text: // SPDX-License-Identifier: GPL-2.0-or-later
  /*
   * STTS751 sensor driver
   *
   * Copyright (C) 2016-2017 Istituto Italiano di Tecnologia - RBCS - EDL
   * Robotics, Brain and Cognitive Sciences department
   * Electronic Design Laboratory
   *
   * Written by Andrea Merello <andrea.merello@gmail.com>
   *
   * Based on  LM95241 driver and LM90 driver
   */
  
  #include <linux/bitops.h>
  #include <linux/err.h>
  #include <linux/hwmon.h>
  #include <linux/hwmon-sysfs.h>
  #include <linux/i2c.h>
  #include <linux/init.h>
  #include <linux/interrupt.h>
  #include <linux/jiffies.h>
  #include <linux/module.h>
  #include <linux/mutex.h>
  #include <linux/property.h>
  #include <linux/slab.h>
  #include <linux/sysfs.h>
  #include <linux/util_macros.h>
  
  #define DEVNAME "stts751"
  
  static const unsigned short normal_i2c[] = {
  	0x48, 0x49, 0x38, 0x39,  /* STTS751-0 */
  	0x4A, 0x4B, 0x3A, 0x3B,  /* STTS751-1 */
  	I2C_CLIENT_END };
  
  #define STTS751_REG_TEMP_H	0x00
  #define STTS751_REG_STATUS	0x01
  #define STTS751_STATUS_TRIPT	BIT(0)
  #define STTS751_STATUS_TRIPL	BIT(5)
  #define STTS751_STATUS_TRIPH	BIT(6)
  #define STTS751_REG_TEMP_L	0x02
  #define STTS751_REG_CONF	0x03
  #define STTS751_CONF_RES_MASK	0x0C
  #define STTS751_CONF_RES_SHIFT  2
  #define STTS751_CONF_EVENT_DIS  BIT(7)
  #define STTS751_CONF_STOP	BIT(6)
  #define STTS751_REG_RATE	0x04
  #define STTS751_REG_HLIM_H	0x05
  #define STTS751_REG_HLIM_L	0x06
  #define STTS751_REG_LLIM_H	0x07
  #define STTS751_REG_LLIM_L	0x08
  #define STTS751_REG_TLIM	0x20
  #define STTS751_REG_HYST	0x21
  #define STTS751_REG_SMBUS_TO	0x22
  
  #define STTS751_REG_PROD_ID	0xFD
  #define STTS751_REG_MAN_ID	0xFE
  #define STTS751_REG_REV_ID	0xFF
  
  #define STTS751_0_PROD_ID	0x00
  #define STTS751_1_PROD_ID	0x01
  #define ST_MAN_ID		0x53
  
  /*
   * Possible update intervals are (in mS):
   * 16000, 8000, 4000, 2000, 1000, 500, 250, 125, 62.5, 31.25
   * However we are not going to complicate things too much and we stick to the
   * approx value in mS.
   */
  static const int stts751_intervals[] = {
  	16000, 8000, 4000, 2000, 1000, 500, 250, 125, 63, 31
  };
  
  static const struct i2c_device_id stts751_id[] = {
  	{ "stts751", 0 },
  	{ }
  };
  
  static const struct of_device_id __maybe_unused stts751_of_match[] = {
  	{ .compatible = "stts751" },
  	{ },
  };
  MODULE_DEVICE_TABLE(of, stts751_of_match);
  
  struct stts751_priv {
  	struct device *dev;
  	struct i2c_client *client;
  	struct mutex access_lock;
  	u8 interval;
  	int res;
  	int event_max, event_min;
  	int therm;
  	int hyst;
  	bool smbus_timeout;
  	int temp;
  	unsigned long last_update, last_alert_update;
  	u8 config;
  	bool min_alert, max_alert, therm_trip;
  	bool data_valid, alert_valid;
  	bool notify_max, notify_min;
  };
  
