[lm-sensors] [PATCH] hwmon: Add LTC4245 driver

Hans de Goede hdegoede at redhat.com
Mon Oct 20 19:29:50 CEST 2008



Ira Snyder wrote:
> Add Linux support for the Linear Technology LTC4245 Multiple Supply Hot
> Swap controller I2C monitoring interface.
> 
> Signed-off-by: Ira W. Snyder <iws at ovro.caltech.edu>
> ---
> 
> I'm pretty sure this should be the final revision of the driver. Please
> go ahead and forward it upstream. :)
> 

Looks good now :)

Jean, can you put this patch in your for Linus for 2.6.28 queue please?

This is:
Reviewed-by: Hans de Goede <hdegoede at redhat.com>
or
Signed-off-by: Hans de Goede <hdegoede at redhat.com>

Whatever you deem more appropriate.

Thanks & Regards,

Hans

> Changes v3 -> v4:
>   * simplify ltc4245_get_voltage(), removing special casing for -12v
>   * power should always be a positive value
> 
> Changes v2 -> v3:
>   * fix units (power?_input in uW, curr?_input in mA)
>   * combine all alarm functions
>   * rename power[1-4]_alarm to in[5-8]_min_alarm, per suggestions
> 
> Changes v1 -> v2:
>   * fixed checkpatch warnings
>   * removed raw register access, per suggestions
>   * changed sysfs interface, per suggestions (current, power, alarms)
> 
> 
>  Documentation/hwmon/ltc4245 |   69 +++++
>  drivers/hwmon/Kconfig       |   11 +
>  drivers/hwmon/Makefile      |    1 +
>  drivers/hwmon/ltc4245.c     |  574 +++++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 655 insertions(+), 0 deletions(-)
>  create mode 100644 Documentation/hwmon/ltc4245
>  create mode 100644 drivers/hwmon/ltc4245.c
> 
> diff --git a/Documentation/hwmon/ltc4245 b/Documentation/hwmon/ltc4245
> new file mode 100644
> index 0000000..d2f411a
> --- /dev/null
> +++ b/Documentation/hwmon/ltc4245
> @@ -0,0 +1,69 @@
> +Kernel driver ltc4245
> +=====================
> +
> +Supported chips:
> +  * Linear Technology LTC4245
> +    Prefix: 'ltc4245'
> +    Addresses scanned: 0x20-0x3f
> +    Datasheet:
> +        http://www.linear.com/pc/downloadDocument.do?navId=H0,C1,C1003,C1006,C1140,P19392,D13517
> +
> +Author: Ira W. Snyder <iws at ovro.caltech.edu>
> +
> +
> +Description
> +-----------
> +
> +The LTC4245 controller allows a board to be safely inserted and removed
> +from a live backplane in multiple supply systems such as CompactPCI and
> +PCI Express.
> +
> +
> +Sysfs entries
> +-------------
> +
> +The LTC4245 has built-in limits for over and under current warnings. This
> +makes it very likely that the reference circuit will be used.
> +
> +This driver uses the values in the datasheet to change the register values
> +into the values specified in the sysfs-interface document. The current readings
> +rely on the sense resistors listed in Table 2: "Sense Resistor Values".
> +
> +in1_input		12v input voltage (mV)
> +in2_input		5v  input voltage (mV)
> +in3_input		3v  input voltage (mV)
> +in4_input		Vee (-12v) input voltage (mV)
> +
> +in1_min_alarm		12v input undervoltage alarm
> +in2_min_alarm		5v  input undervoltage alarm
> +in3_min_alarm		3v  input undervoltage alarm
> +in4_min_alarm		Vee (-12v) input undervoltage alarm
> +
> +curr1_input		12v current (mA)
> +curr2_input		5v  current (mA)
> +curr3_input		3v  current (mA)
> +curr4_input		Vee (-12v) current (mA)
> +
> +curr1_max_alarm		12v overcurrent alarm
> +curr2_max_alarm		5v  overcurrent alarm
> +curr3_max_alarm		3v  overcurrent alarm
> +curr4_max_alarm		Vee (-12v) overcurrent alarm
> +
> +in5_input		12v output voltage (mV)
> +in6_input		5v  output voltage (mV)
> +in7_input		3v  output voltage (mV)
> +in8_input		Vee (-12v) output voltage (mV)
> +
> +in5_min_alarm		12v output undervoltage alarm
