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Sender: Guenter Roeck <groeck7@gmail.com>
Date:   Thu, 28 Sep 2023 04:58:56 -0700
From:   Guenter Roeck <linux@roeck-us.net>
To:     Antoniu Miclaus <antoniu.miclaus@analog.com>
Cc:     Jean Delvare <jdelvare@suse.com>, Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Conor Dooley <conor+dt@kernel.org>,
        Jonathan Corbet <corbet@lwn.net>, linux-hwmon@vger.kernel.org,
        devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-doc@vger.kernel.org
Subject: Re: [PATCH 2/2] drivers: hwmon: ltc2991: add driver support
Message-ID: <441fd06a-47c6-4415-9f48-60bde6ce84fd@roeck-us.net>
References: <20230926140544.80934-1-antoniu.miclaus@analog.com>
 <20230926140544.80934-2-antoniu.miclaus@analog.com>
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In-Reply-To: <20230926140544.80934-2-antoniu.miclaus@analog.com>
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On Tue, Sep 26, 2023 at 05:05:30PM +0300, Antoniu Miclaus wrote:
> Add support for LTC2991 Octal I2C Voltage, Current, and Temperature
> Monitor.
> 
> The LTC2991 is used to monitor system temperatures, voltages and
> currents. Through the I 2C serial interface, theeight monitors can
> individually measure supply voltages and can be paired for
> differential measurements of current sense resistors or temperature
> sensing transistors. Additional measurements include internal
> temperature and internal VCC.
> 
> Signed-off-by: Antoniu Miclaus <antoniu.miclaus@analog.com>
> ---
>  Documentation/hwmon/index.rst   |   1 +
>  Documentation/hwmon/ltc2991.rst |  43 +++
>  MAINTAINERS                     |   8 +
>  drivers/hwmon/Kconfig           |  11 +
>  drivers/hwmon/Makefile          |   1 +
>  drivers/hwmon/ltc2991.c         | 490 ++++++++++++++++++++++++++++++++
>  6 files changed, 554 insertions(+)
>  create mode 100644 Documentation/hwmon/ltc2991.rst
>  create mode 100644 drivers/hwmon/ltc2991.c
> 
> diff --git a/Documentation/hwmon/index.rst b/Documentation/hwmon/index.rst
> index 88dadea85cfc..0ec96abe3f7d 100644
> --- a/Documentation/hwmon/index.rst
> +++ b/Documentation/hwmon/index.rst
> @@ -121,6 +121,7 @@ Hardware Monitoring Kernel Drivers
>     ltc2947
>     ltc2978
>     ltc2990
> +   ltc2991
>     ltc3815
>     ltc4151
>     ltc4215
> diff --git a/Documentation/hwmon/ltc2991.rst b/Documentation/hwmon/ltc2991.rst
> new file mode 100644
> index 000000000000..9ab29dd85012
> --- /dev/null
> +++ b/Documentation/hwmon/ltc2991.rst
> @@ -0,0 +1,43 @@
> +.. SPDX-License-Identifier: GPL-2.0
> +
> +Kernel driver ltc2991
> +=====================
> +
> +Supported chips:
> +
> +  * Analog Devices LTC2991
> +
> +    Prefix: 'ltc2991'
> +
> +    Addresses scanned: I2C 0x48 - 0x4f
> +
> +    Datasheet: https://www.analog.com/media/en/technical-documentation/data-sheets/2991ff.pdf
> +
> +Authors:
> +
> +  - Antoniu Miclaus <antoniu.miclaus@analog.com>
> +
> +
> +Description
> +-----------
> +
> +This driver supports hardware monitoring for Analog Devices LTC2991 Octal I2C
> +Voltage, Current and Temperature Monitor.
> +
> +The LTC2991 is used to monitor system temperatures, voltages and currents.
> +Through the I2C serial interface, the eight monitors can individually measure
> +supply voltages and can be paired for differential measurements of current sense
> +resistors or temperature sensing transistors. Additional measurements include
> +internal temperatureand internal VCC.
> +
> +
> +sysfs-Interface
> +-------------
> +
> +The following attributes are supported. Limits are read-only.
> +
> +=============== =================
> +inX_input:      voltage input
> +currX_input:    current input
> +tempX_input:    temperature input
> +=============== =================
> diff --git a/MAINTAINERS b/MAINTAINERS
> index b19995690904..98dd8a8e1f84 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -12451,6 +12451,14 @@ F:	drivers/hwmon/ltc2947-i2c.c
>  F:	drivers/hwmon/ltc2947-spi.c
>  F:	drivers/hwmon/ltc2947.h
>  
> +LTC2991 HARDWARE MONITOR DRIVER