  /*
   * These functions converts temperature from HW format to integer format and
   * vice-vers. They are (mostly) taken from lm90 driver. Unit is in mC.
   */
  static int stts751_to_deg(s16 hw_val)
  {
  	return hw_val * 125 / 32;
  }
  
  static s32 stts751_to_hw(int val)
  {
  	return DIV_ROUND_CLOSEST(val, 125) * 32;
  }
  
  static int stts751_adjust_resolution(struct stts751_priv *priv)
  {
  	u8 res;
  
  	switch (priv->interval) {
  	case 9:
  		/* 10 bits */
  		res = 0;
  		break;
  	case 8:
  		/* 11 bits */
  		res = 1;
  		break;
  	default:
  		/* 12 bits */
  		res = 3;
  		break;
  	}
  
  	if (priv->res == res)
  		return 0;
  
  	priv->config &= ~STTS751_CONF_RES_MASK;
  	priv->config |= res << STTS751_CONF_RES_SHIFT;
  	dev_dbg(&priv->client->dev, "setting res %d. config %x",
  		res, priv->config);
  	priv->res = res;
  
  	return i2c_smbus_write_byte_data(priv->client,
  				STTS751_REG_CONF, priv->config);
  }
  
  static int stts751_update_temp(struct stts751_priv *priv)
  {
  	s32 integer1, integer2, frac;
  
  	/*
  	 * There is a trick here, like in the lm90 driver. We have to read two
  	 * registers to get the sensor temperature, but we have to beware a
  	 * conversion could occur between the readings. We could use the
  	 * one-shot conversion register, but we don't want to do this (disables
  	 * hardware monitoring). So the solution used here is to read the high
  	 * byte once, then the low byte, then the high byte again. If the new
  	 * high byte matches the old one, then we have a valid reading. Else we
  	 * have to read the low byte again, and now we believe we have a correct
  	 * reading.
  	 */
  	integer1 = i2c_smbus_read_byte_data(priv->client, STTS751_REG_TEMP_H);
  	if (integer1 < 0) {
  		dev_dbg(&priv->client->dev,
  			"I2C read failed (temp H). ret: %x\n", integer1);
  		return integer1;
  	}
  
  	frac = i2c_smbus_read_byte_data(priv->client, STTS751_REG_TEMP_L);
  	if (frac < 0) {
  		dev_dbg(&priv->client->dev,
  			"I2C read failed (temp L). ret: %x\n", frac);
  		return frac;
  	}
  
  	integer2 = i2c_smbus_read_byte_data(priv->client, STTS751_REG_TEMP_H);
  	if (integer2 < 0) {
  		dev_dbg(&priv->client->dev,
  			"I2C 2nd read failed (temp H). ret: %x\n", integer2);
  		return integer2;
  	}
  
  	if (integer1 != integer2) {
  		frac = i2c_smbus_read_byte_data(priv->client,
  						STTS751_REG_TEMP_L);
  		if (frac < 0) {
  			dev_dbg(&priv->client->dev,
  				"I2C 2nd read failed (temp L). ret: %x\n",
  				frac);
  			return frac;
  		}
  	}
  
  	priv->temp = stts751_to_deg((integer1 << 8) | frac);
  	return 0;
  }
  
  static int stts751_set_temp_reg16(struct stts751_priv *priv, int temp,
  				  u8 hreg, u8 lreg)
  {
  	s32 hwval;
  	int ret;
  
  	hwval = stts751_to_hw(temp);
  
  	ret = i2c_smbus_write_byte_data(priv->client, hreg, hwval >> 8);
  	if (ret)
  		return ret;
  
  	return i2c_smbus_write_byte_data(priv->client, lreg, hwval & 0xff);
  }
  
  static int stts751_set_temp_reg8(struct stts751_priv *priv, int temp, u8 reg)
  {
  	s32 hwval;
  
  	hwval = stts751_to_hw(temp);
  	return i2c_smbus_write_byte_data(priv->client, reg, hwval >> 8);
  }
  
  static int stts751_read_reg16(struct stts751_priv *priv, int *temp,
  			      u8 hreg, u8 lreg)
  {
  	int integer, frac;
  
  	integer = i2c_smbus_read_byte_data(priv->client, hreg);
  	if (integer < 0)
  		return integer;
  
  	frac = i2c_smbus_read_byte_data(priv->client, lreg);
  	if (frac < 0)
  		return frac;
  
  	*temp = stts751_to_deg((integer << 8) | frac);
  
  	return 0;
  }
  
  static int stts751_read_reg8(struct stts751_priv *priv, int *temp, u8 reg)
  {
  	int integer;
  
  	integer = i2c_smbus_read_byte_data(priv->client, reg);
  	if (integer < 0)
  		return integer;
  
