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Sender: Guenter Roeck <groeck7@gmail.com>
Message-ID: <830ca43a-b64f-c8c0-7367-2e41133e75b9@roeck-us.net>
Date:   Fri, 28 Jul 2023 02:41:43 -0700
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Subject: Re: [PATCH v2 1/2] hwmon: (isl28022) new driver for ISL28022 power
 monitor
Content-Language: en-US
To:     =?UTF-8?Q?Carsten_Spie=c3=9f?= <mail@carsten-spiess.de>,
        Jean Delvare <jdelvare@suse.com>,
        Jonathan Corbet <corbet@lwn.net>,
        Geert Uytterhoeven <geert+renesas@glider.be>,
        Magnus Damm <magnus.damm@gmail.com>
Cc:     linux-hwmon@vger.kernel.org, linux-doc@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-renesas-soc@vger.kernel.org
References: <20230727195541.2245289-1-mail@carsten-spiess.de>
 <20230727195541.2245289-2-mail@carsten-spiess.de>
From:   Guenter Roeck <linux@roeck-us.net>
In-Reply-To: <20230727195541.2245289-2-mail@carsten-spiess.de>
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Precedence: bulk

On 7/27/23 12:55, Carsten Spieß wrote:
> Driver for Renesas ISL28022 power monitor with I2C interface.
> The device monitors voltage, current via shunt resistor
> and calculated power.
> 
> Signed-off-by: Carsten Spieß <mail@carsten-spiess.de>

Change log missing. I am not going to review patches without change log.

Guenter

> ---
>   Documentation/hwmon/index.rst    |   1 +
>   Documentation/hwmon/isl28022.rst |  63 ++++
>   MAINTAINERS                      |   7 +
>   drivers/hwmon/Kconfig            |  11 +
>   drivers/hwmon/Makefile           |   1 +
>   drivers/hwmon/isl28022.c         | 496 +++++++++++++++++++++++++++++++
>   6 files changed, 579 insertions(+)
>   create mode 100644 Documentation/hwmon/isl28022.rst
>   create mode 100644 drivers/hwmon/isl28022.c
> 
> diff --git a/Documentation/hwmon/index.rst b/Documentation/hwmon/index.rst
> index d11924667f76..c9548fc5c40e 100644
> --- a/Documentation/hwmon/index.rst
> +++ b/Documentation/hwmon/index.rst
> @@ -90,6 +90,7 @@ Hardware Monitoring Kernel Drivers
>      ir35221
>      ir38064
>      ir36021
> +   isl28022
>      isl68137
>      it87
>      jc42
> diff --git a/Documentation/hwmon/isl28022.rst b/Documentation/hwmon/isl28022.rst
> new file mode 100644
> index 000000000000..8d4422a2dacd
> --- /dev/null
> +++ b/Documentation/hwmon/isl28022.rst
> @@ -0,0 +1,63 @@
> +.. SPDX-License-Identifier: GPL-2.0-or-later
> +
> +Kernel driver isl28022
> +======================
> +
> +Supported chips:
> +
> +  * Renesas ISL28022
> +
> +    Prefix: 'isl28022'
> +
> +    Addresses scanned: none
> +
> +    Datasheet: Publicly available at the Renesas website
> +
> +	       https://www.renesas.com/us/en/www/doc/datasheet/isl28022.pdf
> +
> +Author:
> +    Carsten Spieß <mail@carsten-spiess.de>
> +
> +Description
> +-----------
> +
> +The ISL28022 is a power monitor with I2C interface. The device monitors
> +voltage, current via shunt resistor and calculated power.
> +
> +Usage Notes
> +-----------
> +
> +This driver does not auto-detect devices. You will have to instantiate the
> +device explicitly. Please see Documentation/i2c/instantiating-devices.rst for
> +details.
> +
> +The shunt value in micro-ohms, shunt voltage range and averaging can be set
> +with device properties.
> +Please refer to the Documentation/devicetree/bindings/hwmon/isl,isl28022.yaml
> +for bindings if the device tree is used.
> +
> +The driver supports only shunt and bus continuous ADC mode at 15bit resolution.
> +Averaging can be set from 1 to 128 samples (power of 2) on both channels.
> +Shunt voltage range of 40, 80, 160 or 320mV is allowed
> +The bus voltage range is 60V fixed.
> +
> +Sysfs entries
> +-------------
> +
> +The following attributes are supported. All attributes are read-only.
> +
> +======================= =======================================================
> +in0_input		bus voltage (milli Volt)
> +
> +curr1_input		current (milli Ampere)
> +power1_input		power (micro Watt)
> +======================= =======================================================
> +
> +Debugfs entries
> +---------------
> +
> +The following attributes are supported. All attributes are read-only.
