xref: /openbmc/linux/drivers/mtd/mtdchar.c (revision 0ea923f4)

// 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(sizeof(*mfi), GFP_KERNEL);
	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;

	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 (req.start + req.len > 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;

	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 (req.start + req.len > 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(sizeof(struct erase_info),GFP_KERNEL);
		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(sizeof(*usrlay), GFP_KERNEL);
		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(struct file *file, struct vm_area_struct *vma)
{
#ifdef CONFIG_MMU
	struct mtd_file_info *mfi = file->private_data;
	struct mtd_info *mtd = mfi->mtd;
	struct map_info *map = mtd->priv;

        /* This is broken because it assumes the MTD device is map-based
	   and that mtd->priv is a valid struct map_info.  It should be
	   replaced with something that uses the mtd_get_unmapped_area()
	   operation properly. */
	if (0 /*mtd->type == MTD_RAM || mtd->type == MTD_ROM*/) {
#ifdef pgprot_noncached
		if (file->f_flags & O_DSYNC || map->phys >= __pa(high_memory))
			vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
#endif
		return vm_iomap_memory(vma, map->phys, map->size);
	}
	return -ENODEV;
#else
	return vma->vm_flags & VM_SHARED ? 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		= mtdchar_mmap,
#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);