drivers/hwmon/ltc4245.c - kernel/msm-4.9 - Gitiles

 /*
  * Driver for Linear Technology LTC4245 I2C Multiple Supply Hot Swap Controller
  *
  * Copyright (C) 2008 Ira W. Snyder <iws@ovro.caltech.edu>
  *
  * 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; version 2 of the License.
  *
  * This driver is based on the ds1621 and ina209 drivers.
  *
  * Datasheet:
  * http://www.linear.com/pc/downloadDocument.do?navId=H0,C1,C1003,C1006,C1140,P19392,D13517
  */

 #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/i2c/ltc4245.h>

 /* Here are names of the chip's registers (a.k.a. commands) */
 enum ltc4245_cmd {
 	LTC4245_STATUS			= 0x00, /* readonly */
 	LTC4245_ALERT			= 0x01,
 	LTC4245_CONTROL			= 0x02,
 	LTC4245_ON			= 0x03,
 	LTC4245_FAULT1			= 0x04,
 	LTC4245_FAULT2			= 0x05,
 	LTC4245_GPIO			= 0x06,
 	LTC4245_ADCADR			= 0x07,

 	LTC4245_12VIN			= 0x10,
 	LTC4245_12VSENSE		= 0x11,
 	LTC4245_12VOUT			= 0x12,
 	LTC4245_5VIN			= 0x13,
 	LTC4245_5VSENSE			= 0x14,
 	LTC4245_5VOUT			= 0x15,
 	LTC4245_3VIN			= 0x16,
 	LTC4245_3VSENSE			= 0x17,
 	LTC4245_3VOUT			= 0x18,
 	LTC4245_VEEIN			= 0x19,
 	LTC4245_VEESENSE		= 0x1a,
 	LTC4245_VEEOUT			= 0x1b,
 	LTC4245_GPIOADC			= 0x1c,
 };

 struct ltc4245_data {
 	struct device *hwmon_dev;

 	struct mutex update_lock;
 	bool valid;
 	unsigned long last_updated; /* in jiffies */

 	/* Control registers */
 	u8 cregs[0x08];

 	/* Voltage registers */
 	u8 vregs[0x0d];

 	/* GPIO ADC registers */
 	bool use_extra_gpios;
 	int gpios[3];
 };

 /*
  * Update the readings from the GPIO pins. If the driver has been configured to
  * sample all GPIO's as analog voltages, a round-robin sampling method is used.
  * Otherwise, only the configured GPIO pin is sampled.
  *
  * LOCKING: must hold data->update_lock
  */
 static void ltc4245_update_gpios(struct device *dev)
 {
 	struct i2c_client *client = to_i2c_client(dev);
 	struct ltc4245_data *data = i2c_get_clientdata(client);
 	u8 gpio_curr, gpio_next, gpio_reg;
 	int i;

 	/* no extra gpio support, we're basically done */
 	if (!data->use_extra_gpios) {
 		data->gpios[0] = data->vregs[LTC4245_GPIOADC - 0x10];
 		return;
 	}

 	/*
 	 * If the last reading was too long ago, then we mark all old GPIO
 	 * readings as stale by setting them to -EAGAIN
 	 */
 	if (time_after(jiffies, data->last_updated + 5 * HZ)) {
 		dev_dbg(&client->dev, "Marking GPIOs invalid\n");
 		for (i = 0; i < ARRAY_SIZE(data->gpios); i++)
 			data->gpios[i] = -EAGAIN;
 	}

 	/*
 	 * Get the current GPIO pin
 	 *
 	 * The datasheet calls these GPIO[1-3], but we'll calculate the zero
 	 * based array index instead, and call them GPIO[0-2]. This is much
 	 * easier to think about.
 	 */
 	gpio_curr = (data->cregs[LTC4245_GPIO] & 0xc0) >> 6;
 	if (gpio_curr > 0)
 		gpio_curr -= 1;

 	/* Read the GPIO voltage from the GPIOADC register */
 	data->gpios[gpio_curr] = data->vregs[LTC4245_GPIOADC - 0x10];

 	/* Find the next GPIO pin to read */
 	gpio_next = (gpio_curr + 1) % ARRAY_SIZE(data->gpios);

 	/*
 	 * Calculate the correct setting for the GPIO register so it will
 	 * sample the next GPIO pin
 	 */
 	gpio_reg = (data->cregs[LTC4245_GPIO] & 0x3f) | ((gpio_next + 1) << 6);

 	/* Update the GPIO register */
 	i2c_smbus_write_byte_data(client, LTC4245_GPIO, gpio_reg);

 	/* Update saved data */
 	data->cregs[LTC4245_GPIO] = gpio_reg;
 }

 static struct ltc4245_data *ltc4245_update_device(struct device *dev)
 {
 	struct i2c_client *client = to_i2c_client(dev);
 	struct ltc4245_data *data = i2c_get_clientdata(client);
 	s32 val;
 	int i;

 	mutex_lock(&data->update_lock);

 	if (time_after(jiffies, data->last_updated + HZ) || !data->valid) {

 		dev_dbg(&client->dev, "Starting ltc4245 update\n");

 		/* Read control registers -- 0x00 to 0x07 */
 		for (i = 0; i < ARRAY_SIZE(data->cregs); i++) {
 			val = i2c_smbus_read_byte_data(client, i);
 			if (unlikely(val < 0))
 				data->cregs[i] = 0;
 			else
 				data->cregs[i] = val;
 		}

