drivers/staging/iio/adc/ad7816.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0+
 /*
  * AD7816 digital temperature sensor driver supporting AD7816/7/8
  *
  * Copyright 2010 Analog Devices Inc.
  */

 #include <linux/interrupt.h>
 #include <linux/gpio/consumer.h>
 #include <linux/device.h>
 #include <linux/kernel.h>
 #include <linux/slab.h>
 #include <linux/sysfs.h>
 #include <linux/list.h>
 #include <linux/spi/spi.h>
 #include <linux/module.h>

 #include <linux/iio/iio.h>
 #include <linux/iio/sysfs.h>
 #include <linux/iio/events.h>

 /*
  * AD7816 config masks
  */
 #define AD7816_FULL			0x1
 #define AD7816_PD			0x2
 #define AD7816_CS_MASK			0x7
 #define AD7816_CS_MAX			0x4

 /*
  * AD7816 temperature masks
  */
 #define AD7816_VALUE_OFFSET		6
 #define AD7816_BOUND_VALUE_BASE		0x8
 #define AD7816_BOUND_VALUE_MIN		-95
 #define AD7816_BOUND_VALUE_MAX		152
 #define AD7816_TEMP_FLOAT_OFFSET	2
 #define AD7816_TEMP_FLOAT_MASK		0x3

 /*
  * struct ad7816_chip_info - chip specific information
  */

 struct ad7816_chip_info {
 	kernel_ulong_t id;
 	struct spi_device *spi_dev;
 	struct gpio_desc *rdwr_pin;
 	struct gpio_desc *convert_pin;
 	struct gpio_desc *busy_pin;
 	u8  oti_data[AD7816_CS_MAX + 1];
 	u8  channel_id;	/* 0 always be temperature */
 	u8  mode;
 };

 enum ad7816_type {
 	ID_AD7816,
 	ID_AD7817,
 	ID_AD7818,
 };

 /*
  * ad7816 data access by SPI
  */
 static int ad7816_spi_read(struct ad7816_chip_info *chip, u16 *data)
 {
 	struct spi_device *spi_dev = chip->spi_dev;
 	int ret;
 	__be16 buf;

 	gpiod_set_value(chip->rdwr_pin, 1);
 	gpiod_set_value(chip->rdwr_pin, 0);
 	ret = spi_write(spi_dev, &chip->channel_id, sizeof(chip->channel_id));
 	if (ret < 0) {
 		dev_err(&spi_dev->dev, "SPI channel setting error\n");
 		return ret;
 	}
 	gpiod_set_value(chip->rdwr_pin, 1);

 	if (chip->mode == AD7816_PD) { /* operating mode 2 */
 		gpiod_set_value(chip->convert_pin, 1);
 		gpiod_set_value(chip->convert_pin, 0);
 	} else { /* operating mode 1 */
 		gpiod_set_value(chip->convert_pin, 0);
 		gpiod_set_value(chip->convert_pin, 1);
 	}

 	if (chip->id == ID_AD7816 || chip->id == ID_AD7817) {
 		while (gpiod_get_value(chip->busy_pin))
 			cpu_relax();
 	}

 	gpiod_set_value(chip->rdwr_pin, 0);
 	gpiod_set_value(chip->rdwr_pin, 1);
 	ret = spi_read(spi_dev, &buf, sizeof(*data));
 	if (ret < 0) {
 		dev_err(&spi_dev->dev, "SPI data read error\n");
 		return ret;
 	}

 	*data = be16_to_cpu(buf);

 	return ret;
 }

 static int ad7816_spi_write(struct ad7816_chip_info *chip, u8 data)
 {
 	struct spi_device *spi_dev = chip->spi_dev;
 	int ret;

 	gpiod_set_value(chip->rdwr_pin, 1);
 	gpiod_set_value(chip->rdwr_pin, 0);
 	ret = spi_write(spi_dev, &data, sizeof(data));
 	if (ret < 0)
 		dev_err(&spi_dev->dev, "SPI oti data write error\n");

 	return ret;
 }

 static ssize_t ad7816_show_mode(struct device *dev,
 				struct device_attribute *attr,
 				char *buf)
 {
 	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
 	struct ad7816_chip_info *chip = iio_priv(indio_dev);

 	if (chip->mode)
 		return sprintf(buf, "power-save\n");
 	return sprintf(buf, "full\n");
 }

