *mtd = mfi->mtd;
        size_t size = count;
        char *kbuf;
        size_t retlen;
        size_t total_retlen=0;
        int ret=0;
        int len;

        pr_debug("MTD_write\n");

        if (*ppos >= mtd->size)
                return -ENOSPC;

        if (*ppos + count > mtd->size)
                count = mtd->size - *ppos;

        if (!count)
                return 0;

        kbuf = mtd_kmalloc_up_to(mtd, &size);
        if (!kbuf)
                return -ENOMEM;

        while (count) {
                len = min_t(size_t, count, size);

                if (copy_from_user(kbuf, buf, len)) {
                        kfree(kbuf);
                        return -EFAULT;
                }

                switch (mfi->mode) {
                case MTD_FILE_MODE_OTP_FACTORY:
                        ret = -EROFS;
                        break;
                case MTD_FILE_MODE_OTP_USER:
                        ret = mtd_write_user_prot_reg(mtd, *ppos, len,
                                                      &retlen, kbuf);
                        break;

                case MTD_FILE_MODE_RAW:
                {
                        struct mtd_oob_ops ops = {};

                        ops.mode = MTD_OPS_RAW;
                        ops.datbuf = kbuf;
                        ops.oobbuf = NULL;
                        ops.ooboffs = 0;
                        ops.len = len;

                        ret = mtd_write_oob(mtd, *ppos, &ops);
                        retlen = ops.retlen;
                        break;
                }

                default:
                        ret = mtd_write(mtd, *ppos, len, &retlen, kbuf);
                }

                /*
                 * Return -ENOSPC only if no data could be written at all.
                 * Otherwise just return the number of bytes that actually
                 * have been written.
                 */
                if ((ret == -ENOSPC) && (total_retlen))
                        break;

                if (!ret) {
                        *ppos += retlen;
                        total_retlen += retlen;
                        count -= retlen;
                        buf += retlen;
                }
                else {
                        kfree(kbuf);
                        return ret;
                }
        }

        kfree(kbuf);
        return total_retlen;
} /* mtdchar_write */

/*======================================================================

    IOCTL calls for getting device parameters.

======================================================================*/

static int otp_select_filemode(struct mtd_file_info *mfi, int mode)
{
        struct mtd_info *mtd = mfi->mtd;
        size_t retlen;

        switch (mode) {
        case MTD_OTP_FACTORY:
                if (mtd_read_fact_prot_reg(mtd, -1, 0, &retlen, NULL) ==
                                -EOPNOTSUPP)
                        return -EOPNOTSUPP;

                mfi->mode = MTD_FILE_MODE_OTP_FACTORY;
                break;
        case MTD_OTP_USER:
                if (mtd_read_user_prot_reg(mtd, -1, 0, &retlen, NULL) ==
                                -EOPNOTSUPP)
                        return -EOPNOTSUPP;

                mfi->mode = MTD_FILE_MODE_OTP_USER;
                break;
        case MTD_OTP_OFF:
                mfi->mode = MTD_FILE_MODE_NORMAL;
                break;
        default:
                return -EINVAL;
        }

        return 0;
}

static int mtdchar_writeoob(struct file *file, struct mtd_info *mtd,
        uint64_t start, uint32_t length, void __user *ptr,
        uint32_t __user *retp)
{
        struct mtd_info *master  = mtd_get_master(mtd);
        struct mtd_file_info *mfi = file->private_data;
        struct mtd_oob_ops ops = {};
        uint32_t retlen;
        int ret = 0;

        if (length > 4096)
                return -EINVAL;

        if (!master->_write_oob)
                return -EOPNOTSUPP;

        ops.ooblen = length;
        ops.ooboffs = start & (mtd->writesize - 1);
        ops.datbuf = NULL;
        ops.mode = (mfi->mode == MTD_FILE_MODE_RAW) ? MTD_OPS_RAW :
                MTD_OPS_PLACE_OOB;

        if (ops.ooboffs && ops.ooblen > (mtd->oobsize - ops.ooboffs))
                return -EINVAL;

        ops.oobbuf = memdup_user(ptr, length);
        if (IS_ERR(ops.oobbuf))
                return PTR_ERR(ops.oobbuf);

        start &= ~((uint64_t)mtd->writesize - 1);
        ret = mtd_write_oob(mtd, start, &ops);

        if (ops.oobretlen > 0xFFFFFFFFU)
                ret = -EOVERFLOW;
        retlen = ops.oobretlen;
        if (copy_to_user(retp, &retlen, sizeof(length)))
                ret = -EFAULT;