 		/* Read voltage registers -- 0x10 to 0x1c */
 		for (i = 0; i < ARRAY_SIZE(data->vregs); i++) {
 			val = i2c_smbus_read_byte_data(client, i+0x10);
 			if (unlikely(val < 0))
 				data->vregs[i] = 0;
 			else
 				data->vregs[i] = val;
 		}

 		/* Update GPIO readings */
 		ltc4245_update_gpios(dev);

 		data->last_updated = jiffies;
 		data->valid = 1;
 	}

 	mutex_unlock(&data->update_lock);

 	return data;
 }

 /* Return the voltage from the given register in millivolts */
 static int ltc4245_get_voltage(struct device *dev, u8 reg)
 {
 	struct ltc4245_data *data = ltc4245_update_device(dev);
 	const u8 regval = data->vregs[reg - 0x10];
 	u32 voltage = 0;

 	switch (reg) {
 	case LTC4245_12VIN:
 	case LTC4245_12VOUT:
 		voltage = regval * 55;
 		break;
 	case LTC4245_5VIN:
 	case LTC4245_5VOUT:
 		voltage = regval * 22;
 		break;
 	case LTC4245_3VIN:
 	case LTC4245_3VOUT:
 		voltage = regval * 15;
 		break;
 	case LTC4245_VEEIN:
 	case LTC4245_VEEOUT:
 		voltage = regval * -55;
 		break;
 	case LTC4245_GPIOADC:
 		voltage = regval * 10;
 		break;
 	default:
 		/* If we get here, the developer messed up */
 		WARN_ON_ONCE(1);
 		break;
 	}

 	return voltage;
 }

 /* Return the current in the given sense register in milliAmperes */
 static unsigned int ltc4245_get_current(struct device *dev, u8 reg)
 {
 	struct ltc4245_data *data = ltc4245_update_device(dev);
 	const u8 regval = data->vregs[reg - 0x10];
 	unsigned int voltage;
 	unsigned int curr;

 	/* The strange looking conversions that follow are fixed-point
 	 * math, since we cannot do floating point in the kernel.
 	 *
 	 * Step 1: convert sense register to microVolts
 	 * Step 2: convert voltage to milliAmperes
 	 *
 	 * If you play around with the V=IR equation, you come up with
 	 * the following: X uV / Y mOhm == Z mA
 	 *
 	 * With the resistors that are fractions of a milliOhm, we multiply
 	 * the voltage and resistance by 10, to shift the decimal point.
 	 * Now we can use the normal division operator again.
 	 */

 	switch (reg) {
 	case LTC4245_12VSENSE:
 		voltage = regval * 250; /* voltage in uV */
 		curr = voltage / 50; /* sense resistor 50 mOhm */
 		break;
 	case LTC4245_5VSENSE:
 		voltage = regval * 125; /* voltage in uV */
 		curr = (voltage * 10) / 35; /* sense resistor 3.5 mOhm */
 		break;
 	case LTC4245_3VSENSE:
 		voltage = regval * 125; /* voltage in uV */
 		curr = (voltage * 10) / 25; /* sense resistor 2.5 mOhm */
 		break;
 	case LTC4245_VEESENSE:
 		voltage = regval * 250; /* voltage in uV */
 		curr = voltage / 100; /* sense resistor 100 mOhm */
 		break;
 	default:
 		/* If we get here, the developer messed up */
 		WARN_ON_ONCE(1);
 		curr = 0;
 		break;
 	}

 	return curr;
 }

 static ssize_t ltc4245_show_voltage(struct device *dev,
 				    struct device_attribute *da,
 				    char *buf)
 {
 	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
 	const int voltage = ltc4245_get_voltage(dev, attr->index);

 	return snprintf(buf, PAGE_SIZE, "%d\n", voltage);
 }

 static ssize_t ltc4245_show_current(struct device *dev,
 				    struct device_attribute *da,
 				    char *buf)
 {
 	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
 	const unsigned int curr = ltc4245_get_current(dev, attr->index);

 	return snprintf(buf, PAGE_SIZE, "%u\n", curr);
 }

 static ssize_t ltc4245_show_power(struct device *dev,
 				  struct device_attribute *da,
 				  char *buf)
 {
 	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
 	const unsigned int curr = ltc4245_get_current(dev, attr->index);
 	const int output_voltage = ltc4245_get_voltage(dev, attr->index+1);

 	/* current in mA * voltage in mV == power in uW */
 	const unsigned int power = abs(output_voltage * curr);

 	return snprintf(buf, PAGE_SIZE, "%u\n", power);
 }

 static ssize_t ltc4245_show_alarm(struct device *dev,
 					  struct device_attribute *da,
 					  char *buf)
 {
 	struct sensor_device_attribute_2 *attr = to_sensor_dev_attr_2(da);
 	struct ltc4245_data *data = ltc4245_update_device(dev);
 	const u8 reg = data->cregs[attr->index];
 	const u32 mask = attr->nr;

 	return snprintf(buf, PAGE_SIZE, "%u\n", (reg & mask) ? 1 : 0);
 }

 static ssize_t ltc4245_show_gpio(struct device *dev,
 				 struct device_attribute *da,
 				 char *buf)
 {
 	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
 	struct ltc4245_data *data = ltc4245_update_device(dev);
 	int val = data->gpios[attr->index];

 	/* handle stale GPIO's */
 	if (val < 0)
 		return val;

 	/* Convert to millivolts and print */
 	return snprintf(buf, PAGE_SIZE, "%u\n", val * 10);
 }

