drivers/hwmon/tmp108.c - linux - Git at Google

 /* Texas Instruments TMP108 SMBus temperature sensor driver
  *
  * Copyright (C) 2016 John Muir <john@jmuir.com>
  *
  * 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.
  *
  * 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 <linux/delay.h>
 #include <linux/device.h>
 #include <linux/err.h>
 #include <linux/hwmon.h>
 #include <linux/hwmon-sysfs.h>
 #include <linux/module.h>
 #include <linux/mutex.h>
 #include <linux/of.h>
 #include <linux/i2c.h>
 #include <linux/init.h>
 #include <linux/jiffies.h>
 #include <linux/regmap.h>
 #include <linux/slab.h>

 #define	DRIVER_NAME "tmp108"

 #define	TMP108_REG_TEMP		0x00
 #define	TMP108_REG_CONF		0x01
 #define	TMP108_REG_TLOW		0x02
 #define	TMP108_REG_THIGH	0x03

 #define TMP108_TEMP_MIN_MC	-50000 /* Minimum millicelcius. */
 #define TMP108_TEMP_MAX_MC	127937 /* Maximum millicelcius. */

 /* Configuration register bits.
  * Note: these bit definitions are byte swapped.
  */
 #define TMP108_CONF_M0		0x0100 /* Sensor mode. */
 #define TMP108_CONF_M1		0x0200
 #define TMP108_CONF_TM		0x0400 /* Thermostat mode. */
 #define TMP108_CONF_FL		0x0800 /* Watchdog flag - TLOW */
 #define TMP108_CONF_FH		0x1000 /* Watchdog flag - THIGH */
 #define TMP108_CONF_CR0		0x2000 /* Conversion rate. */
 #define TMP108_CONF_CR1		0x4000
 #define TMP108_CONF_ID		0x8000
 #define TMP108_CONF_HYS0	0x0010 /* Hysteresis. */
 #define TMP108_CONF_HYS1	0x0020
 #define TMP108_CONF_POL		0x0080 /* Polarity of alert. */

 /* Defaults set by the hardware upon reset. */
 #define TMP108_CONF_DEFAULTS		(TMP108_CONF_CR0 | TMP108_CONF_TM |\
 					 TMP108_CONF_HYS0 | TMP108_CONF_M1)
 /* These bits are read-only. */
 #define TMP108_CONF_READ_ONLY		(TMP108_CONF_FL | TMP108_CONF_FH |\
 					 TMP108_CONF_ID)

 #define TMP108_CONF_MODE_MASK		(TMP108_CONF_M0|TMP108_CONF_M1)
 #define TMP108_MODE_SHUTDOWN		0x0000
 #define TMP108_MODE_ONE_SHOT		TMP108_CONF_M0
 #define TMP108_MODE_CONTINUOUS		TMP108_CONF_M1		/* Default */
 					/* When M1 is set, M0 is ignored. */

 #define TMP108_CONF_CONVRATE_MASK	(TMP108_CONF_CR0|TMP108_CONF_CR1)
 #define TMP108_CONVRATE_0P25HZ		0x0000
 #define TMP108_CONVRATE_1HZ		TMP108_CONF_CR0		/* Default */
 #define TMP108_CONVRATE_4HZ		TMP108_CONF_CR1
 #define TMP108_CONVRATE_16HZ		(TMP108_CONF_CR0|TMP108_CONF_CR1)

 #define TMP108_CONF_HYSTERESIS_MASK	(TMP108_CONF_HYS0|TMP108_CONF_HYS1)
 #define TMP108_HYSTERESIS_0C		0x0000
 #define TMP108_HYSTERESIS_1C		TMP108_CONF_HYS0	/* Default */
 #define TMP108_HYSTERESIS_2C		TMP108_CONF_HYS1
 #define TMP108_HYSTERESIS_4C		(TMP108_CONF_HYS0|TMP108_CONF_HYS1)

 #define TMP108_CONVERSION_TIME_MS	30	/* in milli-seconds */

 struct tmp108 {
 	struct regmap *regmap;
 	u16 orig_config;
 	unsigned long ready_time;
 };

 /* convert 12-bit TMP108 register value to milliCelsius */
 static inline int tmp108_temp_reg_to_mC(s16 val)
 {
 	return (val & ~0x0f) * 1000 / 256;
 }