> +M:	Antoniu Miclaus <antoniu.miclaus@analog.com>
> +L:	linux-hwmon@vger.kernel.org
> +S:	Supported
> +W:	https://ez.analog.com/linux-software-drivers
> +F:	Documentation/devicetree/bindings/hwmon/adi,ltc2991.yaml
> +F:	drivers/hwmon/ltc2991.c
> +
>  LTC2983 IIO TEMPERATURE DRIVER
>  M:	Nuno S? <nuno.sa@analog.com>
>  L:	linux-iio@vger.kernel.org
> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> index ec38c8892158..818a67328fcd 100644
> --- a/drivers/hwmon/Kconfig
> +++ b/drivers/hwmon/Kconfig
> @@ -932,6 +932,17 @@ config SENSORS_LTC2990
>  	  This driver can also be built as a module. If so, the module will
>  	  be called ltc2990.
>  
> +config SENSORS_LTC2991
> +	tristate "Analog Devices LTC2991"
> +	depends on I2C
> +	help
> +	  If you say yes here you get support for Analog Devices LTC2991
> +	  Octal I2C Voltage, Current, and Temperature Monitor. The LTC2991
> +	  supports a combination of voltage, current and temperature monitoring.
> +
> +	  This driver can also be built as a module. If so, the module will
> +	  be called ltc2991.
> +
>  config SENSORS_LTC2992
>  	tristate "Linear Technology LTC2992"
>  	depends on I2C
> diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
> index 4ac9452b5430..f324d057535a 100644
> --- a/drivers/hwmon/Makefile
> +++ b/drivers/hwmon/Makefile
> @@ -127,6 +127,7 @@ obj-$(CONFIG_SENSORS_LTC2947)	+= ltc2947-core.o
>  obj-$(CONFIG_SENSORS_LTC2947_I2C) += ltc2947-i2c.o
>  obj-$(CONFIG_SENSORS_LTC2947_SPI) += ltc2947-spi.o
>  obj-$(CONFIG_SENSORS_LTC2990)	+= ltc2990.o
> +obj-$(CONFIG_SENSORS_LTC2991)	+= ltc2991.o
>  obj-$(CONFIG_SENSORS_LTC2992)	+= ltc2992.o
>  obj-$(CONFIG_SENSORS_LTC4151)	+= ltc4151.o
>  obj-$(CONFIG_SENSORS_LTC4215)	+= ltc4215.o
> diff --git a/drivers/hwmon/ltc2991.c b/drivers/hwmon/ltc2991.c
> new file mode 100644
> index 000000000000..51a60ca8c24e
> --- /dev/null
> +++ b/drivers/hwmon/ltc2991.c
> @@ -0,0 +1,490 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) 2023 Analog Devices, Inc.
> + * Author: Antoniu Miclaus <antoniu.miclaus@analog.com>
> + */
> +
> +#include <linux/bitops.h>
> +#include <linux/err.h>
> +#include <linux/hwmon.h>
> +#include <linux/hwmon-sysfs.h>
> +#include <linux/i2c.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/property.h>
> +#include <linux/regmap.h>
> +#include <linux/regulator/consumer.h>
> +
> +#define LTC2991_STATUS_LOW		0x00
> +#define LTC2991_CH_EN_TRIGGER		0x01
> +#define LTC2991_V1_V4_CTRL		0x06
> +#define LTC2991_V5_V8_CTRL		0x07
> +#define LTC2991_PWM_TH_LSB_T_INT	0x08
> +#define LTC2991_PWM_TH_MSB		0x09
> +#define LTC2991_CHANNEL_V_MSB(x)	(0x0A + ((x) * 2))
> +#define LTC2991_CHANNEL_T_MSB(x)	(0x0A + ((x) * 4))
> +#define LTC2991_CHANNEL_C_MSB(x)	(0x0C + ((x) * 4))
> +#define LTC2991_T_INT_MSB		0x1A
> +#define LTC2991_VCC_MSB			0x1C
> +
> +#define LTC2991_V7_V8_EN		BIT(7)
> +#define LTC2991_V5_V6_EN		BIT(6)
> +#define LTC2991_V3_V4_EN		BIT(5)
> +#define LTC2991_V1_V2_EN		BIT(4)
> +#define LTC2991_T_INT_VCC_EN		BIT(3)
> +
> +#define LTC2991_V3_V4_FILT_EN		BIT(7)
> +#define LTC2991_V3_V4_TEMP_EN		BIT(5)
> +#define LTC2991_V3_V4_DIFF_EN		BIT(4)
> +#define LTC2991_V1_V2_FILT_EN		BIT(3)
> +#define LTC2991_V1_V2_TEMP_EN		BIT(1)
> +#define LTC2991_V1_V2_DIFF_EN		BIT(0)
> +
> +#define LTC2991_V7_V8_FILT_EN		BIT(7)
> +#define LTC2991_V7_V8_TEMP_EN		BIT(5)
> +#define LTC2991_V7_V8_DIFF_EN		BIT(4)
> +#define LTC2991_V5_V6_FILT_EN		BIT(7)
> +#define LTC2991_V5_V6_TEMP_EN		BIT(5)
> +#define LTC2991_V5_V6_DIFF_EN		BIT(4)
> +
> +#define LTC2991_REPEAT_ACQ_EN		BIT(4)
> +#define LTC2991_T_INT_FILT_EN		BIT(3)
> +
> +#define LTC2991_MAX_CHANNEL		4
> +#define LTC2991_T_INT_CH_NR		4
> +#define LTC2991_VCC_CH_NR		0
> +
> +static const char *const label_voltages[] = {
> +	"vcc",
> +	"voltage1",
> +	"voltage2",
> +	"voltage3",
> +	"voltage4",
> +	"voltage5",
> +	"voltage6",
> +	"voltage7",
> +	"voltage8"
> +};
> +
> +static const char *const label_temp[] = {
> +	"t1",
> +	"t2",
> +	"t3",
> +	"t4",
> +	"t_int"
> +};
> +
> +static const char *const label_curr[] = {
> +	"v1-v2",
> +	"v3-v4",
> +	"v5-v6",
> +	"v7-v8"