        kfree(ops.oobbuf);
        return ret;
}

static int mtdchar_readoob(struct file *file, struct mtd_info *mtd,
        uint64_t start, uint32_t length, void __user *ptr,
        uint32_t __user *retp)
{
        struct mtd_file_info *mfi = file->private_data;
        struct mtd_oob_ops ops = {};
        int ret = 0;

        if (length > 4096)
                return -EINVAL;

        ops.ooblen = length;
        ops.ooboffs = start & (mtd->writesize - 1);
        ops.datbuf = NULL;
        ops.mode = (mfi->mode == MTD_FILE_MODE_RAW) ? MTD_OPS_RAW :
                MTD_OPS_PLACE_OOB;

        if (ops.ooboffs && ops.ooblen > (mtd->oobsize - ops.ooboffs))
                return -EINVAL;

        ops.oobbuf = kmalloc(length, GFP_KERNEL);
        if (!ops.oobbuf)
                return -ENOMEM;

        start &= ~((uint64_t)mtd->writesize - 1);
        ret = mtd_read_oob(mtd, start, &ops);

        if (put_user(ops.oobretlen, retp))
                ret = -EFAULT;
        else if (ops.oobretlen && copy_to_user(ptr, ops.oobbuf,
                                            ops.oobretlen))
                ret = -EFAULT;

        kfree(ops.oobbuf);

        /*
         * NAND returns -EBADMSG on ECC errors, but it returns the OOB
         * data. For our userspace tools it is important to dump areas
         * with ECC errors!
         * For kernel internal usage it also might return -EUCLEAN
         * to signal the caller that a bitflip has occurred and has
         * been corrected by the ECC algorithm.
         *
         * Note: currently the standard NAND function, nand_read_oob_std,
         * does not calculate ECC for the OOB area, so do not rely on
         * this behavior unless you have replaced it with your own.
         */
        if (mtd_is_bitflip_or_eccerr(ret))
                return 0;

        return ret;
}

/*
 * Copies (and truncates, if necessary) OOB layout information to the
 * deprecated layout struct, nand_ecclayout_user. This is necessary only to
 * support the deprecated API ioctl ECCGETLAYOUT while allowing all new
 * functionality to use mtd_ooblayout_ops flexibly (i.e. mtd_ooblayout_ops
 * can describe any kind of OOB layout with almost zero overhead from a
 * memory usage point of view).
 */
static int shrink_ecclayout(struct mtd_info *mtd,
                            struct nand_ecclayout_user *to)
{
        struct mtd_oob_region oobregion;
        int i, section = 0, ret;

        if (!mtd || !to)
                return -EINVAL;

        memset(to, 0, sizeof(*to));

        to->eccbytes = 0;
        for (i = 0; i < MTD_MAX_ECCPOS_ENTRIES;) {
                u32 eccpos;

                ret = mtd_ooblayout_ecc(mtd, section++, &oobregion);
                if (ret < 0) {
                        if (ret != -ERANGE)
                                return ret;

                        break;
                }

                eccpos = oobregion.offset;
                for (; i < MTD_MAX_ECCPOS_ENTRIES &&
                       eccpos < oobregion.offset + oobregion.length; i++) {
                        to->eccpos[i] = eccpos++;
                        to->eccbytes++;
                }
        }

        for (i = 0; i < MTD_MAX_OOBFREE_ENTRIES; i++) {
                ret = mtd_ooblayout_free(mtd, i, &oobregion);
                if (ret < 0) {
                        if (ret != -ERANGE)
                                return ret;

                        break;
                }

                to->oobfree[i].offset = oobregion.offset;
                to->oobfree[i].length = oobregion.length;
                to->oobavail += to->oobfree[i].length;
        }

        return 0;
}

static int get_oobinfo(struct mtd_info *mtd, struct nand_oobinfo *to)
{
        struct mtd_oob_region oobregion;
        int i, section = 0, ret;

        if (!mtd || !to)
                return -EINVAL;

        memset(to, 0, sizeof(*to));

        to->eccbytes = 0;
        for (i = 0; i < ARRAY_SIZE(to->eccpos);) {
                u32 eccpos;

                ret = mtd_ooblayout_ecc(mtd, section++, &oobregion);
                if (ret < 0) {
                        if (ret != -ERANGE)
                                return ret;

                        break;
                }

                if (oobregion.length + i > ARRAY_SIZE(to->eccpos))
                        return -EINVAL;

                eccpos = oobregion.offset;
                for (; eccpos < oobregion.offset + oobregion.length; i++) {
                        to->eccpos[i] = eccpos++;
                        to->eccbytes++;
                }
        }

        for (i = 0; i < 8; i++) {
                ret = mtd_ooblayout_free(mtd, i, &oobregion);
                if (ret < 0) {
                        if (ret != -ERANGE)
                                return ret;

