/*
   * lm92 - Hardware monitoring driver
   * Copyright (C) 2005-2008  Jean Delvare <jdelvare@suse.de>
   *
   * Based on the lm90 driver, with some ideas taken from the lm_sensors
   * lm92 driver as well.
   *
   * The LM92 is a sensor chip made by National Semiconductor. It reports
   * its own temperature with a 0.0625 deg resolution and a 0.33 deg
   * accuracy. Complete datasheet can be obtained from National's website
   * at:
   *   http://www.national.com/pf/LM/LM92.html
   *
   * This driver also supports the MAX6635 sensor chip made by Maxim.
   * This chip is compatible with the LM92, but has a lesser accuracy
   * (1.0 deg). Complete datasheet can be obtained from Maxim's website
   * at:
   *   http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3074
   *
   * Since the LM92 was the first chipset supported by this driver, most
   * comments will refer to this chipset, but are actually general and
   * concern all supported chipsets, unless mentioned otherwise.
   *
   * Support could easily be added for the National Semiconductor LM76
   * and Maxim MAX6633 and MAX6634 chips, which are mostly compatible
   * with the LM92.
   *
   * 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.
   *
   * You should have received a copy of the GNU General Public License
   * along with this program; if not, write to the Free Software
   * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
   */
  
  #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/mutex.h>
  #include <linux/jiffies.h>
  
  /*
   * The LM92 and MAX6635 have 2 two-state pins for address selection,
   * resulting in 4 possible addresses.
   */
  static const unsigned short normal_i2c[] = { 0x48, 0x49, 0x4a, 0x4b,
  						I2C_CLIENT_END };
  
  /* The LM92 registers */
  #define LM92_REG_CONFIG			0x01 /* 8-bit, RW */
  #define LM92_REG_TEMP			0x00 /* 16-bit, RO */
  #define LM92_REG_TEMP_HYST		0x02 /* 16-bit, RW */
  #define LM92_REG_TEMP_CRIT		0x03 /* 16-bit, RW */
  #define LM92_REG_TEMP_LOW		0x04 /* 16-bit, RW */
  #define LM92_REG_TEMP_HIGH		0x05 /* 16-bit, RW */
  #define LM92_REG_MAN_ID			0x07 /* 16-bit, RO, LM92 only */
  
  /*
   * The LM92 uses signed 13-bit values with LSB = 0.0625 degree Celsius,
   * left-justified in 16-bit registers. No rounding is done, with such
   * a resolution it's just not worth it. Note that the MAX6635 doesn't
   * make use of the 4 lower bits for limits (i.e. effective resolution
   * for limits is 1 degree Celsius).
   */
  static inline int TEMP_FROM_REG(s16 reg)
  {
  	return reg / 8 * 625 / 10;
  }
  
  static inline s16 TEMP_TO_REG(int val)
  {
  	if (val <= -60000)
  		return -60000 * 10 / 625 * 8;
  	if (val >= 160000)
  		return 160000 * 10 / 625 * 8;
  	return val * 10 / 625 * 8;
  }
  
  /* Alarm flags are stored in the 3 LSB of the temperature register */
  static inline u8 ALARMS_FROM_REG(s16 reg)
  {
  	return reg & 0x0007;
  }
  
  /* Driver data (common to all clients) */
  static struct i2c_driver lm92_driver;
  
  /* Client data (each client gets its own) */
  struct lm92_data {
  	struct device *hwmon_dev;
  	struct mutex update_lock;
  	char valid; /* zero until following fields are valid */
  	unsigned long last_updated; /* in jiffies */
  
  	/* registers values */
  	s16 temp1_input, temp1_crit, temp1_min, temp1_max, temp1_hyst;
  };
  
  
  /*
   * Sysfs attributes and callback functions
   */
  
  static struct lm92_data *lm92_update_device(struct device *dev)
  {
  	struct i2c_client *client = to_i2c_client(dev);
  	struct lm92_data *data = i2c_get_clientdata(client);
  
  	mutex_lock(&data->update_lock);
  