 /* These macros are used below in constructing device attribute objects
  * for use with sysfs_create_group() to make a sysfs device file
  * for each register.
  */

 #define LTC4245_VOLTAGE(name, ltc4245_cmd_idx) \
 	static SENSOR_DEVICE_ATTR(name, S_IRUGO, \
 	ltc4245_show_voltage, NULL, ltc4245_cmd_idx)

 #define LTC4245_CURRENT(name, ltc4245_cmd_idx) \
 	static SENSOR_DEVICE_ATTR(name, S_IRUGO, \
 	ltc4245_show_current, NULL, ltc4245_cmd_idx)

 #define LTC4245_POWER(name, ltc4245_cmd_idx) \
 	static SENSOR_DEVICE_ATTR(name, S_IRUGO, \
 	ltc4245_show_power, NULL, ltc4245_cmd_idx)

 #define LTC4245_ALARM(name, mask, reg) \
 	static SENSOR_DEVICE_ATTR_2(name, S_IRUGO, \
 	ltc4245_show_alarm, NULL, (mask), reg)

 #define LTC4245_GPIO_VOLTAGE(name, gpio_num) \
 	static SENSOR_DEVICE_ATTR(name, S_IRUGO, \
 	ltc4245_show_gpio, NULL, gpio_num)

 /* Construct a sensor_device_attribute structure for each register */

 /* Input voltages */
 LTC4245_VOLTAGE(in1_input,			LTC4245_12VIN);
 LTC4245_VOLTAGE(in2_input,			LTC4245_5VIN);
 LTC4245_VOLTAGE(in3_input,			LTC4245_3VIN);
 LTC4245_VOLTAGE(in4_input,			LTC4245_VEEIN);

 /* Input undervoltage alarms */
 LTC4245_ALARM(in1_min_alarm,	(1 << 0),	LTC4245_FAULT1);
 LTC4245_ALARM(in2_min_alarm,	(1 << 1),	LTC4245_FAULT1);
 LTC4245_ALARM(in3_min_alarm,	(1 << 2),	LTC4245_FAULT1);
 LTC4245_ALARM(in4_min_alarm,	(1 << 3),	LTC4245_FAULT1);

 /* Currents (via sense resistor) */
 LTC4245_CURRENT(curr1_input,			LTC4245_12VSENSE);
 LTC4245_CURRENT(curr2_input,			LTC4245_5VSENSE);
 LTC4245_CURRENT(curr3_input,			LTC4245_3VSENSE);
 LTC4245_CURRENT(curr4_input,			LTC4245_VEESENSE);

 /* Overcurrent alarms */
 LTC4245_ALARM(curr1_max_alarm,	(1 << 4),	LTC4245_FAULT1);
 LTC4245_ALARM(curr2_max_alarm,	(1 << 5),	LTC4245_FAULT1);
 LTC4245_ALARM(curr3_max_alarm,	(1 << 6),	LTC4245_FAULT1);
 LTC4245_ALARM(curr4_max_alarm,	(1 << 7),	LTC4245_FAULT1);

 /* Output voltages */
 LTC4245_VOLTAGE(in5_input,			LTC4245_12VOUT);
 LTC4245_VOLTAGE(in6_input,			LTC4245_5VOUT);
 LTC4245_VOLTAGE(in7_input,			LTC4245_3VOUT);
 LTC4245_VOLTAGE(in8_input,			LTC4245_VEEOUT);

 /* Power Bad alarms */
 LTC4245_ALARM(in5_min_alarm,	(1 << 0),	LTC4245_FAULT2);
 LTC4245_ALARM(in6_min_alarm,	(1 << 1),	LTC4245_FAULT2);
 LTC4245_ALARM(in7_min_alarm,	(1 << 2),	LTC4245_FAULT2);
 LTC4245_ALARM(in8_min_alarm,	(1 << 3),	LTC4245_FAULT2);

 /* GPIO voltages */
 LTC4245_GPIO_VOLTAGE(in9_input,			0);
 LTC4245_GPIO_VOLTAGE(in10_input,		1);
 LTC4245_GPIO_VOLTAGE(in11_input,		2);

 /* Power Consumption (virtual) */
 LTC4245_POWER(power1_input,			LTC4245_12VSENSE);
 LTC4245_POWER(power2_input,			LTC4245_5VSENSE);
 LTC4245_POWER(power3_input,			LTC4245_3VSENSE);
 LTC4245_POWER(power4_input,			LTC4245_VEESENSE);

 /* Finally, construct an array of pointers to members of the above objects,
  * as required for sysfs_create_group()
  */
 static struct attribute *ltc4245_std_attributes[] = {
 	&sensor_dev_attr_in1_input.dev_attr.attr,
 	&sensor_dev_attr_in2_input.dev_attr.attr,
 	&sensor_dev_attr_in3_input.dev_attr.attr,
 	&sensor_dev_attr_in4_input.dev_attr.attr,

 	&sensor_dev_attr_in1_min_alarm.dev_attr.attr,
 	&sensor_dev_attr_in2_min_alarm.dev_attr.attr,
 	&sensor_dev_attr_in3_min_alarm.dev_attr.attr,
 	&sensor_dev_attr_in4_min_alarm.dev_attr.attr,

 	&sensor_dev_attr_curr1_input.dev_attr.attr,
 	&sensor_dev_attr_curr2_input.dev_attr.attr,
 	&sensor_dev_attr_curr3_input.dev_attr.attr,
 	&sensor_dev_attr_curr4_input.dev_attr.attr,