                        break;
                }

                to->oobfree[i][0] = oobregion.offset;
                to->oobfree[i][1] = oobregion.length;
        }

        to->useecc = MTD_NANDECC_AUTOPLACE;

        return 0;
}

static int mtdchar_blkpg_ioctl(struct mtd_info *mtd,
                               struct blkpg_ioctl_arg *arg)
{
        struct blkpg_partition p;

        if (!capable(CAP_SYS_ADMIN))
                return -EPERM;

        if (copy_from_user(&p, arg->data, sizeof(p)))
                return -EFAULT;

        switch (arg->op) {
        case BLKPG_ADD_PARTITION:

                /* Only master mtd device must be used to add partitions */
                if (mtd_is_partition(mtd))
                        return -EINVAL;

                /* Sanitize user input */
                p.devname[BLKPG_DEVNAMELTH - 1] = '\0';

                return mtd_add_partition(mtd, p.devname, p.start, p.length);

        case BLKPG_DEL_PARTITION:

                if (p.pno < 0)
                        return -EINVAL;

                return mtd_del_partition(mtd, p.pno);

        default:
                return -EINVAL;
        }
}

static void adjust_oob_length(struct mtd_info *mtd, uint64_t start,
                              struct mtd_oob_ops *ops)
{
        uint32_t start_page, end_page;
        u32 oob_per_page;

        if (ops->len == 0 || ops->ooblen == 0)
                return;

        start_page = mtd_div_by_ws(start, mtd);
        end_page = mtd_div_by_ws(start + ops->len - 1, mtd);
        oob_per_page = mtd_oobavail(mtd, ops);

        ops->ooblen = min_t(size_t, ops->ooblen,
                            (end_page - start_page + 1) * oob_per_page);
}

static noinline_for_stack int
mtdchar_write_ioctl(struct mtd_info *mtd, struct mtd_write_req __user *argp)
{
        struct mtd_info *master = mtd_get_master(mtd);
        struct mtd_write_req req;
        const void __user *usr_data, *usr_oob;
        uint8_t *datbuf = NULL, *oobbuf = NULL;
        size_t datbuf_len, oobbuf_len;
        int ret = 0;
        u64 end;

        if (copy_from_user(&req, argp, sizeof(req)))
                return -EFAULT;

        usr_data = (const void __user *)(uintptr_t)req.usr_data;
        usr_oob = (const void __user *)(uintptr_t)req.usr_oob;

        if (!master->_write_oob)
                return -EOPNOTSUPP;

        if (!usr_data)
                req.len = 0;

        if (!usr_oob)
                req.ooblen = 0;

        req.len &= 0xffffffff;
        req.ooblen &= 0xffffffff;

        if (check_add_overflow(req.start, req.len, &end) || end > mtd->size)
                return -EINVAL;

        datbuf_len = min_t(size_t, req.len, mtd->erasesize);
        if (datbuf_len > 0) {
                datbuf = kvmalloc(datbuf_len, GFP_KERNEL);
                if (!datbuf)
                        return -ENOMEM;
        }

        oobbuf_len = min_t(size_t, req.ooblen, mtd->erasesize);
        if (oobbuf_len > 0) {
                oobbuf = kvmalloc(oobbuf_len, GFP_KERNEL);
                if (!oobbuf) {
                        kvfree(datbuf);
                        return -ENOMEM;
                }
        }

        while (req.len > 0 || (!usr_data && req.ooblen > 0)) {
                struct mtd_oob_ops ops = {
                        .mode = req.mode,
                        .len = min_t(size_t, req.len, datbuf_len),
                        .ooblen = min_t(size_t, req.ooblen, oobbuf_len),
                        .datbuf = datbuf,
                        .oobbuf = oobbuf,
                };

                /*
                 * Shorten non-page-aligned, eraseblock-sized writes so that
                 * the write ends on an eraseblock boundary.  This is necessary
                 * for adjust_oob_length() to properly handle non-page-aligned
                 * writes.
                 */
                if (ops.len == mtd->erasesize)
                        ops.len -= mtd_mod_by_ws(req.start + ops.len, mtd);

