linux_mtd.c - flashprog - Gitiles

 /*
  * This file is part of the flashrom project.
  *
  * Copyright 2015 Google Inc.
  * Copyright 2018-present Facebook, Inc.
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
  * the Free Software Foundation; version 2 of the License.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  */

 #include <ctype.h>
 #include <errno.h>
 #include <fcntl.h>
 #include <stdbool.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <mtd/mtd-user.h>
 #include <string.h>
 #include <sys/ioctl.h>
 #include <sys/stat.h>
 #include <unistd.h>

 #include "flash.h"
 #include "programmer.h"

 #define LINUX_DEV_ROOT			"/dev"
 #define LINUX_MTD_SYSFS_ROOT		"/sys/class/mtd"

 struct linux_mtd_data {
 	FILE *dev_fp;
 	bool device_is_writeable;
 	bool no_erase;
 	/* Size info is presented in bytes in sysfs. */
 	unsigned long int total_size;
 	unsigned long int numeraseregions;
 	/* only valid if numeraseregions is 0 */
 	unsigned long int erasesize;
 };

 /* read a string from a sysfs file and sanitize it */
 static int read_sysfs_string(const char *sysfs_path, const char *filename, char *buf, int len)
 {
 	int i;
 	size_t bytes_read;
 	FILE *fp;
 	char path[strlen(LINUX_MTD_SYSFS_ROOT) + 32];

 	snprintf(path, sizeof(path), "%s/%s", sysfs_path, filename);

 	if ((fp = fopen(path, "r")) == NULL) {
 		msg_perr("Cannot open %s\n", path);
 		return 1;
 	}

 	clearerr(fp);
 	bytes_read = fread(buf, 1, (size_t)len, fp);
 	if (!feof(fp) && ferror(fp)) {
 		msg_perr("Error occurred when reading %s\n", path);
 		fclose(fp);
 		return 1;
 	}

 	buf[bytes_read] = '\0';

 	/*
 	 * Files from sysfs sometimes contain a newline or other garbage that
 	 * can confuse functions like strtoul() and ruin formatting in print
 	 * statements. Replace the first non-printable character (space is
 	 * considered printable) with a proper string terminator.
 	 */
 	for (i = 0; i < len; i++) {
 		if (!isprint(buf[i])) {
 			buf[i] = '\0';
 			break;
 		}
 	}

 	fclose(fp);
 	return 0;
 }

 static int read_sysfs_int(const char *sysfs_path, const char *filename, unsigned long int *val)
 {
 	char buf[32];
 	char *endptr;

 	if (read_sysfs_string(sysfs_path, filename, buf, sizeof(buf)))
 		return 1;

 	errno = 0;
 	*val = strtoul(buf, &endptr, 0);
 	if (*endptr != '\0') {
 		msg_perr("Error reading %s\n", filename);
 		return 1;
 	}

 	if (errno) {
 		msg_perr("Error reading %s: %s\n", filename, strerror(errno));
 		return 1;
 	}

 	return 0;
 }

 static int popcnt(unsigned int u)
 {
 	int count = 0;

 	while (u) {
 		u &= u - 1;
 		count++;
 	}

 	return count;
 }

 /* returns 0 to indicate success, non-zero to indicate error */
 static int get_mtd_info(const char *sysfs_path, struct linux_mtd_data *data)
 {
 	unsigned long int tmp;
 	char device_name[32];

 	/* Flags */
 	if (read_sysfs_int(sysfs_path, "flags", &tmp))
 		return 1;
 	if (tmp & MTD_WRITEABLE) {
 		/* cache for later use by write function */
 		data->device_is_writeable = true;
 	}
 	if (tmp & MTD_NO_ERASE) {
 		data->no_erase = true;
 	}

 	/* Device name */
 	if (read_sysfs_string(sysfs_path, "name", device_name, sizeof(device_name)))
 		return 1;

 	/* Total size */
 	if (read_sysfs_int(sysfs_path, "size", &data->total_size))
 		return 1;
 	if (popcnt(data->total_size) != 1) {
 		msg_perr("MTD size is not a power of 2\n");
 		return 1;
 	}