 /* convert milliCelsius to left adjusted 12-bit TMP108 register value */
 static inline u16 tmp108_mC_to_temp_reg(int val)
 {
 	return (val * 256) / 1000;
 }

 static int tmp108_read(struct device *dev, enum hwmon_sensor_types type,
 		       u32 attr, int channel, long *temp)
 {
 	struct tmp108 *tmp108 = dev_get_drvdata(dev);
 	unsigned int regval;
 	int err, hyst;

 	if (type == hwmon_chip) {
 		if (attr == hwmon_chip_update_interval) {
 			err = regmap_read(tmp108->regmap, TMP108_REG_CONF,
 					  &regval);
 			if (err < 0)
 				return err;
 			switch (regval & TMP108_CONF_CONVRATE_MASK) {
 			case TMP108_CONVRATE_0P25HZ:
 			default:
 				*temp = 4000;
 				break;
 			case TMP108_CONVRATE_1HZ:
 				*temp = 1000;
 				break;
 			case TMP108_CONVRATE_4HZ:
 				*temp = 250;
 				break;
 			case TMP108_CONVRATE_16HZ:
 				*temp = 63;
 				break;
 			}
 			return 0;
 		}
 		return -EOPNOTSUPP;
 	}

 	switch (attr) {
 	case hwmon_temp_input:
 		/* Is it too early to return a conversion ? */
 		if (time_before(jiffies, tmp108->ready_time)) {
 			dev_dbg(dev, "%s: Conversion not ready yet..\n",
 				__func__);
 			return -EAGAIN;
 		}
 		err = regmap_read(tmp108->regmap, TMP108_REG_TEMP, &regval);
 		if (err < 0)
 			return err;
 		*temp = tmp108_temp_reg_to_mC(regval);
 		break;
 	case hwmon_temp_min:
 	case hwmon_temp_max:
 		err = regmap_read(tmp108->regmap, attr == hwmon_temp_min ?
 				  TMP108_REG_TLOW : TMP108_REG_THIGH, &regval);
 		if (err < 0)
 			return err;
 		*temp = tmp108_temp_reg_to_mC(regval);
 		break;
 	case hwmon_temp_min_alarm:
 	case hwmon_temp_max_alarm:
 		err = regmap_read(tmp108->regmap, TMP108_REG_CONF, &regval);
 		if (err < 0)
 			return err;
 		*temp = !!(regval & (attr == hwmon_temp_min_alarm ?
 				     TMP108_CONF_FL : TMP108_CONF_FH));
 		break;
 	case hwmon_temp_min_hyst:
 	case hwmon_temp_max_hyst:
 		err = regmap_read(tmp108->regmap, TMP108_REG_CONF, &regval);
 		if (err < 0)
 			return err;
 		switch (regval & TMP108_CONF_HYSTERESIS_MASK) {
 		case TMP108_HYSTERESIS_0C:
 		default:
 			hyst = 0;
 			break;
 		case TMP108_HYSTERESIS_1C:
 			hyst = 1000;
 			break;
 		case TMP108_HYSTERESIS_2C:
 			hyst = 2000;
 			break;
 		case TMP108_HYSTERESIS_4C:
 			hyst = 4000;
 			break;
 		}
 		err = regmap_read(tmp108->regmap, attr == hwmon_temp_min_hyst ?
 				  TMP108_REG_TLOW : TMP108_REG_THIGH, &regval);
 		if (err < 0)
 			return err;
 		*temp = tmp108_temp_reg_to_mC(regval);
 		if (attr == hwmon_temp_min_hyst)
 			*temp += hyst;
 		else
 			*temp -= hyst;
 		break;
 	default:
 		return -EOPNOTSUPP;
 	}

 	return 0;
 }

 static int tmp108_write(struct device *dev, enum hwmon_sensor_types type,
 			u32 attr, int channel, long temp)
 {
 	struct tmp108 *tmp108 = dev_get_drvdata(dev);
 	u32 regval, mask;
 	int err;

 	if (type == hwmon_chip) {
 		if (attr == hwmon_chip_update_interval) {
 			if (temp < 156)
 				mask = TMP108_CONVRATE_16HZ;
 			else if (temp < 625)
 				mask = TMP108_CONVRATE_4HZ;
 			else if (temp < 2500)
 				mask = TMP108_CONVRATE_1HZ;
 			else
 				mask = TMP108_CONVRATE_0P25HZ;
 			return regmap_update_bits(tmp108->regmap,
 						  TMP108_REG_CONF,
 						  TMP108_CONF_CONVRATE_MASK,
 						  mask);
 		}
 		return -EOPNOTSUPP;
 	}

