RE: [PATCH v4 2/2] hwmon: max31827: add MAX31827 driver

[Matyas, Daniel]

-----Original Message-----
From: Guenter Roeck <groeck7@xxxxxxxxx> On Behalf Of Guenter Roeck
Sent: Thursday, May 4, 2023 4:22 PM
To: Matyas, Daniel <Daniel.Matyas@xxxxxxxxxx>
Cc: Jean Delvare <jdelvare@xxxxxxxx>; Rob Herring <robh+dt@xxxxxxxxxx>; Krzysztof Kozlowski <krzysztof.kozlowski+dt@xxxxxxxxxx>; Jonathan Corbet <corbet@xxxxxxx>; linux-hwmon@xxxxxxxxxxxxxxx; devicetree@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; linux-doc@xxxxxxxxxxxxxxx
Subject: Re: [PATCH v4 2/2] hwmon: max31827: add MAX31827 driver

[External]

On 5/4/23 02:39, Daniel Matyas wrote:
> MAX31827 is a low-power temperature switch with I2C interface.
> 
> The device is a ±1°C accuracy from -40°C to +125°C
> (12 bits) local temperature switch and sensor with I2C/SM- Bus 
> interface. The combination of small 6-bump wafer-lev- el package (WLP) 
> and high accuracy makes this temper- ature sensor/switch ideal for a 
> wide range of applications.
> 
> Signed-off-by: Daniel Matyas <daniel.matyas@xxxxxxxxxx>

Thanks to missing change log, this review is incomplete and just mentions a few obvious problems.

Should I write the changelog as a cover letter or should I just add it at the end of the usual commit message?