 	/* Erase size */
 	if (read_sysfs_int(sysfs_path, "erasesize", &data->erasesize))
 		return 1;
 	if (popcnt(data->erasesize) != 1) {
 		msg_perr("MTD erase size is not a power of 2\n");
 		return 1;
 	}

 	/* Erase regions */
 	if (read_sysfs_int(sysfs_path, "numeraseregions", &data->numeraseregions))
 		return 1;
 	if (data->numeraseregions != 0) {
 		msg_perr("Non-uniform eraseblock size is unsupported.\n");
 		return 1;
 	}

 	msg_pdbg("%s: device_name: \"%s\", is_writeable: %d, "
 		"numeraseregions: %lu, total_size: %lu, erasesize: %lu\n",
 		__func__, device_name, data->device_is_writeable,
 		data->numeraseregions, data->total_size, data->erasesize);

 	return 0;
 }

 static int linux_mtd_probe(struct flashctx *flash)
 {
 	struct linux_mtd_data *data = flash->mst->opaque.data;

 	if (data->no_erase)
 		flash->chip->feature_bits |= FEATURE_NO_ERASE;
 	flash->chip->tested = TEST_OK_PREW;
 	flash->chip->total_size = data->total_size / 1024;	/* bytes -> kB */
 	flash->chip->block_erasers[0].eraseblocks[0].size = data->erasesize;
 	flash->chip->block_erasers[0].eraseblocks[0].count =
 		data->total_size / data->erasesize;
 	return 1;
 }

 static int linux_mtd_read(struct flashctx *flash, uint8_t *buf,
 			  unsigned int start, unsigned int len)
 {
 	struct linux_mtd_data *data = flash->mst->opaque.data;
 	unsigned int eb_size = flash->chip->block_erasers[0].eraseblocks[0].size;
 	unsigned int i;

 	if (fseek(data->dev_fp, start, SEEK_SET) != 0) {
 		msg_perr("Cannot seek to 0x%06x: %s\n", start, strerror(errno));
 		return 1;
 	}

 	for (i = 0; i < len; ) {
 		/*
 		 * Try to align reads to eraseblock size.
 		 * FIXME: Shouldn't actually be necessary, but not all MTD
 		 * drivers handle arbitrary large reads well.
 		 */
 		unsigned int step = eb_size - ((start + i) % eb_size);
 		step = min(step, len - i);

 		if (fread(buf + i, step, 1, data->dev_fp) != 1) {
 			msg_perr("Cannot read 0x%06x bytes at 0x%06x: %s\n",
 					step, start + i, strerror(errno));
 			return 1;
 		}

 		i += step;
 	}

 	return 0;
 }

 /* this version assumes we must divide the write request into chunks ourselves */
 static int linux_mtd_write(struct flashctx *flash, const uint8_t *buf,
 				unsigned int start, unsigned int len)
 {
 	struct linux_mtd_data *data = flash->mst->opaque.data;
 	unsigned int chunksize = flash->chip->block_erasers[0].eraseblocks[0].size;
 	unsigned int i;

 	if (!data->device_is_writeable)
 		return 1;

 	if (fseek(data->dev_fp, start, SEEK_SET) != 0) {
 		msg_perr("Cannot seek to 0x%06x: %s\n", start, strerror(errno));
 		return 1;
 	}

 	/*
 	 * Try to align writes to eraseblock size. We want these large enough
 	 * to give MTD room for optimizing performance.
 	 * FIXME: Shouldn't need to divide this up at all, but not all MTD
 	 * drivers handle arbitrary large writes well.
 	 */
 	for (i = 0; i < len; ) {
 		unsigned int step = chunksize - ((start + i) % chunksize);
 		step = min(step, len - i);

 		if (fwrite(buf + i, step, 1, data->dev_fp) != 1) {
 			msg_perr("Cannot write 0x%06x bytes at 0x%06x\n", step, start + i);
 			return 1;
 		}

 		if (fflush(data->dev_fp) == EOF) {
 			msg_perr("Failed to flush buffer: %s\n", strerror(errno));
 			return 1;
 		}