 	switch (attr) {
 	case hwmon_temp_min:
 	case hwmon_temp_max:
 		temp = clamp_val(temp, TMP108_TEMP_MIN_MC, TMP108_TEMP_MAX_MC);
 		return regmap_write(tmp108->regmap,
 				    attr == hwmon_temp_min ?
 					TMP108_REG_TLOW : TMP108_REG_THIGH,
 				    tmp108_mC_to_temp_reg(temp));
 	case hwmon_temp_min_hyst:
 	case hwmon_temp_max_hyst:
 		temp = clamp_val(temp, TMP108_TEMP_MIN_MC, TMP108_TEMP_MAX_MC);
 		err = regmap_read(tmp108->regmap,
 				  attr == hwmon_temp_min_hyst ?
 					TMP108_REG_TLOW : TMP108_REG_THIGH,
 				  &regval);
 		if (err < 0)
 			return err;
 		if (attr == hwmon_temp_min_hyst)
 			temp -= tmp108_temp_reg_to_mC(regval);
 		else
 			temp = tmp108_temp_reg_to_mC(regval) - temp;
 		if (temp < 500)
 			mask = TMP108_HYSTERESIS_0C;
 		else if (temp < 1500)
 			mask = TMP108_HYSTERESIS_1C;
 		else if (temp < 3000)
 			mask = TMP108_HYSTERESIS_2C;
 		else
 			mask = TMP108_HYSTERESIS_4C;
 		return regmap_update_bits(tmp108->regmap, TMP108_REG_CONF,
 					  TMP108_CONF_HYSTERESIS_MASK, mask);
 	default:
 		return -EOPNOTSUPP;
 	}
 }

 static umode_t tmp108_is_visible(const void *data, enum hwmon_sensor_types type,
 				 u32 attr, int channel)
 {
 	if (type == hwmon_chip && attr == hwmon_chip_update_interval)
 		return 0644;

 	if (type != hwmon_temp)
 		return 0;

 	switch (attr) {
 	case hwmon_temp_input:
 	case hwmon_temp_min_alarm:
 	case hwmon_temp_max_alarm:
 		return 0444;
 	case hwmon_temp_min:
 	case hwmon_temp_max:
 	case hwmon_temp_min_hyst:
 	case hwmon_temp_max_hyst:
 		return 0644;
 	default:
 		return 0;
 	}
 }

 static u32 tmp108_chip_config[] = {
 	HWMON_C_REGISTER_TZ | HWMON_C_UPDATE_INTERVAL,
 	0
 };

 static const struct hwmon_channel_info tmp108_chip = {
 	.type = hwmon_chip,
 	.config = tmp108_chip_config,
 };

 static u32 tmp108_temp_config[] = {
 	HWMON_T_INPUT | HWMON_T_MAX | HWMON_T_MIN | HWMON_T_MIN_HYST
 		| HWMON_T_MAX_HYST | HWMON_T_MIN_ALARM | HWMON_T_MAX_ALARM,
 	0
 };

 static const struct hwmon_channel_info tmp108_temp = {
 	.type = hwmon_temp,
 	.config = tmp108_temp_config,
 };

 static const struct hwmon_channel_info *tmp108_info[] = {
 	&tmp108_chip,
 	&tmp108_temp,
 	NULL
 };

 static const struct hwmon_ops tmp108_hwmon_ops = {
 	.is_visible = tmp108_is_visible,
 	.read = tmp108_read,
 	.write = tmp108_write,
 };

 static const struct hwmon_chip_info tmp108_chip_info = {
 	.ops = &tmp108_hwmon_ops,
 	.info = tmp108_info,
 };

 static void tmp108_restore_config(void *data)
 {
 	struct tmp108 *tmp108 = data;

 	regmap_write(tmp108->regmap, TMP108_REG_CONF, tmp108->orig_config);
 }

 static bool tmp108_is_writeable_reg(struct device *dev, unsigned int reg)
 {
 	return reg != TMP108_REG_TEMP;
 }

 static bool tmp108_is_volatile_reg(struct device *dev, unsigned int reg)
 {
 	/* Configuration register must be volatile to enable FL and FH. */
 	return reg == TMP108_REG_TEMP || reg == TMP108_REG_CONF;
 }