> ---
>   Documentation/hwmon/index.rst    |   1 +
>   Documentation/hwmon/max31827.rst |  83 ++++++
>   MAINTAINERS                      |   2 +
>   drivers/hwmon/Kconfig            |  11 +
>   drivers/hwmon/Makefile           |   2 +-
>   drivers/hwmon/max31827.c         | 428 +++++++++++++++++++++++++++++++
>   6 files changed, 526 insertions(+), 1 deletion(-)
>   create mode 100644 Documentation/hwmon/max31827.rst
>   create mode 100644 drivers/hwmon/max31827.c
> 
> diff --git a/Documentation/hwmon/index.rst 
> b/Documentation/hwmon/index.rst index f1fe75f596a5..965a830ea766 
> 100644
> --- a/Documentation/hwmon/index.rst
> +++ b/Documentation/hwmon/index.rst
> @@ -139,6 +139,7 @@ Hardware Monitoring Kernel Drivers
>      max31760
>      max31785
>      max31790
> +   max31827
>      max34440
>      max6620
>      max6639
> diff --git a/Documentation/hwmon/max31827.rst 
> b/Documentation/hwmon/max31827.rst
> new file mode 100644
> index 000000000000..5b94ad62baa3
> --- /dev/null
> +++ b/Documentation/hwmon/max31827.rst
> @@ -0,0 +1,83 @@
> +.. SPDX-License-Identifier: GPL-2.0
> +
> +Kernel driver max31827
> +======================
> +
> +Supported chips:
> +
> +  * Maxim MAX31827
> +
> +    Prefix: 'max31827'
> +
> +    Addresses scanned: I2C 0x40 - 0x5f
> +
> +    Datasheet: Publicly available at the Analog Devices website
> +
> +  * Maxim MAX31828
> +
> +    Prefix: 'max31828'
> +
> +    Addresses scanned: I2C 0x40 - 0x5f
> +
> +    Datasheet: Publicly available at the Analog Devices website
> +
> +  * Maxim MAX31829
> +
> +    Prefix: 'max31829'
> +
> +    Addresses scanned: I2C 0x40 - 0x5f
> +
> +    Datasheet: Publicly available at the Analog Devices website
> +
> +
> +Authors:
> +	- Daniel Matyas <daniel.matyas@xxxxxxxxxx>
> +
> +Description
> +-----------
> +
> +The chips supported by this driver are quite similar. The only 
> +difference between them is found in the default power-on behaviour of 
> +the chips. While the MAX31827's fault queue is set to 1, the other 
> +two chip's fault queue is set to 4. Besides this, the MAX31829's 
> +alarm active state is high, while the other two chip's alarms are 
> +active on low. It is important to note that the chips can be 
> +configured to operate in the same manner with 1 write operation to 
> +the configuration register. From here on, we will refer to all these chips as MAX31827.
> +
> +MAX31827 implements a temperature sensor with a 6 WLP packaging 
> +scheme. This sensor measures the temperature of the chip itself.
> +
> +MAX31827 has low and over temperature alarms with an effective value 
> +and a hysteresis value: -40 and -30 degrees for under temperature 
> +alarm and +100 and
> ++90 degrees for over temperature alarm.
> +
> +The alarm can be configured in comparator and interrupt mode. 
> +Currently only comparator mode is implemented. In Comparator mode, 
> +the OT/UT status bits have a value of 1 when the temperature rises 
> +above the TH value or falls below TL, which is also subject to the 
> +Fault Queue selection. OT status returns to 0 when the temperature drops below the TH_HYST value or when shutdown mode is entered.
> +Similarly, UT status returns to 0 when the temperature rises above 
> +TL_HYST value or when shutdown mode is entered.
> +
> +Putting the MAX31827 into shutdown mode also resets the OT/UT status 
> +bits. Note that if the mode is changed while OT/UT status bits are 
> +set, an OT/UT status reset may be required before it begins to behave 
> +normally. To prevent this, it is recommended to perform a read of the 
> +configuration/status register to clear the status bits before changing the operating mode.
> +
> +The conversions can be manual with the one-shot functionality and 
> +automatic with a set frequency. When powered on, the chip measures temperatures with 1 conv/s.
> +Enabling the device when it is already enabled has the side effect of 
> +setting the conversion frequency to 1 conv/s. The conversion time 
> +varies depending on the resolution. The conversion time doubles with 
> +every bit of increased resolution. For 10 bit resolution 35ms are 
> +needed, while for 12 bit resolution
> +(default) 140ms. When chip is in shutdown mode and a read operation 
> +is requested, one-shot is triggered, the device waits for 140 
> +(conversion time) + 1
> +(error) ms, and only after that is the temperature value register read.
> +
> +Notes
> +-----
> +
> +Currently fault queue, alarm polarity and resolution cannot be modified.
> +PEC is not implemented either.
> diff --git a/MAINTAINERS b/MAINTAINERS index 
> 0997a0490c97..fabc8869b13b 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -12541,6 +12541,8 @@ L:	linux-hwmon@xxxxxxxxxxxxxxx
>   S:	Supported
>   W:	http://ez.analog.com/community/linux-device-drivers
>   F:	Documentation/devicetree/bindings/hwmon/adi,max31827.yaml
> +F:	Documentation/hwmon/max31827.rst
> +F:	drivers/hwmon/max31827.c
>   
>   MAX6650 HARDWARE MONITOR AND FAN CONTROLLER DRIVER
>   L:	linux-hwmon@xxxxxxxxxxxxxxx
> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig index 
> 5b3b76477b0e..1e8546b3a8f2 100644
> --- a/drivers/hwmon/Kconfig
> +++ b/drivers/hwmon/Kconfig
> @@ -1097,6 +1097,17 @@ config SENSORS_MAX31760
>   	  This driver can also be built as a module. If so, the module
>   	  will be called max31760.
>   
> +config MAX31827
> +	tristate "MAX31827 low-power temperature switch and similar devices"
> +	depends on I2C
> +	select REGMAP_I2C
> +	help
> +	  If you say yes here you get support for MAX31827, MAX31828 and
> +	  MAX31829 low-power temperature switches and sensors connected with I2C.
> +
> +	  This driver can also be built as a module.  If so, the module
> +	  will be called max31827.
> +
>   config SENSORS_MAX6620
>   	tristate "Maxim MAX6620 fan controller"
>   	depends on I2C
> diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile index 
> 88712b5031c8..dfb9aaf979bb 100644
> --- a/drivers/hwmon/Makefile
> +++ b/drivers/hwmon/Makefile
> @@ -149,6 +149,7 @@ obj-$(CONFIG_SENSORS_MAX6642)	+= max6642.o
>   obj-$(CONFIG_SENSORS_MAX6650)	+= max6650.o
>   obj-$(CONFIG_SENSORS_MAX6697)	+= max6697.o
>   obj-$(CONFIG_SENSORS_MAX31790)	+= max31790.o
> +obj-$(CONFIG_MAX31827) += max31827.o
>   obj-$(CONFIG_SENSORS_MC13783_ADC)+= mc13783-adc.o
>   obj-$(CONFIG_SENSORS_MC34VR500)	+= mc34vr500.o
>   obj-$(CONFIG_SENSORS_MCP3021)	+= mcp3021.o
> @@ -223,4 +224,3 @@ obj-$(CONFIG_SENSORS_PECI)	+= peci/
>   obj-$(CONFIG_PMBUS)		+= pmbus/
>   
>   ccflags-$(CONFIG_HWMON_DEBUG_CHIP) := -DDEBUG
> -
> diff --git a/drivers/hwmon/max31827.c b/drivers/hwmon/max31827.c new 
> file mode 100644 index 000000000000..48ab62f76f7b
> --- /dev/null
> +++ b/drivers/hwmon/max31827.c
> @@ -0,0 +1,428 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * max31827.c - Support for Maxim Low-Power Switch
> + *
> + * Copyright (c) 2023 Daniel Matyas <daniel.matyas@xxxxxxxxxx>  */
> +
> +#include <linux/bitfield.h>
> +#include <linux/delay.h>
> +#include <linux/hwmon.h>
> +#include <linux/i2c.h>
> +#include <linux/mutex.h>
> +#include <linux/regmap.h>
> +
> +#define MAX31827_T_REG	0x0
> +#define MAX31827_CONFIGURATION_REG	0x2
> +#define MAX31827_TH_REG	0x4
> +#define MAX31827_TL_REG 0x6
> +#define MAX31827_TH_HYST_REG	0x8
> +#define MAX31827_TL_HYST_REG	0xA
> +
> +#define MAX31827_CONFIGURATION_1SHOT_MASK	BIT(0)
> +#define MAX31827_CONFIGURATION_CNV_RATE_MASK	GENMASK(3, 1)
> +#define MAX31827_CONFIGURATION_U_TEMP_STAT_MASK BIT(14) #define 
> +MAX31827_CONFIGURATION_O_TEMP_STAT_MASK BIT(15)
> +
> +#define MAX31827_12_BIT_CNV_TIME	141
> +
> +#define MAX31827_CNV_1_DIV_64_HZ	0x1
> +#define MAX31827_CNV_1_DIV_32_HZ	0x2
> +#define MAX31827_CNV_1_DIV_16_HZ	0x3
> +#define MAX31827_CNV_1_DIV_4_HZ		0x4
> +#define MAX31827_CNV_1_HZ	0x5
> +#define MAX31827_CNV_4_HZ	0x6
> +#define MAX31827_CNV_8_HZ	0x7
> +
> +#define LONG_MASK	0xFFFFFFFFFFFFFFFF
> +