                /*
                 * For writes which are not OOB-only, adjust the amount of OOB
                 * data written according to the number of data pages written.
                 * This is necessary to prevent OOB data from being skipped
                 * over in data+OOB writes requiring multiple mtd_write_oob()
                 * calls to be completed.
                 */
                adjust_oob_length(mtd, req.start, &ops);

                if (copy_from_user(datbuf, usr_data, ops.len) ||
                    copy_from_user(oobbuf, usr_oob, ops.ooblen)) {
                        ret = -EFAULT;
                        break;
                }

                ret = mtd_write_oob(mtd, req.start, &ops);
                if (ret)
                        break;

                req.start += ops.retlen;
                req.len -= ops.retlen;
                usr_data += ops.retlen;

                req.ooblen -= ops.oobretlen;
                usr_oob += ops.oobretlen;
        }

        kvfree(datbuf);
        kvfree(oobbuf);

        return ret;
}

static noinline_for_stack int
mtdchar_read_ioctl(struct mtd_info *mtd, struct mtd_read_req __user *argp)
{
        struct mtd_info *master = mtd_get_master(mtd);
        struct mtd_read_req req;
        void __user *usr_data, *usr_oob;
        uint8_t *datbuf = NULL, *oobbuf = NULL;
        size_t datbuf_len, oobbuf_len;
        size_t orig_len, orig_ooblen;
        int ret = 0;
        u64 end;

        if (copy_from_user(&req, argp, sizeof(req)))
                return -EFAULT;

        orig_len = req.len;
        orig_ooblen = req.ooblen;

        usr_data = (void __user *)(uintptr_t)req.usr_data;
        usr_oob = (void __user *)(uintptr_t)req.usr_oob;

        if (!master->_read_oob)
                return -EOPNOTSUPP;

        if (!usr_data)
                req.len = 0;

        if (!usr_oob)
                req.ooblen = 0;

        req.ecc_stats.uncorrectable_errors = 0;
        req.ecc_stats.corrected_bitflips = 0;
        req.ecc_stats.max_bitflips = 0;

        req.len &= 0xffffffff;
        req.ooblen &= 0xffffffff;

        if (check_add_overflow(req.start, req.len, &end) || end > mtd->size) {
                ret = -EINVAL;
                goto out;
        }

        datbuf_len = min_t(size_t, req.len, mtd->erasesize);
        if (datbuf_len > 0) {
                datbuf = kvmalloc(datbuf_len, GFP_KERNEL);
                if (!datbuf) {
                        ret = -ENOMEM;
                        goto out;
                }
        }

        oobbuf_len = min_t(size_t, req.ooblen, mtd->erasesize);
        if (oobbuf_len > 0) {
                oobbuf = kvmalloc(oobbuf_len, GFP_KERNEL);
                if (!oobbuf) {
                        ret = -ENOMEM;
                        goto out;
                }
        }

        while (req.len > 0 || (!usr_data && req.ooblen > 0)) {
                struct mtd_req_stats stats;
                struct mtd_oob_ops ops = {
                        .mode = req.mode,
                        .len = min_t(size_t, req.len, datbuf_len),
                        .ooblen = min_t(size_t, req.ooblen, oobbuf_len),
                        .datbuf = datbuf,
                        .oobbuf = oobbuf,
                        .stats = &stats,
                };

                /*
                 * Shorten non-page-aligned, eraseblock-sized reads so that the
                 * read ends on an eraseblock boundary.  This is necessary in
                 * order to prevent OOB data for some pages from being
                 * duplicated in the output of non-page-aligned reads requiring
                 * multiple mtd_read_oob() calls to be completed.
                 */
                if (ops.len == mtd->erasesize)
                        ops.len -= mtd_mod_by_ws(req.start + ops.len, mtd);

                ret = mtd_read_oob(mtd, (loff_t)req.start, &ops);

                req.ecc_stats.uncorrectable_errors +=
                        stats.uncorrectable_errors;
                req.ecc_stats.corrected_bitflips += stats.corrected_bitflips;
                req.ecc_stats.max_bitflips =
                        max(req.ecc_stats.max_bitflips, stats.max_bitflips);

                if (ret && !mtd_is_bitflip_or_eccerr(ret))
                        break;

                if (copy_to_user(usr_data, ops.datbuf, ops.retlen) ||
                    copy_to_user(usr_oob, ops.oobbuf, ops.oobretlen)) {
                        ret = -EFAULT;
                        break;
                }

                req.start += ops.retlen;
                req.len -= ops.retlen;
                usr_data += ops.retlen;