 static const struct regmap_config tmp108_regmap_config = {
 	.reg_bits = 8,
 	.val_bits = 16,
 	.max_register = TMP108_REG_THIGH,
 	.writeable_reg = tmp108_is_writeable_reg,
 	.volatile_reg = tmp108_is_volatile_reg,
 	.val_format_endian = REGMAP_ENDIAN_BIG,
 	.cache_type = REGCACHE_RBTREE,
 	.use_single_read = true,
 	.use_single_write = true,
 };

 static int tmp108_probe(struct i2c_client *client,
 			const struct i2c_device_id *id)
 {
 	struct device *dev = &client->dev;
 	struct device *hwmon_dev;
 	struct tmp108 *tmp108;
 	int err;
 	u32 config;

 	if (!i2c_check_functionality(client->adapter,
 				     I2C_FUNC_SMBUS_WORD_DATA)) {
 		dev_err(dev,
 			"adapter doesn't support SMBus word transactions\n");
 		return -ENODEV;
 	}

 	tmp108 = devm_kzalloc(dev, sizeof(*tmp108), GFP_KERNEL);
 	if (!tmp108)
 		return -ENOMEM;

 	dev_set_drvdata(dev, tmp108);

 	tmp108->regmap = devm_regmap_init_i2c(client, &tmp108_regmap_config);
 	if (IS_ERR(tmp108->regmap)) {
 		err = PTR_ERR(tmp108->regmap);
 		dev_err(dev, "regmap init failed: %d", err);
 		return err;
 	}

 	err = regmap_read(tmp108->regmap, TMP108_REG_CONF, &config);
 	if (err < 0) {
 		dev_err(dev, "error reading config register: %d", err);
 		return err;
 	}
 	tmp108->orig_config = config;

 	/* Only continuous mode is supported. */
 	config &= ~TMP108_CONF_MODE_MASK;
 	config |= TMP108_MODE_CONTINUOUS;

 	/* Only comparator mode is supported. */
 	config &= ~TMP108_CONF_TM;

 	err = regmap_write(tmp108->regmap, TMP108_REG_CONF, config);
 	if (err < 0) {
 		dev_err(dev, "error writing config register: %d", err);
 		return err;
 	}

 	tmp108->ready_time = jiffies;
 	if ((tmp108->orig_config & TMP108_CONF_MODE_MASK) ==
 	    TMP108_MODE_SHUTDOWN)
 		tmp108->ready_time +=
 			msecs_to_jiffies(TMP108_CONVERSION_TIME_MS);

 	err = devm_add_action_or_reset(dev, tmp108_restore_config, tmp108);
 	if (err) {
 		dev_err(dev, "add action or reset failed: %d", err);
 		return err;
 	}

 	hwmon_dev = devm_hwmon_device_register_with_info(dev, client->name,
 							 tmp108,
 							 &tmp108_chip_info,
 							 NULL);
 	return PTR_ERR_OR_ZERO(hwmon_dev);
 }

 static int __maybe_unused tmp108_suspend(struct device *dev)
 {
 	struct tmp108 *tmp108 = dev_get_drvdata(dev);

 	return regmap_update_bits(tmp108->regmap, TMP108_REG_CONF,
 				  TMP108_CONF_MODE_MASK, TMP108_MODE_SHUTDOWN);
 }

 static int __maybe_unused tmp108_resume(struct device *dev)
 {
 	struct tmp108 *tmp108 = dev_get_drvdata(dev);
 	int err;

 	err = regmap_update_bits(tmp108->regmap, TMP108_REG_CONF,
 				 TMP108_CONF_MODE_MASK, TMP108_MODE_CONTINUOUS);
 	tmp108->ready_time = jiffies +
 			     msecs_to_jiffies(TMP108_CONVERSION_TIME_MS);
 	return err;
 }

 static SIMPLE_DEV_PM_OPS(tmp108_dev_pm_ops, tmp108_suspend, tmp108_resume);

 static const struct i2c_device_id tmp108_i2c_ids[] = {
 	{ "tmp108", 0 },
 	{ }
 };
 MODULE_DEVICE_TABLE(i2c, tmp108_i2c_ids);

 #ifdef CONFIG_OF
 static const struct of_device_id tmp108_of_ids[] = {
 	{ .compatible = "ti,tmp108", },
 	{}
 };
 MODULE_DEVICE_TABLE(of, tmp108_of_ids);
 #endif

 static struct i2c_driver tmp108_driver = {
 	.driver = {
 		.name	= DRIVER_NAME,
 		.pm	= &tmp108_dev_pm_ops,
 		.of_match_table = of_match_ptr(tmp108_of_ids),
 	},
 	.probe		= tmp108_probe,
 	.id_table	= tmp108_i2c_ids,
 };

 module_i2c_driver(tmp108_driver);