 		i += step;
 	}

 	return 0;
 }

 static int linux_mtd_erase(struct flashctx *flash,
 			unsigned int start, unsigned int len)
 {
 	struct linux_mtd_data *data = flash->mst->opaque.data;
 	uint32_t u;

 	if (data->no_erase) {
 		msg_perr("%s: device does not support erasing.\n"
 			 "Please file a bug report at flashrom-stable@flashrom.org\n",
 			 __func__);
 		return 1;
 	}

 	if (data->numeraseregions != 0) {
 		/* TODO: Support non-uniform eraseblock size using
 		   use MEMGETREGIONCOUNT/MEMGETREGIONINFO ioctls */
 		msg_perr("%s: numeraseregions must be 0\n", __func__);
 		return 1;
 	}

 	for (u = 0; u < len; u += data->erasesize) {
 		struct erase_info_user erase_info = {
 			.start = start + u,
 			.length = data->erasesize,
 		};

 		int ret = ioctl(fileno(data->dev_fp), MEMERASE, &erase_info);
 		if (ret < 0) {
 		        msg_perr("%s: MEMERASE ioctl call returned %d, error: %s\n",
 		                 __func__, ret, strerror(errno));
 		        return 1;
 		}
 	}

 	return 0;
 }

 static int linux_mtd_shutdown(void *data);

 static const struct opaque_master linux_mtd_opaque_master = {
 	/* max_data_{read,write} don't have any effect for this programmer */
 	.max_data_read	= MAX_DATA_UNSPECIFIED,
 	.max_data_write	= MAX_DATA_UNSPECIFIED,
 	.probe		= linux_mtd_probe,
 	.read		= linux_mtd_read,
 	.write		= linux_mtd_write,
 	.erase		= linux_mtd_erase,
 	.shutdown	= linux_mtd_shutdown,
 };

 /* Returns 0 if setup is successful, non-zero to indicate error */
 static int linux_mtd_setup(int dev_num, struct linux_mtd_data *data)
 {
 	char sysfs_path[32];
 	int ret = 1;

 	/* Start by checking /sys/class/mtd/mtdN/type which should be "nor" for NOR flash */
 	if (snprintf(sysfs_path, sizeof(sysfs_path), "%s/mtd%d/", LINUX_MTD_SYSFS_ROOT, dev_num) < 0)
 		goto linux_mtd_setup_exit;

 	char buf[4] = { 0 };
 	if (read_sysfs_string(sysfs_path, "type", buf, sizeof(buf)))
 		return 1;

 	if (strcmp(buf, "nor")) {
 		msg_perr("MTD device %d type is not \"nor\"\n", dev_num);
 		goto linux_mtd_setup_exit;
 	}

 	/* sysfs shows the correct device type, see if corresponding device node exists */
 	char dev_path[32];
 	struct stat s;
 	snprintf(dev_path, sizeof(dev_path), "%s/mtd%d", LINUX_DEV_ROOT, dev_num);
 	errno = 0;
 	if (stat(dev_path, &s) < 0) {
 		msg_pdbg("Cannot stat \"%s\": %s\n", dev_path, strerror(errno));
 		goto linux_mtd_setup_exit;
 	}

 	/* so far so good, get more info from other files in this dir */
 	if (snprintf(sysfs_path, sizeof(sysfs_path), "%s/mtd%d/", LINUX_MTD_SYSFS_ROOT, dev_num) < 0)
 		goto linux_mtd_setup_exit;
 	if (get_mtd_info(sysfs_path, data))
 		goto linux_mtd_setup_exit;

