/*
   * Driver for Linear Technology LTC4151 High Voltage I2C Current
   * and Voltage Monitor
   *
   * Copyright (C) 2011 AppearTV AS
   *
   * Derived from:
   *
   *  Driver for Linear Technology LTC4261 I2C Negative Voltage Hot
   *  Swap Controller
   *  Copyright (C) 2010 Ericsson AB.
   *
   * Datasheet: http://www.linear.com/docs/Datasheet/4151fc.pdf
   *
   * 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/kernel.h>
  #include <linux/module.h>
  #include <linux/init.h>
  #include <linux/err.h>
  #include <linux/slab.h>
  #include <linux/i2c.h>
  #include <linux/hwmon.h>
  #include <linux/hwmon-sysfs.h>
  #include <linux/jiffies.h>
  
  /* chip registers */
  #define LTC4151_SENSE_H	0x00
  #define LTC4151_SENSE_L	0x01
  #define LTC4151_VIN_H	0x02
  #define LTC4151_VIN_L	0x03
  #define LTC4151_ADIN_H	0x04
  #define LTC4151_ADIN_L	0x05
  
  struct ltc4151_data {
  	struct device *hwmon_dev;
  
  	struct mutex update_lock;
  	bool valid;
  	unsigned long last_updated; /* in jiffies */
  
  	/* Registers */
  	u8 regs[6];
  };
  
  static struct ltc4151_data *ltc4151_update_device(struct device *dev)
  {
  	struct i2c_client *client = to_i2c_client(dev);
  	struct ltc4151_data *data = i2c_get_clientdata(client);
  	struct ltc4151_data *ret = data;
  
  	mutex_lock(&data->update_lock);
  
  	/*
  	 * The chip's A/D updates 6 times per second
  	 * (Conversion Rate 6 - 9 Hz)
  	 */
  	if (time_after(jiffies, data->last_updated + HZ / 6) || !data->valid) {
  		int i;
  
  		dev_dbg(&client->dev, "Starting ltc4151 update
  ");
  
  		/* Read all registers */
  		for (i = 0; i < ARRAY_SIZE(data->regs); i++) {
  			int val;
  
  			val = i2c_smbus_read_byte_data(client, i);
  			if (unlikely(val < 0)) {
  				dev_dbg(dev,
  					"Failed to read ADC value: error %d
  ",
  					val);
  				ret = ERR_PTR(val);
  				goto abort;
  			}
  			data->regs[i] = val;
  		}
  		data->last_updated = jiffies;
  		data->valid = 1;
  	}
  abort:
  	mutex_unlock(&data->update_lock);
  	return ret;
  }
  
  /* Return the voltage from the given register in mV */
  static int ltc4151_get_value(struct ltc4151_data *data, u8 reg)
  {
  	u32 val;
  
  	val = (data->regs[reg] << 4) + (data->regs[reg + 1] >> 4);
  
  	switch (reg) {
  	case LTC4151_ADIN_H:
  		/* 500uV resolution. Convert to mV. */
  		val = val * 500 / 1000;
  		break;
  	case LTC4151_SENSE_H:
  		/*
  		 * 20uV resolution. Convert to current as measured with
  		 * an 1 mOhm sense resistor, in mA.
  		 */
  		val = val * 20;
  		break;
  	case LTC4151_VIN_H:
  		/* 25 mV per increment */
  		val = val * 25;
  		break;
  	default:
  		/* If we get here, the developer messed up */
  		WARN_ON_ONCE(1);
  		val = 0;
  		break;
  	}
  
  	return val;
  }
  
  static ssize_t ltc4151_show_value(struct device *dev,
  				  struct device_attribute *da, char *buf)
  {
  	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
  	struct ltc4151_data *data = ltc4151_update_device(dev);
  	int value;
  
  	if (IS_ERR(data))
  		return PTR_ERR(data);
  
  	value = ltc4151_get_value(data, attr->index);
  	return snprintf(buf, PAGE_SIZE, "%d
  ", value);
  }
  
  /*
   * Input voltages.
   */
  static SENSOR_DEVICE_ATTR(in1_input, S_IRUGO, ltc4151_show_value, NULL,
  			  LTC4151_VIN_H);
  static SENSOR_DEVICE_ATTR(in2_input, S_IRUGO, ltc4151_show_value, NULL,
  			  LTC4151_ADIN_H);
  
  /* Currents (via sense resistor) */
  static SENSOR_DEVICE_ATTR(curr1_input, S_IRUGO, ltc4151_show_value, NULL,
  			  LTC4151_SENSE_H);
  
  /*
   * Finally, construct an array of pointers to members of the above objects,
   * as required for sysfs_create_group()
   */
  static struct attribute *ltc4151_attributes[] = {
  	&sensor_dev_attr_in1_input.dev_attr.attr,
  	&sensor_dev_attr_in2_input.dev_attr.attr,
  
  	&sensor_dev_attr_curr1_input.dev_attr.attr,
  
  	NULL,
  };
  
  static const struct attribute_group ltc4151_group = {
  	.attrs = ltc4151_attributes,
  };
  
  static int ltc4151_probe(struct i2c_client *client,
  			 const struct i2c_device_id *id)
  {
  	struct i2c_adapter *adapter = client->adapter;
  	struct ltc4151_data *data;
  	int ret;
  
  	if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA))
  		return -ENODEV;
  
  	data = devm_kzalloc(&client->dev, sizeof(*data), GFP_KERNEL);
  	if (!data)
  		return -ENOMEM;
  
  	i2c_set_clientdata(client, data);
  	mutex_init(&data->update_lock);
  
  	/* Register sysfs hooks */
  	ret = sysfs_create_group(&client->dev.kobj, &ltc4151_group);
  	if (ret)
  		return ret;
  
  	data->hwmon_dev = hwmon_device_register(&client->dev);
  	if (IS_ERR(data->hwmon_dev)) {
  		ret = PTR_ERR(data->hwmon_dev);
  		goto out_hwmon_device_register;
  	}
  
  	return 0;
  
  out_hwmon_device_register:
  	sysfs_remove_group(&client->dev.kobj, &ltc4151_group);
  	return ret;
  }
  
  static int ltc4151_remove(struct i2c_client *client)
  {
  	struct ltc4151_data *data = i2c_get_clientdata(client);
  
  	hwmon_device_unregister(data->hwmon_dev);
  	sysfs_remove_group(&client->dev.kobj, &ltc4151_group);
  
  	return 0;
  }
  
  static const struct i2c_device_id ltc4151_id[] = {
  	{ "ltc4151", 0 },
  	{ }
  };
  MODULE_DEVICE_TABLE(i2c, ltc4151_id);
  
  /* This is the driver that will be inserted */
  static struct i2c_driver ltc4151_driver = {
  	.driver = {
  		.name	= "ltc4151",
  	},
  	.probe		= ltc4151_probe,
  	.remove		= ltc4151_remove,
  	.id_table	= ltc4151_id,
  };
  
  module_i2c_driver(ltc4151_driver);
  
  MODULE_AUTHOR("Per Dalen <per.dalen@appeartv.com>");
  MODULE_DESCRIPTION("LTC4151 driver");
  MODULE_LICENSE("GPL");