> +
> +======================= =======================================================
> +shunt_voltage		shunt voltage (micro Volt)
> +======================= =======================================================
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 7abb5710e1bb..b02e3b991676 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -11065,6 +11065,13 @@ F:	drivers/isdn/Makefile
>   F:	drivers/isdn/hardware/
>   F:	drivers/isdn/mISDN/
>   
> +ISL28022 HARDWARE MONITORING DRIVER
> +M:	Carsten Spieß <mail@carsten-spiess.de>
> +L:	linux-hwmon@vger.kernel.org
> +S:	Maintained
> +F:	Documentation/hwmon/isl28022.rst
> +F:	drivers/hwmon/isl28022.c
> +
>   ISOFS FILESYSTEM
>   M:	Jan Kara <jack@suse.cz>
>   L:	linux-fsdevel@vger.kernel.org
> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> index 2913299c2c9e..3049c519e6ac 100644
> --- a/drivers/hwmon/Kconfig
> +++ b/drivers/hwmon/Kconfig
> @@ -800,6 +800,17 @@ config SENSORS_CORETEMP
>   	  sensor inside your CPU. Most of the family 6 CPUs
>   	  are supported. Check Documentation/hwmon/coretemp.rst for details.
>   
> +config SENSORS_ISL28022
> +	tristate "Renesas ISL28022"
> +	depends on I2C
> +	select REGMAP_I2C
> +	help
> +	  If you say yes here you get support for ISL28022 power monitor.
> +	  Check Documentation/hwmon/isl28022.rst for details.
> +
> +	  This driver can also be built as a module. If so, the module
> +	  will be called isl28022.
> +
>   config SENSORS_IT87
>   	tristate "ITE IT87xx and compatibles"
>   	depends on !PPC
> diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
> index ff6bfd109c72..4046fed7f48d 100644
> --- a/drivers/hwmon/Makefile
> +++ b/drivers/hwmon/Makefile
> @@ -98,6 +98,7 @@ obj-$(CONFIG_SENSORS_INA2XX)	+= ina2xx.o
>   obj-$(CONFIG_SENSORS_INA238)	+= ina238.o
>   obj-$(CONFIG_SENSORS_INA3221)	+= ina3221.o
>   obj-$(CONFIG_SENSORS_INTEL_M10_BMC_HWMON) += intel-m10-bmc-hwmon.o
> +obj-$(CONFIG_SENSORS_ISL28022)	+= isl28022.o
>   obj-$(CONFIG_SENSORS_IT87)	+= it87.o
>   obj-$(CONFIG_SENSORS_JC42)	+= jc42.o
>   obj-$(CONFIG_SENSORS_K8TEMP)	+= k8temp.o
> diff --git a/drivers/hwmon/isl28022.c b/drivers/hwmon/isl28022.c
> new file mode 100644
> index 000000000000..18b4481d5ff6
> --- /dev/null
> +++ b/drivers/hwmon/isl28022.c
> @@ -0,0 +1,496 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * isl28022.c - driver for Renesas ISL28022 power monitor chip monitoring
> + *
> + * Copyright (c) 2023 Carsten Spieß <mail@carsten-spiess.de>
> + */
> +
> +#include <linux/module.h>
> +#include <linux/init.h>
> +#include <linux/slab.h>
> +#include <linux/i2c.h>
> +#include <linux/hwmon.h>
> +#include <linux/hwmon-sysfs.h>
> +#include <linux/debugfs.h>
> +#include <linux/err.h>
> +#include <linux/of_device.h>
> +#include <linux/regmap.h>
> +#include <linux/util_macros.h>
> +#include <linux/regulator/consumer.h>
> +
> +/* ISL28022 registers */
> +#define ISL28022_REG_CONFIG	0x00
> +#define ISL28022_REG_SHUNT	0x01
> +#define ISL28022_REG_BUS	0x02
> +#define ISL28022_REG_POWER	0x03
> +#define ISL28022_REG_CURRENT	0x04
> +#define ISL28022_REG_CALIB	0x05
> +#define ISL28022_REG_SHUNT_THR	0x06
> +#define ISL28022_REG_BUS_THR	0x07
> +#define ISL28022_REG_INT	0x08
> +#define ISL28022_REG_AUX	0x09
> +#define ISL28022_REG_MAX	ISL28022_REG_AUX
> +
> +/* ISL28022 config flags */
> +/* mode flags */
> +#define ISL28022_MODE_SHIFT	0
> +#define ISL28022_MODE_MASK	0x0007
> +
> +#define ISL28022_MODE_PWR_DOWN	0x0
> +#define ISL28022_MODE_TRG_S	0x1
> +#define ISL28022_MODE_TRG_B	0x2
> +#define ISL28022_MODE_TRG_SB	0x3
> +#define ISL28022_MODE_ADC_OFF	0x4
> +#define ISL28022_MODE_CONT_S	0x5