 	/* open file stream and go! */
 	if ((data->dev_fp = fopen(dev_path, "r+")) == NULL) {
 		msg_perr("Cannot open file stream for %s\n", dev_path);
 		goto linux_mtd_setup_exit;
 	}
 	ret = setvbuf(data->dev_fp, NULL, _IONBF, 0);
 	if (ret)
 		msg_pwarn("Failed to set MTD device to unbuffered: %d\n", ret);

 	msg_pinfo("Opened %s successfully\n", dev_path);

 	ret = 0;
 linux_mtd_setup_exit:
 	return ret;
 }

 static int linux_mtd_shutdown(void *data)
 {
 	struct linux_mtd_data *mtd_data = data;
 	if (mtd_data->dev_fp != NULL) {
 		fclose(mtd_data->dev_fp);
 	}
 	free(data);

 	return 0;
 }

 static int linux_mtd_init(void)
 {
 	char *param;
 	int dev_num = 0;
 	int ret = 1;
 	struct linux_mtd_data *data = NULL;

 	param = extract_programmer_param("dev");
 	if (param) {
 		char *endptr;

 		dev_num = strtol(param, &endptr, 0);
 		if ((*endptr != '\0') || (dev_num < 0)) {
 			msg_perr("Invalid device number %s. Use flashrom -p "
 				"linux_mtd:dev=N where N is a valid MTD\n"
 				"device number.\n", param);
 			goto linux_mtd_init_exit;
 		}
 	}

 	/*
 	 * If user specified the MTD device number then error out if it doesn't
 	 * appear to exist. Otherwise assume the error is benign and print a
 	 * debug message. Bail out in either case.
 	 */
 	char sysfs_path[32];
 	if (snprintf(sysfs_path, sizeof(sysfs_path), "%s/mtd%d", LINUX_MTD_SYSFS_ROOT, dev_num) < 0)
 		goto linux_mtd_init_exit;

 	struct stat s;
 	if (stat(sysfs_path, &s) < 0) {
 		if (param)
 			msg_perr("%s does not exist\n", sysfs_path);
 		else
 			msg_pdbg("%s does not exist\n", sysfs_path);
 		goto linux_mtd_init_exit;
 	}
 	free(param);

 	data = calloc(1, sizeof(*data));
 	if (!data) {
 		msg_perr("Unable to allocate memory for linux_mtd_data\n");
 		return 1;
 	}

 	/* Get MTD info and store it in `data` */
 	if (linux_mtd_setup(dev_num, data)) {
 		free(data);
 		return 1;
 	}

 	return register_opaque_master(&linux_mtd_opaque_master, data);

 linux_mtd_init_exit:
 	free(param);
 	return ret;
 }

 const struct programmer_entry programmer_linux_mtd = {
 	.name			= "linux_mtd",
 	.type			= OTHER,
 	.devs.note		= "Device files /dev/mtd*\n",
 	.init			= linux_mtd_init,
 };
	/*
	* This file is part of the flashrom project.
	*
	* Copyright 2015 Google Inc.
	* Copyright 2018-present Facebook, Inc.
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License as published by
	* the Free Software Foundation; version 2 of the License.
	*
	* This program is distributed in the hope that it will be useful,
	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	* GNU General Public License for more details.
	*/

	#include <ctype.h>
	#include <errno.h>
	#include <fcntl.h>
	#include <stdbool.h>
	#include <stdio.h>
	#include <stdlib.h>
	#include <mtd/mtd-user.h>
	#include <string.h>
	#include <sys/ioctl.h>
	#include <sys/stat.h>
	#include <unistd.h>

	#include "flash.h"
	#include "programmer.h"

	#define LINUX_DEV_ROOT "/dev"
	#define LINUX_MTD_SYSFS_ROOT "/sys/class/mtd"

	struct linux_mtd_data {
	FILE *dev_fp;
	bool device_is_writeable;
	bool no_erase;
	/* Size info is presented in bytes in sysfs. */
	unsigned long int total_size;
	unsigned long int numeraseregions;
	/* only valid if numeraseregions is 0 */
	unsigned long int erasesize;
	};

	/* read a string from a sysfs file and sanitize it */
	static int read_sysfs_string(const char sysfs_path, const char filename, char *buf, int len)
	{
	int i;
	size_t bytes_read;
	FILE *fp;
	char path[strlen(LINUX_MTD_SYSFS_ROOT) + 32];

	snprintf(path, sizeof(path), "%s/%s", sysfs_path, filename);

	if ((fp = fopen(path, "r")) == NULL) {
	msg_perr("Cannot open %s\n", path);
	return 1;
	}

	clearerr(fp);
	bytes_read = fread(buf, 1, (size_t)len, fp);
	if (!feof(fp) && ferror(fp)) {
	msg_perr("Error occurred when reading %s\n", path);
	fclose(fp);
	return 1;
	}

	buf[bytes_read] = '\0';