 static ssize_t ad7816_store_mode(struct device *dev,
 				 struct device_attribute *attr,
 				 const char *buf,
 				 size_t len)
 {
 	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
 	struct ad7816_chip_info *chip = iio_priv(indio_dev);

 	if (strcmp(buf, "full")) {
 		gpiod_set_value(chip->rdwr_pin, 1);
 		chip->mode = AD7816_FULL;
 	} else {
 		gpiod_set_value(chip->rdwr_pin, 0);
 		chip->mode = AD7816_PD;
 	}

 	return len;
 }

 static IIO_DEVICE_ATTR(mode, 0644,
 		ad7816_show_mode,
 		ad7816_store_mode,
 		0);

 static ssize_t ad7816_show_available_modes(struct device *dev,
 					   struct device_attribute *attr,
 					   char *buf)
 {
 	return sprintf(buf, "full\npower-save\n");
 }

 static IIO_DEVICE_ATTR(available_modes, 0444, ad7816_show_available_modes,
 			NULL, 0);

 static ssize_t ad7816_show_channel(struct device *dev,
 				   struct device_attribute *attr,
 				   char *buf)
 {
 	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
 	struct ad7816_chip_info *chip = iio_priv(indio_dev);

 	return sprintf(buf, "%d\n", chip->channel_id);
 }

 static ssize_t ad7816_store_channel(struct device *dev,
 				    struct device_attribute *attr,
 				    const char *buf,
 				    size_t len)
 {
 	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
 	struct ad7816_chip_info *chip = iio_priv(indio_dev);
 	unsigned long data;
 	int ret;

 	ret = kstrtoul(buf, 10, &data);
 	if (ret)
 		return ret;

 	if (data > AD7816_CS_MAX && data != AD7816_CS_MASK) {
 		dev_err(&chip->spi_dev->dev, "Invalid channel id %lu for %s.\n",
 			data, indio_dev->name);
 		return -EINVAL;
 	} else if (strcmp(indio_dev->name, "ad7818") == 0 && data > 1) {
 		dev_err(&chip->spi_dev->dev,
 			"Invalid channel id %lu for ad7818.\n", data);
 		return -EINVAL;
 	} else if (strcmp(indio_dev->name, "ad7816") == 0 && data > 0) {
 		dev_err(&chip->spi_dev->dev,
 			"Invalid channel id %lu for ad7816.\n", data);
 		return -EINVAL;
 	}

 	chip->channel_id = data;

 	return len;
 }

 static IIO_DEVICE_ATTR(channel, 0644,
 		ad7816_show_channel,
 		ad7816_store_channel,
 		0);

 static ssize_t ad7816_show_value(struct device *dev,
 				 struct device_attribute *attr,
 				 char *buf)
 {
 	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
 	struct ad7816_chip_info *chip = iio_priv(indio_dev);
 	u16 data;
 	s8 value;
 	int ret;

 	ret = ad7816_spi_read(chip, &data);
 	if (ret)
 		return -EIO;

 	data >>= AD7816_VALUE_OFFSET;

 	if (chip->channel_id == 0) {
 		value = (s8)((data >> AD7816_TEMP_FLOAT_OFFSET) - 103);
 		data &= AD7816_TEMP_FLOAT_MASK;
 		if (value < 0)
 			data = BIT(AD7816_TEMP_FLOAT_OFFSET) - data;
 		return sprintf(buf, "%d.%.2d\n", value, data * 25);
 	}
 	return sprintf(buf, "%u\n", data);
 }

 static IIO_DEVICE_ATTR(value, 0444, ad7816_show_value, NULL, 0);

 static struct attribute *ad7816_attributes[] = {
 	&iio_dev_attr_available_modes.dev_attr.attr,
 	&iio_dev_attr_mode.dev_attr.attr,
 	&iio_dev_attr_channel.dev_attr.attr,
 	&iio_dev_attr_value.dev_attr.attr,
 	NULL,
 };

 static const struct attribute_group ad7816_attribute_group = {
 	.attrs = ad7816_attributes,
 };