                req.ooblen -= ops.oobretlen;
                usr_oob += ops.oobretlen;
        }

        /*
         * As multiple iterations of the above loop (and therefore multiple
         * mtd_read_oob() calls) may be necessary to complete the read request,
         * adjust the final return code to ensure it accounts for all detected
         * ECC errors.
         */
        if (!ret || mtd_is_bitflip(ret)) {
                if (req.ecc_stats.uncorrectable_errors > 0)
                        ret = -EBADMSG;
                else if (req.ecc_stats.corrected_bitflips > 0)
                        ret = -EUCLEAN;
        }

out:
        req.len = orig_len - req.len;
        req.ooblen = orig_ooblen - req.ooblen;

        if (copy_to_user(argp, &req, sizeof(req)))
                ret = -EFAULT;

        kvfree(datbuf);
        kvfree(oobbuf);

        return ret;
}

static int mtdchar_ioctl(struct file *file, u_int cmd, u_long arg)
{
        struct mtd_file_info *mfi = file->private_data;
        struct mtd_info *mtd = mfi->mtd;
        struct mtd_info *master = mtd_get_master(mtd);
        void __user *argp = (void __user *)arg;
        int ret = 0;
        struct mtd_info_user info;

        pr_debug("MTD_ioctl\n");

        /*
         * Check the file mode to require "dangerous" commands to have write
         * permissions.
         */
        switch (cmd) {
        /* "safe" commands */
        case MEMGETREGIONCOUNT:
        case MEMGETREGIONINFO:
        case MEMGETINFO:
        case MEMREADOOB:
        case MEMREADOOB64:
        case MEMREAD:
        case MEMISLOCKED:
        case MEMGETOOBSEL:
        case MEMGETBADBLOCK:
        case OTPSELECT:
        case OTPGETREGIONCOUNT:
        case OTPGETREGIONINFO:
        case ECCGETLAYOUT:
        case ECCGETSTATS:
        case MTDFILEMODE:
        case BLKPG:
        case BLKRRPART:
                break;

        /* "dangerous" commands */
        case MEMERASE:
        case MEMERASE64:
        case MEMLOCK:
        case MEMUNLOCK:
        case MEMSETBADBLOCK:
        case MEMWRITEOOB:
        case MEMWRITEOOB64:
        case MEMWRITE:
        case OTPLOCK:
        case OTPERASE:
                if (!(file->f_mode & FMODE_WRITE))
                        return -EPERM;
                break;

        default:
                return -ENOTTY;
        }

        switch (cmd) {
        case MEMGETREGIONCOUNT:
                if (copy_to_user(argp, &(mtd->numeraseregions), sizeof(int)))
                        return -EFAULT;
                break;

        case MEMGETREGIONINFO:
        {
                uint32_t ur_idx;
                struct mtd_erase_region_info *kr;
                struct region_info_user __user *ur = argp;

                if (get_user(ur_idx, &(ur->regionindex)))
                        return -EFAULT;

                if (ur_idx >= mtd->numeraseregions)
                        return -EINVAL;

                kr = &(mtd->eraseregions[ur_idx]);

                if (put_user(kr->offset, &(ur->offset))
                    || put_user(kr->erasesize, &(ur->erasesize))
                    || put_user(kr->numblocks, &(ur->numblocks)))
                        return -EFAULT;

                break;
        }

        case MEMGETINFO:
                memset(&info, 0, sizeof(info));
                info.type       = mtd->type;
                info.flags      = mtd->flags;
                info.size       = mtd->size;
                info.erasesize  = mtd->erasesize;
                info.writesize  = mtd->writesize;
                info.oobsize    = mtd->oobsize;
                /* The below field is obsolete */
                info.padding    = 0;
                if (copy_to_user(argp, &info, sizeof(struct mtd_info_user)))
                        return -EFAULT;
                break;

        case MEMERASE:
        case MEMERASE64:
        {
                struct erase_info *erase;

                erase=kzalloc_obj(struct erase_info);
                if (!erase)
                        ret = -ENOMEM;
                else {
                        if (cmd == MEMERASE64) {
                                struct erase_info_user64 einfo64;

                                if (copy_from_user(&einfo64, argp,
                                            sizeof(struct erase_info_user64))) {
                                        kfree(erase);
                                        return -EFAULT;
                                }
                                erase->addr = einfo64.start;
                                erase->len = einfo64.length;
                        } else {
                                struct erase_info_user einfo32;

                                if (copy_from_user(&einfo32, argp,
                                            sizeof(struct erase_info_user))) {
                                        kfree(erase);
                                        return -EFAULT;
                                }
                                erase->addr = einfo32.start;
                                erase->len = einfo32.length;
                        }

                        ret = mtd_erase(mtd, erase);
                        kfree(erase);
                }
                break;
        }

        case MEMWRITEOOB:
        {
                struct mtd_oob_buf buf;
                struct mtd_oob_buf __user *buf_user = argp;