  	*temp = stts751_to_deg(integer << 8);
  
  	return 0;
  }
  
  /*
   * Update alert flags without waiting for cache to expire. We detects alerts
   * immediately for the sake of the alert handler; we still need to deal with
   * caching to workaround the fact that alarm flags int the status register,
   * despite what the datasheet claims, gets always cleared on read.
   */
  static int stts751_update_alert(struct stts751_priv *priv)
  {
  	int ret;
  	bool conv_done;
  	int cache_time = msecs_to_jiffies(stts751_intervals[priv->interval]);
  
  	/*
  	 * Add another 10% because if we run faster than the HW conversion
  	 * rate we will end up in reporting incorrectly alarms.
  	 */
  	cache_time += cache_time / 10;
  
  	ret = i2c_smbus_read_byte_data(priv->client, STTS751_REG_STATUS);
  	if (ret < 0)
  		return ret;
  
  	dev_dbg(&priv->client->dev, "status reg %x\n", ret);
  	conv_done = ret & (STTS751_STATUS_TRIPH | STTS751_STATUS_TRIPL);
  	/*
  	 * Reset the cache if the cache time expired, or if we are sure
  	 * we have valid data from a device conversion, or if we know
  	 * our cache has been never written.
  	 *
  	 * Note that when the cache has been never written the point is
  	 * to correctly initialize the timestamp, rather than clearing
  	 * the cache values.
  	 *
  	 * Note that updating the cache timestamp when we get an alarm flag
  	 * is required, otherwise we could incorrectly report alarms to be zero.
  	 */
  	if (time_after(jiffies,	priv->last_alert_update + cache_time) ||
  	    conv_done || !priv->alert_valid) {
  		priv->max_alert = false;
  		priv->min_alert = false;
  		priv->alert_valid = true;
  		priv->last_alert_update = jiffies;
  		dev_dbg(&priv->client->dev, "invalidating alert cache\n");
  	}
  
  	priv->max_alert |= !!(ret & STTS751_STATUS_TRIPH);
  	priv->min_alert |= !!(ret & STTS751_STATUS_TRIPL);
  	priv->therm_trip = !!(ret & STTS751_STATUS_TRIPT);
  
  	dev_dbg(&priv->client->dev, "max_alert: %d, min_alert: %d, therm_trip: %d\n",
  		priv->max_alert, priv->min_alert, priv->therm_trip);
  
  	return 0;
  }
  
  static void stts751_alert(struct i2c_client *client,
  			  enum i2c_alert_protocol type, unsigned int data)
  {
  	int ret;
  	struct stts751_priv *priv = i2c_get_clientdata(client);
  
  	if (type != I2C_PROTOCOL_SMBUS_ALERT)
  		return;
  
  	dev_dbg(&client->dev, "alert!");
  
  	mutex_lock(&priv->access_lock);
  	ret = stts751_update_alert(priv);
  	if (ret < 0) {
  		/* default to worst case */
  		priv->max_alert = true;
  		priv->min_alert = true;
  
  		dev_warn(priv->dev,
  			 "Alert received, but can't communicate to the device. Triggering all alarms!");
  	}
  
  	if (priv->max_alert) {
  		if (priv->notify_max)
  			dev_notice(priv->dev, "got alert for HIGH temperature");
  		priv->notify_max = false;
  
  		/* unblock alert poll */
  		sysfs_notify(&priv->dev->kobj, NULL, "temp1_max_alarm");
  	}
  
  	if (priv->min_alert) {
  		if (priv->notify_min)
  			dev_notice(priv->dev, "got alert for LOW temperature");
  		priv->notify_min = false;
  
  		/* unblock alert poll */
  		sysfs_notify(&priv->dev->kobj, NULL, "temp1_min_alarm");
  	}
  
  	if (priv->min_alert || priv->max_alert)
  		kobject_uevent(&priv->dev->kobj, KOBJ_CHANGE);
  
  	mutex_unlock(&priv->access_lock);
  }
  
  static int stts751_update(struct stts751_priv *priv)
  {
  	int ret;
  	int cache_time = msecs_to_jiffies(stts751_intervals[priv->interval]);
  
  	if (time_after(jiffies,	priv->last_update + cache_time) ||
  	    !priv->data_valid) {
  		ret = stts751_update_temp(priv);
  		if (ret)
  			return ret;
  