 /*
  * temperature bound events
  */

 #define IIO_EVENT_CODE_AD7816_OTI IIO_UNMOD_EVENT_CODE(IIO_TEMP,	\
 						       0,		\
 						       IIO_EV_TYPE_THRESH, \
 						       IIO_EV_DIR_FALLING)

 static irqreturn_t ad7816_event_handler(int irq, void *private)
 {
 	iio_push_event(private, IIO_EVENT_CODE_AD7816_OTI,
 		       iio_get_time_ns(private));
 	return IRQ_HANDLED;
 }

 static ssize_t ad7816_show_oti(struct device *dev,
 			       struct device_attribute *attr,
 			       char *buf)
 {
 	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
 	struct ad7816_chip_info *chip = iio_priv(indio_dev);
 	int value;

 	if (chip->channel_id > AD7816_CS_MAX) {
 		dev_err(dev, "Invalid oti channel id %d.\n", chip->channel_id);
 		return -EINVAL;
 	} else if (chip->channel_id == 0) {
 		value = AD7816_BOUND_VALUE_MIN +
 			(chip->oti_data[chip->channel_id] -
 			AD7816_BOUND_VALUE_BASE);
 		return sprintf(buf, "%d\n", value);
 	}
 	return sprintf(buf, "%u\n", chip->oti_data[chip->channel_id]);
 }

 static inline ssize_t ad7816_set_oti(struct device *dev,
 				     struct device_attribute *attr,
 				     const char *buf,
 				     size_t len)
 {
 	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
 	struct ad7816_chip_info *chip = iio_priv(indio_dev);
 	long value;
 	u8 data;
 	int ret;

 	ret = kstrtol(buf, 10, &value);
 	if (ret)
 		return ret;

 	if (chip->channel_id > AD7816_CS_MAX) {
 		dev_err(dev, "Invalid oti channel id %d.\n", chip->channel_id);
 		return -EINVAL;
 	} else if (chip->channel_id == 0) {
 		if (value < AD7816_BOUND_VALUE_MIN ||
 		    value > AD7816_BOUND_VALUE_MAX)
 			return -EINVAL;

 		data = (u8)(value - AD7816_BOUND_VALUE_MIN +
 			AD7816_BOUND_VALUE_BASE);
 	} else {
 		if (value < AD7816_BOUND_VALUE_BASE || value > 255)
 			return -EINVAL;

 		data = (u8)value;
 	}

 	ret = ad7816_spi_write(chip, data);
 	if (ret)
 		return -EIO;

 	chip->oti_data[chip->channel_id] = data;

 	return len;
 }

 static IIO_DEVICE_ATTR(oti, 0644,
 		       ad7816_show_oti, ad7816_set_oti, 0);

 static struct attribute *ad7816_event_attributes[] = {
 	&iio_dev_attr_oti.dev_attr.attr,
 	NULL,
 };

 static const struct attribute_group ad7816_event_attribute_group = {
 	.attrs = ad7816_event_attributes,
 	.name = "events",
 };

 static const struct iio_info ad7816_info = {
 	.attrs = &ad7816_attribute_group,
 	.event_attrs = &ad7816_event_attribute_group,
 };

 /*
  * device probe and remove
  */

 static int ad7816_probe(struct spi_device *spi_dev)
 {
 	struct ad7816_chip_info *chip;
 	struct iio_dev *indio_dev;
 	int i, ret;

 	indio_dev = devm_iio_device_alloc(&spi_dev->dev, sizeof(*chip));
 	if (!indio_dev)
 		return -ENOMEM;
 	chip = iio_priv(indio_dev);
 	/* this is only used for device removal purposes */
 	dev_set_drvdata(&spi_dev->dev, indio_dev);

 	chip->spi_dev = spi_dev;
 	for (i = 0; i <= AD7816_CS_MAX; i++)
 		chip->oti_data[i] = 203;

 	chip->id = spi_get_device_id(spi_dev)->driver_data;
 	chip->rdwr_pin = devm_gpiod_get(&spi_dev->dev, "rdwr", GPIOD_OUT_HIGH);
 	if (IS_ERR(chip->rdwr_pin)) {
 		ret = PTR_ERR(chip->rdwr_pin);
 		dev_err(&spi_dev->dev, "Failed to request rdwr GPIO: %d\n",
 			ret);
 		return ret;
 	}
 	chip->convert_pin = devm_gpiod_get(&spi_dev->dev, "convert",
 					   GPIOD_OUT_HIGH);
 	if (IS_ERR(chip->convert_pin)) {
 		ret = PTR_ERR(chip->convert_pin);
 		dev_err(&spi_dev->dev, "Failed to request convert GPIO: %d\n",
 			ret);
 		return ret;
 	}
 	if (chip->id == ID_AD7816 || chip->id == ID_AD7817) {
 		chip->busy_pin = devm_gpiod_get(&spi_dev->dev, "busy",
 						GPIOD_IN);
 		if (IS_ERR(chip->busy_pin)) {
 			ret = PTR_ERR(chip->busy_pin);
 			dev_err(&spi_dev->dev, "Failed to request busy GPIO: %d\n",
 				ret);
 			return ret;
 		}
 	}