                /* NOTE: writes return length to buf_user->length */
                if (copy_from_user(&buf, argp, sizeof(buf)))
                        ret = -EFAULT;
                else
                        ret = mtdchar_writeoob(file, mtd, buf.start, buf.length,
                                buf.ptr, &buf_user->length);
                break;
        }

        case MEMREADOOB:
        {
                struct mtd_oob_buf buf;
                struct mtd_oob_buf __user *buf_user = argp;

                /* NOTE: writes return length to buf_user->start */
                if (copy_from_user(&buf, argp, sizeof(buf)))
                        ret = -EFAULT;
                else
                        ret = mtdchar_readoob(file, mtd, buf.start, buf.length,
                                buf.ptr, &buf_user->start);
                break;
        }

        case MEMWRITEOOB64:
        {
                struct mtd_oob_buf64 buf;
                struct mtd_oob_buf64 __user *buf_user = argp;

                if (copy_from_user(&buf, argp, sizeof(buf)))
                        ret = -EFAULT;
                else
                        ret = mtdchar_writeoob(file, mtd, buf.start, buf.length,
                                (void __user *)(uintptr_t)buf.usr_ptr,
                                &buf_user->length);
                break;
        }

        case MEMREADOOB64:
        {
                struct mtd_oob_buf64 buf;
                struct mtd_oob_buf64 __user *buf_user = argp;

                if (copy_from_user(&buf, argp, sizeof(buf)))
                        ret = -EFAULT;
                else
                        ret = mtdchar_readoob(file, mtd, buf.start, buf.length,
                                (void __user *)(uintptr_t)buf.usr_ptr,
                                &buf_user->length);
                break;
        }

        case MEMWRITE:
        {
                ret = mtdchar_write_ioctl(mtd,
                      (struct mtd_write_req __user *)arg);
                break;
        }

        case MEMREAD:
        {
                ret = mtdchar_read_ioctl(mtd,
                      (struct mtd_read_req __user *)arg);
                break;
        }

        case MEMLOCK:
        {
                struct erase_info_user einfo;

                if (copy_from_user(&einfo, argp, sizeof(einfo)))
                        return -EFAULT;

                ret = mtd_lock(mtd, einfo.start, einfo.length);
                break;
        }

        case MEMUNLOCK:
        {
                struct erase_info_user einfo;

                if (copy_from_user(&einfo, argp, sizeof(einfo)))
                        return -EFAULT;

                ret = mtd_unlock(mtd, einfo.start, einfo.length);
                break;
        }

        case MEMISLOCKED:
        {
                struct erase_info_user einfo;

                if (copy_from_user(&einfo, argp, sizeof(einfo)))
                        return -EFAULT;

                ret = mtd_is_locked(mtd, einfo.start, einfo.length);
                break;
        }

        /* Legacy interface */
        case MEMGETOOBSEL:
        {
                struct nand_oobinfo oi;

                if (!master->ooblayout)
                        return -EOPNOTSUPP;

                ret = get_oobinfo(mtd, &oi);
                if (ret)
                        return ret;

                if (copy_to_user(argp, &oi, sizeof(struct nand_oobinfo)))
                        return -EFAULT;
                break;
        }

        case MEMGETBADBLOCK:
        {
                loff_t offs;

                if (copy_from_user(&offs, argp, sizeof(loff_t)))
                        return -EFAULT;
                return mtd_block_isbad(mtd, offs);
        }

        case MEMSETBADBLOCK:
        {
                loff_t offs;

                if (copy_from_user(&offs, argp, sizeof(loff_t)))
                        return -EFAULT;
                return mtd_block_markbad(mtd, offs);
        }

        case OTPSELECT:
        {
                int mode;
                if (copy_from_user(&mode, argp, sizeof(int)))
                        return -EFAULT;

                mfi->mode = MTD_FILE_MODE_NORMAL;

                ret = otp_select_filemode(mfi, mode);

                file->f_pos = 0;
                break;
        }

        case OTPGETREGIONCOUNT:
        case OTPGETREGIONINFO:
        {
                struct otp_info *buf = kmalloc(4096, GFP_KERNEL);
                size_t retlen;
                if (!buf)
                        return -ENOMEM;
                switch (mfi->mode) {
                case MTD_FILE_MODE_OTP_FACTORY:
                        ret = mtd_get_fact_prot_info(mtd, 4096, &retlen, buf);
                        break;
                case MTD_FILE_MODE_OTP_USER:
                        ret = mtd_get_user_prot_info(mtd, 4096, &retlen, buf);
                        break;
                default:
                        ret = -EINVAL;
                        break;
                }
                if (!ret) {
                        if (cmd == OTPGETREGIONCOUNT) {
                                int nbr = retlen / sizeof(struct otp_info);
                                ret = copy_to_user(argp, &nbr, sizeof(int));
                        } else
                                ret = copy_to_user(argp, buf, retlen);
                        if (ret)
                                ret = -EFAULT;
                }
                kfree(buf);
                break;
        }