  		ret = stts751_update_alert(priv);
  		if (ret)
  			return ret;
  		priv->data_valid = true;
  		priv->last_update = jiffies;
  	}
  
  	return 0;
  }
  
  static ssize_t max_alarm_show(struct device *dev,
  			      struct device_attribute *attr, char *buf)
  {
  	int ret;
  	struct stts751_priv *priv = dev_get_drvdata(dev);
  
  	mutex_lock(&priv->access_lock);
  	ret = stts751_update(priv);
  	if (!ret)
  		priv->notify_max = true;
  	mutex_unlock(&priv->access_lock);
  	if (ret < 0)
  		return ret;
  
  	return snprintf(buf, PAGE_SIZE, "%d\n", priv->max_alert);
  }
  
  static ssize_t min_alarm_show(struct device *dev,
  			      struct device_attribute *attr, char *buf)
  {
  	int ret;
  	struct stts751_priv *priv = dev_get_drvdata(dev);
  
  	mutex_lock(&priv->access_lock);
  	ret = stts751_update(priv);
  	if (!ret)
  		priv->notify_min = true;
  	mutex_unlock(&priv->access_lock);
  	if (ret < 0)
  		return ret;
  
  	return snprintf(buf, PAGE_SIZE, "%d\n", priv->min_alert);
  }
  
  static ssize_t input_show(struct device *dev, struct device_attribute *attr,
  			  char *buf)
  {
  	int ret;
  	struct stts751_priv *priv = dev_get_drvdata(dev);
  
  	mutex_lock(&priv->access_lock);
  	ret = stts751_update(priv);
  	mutex_unlock(&priv->access_lock);
  	if (ret < 0)
  		return ret;
  
  	return snprintf(buf, PAGE_SIZE, "%d\n", priv->temp);
  }
  
  static ssize_t therm_show(struct device *dev, struct device_attribute *attr,
  			  char *buf)
  {
  	struct stts751_priv *priv = dev_get_drvdata(dev);
  
  	return snprintf(buf, PAGE_SIZE, "%d\n", priv->therm);
  }
  
  static ssize_t therm_store(struct device *dev, struct device_attribute *attr,
  			   const char *buf, size_t count)
  {
  	int ret;
  	long temp;
  	struct stts751_priv *priv = dev_get_drvdata(dev);
  
  	if (kstrtol(buf, 10, &temp) < 0)
  		return -EINVAL;
  
  	/* HW works in range -64C to +127.937C */
  	temp = clamp_val(temp, -64000, 127937);
  	mutex_lock(&priv->access_lock);
  	ret = stts751_set_temp_reg8(priv, temp, STTS751_REG_TLIM);
  	if (ret)
  		goto exit;
  
  	dev_dbg(&priv->client->dev, "setting therm %ld", temp);
  
  	/*
  	 * hysteresis reg is relative to therm, so the HW does not need to be
  	 * adjusted, we need to update our local copy only.
  	 */
  	priv->hyst = temp - (priv->therm - priv->hyst);
  	priv->therm = temp;
  
  exit:
  	mutex_unlock(&priv->access_lock);
  	if (ret)
  		return ret;
  
  	return count;
  }
  
  static ssize_t hyst_show(struct device *dev, struct device_attribute *attr,
  			 char *buf)
  {
  	struct stts751_priv *priv = dev_get_drvdata(dev);
  
  	return snprintf(buf, PAGE_SIZE, "%d\n", priv->hyst);
  }
  
  static ssize_t hyst_store(struct device *dev, struct device_attribute *attr,
  			  const char *buf, size_t count)
  {
  	int ret;
  	long temp;
  
  	struct stts751_priv *priv = dev_get_drvdata(dev);
  
  	if (kstrtol(buf, 10, &temp) < 0)
  		return -EINVAL;
  
  	mutex_lock(&priv->access_lock);
  	/* HW works in range -64C to +127.937C */
  	temp = clamp_val(temp, -64000, priv->therm);
  	priv->hyst = temp;
  	dev_dbg(&priv->client->dev, "setting hyst %ld", temp);
  	temp = priv->therm - temp;
  	ret = stts751_set_temp_reg8(priv, temp, STTS751_REG_HYST);
  	mutex_unlock(&priv->access_lock);
  	if (ret)
  		return ret;
  