 MODULE_AUTHOR("John Muir <john@jmuir.com>");
 MODULE_DESCRIPTION("Texas Instruments TMP108 temperature sensor driver");
 MODULE_LICENSE("GPL");
	/* Texas Instruments TMP108 SMBus temperature sensor driver
	*
	* Copyright (C) 2016 John Muir <john@jmuir.com>
	*
	* 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.
	*
	* 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 <linux/delay.h>
	#include <linux/device.h>
	#include <linux/err.h>
	#include <linux/hwmon.h>
	#include <linux/hwmon-sysfs.h>
	#include <linux/module.h>
	#include <linux/mutex.h>
	#include <linux/of.h>
	#include <linux/i2c.h>
	#include <linux/init.h>
	#include <linux/jiffies.h>
	#include <linux/regmap.h>
	#include <linux/slab.h>

	#define DRIVER_NAME "tmp108"

	#define TMP108_REG_TEMP 0x00
	#define TMP108_REG_CONF 0x01
	#define TMP108_REG_TLOW 0x02
	#define TMP108_REG_THIGH 0x03

	#define TMP108_TEMP_MIN_MC -50000 /* Minimum millicelcius. */
	#define TMP108_TEMP_MAX_MC 127937 /* Maximum millicelcius. */

	/* Configuration register bits.
	* Note: these bit definitions are byte swapped.
	*/
	#define TMP108_CONF_M0 0x0100 /* Sensor mode. */
	#define TMP108_CONF_M1 0x0200
	#define TMP108_CONF_TM 0x0400 /* Thermostat mode. */
	#define TMP108_CONF_FL 0x0800 /* Watchdog flag - TLOW */
	#define TMP108_CONF_FH 0x1000 /* Watchdog flag - THIGH */
	#define TMP108_CONF_CR0 0x2000 /* Conversion rate. */
	#define TMP108_CONF_CR1 0x4000
	#define TMP108_CONF_ID 0x8000
	#define TMP108_CONF_HYS0 0x0010 /* Hysteresis. */
	#define TMP108_CONF_HYS1 0x0020
	#define TMP108_CONF_POL 0x0080 /* Polarity of alert. */

	/* Defaults set by the hardware upon reset. */
	#define TMP108_CONF_DEFAULTS (TMP108_CONF_CR0 \| TMP108_CONF_TM \|\
	TMP108_CONF_HYS0 \| TMP108_CONF_M1)
	/* These bits are read-only. */
	#define TMP108_CONF_READ_ONLY (TMP108_CONF_FL \| TMP108_CONF_FH \|\
	TMP108_CONF_ID)

	#define TMP108_CONF_MODE_MASK (TMP108_CONF_M0\|TMP108_CONF_M1)
	#define TMP108_MODE_SHUTDOWN 0x0000
	#define TMP108_MODE_ONE_SHOT TMP108_CONF_M0
	#define TMP108_MODE_CONTINUOUS TMP108_CONF_M1 /* Default */
	/* When M1 is set, M0 is ignored. */

	#define TMP108_CONF_CONVRATE_MASK (TMP108_CONF_CR0\|TMP108_CONF_CR1)
	#define TMP108_CONVRATE_0P25HZ 0x0000
	#define TMP108_CONVRATE_1HZ TMP108_CONF_CR0 /* Default */
	#define TMP108_CONVRATE_4HZ TMP108_CONF_CR1
	#define TMP108_CONVRATE_16HZ (TMP108_CONF_CR0\|TMP108_CONF_CR1)

	#define TMP108_CONF_HYSTERESIS_MASK (TMP108_CONF_HYS0\|TMP108_CONF_HYS1)
	#define TMP108_HYSTERESIS_0C 0x0000
	#define TMP108_HYSTERESIS_1C TMP108_CONF_HYS0 /* Default */
	#define TMP108_HYSTERESIS_2C TMP108_CONF_HYS1
	#define TMP108_HYSTERESIS_4C (TMP108_CONF_HYS0\|TMP108_CONF_HYS1)

	#define TMP108_CONVERSION_TIME_MS 30 /* in milli-seconds */

	struct tmp108 {
	struct regmap *regmap;
	u16 orig_config;
	unsigned long ready_time;
	};

