// SPDX-License-Identifier: GPL-2.0-or-later

  /* Sensirion SHTC1 humidity and temperature sensor driver
   *
   * Copyright (C) 2014 Sensirion AG, Switzerland
   * Author: Johannes Winkelmann <johannes.winkelmann@sensirion.com>

   */
  
  #include <linux/module.h>
  #include <linux/init.h>
  #include <linux/slab.h>
  #include <linux/i2c.h>
  #include <linux/hwmon.h>
  #include <linux/hwmon-sysfs.h>
  #include <linux/err.h>
  #include <linux/delay.h>
  #include <linux/platform_data/shtc1.h>

  #include <linux/of.h>

  
  /* commands (high precision mode) */
  static const unsigned char shtc1_cmd_measure_blocking_hpm[]    = { 0x7C, 0xA2 };
  static const unsigned char shtc1_cmd_measure_nonblocking_hpm[] = { 0x78, 0x66 };
  
  /* commands (low precision mode) */
  static const unsigned char shtc1_cmd_measure_blocking_lpm[]    = { 0x64, 0x58 };
  static const unsigned char shtc1_cmd_measure_nonblocking_lpm[] = { 0x60, 0x9c };
  
  /* command for reading the ID register */

  static const unsigned char shtc1_cmd_read_id_reg[]             = { 0xef, 0xc8 };

  /*
   * constants for reading the ID register
   * SHTC1: 0x0007 with mask 0x003f
   * SHTW1: 0x0007 with mask 0x003f
   * SHTC3: 0x0807 with mask 0x083f
   */
  #define SHTC3_ID      0x0807
  #define SHTC3_ID_MASK 0x083f
  #define SHTC1_ID      0x0007
  #define SHTC1_ID_MASK 0x003f

  
  /* delays for non-blocking i2c commands, both in us */
  #define SHTC1_NONBLOCKING_WAIT_TIME_HPM  14400
  #define SHTC1_NONBLOCKING_WAIT_TIME_LPM   1000

  #define SHTC3_NONBLOCKING_WAIT_TIME_HPM  12100
  #define SHTC3_NONBLOCKING_WAIT_TIME_LPM    800

  
  #define SHTC1_CMD_LENGTH      2
  #define SHTC1_RESPONSE_LENGTH 6

  enum shtcx_chips {
  	shtc1,
  	shtc3,
  };

  struct shtc1_data {
  	struct i2c_client *client;
  	struct mutex update_lock;
  	bool valid;
  	unsigned long last_updated; /* in jiffies */
  
  	const unsigned char *command;
  	unsigned int nonblocking_wait_time; /* in us */
  
  	struct shtc1_platform_data setup;

  	enum shtcx_chips chip;

  
  	int temperature; /* 1000 * temperature in dgr C */
  	int humidity; /* 1000 * relative humidity in %RH */
  };
  
  static int shtc1_update_values(struct i2c_client *client,
  			       struct shtc1_data *data,
  			       char *buf, int bufsize)
  {
  	int ret = i2c_master_send(client, data->command, SHTC1_CMD_LENGTH);
  	if (ret != SHTC1_CMD_LENGTH) {
  		dev_err(&client->dev, "failed to send command: %d
  ", ret);
  		return ret < 0 ? ret : -EIO;
  	}
  
  	/*
  	 * In blocking mode (clock stretching mode) the I2C bus
  	 * is blocked for other traffic, thus the call to i2c_master_recv()
  	 * will wait until the data is ready. For non blocking mode, we
  	 * have to wait ourselves.
  	 */
  	if (!data->setup.blocking_io)
  		usleep_range(data->nonblocking_wait_time,
  			     data->nonblocking_wait_time + 1000);
  
  	ret = i2c_master_recv(client, buf, bufsize);
  	if (ret != bufsize) {
  		dev_err(&client->dev, "failed to read values: %d
  ", ret);
  		return ret < 0 ? ret : -EIO;
  	}
  
  	return 0;
  }
  
  /* sysfs attributes */
  static struct shtc1_data *shtc1_update_client(struct device *dev)
  {
  	struct shtc1_data *data = dev_get_drvdata(dev);
  	struct i2c_client *client = data->client;
  	unsigned char buf[SHTC1_RESPONSE_LENGTH];
  	int val;
  	int ret = 0;
  
  	mutex_lock(&data->update_lock);
  
  	if (time_after(jiffies, data->last_updated + HZ / 10) || !data->valid) {
  		ret = shtc1_update_values(client, data, buf, sizeof(buf));
  		if (ret)
  			goto out;
  
  		/*
  		 * From datasheet:
  		 * T = -45 + 175 * ST / 2^16
  		 * RH = 100 * SRH / 2^16
  		 *
  		 * Adapted for integer fixed point (3 digit) arithmetic.
  		 */
  		val = be16_to_cpup((__be16 *)buf);
  		data->temperature = ((21875 * val) >> 13) - 45000;
  		val = be16_to_cpup((__be16 *)(buf + 3));
  		data->humidity = ((12500 * val) >> 13);
  
  		data->last_updated = jiffies;
  		data->valid = true;
  	}
  
  out:
  	mutex_unlock(&data->update_lock);
  
  	return ret == 0 ? data : ERR_PTR(ret);
  }
  
  static ssize_t temp1_input_show(struct device *dev,
  				struct device_attribute *attr,
  				char *buf)
  {
  	struct shtc1_data *data = shtc1_update_client(dev);
  	if (IS_ERR(data))
  		return PTR_ERR(data);
  
  	return sprintf(buf, "%d
  ", data->temperature);
  }
  
  static ssize_t humidity1_input_show(struct device *dev,
  				    struct device_attribute *attr, char *buf)
  {
  	struct shtc1_data *data = shtc1_update_client(dev);
  	if (IS_ERR(data))
  		return PTR_ERR(data);
  
  	return sprintf(buf, "%d
  ", data->humidity);
  }
  
  static DEVICE_ATTR_RO(temp1_input);
  static DEVICE_ATTR_RO(humidity1_input);
  
  static struct attribute *shtc1_attrs[] = {
  	&dev_attr_temp1_input.attr,
  	&dev_attr_humidity1_input.attr,
  	NULL
  };
  