 	&sensor_dev_attr_curr1_max_alarm.dev_attr.attr,
 	&sensor_dev_attr_curr2_max_alarm.dev_attr.attr,
 	&sensor_dev_attr_curr3_max_alarm.dev_attr.attr,
 	&sensor_dev_attr_curr4_max_alarm.dev_attr.attr,

 	&sensor_dev_attr_in5_input.dev_attr.attr,
 	&sensor_dev_attr_in6_input.dev_attr.attr,
 	&sensor_dev_attr_in7_input.dev_attr.attr,
 	&sensor_dev_attr_in8_input.dev_attr.attr,

 	&sensor_dev_attr_in5_min_alarm.dev_attr.attr,
 	&sensor_dev_attr_in6_min_alarm.dev_attr.attr,
 	&sensor_dev_attr_in7_min_alarm.dev_attr.attr,
 	&sensor_dev_attr_in8_min_alarm.dev_attr.attr,

 	&sensor_dev_attr_in9_input.dev_attr.attr,

 	&sensor_dev_attr_power1_input.dev_attr.attr,
 	&sensor_dev_attr_power2_input.dev_attr.attr,
 	&sensor_dev_attr_power3_input.dev_attr.attr,
 	&sensor_dev_attr_power4_input.dev_attr.attr,

 	NULL,
 };

 static struct attribute *ltc4245_gpio_attributes[] = {
 	&sensor_dev_attr_in10_input.dev_attr.attr,
 	&sensor_dev_attr_in11_input.dev_attr.attr,
 	NULL,
 };

 static const struct attribute_group ltc4245_std_group = {
 	.attrs = ltc4245_std_attributes,
 };

 static const struct attribute_group ltc4245_gpio_group = {
 	.attrs = ltc4245_gpio_attributes,
 };

 static int ltc4245_sysfs_create_groups(struct i2c_client *client)
 {
 	struct ltc4245_data *data = i2c_get_clientdata(client);
 	struct device *dev = &client->dev;
 	int ret;

 	/* register the standard sysfs attributes */
 	ret = sysfs_create_group(&dev->kobj, &ltc4245_std_group);
 	if (ret) {
 		dev_err(dev, "unable to register standard attributes\n");
 		return ret;
 	}

 	/* if we're using the extra gpio support, register it's attributes */
 	if (data->use_extra_gpios) {
 		ret = sysfs_create_group(&dev->kobj, &ltc4245_gpio_group);
 		if (ret) {
 			dev_err(dev, "unable to register gpio attributes\n");
 			sysfs_remove_group(&dev->kobj, &ltc4245_std_group);
 			return ret;
 		}
 	}

 	return 0;
 }

 static void ltc4245_sysfs_remove_groups(struct i2c_client *client)
 {
 	struct ltc4245_data *data = i2c_get_clientdata(client);
 	struct device *dev = &client->dev;

 	if (data->use_extra_gpios)
 		sysfs_remove_group(&dev->kobj, &ltc4245_gpio_group);

 	sysfs_remove_group(&dev->kobj, &ltc4245_std_group);
 }

 static bool ltc4245_use_extra_gpios(struct i2c_client *client)
 {
 	struct ltc4245_platform_data *pdata = dev_get_platdata(&client->dev);
 #ifdef CONFIG_OF
 	struct device_node *np = client->dev.of_node;
 #endif

 	/* prefer platform data */
 	if (pdata)
 		return pdata->use_extra_gpios;

 #ifdef CONFIG_OF
 	/* fallback on OF */
 	if (of_find_property(np, "ltc4245,use-extra-gpios", NULL))
 		return true;
 #endif

 	return false;
 }

 static int ltc4245_probe(struct i2c_client *client,
 			 const struct i2c_device_id *id)
 {
 	struct i2c_adapter *adapter = client->adapter;
 	struct ltc4245_data *data;
 	int ret;

 	if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA))
 		return -ENODEV;

 	data = kzalloc(sizeof(*data), GFP_KERNEL);
 	if (!data) {
 		ret = -ENOMEM;
 		goto out_kzalloc;
 	}

 	i2c_set_clientdata(client, data);
 	mutex_init(&data->update_lock);
 	data->use_extra_gpios = ltc4245_use_extra_gpios(client);

 	/* Initialize the LTC4245 chip */
 	i2c_smbus_write_byte_data(client, LTC4245_FAULT1, 0x00);
 	i2c_smbus_write_byte_data(client, LTC4245_FAULT2, 0x00);

 	/* Register sysfs hooks */
 	ret = ltc4245_sysfs_create_groups(client);
 	if (ret)
 		goto out_sysfs_create_groups;

 	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:
 	ltc4245_sysfs_remove_groups(client);
 out_sysfs_create_groups:
 	kfree(data);
 out_kzalloc:
 	return ret;
 }

 static int ltc4245_remove(struct i2c_client *client)
 {
 	struct ltc4245_data *data = i2c_get_clientdata(client);

 	hwmon_device_unregister(data->hwmon_dev);
 	ltc4245_sysfs_remove_groups(client);
 	kfree(data);

 	return 0;
 }

 static const struct i2c_device_id ltc4245_id[] = {
 	{ "ltc4245", 0 },
 	{ }
 };
 MODULE_DEVICE_TABLE(i2c, ltc4245_id);