  	if (time_after(jiffies, data->last_updated + HZ)
  	 || !data->valid) {
  		dev_dbg(&client->dev, "Updating lm92 data
  ");
  		data->temp1_input = i2c_smbus_read_word_swapped(client,
  				    LM92_REG_TEMP);
  		data->temp1_hyst = i2c_smbus_read_word_swapped(client,
  				    LM92_REG_TEMP_HYST);
  		data->temp1_crit = i2c_smbus_read_word_swapped(client,
  				    LM92_REG_TEMP_CRIT);
  		data->temp1_min = i2c_smbus_read_word_swapped(client,
  				    LM92_REG_TEMP_LOW);
  		data->temp1_max = i2c_smbus_read_word_swapped(client,
  				    LM92_REG_TEMP_HIGH);
  
  		data->last_updated = jiffies;
  		data->valid = 1;
  	}
  
  	mutex_unlock(&data->update_lock);
  
  	return data;
  }
  
  #define show_temp(value) \
  static ssize_t show_##value(struct device *dev, struct device_attribute *attr, \
  			    char *buf) \
  { \
  	struct lm92_data *data = lm92_update_device(dev); \
  	return sprintf(buf, "%d
  ", TEMP_FROM_REG(data->value)); \
  }
  show_temp(temp1_input);
  show_temp(temp1_crit);
  show_temp(temp1_min);
  show_temp(temp1_max);
  
  #define set_temp(value, reg) \
  static ssize_t set_##value(struct device *dev, struct device_attribute *attr, \
  			   const char *buf, \
  	size_t count) \
  { \
  	struct i2c_client *client = to_i2c_client(dev); \
  	struct lm92_data *data = i2c_get_clientdata(client); \
  	long val; \
  	int err = kstrtol(buf, 10, &val); \
  	if (err) \
  		return err; \
  \
  	mutex_lock(&data->update_lock); \
  	data->value = TEMP_TO_REG(val); \
  	i2c_smbus_write_word_swapped(client, reg, data->value); \
  	mutex_unlock(&data->update_lock); \
  	return count; \
  }
  set_temp(temp1_crit, LM92_REG_TEMP_CRIT);
  set_temp(temp1_min, LM92_REG_TEMP_LOW);
  set_temp(temp1_max, LM92_REG_TEMP_HIGH);
  
  static ssize_t show_temp1_crit_hyst(struct device *dev,
  				    struct device_attribute *attr, char *buf)
  {
  	struct lm92_data *data = lm92_update_device(dev);
  	return sprintf(buf, "%d
  ", TEMP_FROM_REG(data->temp1_crit)
  		       - TEMP_FROM_REG(data->temp1_hyst));
  }
  static ssize_t show_temp1_max_hyst(struct device *dev,
  				   struct device_attribute *attr, char *buf)
  {
  	struct lm92_data *data = lm92_update_device(dev);
  	return sprintf(buf, "%d
  ", TEMP_FROM_REG(data->temp1_max)
  		       - TEMP_FROM_REG(data->temp1_hyst));
  }
  static ssize_t show_temp1_min_hyst(struct device *dev,
  				   struct device_attribute *attr, char *buf)
  {
  	struct lm92_data *data = lm92_update_device(dev);
  	return sprintf(buf, "%d
  ", TEMP_FROM_REG(data->temp1_min)
  		       + TEMP_FROM_REG(data->temp1_hyst));
  }
  
  static ssize_t set_temp1_crit_hyst(struct device *dev,
  				   struct device_attribute *attr,
  				   const char *buf, size_t count)
  {
  	struct i2c_client *client = to_i2c_client(dev);
  	struct lm92_data *data = i2c_get_clientdata(client);
  	long val;
  	int err;
  
  	err = kstrtol(buf, 10, &val);
  	if (err)
  		return err;
  
  	mutex_lock(&data->update_lock);
  	data->temp1_hyst = TEMP_FROM_REG(data->temp1_crit) - val;
  	i2c_smbus_write_word_swapped(client, LM92_REG_TEMP_HYST,
  				     TEMP_TO_REG(data->temp1_hyst));
  	mutex_unlock(&data->update_lock);
  	return count;
  }
  
  static ssize_t show_alarms(struct device *dev, struct device_attribute *attr,
  			   char *buf)
  {
  	struct lm92_data *data = lm92_update_device(dev);
  	return sprintf(buf, "%d
  ", ALARMS_FROM_REG(data->temp1_input));
  }
  
  static ssize_t show_alarm(struct device *dev, struct device_attribute *attr,
  			  char *buf)
  {
  	int bitnr = to_sensor_dev_attr(attr)->index;
  	struct lm92_data *data = lm92_update_device(dev);
  	return sprintf(buf, "%d
  ", (data->temp1_input >> bitnr) & 1);
  }
  
