drivers/misc/eeprom/at25.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * at25.c -- support most SPI EEPROMs, such as Atmel AT25 models
  *
  * Copyright (C) 2006 David Brownell
  */

 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/slab.h>
 #include <linux/delay.h>
 #include <linux/device.h>
 #include <linux/sched.h>

 #include <linux/nvmem-provider.h>
 #include <linux/spi/spi.h>
 #include <linux/spi/eeprom.h>
 #include <linux/property.h>

 /*
  * NOTE: this is an *EEPROM* driver.  The vagaries of product naming
  * mean that some AT25 products are EEPROMs, and others are FLASH.
  * Handle FLASH chips with the drivers/mtd/devices/m25p80.c driver,
  * not this one!
  *
  * EEPROMs that can be used with this driver include, for example:
  *   AT25M02, AT25128B
  */

 struct at25_data {
 	struct spi_device	*spi;
 	struct mutex		lock;
 	struct spi_eeprom	chip;
 	unsigned		addrlen;
 	struct nvmem_config	nvmem_config;
 	struct nvmem_device	*nvmem;
 };

 #define	AT25_WREN	0x06		/* latch the write enable */
 #define	AT25_WRDI	0x04		/* reset the write enable */
 #define	AT25_RDSR	0x05		/* read status register */
 #define	AT25_WRSR	0x01		/* write status register */
 #define	AT25_READ	0x03		/* read byte(s) */
 #define	AT25_WRITE	0x02		/* write byte(s)/sector */

 #define	AT25_SR_nRDY	0x01		/* nRDY = write-in-progress */
 #define	AT25_SR_WEN	0x02		/* write enable (latched) */
 #define	AT25_SR_BP0	0x04		/* BP for software writeprotect */
 #define	AT25_SR_BP1	0x08
 #define	AT25_SR_WPEN	0x80		/* writeprotect enable */

 #define	AT25_INSTR_BIT3	0x08		/* Additional address bit in instr */

 #define EE_MAXADDRLEN	3		/* 24 bit addresses, up to 2 MBytes */

 /* Specs often allow 5 msec for a page write, sometimes 20 msec;
  * it's important to recover from write timeouts.
  */
 #define	EE_TIMEOUT	25

 /*-------------------------------------------------------------------------*/

 #define	io_limit	PAGE_SIZE	/* bytes */

 static int at25_ee_read(void *priv, unsigned int offset,
 			void *val, size_t count)
 {
 	struct at25_data *at25 = priv;
 	char *buf = val;
 	u8			command[EE_MAXADDRLEN + 1];
 	u8			*cp;
 	ssize_t			status;
 	struct spi_transfer	t[2];
 	struct spi_message	m;
 	u8			instr;

 	if (unlikely(offset >= at25->chip.byte_len))
 		return -EINVAL;
 	if ((offset + count) > at25->chip.byte_len)
 		count = at25->chip.byte_len - offset;
 	if (unlikely(!count))
 		return -EINVAL;

 	cp = command;

 	instr = AT25_READ;
 	if (at25->chip.flags & EE_INSTR_BIT3_IS_ADDR)
 		if (offset >= (1U << (at25->addrlen * 8)))
 			instr |= AT25_INSTR_BIT3;
 	*cp++ = instr;

 	/* 8/16/24-bit address is written MSB first */
 	switch (at25->addrlen) {
 	default:	/* case 3 */
 		*cp++ = offset >> 16;
 		fallthrough;
 	case 2:
 		*cp++ = offset >> 8;
 		fallthrough;
 	case 1:
 	case 0:	/* can't happen: for better codegen */
 		*cp++ = offset >> 0;
 	}

 	spi_message_init(&m);
 	memset(t, 0, sizeof(t));

 	t[0].tx_buf = command;
 	t[0].len = at25->addrlen + 1;
 	spi_message_add_tail(&t[0], &m);

 	t[1].rx_buf = buf;
 	t[1].len = count;
 	spi_message_add_tail(&t[1], &m);

 	mutex_lock(&at25->lock);

