src/kernel/linux/v4.19/drivers/hwmon/ltc4245.c - T800 - 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/bitops.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>
 #include <linux/platform_data/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 i2c_client *client;

 	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 ltc4245_data *data = dev_get_drvdata(dev);
 	struct i2c_client *client = data->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)) {
 		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 ltc4245_data *data = dev_get_drvdata(dev);
 	struct i2c_client *client = data->client;
 	s32 val;
 	int i;

 	mutex_lock(&data->update_lock);

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

 		/* 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 = true;
 	}

 	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;
 }

 /* Map from voltage channel index to voltage register */

 static const s8 ltc4245_in_regs[] = {
 	LTC4245_12VIN, LTC4245_5VIN, LTC4245_3VIN, LTC4245_VEEIN,
 	LTC4245_12VOUT, LTC4245_5VOUT, LTC4245_3VOUT, LTC4245_VEEOUT,
 };

 /* Map from current channel index to current register */

 static const s8 ltc4245_curr_regs[] = {
 	LTC4245_12VSENSE, LTC4245_5VSENSE, LTC4245_3VSENSE, LTC4245_VEESENSE,
 };

 static int ltc4245_read_curr(struct device *dev, u32 attr, int channel,
 			     long *val)
 {
 	struct ltc4245_data *data = ltc4245_update_device(dev);

 	switch (attr) {
 	case hwmon_curr_input:
 		*val = ltc4245_get_current(dev, ltc4245_curr_regs[channel]);
 		return 0;
 	case hwmon_curr_max_alarm:
 		*val = !!(data->cregs[LTC4245_FAULT1] & BIT(channel + 4));
 		return 0;
 	default:
 		return -EOPNOTSUPP;
 	}
 }

 static int ltc4245_read_in(struct device *dev, u32 attr, int channel, long *val)
 {
 	struct ltc4245_data *data = ltc4245_update_device(dev);

 	switch (attr) {
 	case hwmon_in_input:
 		if (channel < 8) {
 			*val = ltc4245_get_voltage(dev,
 						ltc4245_in_regs[channel]);
 		} else {
 			int regval = data->gpios[channel - 8];

 			if (regval < 0)
 				return regval;
 			*val = regval * 10;
 		}
 		return 0;
 	case hwmon_in_min_alarm:
 		if (channel < 4)
 			*val = !!(data->cregs[LTC4245_FAULT1] & BIT(channel));
 		else
 			*val = !!(data->cregs[LTC4245_FAULT2] &
 				  BIT(channel - 4));
 		return 0;
 	default:
 		return -EOPNOTSUPP;
 	}
 }

 static int ltc4245_read_power(struct device *dev, u32 attr, int channel,
 			      long *val)
 {
 	unsigned long curr;
 	long voltage;

 	switch (attr) {
 	case hwmon_power_input:
 		(void)ltc4245_update_device(dev);
 		curr = ltc4245_get_current(dev, ltc4245_curr_regs[channel]);
 		voltage = ltc4245_get_voltage(dev, ltc4245_in_regs[channel]);
 		*val = abs(curr * voltage);
 		return 0;
 	default:
 		return -EOPNOTSUPP;
 	}
 }

 static int ltc4245_read(struct device *dev, enum hwmon_sensor_types type,
 			u32 attr, int channel, long *val)
 {

 	switch (type) {
 	case hwmon_curr:
 		return ltc4245_read_curr(dev, attr, channel, val);
 	case hwmon_power:
 		return ltc4245_read_power(dev, attr, channel, val);
 	case hwmon_in:
 		return ltc4245_read_in(dev, attr, channel - 1, val);
 	default:
 		return -EOPNOTSUPP;
 	}
 }

 static umode_t ltc4245_is_visible(const void *_data,
 				  enum hwmon_sensor_types type,
 				  u32 attr, int channel)
 {
 	const struct ltc4245_data *data = _data;

 	switch (type) {
 	case hwmon_in:
 		if (channel == 0)
 			return 0;
 		switch (attr) {
 		case hwmon_in_input:
 			if (channel > 9 && !data->use_extra_gpios)
 				return 0;
 			return S_IRUGO;
 		case hwmon_in_min_alarm:
 			if (channel > 8)
 				return 0;
 			return S_IRUGO;
 		default:
 			return 0;
 		}
 	case hwmon_curr:
 		switch (attr) {
 		case hwmon_curr_input:
 		case hwmon_curr_max_alarm:
 			return S_IRUGO;
 		default:
 			return 0;
 		}
 	case hwmon_power:
 		switch (attr) {
 		case hwmon_power_input:
 			return S_IRUGO;
 		default:
 			return 0;
 		}
 	default:
 		return 0;
 	}
 }