Those labels are all but pointless. Please drop.

> +};
> +
> +struct ltc2991_state {
> +	struct i2c_client	*client;
> +	struct regmap		*regmap;
> +	u32			r_sense_mohm[LTC2991_MAX_CHANNEL];
> +	bool			temp_en[LTC2991_MAX_CHANNEL];
> +};
> +
> +static int ltc2991_read_reg(struct ltc2991_state *st, u8 addr, u8 reg_len,
> +			    int *val)
> +{
> +	u8 regvals[2];
> +	int ret;
> +	int i;
> +
> +	ret = regmap_bulk_read(st->regmap, addr, regvals, reg_len);
> +	if (ret)
> +		return ret;
> +
> +	*val = 0;
> +	for (i = 0; i < reg_len; i++)
> +		*val |= regvals[reg_len - i - 1] << (i * 8);
> +
> +	return 0;
> +}
> +
> +static int ltc2991_get_voltage(struct ltc2991_state *st, u32 reg, long *val)
> +{
> +	int reg_val, ret, offset = 0;
> +
> +	ret = ltc2991_read_reg(st, reg, 2, &reg_val);
> +	if (ret)
> +		return ret;
> +
> +	if (reg == LTC2991_VCC_MSB)
> +		/* Vcc 2.5V offset */
> +		offset = 2500;
> +
> +	/* Vx, 305.18uV/LSB */
> +	*val = DIV_ROUND_CLOSEST(sign_extend32(reg_val, 14) * 30518,
> +				 1000 * 100) + offset;
> +
> +	return 0;
> +}
> +
> +static int ltc2991_read_in(struct device *dev, u32 attr, int channel, long *val)
> +{
> +	struct ltc2991_state *st = dev_get_drvdata(dev);
> +	u32 reg;
> +
> +	switch (attr) {
> +	case hwmon_in_input:
> +		if (channel == LTC2991_VCC_CH_NR)
> +			reg = LTC2991_VCC_MSB;
> +		else
> +			reg = LTC2991_CHANNEL_V_MSB(channel - 1);
> +		break;
> +	default:
> +		return -EOPNOTSUPP;
> +	}
> +
> +	return ltc2991_get_voltage(st, reg, val);

I see no value having this code here. WHy not in the case statement above ?