  	return count;
  }
  
  static ssize_t therm_trip_show(struct device *dev,
  			       struct device_attribute *attr, char *buf)
  {
  	int ret;
  	struct stts751_priv *priv = dev_get_drvdata(dev);
  
  	mutex_lock(&priv->access_lock);
  	ret = stts751_update(priv);
  	mutex_unlock(&priv->access_lock);
  	if (ret < 0)
  		return ret;
  
  	return snprintf(buf, PAGE_SIZE, "%d\n", priv->therm_trip);
  }
  
  static ssize_t max_show(struct device *dev, struct device_attribute *attr,
  			char *buf)
  {
  	struct stts751_priv *priv = dev_get_drvdata(dev);
  
  	return snprintf(buf, PAGE_SIZE, "%d\n", priv->event_max);
  }
  
  static ssize_t max_store(struct device *dev, struct device_attribute *attr,
  			 const char *buf, size_t count)
  {
  	int ret;
  	long temp;
  	struct stts751_priv *priv = dev_get_drvdata(dev);
  
  	if (kstrtol(buf, 10, &temp) < 0)
  		return -EINVAL;
  
  	mutex_lock(&priv->access_lock);
  	/* HW works in range -64C to +127.937C */
  	temp = clamp_val(temp, priv->event_min, 127937);
  	ret = stts751_set_temp_reg16(priv, temp,
  				     STTS751_REG_HLIM_H, STTS751_REG_HLIM_L);
  	if (ret)
  		goto exit;
  
  	dev_dbg(&priv->client->dev, "setting event max %ld", temp);
  	priv->event_max = temp;
  	ret = count;
  exit:
  	mutex_unlock(&priv->access_lock);
  	return ret;
  }
  
  static ssize_t min_show(struct device *dev, struct device_attribute *attr,
  			char *buf)
  {
  	struct stts751_priv *priv = dev_get_drvdata(dev);
  
  	return snprintf(buf, PAGE_SIZE, "%d\n", priv->event_min);
  }
  
  static ssize_t min_store(struct device *dev, struct device_attribute *attr,
  			 const char *buf, size_t count)
  {
  	int ret;
  	long temp;
  	struct stts751_priv *priv = dev_get_drvdata(dev);
  
  	if (kstrtol(buf, 10, &temp) < 0)
  		return -EINVAL;
  
  	mutex_lock(&priv->access_lock);
  	/* HW works in range -64C to +127.937C */
  	temp = clamp_val(temp, -64000, priv->event_max);
  	ret = stts751_set_temp_reg16(priv, temp,
  				     STTS751_REG_LLIM_H, STTS751_REG_LLIM_L);
  	if (ret)
  		goto exit;
  
  	dev_dbg(&priv->client->dev, "setting event min %ld", temp);
  	priv->event_min = temp;
  	ret = count;
  exit:
  	mutex_unlock(&priv->access_lock);
  	return ret;
  }
  
  static ssize_t interval_show(struct device *dev,
  			     struct device_attribute *attr, char *buf)
  {
  	struct stts751_priv *priv = dev_get_drvdata(dev);
  
  	return snprintf(buf, PAGE_SIZE, "%d\n",
  			stts751_intervals[priv->interval]);
  }
  
  static ssize_t interval_store(struct device *dev,
  			      struct device_attribute *attr, const char *buf,
  			      size_t count)
  {
  	unsigned long val;
  	int idx;
  	int ret = count;
  	struct stts751_priv *priv = dev_get_drvdata(dev);
  
  	if (kstrtoul(buf, 10, &val) < 0)
  		return -EINVAL;
  
  	idx = find_closest_descending(val, stts751_intervals,
  				      ARRAY_SIZE(stts751_intervals));
  
  	dev_dbg(&priv->client->dev, "setting interval. req:%lu, idx: %d, val: %d",
  		val, idx, stts751_intervals[idx]);
  
  	mutex_lock(&priv->access_lock);
  	if (priv->interval == idx)
  		goto exit;
  
  	/*
  	 * In early development stages I've become suspicious about the chip
  	 * starting to misbehave if I ever set, even briefly, an invalid
  	 * configuration. While I'm not sure this is really needed, be
  	 * conservative and set rate/resolution in such an order that avoids
  	 * passing through an invalid configuration.
  	 */
  