  static DEVICE_ATTR(temp1_input, S_IRUGO, show_temp1_input, NULL);
  static DEVICE_ATTR(temp1_crit, S_IWUSR | S_IRUGO, show_temp1_crit,
  	set_temp1_crit);
  static DEVICE_ATTR(temp1_crit_hyst, S_IWUSR | S_IRUGO, show_temp1_crit_hyst,
  	set_temp1_crit_hyst);
  static DEVICE_ATTR(temp1_min, S_IWUSR | S_IRUGO, show_temp1_min,
  	set_temp1_min);
  static DEVICE_ATTR(temp1_min_hyst, S_IRUGO, show_temp1_min_hyst, NULL);
  static DEVICE_ATTR(temp1_max, S_IWUSR | S_IRUGO, show_temp1_max,
  	set_temp1_max);
  static DEVICE_ATTR(temp1_max_hyst, S_IRUGO, show_temp1_max_hyst, NULL);
  static DEVICE_ATTR(alarms, S_IRUGO, show_alarms, NULL);
  static SENSOR_DEVICE_ATTR(temp1_crit_alarm, S_IRUGO, show_alarm, NULL, 2);
  static SENSOR_DEVICE_ATTR(temp1_min_alarm, S_IRUGO, show_alarm, NULL, 0);
  static SENSOR_DEVICE_ATTR(temp1_max_alarm, S_IRUGO, show_alarm, NULL, 1);
  
  
  /*
   * Detection and registration
   */
  
  static void lm92_init_client(struct i2c_client *client)
  {
  	u8 config;
  
  	/* Start the conversions if needed */
  	config = i2c_smbus_read_byte_data(client, LM92_REG_CONFIG);
  	if (config & 0x01)
  		i2c_smbus_write_byte_data(client, LM92_REG_CONFIG,
  					  config & 0xFE);
  }
  
  /*
   * The MAX6635 has no identification register, so we have to use tricks
   * to identify it reliably. This is somewhat slow.
   * Note that we do NOT rely on the 2 MSB of the configuration register
   * always reading 0, as suggested by the datasheet, because it was once
   * reported not to be true.
   */
  static int max6635_check(struct i2c_client *client)
  {
  	u16 temp_low, temp_high, temp_hyst, temp_crit;
  	u8 conf;
  	int i;
  
  	/*
  	 * No manufacturer ID register, so a read from this address will
  	 * always return the last read value.
  	 */
  	temp_low = i2c_smbus_read_word_data(client, LM92_REG_TEMP_LOW);
  	if (i2c_smbus_read_word_data(client, LM92_REG_MAN_ID) != temp_low)
  		return 0;
  	temp_high = i2c_smbus_read_word_data(client, LM92_REG_TEMP_HIGH);
  	if (i2c_smbus_read_word_data(client, LM92_REG_MAN_ID) != temp_high)
  		return 0;
  
  	/* Limits are stored as integer values (signed, 9-bit). */
  	if ((temp_low & 0x7f00) || (temp_high & 0x7f00))
  		return 0;
  	temp_hyst = i2c_smbus_read_word_data(client, LM92_REG_TEMP_HYST);
  	temp_crit = i2c_smbus_read_word_data(client, LM92_REG_TEMP_CRIT);
  	if ((temp_hyst & 0x7f00) || (temp_crit & 0x7f00))
  		return 0;
  
  	/*
  	 * Registers addresses were found to cycle over 16-byte boundaries.
  	 * We don't test all registers with all offsets so as to save some
  	 * reads and time, but this should still be sufficient to dismiss
  	 * non-MAX6635 chips.
  	 */
  	conf = i2c_smbus_read_byte_data(client, LM92_REG_CONFIG);
  	for (i = 16; i < 96; i *= 2) {
  		if (temp_hyst != i2c_smbus_read_word_data(client,
  				 LM92_REG_TEMP_HYST + i - 16)
  		 || temp_crit != i2c_smbus_read_word_data(client,
  				 LM92_REG_TEMP_CRIT + i)
  		 || temp_low != i2c_smbus_read_word_data(client,
  				LM92_REG_TEMP_LOW + i + 16)
  		 || temp_high != i2c_smbus_read_word_data(client,
  				 LM92_REG_TEMP_HIGH + i + 32)
  		 || conf != i2c_smbus_read_byte_data(client,
  			    LM92_REG_CONFIG + i))
  			return 0;
  	}
  