	/* convert 12-bit TMP108 register value to milliCelsius */
	static inline int tmp108_temp_reg_to_mC(s16 val)
	{
	return (val & ~0x0f) * 1000 / 256;
	}

	/* convert milliCelsius to left adjusted 12-bit TMP108 register value */
	static inline u16 tmp108_mC_to_temp_reg(int val)
	{
	return (val * 256) / 1000;
	}

	static int tmp108_read(struct device *dev, enum hwmon_sensor_types type,
	u32 attr, int channel, long *temp)
	{
	struct tmp108 *tmp108 = dev_get_drvdata(dev);
	unsigned int regval;
	int err, hyst;

	if (type == hwmon_chip) {
	if (attr == hwmon_chip_update_interval) {
	err = regmap_read(tmp108->regmap, TMP108_REG_CONF,
	&regval);
	if (err < 0)
	return err;
	switch (regval & TMP108_CONF_CONVRATE_MASK) {
	case TMP108_CONVRATE_0P25HZ:
	default:
	*temp = 4000;
	break;
	case TMP108_CONVRATE_1HZ:
	*temp = 1000;
	break;
	case TMP108_CONVRATE_4HZ:
	*temp = 250;
	break;
	case TMP108_CONVRATE_16HZ:
	*temp = 63;
	break;
	}
	return 0;
	}
	return -EOPNOTSUPP;
	}

	switch (attr) {
	case hwmon_temp_input:
	/* Is it too early to return a conversion ? */
	if (time_before(jiffies, tmp108->ready_time)) {
	dev_dbg(dev, "%s: Conversion not ready yet..\n",
	__func__);
	return -EAGAIN;
	}
	err = regmap_read(tmp108->regmap, TMP108_REG_TEMP, &regval);
	if (err < 0)
	return err;
	*temp = tmp108_temp_reg_to_mC(regval);
	break;
	case hwmon_temp_min:
	case hwmon_temp_max:
	err = regmap_read(tmp108->regmap, attr == hwmon_temp_min ?
	TMP108_REG_TLOW : TMP108_REG_THIGH, &regval);
	if (err < 0)
	return err;
	*temp = tmp108_temp_reg_to_mC(regval);
	break;
	case hwmon_temp_min_alarm:
	case hwmon_temp_max_alarm:
	err = regmap_read(tmp108->regmap, TMP108_REG_CONF, &regval);
	if (err < 0)
	return err;
	*temp = !!(regval & (attr == hwmon_temp_min_alarm ?
	TMP108_CONF_FL : TMP108_CONF_FH));
	break;
	case hwmon_temp_min_hyst:
	case hwmon_temp_max_hyst:
	err = regmap_read(tmp108->regmap, TMP108_REG_CONF, &regval);
	if (err < 0)
	return err;
	switch (regval & TMP108_CONF_HYSTERESIS_MASK) {
	case TMP108_HYSTERESIS_0C:
	default:
	hyst = 0;
	break;
	case TMP108_HYSTERESIS_1C:
	hyst = 1000;
	break;
	case TMP108_HYSTERESIS_2C:
	hyst = 2000;
	break;
	case TMP108_HYSTERESIS_4C:
	hyst = 4000;
	break;
	}
	err = regmap_read(tmp108->regmap, attr == hwmon_temp_min_hyst ?
	TMP108_REG_TLOW : TMP108_REG_THIGH, &regval);
	if (err < 0)
	return err;
	*temp = tmp108_temp_reg_to_mC(regval);
	if (attr == hwmon_temp_min_hyst)
	*temp += hyst;
	else
	*temp -= hyst;
	break;
	default:
	return -EOPNOTSUPP;
	}

	return 0;
	}

	static int tmp108_write(struct device *dev, enum hwmon_sensor_types type,
	u32 attr, int channel, long temp)
	{
	struct tmp108 *tmp108 = dev_get_drvdata(dev);
	u32 regval, mask;
	int err;

	if (type == hwmon_chip) {
	if (attr == hwmon_chip_update_interval) {
	if (temp < 156)
	mask = TMP108_CONVRATE_16HZ;
	else if (temp < 625)
	mask = TMP108_CONVRATE_4HZ;
	else if (temp < 2500)
	mask = TMP108_CONVRATE_1HZ;
	else
	mask = TMP108_CONVRATE_0P25HZ;
	return regmap_update_bits(tmp108->regmap,
	TMP108_REG_CONF,
	TMP108_CONF_CONVRATE_MASK,
	mask);
	}
	return -EOPNOTSUPP;
	}