        case OTPLOCK:
        case OTPERASE:
        {
                struct otp_info oinfo;

                if (mfi->mode != MTD_FILE_MODE_OTP_USER)
                        return -EINVAL;
                if (copy_from_user(&oinfo, argp, sizeof(oinfo)))
                        return -EFAULT;
                if (cmd == OTPLOCK)
                        ret = mtd_lock_user_prot_reg(mtd, oinfo.start, oinfo.length);
                else
                        ret = mtd_erase_user_prot_reg(mtd, oinfo.start, oinfo.length);
                break;
        }

        /* This ioctl is being deprecated - it truncates the ECC layout */
        case ECCGETLAYOUT:
        {
                struct nand_ecclayout_user *usrlay;

                if (!master->ooblayout)
                        return -EOPNOTSUPP;

                usrlay = kmalloc_obj(*usrlay);
                if (!usrlay)
                        return -ENOMEM;

                shrink_ecclayout(mtd, usrlay);

                if (copy_to_user(argp, usrlay, sizeof(*usrlay)))
                        ret = -EFAULT;
                kfree(usrlay);
                break;
        }

        case ECCGETSTATS:
        {
                if (copy_to_user(argp, &mtd->ecc_stats,
                                 sizeof(struct mtd_ecc_stats)))
                        return -EFAULT;
                break;
        }

        case MTDFILEMODE:
        {
                mfi->mode = 0;

                switch(arg) {
                case MTD_FILE_MODE_OTP_FACTORY:
                case MTD_FILE_MODE_OTP_USER:
                        ret = otp_select_filemode(mfi, arg);
                        break;

                case MTD_FILE_MODE_RAW:
                        if (!mtd_has_oob(mtd))
                                return -EOPNOTSUPP;
                        mfi->mode = arg;
                        break;

                case MTD_FILE_MODE_NORMAL:
                        break;
                default:
                        ret = -EINVAL;
                }
                file->f_pos = 0;
                break;
        }

        case BLKPG:
        {
                struct blkpg_ioctl_arg __user *blk_arg = argp;
                struct blkpg_ioctl_arg a;

                if (copy_from_user(&a, blk_arg, sizeof(a)))
                        ret = -EFAULT;
                else
                        ret = mtdchar_blkpg_ioctl(mtd, &a);
                break;
        }

        case BLKRRPART:
        {
                /* No reread partition feature. Just return ok */
                ret = 0;
                break;
        }
        }

        return ret;
} /* memory_ioctl */

static long mtdchar_unlocked_ioctl(struct file *file, u_int cmd, u_long arg)
{
        struct mtd_file_info *mfi = file->private_data;
        struct mtd_info *mtd = mfi->mtd;
        struct mtd_info *master = mtd_get_master(mtd);
        int ret;

        mutex_lock(&master->master.chrdev_lock);
        ret = mtdchar_ioctl(file, cmd, arg);
        mutex_unlock(&master->master.chrdev_lock);

        return ret;
}

#ifdef CONFIG_COMPAT

struct mtd_oob_buf32 {
        u_int32_t start;
        u_int32_t length;
        compat_caddr_t ptr;     /* unsigned char* */
};

#define MEMWRITEOOB32           _IOWR('M', 3, struct mtd_oob_buf32)
#define MEMREADOOB32            _IOWR('M', 4, struct mtd_oob_buf32)

static long mtdchar_compat_ioctl(struct file *file, unsigned int cmd,
        unsigned long arg)
{
        struct mtd_file_info *mfi = file->private_data;
        struct mtd_info *mtd = mfi->mtd;
        struct mtd_info *master = mtd_get_master(mtd);
        void __user *argp = compat_ptr(arg);
        int ret = 0;

        mutex_lock(&master->master.chrdev_lock);

        switch (cmd) {
        case MEMWRITEOOB32:
        {
                struct mtd_oob_buf32 buf;
                struct mtd_oob_buf32 __user *buf_user = argp;

                if (!(file->f_mode & FMODE_WRITE)) {
                        ret = -EPERM;
                        break;
                }

                if (copy_from_user(&buf, argp, sizeof(buf)))
                        ret = -EFAULT;
                else
                        ret = mtdchar_writeoob(file, mtd, buf.start,
                                buf.length, compat_ptr(buf.ptr),
                                &buf_user->length);
                break;
        }

        case MEMREADOOB32:
        {
                struct mtd_oob_buf32 buf;
                struct mtd_oob_buf32 __user *buf_user = argp;