 /* This is the driver that will be inserted */
 static struct i2c_driver ltc4245_driver = {
 	.driver = {
 		.name	= "ltc4245",
 	},
 	.probe		= ltc4245_probe,
 	.remove		= ltc4245_remove,
 	.id_table	= ltc4245_id,
 };

 static int __init ltc4245_init(void)
 {
 	return i2c_add_driver(&ltc4245_driver);
 }

 static void __exit ltc4245_exit(void)
 {
 	i2c_del_driver(&ltc4245_driver);
 }

 MODULE_AUTHOR("Ira W. Snyder <iws@ovro.caltech.edu>");
 MODULE_DESCRIPTION("LTC4245 driver");
 MODULE_LICENSE("GPL");

 module_init(ltc4245_init);
 module_exit(ltc4245_exit);
	/*
	* Driver for Linear Technology LTC4245 I2C Multiple Supply Hot Swap Controller
	*
	* Copyright (C) 2008 Ira W. Snyder <iws@ovro.caltech.edu>
	*
	* 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; version 2 of the License.
	*
	* This driver is based on the ds1621 and ina209 drivers.
	*
	* Datasheet:
	* http://www.linear.com/pc/downloadDocument.do?navId=H0,C1,C1003,C1006,C1140,P19392,D13517
	*/

	#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/i2c/ltc4245.h>

	/* Here are names of the chip's registers (a.k.a. commands) */
	enum ltc4245_cmd {
	LTC4245_STATUS = 0x00, /* readonly */
	LTC4245_ALERT = 0x01,
	LTC4245_CONTROL = 0x02,
	LTC4245_ON = 0x03,
	LTC4245_FAULT1 = 0x04,
	LTC4245_FAULT2 = 0x05,
	LTC4245_GPIO = 0x06,
	LTC4245_ADCADR = 0x07,

	LTC4245_12VIN = 0x10,
	LTC4245_12VSENSE = 0x11,
	LTC4245_12VOUT = 0x12,
	LTC4245_5VIN = 0x13,
	LTC4245_5VSENSE = 0x14,
	LTC4245_5VOUT = 0x15,
	LTC4245_3VIN = 0x16,
	LTC4245_3VSENSE = 0x17,
	LTC4245_3VOUT = 0x18,
	LTC4245_VEEIN = 0x19,
	LTC4245_VEESENSE = 0x1a,
	LTC4245_VEEOUT = 0x1b,
	LTC4245_GPIOADC = 0x1c,
	};

	struct ltc4245_data {
	struct device *hwmon_dev;

	struct mutex update_lock;
	bool valid;
	unsigned long last_updated; /* in jiffies */

	/* Control registers */
	u8 cregs[0x08];

	/* Voltage registers */
	u8 vregs[0x0d];

	/* GPIO ADC registers */
	bool use_extra_gpios;
	int gpios[3];
	};

	/*
	* Update the readings from the GPIO pins. If the driver has been configured to
	* sample all GPIO's as analog voltages, a round-robin sampling method is used.
	* Otherwise, only the configured GPIO pin is sampled.
	*
	* LOCKING: must hold data->update_lock
	*/
	static void ltc4245_update_gpios(struct device *dev)
	{
	struct i2c_client *client = to_i2c_client(dev);
	struct ltc4245_data *data = i2c_get_clientdata(client);
	u8 gpio_curr, gpio_next, gpio_reg;
	int i;

	/* no extra gpio support, we're basically done */
	if (!data->use_extra_gpios) {
	data->gpios[0] = data->vregs[LTC4245_GPIOADC - 0x10];
	return;
	}

	/*
	* If the last reading was too long ago, then we mark all old GPIO
	* readings as stale by setting them to -EAGAIN
	*/
	if (time_after(jiffies, data->last_updated + 5 * HZ)) {
	dev_dbg(&client->dev, "Marking GPIOs invalid\n");
	for (i = 0; i < ARRAY_SIZE(data->gpios); i++)
	data->gpios[i] = -EAGAIN;
	}

	/*
	* Get the current GPIO pin
	*
	* The datasheet calls these GPIO[1-3], but we'll calculate the zero
	* based array index instead, and call them GPIO[0-2]. This is much
	* easier to think about.
	*/
	gpio_curr = (data->cregs[LTC4245_GPIO] & 0xc0) >> 6;
	if (gpio_curr > 0)
	gpio_curr -= 1;

	/* Read the GPIO voltage from the GPIOADC register */
	data->gpios[gpio_curr] = data->vregs[LTC4245_GPIOADC - 0x10];

	/* Find the next GPIO pin to read */
	gpio_next = (gpio_curr + 1) % ARRAY_SIZE(data->gpios);

	/*
	* Calculate the correct setting for the GPIO register so it will
	* sample the next GPIO pin
	*/
	gpio_reg = (data->cregs[LTC4245_GPIO] & 0x3f) \| ((gpio_next + 1) << 6);

	/* Update the GPIO register */
	i2c_smbus_write_byte_data(client, LTC4245_GPIO, gpio_reg);

	/* Update saved data */
	data->cregs[LTC4245_GPIO] = gpio_reg;
	}

	static struct ltc4245_data ltc4245_update_device(struct device dev)
	{
	struct i2c_client *client = to_i2c_client(dev);
	struct ltc4245_data *data = i2c_get_clientdata(client);
	s32 val;
	int i;

	mutex_lock(&data->update_lock);

	if (time_after(jiffies, data->last_updated + HZ) \|\| !data->valid) {

	dev_dbg(&client->dev, "Starting ltc4245 update\n");

	/* Read control registers -- 0x00 to 0x07 */
	for (i = 0; i < ARRAY_SIZE(data->cregs); i++) {
	val = i2c_smbus_read_byte_data(client, i);
	if (unlikely(val < 0))
	data->cregs[i] = 0;
	else
	data->cregs[i] = val;
	}

