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

 /*
  * at25.c -- support most SPI EEPROMs, such as Atmel AT25 models
  *
  * Copyright (C) 2006 David Brownell
  *
  * 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; either version 2 of the License, or
  * (at your option) any later version.
  */

 #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/spi/spi.h>
 #include <linux/spi/eeprom.h>
 #include <linux/of.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!
  */

 struct at25_data {
 	struct spi_device	*spi;
 	struct memory_accessor	mem;
 	struct mutex		lock;
 	struct spi_eeprom	chip;
 	struct bin_attribute	bin;
 	unsigned		addrlen;
 };

 #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 ssize_t
 at25_ee_read(
 	struct at25_data	*at25,
 	char			*buf,
 	unsigned		offset,
 	size_t			count
 )
 {
 	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->bin.size))
 		return 0;
 	if ((offset + count) > at25->bin.size)
 		count = at25->bin.size - offset;
 	if (unlikely(!count))
 		return count;

 	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;
 	case 2:
 		*cp++ = offset >> 8;
 	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 %Zd bytes at %d --> %d\n",
 		count, offset, (int) status);

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

 static ssize_t
 at25_bin_read(struct file *filp, struct kobject *kobj,
 	      struct bin_attribute *bin_attr,
 	      char *buf, loff_t off, size_t count)
 {
 	struct device		*dev;
 	struct at25_data	*at25;

 	dev = container_of(kobj, struct device, kobj);
 	at25 = dev_get_drvdata(dev);

 	return at25_ee_read(at25, buf, off, count);
 }


 static ssize_t
 at25_ee_write(struct at25_data *at25, const char *buf, loff_t off,
 	      size_t count)
 {
 	ssize_t			status = 0;
 	unsigned		written = 0;
 	unsigned		buf_size;
 	u8			*bounce;

 	if (unlikely(off >= at25->bin.size))
 		return -EFBIG;
 	if ((off + count) > at25->bin.size)
 		count = at25->bin.size - off;
 	if (unlikely(!count))
 		return count;

 	/* 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",
 					(int) 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;
 		case 2:
 			*cp++ = offset >> 8;
 		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, (int) 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 %d bytes offset %d, "
 				"timeout after %u msecs\n",
 				segment, offset,
 				jiffies_to_msecs(jiffies -
 					(timeout - EE_TIMEOUT)));
 			status = -ETIMEDOUT;
 			break;
 		}

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

 	} while (count > 0);

 	mutex_unlock(&at25->lock);

 	kfree(bounce);
 	return written ? written : status;
 }

 static ssize_t
 at25_bin_write(struct file *filp, struct kobject *kobj,
 	       struct bin_attribute *bin_attr,
 	       char *buf, loff_t off, size_t count)
 {
 	struct device		*dev;
 	struct at25_data	*at25;

 	dev = container_of(kobj, struct device, kobj);
 	at25 = dev_get_drvdata(dev);

 	return at25_ee_write(at25, buf, off, count);
 }

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

 /* Let in-kernel code access the eeprom data. */

 static ssize_t at25_mem_read(struct memory_accessor *mem, char *buf,
 			 off_t offset, size_t count)
 {
 	struct at25_data *at25 = container_of(mem, struct at25_data, mem);

 	return at25_ee_read(at25, buf, offset, count);
 }

 static ssize_t at25_mem_write(struct memory_accessor *mem, const char *buf,
 			  off_t offset, size_t count)
 {
 	struct at25_data *at25 = container_of(mem, struct at25_data, mem);

 	return at25_ee_write(at25, buf, offset, count);
 }

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

 static int at25_np_to_chip(struct device *dev,
 			   struct device_node *np,
 			   struct spi_eeprom *chip)
 {
 	u32 val;

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

 	if (of_property_read_u32(np, "size", &val) == 0 ||
 	    of_property_read_u32(np, "at25,byte-len", &val) == 0) {
 		chip->byte_len = val;
 	} else {
 		dev_err(dev, "Error: missing \"size\" property\n");
 		return -ENODEV;
 	}

 	if (of_property_read_u32(np, "pagesize", &val) == 0 ||
 	    of_property_read_u32(np, "at25,page-size", &val) == 0) {
 		chip->page_size = (u16)val;
 	} else {
 		dev_err(dev, "Error: missing \"pagesize\" property\n");
 		return -ENODEV;
 	}

 	if (of_property_read_u32(np, "at25,addr-mode", &val) == 0) {
 		chip->flags = (u16)val;
 	} else {
 		if (of_property_read_u32(np, "address-width", &val)) {
 			dev_err(dev,
 				"Error: missing \"address-width\" property\n");
 			return -ENODEV;
 		}
 		switch (val) {
 		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 (of_find_property(np, "read-only", NULL))
 			chip->flags |= EE_READONLY;
 	}
 	return 0;
 }

 static int at25_probe(struct spi_device *spi)
 {
 	struct at25_data	*at25 = NULL;
 	struct spi_eeprom	chip;
 	struct device_node	*np = spi->dev.of_node;
 	int			err;
 	int			sr;
 	int			addrlen;