	/*
	* Files from sysfs sometimes contain a newline or other garbage that
	* can confuse functions like strtoul() and ruin formatting in print
	* statements. Replace the first non-printable character (space is
	* considered printable) with a proper string terminator.
	*/
	for (i = 0; i < len; i++) {
	if (!isprint(buf[i])) {
	buf[i] = '\0';
	break;
	}
	}

	fclose(fp);
	return 0;
	}

	static int read_sysfs_int(const char sysfs_path, const char filename, unsigned long int *val)
	{
	char buf[32];
	char *endptr;

	if (read_sysfs_string(sysfs_path, filename, buf, sizeof(buf)))
	return 1;

	errno = 0;
	*val = strtoul(buf, &endptr, 0);
	if (*endptr != '\0') {
	msg_perr("Error reading %s\n", filename);
	return 1;
	}

	if (errno) {
	msg_perr("Error reading %s: %s\n", filename, strerror(errno));
	return 1;
	}

	return 0;
	}

	static int popcnt(unsigned int u)
	{
	int count = 0;

	while (u) {
	u &= u - 1;
	count++;
	}

	return count;
	}

	/* returns 0 to indicate success, non-zero to indicate error */
	static int get_mtd_info(const char sysfs_path, struct linux_mtd_data data)
	{
	unsigned long int tmp;
	char device_name[32];

	/* Flags */
	if (read_sysfs_int(sysfs_path, "flags", &tmp))
	return 1;
	if (tmp & MTD_WRITEABLE) {
	/* cache for later use by write function */
	data->device_is_writeable = true;
	}
	if (tmp & MTD_NO_ERASE) {
	data->no_erase = true;
	}

	/* Device name */
	if (read_sysfs_string(sysfs_path, "name", device_name, sizeof(device_name)))
	return 1;

	/* Total size */
	if (read_sysfs_int(sysfs_path, "size", &data->total_size))
	return 1;
	if (popcnt(data->total_size) != 1) {
	msg_perr("MTD size is not a power of 2\n");
	return 1;
	}

	/* Erase size */
	if (read_sysfs_int(sysfs_path, "erasesize", &data->erasesize))
	return 1;
	if (popcnt(data->erasesize) != 1) {
	msg_perr("MTD erase size is not a power of 2\n");
	return 1;
	}

	/* Erase regions */
	if (read_sysfs_int(sysfs_path, "numeraseregions", &data->numeraseregions))
	return 1;
	if (data->numeraseregions != 0) {
	msg_perr("Non-uniform eraseblock size is unsupported.\n");
	return 1;
	}

	msg_pdbg("%s: device_name: \"%s\", is_writeable: %d, "
	"numeraseregions: %lu, total_size: %lu, erasesize: %lu\n",
	__func__, device_name, data->device_is_writeable,
	data->numeraseregions, data->total_size, data->erasesize);

	return 0;
	}

	static int linux_mtd_probe(struct flashctx *flash)
	{
	struct linux_mtd_data *data = flash->mst->opaque.data;

	if (data->no_erase)
	flash->chip->feature_bits \|= FEATURE_NO_ERASE;
	flash->chip->tested = TEST_OK_PREW;
	flash->chip->total_size = data->total_size / 1024; /* bytes -> kB */
	flash->chip->block_erasers[0].eraseblocks[0].size = data->erasesize;
	flash->chip->block_erasers[0].eraseblocks[0].count =
	data->total_size / data->erasesize;
	return 1;
	}

	static int linux_mtd_read(struct flashctx flash, uint8_t buf,
	unsigned int start, unsigned int len)
	{
	struct linux_mtd_data *data = flash->mst->opaque.data;
	unsigned int eb_size = flash->chip->block_erasers[0].eraseblocks[0].size;
	unsigned int i;