	/* Read voltage registers -- 0x10 to 0x1c */
	for (i = 0; i < ARRAY_SIZE(data->vregs); i++) {
	val = i2c_smbus_read_byte_data(client, i+0x10);
	if (unlikely(val < 0))
	data->vregs[i] = 0;
	else
	data->vregs[i] = val;
	}

	/* Update GPIO readings */
	ltc4245_update_gpios(dev);

	data->last_updated = jiffies;
	data->valid = 1;
	}

	mutex_unlock(&data->update_lock);

	return data;
	}

	/* Return the voltage from the given register in millivolts */
	static int ltc4245_get_voltage(struct device *dev, u8 reg)
	{
	struct ltc4245_data *data = ltc4245_update_device(dev);
	const u8 regval = data->vregs[reg - 0x10];
	u32 voltage = 0;

	switch (reg) {
	case LTC4245_12VIN:
	case LTC4245_12VOUT:
	voltage = regval * 55;
	break;
	case LTC4245_5VIN:
	case LTC4245_5VOUT:
	voltage = regval * 22;
	break;
	case LTC4245_3VIN:
	case LTC4245_3VOUT:
	voltage = regval * 15;
	break;
	case LTC4245_VEEIN:
	case LTC4245_VEEOUT:
	voltage = regval * -55;
	break;
	case LTC4245_GPIOADC:
	voltage = regval * 10;
	break;
	default:
	/* If we get here, the developer messed up */
	WARN_ON_ONCE(1);
	break;
	}

	return voltage;
	}

	/* Return the current in the given sense register in milliAmperes */
	static unsigned int ltc4245_get_current(struct device *dev, u8 reg)
	{
	struct ltc4245_data *data = ltc4245_update_device(dev);
	const u8 regval = data->vregs[reg - 0x10];
	unsigned int voltage;
	unsigned int curr;

	/* The strange looking conversions that follow are fixed-point
	* math, since we cannot do floating point in the kernel.
	*
	* Step 1: convert sense register to microVolts
	* Step 2: convert voltage to milliAmperes
	*
	* If you play around with the V=IR equation, you come up with
	* the following: X uV / Y mOhm == Z mA
	*
	* With the resistors that are fractions of a milliOhm, we multiply
	* the voltage and resistance by 10, to shift the decimal point.
	* Now we can use the normal division operator again.
	*/

	switch (reg) {
	case LTC4245_12VSENSE:
	voltage = regval * 250; /* voltage in uV */
	curr = voltage / 50; /* sense resistor 50 mOhm */
	break;
	case LTC4245_5VSENSE:
	voltage = regval * 125; /* voltage in uV */
	curr = (voltage * 10) / 35; /* sense resistor 3.5 mOhm */
	break;
	case LTC4245_3VSENSE:
	voltage = regval * 125; /* voltage in uV */
	curr = (voltage * 10) / 25; /* sense resistor 2.5 mOhm */
	break;
	case LTC4245_VEESENSE:
	voltage = regval * 250; /* voltage in uV */
	curr = voltage / 100; /* sense resistor 100 mOhm */
	break;
	default:
	/* If we get here, the developer messed up */
	WARN_ON_ONCE(1);
	curr = 0;
	break;
	}

	return curr;
	}

	static ssize_t ltc4245_show_voltage(struct device *dev,
	struct device_attribute *da,
	char *buf)
	{
	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
	const int voltage = ltc4245_get_voltage(dev, attr->index);

	return snprintf(buf, PAGE_SIZE, "%d\n", voltage);
	}

	static ssize_t ltc4245_show_current(struct device *dev,
	struct device_attribute *da,
	char *buf)
	{
	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
	const unsigned int curr = ltc4245_get_current(dev, attr->index);

	return snprintf(buf, PAGE_SIZE, "%u\n", curr);
	}

	static ssize_t ltc4245_show_power(struct device *dev,
	struct device_attribute *da,
	char *buf)
	{
	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
	const unsigned int curr = ltc4245_get_current(dev, attr->index);
	const int output_voltage = ltc4245_get_voltage(dev, attr->index+1);

	/* current in mA * voltage in mV == power in uW */
	const unsigned int power = abs(output_voltage * curr);

	return snprintf(buf, PAGE_SIZE, "%u\n", power);
	}

	static ssize_t ltc4245_show_alarm(struct device *dev,
	struct device_attribute *da,
	char *buf)
	{
	struct sensor_device_attribute_2 *attr = to_sensor_dev_attr_2(da);
	struct ltc4245_data *data = ltc4245_update_device(dev);
	const u8 reg = data->cregs[attr->index];
	const u32 mask = attr->nr;

	return snprintf(buf, PAGE_SIZE, "%u\n", (reg & mask) ? 1 : 0);
	}

	static ssize_t ltc4245_show_gpio(struct device *dev,
	struct device_attribute *da,
	char *buf)
	{
	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
	struct ltc4245_data *data = ltc4245_update_device(dev);
	int val = data->gpios[attr->index];

	/* handle stale GPIO's */
	if (val < 0)
	return val;

	/* Convert to millivolts and print */
	return snprintf(buf, PAGE_SIZE, "%u\n", val * 10);
	}

	/* These macros are used below in constructing device attribute objects
	* for use with sysfs_create_group() to make a sysfs device file
	* for each register.
	*/