This would be ULLONG_MAX, but I don't really see ..

> +#define MAX31827_16_BIT_TO_M_DGR(x)	((long)(~(~(x) & LONG_MASK)) * 1000 >> 4)

... the point here. Masking anything against 0xFFFFFFFFFFFFFFFF doesn't do any good, and the register values are really 13 bit wide with the upper 4 bit reflecting the sign. Using one of the sign_extend() variants would be more appropriate to calculate the temperature. I also don't understand the shift since temperature values are supposedly - per datasheet - aligned to bit 0.

> +#define MAX31827_M_DGR_TO_16_BIT(x)	(((x) << 4) / 1000)

Same here. This seems to drop the lower 4 temperature bits (fractions) for no good reason.

I am doing the shift, because the value of LSB is not 1, but 0.0625. Thus, I am dividing by 16 (>> 4) when converting to milli-degrees, and I am multiplying by 16 (<< 4), when converting to 16 bit format.

> +#define MAX31827_DEVICE_ENABLE(x)	((x) ? 0xA : 0x0)
> +
> +struct max31827_state {
> +	/*
> +	 * Prevent simultaneous access to the i2c client.
> +	 */
> +	struct mutex lock;
> +	struct regmap *regmap;
> +	bool enable;
> +};
> +
> +static const struct regmap_config max31827_regmap = {
> +	.reg_bits = 8,
> +	.val_bits = 16,
> +	.max_register = 0xA,
> +};
> +
> +static int write_alarm_val(struct max31827_state *st, unsigned int reg,
> +			   long val)
> +{
> +	unsigned int cfg;
> +	unsigned int tmp;
> +	int ret;
> +
> +	val = MAX31827_M_DGR_TO_16_BIT(val);
> +
> +	/*
> +	 * Before the Temperature Threshold Alarm and Alarm Hysteresis Threshold
> +	 * register values are changed over I2C, the part must be in shutdown
> +	 * mode.
> +	 *
> +	 * Mutex is used to ensure, that some other process doesn't change the
> +	 * configuration register.
> +	 */
> +	mutex_lock(&st->lock);
> +
> +	if (!st->enable)
> +		return regmap_write(st->regmap, reg, val);
> +

Hang guaranteed here.