	switch (attr) {
	case hwmon_temp_min:
	case hwmon_temp_max:
	temp = clamp_val(temp, TMP108_TEMP_MIN_MC, TMP108_TEMP_MAX_MC);
	return regmap_write(tmp108->regmap,
	attr == hwmon_temp_min ?
	TMP108_REG_TLOW : TMP108_REG_THIGH,
	tmp108_mC_to_temp_reg(temp));
	case hwmon_temp_min_hyst:
	case hwmon_temp_max_hyst:
	temp = clamp_val(temp, TMP108_TEMP_MIN_MC, TMP108_TEMP_MAX_MC);
	err = regmap_read(tmp108->regmap,
	attr == hwmon_temp_min_hyst ?
	TMP108_REG_TLOW : TMP108_REG_THIGH,
	&regval);
	if (err < 0)
	return err;
	if (attr == hwmon_temp_min_hyst)
	temp -= tmp108_temp_reg_to_mC(regval);
	else
	temp = tmp108_temp_reg_to_mC(regval) - temp;
	if (temp < 500)
	mask = TMP108_HYSTERESIS_0C;
	else if (temp < 1500)
	mask = TMP108_HYSTERESIS_1C;
	else if (temp < 3000)
	mask = TMP108_HYSTERESIS_2C;
	else
	mask = TMP108_HYSTERESIS_4C;
	return regmap_update_bits(tmp108->regmap, TMP108_REG_CONF,
	TMP108_CONF_HYSTERESIS_MASK, mask);
	default:
	return -EOPNOTSUPP;
	}
	}

	static umode_t tmp108_is_visible(const void *data, enum hwmon_sensor_types type,
	u32 attr, int channel)
	{
	if (type == hwmon_chip && attr == hwmon_chip_update_interval)
	return 0644;

	if (type != hwmon_temp)
	return 0;

	switch (attr) {
	case hwmon_temp_input:
	case hwmon_temp_min_alarm:
	case hwmon_temp_max_alarm:
	return 0444;
	case hwmon_temp_min:
	case hwmon_temp_max:
	case hwmon_temp_min_hyst:
	case hwmon_temp_max_hyst:
	return 0644;
	default:
	return 0;
	}
	}

	static u32 tmp108_chip_config[] = {
	HWMON_C_REGISTER_TZ \| HWMON_C_UPDATE_INTERVAL,
	0
	};

	static const struct hwmon_channel_info tmp108_chip = {
	.type = hwmon_chip,
	.config = tmp108_chip_config,
	};

	static u32 tmp108_temp_config[] = {
	HWMON_T_INPUT \| HWMON_T_MAX \| HWMON_T_MIN \| HWMON_T_MIN_HYST
	\| HWMON_T_MAX_HYST \| HWMON_T_MIN_ALARM \| HWMON_T_MAX_ALARM,
	0
	};

	static const struct hwmon_channel_info tmp108_temp = {
	.type = hwmon_temp,
	.config = tmp108_temp_config,
	};

	static const struct hwmon_channel_info *tmp108_info[] = {
	&tmp108_chip,
	&tmp108_temp,
	NULL
	};

	static const struct hwmon_ops tmp108_hwmon_ops = {
	.is_visible = tmp108_is_visible,
	.read = tmp108_read,
	.write = tmp108_write,
	};

	static const struct hwmon_chip_info tmp108_chip_info = {
	.ops = &tmp108_hwmon_ops,
	.info = tmp108_info,
	};

	static void tmp108_restore_config(void *data)
	{
	struct tmp108 *tmp108 = data;

	regmap_write(tmp108->regmap, TMP108_REG_CONF, tmp108->orig_config);
	}

	static bool tmp108_is_writeable_reg(struct device *dev, unsigned int reg)
	{
	return reg != TMP108_REG_TEMP;
	}

	static bool tmp108_is_volatile_reg(struct device *dev, unsigned int reg)
	{
	/* Configuration register must be volatile to enable FL and FH. */
	return reg == TMP108_REG_TEMP \|\| reg == TMP108_REG_CONF;
	}

	static const struct regmap_config tmp108_regmap_config = {
	.reg_bits = 8,
	.val_bits = 16,
	.max_register = TMP108_REG_THIGH,
	.writeable_reg = tmp108_is_writeable_reg,
	.volatile_reg = tmp108_is_volatile_reg,
	.val_format_endian = REGMAP_ENDIAN_BIG,
	.cache_type = REGCACHE_RBTREE,
	.use_single_read = true,
	.use_single_write = true,
	};