 	indio_dev->name = spi_get_device_id(spi_dev)->name;
 	indio_dev->info = &ad7816_info;
 	indio_dev->modes = INDIO_DIRECT_MODE;

 	if (spi_dev->irq) {
 		/* Only low trigger is supported in ad7816/7/8 */
 		ret = devm_request_threaded_irq(&spi_dev->dev, spi_dev->irq,
 						NULL,
 						&ad7816_event_handler,
 						IRQF_TRIGGER_LOW | IRQF_ONESHOT,
 						indio_dev->name,
 						indio_dev);
 		if (ret)
 			return ret;
 	}

 	ret = devm_iio_device_register(&spi_dev->dev, indio_dev);
 	if (ret)
 		return ret;

 	dev_info(&spi_dev->dev, "%s temperature sensor and ADC registered.\n",
 		 indio_dev->name);

 	return 0;
 }

 static const struct of_device_id ad7816_of_match[] = {
 	{ .compatible = "adi,ad7816", },
 	{ .compatible = "adi,ad7817", },
 	{ .compatible = "adi,ad7818", },
 	{ }
 };
 MODULE_DEVICE_TABLE(of, ad7816_of_match);

 static const struct spi_device_id ad7816_id[] = {
 	{ "ad7816", ID_AD7816 },
 	{ "ad7817", ID_AD7817 },
 	{ "ad7818", ID_AD7818 },
 	{}
 };

 MODULE_DEVICE_TABLE(spi, ad7816_id);

 static struct spi_driver ad7816_driver = {
 	.driver = {
 		.name = "ad7816",
 		.of_match_table = ad7816_of_match,
 	},
 	.probe = ad7816_probe,
 	.id_table = ad7816_id,
 };
 module_spi_driver(ad7816_driver);

 MODULE_AUTHOR("Sonic Zhang <sonic.zhang@analog.com>");
 MODULE_DESCRIPTION("Analog Devices AD7816/7/8 digital temperature sensor driver");
 MODULE_LICENSE("GPL v2");
	// SPDX-License-Identifier: GPL-2.0+
	/*
	* AD7816 digital temperature sensor driver supporting AD7816/7/8
	*
	* Copyright 2010 Analog Devices Inc.
	*/

	#include <linux/interrupt.h>
	#include <linux/gpio/consumer.h>
	#include <linux/device.h>
	#include <linux/kernel.h>
	#include <linux/slab.h>
	#include <linux/sysfs.h>
	#include <linux/list.h>
	#include <linux/spi/spi.h>
	#include <linux/module.h>

	#include <linux/iio/iio.h>
	#include <linux/iio/sysfs.h>
	#include <linux/iio/events.h>

	/*
	* AD7816 config masks
	*/
	#define AD7816_FULL 0x1
	#define AD7816_PD 0x2
	#define AD7816_CS_MASK 0x7
	#define AD7816_CS_MAX 0x4

	/*
	* AD7816 temperature masks
	*/
	#define AD7816_VALUE_OFFSET 6
	#define AD7816_BOUND_VALUE_BASE 0x8
	#define AD7816_BOUND_VALUE_MIN -95
	#define AD7816_BOUND_VALUE_MAX 152
	#define AD7816_TEMP_FLOAT_OFFSET 2
	#define AD7816_TEMP_FLOAT_MASK 0x3

	/*
	* struct ad7816_chip_info - chip specific information
	*/

	struct ad7816_chip_info {
	kernel_ulong_t id;
	struct spi_device *spi_dev;
	struct gpio_desc *rdwr_pin;
	struct gpio_desc *convert_pin;
	struct gpio_desc *busy_pin;
	u8 oti_data[AD7816_CS_MAX + 1];
	u8 channel_id; /* 0 always be temperature */
	u8 mode;
	};

	enum ad7816_type {
	ID_AD7816,
	ID_AD7817,
	ID_AD7818,
	};