> +	ret = regmap_read(st->regmap, MAX31827_CONFIGURATION_REG, &cfg);
> +	if (ret)
> +		return ret;

... and here and everywhere else where the function returns without releasing the mutex.

> +
> +	tmp = cfg & ~(MAX31827_CONFIGURATION_1SHOT_MASK |
> +		      MAX31827_CONFIGURATION_CNV_RATE_MASK);
> +	ret = regmap_write(st->regmap, MAX31827_CONFIGURATION_REG, tmp);
> +	if (ret)
> +		return ret;
> +
> +	ret = regmap_write(st->regmap, reg, val);
> +	if (ret)
> +		return ret;
> +
> +	ret = regmap_write(st->regmap, MAX31827_CONFIGURATION_REG, cfg);
> +
> +	mutex_unlock(&st->lock);
> +
> +	return ret;
> +}
> +
> +static umode_t max31827_is_visible(const void *state,
> +				   enum hwmon_sensor_types type, u32 attr,
> +				   int channel)
> +{
> +	if (type == hwmon_temp) {
> +		switch (attr) {
> +		case hwmon_temp_enable:
> +		case hwmon_temp_max:
> +		case hwmon_temp_min:
> +		case hwmon_temp_max_hyst:
> +		case hwmon_temp_min_hyst:
> +			return 0644;
> +		case hwmon_temp_input:
> +		case hwmon_temp_min_alarm:
> +		case hwmon_temp_max_alarm:
> +			return 0444;
> +		default:
> +			return 0;
> +		}
> +	} else if (type == hwmon_chip) {
> +		if (attr == hwmon_chip_update_interval)
> +			return 0644;
> +	}
> +
> +	return 0;
> +}
> +
> +static int max31827_read(struct device *dev, enum hwmon_sensor_types type,
> +			 u32 attr, int channel, long *val) {
> +	struct max31827_state *st = dev_get_drvdata(dev);
> +	unsigned int uval;
> +	int ret;
> +
> +	switch (type) {
> +	case hwmon_temp:
> +		switch (attr) {
> +		case hwmon_temp_enable:
> +			ret = regmap_read(st->regmap,
> +					  MAX31827_CONFIGURATION_REG, &uval);
> +			uval = FIELD_GET(MAX31827_CONFIGURATION_1SHOT_MASK |
> +					 MAX31827_CONFIGURATION_CNV_RATE_MASK,
> +					 uval);
> +			*val = !!uval;
> +
> +			break;
> +		case hwmon_temp_input:
> +			mutex_lock(&st->lock);
> +
> +			if (!st->enable) {
> +				/*
> +				 * This operation requires mutex protection,
> +				 * because the chip configuration should not
> +				 * be changed during the conversion process.
> +				 */
> +
> +				ret = regmap_update_bits(st->regmap,
> +							 MAX31827_CONFIGURATION_REG,
> +							 MAX31827_CONFIGURATION_1SHOT_MASK,
> +							 1);
> +				if (ret)
> +					return ret;

Another hang due to lacking mutex_unlock().