 	/* Read it all at once.
 	 *
 	 * REVISIT that's potentially a problem with large chips, if
 	 * other devices on the bus need to be accessed regularly or
 	 * this chip is clocked very slowly
 	 */
 	status = spi_sync(at25->spi, &m);
 	dev_dbg(&at25->spi->dev, "read %zu bytes at %d --> %zd\n",
 		count, offset, status);

 	mutex_unlock(&at25->lock);
 	return status;
 }

 static int at25_ee_write(void *priv, unsigned int off, void *val, size_t count)
 {
 	struct at25_data *at25 = priv;
 	const char *buf = val;
 	int			status = 0;
 	unsigned		buf_size;
 	u8			*bounce;

 	if (unlikely(off >= at25->chip.byte_len))
 		return -EFBIG;
 	if ((off + count) > at25->chip.byte_len)
 		count = at25->chip.byte_len - off;
 	if (unlikely(!count))
 		return -EINVAL;

 	/* Temp buffer starts with command and address */
 	buf_size = at25->chip.page_size;
 	if (buf_size > io_limit)
 		buf_size = io_limit;
 	bounce = kmalloc(buf_size + at25->addrlen + 1, GFP_KERNEL);
 	if (!bounce)
 		return -ENOMEM;

 	/* For write, rollover is within the page ... so we write at
 	 * most one page, then manually roll over to the next page.
 	 */
 	mutex_lock(&at25->lock);
 	do {
 		unsigned long	timeout, retries;
 		unsigned	segment;
 		unsigned	offset = (unsigned) off;
 		u8		*cp = bounce;
 		int		sr;
 		u8		instr;

 		*cp = AT25_WREN;
 		status = spi_write(at25->spi, cp, 1);
 		if (status < 0) {
 			dev_dbg(&at25->spi->dev, "WREN --> %d\n", status);
 			break;
 		}

 		instr = AT25_WRITE;
 		if (at25->chip.flags & EE_INSTR_BIT3_IS_ADDR)
 			if (offset >= (1U << (at25->addrlen * 8)))
 				instr |= AT25_INSTR_BIT3;
 		*cp++ = instr;

 		/* 8/16/24-bit address is written MSB first */
 		switch (at25->addrlen) {
 		default:	/* case 3 */
 			*cp++ = offset >> 16;
 			fallthrough;
 		case 2:
 			*cp++ = offset >> 8;
 			fallthrough;
 		case 1:
 		case 0:	/* can't happen: for better codegen */
 			*cp++ = offset >> 0;
 		}

 		/* Write as much of a page as we can */
 		segment = buf_size - (offset % buf_size);
 		if (segment > count)
 			segment = count;
 		memcpy(cp, buf, segment);
 		status = spi_write(at25->spi, bounce,
 				segment + at25->addrlen + 1);
 		dev_dbg(&at25->spi->dev, "write %u bytes at %u --> %d\n",
 			segment, offset, status);
 		if (status < 0)
 			break;

 		/* REVISIT this should detect (or prevent) failed writes
 		 * to readonly sections of the EEPROM...
 		 */

 		/* Wait for non-busy status */
 		timeout = jiffies + msecs_to_jiffies(EE_TIMEOUT);
 		retries = 0;
 		do {

 			sr = spi_w8r8(at25->spi, AT25_RDSR);
 			if (sr < 0 || (sr & AT25_SR_nRDY)) {
 				dev_dbg(&at25->spi->dev,
 					"rdsr --> %d (%02x)\n", sr, sr);
 				/* at HZ=100, this is sloooow */
 				msleep(1);
 				continue;
 			}
 			if (!(sr & AT25_SR_nRDY))
 				break;
 		} while (retries++ < 3 || time_before_eq(jiffies, timeout));

 		if ((sr < 0) || (sr & AT25_SR_nRDY)) {
 			dev_err(&at25->spi->dev,
 				"write %u bytes offset %u, timeout after %u msecs\n",
 				segment, offset,
 				jiffies_to_msecs(jiffies -
 					(timeout - EE_TIMEOUT)));
 			status = -ETIMEDOUT;
 			break;
 		}

 		off += segment;
 		buf += segment;
 		count -= segment;