	/*
	* ad7816 data access by SPI
	*/
	static int ad7816_spi_read(struct ad7816_chip_info chip, u16 data)
	{
	struct spi_device *spi_dev = chip->spi_dev;
	int ret;
	__be16 buf;

	gpiod_set_value(chip->rdwr_pin, 1);
	gpiod_set_value(chip->rdwr_pin, 0);
	ret = spi_write(spi_dev, &chip->channel_id, sizeof(chip->channel_id));
	if (ret < 0) {
	dev_err(&spi_dev->dev, "SPI channel setting error\n");
	return ret;
	}
	gpiod_set_value(chip->rdwr_pin, 1);

	if (chip->mode == AD7816_PD) { /* operating mode 2 */
	gpiod_set_value(chip->convert_pin, 1);
	gpiod_set_value(chip->convert_pin, 0);
	} else { /* operating mode 1 */
	gpiod_set_value(chip->convert_pin, 0);
	gpiod_set_value(chip->convert_pin, 1);
	}

	if (chip->id == ID_AD7816 \|\| chip->id == ID_AD7817) {
	while (gpiod_get_value(chip->busy_pin))
	cpu_relax();
	}

	gpiod_set_value(chip->rdwr_pin, 0);
	gpiod_set_value(chip->rdwr_pin, 1);
	ret = spi_read(spi_dev, &buf, sizeof(*data));
	if (ret < 0) {
	dev_err(&spi_dev->dev, "SPI data read error\n");
	return ret;
	}

	*data = be16_to_cpu(buf);

	return ret;
	}

	static int ad7816_spi_write(struct ad7816_chip_info *chip, u8 data)
	{
	struct spi_device *spi_dev = chip->spi_dev;
	int ret;

	gpiod_set_value(chip->rdwr_pin, 1);
	gpiod_set_value(chip->rdwr_pin, 0);
	ret = spi_write(spi_dev, &data, sizeof(data));
	if (ret < 0)
	dev_err(&spi_dev->dev, "SPI oti data write error\n");

	return ret;
	}

	static ssize_t ad7816_show_mode(struct device *dev,
	struct device_attribute *attr,
	char *buf)
	{
	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
	struct ad7816_chip_info *chip = iio_priv(indio_dev);

	if (chip->mode)
	return sprintf(buf, "power-save\n");
	return sprintf(buf, "full\n");
	}

	static ssize_t ad7816_store_mode(struct device *dev,
	struct device_attribute *attr,
	const char *buf,
	size_t len)
	{
	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
	struct ad7816_chip_info *chip = iio_priv(indio_dev);

	if (strcmp(buf, "full")) {
	gpiod_set_value(chip->rdwr_pin, 1);
	chip->mode = AD7816_FULL;
	} else {
	gpiod_set_value(chip->rdwr_pin, 0);
	chip->mode = AD7816_PD;
	}

	return len;
	}

	static IIO_DEVICE_ATTR(mode, 0644,
	ad7816_show_mode,
	ad7816_store_mode,
	0);

	static ssize_t ad7816_show_available_modes(struct device *dev,
	struct device_attribute *attr,
	char *buf)
	{
	return sprintf(buf, "full\npower-save\n");
	}

	static IIO_DEVICE_ATTR(available_modes, 0444, ad7816_show_available_modes,
	NULL, 0);

	static ssize_t ad7816_show_channel(struct device *dev,
	struct device_attribute *attr,
	char *buf)
	{
	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
	struct ad7816_chip_info *chip = iio_priv(indio_dev);

	return sprintf(buf, "%d\n", chip->channel_id);
	}

	static ssize_t ad7816_store_channel(struct device *dev,
	struct device_attribute *attr,
	const char *buf,
	size_t len)
	{
	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
	struct ad7816_chip_info *chip = iio_priv(indio_dev);
	unsigned long data;
	int ret;

	ret = kstrtoul(buf, 10, &data);
	if (ret)
	return ret;

	if (data > AD7816_CS_MAX && data != AD7816_CS_MASK) {
	dev_err(&chip->spi_dev->dev, "Invalid channel id %lu for %s.\n",
	data, indio_dev->name);
	return -EINVAL;
	} else if (strcmp(indio_dev->name, "ad7818") == 0 && data > 1) {
	dev_err(&chip->spi_dev->dev,
	"Invalid channel id %lu for ad7818.\n", data);
	return -EINVAL;
	} else if (strcmp(indio_dev->name, "ad7816") == 0 && data > 0) {
	dev_err(&chip->spi_dev->dev,
	"Invalid channel id %lu for ad7816.\n", data);
	return -EINVAL;
	}