> +}
> +
> +static int ltc2991_get_curr(struct ltc2991_state *st, u32 reg, int channel,
> +			    long *val)
> +{
> +	int reg_val, ret;
> +
> +	ret = ltc2991_read_reg(st, reg, 2, &reg_val);
> +	if (ret)
> +		return ret;
> +
> +	/* Vx-Vy, 19.075uV/LSB */
> +	*val = DIV_ROUND_CLOSEST(sign_extend32(reg_val, 14) * 19075, 1000)
> +				 / st->r_sense_mohm[channel];
> +
> +	return 0;
> +}
> +
> +static int ltc2991_read_curr(struct device *dev, u32 attr, int channel,
> +			     long *val)
> +{
> +	struct ltc2991_state *st = dev_get_drvdata(dev);
> +	u32 reg;
> +
> +	switch (attr) {
> +	case hwmon_curr_input:
> +		reg = LTC2991_CHANNEL_C_MSB(channel);
> +		break;
> +	default:
> +		return -EOPNOTSUPP;
> +	}
> +
> +	return ltc2991_get_curr(st, reg, channel, val);

Even less value than above. That would only make sense if there were
more attributes to read.

> +}
> +
> +static int ltc2991_get_temp(struct ltc2991_state *st, u32 reg, int channel,
> +			    long *val)
> +{
> +	int reg_val, ret;
> +
> +	ret = ltc2991_read_reg(st, reg, 2, &reg_val);
> +	if (ret)
> +		return ret;
> +
> +	/* Temp LSB = 0.0625 Degrees */
> +	*val = DIV_ROUND_CLOSEST(sign_extend32(reg_val, 12) * 1000, 16);
> +
> +	return 0;
> +}
> +
> +static int ltc2991_read_temp(struct device *dev, u32 attr, int channel,
> +			     long *val)
> +{
> +	struct ltc2991_state *st = dev_get_drvdata(dev);
> +	u32 reg;
> +
> +	switch (attr) {
> +	case hwmon_temp_input:
> +		if (channel == LTC2991_T_INT_CH_NR)
> +			reg = LTC2991_T_INT_MSB;
> +		else
> +			reg = LTC2991_CHANNEL_T_MSB(channel);
> +		break;
> +	default:
> +		return -EOPNOTSUPP;
> +	}
> +
> +	return ltc2991_get_temp(st, reg, channel, val);

And again.