 static const u32 ltc4245_in_config[] = {
 	HWMON_I_INPUT,			/* dummy, skipped in is_visible */
 	HWMON_I_INPUT | HWMON_I_MIN_ALARM,
 	HWMON_I_INPUT | HWMON_I_MIN_ALARM,
 	HWMON_I_INPUT | HWMON_I_MIN_ALARM,
 	HWMON_I_INPUT | HWMON_I_MIN_ALARM,
 	HWMON_I_INPUT | HWMON_I_MIN_ALARM,
 	HWMON_I_INPUT | HWMON_I_MIN_ALARM,
 	HWMON_I_INPUT | HWMON_I_MIN_ALARM,
 	HWMON_I_INPUT | HWMON_I_MIN_ALARM,
 	HWMON_I_INPUT,
 	HWMON_I_INPUT,
 	HWMON_I_INPUT,
 	0
 };

 static const struct hwmon_channel_info ltc4245_in = {
 	.type = hwmon_in,
 	.config = ltc4245_in_config,
 };

 static const u32 ltc4245_curr_config[] = {
 	HWMON_C_INPUT | HWMON_C_MAX_ALARM,
 	HWMON_C_INPUT | HWMON_C_MAX_ALARM,
 	HWMON_C_INPUT | HWMON_C_MAX_ALARM,
 	HWMON_C_INPUT | HWMON_C_MAX_ALARM,
 	0
 };

 static const struct hwmon_channel_info ltc4245_curr = {
 	.type = hwmon_curr,
 	.config = ltc4245_curr_config,
 };

 static const u32 ltc4245_power_config[] = {
 	HWMON_P_INPUT,
 	HWMON_P_INPUT,
 	HWMON_P_INPUT,
 	HWMON_P_INPUT,
 	0
 };

 static const struct hwmon_channel_info ltc4245_power = {
 	.type = hwmon_power,
 	.config = ltc4245_power_config,
 };

 static const struct hwmon_channel_info *ltc4245_info[] = {
 	&ltc4245_in,
 	&ltc4245_curr,
 	&ltc4245_power,
 	NULL
 };

 static const struct hwmon_ops ltc4245_hwmon_ops = {
 	.is_visible = ltc4245_is_visible,
 	.read = ltc4245_read,
 };

 static const struct hwmon_chip_info ltc4245_chip_info = {
 	.ops = &ltc4245_hwmon_ops,
 	.info = ltc4245_info,
 };

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

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

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

 	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;
 	struct device *hwmon_dev;

 	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;

 	data->client = client;
 	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);

 	hwmon_dev = devm_hwmon_device_register_with_info(&client->dev,
 							 client->name, data,
 							 &ltc4245_chip_info,
 							 NULL);
 	return PTR_ERR_OR_ZERO(hwmon_dev);
 }

 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,
 	.id_table	= ltc4245_id,
 };

 module_i2c_driver(ltc4245_driver);

 MODULE_AUTHOR("Ira W. Snyder <iws@ovro.caltech.edu>");
 MODULE_DESCRIPTION("LTC4245 driver");
 MODULE_LICENSE("GPL");
	/*
	* 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/bitops.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>
	#include <linux/platform_data/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 i2c_client *client;

	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 ltc4245_data *data = dev_get_drvdata(dev);
	struct i2c_client *client = data->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)) {
	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 ltc4245_data *data = dev_get_drvdata(dev);
	struct i2c_client *client = data->client;
	s32 val;
	int i;

	mutex_lock(&data->update_lock);

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

	/* 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 = true;
	}

	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;
	}

	/* Map from voltage channel index to voltage register */

	static const s8 ltc4245_in_regs[] = {
	LTC4245_12VIN, LTC4245_5VIN, LTC4245_3VIN, LTC4245_VEEIN,
	LTC4245_12VOUT, LTC4245_5VOUT, LTC4245_3VOUT, LTC4245_VEEOUT,
	};

	/* Map from current channel index to current register */

	static const s8 ltc4245_curr_regs[] = {
	LTC4245_12VSENSE, LTC4245_5VSENSE, LTC4245_3VSENSE, LTC4245_VEESENSE,
	};

	static int ltc4245_read_curr(struct device *dev, u32 attr, int channel,
	long *val)
	{
	struct ltc4245_data *data = ltc4245_update_device(dev);

	switch (attr) {
	case hwmon_curr_input:
	*val = ltc4245_get_current(dev, ltc4245_curr_regs[channel]);
	return 0;
	case hwmon_curr_max_alarm:
	*val = !!(data->cregs[LTC4245_FAULT1] & BIT(channel + 4));
	return 0;
	default:
	return -EOPNOTSUPP;
	}
	}

	static int ltc4245_read_in(struct device dev, u32 attr, int channel, long val)
	{
	struct ltc4245_data *data = ltc4245_update_device(dev);

	switch (attr) {
	case hwmon_in_input:
	if (channel < 8) {
	*val = ltc4245_get_voltage(dev,
	ltc4245_in_regs[channel]);
	} else {
	int regval = data->gpios[channel - 8];