	chip->channel_id = data;

	return len;
	}

	static IIO_DEVICE_ATTR(channel, 0644,
	ad7816_show_channel,
	ad7816_store_channel,
	0);

	static ssize_t ad7816_show_value(struct device *dev,
	struct device_attribute *attr,
	char *buf)
	{
	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
	struct ad7816_chip_info *chip = iio_priv(indio_dev);
	u16 data;
	s8 value;
	int ret;

	ret = ad7816_spi_read(chip, &data);
	if (ret)
	return -EIO;

	data >>= AD7816_VALUE_OFFSET;

	if (chip->channel_id == 0) {
	value = (s8)((data >> AD7816_TEMP_FLOAT_OFFSET) - 103);
	data &= AD7816_TEMP_FLOAT_MASK;
	if (value < 0)
	data = BIT(AD7816_TEMP_FLOAT_OFFSET) - data;
	return sprintf(buf, "%d.%.2d\n", value, data * 25);
	}
	return sprintf(buf, "%u\n", data);
	}

	static IIO_DEVICE_ATTR(value, 0444, ad7816_show_value, NULL, 0);

	static struct attribute *ad7816_attributes[] = {
	&iio_dev_attr_available_modes.dev_attr.attr,
	&iio_dev_attr_mode.dev_attr.attr,
	&iio_dev_attr_channel.dev_attr.attr,
	&iio_dev_attr_value.dev_attr.attr,
	NULL,
	};

	static const struct attribute_group ad7816_attribute_group = {
	.attrs = ad7816_attributes,
	};

	/*
	* temperature bound events
	*/

	#define IIO_EVENT_CODE_AD7816_OTI IIO_UNMOD_EVENT_CODE(IIO_TEMP, \
	0, \
	IIO_EV_TYPE_THRESH, \
	IIO_EV_DIR_FALLING)

	static irqreturn_t ad7816_event_handler(int irq, void *private)
	{
	iio_push_event(private, IIO_EVENT_CODE_AD7816_OTI,
	iio_get_time_ns(private));
	return IRQ_HANDLED;
	}

	static ssize_t ad7816_show_oti(struct device *dev,
	struct device_attribute *attr,
	char *buf)
	{
	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
	struct ad7816_chip_info *chip = iio_priv(indio_dev);
	int value;

	if (chip->channel_id > AD7816_CS_MAX) {
	dev_err(dev, "Invalid oti channel id %d.\n", chip->channel_id);
	return -EINVAL;
	} else if (chip->channel_id == 0) {
	value = AD7816_BOUND_VALUE_MIN +
	(chip->oti_data[chip->channel_id] -
	AD7816_BOUND_VALUE_BASE);
	return sprintf(buf, "%d\n", value);
	}
	return sprintf(buf, "%u\n", chip->oti_data[chip->channel_id]);
	}

	static inline ssize_t ad7816_set_oti(struct device *dev,
	struct device_attribute *attr,
	const char *buf,
	size_t len)
	{
	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
	struct ad7816_chip_info *chip = iio_priv(indio_dev);
	long value;
	u8 data;
	int ret;

	ret = kstrtol(buf, 10, &value);
	if (ret)
	return ret;

	if (chip->channel_id > AD7816_CS_MAX) {
	dev_err(dev, "Invalid oti channel id %d.\n", chip->channel_id);
	return -EINVAL;
	} else if (chip->channel_id == 0) {
	if (value < AD7816_BOUND_VALUE_MIN \|\|
	value > AD7816_BOUND_VALUE_MAX)
	return -EINVAL;

	data = (u8)(value - AD7816_BOUND_VALUE_MIN +
	AD7816_BOUND_VALUE_BASE);
	} else {
	if (value < AD7816_BOUND_VALUE_BASE \|\| value > 255)
	return -EINVAL;

	data = (u8)value;
	}

	ret = ad7816_spi_write(chip, data);
	if (ret)
	return -EIO;

	chip->oti_data[chip->channel_id] = data;

	return len;
	}

	static IIO_DEVICE_ATTR(oti, 0644,
	ad7816_show_oti, ad7816_set_oti, 0);

	static struct attribute *ad7816_event_attributes[] = {
	&iio_dev_attr_oti.dev_attr.attr,
	NULL,
	};

	static const struct attribute_group ad7816_event_attribute_group = {
	.attrs = ad7816_event_attributes,
	.name = "events",
	};

	static const struct iio_info ad7816_info = {
	.attrs = &ad7816_attribute_group,
	.event_attrs = &ad7816_event_attribute_group,
	};