> +}
> +
> +static int ltc2991_read(struct device *dev, enum hwmon_sensor_types type, u32 attr, int channel,
> +			long *val)
> +{
> +	switch (type) {
> +	case hwmon_in:
> +		return ltc2991_read_in(dev, attr, channel, val);
> +	case hwmon_curr:
> +		return ltc2991_read_curr(dev, attr, channel, val);
> +	case hwmon_temp:
> +		return ltc2991_read_temp(dev, attr, channel, val);
> +	default:
> +		return -EOPNOTSUPP;
> +	}
> +}
> +
> +static umode_t ltc2991_is_visible(const void *data, enum hwmon_sensor_types type, u32 attr,
> +				  int channel)
> +{
> +	const struct ltc2991_state *st = data;
> +
> +	switch (type) {
> +	case hwmon_in:
> +		switch (attr) {
> +		case hwmon_in_input:
> +		case hwmon_in_label:
> +			return 0444;
> +		}
> +		break;
> +	case hwmon_curr:
> +		switch (attr) {
> +		case hwmon_curr_input:
> +		case hwmon_curr_label:
> +			if (st->r_sense_mohm[channel])
> +				return 0444;
> +			break;
> +		}
> +		break;
> +	case hwmon_temp:
> +		switch (attr) {
> +		case hwmon_temp_input:
> +		case hwmon_temp_label:
> +			if (st->temp_en[channel] || channel == LTC2991_T_INT_CH_NR)
> +				return 0444;
> +			break;
> +		}
> +		break;
> +	default:
> +		break;
> +	}
> +
> +	return 0;
> +}
> +
> +static int ltc2991_read_string(struct device *dev, enum hwmon_sensor_types type, u32 attr,
> +			       int channel, const char **str)
> +{
> +	switch (type) {
> +	case hwmon_temp:
> +		*str = label_temp[channel];
> +		break;
> +	case hwmon_curr:
> +		*str = label_curr[channel];
> +		break;
> +	case hwmon_in:
> +		*str = label_voltages[channel];
> +		break;
> +	default:
> +		return -EOPNOTSUPP;
> +	}
> +
> +	return 0;
> +}
> +
> +static const struct hwmon_ops ltc2991_hwmon_ops = {
> +	.is_visible = ltc2991_is_visible,
> +	.read = ltc2991_read,
> +	.read_string = ltc2991_read_string,
> +};
> +
> +static const struct hwmon_channel_info *ltc2991_info[] = {
> +	HWMON_CHANNEL_INFO(temp,
> +			   HWMON_T_INPUT | HWMON_T_LABEL,
> +			   HWMON_T_INPUT | HWMON_T_LABEL,
> +			   HWMON_T_INPUT | HWMON_T_LABEL,
> +			   HWMON_T_INPUT | HWMON_T_LABEL,
> +			   HWMON_T_INPUT | HWMON_T_LABEL
> +			   ),
> +	HWMON_CHANNEL_INFO(curr,
> +			   HWMON_C_INPUT | HWMON_C_LABEL,
> +			   HWMON_C_INPUT | HWMON_C_LABEL,
> +			   HWMON_C_INPUT | HWMON_C_LABEL,
> +			   HWMON_C_INPUT | HWMON_C_LABEL
> +			   ),
> +	HWMON_CHANNEL_INFO(in,
> +			   HWMON_I_INPUT | HWMON_I_LABEL,
> +			   HWMON_I_INPUT | HWMON_I_LABEL,
> +			   HWMON_I_INPUT | HWMON_I_LABEL,
> +			   HWMON_I_INPUT | HWMON_I_LABEL,
> +			   HWMON_I_INPUT | HWMON_I_LABEL,
> +			   HWMON_I_INPUT | HWMON_I_LABEL,
> +			   HWMON_I_INPUT | HWMON_I_LABEL,
> +			   HWMON_I_INPUT | HWMON_I_LABEL,
> +			   HWMON_I_INPUT | HWMON_I_LABEL
> +			   ),
> +	NULL
> +};
> +
> +static const struct hwmon_chip_info ltc2991_chip_info = {
> +	.ops = &ltc2991_hwmon_ops,
> +	.info = ltc2991_info,
> +};
> +
> +static const struct regmap_config ltc2991_regmap_config = {
> +	.reg_bits = 8,
> +	.val_bits = 8,
> +	.max_register = 0x1D,
> +};
> +
> +static int ltc2991_init(struct ltc2991_state *st)
> +{
> +	struct fwnode_handle *fwnode;
> +	struct fwnode_handle *child;
> +	int ret;
> +	u32 val, addr;
> +	u8 v5_v8_reg_data = 0, v1_v4_reg_data = 0;
> +
> +	ret = devm_regulator_get_enable(&st->client->dev, "vcc");

The only use of st->client is in this function, which is called from probe.
Please just pass client as parameter (or even &client->dev since that is
what is really used).

> +	if (ret)
> +		return dev_err_probe(&st->client->dev, ret,
> +				     "failed to enable regulator\n");
> +
> +	fwnode = dev_fwnode(&st->client->dev);
> +
> +	fwnode_for_each_available_child_node(fwnode, child) {
> +		ret = fwnode_property_read_u32(child, "reg", &addr);
> +		if (ret < 0) {
> +			fwnode_handle_put(child);
> +			return ret;
> +		}
> +
> +		if (addr > 3) {
> +			fwnode_handle_put(child);
> +			return -EINVAL;
> +		}
> +
> +		ret = fwnode_property_read_u32(child, "shunt-resistor-mili-ohms", &val);
> +		if (!ret) {
> +			st->r_sense_mohm[addr] = val;

shunt resistors may be in fraction of milli-ohms.

> +			switch (addr) {
> +			case 0:
> +				v1_v4_reg_data |= LTC2991_V1_V2_DIFF_EN;
> +				break;
> +			case 1:
> +				v1_v4_reg_data |= LTC2991_V3_V4_DIFF_EN;
> +				break;
> +			case 2:
> +				v5_v8_reg_data |= LTC2991_V5_V6_DIFF_EN;
> +				break;
> +			case 3:
> +				v5_v8_reg_data |= LTC2991_V7_V8_DIFF_EN;
> +				break;
> +			default:
> +				break;
> +			}

While the above accepts sense resistor values of 0, it does not
distinguish that from "value not provided". At the very least that needs
an explanation.