 	} while (count > 0);

 	mutex_unlock(&at25->lock);

 	kfree(bounce);
 	return status;
 }

 /*-------------------------------------------------------------------------*/

 static int at25_fw_to_chip(struct device *dev, struct spi_eeprom *chip)
 {
 	u32 val;

 	memset(chip, 0, sizeof(*chip));
 	strncpy(chip->name, "at25", sizeof(chip->name));

 	if (device_property_read_u32(dev, "size", &val) == 0 ||
 	    device_property_read_u32(dev, "at25,byte-len", &val) == 0) {
 		chip->byte_len = val;
 	} else {
 		dev_err(dev, "Error: missing \"size\" property\n");
 		return -ENODEV;
 	}

 	if (device_property_read_u32(dev, "pagesize", &val) == 0 ||
 	    device_property_read_u32(dev, "at25,page-size", &val) == 0) {
 		chip->page_size = val;
 	} else {
 		dev_err(dev, "Error: missing \"pagesize\" property\n");
 		return -ENODEV;
 	}

 	if (device_property_read_u32(dev, "at25,addr-mode", &val) == 0) {
 		chip->flags = (u16)val;
 	} else {
 		if (device_property_read_u32(dev, "address-width", &val)) {
 			dev_err(dev,
 				"Error: missing \"address-width\" property\n");
 			return -ENODEV;
 		}
 		switch (val) {
 		case 9:
 			chip->flags |= EE_INSTR_BIT3_IS_ADDR;
 			fallthrough;
 		case 8:
 			chip->flags |= EE_ADDR1;
 			break;
 		case 16:
 			chip->flags |= EE_ADDR2;
 			break;
 		case 24:
 			chip->flags |= EE_ADDR3;
 			break;
 		default:
 			dev_err(dev,
 				"Error: bad \"address-width\" property: %u\n",
 				val);
 			return -ENODEV;
 		}
 		if (device_property_present(dev, "read-only"))
 			chip->flags |= EE_READONLY;
 	}
 	return 0;
 }

 static int at25_probe(struct spi_device *spi)
 {
 	struct at25_data	*at25 = NULL;
 	struct spi_eeprom	chip;
 	int			err;
 	int			sr;
 	int			addrlen;

 	/* Chip description */
 	if (!spi->dev.platform_data) {
 		err = at25_fw_to_chip(&spi->dev, &chip);
 		if (err)
 			return err;
 	} else
 		chip = *(struct spi_eeprom *)spi->dev.platform_data;

 	/* For now we only support 8/16/24 bit addressing */
 	if (chip.flags & EE_ADDR1)
 		addrlen = 1;
 	else if (chip.flags & EE_ADDR2)
 		addrlen = 2;
 	else if (chip.flags & EE_ADDR3)
 		addrlen = 3;
 	else {
 		dev_dbg(&spi->dev, "unsupported address type\n");
 		return -EINVAL;
 	}

 	/* Ping the chip ... the status register is pretty portable,
 	 * unlike probing manufacturer IDs.  We do expect that system
 	 * firmware didn't write it in the past few milliseconds!
 	 */
 	sr = spi_w8r8(spi, AT25_RDSR);
 	if (sr < 0 || sr & AT25_SR_nRDY) {
 		dev_dbg(&spi->dev, "rdsr --> %d (%02x)\n", sr, sr);
 		return -ENXIO;
 	}

 	at25 = devm_kzalloc(&spi->dev, sizeof(struct at25_data), GFP_KERNEL);
 	if (!at25)
 		return -ENOMEM;