> +in6_min_alarm		5v  output undervoltage alarm
> +in7_min_alarm		3v  output undervoltage alarm
> +in8_min_alarm		Vee (-12v) output undervoltage alarm
> +
> +in9_input		GPIO #1 voltage data
> +in10_input		GPIO #2 voltage data
> +in11_input		GPIO #3 voltage data
> +
> +power1_input		12v power usage (mW)
> +power2_input		5v  power usage (mW)
> +power3_input		3v  power usage (mW)
> +power4_input		Vee (-12v) power usage (mW)
> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> index d402e8d..91bec8a 100644
> --- a/drivers/hwmon/Kconfig
> +++ b/drivers/hwmon/Kconfig
> @@ -836,6 +836,17 @@ config SENSORS_APPLESMC
>  	  Say Y here if you have an applicable laptop and want to experience
>  	  the awesome power of applesmc.
>  
> +config SENSORS_LTC4245
> +	tristate "Linear Technology LTC4245"
> +	depends on I2C && EXPERIMENTAL
> +	default n
> +	help
> +	  If you say yes here you get support for Linear Technology LTC4245
> +	  Multiple Supply Hot Swap Controller I2C interface.
> +
> +	  This driver can also be built as a module. If so, the module will
> +	  be called ltc4245.
> +
>  config HWMON_DEBUG_CHIP
>  	bool "Hardware Monitoring Chip debugging messages"
>  	default n
> diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
> index 950134a..0ed56ac 100644
> --- a/drivers/hwmon/Makefile
> +++ b/drivers/hwmon/Makefile
> @@ -59,6 +59,7 @@ obj-$(CONFIG_SENSORS_LM87)	+= lm87.o
>  obj-$(CONFIG_SENSORS_LM90)	+= lm90.o
>  obj-$(CONFIG_SENSORS_LM92)	+= lm92.o
>  obj-$(CONFIG_SENSORS_LM93)	+= lm93.o
> +obj-$(CONFIG_SENSORS_LTC4245)	+= ltc4245.o
>  obj-$(CONFIG_SENSORS_MAX1619)	+= max1619.o
>  obj-$(CONFIG_SENSORS_MAX6650)	+= max6650.o
>  obj-$(CONFIG_SENSORS_PC87360)	+= pc87360.o
> diff --git a/drivers/hwmon/ltc4245.c b/drivers/hwmon/ltc4245.c
> new file mode 100644
> index 0000000..5d0528b
> --- /dev/null
> +++ b/drivers/hwmon/ltc4245.c
> @@ -0,0 +1,574 @@
> +/*
> + * Driver for Linear Technology LTC4245 I2C Multiple Supply Hot Swap Controller
> + *
> + * Copyright (C) 2008 Ira W. Snyder <iws at 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/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>
> +
> +/* Addresses to probe */
> +static unsigned short normal_i2c[] = {
> +	0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27,
> +	0x28, 0x29, 0x2a, 0x2b, 0x2c, 0x2d, 0x2e, 0x2f,
> +	0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37,
> +	0x38, 0x39, 0x3a, 0x3b, 0x3c, 0x3d, 0x3e, 0x3f,
> +	I2C_CLIENT_END};
> +
> +/* Insmod parameters */
> +I2C_CLIENT_INSMOD_1(ltc4245);
> +
> +/* 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_GPIOADC1		= 0x1c,
> +	LTC4245_GPIOADC2		= 0x1d,
> +	LTC4245_GPIOADC3		= 0x1e,
> +};
> +
> +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[0x0f];
> +};
> +
> +/* All registers are byte-sized (8 bit) */
> +static s32 ltc4245_read_reg(struct i2c_client *client, u8 reg)
> +{
> +	return i2c_smbus_read_byte_data(client, reg);
> +}
> +
> +#if 0
> +static s32 ltc4245_write_reg(struct i2c_client *client, u8 reg, u8 val)
> +{
> +	return i2c_smbus_write_byte_data(client, reg, val);
> +}
> +#endif
> +
> +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);
> +	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++)
> +			data->cregs[i] = ltc4245_read_reg(client, i);
> +
> +		/* Read voltage registers -- 0x10 to 0x1f */
> +		for (i = 0; i < ARRAY_SIZE(data->vregs); i++)
> +			data->vregs[i] = ltc4245_read_reg(client, i+0x10);
> +
> +		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 s32 val = data->vregs[reg - 0x10];
> +	const u8 regval = val;
> +	u32 voltage = 0;
> +
> +	if (unlikely(val < 0))
> +		return 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_GPIOADC1:
> +	case LTC4245_GPIOADC2:
> +	case LTC4245_GPIOADC3:
> +		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 u32 ltc4245_get_current(struct device *dev, u8 reg)
> +{
> +	struct ltc4245_data *data = ltc4245_update_device(dev);
> +	const s32 val = data->vregs[reg - 0x10];
> +	const u8 regval = val;
> +	u32 voltage;
> +	u32 current;
> +
> +	if (unlikely(val) < 0)
> +		return 0;
> +
> +	/* 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 */
> +		current = voltage / 50; /* sense resistor 50 mOhm */
> +		break;
> +	case LTC4245_5VSENSE:
> +		voltage = regval * 125; /* voltage in uV */
> +		current = (voltage * 10) / 35; /* sense resistor 3.5 mOhm */
> +		break;
> +	case LTC4245_3VSENSE:
> +		voltage = regval * 125; /* voltage in uV */
> +		current = (voltage * 10) / 25; /* sense resistor 2.5 mOhm */
> +		break;
> +	case LTC4245_VEESENSE:
> +		voltage = regval * 250; /* voltage in uV */
> +		current = voltage / 100; /* sense resistor 100 mOhm */
> +		break;
> +	default:
> +		/* If we get here, the developer messed up */
> +		WARN_ON_ONCE(1);
> +		current = 0;
> +		break;
> +	}
> +
> +	return current;
> +}
> +
> +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 u32 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 u32 current = ltc4245_get_current(dev, attr->index);
> +
> +	return snprintf(buf, PAGE_SIZE, "%u\n", current);
> +}
> +
> +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 u32 current = ltc4245_get_current(dev, attr->index);
> +	const u32 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 * current);
> +
> +	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 s32 reg = data->cregs[attr->index];
> +	const u32 mask = attr->nr;
> +
> +	if (unlikely(reg < 0)) {
> +		memset(buf, 0, PAGE_SIZE); /* user should not see old data */
> +		return 0;
> +	}
> +
> +	return snprintf(buf, PAGE_SIZE, "%u\n", (reg & mask) ? 1 : 0);
> +}
> +
> +/* 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)
> +
> +/* 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_VOLTAGE(in9_input,			LTC4245_GPIOADC1);
> +LTC4245_VOLTAGE(in10_input,			LTC4245_GPIOADC2);
> +LTC4245_VOLTAGE(in11_input,			LTC4245_GPIOADC3);
> +
> +/* 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_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_in10_input.dev_attr.attr,
> +	&sensor_dev_attr_in11_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_group ltc4245_group = {
> +	.attrs = ltc4245_attributes,
> +};
> +
> +static int ltc4245_probe(struct i2c_client *client,
> +			 const struct i2c_device_id *id)
> +{
> +	struct ltc4245_data *data;
> +	int ret;
> +
> +	data = kzalloc(sizeof(*data), GFP_KERNEL);
> +
> +	if (!data) {
> +		ret = -ENOMEM;
> +		goto out_kzalloc;
> +	}
> +
> +	i2c_set_clientdata(client, data);
> +	mutex_init(&data->update_lock);
> +
> +	/* Initialize the LTC4245 chip */
> +	/* TODO */
> +
> +	/* Register sysfs hooks */
> +	ret = sysfs_create_group(&client->dev.kobj, &ltc4245_group);
> +
> +	if (ret)
> +		goto out_sysfs_create_group;
> +
> +	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, &ltc4245_group);
> +out_sysfs_create_group:
> +	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);
> +	sysfs_remove_group(&client->dev.kobj, &ltc4245_group);
> +
> +	kfree(data);
> +
> +	return 0;
> +}
> +
> +/* Check that some bits in a control register appear at all possible
> + * locations without changing value
> + *
> + * @client: the i2c client to use
> + * @reg: the register to read
> + * @bits: the bits to check (0xff checks all bits,
> + *                           0x03 checks only the last two bits)
> + *
> + * return -ENODEV if the register value doesn't stay constant at all