  ATTRIBUTE_GROUPS(shtc1);
  
  static void shtc1_select_command(struct shtc1_data *data)
  {
  	if (data->setup.high_precision) {
  		data->command = data->setup.blocking_io ?
  				shtc1_cmd_measure_blocking_hpm :
  				shtc1_cmd_measure_nonblocking_hpm;

  		data->nonblocking_wait_time = (data->chip == shtc1) ?
  				SHTC1_NONBLOCKING_WAIT_TIME_HPM :
  				SHTC3_NONBLOCKING_WAIT_TIME_HPM;

  	} else {
  		data->command = data->setup.blocking_io ?
  				shtc1_cmd_measure_blocking_lpm :
  				shtc1_cmd_measure_nonblocking_lpm;

  		data->nonblocking_wait_time = (data->chip == shtc1) ?
  				SHTC1_NONBLOCKING_WAIT_TIME_LPM :
  				SHTC3_NONBLOCKING_WAIT_TIME_LPM;

  	}
  }

  static const struct i2c_device_id shtc1_id[];
  
  static int shtc1_probe(struct i2c_client *client)

  {
  	int ret;

  	u16 id_reg;
  	char id_reg_buf[2];

  	struct shtc1_data *data;
  	struct device *hwmon_dev;

  	enum shtcx_chips chip = i2c_match_id(shtc1_id, client)->driver_data;

  	struct i2c_adapter *adap = client->adapter;
  	struct device *dev = &client->dev;

  	struct device_node *np = dev->of_node;

  
  	if (!i2c_check_functionality(adap, I2C_FUNC_I2C)) {
  		dev_err(dev, "plain i2c transactions not supported
  ");
  		return -ENODEV;
  	}
  
  	ret = i2c_master_send(client, shtc1_cmd_read_id_reg, SHTC1_CMD_LENGTH);
  	if (ret != SHTC1_CMD_LENGTH) {
  		dev_err(dev, "could not send read_id_reg command: %d
  ", ret);
  		return ret < 0 ? ret : -ENODEV;
  	}

  	ret = i2c_master_recv(client, id_reg_buf, sizeof(id_reg_buf));
  	if (ret != sizeof(id_reg_buf)) {

  		dev_err(dev, "could not read ID register: %d
  ", ret);
  		return -ENODEV;
  	}

  
  	id_reg = be16_to_cpup((__be16 *)id_reg_buf);
  	if (chip == shtc3) {
  		if ((id_reg & SHTC3_ID_MASK) != SHTC3_ID) {
  			dev_err(dev, "SHTC3 ID register does not match
  ");
  			return -ENODEV;
  		}
  	} else if ((id_reg & SHTC1_ID_MASK) != SHTC1_ID) {
  		dev_err(dev, "SHTC1 ID register does not match
  ");

  		return -ENODEV;
  	}
  
  	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
  	if (!data)
  		return -ENOMEM;
  
  	data->setup.blocking_io = false;
  	data->setup.high_precision = true;
  	data->client = client;

  	data->chip = chip;

  	if (np) {
  		data->setup.blocking_io = of_property_read_bool(np, "sensirion,blocking-io");
  		data->setup.high_precision = !of_property_read_bool(np, "sensicon,low-precision");
  	} else {
  		if (client->dev.platform_data)
  			data->setup = *(struct shtc1_platform_data *)dev->platform_data;
  	}

  	shtc1_select_command(data);
  	mutex_init(&data->update_lock);
  
  	hwmon_dev = devm_hwmon_device_register_with_groups(dev,
  							   client->name,
  							   data,
  							   shtc1_groups);
  	if (IS_ERR(hwmon_dev))
  		dev_dbg(dev, "unable to register hwmon device
  ");
  
  	return PTR_ERR_OR_ZERO(hwmon_dev);
  }
  
  /* device ID table */
  static const struct i2c_device_id shtc1_id[] = {

  	{ "shtc1", shtc1 },
  	{ "shtw1", shtc1 },
  	{ "shtc3", shtc3 },

  	{ }
  };
  MODULE_DEVICE_TABLE(i2c, shtc1_id);

  static const struct of_device_id shtc1_of_match[] = {
  	{ .compatible = "sensirion,shtc1" },
  	{ .compatible = "sensirion,shtw1" },
  	{ .compatible = "sensirion,shtc3" },
  	{ }
  };
  MODULE_DEVICE_TABLE(of, shtc1_of_match);

  static struct i2c_driver shtc1_i2c_driver = {

  	.driver = {
  		.name = "shtc1",
  		.of_match_table = shtc1_of_match,
  	},

  	.probe_new    = shtc1_probe,

  	.id_table     = shtc1_id,
  };
  
  module_i2c_driver(shtc1_i2c_driver);
  
  MODULE_AUTHOR("Johannes Winkelmann <johannes.winkelmann@sensirion.com>");
  MODULE_DESCRIPTION("Sensirion SHTC1 humidity and temperature sensor driver");
  MODULE_LICENSE("GPL");