	if (regval < 0)
	return regval;
	val = regval 10;
	}
	return 0;
	case hwmon_in_min_alarm:
	if (channel < 4)
	*val = !!(data->cregs[LTC4245_FAULT1] & BIT(channel));
	else
	*val = !!(data->cregs[LTC4245_FAULT2] &
	BIT(channel - 4));
	return 0;
	default:
	return -EOPNOTSUPP;
	}
	}

	static int ltc4245_read_power(struct device *dev, u32 attr, int channel,
	long *val)
	{
	unsigned long curr;
	long voltage;

	switch (attr) {
	case hwmon_power_input:
	(void)ltc4245_update_device(dev);
	curr = ltc4245_get_current(dev, ltc4245_curr_regs[channel]);
	voltage = ltc4245_get_voltage(dev, ltc4245_in_regs[channel]);
	val = abs(curr voltage);
	return 0;
	default:
	return -EOPNOTSUPP;
	}
	}

	static int ltc4245_read(struct device *dev, enum hwmon_sensor_types type,
	u32 attr, int channel, long *val)
	{

	switch (type) {
	case hwmon_curr:
	return ltc4245_read_curr(dev, attr, channel, val);
	case hwmon_power:
	return ltc4245_read_power(dev, attr, channel, val);
	case hwmon_in:
	return ltc4245_read_in(dev, attr, channel - 1, val);
	default:
	return -EOPNOTSUPP;
	}
	}

	static umode_t ltc4245_is_visible(const void *_data,
	enum hwmon_sensor_types type,
	u32 attr, int channel)
	{
	const struct ltc4245_data *data = _data;

	switch (type) {
	case hwmon_in:
	if (channel == 0)
	return 0;
	switch (attr) {
	case hwmon_in_input:
	if (channel > 9 && !data->use_extra_gpios)
	return 0;
	return S_IRUGO;
	case hwmon_in_min_alarm:
	if (channel > 8)
	return 0;
	return S_IRUGO;
	default:
	return 0;
	}
	case hwmon_curr:
	switch (attr) {
	case hwmon_curr_input:
	case hwmon_curr_max_alarm:
	return S_IRUGO;
	default:
	return 0;
	}
	case hwmon_power:
	switch (attr) {
	case hwmon_power_input:
	return S_IRUGO;
	default:
	return 0;
	}
	default:
	return 0;
	}
	}

	static const u32 ltc4245_in_config[] = {
	HWMON_I_INPUT, /* dummy, skipped in is_visible */
	HWMON_I_INPUT \| HWMON_I_MIN_ALARM,
	HWMON_I_INPUT \| HWMON_I_MIN_ALARM,
	HWMON_I_INPUT \| HWMON_I_MIN_ALARM,
	HWMON_I_INPUT \| HWMON_I_MIN_ALARM,
	HWMON_I_INPUT \| HWMON_I_MIN_ALARM,
	HWMON_I_INPUT \| HWMON_I_MIN_ALARM,
	HWMON_I_INPUT \| HWMON_I_MIN_ALARM,
	HWMON_I_INPUT \| HWMON_I_MIN_ALARM,
	HWMON_I_INPUT,
	HWMON_I_INPUT,
	HWMON_I_INPUT,
	0
	};

	static const struct hwmon_channel_info ltc4245_in = {
	.type = hwmon_in,
	.config = ltc4245_in_config,
	};

	static const u32 ltc4245_curr_config[] = {
	HWMON_C_INPUT \| HWMON_C_MAX_ALARM,
	HWMON_C_INPUT \| HWMON_C_MAX_ALARM,
	HWMON_C_INPUT \| HWMON_C_MAX_ALARM,
	HWMON_C_INPUT \| HWMON_C_MAX_ALARM,
	0
	};

	static const struct hwmon_channel_info ltc4245_curr = {
	.type = hwmon_curr,
	.config = ltc4245_curr_config,
	};

	static const u32 ltc4245_power_config[] = {
	HWMON_P_INPUT,
	HWMON_P_INPUT,
	HWMON_P_INPUT,
	HWMON_P_INPUT,
	0
	};

	static const struct hwmon_channel_info ltc4245_power = {
	.type = hwmon_power,
	.config = ltc4245_power_config,
	};

	static const struct hwmon_channel_info *ltc4245_info[] = {
	&ltc4245_in,
	&ltc4245_curr,
	&ltc4245_power,
	NULL
	};

	static const struct hwmon_ops ltc4245_hwmon_ops = {
	.is_visible = ltc4245_is_visible,
	.read = ltc4245_read,
	};

	static const struct hwmon_chip_info ltc4245_chip_info = {
	.ops = &ltc4245_hwmon_ops,
	.info = ltc4245_info,
	};

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

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

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

	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;
	struct device *hwmon_dev;

	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;

	data->client = client;
	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);

	hwmon_dev = devm_hwmon_device_register_with_info(&client->dev,
	client->name, data,
	&ltc4245_chip_info,
	NULL);
	return PTR_ERR_OR_ZERO(hwmon_dev);
	}

	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,
	.id_table = ltc4245_id,
	};

	module_i2c_driver(ltc4245_driver);

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