 	mutex_init(&at25->lock);
 	at25->chip = chip;
 	at25->spi = spi;
 	spi_set_drvdata(spi, at25);
 	at25->addrlen = addrlen;

 	at25->nvmem_config.type = NVMEM_TYPE_EEPROM;
 	at25->nvmem_config.name = dev_name(&spi->dev);
 	at25->nvmem_config.dev = &spi->dev;
 	at25->nvmem_config.read_only = chip.flags & EE_READONLY;
 	at25->nvmem_config.root_only = true;
 	at25->nvmem_config.owner = THIS_MODULE;
 	at25->nvmem_config.compat = true;
 	at25->nvmem_config.base_dev = &spi->dev;
 	at25->nvmem_config.reg_read = at25_ee_read;
 	at25->nvmem_config.reg_write = at25_ee_write;
 	at25->nvmem_config.priv = at25;
 	at25->nvmem_config.stride = 1;
 	at25->nvmem_config.word_size = 1;
 	at25->nvmem_config.size = chip.byte_len;

 	at25->nvmem = devm_nvmem_register(&spi->dev, &at25->nvmem_config);
 	if (IS_ERR(at25->nvmem))
 		return PTR_ERR(at25->nvmem);

 	dev_info(&spi->dev, "%d %s %s eeprom%s, pagesize %u\n",
 		(chip.byte_len < 1024) ? chip.byte_len : (chip.byte_len / 1024),
 		(chip.byte_len < 1024) ? "Byte" : "KByte",
 		at25->chip.name,
 		(chip.flags & EE_READONLY) ? " (readonly)" : "",
 		at25->chip.page_size);
 	return 0;
 }

 /*-------------------------------------------------------------------------*/

 static const struct of_device_id at25_of_match[] = {
 	{ .compatible = "atmel,at25", },
 	{ }
 };
 MODULE_DEVICE_TABLE(of, at25_of_match);

 static struct spi_driver at25_driver = {
 	.driver = {
 		.name		= "at25",
 		.of_match_table = at25_of_match,
 	},
 	.probe		= at25_probe,
 };

 module_spi_driver(at25_driver);

 MODULE_DESCRIPTION("Driver for most SPI EEPROMs");
 MODULE_AUTHOR("David Brownell");
 MODULE_LICENSE("GPL");
 MODULE_ALIAS("spi:at25");
	// SPDX-License-Identifier: GPL-2.0-or-later
	/*
	* at25.c -- support most SPI EEPROMs, such as Atmel AT25 models
	*
	* Copyright (C) 2006 David Brownell
	*/

	#include <linux/kernel.h>
	#include <linux/module.h>
	#include <linux/slab.h>
	#include <linux/delay.h>
	#include <linux/device.h>
	#include <linux/sched.h>

	#include <linux/nvmem-provider.h>
	#include <linux/spi/spi.h>
	#include <linux/spi/eeprom.h>
	#include <linux/property.h>

	/*
	* NOTE: this is an EEPROM driver. The vagaries of product naming
	* mean that some AT25 products are EEPROMs, and others are FLASH.
	* Handle FLASH chips with the drivers/mtd/devices/m25p80.c driver,
	* not this one!
	*
	* EEPROMs that can be used with this driver include, for example:
	* AT25M02, AT25128B
	*/

	struct at25_data {
	struct spi_device *spi;
	struct mutex lock;
	struct spi_eeprom chip;
	unsigned addrlen;
	struct nvmem_config nvmem_config;
	struct nvmem_device *nvmem;
	};

	#define AT25_WREN 0x06 /* latch the write enable */
	#define AT25_WRDI 0x04 /* reset the write enable */
	#define AT25_RDSR 0x05 /* read status register */
	#define AT25_WRSR 0x01 /* write status register */
	#define AT25_READ 0x03 /* read byte(s) */
	#define AT25_WRITE 0x02 /* write byte(s)/sector */