> +		}
> +
> +		ret = fwnode_property_read_bool(child, "temperature-enable");
> +		if (ret) {
> +			st->temp_en[addr] = ret;
> +			switch (addr) {
> +			case 0:
> +				v1_v4_reg_data |= LTC2991_V1_V2_TEMP_EN;
> +				break;
> +			case 1:
> +				v1_v4_reg_data |= LTC2991_V3_V4_TEMP_EN;
> +				break;
> +			case 2:
> +				v5_v8_reg_data |= LTC2991_V5_V6_TEMP_EN;
> +				break;
> +			case 3:
> +				v5_v8_reg_data |= LTC2991_V7_V8_TEMP_EN;
> +				break;
> +			default:
> +				break;
> +			}
> +		}
> +	}

I am not happy that there are no defaults, meaning the chip can not be used
without devicetree or firmware (acpi) data. This is very undesirable and not
common for hwmon sensors. I would very much prefer the use of defaults
(i.e., existing register values and a default for the shunt resistor).

> +
> +	/* Setup V5-V8 Control register */
> +	ret = regmap_write(st->regmap, LTC2991_V5_V8_CTRL, v5_v8_reg_data);
> +	if (ret)
> +		return dev_err_probe(&st->client->dev, ret,
> +				     "Error: Failed to set V5-V8 CTRL reg.\n");
> +
> +	/* Setup V1-V4 Control register */
> +	ret = regmap_write(st->regmap, LTC2991_V1_V4_CTRL, v1_v4_reg_data);
> +	if (ret)
> +		return dev_err_probe(&st->client->dev, ret,
> +				     "Error: Failed to set V1-V4 CTRL reg.\n");
> +
> +	/* Setup continuous mode */
> +	ret = regmap_write(st->regmap, LTC2991_PWM_TH_LSB_T_INT,
> +			   LTC2991_REPEAT_ACQ_EN);
> +	if (ret)
> +		return dev_err_probe(&st->client->dev, ret,
> +				     "Error: Failed to set contiuous mode.\n");
> +
> +	/* Enable all channels and trigger conversions */
> +	ret = regmap_write(st->regmap, LTC2991_CH_EN_TRIGGER,
> +			   LTC2991_V7_V8_EN | LTC2991_V5_V6_EN |
> +			   LTC2991_V3_V4_EN | LTC2991_V1_V2_EN |
> +			   LTC2991_T_INT_VCC_EN);
> +	if (ret)
> +		return dev_err_probe(&st->client->dev, ret,
> +				     "Error: Failed to enable conversions.\n");
> +
> +	return 0;
> +}
> +
> +static int ltc2991_i2c_probe(struct i2c_client *client)
> +{
> +	int ret;
> +	struct device *hwmon_dev;
> +	struct ltc2991_state *st;
> +
> +	if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_WORD_DATA))
> +		return -EOPNOTSUPP;
> +
> +	st = devm_kzalloc(&client->dev, sizeof(*st), GFP_KERNEL);
> +	if (!st)
> +		return -ENOMEM;
> +
> +	st->client = client;
> +	st->regmap = devm_regmap_init_i2c(client, &ltc2991_regmap_config);
> +	if (IS_ERR(st->regmap))
> +		return PTR_ERR(st->regmap);
> +
> +	ret = ltc2991_init(st);
> +	if (ret)
> +		return ret;
> +
> +	hwmon_dev = devm_hwmon_device_register_with_info(&client->dev,
> +							 client->name, st,
> +							 &ltc2991_chip_info,
> +							 NULL);
> +
> +	return PTR_ERR_OR_ZERO(hwmon_dev);
> +}
> +
> +static const struct of_device_id ltc2991_of_match[] = {
> +	{ .compatible = "adi,ltc2991" },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(of, ltc2991_of_match);
> +
> +static const struct i2c_device_id ltc2991_i2c_id[] = {
> +	{ "ltc2991", 0 },
> +	{}
> +};
> +MODULE_DEVICE_TABLE(i2c, ltc2991_i2c_id);
> +
> +static struct i2c_driver ltc2991_i2c_driver = {
> +	.class = I2C_CLASS_HWMON,
> +	.driver = {
> +		.name = "ltc2991",
> +		.of_match_table = ltc2991_of_match,
> +	},
> +	.probe = ltc2991_i2c_probe,
> +	.id_table = ltc2991_i2c_id,
> +};
> +
> +module_i2c_driver(ltc2991_i2c_driver);
> +
> +MODULE_AUTHOR("Antoniu Miclaus <antoniu.miclaus@analog.com>");
> +MODULE_DESCRIPTION("Analog Devices LTC2991 HWMON Driver");
> +MODULE_LICENSE("GPL");
> -- 
> 2.42.0
>