	if (fseek(data->dev_fp, start, SEEK_SET) != 0) {
	msg_perr("Cannot seek to 0x%06x: %s\n", start, strerror(errno));
	return 1;
	}

	for (i = 0; i < len; ) {
	/*
	* Try to align reads to eraseblock size.
	* FIXME: Shouldn't actually be necessary, but not all MTD
	* drivers handle arbitrary large reads well.
	*/
	unsigned int step = eb_size - ((start + i) % eb_size);
	step = min(step, len - i);

	if (fread(buf + i, step, 1, data->dev_fp) != 1) {
	msg_perr("Cannot read 0x%06x bytes at 0x%06x: %s\n",
	step, start + i, strerror(errno));
	return 1;
	}

	i += step;
	}

	return 0;
	}

	/* this version assumes we must divide the write request into chunks ourselves */
	static int linux_mtd_write(struct flashctx flash, const uint8_t buf,
	unsigned int start, unsigned int len)
	{
	struct linux_mtd_data *data = flash->mst->opaque.data;
	unsigned int chunksize = flash->chip->block_erasers[0].eraseblocks[0].size;
	unsigned int i;

	if (!data->device_is_writeable)
	return 1;

	if (fseek(data->dev_fp, start, SEEK_SET) != 0) {
	msg_perr("Cannot seek to 0x%06x: %s\n", start, strerror(errno));
	return 1;
	}

	/*
	* Try to align writes to eraseblock size. We want these large enough
	* to give MTD room for optimizing performance.
	* FIXME: Shouldn't need to divide this up at all, but not all MTD
	* drivers handle arbitrary large writes well.
	*/
	for (i = 0; i < len; ) {
	unsigned int step = chunksize - ((start + i) % chunksize);
	step = min(step, len - i);

	if (fwrite(buf + i, step, 1, data->dev_fp) != 1) {
	msg_perr("Cannot write 0x%06x bytes at 0x%06x\n", step, start + i);
	return 1;
	}

	if (fflush(data->dev_fp) == EOF) {
	msg_perr("Failed to flush buffer: %s\n", strerror(errno));
	return 1;
	}

	i += step;
	}

	return 0;
	}

	static int linux_mtd_erase(struct flashctx *flash,
	unsigned int start, unsigned int len)
	{
	struct linux_mtd_data *data = flash->mst->opaque.data;
	uint32_t u;

	if (data->no_erase) {
	msg_perr("%s: device does not support erasing.\n"
	"Please file a bug report at flashrom-stable@flashrom.org\n",
	__func__);
	return 1;
	}

	if (data->numeraseregions != 0) {
	/* TODO: Support non-uniform eraseblock size using
	use MEMGETREGIONCOUNT/MEMGETREGIONINFO ioctls */
	msg_perr("%s: numeraseregions must be 0\n", __func__);
	return 1;
	}

	for (u = 0; u < len; u += data->erasesize) {
	struct erase_info_user erase_info = {
	.start = start + u,
	.length = data->erasesize,
	};

	int ret = ioctl(fileno(data->dev_fp), MEMERASE, &erase_info);
	if (ret < 0) {
	msg_perr("%s: MEMERASE ioctl call returned %d, error: %s\n",
	__func__, ret, strerror(errno));
	return 1;
	}
	}

	return 0;
	}

	static int linux_mtd_shutdown(void *data);

	static const struct opaque_master linux_mtd_opaque_master = {
	/* max_data_{read,write} don't have any effect for this programmer */
	.max_data_read = MAX_DATA_UNSPECIFIED,
	.max_data_write = MAX_DATA_UNSPECIFIED,
	.probe = linux_mtd_probe,
	.read = linux_mtd_read,
	.write = linux_mtd_write,
	.erase = linux_mtd_erase,
	.shutdown = linux_mtd_shutdown,
	};

	/* Returns 0 if setup is successful, non-zero to indicate error */
	static int linux_mtd_setup(int dev_num, struct linux_mtd_data *data)
	{
	char sysfs_path[32];
	int ret = 1;