	/*
	* device probe and remove
	*/

	static int ad7816_probe(struct spi_device *spi_dev)
	{
	struct ad7816_chip_info *chip;
	struct iio_dev *indio_dev;
	int i, ret;

	indio_dev = devm_iio_device_alloc(&spi_dev->dev, sizeof(*chip));
	if (!indio_dev)
	return -ENOMEM;
	chip = iio_priv(indio_dev);
	/* this is only used for device removal purposes */
	dev_set_drvdata(&spi_dev->dev, indio_dev);

	chip->spi_dev = spi_dev;
	for (i = 0; i <= AD7816_CS_MAX; i++)
	chip->oti_data[i] = 203;

	chip->id = spi_get_device_id(spi_dev)->driver_data;
	chip->rdwr_pin = devm_gpiod_get(&spi_dev->dev, "rdwr", GPIOD_OUT_HIGH);
	if (IS_ERR(chip->rdwr_pin)) {
	ret = PTR_ERR(chip->rdwr_pin);
	dev_err(&spi_dev->dev, "Failed to request rdwr GPIO: %d\n",
	ret);
	return ret;
	}
	chip->convert_pin = devm_gpiod_get(&spi_dev->dev, "convert",
	GPIOD_OUT_HIGH);
	if (IS_ERR(chip->convert_pin)) {
	ret = PTR_ERR(chip->convert_pin);
	dev_err(&spi_dev->dev, "Failed to request convert GPIO: %d\n",
	ret);
	return ret;
	}
	if (chip->id == ID_AD7816 \|\| chip->id == ID_AD7817) {
	chip->busy_pin = devm_gpiod_get(&spi_dev->dev, "busy",
	GPIOD_IN);
	if (IS_ERR(chip->busy_pin)) {
	ret = PTR_ERR(chip->busy_pin);
	dev_err(&spi_dev->dev, "Failed to request busy GPIO: %d\n",
	ret);
	return ret;
	}
	}

	indio_dev->name = spi_get_device_id(spi_dev)->name;
	indio_dev->info = &ad7816_info;
	indio_dev->modes = INDIO_DIRECT_MODE;

	if (spi_dev->irq) {
	/* Only low trigger is supported in ad7816/7/8 */
	ret = devm_request_threaded_irq(&spi_dev->dev, spi_dev->irq,
	NULL,
	&ad7816_event_handler,
	IRQF_TRIGGER_LOW \| IRQF_ONESHOT,
	indio_dev->name,
	indio_dev);
	if (ret)
	return ret;
	}

	ret = devm_iio_device_register(&spi_dev->dev, indio_dev);
	if (ret)
	return ret;

	dev_info(&spi_dev->dev, "%s temperature sensor and ADC registered.\n",
	indio_dev->name);

	return 0;
	}

	static const struct of_device_id ad7816_of_match[] = {
	{ .compatible = "adi,ad7816", },
	{ .compatible = "adi,ad7817", },
	{ .compatible = "adi,ad7818", },
	{ }
	};
	MODULE_DEVICE_TABLE(of, ad7816_of_match);

	static const struct spi_device_id ad7816_id[] = {
	{ "ad7816", ID_AD7816 },
	{ "ad7817", ID_AD7817 },
	{ "ad7818", ID_AD7818 },
	{}
	};

	MODULE_DEVICE_TABLE(spi, ad7816_id);

	static struct spi_driver ad7816_driver = {
	.driver = {
	.name = "ad7816",
	.of_match_table = ad7816_of_match,
	},
	.probe = ad7816_probe,
	.id_table = ad7816_id,
	};
	module_spi_driver(ad7816_driver);

	MODULE_AUTHOR("Sonic Zhang <sonic.zhang@analog.com>");
	MODULE_DESCRIPTION("Analog Devices AD7816/7/8 digital temperature sensor driver");
	MODULE_LICENSE("GPL v2");