> + * possible addresses
> + *
> + * return 0 for success
> + */
> +static int ltc4245_check_control_reg(struct i2c_client *client, u8 reg, u8 bits)
> +{
> +	int i;
> +	s32 v, voff1, voff2;
> +
> +	v = ltc4245_read_reg(client, reg) & bits;
> +
> +	if (v < 0)
> +		return -ENODEV;
> +
> +	for (i = 0x00; i < 0xff; i += 0x20) {
> +		voff1 = ltc4245_read_reg(client, reg + i) & bits;
> +		voff2 = ltc4245_read_reg(client, reg + i + 0x08) & bits;
> +
> +		if (voff1 < 0 || voff2 < 0 || v != voff1 || v != voff2)
> +			return -ENODEV;
> +	}
> +
> +	return 0;
> +}
> +
> +static int ltc4245_detect(struct i2c_client *client,
> +			  int kind,
> +			  struct i2c_board_info *info)
> +{
> +	struct i2c_adapter *adapter = client->adapter;
> +
> +	if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA))
> +		return -ENODEV;
> +
> +	if (kind < 0) {		/* probed detection - check the chip type */
> +		s32 v;		/* 8 bits from the chip, or -ERRNO */
> +
> +		/* Chip registers 0x00-0x07 are control registers
> +		 * Chip registers 0x10-0x1f are data registers
> +		 *
> +		 * Address bits b7-b5 are ignored. This makes the chip "repeat"
> +		 * in steps of 0x20. Any control registers should appear with
> +		 * the same values across all duplicated addresses.
> +		 *
> +		 * Register 0x02 bit b2 is reserved, expect 0
> +		 * Register 0x07 bits b7 to b4 are reserved, expect 0
> +		 *
> +		 * Registers 0x01, 0x02 are control registers and should not
> +		 * change on their own.
> +		 *
> +		 * Register 0x06 bits b6 and b7 are control bits, and should
> +		 * not change on their own.
> +		 *
> +		 * Register 0x07 bits b3 to b0 are control bits, and should
> +		 * not change on their own.
> +		 */
> +
> +		/* read register 0x02 reserved bit, expect 0 */
> +		v = ltc4245_read_reg(client, LTC4245_CONTROL);
> +		if (v < 0 || (v & 0x04) != 0)
> +			return -ENODEV;
> +
> +		/* read register 0x07 reserved bits, expect 0 */
> +		v = ltc4245_read_reg(client, LTC4245_ADCADR);
> +		if (v < 0 || (v & 0xf0) != 0)
> +			return -ENODEV;
> +
> +		/* check that the alert register appears at all locations */
> +		if (ltc4245_check_control_reg(client, LTC4245_ALERT, 0xff))
> +			return -ENODEV;
> +
> +		/* check that the control register appears at all locations */
> +		if (ltc4245_check_control_reg(client, LTC4245_CONTROL, 0xff))
> +			return -ENODEV;
> +
> +		/* check that register 0x06 bits b6 and b7 stay constant */
> +		if (ltc4245_check_control_reg(client, LTC4245_GPIO, 0xc0))
> +			return -ENODEV;
> +
> +		/* check that register 0x07 bits b3-b0 stay constant */
> +		if (ltc4245_check_control_reg(client, LTC4245_ADCADR, 0x0f))
> +			return -ENODEV;
> +	}
> +
> +	strlcpy(info->type, "ltc4245", I2C_NAME_SIZE);
> +	pr_info("ltc4245: %s on i2c-%u address 0x%02x\n",
> +			kind < 0 ? "probed" : "forced",
> +			adapter->nr, client->addr);
> +
> +	return 0;
> +}
> +
> +static const struct i2c_device_id ltc4245_id[] = {
> +	{ "ltc4245", ltc4245 },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(i2c, ltc4245_id);
> +
> +/* This is the driver that will be inserted */
> +static struct i2c_driver ltc4245_driver = {
> +	.class		= I2C_CLASS_HWMON,
> +	.driver = {
> +		.name	= "ltc4245",
> +	},
> +	.probe		= ltc4245_probe,
> +	.remove		= ltc4245_remove,
> +	.id_table	= ltc4245_id,
> +	.detect		= ltc4245_detect,
> +	.address_data	= &addr_data,
> +};
> +
> +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 at ovro.caltech.edu>");
> +MODULE_DESCRIPTION("LTC4245 driver");
> +MODULE_LICENSE("GPL");
> +
> +module_init(ltc4245_init);
> +module_exit(ltc4245_exit);




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