	static int tmp108_probe(struct i2c_client *client,
	const struct i2c_device_id *id)
	{
	struct device *dev = &client->dev;
	struct device *hwmon_dev;
	struct tmp108 *tmp108;
	int err;
	u32 config;

	if (!i2c_check_functionality(client->adapter,
	I2C_FUNC_SMBUS_WORD_DATA)) {
	dev_err(dev,
	"adapter doesn't support SMBus word transactions\n");
	return -ENODEV;
	}

	tmp108 = devm_kzalloc(dev, sizeof(*tmp108), GFP_KERNEL);
	if (!tmp108)
	return -ENOMEM;

	dev_set_drvdata(dev, tmp108);

	tmp108->regmap = devm_regmap_init_i2c(client, &tmp108_regmap_config);
	if (IS_ERR(tmp108->regmap)) {
	err = PTR_ERR(tmp108->regmap);
	dev_err(dev, "regmap init failed: %d", err);
	return err;
	}

	err = regmap_read(tmp108->regmap, TMP108_REG_CONF, &config);
	if (err < 0) {
	dev_err(dev, "error reading config register: %d", err);
	return err;
	}
	tmp108->orig_config = config;

	/* Only continuous mode is supported. */
	config &= ~TMP108_CONF_MODE_MASK;
	config \|= TMP108_MODE_CONTINUOUS;

	/* Only comparator mode is supported. */
	config &= ~TMP108_CONF_TM;

	err = regmap_write(tmp108->regmap, TMP108_REG_CONF, config);
	if (err < 0) {
	dev_err(dev, "error writing config register: %d", err);
	return err;
	}

	tmp108->ready_time = jiffies;
	if ((tmp108->orig_config & TMP108_CONF_MODE_MASK) ==
	TMP108_MODE_SHUTDOWN)
	tmp108->ready_time +=
	msecs_to_jiffies(TMP108_CONVERSION_TIME_MS);

	err = devm_add_action_or_reset(dev, tmp108_restore_config, tmp108);
	if (err) {
	dev_err(dev, "add action or reset failed: %d", err);
	return err;
	}

	hwmon_dev = devm_hwmon_device_register_with_info(dev, client->name,
	tmp108,
	&tmp108_chip_info,
	NULL);
	return PTR_ERR_OR_ZERO(hwmon_dev);
	}

	static int __maybe_unused tmp108_suspend(struct device *dev)
	{
	struct tmp108 *tmp108 = dev_get_drvdata(dev);

	return regmap_update_bits(tmp108->regmap, TMP108_REG_CONF,
	TMP108_CONF_MODE_MASK, TMP108_MODE_SHUTDOWN);
	}

	static int __maybe_unused tmp108_resume(struct device *dev)
	{
	struct tmp108 *tmp108 = dev_get_drvdata(dev);
	int err;

	err = regmap_update_bits(tmp108->regmap, TMP108_REG_CONF,
	TMP108_CONF_MODE_MASK, TMP108_MODE_CONTINUOUS);
	tmp108->ready_time = jiffies +
	msecs_to_jiffies(TMP108_CONVERSION_TIME_MS);
	return err;
	}

	static SIMPLE_DEV_PM_OPS(tmp108_dev_pm_ops, tmp108_suspend, tmp108_resume);

	static const struct i2c_device_id tmp108_i2c_ids[] = {
	{ "tmp108", 0 },
	{ }
	};
	MODULE_DEVICE_TABLE(i2c, tmp108_i2c_ids);

	#ifdef CONFIG_OF
	static const struct of_device_id tmp108_of_ids[] = {
	{ .compatible = "ti,tmp108", },
	{}
	};
	MODULE_DEVICE_TABLE(of, tmp108_of_ids);
	#endif

	static struct i2c_driver tmp108_driver = {
	.driver = {
	.name = DRIVER_NAME,
	.pm = &tmp108_dev_pm_ops,
	.of_match_table = of_match_ptr(tmp108_of_ids),
	},
	.probe = tmp108_probe,
	.id_table = tmp108_i2c_ids,
	};

	module_i2c_driver(tmp108_driver);

	MODULE_AUTHOR("John Muir <john@jmuir.com>");
	MODULE_DESCRIPTION("Texas Instruments TMP108 temperature sensor driver");
	MODULE_LICENSE("GPL");