  	return 1;
  }
  
  static struct attribute *lm92_attributes[] = {
  	&dev_attr_temp1_input.attr,
  	&dev_attr_temp1_crit.attr,
  	&dev_attr_temp1_crit_hyst.attr,
  	&dev_attr_temp1_min.attr,
  	&dev_attr_temp1_min_hyst.attr,
  	&dev_attr_temp1_max.attr,
  	&dev_attr_temp1_max_hyst.attr,
  	&dev_attr_alarms.attr,
  	&sensor_dev_attr_temp1_crit_alarm.dev_attr.attr,
  	&sensor_dev_attr_temp1_min_alarm.dev_attr.attr,
  	&sensor_dev_attr_temp1_max_alarm.dev_attr.attr,
  	NULL
  };
  
  static const struct attribute_group lm92_group = {
  	.attrs = lm92_attributes,
  };
  
  /* Return 0 if detection is successful, -ENODEV otherwise */
  static int lm92_detect(struct i2c_client *new_client,
  		       struct i2c_board_info *info)
  {
  	struct i2c_adapter *adapter = new_client->adapter;
  	u8 config;
  	u16 man_id;
  
  	if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA
  					    | I2C_FUNC_SMBUS_WORD_DATA))
  		return -ENODEV;
  
  	config = i2c_smbus_read_byte_data(new_client, LM92_REG_CONFIG);
  	man_id = i2c_smbus_read_word_data(new_client, LM92_REG_MAN_ID);
  
  	if ((config & 0xe0) == 0x00 && man_id == 0x0180)
  		pr_info("lm92: Found National Semiconductor LM92 chip
  ");
  	else if (max6635_check(new_client))
  		pr_info("lm92: Found Maxim MAX6635 chip
  ");
  	else
  		return -ENODEV;
  
  	strlcpy(info->type, "lm92", I2C_NAME_SIZE);
  
  	return 0;
  }
  
  static int lm92_probe(struct i2c_client *new_client,
  		      const struct i2c_device_id *id)
  {
  	struct lm92_data *data;
  	int err;
  
  	data = devm_kzalloc(&new_client->dev, sizeof(struct lm92_data),
  			    GFP_KERNEL);
  	if (!data)
  		return -ENOMEM;
  
  	i2c_set_clientdata(new_client, data);
  	data->valid = 0;
  	mutex_init(&data->update_lock);
  
  	/* Initialize the chipset */
  	lm92_init_client(new_client);
  
  	/* Register sysfs hooks */
  	err = sysfs_create_group(&new_client->dev.kobj, &lm92_group);
  	if (err)
  		return err;
  
  	data->hwmon_dev = hwmon_device_register(&new_client->dev);
  	if (IS_ERR(data->hwmon_dev)) {
  		err = PTR_ERR(data->hwmon_dev);
  		goto exit_remove;
  	}
  
  	return 0;
  
  exit_remove:
  	sysfs_remove_group(&new_client->dev.kobj, &lm92_group);
  	return err;
  }
  
  static int lm92_remove(struct i2c_client *client)
  {
  	struct lm92_data *data = i2c_get_clientdata(client);
  
  	hwmon_device_unregister(data->hwmon_dev);
  	sysfs_remove_group(&client->dev.kobj, &lm92_group);
  
  	return 0;
  }
  
  
  /*
   * Module and driver stuff
   */
  
  static const struct i2c_device_id lm92_id[] = {
  	{ "lm92", 0 },
  	/* max6635 could be added here */
  	{ }
  };
  MODULE_DEVICE_TABLE(i2c, lm92_id);
  
  static struct i2c_driver lm92_driver = {
  	.class		= I2C_CLASS_HWMON,
  	.driver = {
  		.name	= "lm92",
  	},
  	.probe		= lm92_probe,
  	.remove		= lm92_remove,
  	.id_table	= lm92_id,
  	.detect		= lm92_detect,
  	.address_list	= normal_i2c,
  };
  
  module_i2c_driver(lm92_driver);
  
  MODULE_AUTHOR("Jean Delvare <jdelvare@suse.de>");
  MODULE_DESCRIPTION("LM92/MAX6635 driver");
  MODULE_LICENSE("GPL");