 	/* Chip description */
 	if (!spi->dev.platform_data) {
 		if (np) {
 			err = at25_np_to_chip(&spi->dev, np, &chip);
 			if (err)
 				return err;
 		} else {
 			dev_err(&spi->dev, "Error: no chip description\n");
 			return -ENODEV;
 		}
 	} 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_dev_get(spi);
 	spi_set_drvdata(spi, at25);
 	at25->addrlen = addrlen;

 	/* Export the EEPROM bytes through sysfs, since that's convenient.
 	 * And maybe to other kernel code; it might hold a board's Ethernet
 	 * address, or board-specific calibration data generated on the
 	 * manufacturing floor.
 	 *
 	 * Default to root-only access to the data; EEPROMs often hold data
 	 * that's sensitive for read and/or write, like ethernet addresses,
 	 * security codes, board-specific manufacturing calibrations, etc.
 	 */
 	sysfs_bin_attr_init(&at25->bin);
 	at25->bin.attr.name = "eeprom";
 	at25->bin.attr.mode = S_IRUSR;
 	at25->bin.read = at25_bin_read;
 	at25->mem.read = at25_mem_read;

 	at25->bin.size = at25->chip.byte_len;
 	if (!(chip.flags & EE_READONLY)) {
 		at25->bin.write = at25_bin_write;
 		at25->bin.attr.mode |= S_IWUSR;
 		at25->mem.write = at25_mem_write;
 	}

 	err = sysfs_create_bin_file(&spi->dev.kobj, &at25->bin);
 	if (err)
 		return err;

 	if (chip.setup)
 		chip.setup(&at25->mem, chip.context);

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

 static int at25_remove(struct spi_device *spi)
 {
 	struct at25_data	*at25;

 	at25 = spi_get_drvdata(spi);
 	sysfs_remove_bin_file(&spi->dev.kobj, &at25->bin);
 	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",
 		.owner		= THIS_MODULE,
 		.of_match_table = at25_of_match,
 	},
 	.probe		= at25_probe,
 	.remove		= at25_remove,
 };

 module_spi_driver(at25_driver);

 MODULE_DESCRIPTION("Driver for most SPI EEPROMs");
 MODULE_AUTHOR("David Brownell");
 MODULE_LICENSE("GPL");
 MODULE_ALIAS("spi:at25");
	/*
	* at25.c -- support most SPI EEPROMs, such as Atmel AT25 models
	*
	* Copyright (C) 2006 David Brownell
	*
	* 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; either version 2 of the License, or
	* (at your option) any later version.
	*/

	#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/spi/spi.h>
	#include <linux/spi/eeprom.h>
	#include <linux/of.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!
	*/

	struct at25_data {
	struct spi_device *spi;
	struct memory_accessor mem;
	struct mutex lock;
	struct spi_eeprom chip;
	struct bin_attribute bin;
	unsigned addrlen;
	};

	#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 ssize_t
	at25_ee_read(
	struct at25_data *at25,
	char *buf,
	unsigned offset,
	size_t count
	)
	{
	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->bin.size))
	return 0;
	if ((offset + count) > at25->bin.size)
	count = at25->bin.size - offset;
	if (unlikely(!count))
	return count;

	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;
	case 2:
	*cp++ = offset >> 8;
	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 %Zd bytes at %d --> %d\n",
	count, offset, (int) status);

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

	static ssize_t
	at25_bin_read(struct file filp, struct kobject kobj,
	struct bin_attribute *bin_attr,
	char *buf, loff_t off, size_t count)
	{
	struct device *dev;
	struct at25_data *at25;

	dev = container_of(kobj, struct device, kobj);
	at25 = dev_get_drvdata(dev);

	return at25_ee_read(at25, buf, off, count);
	}


	static ssize_t
	at25_ee_write(struct at25_data at25, const char buf, loff_t off,
	size_t count)
	{
	ssize_t status = 0;
	unsigned written = 0;
	unsigned buf_size;
	u8 *bounce;

	if (unlikely(off >= at25->bin.size))
	return -EFBIG;
	if ((off + count) > at25->bin.size)
	count = at25->bin.size - off;
	if (unlikely(!count))
	return count;