	#define LTC4245_VOLTAGE(name, ltc4245_cmd_idx) \
	static SENSOR_DEVICE_ATTR(name, S_IRUGO, \
	ltc4245_show_voltage, NULL, ltc4245_cmd_idx)

	#define LTC4245_CURRENT(name, ltc4245_cmd_idx) \
	static SENSOR_DEVICE_ATTR(name, S_IRUGO, \
	ltc4245_show_current, NULL, ltc4245_cmd_idx)

	#define LTC4245_POWER(name, ltc4245_cmd_idx) \
	static SENSOR_DEVICE_ATTR(name, S_IRUGO, \
	ltc4245_show_power, NULL, ltc4245_cmd_idx)

	#define LTC4245_ALARM(name, mask, reg) \
	static SENSOR_DEVICE_ATTR_2(name, S_IRUGO, \
	ltc4245_show_alarm, NULL, (mask), reg)

	#define LTC4245_GPIO_VOLTAGE(name, gpio_num) \
	static SENSOR_DEVICE_ATTR(name, S_IRUGO, \
	ltc4245_show_gpio, NULL, gpio_num)

	/* Construct a sensor_device_attribute structure for each register */

	/* Input voltages */
	LTC4245_VOLTAGE(in1_input, LTC4245_12VIN);
	LTC4245_VOLTAGE(in2_input, LTC4245_5VIN);
	LTC4245_VOLTAGE(in3_input, LTC4245_3VIN);
	LTC4245_VOLTAGE(in4_input, LTC4245_VEEIN);

	/* Input undervoltage alarms */
	LTC4245_ALARM(in1_min_alarm, (1 << 0), LTC4245_FAULT1);
	LTC4245_ALARM(in2_min_alarm, (1 << 1), LTC4245_FAULT1);
	LTC4245_ALARM(in3_min_alarm, (1 << 2), LTC4245_FAULT1);
	LTC4245_ALARM(in4_min_alarm, (1 << 3), LTC4245_FAULT1);

	/* Currents (via sense resistor) */
	LTC4245_CURRENT(curr1_input, LTC4245_12VSENSE);
	LTC4245_CURRENT(curr2_input, LTC4245_5VSENSE);
	LTC4245_CURRENT(curr3_input, LTC4245_3VSENSE);
	LTC4245_CURRENT(curr4_input, LTC4245_VEESENSE);

	/* Overcurrent alarms */
	LTC4245_ALARM(curr1_max_alarm, (1 << 4), LTC4245_FAULT1);
	LTC4245_ALARM(curr2_max_alarm, (1 << 5), LTC4245_FAULT1);
	LTC4245_ALARM(curr3_max_alarm, (1 << 6), LTC4245_FAULT1);
	LTC4245_ALARM(curr4_max_alarm, (1 << 7), LTC4245_FAULT1);

	/* Output voltages */
	LTC4245_VOLTAGE(in5_input, LTC4245_12VOUT);
	LTC4245_VOLTAGE(in6_input, LTC4245_5VOUT);
	LTC4245_VOLTAGE(in7_input, LTC4245_3VOUT);
	LTC4245_VOLTAGE(in8_input, LTC4245_VEEOUT);

	/* Power Bad alarms */
	LTC4245_ALARM(in5_min_alarm, (1 << 0), LTC4245_FAULT2);
	LTC4245_ALARM(in6_min_alarm, (1 << 1), LTC4245_FAULT2);
	LTC4245_ALARM(in7_min_alarm, (1 << 2), LTC4245_FAULT2);
	LTC4245_ALARM(in8_min_alarm, (1 << 3), LTC4245_FAULT2);

	/* GPIO voltages */
	LTC4245_GPIO_VOLTAGE(in9_input, 0);
	LTC4245_GPIO_VOLTAGE(in10_input, 1);
	LTC4245_GPIO_VOLTAGE(in11_input, 2);

	/* Power Consumption (virtual) */
	LTC4245_POWER(power1_input, LTC4245_12VSENSE);
	LTC4245_POWER(power2_input, LTC4245_5VSENSE);
	LTC4245_POWER(power3_input, LTC4245_3VSENSE);
	LTC4245_POWER(power4_input, LTC4245_VEESENSE);

	/* Finally, construct an array of pointers to members of the above objects,
	* as required for sysfs_create_group()
	*/
	static struct attribute *ltc4245_std_attributes[] = {
	&sensor_dev_attr_in1_input.dev_attr.attr,
	&sensor_dev_attr_in2_input.dev_attr.attr,
	&sensor_dev_attr_in3_input.dev_attr.attr,
	&sensor_dev_attr_in4_input.dev_attr.attr,

	&sensor_dev_attr_in1_min_alarm.dev_attr.attr,
	&sensor_dev_attr_in2_min_alarm.dev_attr.attr,
	&sensor_dev_attr_in3_min_alarm.dev_attr.attr,
	&sensor_dev_attr_in4_min_alarm.dev_attr.attr,

	&sensor_dev_attr_curr1_input.dev_attr.attr,
	&sensor_dev_attr_curr2_input.dev_attr.attr,
	&sensor_dev_attr_curr3_input.dev_attr.attr,
	&sensor_dev_attr_curr4_input.dev_attr.attr,

	&sensor_dev_attr_curr1_max_alarm.dev_attr.attr,
	&sensor_dev_attr_curr2_max_alarm.dev_attr.attr,
	&sensor_dev_attr_curr3_max_alarm.dev_attr.attr,
	&sensor_dev_attr_curr4_max_alarm.dev_attr.attr,