  	/* speed up: lower the resolution, then modify convrate */
  	if (priv->interval < idx) {
  		dev_dbg(&priv->client->dev, "lower resolution, then modify convrate");
  		priv->interval = idx;
  		ret = stts751_adjust_resolution(priv);
  		if (ret)
  			goto exit;
  	}
  
  	ret = i2c_smbus_write_byte_data(priv->client, STTS751_REG_RATE, idx);
  	if (ret)
  		goto exit;
  	/* slow down: modify convrate, then raise resolution */
  	if (priv->interval != idx) {
  		dev_dbg(&priv->client->dev, "modify convrate, then raise resolution");
  		priv->interval = idx;
  		ret = stts751_adjust_resolution(priv);
  		if (ret)
  			goto exit;
  	}
  	ret = count;
  exit:
  	mutex_unlock(&priv->access_lock);
  
  	return ret;
  }
  
  static int stts751_detect(struct i2c_client *new_client,
  			  struct i2c_board_info *info)
  {
  	struct i2c_adapter *adapter = new_client->adapter;
  	const char *name;
  	int tmp;
  
  	if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA))
  		return -ENODEV;
  
  	tmp = i2c_smbus_read_byte_data(new_client, STTS751_REG_MAN_ID);
  	if (tmp != ST_MAN_ID)
  		return -ENODEV;
  
  	/* lower temperaure registers always have bits 0-3 set to zero */
  	tmp = i2c_smbus_read_byte_data(new_client, STTS751_REG_TEMP_L);
  	if (tmp & 0xf)
  		return -ENODEV;
  
  	tmp = i2c_smbus_read_byte_data(new_client, STTS751_REG_HLIM_L);
  	if (tmp & 0xf)
  		return -ENODEV;
  
  	tmp = i2c_smbus_read_byte_data(new_client, STTS751_REG_LLIM_L);
  	if (tmp & 0xf)
  		return -ENODEV;
  
  	/* smbus timeout register always have bits 0-7 set to zero */
  	tmp = i2c_smbus_read_byte_data(new_client, STTS751_REG_SMBUS_TO);
  	if (tmp & 0x7f)
  		return -ENODEV;
  
  	tmp = i2c_smbus_read_byte_data(new_client, STTS751_REG_PROD_ID);
  
  	switch (tmp) {
  	case STTS751_0_PROD_ID:
  		name = "STTS751-0";
  		break;
  	case STTS751_1_PROD_ID:
  		name = "STTS751-1";
  		break;
  	default:
  		return -ENODEV;
  	}
  	dev_dbg(&new_client->dev, "Chip %s detected", name);
  
  	strlcpy(info->type, stts751_id[0].name, I2C_NAME_SIZE);
  	return 0;
  }
  
  static int stts751_read_chip_config(struct stts751_priv *priv)
  {
  	int ret;
  	int tmp;
  
  	ret = i2c_smbus_read_byte_data(priv->client, STTS751_REG_CONF);
  	if (ret < 0)
  		return ret;
  	priv->config = ret;
  	priv->res = (ret & STTS751_CONF_RES_MASK) >> STTS751_CONF_RES_SHIFT;
  
  	ret = i2c_smbus_read_byte_data(priv->client, STTS751_REG_RATE);
  	if (ret < 0)
  		return ret;
  	if (ret >= ARRAY_SIZE(stts751_intervals)) {
  		dev_err(priv->dev, "Unrecognized conversion rate 0x%x\n", ret);
  		return -ENODEV;
  	}
  	priv->interval = ret;
  
  	ret = stts751_read_reg16(priv, &priv->event_max,
  				 STTS751_REG_HLIM_H, STTS751_REG_HLIM_L);
  	if (ret)
  		return ret;
  
  	ret = stts751_read_reg16(priv, &priv->event_min,
  				 STTS751_REG_LLIM_H, STTS751_REG_LLIM_L);
  	if (ret)
  		return ret;
  
  	ret = stts751_read_reg8(priv, &priv->therm, STTS751_REG_TLIM);
  	if (ret)
  		return ret;
  
  	ret = stts751_read_reg8(priv, &tmp, STTS751_REG_HYST);
  	if (ret)
  		return ret;
  	priv->hyst = priv->therm - tmp;
  