	#define AT25_SR_nRDY 0x01 /* nRDY = write-in-progress */
	#define AT25_SR_WEN 0x02 /* write enable (latched) */
	#define AT25_SR_BP0 0x04 /* BP for software writeprotect */
	#define AT25_SR_BP1 0x08
	#define AT25_SR_WPEN 0x80 /* writeprotect enable */

	#define AT25_INSTR_BIT3 0x08 /* Additional address bit in instr */

	#define EE_MAXADDRLEN 3 /* 24 bit addresses, up to 2 MBytes */

	/* Specs often allow 5 msec for a page write, sometimes 20 msec;
	* it's important to recover from write timeouts.
	*/
	#define EE_TIMEOUT 25

	/-------------------------------------------------------------------------/

	#define io_limit PAGE_SIZE /* bytes */

	static int at25_ee_read(void *priv, unsigned int offset,
	void *val, size_t count)
	{
	struct at25_data *at25 = priv;
	char *buf = val;
	u8 command[EE_MAXADDRLEN + 1];
	u8 *cp;
	ssize_t status;
	struct spi_transfer t[2];
	struct spi_message m;
	u8 instr;

	if (unlikely(offset >= at25->chip.byte_len))
	return -EINVAL;
	if ((offset + count) > at25->chip.byte_len)
	count = at25->chip.byte_len - offset;
	if (unlikely(!count))
	return -EINVAL;

	cp = command;

	instr = AT25_READ;
	if (at25->chip.flags & EE_INSTR_BIT3_IS_ADDR)
	if (offset >= (1U << (at25->addrlen * 8)))
	instr \|= AT25_INSTR_BIT3;
	*cp++ = instr;

	/* 8/16/24-bit address is written MSB first */
	switch (at25->addrlen) {
	default: /* case 3 */
	*cp++ = offset >> 16;
	fallthrough;
	case 2:
	*cp++ = offset >> 8;
	fallthrough;
	case 1:
	case 0: /* can't happen: for better codegen */
	*cp++ = offset >> 0;
	}

	spi_message_init(&m);
	memset(t, 0, sizeof(t));

	t[0].tx_buf = command;
	t[0].len = at25->addrlen + 1;
	spi_message_add_tail(&t[0], &m);

	t[1].rx_buf = buf;
	t[1].len = count;
	spi_message_add_tail(&t[1], &m);

	mutex_lock(&at25->lock);

	/* Read it all at once.
	*
	* REVISIT that's potentially a problem with large chips, if
	* other devices on the bus need to be accessed regularly or
	* this chip is clocked very slowly
	*/
	status = spi_sync(at25->spi, &m);
	dev_dbg(&at25->spi->dev, "read %zu bytes at %d --> %zd\n",
	count, offset, status);

	mutex_unlock(&at25->lock);
	return status;
	}

	static int at25_ee_write(void priv, unsigned int off, void val, size_t count)
	{
	struct at25_data *at25 = priv;
	const char *buf = val;
	int status = 0;
	unsigned buf_size;
	u8 *bounce;

	if (unlikely(off >= at25->chip.byte_len))
	return -EFBIG;
	if ((off + count) > at25->chip.byte_len)
	count = at25->chip.byte_len - off;
	if (unlikely(!count))
	return -EINVAL;

	/* Temp buffer starts with command and address */
	buf_size = at25->chip.page_size;
	if (buf_size > io_limit)
	buf_size = io_limit;
	bounce = kmalloc(buf_size + at25->addrlen + 1, GFP_KERNEL);
	if (!bounce)
	return -ENOMEM;

	/* For write, rollover is within the page ... so we write at
	* most one page, then manually roll over to the next page.
	*/
	mutex_lock(&at25->lock);
	do {
	unsigned long timeout, retries;
	unsigned segment;
	unsigned offset = (unsigned) off;
	u8 *cp = bounce;
	int sr;
	u8 instr;