                /* NOTE: writes return length to buf->start */
                if (copy_from_user(&buf, argp, sizeof(buf)))
                        ret = -EFAULT;
                else
                        ret = mtdchar_readoob(file, mtd, buf.start,
                                buf.length, compat_ptr(buf.ptr),
                                &buf_user->start);
                break;
        }

        case BLKPG:
        {
                /* Convert from blkpg_compat_ioctl_arg to blkpg_ioctl_arg */
                struct blkpg_compat_ioctl_arg __user *uarg = argp;
                struct blkpg_compat_ioctl_arg compat_arg;
                struct blkpg_ioctl_arg a;

                if (copy_from_user(&compat_arg, uarg, sizeof(compat_arg))) {
                        ret = -EFAULT;
                        break;
                }

                memset(&a, 0, sizeof(a));
                a.op = compat_arg.op;
                a.flags = compat_arg.flags;
                a.datalen = compat_arg.datalen;
                a.data = compat_ptr(compat_arg.data);

                ret = mtdchar_blkpg_ioctl(mtd, &a);
                break;
        }

        default:
                ret = mtdchar_ioctl(file, cmd, (unsigned long)argp);
        }

        mutex_unlock(&master->master.chrdev_lock);

        return ret;
}

#endif /* CONFIG_COMPAT */

/*
 * try to determine where a shared mapping can be made
 * - only supported for NOMMU at the moment (MMU can't doesn't copy private
 *   mappings)
 */
#ifndef CONFIG_MMU
static unsigned long mtdchar_get_unmapped_area(struct file *file,
                                           unsigned long addr,
                                           unsigned long len,
                                           unsigned long pgoff,
                                           unsigned long flags)
{
        struct mtd_file_info *mfi = file->private_data;
        struct mtd_info *mtd = mfi->mtd;
        unsigned long offset;
        int ret;

        if (addr != 0)
                return (unsigned long) -EINVAL;

        if (len > mtd->size || pgoff >= (mtd->size >> PAGE_SHIFT))
                return (unsigned long) -EINVAL;

        offset = pgoff << PAGE_SHIFT;
        if (offset > mtd->size - len)
                return (unsigned long) -EINVAL;

        ret = mtd_get_unmapped_area(mtd, len, offset, flags);
        return ret == -EOPNOTSUPP ? -ENODEV : ret;
}

static unsigned mtdchar_mmap_capabilities(struct file *file)
{
        struct mtd_file_info *mfi = file->private_data;

        return mtd_mmap_capabilities(mfi->mtd);
}
#endif

/*
 * set up a mapping for shared memory segments
 */
static int mtdchar_mmap_prepare(struct vm_area_desc *desc)
{
#ifdef CONFIG_MMU
        return -ENODEV;
#else
        return vma_desc_test(desc, VMA_SHARED_BIT) ? 0 : -EACCES;
#endif
}

static const struct file_operations mtd_fops = {
        .owner          = THIS_MODULE,
        .llseek         = mtdchar_lseek,
        .read           = mtdchar_read,
        .write          = mtdchar_write,
        .unlocked_ioctl = mtdchar_unlocked_ioctl,
#ifdef CONFIG_COMPAT
        .compat_ioctl   = mtdchar_compat_ioctl,
#endif
        .open           = mtdchar_open,
        .release        = mtdchar_close,
        .mmap_prepare   = mtdchar_mmap_prepare,
#ifndef CONFIG_MMU
        .get_unmapped_area = mtdchar_get_unmapped_area,
        .mmap_capabilities = mtdchar_mmap_capabilities,
#endif
};

int __init init_mtdchar(void)
{
        int ret;

        ret = __register_chrdev(MTD_CHAR_MAJOR, 0, 1 << MINORBITS,
                                   "mtd", &mtd_fops);
        if (ret < 0) {
                pr_err("Can't allocate major number %d for MTD\n",
                       MTD_CHAR_MAJOR);
                return ret;
        }

        return ret;
}

void __exit cleanup_mtdchar(void)
{
        __unregister_chrdev(MTD_CHAR_MAJOR, 0, 1 << MINORBITS, "mtd");
}

MODULE_ALIAS_CHARDEV_MAJOR(MTD_CHAR_MAJOR);