> +
> +				msleep(MAX31827_12_BIT_CNV_TIME);
> +			}
> +			ret = regmap_read(st->regmap, MAX31827_T_REG, &uval);
> +
> +			mutex_unlock(&st->lock);
> +
> +			*val = MAX31827_16_BIT_TO_M_DGR(uval);
> +
> +			break;
> +		case hwmon_temp_max:
> +			ret = regmap_read(st->regmap, MAX31827_TH_REG, &uval);
> +			*val = MAX31827_16_BIT_TO_M_DGR(uval);
> +			break;
> +		case hwmon_temp_max_hyst:
> +			ret = regmap_read(st->regmap, MAX31827_TH_HYST_REG,
> +					  &uval);
> +			*val = MAX31827_16_BIT_TO_M_DGR(uval);
> +			break;
> +		case hwmon_temp_max_alarm:
> +			ret = regmap_read(st->regmap,
> +					  MAX31827_CONFIGURATION_REG, &uval);
> +			*val = FIELD_GET(MAX31827_CONFIGURATION_O_TEMP_STAT_MASK,
> +					 uval);
> +			break;
> +		case hwmon_temp_min:
> +			ret = regmap_read(st->regmap, MAX31827_TL_REG, &uval);
> +			*val = MAX31827_16_BIT_TO_M_DGR(uval);
> +			break;
> +		case hwmon_temp_min_hyst:
> +			ret = regmap_read(st->regmap, MAX31827_TL_HYST_REG,
> +					  &uval);
> +			*val = MAX31827_16_BIT_TO_M_DGR(uval);
> +			break;
> +		case hwmon_temp_min_alarm:
> +			ret = regmap_read(st->regmap,
> +					  MAX31827_CONFIGURATION_REG, &uval);
> +			*val = FIELD_GET(MAX31827_CONFIGURATION_U_TEMP_STAT_MASK,
> +					 uval);
> +			break;
> +		default:
> +			ret = -EOPNOTSUPP;
> +			break;
> +		}
> +
> +		break;
> +
> +	case hwmon_chip:
> +		if (attr == hwmon_chip_update_interval) {
> +			ret = regmap_read(st->regmap,
> +					  MAX31827_CONFIGURATION_REG, &uval);
> +			uval = FIELD_GET(MAX31827_CONFIGURATION_CNV_RATE_MASK,
> +					 uval);
> +			switch (uval) {
> +			case MAX31827_CNV_1_DIV_64_HZ:
> +				*val = 64000;
> +				break;
> +			case MAX31827_CNV_1_DIV_32_HZ:
> +				*val = 32000;
> +				break;
> +			case MAX31827_CNV_1_DIV_16_HZ:
> +				*val = 16000;
> +				break;
> +			case MAX31827_CNV_1_DIV_4_HZ:
> +				*val = 4000;
> +				break;
> +			case MAX31827_CNV_1_HZ:
> +				*val = 1000;
> +				break;
> +			case MAX31827_CNV_4_HZ:
> +				*val = 250;
> +				break;
> +			case MAX31827_CNV_8_HZ:
> +				*val = 125;
> +				break;
> +			default:
> +				*val = 0;
> +				break;
> +			}
> +		}
> +		break;
> +
> +	default:
> +		ret = -EOPNOTSUPP;
> +		break;
> +	}
> +
> +	if (ret)
> +		return ret;
> +
> +	return 0;

just
	return ret;

would do the same.

> +}
> +
> +static int max31827_write(struct device *dev, enum hwmon_sensor_types type,
> +			  u32 attr, int channel, long val) {
> +	struct max31827_state *st = dev_get_drvdata(dev);
> +
> +	switch (type) {
> +	case hwmon_temp:
> +		switch (attr) {
> +		case hwmon_temp_enable:
> +			if (val >> 1)
> +				return -EOPNOTSUPP;
> +
> +			st->enable = val;
> +
> +			return regmap_update_bits(st->regmap,
> +						  MAX31827_CONFIGURATION_REG,
> +						  MAX31827_CONFIGURATION_1SHOT_MASK |
> +						  MAX31827_CONFIGURATION_CNV_RATE_MASK,
> +						  MAX31827_DEVICE_ENABLE(val));
> +
> +		case hwmon_temp_max:
> +			return write_alarm_val(st, MAX31827_TH_REG, val);
> +
> +		case hwmon_temp_max_hyst:
> +			return write_alarm_val(st, MAX31827_TH_HYST_REG, val);
> +
> +		case hwmon_temp_min:
> +			return write_alarm_val(st, MAX31827_TL_REG, val);
> +
> +		case hwmon_temp_min_hyst:
> +			return write_alarm_val(st, MAX31827_TL_HYST_REG, val);
> +
> +		default:
> +			return -EOPNOTSUPP;
> +		}
> +
> +	case hwmon_chip:
> +		if (attr == hwmon_chip_update_interval) {
> +			switch (val) {
> +			case 125:
> +				val = MAX31827_CNV_8_HZ;
> +				break;
> +			case 250:
> +				val = MAX31827_CNV_4_HZ;
> +				break;
> +			case 1000:
> +				val = MAX31827_CNV_1_HZ;
> +				break;
> +			case 4000:
> +				val = MAX31827_CNV_1_DIV_4_HZ;
> +				break;
> +			case 16000:
> +				val = MAX31827_CNV_1_DIV_16_HZ;
> +				break;
> +			case 32000:
> +				val = MAX31827_CNV_1_DIV_32_HZ;
> +				break;
> +			case 64000:
> +				val = MAX31827_CNV_1_DIV_64_HZ;
> +				break;
> +			default:
> +				val = 0;
> +				break;
> +			}
> +
> +			if (!val)
> +				return -EOPNOTSUPP;

Might as well return from default: above.