	/* Start by checking /sys/class/mtd/mtdN/type which should be "nor" for NOR flash */
	if (snprintf(sysfs_path, sizeof(sysfs_path), "%s/mtd%d/", LINUX_MTD_SYSFS_ROOT, dev_num) < 0)
	goto linux_mtd_setup_exit;

	char buf[4] = { 0 };
	if (read_sysfs_string(sysfs_path, "type", buf, sizeof(buf)))
	return 1;

	if (strcmp(buf, "nor")) {
	msg_perr("MTD device %d type is not \"nor\"\n", dev_num);
	goto linux_mtd_setup_exit;
	}

	/* sysfs shows the correct device type, see if corresponding device node exists */
	char dev_path[32];
	struct stat s;
	snprintf(dev_path, sizeof(dev_path), "%s/mtd%d", LINUX_DEV_ROOT, dev_num);
	errno = 0;
	if (stat(dev_path, &s) < 0) {
	msg_pdbg("Cannot stat \"%s\": %s\n", dev_path, strerror(errno));
	goto linux_mtd_setup_exit;
	}

	/* so far so good, get more info from other files in this dir */
	if (snprintf(sysfs_path, sizeof(sysfs_path), "%s/mtd%d/", LINUX_MTD_SYSFS_ROOT, dev_num) < 0)
	goto linux_mtd_setup_exit;
	if (get_mtd_info(sysfs_path, data))
	goto linux_mtd_setup_exit;

	/* open file stream and go! */
	if ((data->dev_fp = fopen(dev_path, "r+")) == NULL) {
	msg_perr("Cannot open file stream for %s\n", dev_path);
	goto linux_mtd_setup_exit;
	}
	ret = setvbuf(data->dev_fp, NULL, _IONBF, 0);
	if (ret)
	msg_pwarn("Failed to set MTD device to unbuffered: %d\n", ret);

	msg_pinfo("Opened %s successfully\n", dev_path);

	ret = 0;
	linux_mtd_setup_exit:
	return ret;
	}

	static int linux_mtd_shutdown(void *data)
	{
	struct linux_mtd_data *mtd_data = data;
	if (mtd_data->dev_fp != NULL) {
	fclose(mtd_data->dev_fp);
	}
	free(data);

	return 0;
	}

	static int linux_mtd_init(void)
	{
	char *param;
	int dev_num = 0;
	int ret = 1;
	struct linux_mtd_data *data = NULL;

	param = extract_programmer_param("dev");
	if (param) {
	char *endptr;

	dev_num = strtol(param, &endptr, 0);
	if ((*endptr != '\0') \|\| (dev_num < 0)) {
	msg_perr("Invalid device number %s. Use flashrom -p "
	"linux_mtd:dev=N where N is a valid MTD\n"
	"device number.\n", param);
	goto linux_mtd_init_exit;
	}
	}

	/*
	* If user specified the MTD device number then error out if it doesn't
	* appear to exist. Otherwise assume the error is benign and print a
	* debug message. Bail out in either case.
	*/
	char sysfs_path[32];
	if (snprintf(sysfs_path, sizeof(sysfs_path), "%s/mtd%d", LINUX_MTD_SYSFS_ROOT, dev_num) < 0)
	goto linux_mtd_init_exit;

	struct stat s;
	if (stat(sysfs_path, &s) < 0) {
	if (param)
	msg_perr("%s does not exist\n", sysfs_path);
	else
	msg_pdbg("%s does not exist\n", sysfs_path);
	goto linux_mtd_init_exit;
	}
	free(param);

	data = calloc(1, sizeof(*data));
	if (!data) {
	msg_perr("Unable to allocate memory for linux_mtd_data\n");
	return 1;
	}

	/* Get MTD info and store it in `data` */
	if (linux_mtd_setup(dev_num, data)) {
	free(data);
	return 1;
	}

	return register_opaque_master(&linux_mtd_opaque_master, data);

	linux_mtd_init_exit:
	free(param);
	return ret;
	}

	const struct programmer_entry programmer_linux_mtd = {
	.name = "linux_mtd",
	.type = OTHER,
	.devs.note = "Device files /dev/mtd*\n",
	.init = linux_mtd_init,
	};