	/* 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",
	(int) 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;
	case 2:
	*cp++ = offset >> 8;
	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, (int) 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 %d bytes offset %d, "
	"timeout after %u msecs\n",
	segment, offset,
	jiffies_to_msecs(jiffies -
	(timeout - EE_TIMEOUT)));
	status = -ETIMEDOUT;
	break;
	}

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

	} while (count > 0);

	mutex_unlock(&at25->lock);

	kfree(bounce);
	return written ? written : status;
	}

	static ssize_t
	at25_bin_write(struct file filp, struct kobject kobj,
	struct bin_attribute *bin_attr,
	char *buf, loff_t off, size_t count)
	{
	struct device *dev;
	struct at25_data *at25;

	dev = container_of(kobj, struct device, kobj);
	at25 = dev_get_drvdata(dev);

	return at25_ee_write(at25, buf, off, count);
	}

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

	/* Let in-kernel code access the eeprom data. */

	static ssize_t at25_mem_read(struct memory_accessor mem, char buf,
	off_t offset, size_t count)
	{
	struct at25_data *at25 = container_of(mem, struct at25_data, mem);

	return at25_ee_read(at25, buf, offset, count);
	}

	static ssize_t at25_mem_write(struct memory_accessor mem, const char buf,
	off_t offset, size_t count)
	{
	struct at25_data *at25 = container_of(mem, struct at25_data, mem);

	return at25_ee_write(at25, buf, offset, count);
	}

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

	static int at25_np_to_chip(struct device *dev,
	struct device_node *np,
	struct spi_eeprom *chip)
	{
	u32 val;

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

	if (of_property_read_u32(np, "size", &val) == 0 \|\|
	of_property_read_u32(np, "at25,byte-len", &val) == 0) {
	chip->byte_len = val;
	} else {
	dev_err(dev, "Error: missing \"size\" property\n");
	return -ENODEV;
	}

	if (of_property_read_u32(np, "pagesize", &val) == 0 \|\|
	of_property_read_u32(np, "at25,page-size", &val) == 0) {
	chip->page_size = (u16)val;
	} else {
	dev_err(dev, "Error: missing \"pagesize\" property\n");
	return -ENODEV;
	}

	if (of_property_read_u32(np, "at25,addr-mode", &val) == 0) {
	chip->flags = (u16)val;
	} else {
	if (of_property_read_u32(np, "address-width", &val)) {
	dev_err(dev,
	"Error: missing \"address-width\" property\n");
	return -ENODEV;
	}
	switch (val) {
	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 (of_find_property(np, "read-only", NULL))
	chip->flags \|= EE_READONLY;
	}
	return 0;
	}

	static int at25_probe(struct spi_device *spi)
	{
	struct at25_data *at25 = NULL;
	struct spi_eeprom chip;
	struct device_node *np = spi->dev.of_node;
	int err;
	int sr;
	int addrlen;

	/* Chip description */
	if (!spi->dev.platform_data) {
	if (np) {
	err = at25_np_to_chip(&spi->dev, np, &chip);
	if (err)
	return err;
	} else {
	dev_err(&spi->dev, "Error: no chip description\n");
	return -ENODEV;
	}
	} 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_dev_get(spi);
	spi_set_drvdata(spi, at25);
	at25->addrlen = addrlen;

	/* Export the EEPROM bytes through sysfs, since that's convenient.
	* And maybe to other kernel code; it might hold a board's Ethernet
	* address, or board-specific calibration data generated on the
	* manufacturing floor.
	*
	* Default to root-only access to the data; EEPROMs often hold data
	* that's sensitive for read and/or write, like ethernet addresses,
	* security codes, board-specific manufacturing calibrations, etc.
	*/
	sysfs_bin_attr_init(&at25->bin);
	at25->bin.attr.name = "eeprom";
	at25->bin.attr.mode = S_IRUSR;
	at25->bin.read = at25_bin_read;
	at25->mem.read = at25_mem_read;

	at25->bin.size = at25->chip.byte_len;
	if (!(chip.flags & EE_READONLY)) {
	at25->bin.write = at25_bin_write;
	at25->bin.attr.mode \|= S_IWUSR;
	at25->mem.write = at25_mem_write;
	}

	err = sysfs_create_bin_file(&spi->dev.kobj, &at25->bin);
	if (err)
	return err;

	if (chip.setup)
	chip.setup(&at25->mem, chip.context);

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

	static int at25_remove(struct spi_device *spi)
	{
	struct at25_data *at25;

	at25 = spi_get_drvdata(spi);
	sysfs_remove_bin_file(&spi->dev.kobj, &at25->bin);
	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",
	.owner = THIS_MODULE,
	.of_match_table = at25_of_match,
	},
	.probe = at25_probe,
	.remove = at25_remove,
	};

	module_spi_driver(at25_driver);

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