	&sensor_dev_attr_in5_input.dev_attr.attr,
	&sensor_dev_attr_in6_input.dev_attr.attr,
	&sensor_dev_attr_in7_input.dev_attr.attr,
	&sensor_dev_attr_in8_input.dev_attr.attr,

	&sensor_dev_attr_in5_min_alarm.dev_attr.attr,
	&sensor_dev_attr_in6_min_alarm.dev_attr.attr,
	&sensor_dev_attr_in7_min_alarm.dev_attr.attr,
	&sensor_dev_attr_in8_min_alarm.dev_attr.attr,

	&sensor_dev_attr_in9_input.dev_attr.attr,

	&sensor_dev_attr_power1_input.dev_attr.attr,
	&sensor_dev_attr_power2_input.dev_attr.attr,
	&sensor_dev_attr_power3_input.dev_attr.attr,
	&sensor_dev_attr_power4_input.dev_attr.attr,

	NULL,
	};

	static struct attribute *ltc4245_gpio_attributes[] = {
	&sensor_dev_attr_in10_input.dev_attr.attr,
	&sensor_dev_attr_in11_input.dev_attr.attr,
	NULL,
	};

	static const struct attribute_group ltc4245_std_group = {
	.attrs = ltc4245_std_attributes,
	};

	static const struct attribute_group ltc4245_gpio_group = {
	.attrs = ltc4245_gpio_attributes,
	};

	static int ltc4245_sysfs_create_groups(struct i2c_client *client)
	{
	struct ltc4245_data *data = i2c_get_clientdata(client);
	struct device *dev = &client->dev;
	int ret;

	/* register the standard sysfs attributes */
	ret = sysfs_create_group(&dev->kobj, &ltc4245_std_group);
	if (ret) {
	dev_err(dev, "unable to register standard attributes\n");
	return ret;
	}

	/* if we're using the extra gpio support, register it's attributes */
	if (data->use_extra_gpios) {
	ret = sysfs_create_group(&dev->kobj, &ltc4245_gpio_group);
	if (ret) {
	dev_err(dev, "unable to register gpio attributes\n");
	sysfs_remove_group(&dev->kobj, &ltc4245_std_group);
	return ret;
	}
	}

	return 0;
	}

	static void ltc4245_sysfs_remove_groups(struct i2c_client *client)
	{
	struct ltc4245_data *data = i2c_get_clientdata(client);
	struct device *dev = &client->dev;

	if (data->use_extra_gpios)
	sysfs_remove_group(&dev->kobj, &ltc4245_gpio_group);

	sysfs_remove_group(&dev->kobj, &ltc4245_std_group);
	}

	static bool ltc4245_use_extra_gpios(struct i2c_client *client)
	{
	struct ltc4245_platform_data *pdata = dev_get_platdata(&client->dev);
	#ifdef CONFIG_OF
	struct device_node *np = client->dev.of_node;
	#endif

	/* prefer platform data */
	if (pdata)
	return pdata->use_extra_gpios;

	#ifdef CONFIG_OF
	/* fallback on OF */
	if (of_find_property(np, "ltc4245,use-extra-gpios", NULL))
	return true;
	#endif

	return false;
	}

	static int ltc4245_probe(struct i2c_client *client,
	const struct i2c_device_id *id)
	{
	struct i2c_adapter *adapter = client->adapter;
	struct ltc4245_data *data;
	int ret;

	if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA))
	return -ENODEV;

	data = kzalloc(sizeof(*data), GFP_KERNEL);
	if (!data) {
	ret = -ENOMEM;
	goto out_kzalloc;
	}

	i2c_set_clientdata(client, data);
	mutex_init(&data->update_lock);
	data->use_extra_gpios = ltc4245_use_extra_gpios(client);

	/* Initialize the LTC4245 chip */
	i2c_smbus_write_byte_data(client, LTC4245_FAULT1, 0x00);
	i2c_smbus_write_byte_data(client, LTC4245_FAULT2, 0x00);

	/* Register sysfs hooks */
	ret = ltc4245_sysfs_create_groups(client);
	if (ret)
	goto out_sysfs_create_groups;

	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:
	ltc4245_sysfs_remove_groups(client);
	out_sysfs_create_groups:
	kfree(data);
	out_kzalloc:
	return ret;
	}

	static int ltc4245_remove(struct i2c_client *client)
	{
	struct ltc4245_data *data = i2c_get_clientdata(client);

	hwmon_device_unregister(data->hwmon_dev);
	ltc4245_sysfs_remove_groups(client);
	kfree(data);

	return 0;
	}

	static const struct i2c_device_id ltc4245_id[] = {
	{ "ltc4245", 0 },
	{ }
	};
	MODULE_DEVICE_TABLE(i2c, ltc4245_id);

	/* This is the driver that will be inserted */
	static struct i2c_driver ltc4245_driver = {
	.driver = {
	.name = "ltc4245",
	},
	.probe = ltc4245_probe,
	.remove = ltc4245_remove,
	.id_table = ltc4245_id,
	};

	static int __init ltc4245_init(void)
	{
	return i2c_add_driver(&ltc4245_driver);
	}

	static void __exit ltc4245_exit(void)
	{
	i2c_del_driver(&ltc4245_driver);
	}

	MODULE_AUTHOR("Ira W. Snyder <iws@ovro.caltech.edu>");
	MODULE_DESCRIPTION("LTC4245 driver");
	MODULE_LICENSE("GPL");

	module_init(ltc4245_init);
	module_exit(ltc4245_exit);