	*cp = AT25_WREN;
	status = spi_write(at25->spi, cp, 1);
	if (status < 0) {
	dev_dbg(&at25->spi->dev, "WREN --> %d\n", status);
	break;
	}

	instr = AT25_WRITE;
	if (at25->chip.flags & EE_INSTR_BIT3_IS_ADDR)
	if (offset >= (1U << (at25->addrlen * 8)))
	instr \|= AT25_INSTR_BIT3;
	*cp++ = instr;

	/* 8/16/24-bit address is written MSB first */
	switch (at25->addrlen) {
	default: /* case 3 */
	*cp++ = offset >> 16;
	fallthrough;
	case 2:
	*cp++ = offset >> 8;
	fallthrough;
	case 1:
	case 0: /* can't happen: for better codegen */
	*cp++ = offset >> 0;
	}

	/* Write as much of a page as we can */
	segment = buf_size - (offset % buf_size);
	if (segment > count)
	segment = count;
	memcpy(cp, buf, segment);
	status = spi_write(at25->spi, bounce,
	segment + at25->addrlen + 1);
	dev_dbg(&at25->spi->dev, "write %u bytes at %u --> %d\n",
	segment, offset, status);
	if (status < 0)
	break;

	/* REVISIT this should detect (or prevent) failed writes
	* to readonly sections of the EEPROM...
	*/

	/* Wait for non-busy status */
	timeout = jiffies + msecs_to_jiffies(EE_TIMEOUT);
	retries = 0;
	do {

	sr = spi_w8r8(at25->spi, AT25_RDSR);
	if (sr < 0 \|\| (sr & AT25_SR_nRDY)) {
	dev_dbg(&at25->spi->dev,
	"rdsr --> %d (%02x)\n", sr, sr);
	/* at HZ=100, this is sloooow */
	msleep(1);
	continue;
	}
	if (!(sr & AT25_SR_nRDY))
	break;
	} while (retries++ < 3 \|\| time_before_eq(jiffies, timeout));

	if ((sr < 0) \|\| (sr & AT25_SR_nRDY)) {
	dev_err(&at25->spi->dev,
	"write %u bytes offset %u, timeout after %u msecs\n",
	segment, offset,
	jiffies_to_msecs(jiffies -
	(timeout - EE_TIMEOUT)));
	status = -ETIMEDOUT;
	break;
	}

	off += segment;
	buf += segment;
	count -= segment;

	} while (count > 0);

	mutex_unlock(&at25->lock);

	kfree(bounce);
	return status;
	}

	/-------------------------------------------------------------------------/

	static int at25_fw_to_chip(struct device dev, struct spi_eeprom chip)
	{
	u32 val;

	memset(chip, 0, sizeof(*chip));
	strncpy(chip->name, "at25", sizeof(chip->name));

	if (device_property_read_u32(dev, "size", &val) == 0 \|\|
	device_property_read_u32(dev, "at25,byte-len", &val) == 0) {
	chip->byte_len = val;
	} else {
	dev_err(dev, "Error: missing \"size\" property\n");
	return -ENODEV;
	}

	if (device_property_read_u32(dev, "pagesize", &val) == 0 \|\|
	device_property_read_u32(dev, "at25,page-size", &val) == 0) {
	chip->page_size = val;
	} else {
	dev_err(dev, "Error: missing \"pagesize\" property\n");
	return -ENODEV;
	}

	if (device_property_read_u32(dev, "at25,addr-mode", &val) == 0) {
	chip->flags = (u16)val;
	} else {
	if (device_property_read_u32(dev, "address-width", &val)) {
	dev_err(dev,
	"Error: missing \"address-width\" property\n");
	return -ENODEV;
	}
	switch (val) {
	case 9:
	chip->flags \|= EE_INSTR_BIT3_IS_ADDR;
	fallthrough;
	case 8:
	chip->flags \|= EE_ADDR1;
	break;
	case 16:
	chip->flags \|= EE_ADDR2;
	break;
	case 24:
	chip->flags \|= EE_ADDR3;
	break;
	default:
	dev_err(dev,
	"Error: bad \"address-width\" property: %u\n",
	val);
	return -ENODEV;
	}
	if (device_property_present(dev, "read-only"))
	chip->flags \|= EE_READONLY;
	}
	return 0;
	}

	static int at25_probe(struct spi_device *spi)
	{
	struct at25_data *at25 = NULL;
	struct spi_eeprom chip;
	int err;
	int sr;
	int addrlen;