  	return 0;
  }
  
  static SENSOR_DEVICE_ATTR_RO(temp1_input, input, 0);
  static SENSOR_DEVICE_ATTR_RW(temp1_min, min, 0);
  static SENSOR_DEVICE_ATTR_RW(temp1_max, max, 0);
  static SENSOR_DEVICE_ATTR_RO(temp1_min_alarm, min_alarm, 0);
  static SENSOR_DEVICE_ATTR_RO(temp1_max_alarm, max_alarm, 0);
  static SENSOR_DEVICE_ATTR_RW(temp1_crit, therm, 0);
  static SENSOR_DEVICE_ATTR_RW(temp1_crit_hyst, hyst, 0);
  static SENSOR_DEVICE_ATTR_RO(temp1_crit_alarm, therm_trip, 0);
  static SENSOR_DEVICE_ATTR_RW(update_interval, interval, 0);
  
  static struct attribute *stts751_attrs[] = {
  	&sensor_dev_attr_temp1_input.dev_attr.attr,
  	&sensor_dev_attr_temp1_min.dev_attr.attr,
  	&sensor_dev_attr_temp1_max.dev_attr.attr,
  	&sensor_dev_attr_temp1_min_alarm.dev_attr.attr,
  	&sensor_dev_attr_temp1_max_alarm.dev_attr.attr,
  	&sensor_dev_attr_temp1_crit.dev_attr.attr,
  	&sensor_dev_attr_temp1_crit_hyst.dev_attr.attr,
  	&sensor_dev_attr_temp1_crit_alarm.dev_attr.attr,
  	&sensor_dev_attr_update_interval.dev_attr.attr,
  	NULL
  };
  ATTRIBUTE_GROUPS(stts751);
  
  static int stts751_probe(struct i2c_client *client,
  			 const struct i2c_device_id *id)
  {
  	struct stts751_priv *priv;
  	int ret;
  	bool smbus_nto;
  	int rev_id;
  
  	priv = devm_kzalloc(&client->dev, sizeof(*priv), GFP_KERNEL);
  	if (!priv)
  		return -ENOMEM;
  
  	priv->client = client;
  	priv->notify_max = true;
  	priv->notify_min = true;
  	i2c_set_clientdata(client, priv);
  	mutex_init(&priv->access_lock);
  
  	if (device_property_present(&client->dev,
  				    "smbus-timeout-disable")) {
  		smbus_nto = device_property_read_bool(&client->dev,
  						      "smbus-timeout-disable");
  
  		ret = i2c_smbus_write_byte_data(client,	STTS751_REG_SMBUS_TO,
  						smbus_nto ? 0 : 0x80);
  		if (ret)
  			return ret;
  	}
  
  	rev_id = i2c_smbus_read_byte_data(client, STTS751_REG_REV_ID);
  	if (rev_id < 0)
  		return -ENODEV;
  	if (rev_id != 0x1) {
  		dev_dbg(&client->dev, "Chip revision 0x%x is untested\n",
  			rev_id);
  	}
  
  	ret = stts751_read_chip_config(priv);
  	if (ret)
  		return ret;
  
  	priv->config &= ~(STTS751_CONF_STOP | STTS751_CONF_EVENT_DIS);
  	ret = i2c_smbus_write_byte_data(client,	STTS751_REG_CONF, priv->config);
  	if (ret)
  		return ret;
  
  	priv->dev = devm_hwmon_device_register_with_groups(&client->dev,
  							client->name, priv,
  							stts751_groups);
  	return PTR_ERR_OR_ZERO(priv->dev);
  }
  
  MODULE_DEVICE_TABLE(i2c, stts751_id);
  
  static struct i2c_driver stts751_driver = {
  	.class		= I2C_CLASS_HWMON,
  	.driver = {
  		.name	= DEVNAME,
  		.of_match_table = of_match_ptr(stts751_of_match),
  	},
  	.probe		= stts751_probe,
  	.id_table	= stts751_id,
  	.detect		= stts751_detect,
  	.alert		= stts751_alert,
  	.address_list	= normal_i2c,
  };
  
  module_i2c_driver(stts751_driver);
  
  MODULE_AUTHOR("Andrea Merello <andrea.merello@gmail.com>");
  MODULE_DESCRIPTION("STTS751 sensor driver");
  MODULE_LICENSE("GPL");
  