True, but I wrote it like this for consistency: in a switch statement I am either returning, either breaking. Should I still change it?

> +
> +			val = FIELD_PREP(MAX31827_CONFIGURATION_CNV_RATE_MASK,
> +					 val);
> +
> +			return regmap_update_bits(st->regmap,
> +						  MAX31827_CONFIGURATION_REG,
> +						  MAX31827_CONFIGURATION_CNV_RATE_MASK,
> +						  val);
> +		}
> +		break;
> +
> +	default:
> +		return -EOPNOTSUPP;
> +	}
> +
> +	return -EOPNOTSUPP;
> +}
> +
> +static int max31827_init_client(struct max31827_state *st) {
> +	st->enable = true;
> +
> +	return regmap_update_bits(st->regmap, MAX31827_CONFIGURATION_REG,
> +				  MAX31827_CONFIGURATION_1SHOT_MASK |
> +					  MAX31827_CONFIGURATION_CNV_RATE_MASK,
> +				  MAX31827_DEVICE_ENABLE(1));
> +}
> +
> +static const struct hwmon_channel_info *max31827_info[] = {
> +	HWMON_CHANNEL_INFO(temp, HWMON_T_ENABLE | HWMON_T_INPUT | HWMON_T_MIN |
> +					 HWMON_T_MIN_HYST | HWMON_T_MIN_ALARM |
> +					 HWMON_T_MAX | HWMON_T_MAX_HYST |
> +					 HWMON_T_MAX_ALARM),
> +	HWMON_CHANNEL_INFO(chip, HWMON_C_UPDATE_INTERVAL),
> +	NULL,
> +};
> +
> +static const struct hwmon_ops max31827_hwmon_ops = {
> +	.is_visible = max31827_is_visible,
> +	.read = max31827_read,
> +	.write = max31827_write,
> +};
> +
> +static const struct hwmon_chip_info max31827_chip_info = {
> +	.ops = &max31827_hwmon_ops,
> +	.info = max31827_info,
> +};
> +
> +static int max31827_probe(struct i2c_client *client) {
> +	struct device *dev = &client->dev;
> +	struct device *hwmon_dev;
> +	struct max31827_state *st;
> +	int err;
> +
> +	if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_WORD_DATA))
> +		return -EOPNOTSUPP;
> +
> +	st = devm_kzalloc(dev, sizeof(*st), GFP_KERNEL);
> +	if (!st)
> +		return -ENOMEM;
> +
> +	mutex_init(&st->lock);
> +
> +	st->regmap = devm_regmap_init_i2c(client, &max31827_regmap);
> +	if (IS_ERR(st->regmap))
> +		return dev_err_probe(dev, PTR_ERR(st->regmap),
> +				     "Failed to allocate regmap.\n");
> +
> +	err = max31827_init_client(st);
> +	if (err)
> +		return err;
> +
> +	hwmon_dev = devm_hwmon_device_register_with_info(dev, client->name, st,
> +							 &max31827_chip_info,
> +							 NULL);
> +
> +	return PTR_ERR_OR_ZERO(hwmon_dev);
> +}
> +
> +static const struct i2c_device_id max31827_i2c_ids[] = {
> +	{ "max31827", 0 },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(i2c, max31827_i2c_ids);
> +
> +static const struct of_device_id max31827_of_match[] = {
> +	{ .compatible = "max31827" },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(of, max31827_of_match);
> +
> +static struct i2c_driver max31827_driver = {
> +	.class = I2C_CLASS_HWMON,
> +	.driver = {
> +		.name = "max31827",
> +		.of_match_table = max31827_of_match,
> +	},
> +	.probe_new = max31827_probe,
> +	.id_table = max31827_i2c_ids,
> +};
> +module_i2c_driver(max31827_driver);
> +
> +MODULE_AUTHOR("Daniel Matyas <daniel.matyas@xxxxxxxxxx>"); 
> +MODULE_DESCRIPTION("Maxim MAX31827 low-power temperature switch 
> +driver"); MODULE_LICENSE("GPL");