	/* Chip description */
	if (!spi->dev.platform_data) {
	err = at25_fw_to_chip(&spi->dev, &chip);
	if (err)
	return err;
	} else
	chip = (struct spi_eeprom )spi->dev.platform_data;

	/* For now we only support 8/16/24 bit addressing */
	if (chip.flags & EE_ADDR1)
	addrlen = 1;
	else if (chip.flags & EE_ADDR2)
	addrlen = 2;
	else if (chip.flags & EE_ADDR3)
	addrlen = 3;
	else {
	dev_dbg(&spi->dev, "unsupported address type\n");
	return -EINVAL;
	}

	/* Ping the chip ... the status register is pretty portable,
	* unlike probing manufacturer IDs. We do expect that system
	* firmware didn't write it in the past few milliseconds!
	*/
	sr = spi_w8r8(spi, AT25_RDSR);
	if (sr < 0 \|\| sr & AT25_SR_nRDY) {
	dev_dbg(&spi->dev, "rdsr --> %d (%02x)\n", sr, sr);
	return -ENXIO;
	}

	at25 = devm_kzalloc(&spi->dev, sizeof(struct at25_data), GFP_KERNEL);
	if (!at25)
	return -ENOMEM;

	mutex_init(&at25->lock);
	at25->chip = chip;
	at25->spi = spi;
	spi_set_drvdata(spi, at25);
	at25->addrlen = addrlen;

	at25->nvmem_config.type = NVMEM_TYPE_EEPROM;
	at25->nvmem_config.name = dev_name(&spi->dev);
	at25->nvmem_config.dev = &spi->dev;
	at25->nvmem_config.read_only = chip.flags & EE_READONLY;
	at25->nvmem_config.root_only = true;
	at25->nvmem_config.owner = THIS_MODULE;
	at25->nvmem_config.compat = true;
	at25->nvmem_config.base_dev = &spi->dev;
	at25->nvmem_config.reg_read = at25_ee_read;
	at25->nvmem_config.reg_write = at25_ee_write;
	at25->nvmem_config.priv = at25;
	at25->nvmem_config.stride = 1;
	at25->nvmem_config.word_size = 1;
	at25->nvmem_config.size = chip.byte_len;

	at25->nvmem = devm_nvmem_register(&spi->dev, &at25->nvmem_config);
	if (IS_ERR(at25->nvmem))
	return PTR_ERR(at25->nvmem);

	dev_info(&spi->dev, "%d %s %s eeprom%s, pagesize %u\n",
	(chip.byte_len < 1024) ? chip.byte_len : (chip.byte_len / 1024),
	(chip.byte_len < 1024) ? "Byte" : "KByte",
	at25->chip.name,
	(chip.flags & EE_READONLY) ? " (readonly)" : "",
	at25->chip.page_size);
	return 0;
	}

	/-------------------------------------------------------------------------/

	static const struct of_device_id at25_of_match[] = {
	{ .compatible = "atmel,at25", },
	{ }
	};
	MODULE_DEVICE_TABLE(of, at25_of_match);

	static struct spi_driver at25_driver = {
	.driver = {
	.name = "at25",
	.of_match_table = at25_of_match,
	},
	.probe = at25_probe,
	};

	module_spi_driver(at25_driver);

	MODULE_DESCRIPTION("Driver for most SPI EEPROMs");
	MODULE_AUTHOR("David Brownell");
	MODULE_LICENSE("GPL");
	MODULE_ALIAS("spi:at25");