> +#define ISL28022_MODE_CONT_B	0x6
> +#define ISL28022_MODE_CONT_SB	0x7
> +
> +/* shunt ADC settings */
> +#define ISL28022_SADC_SHIFT	3
> +#define ISL28022_SADC_MASK	0x0078
> +
> +#define ISL28022_BADC_SHIFT	7
> +#define ISL28022_BADC_MASK	0x0780
> +
> +#define ISL28022_ADC_12		0x0	/* 12 bit ADC */
> +#define ISL28022_ADC_13		0x1	/* 13 bit ADC */
> +#define ISL28022_ADC_14		0x2	/* 14 bit ADC */
> +#define ISL28022_ADC_15		0x3	/* 15 bit ADC */
> +#define ISL28022_ADC_15_1	0x8	/* 15 bit ADC, 1 sample */
> +#define ISL28022_ADC_15_2	0x9	/* 15 bit ADC, 2 samples */
> +#define ISL28022_ADC_15_4	0xA	/* 15 bit ADC, 4 samples */
> +#define ISL28022_ADC_15_8	0xB	/* 15 bit ADC, 8 samples */
> +#define ISL28022_ADC_15_16	0xC	/* 15 bit ADC, 16 samples */
> +#define ISL28022_ADC_15_32	0xD	/* 15 bit ADC, 32 samples */
> +#define ISL28022_ADC_15_64	0xE	/* 15 bit ADC, 64 samples */
> +#define ISL28022_ADC_15_128	0xF	/* 15 bit ADC, 128 samples */
> +
> +/* shunt voltage range */
> +#define ISL28022_PG_SHIFT	11
> +#define ISL28022_PG_MASK	0x1800
> +
> +#define ISL28022_PG_40		0x0	/* +/-40 mV */
> +#define ISL28022_PG_80		0x1	/* +/-80 mV */
> +#define ISL28022_PG_160		0x2	/* +/-160 mV */
> +#define ISL28022_PG_320		0x3	/* +/-3200 mV */
> +
> +/* bus voltage range */
> +#define ISL28022_BRNG_SHIFT	13
> +#define ISL28022_BRNG_MASK	0x6000
> +
> +#define ISL28022_BRNG_16	0x0	/* 16 V */
> +#define ISL28022_BRNG_32	0x1	/* 32 V */
> +#define ISL28022_BRNG_60	0x3	/* 60 V */
> +
> +/* reset */
> +#define ISL28022_RESET		0x8000
> +
> +struct isl28022_data {
> +	struct i2c_client	*client;
> +	struct regmap		*regmap;
> +#ifdef CONFIG_DEBUG_FS
> +	struct dentry		*debugfs;
> +#endif
> +	u32			shunt;
> +	u32			gain;
> +	u32			average;
> +	u16			config;
> +	u16			calib;
> +};
> +
> +static int isl28022_read(struct device *dev, enum hwmon_sensor_types type,
> +			 u32 attr, int channel, long *val)
> +{
> +	struct isl28022_data *data = dev_get_drvdata(dev);
> +	unsigned int regval;
> +	int err;
> +
> +	switch (type) {
> +	case hwmon_in:
> +		switch (attr) {
> +		case hwmon_in_input:
> +			err = regmap_read(data->regmap,
> +					  ISL28022_REG_BUS, &regval);
> +			if (err < 0)
> +				return err;
> +			/* driver supports only 60V mode (BRNG 11) */
> +			*val = (long)(((u16)regval) & 0xFFFC);
> +			break;
> +		default:
> +			return -EINVAL;
> +		}
> +		break;
> +	case hwmon_curr:
> +		switch (attr) {
> +		case hwmon_curr_input:
> +			err = regmap_read(data->regmap,
> +					  ISL28022_REG_CURRENT, &regval);
> +			if (err < 0)
> +				return err;
> +			*val = ((long)regval * 1250L * (long)data->gain) /
> +				(long)data->shunt;
> +			break;
> +		default:
> +			return -EINVAL;
> +		}
> +		break;
> +	case hwmon_power:
> +		switch (attr) {
> +		case hwmon_power_input:
> +			err = regmap_read(data->regmap,
> +					  ISL28022_REG_POWER, &regval);
> +			if (err < 0)
> +				return err;
> +			*val = ((51200000L * ((long)data->gain)) /
> +				(long)data->shunt) * (long)regval;
> +			break;
> +		default:
> +			return -EINVAL;
> +		}
> +		break;
> +	default:
> +		return -EINVAL;
> +	}
> +
> +	return 0;
> +}
> +
> +static umode_t isl28022_is_visible(const void *data, enum hwmon_sensor_types type,
> +				   u32 attr, int channel)
> +{
> +	switch (type) {
> +	case hwmon_in:
> +		switch (attr) {
> +		case hwmon_in_input:
> +			return 0444;
> +		}
> +		break;
> +	case hwmon_curr:
> +		switch (attr) {
> +		case hwmon_curr_input:
> +			return 0444;
> +		}
> +		break;
> +	case hwmon_power:
> +		switch (attr) {
> +		case hwmon_power_input:
> +			return 0444;
> +		}
> +		break;
> +	default:
> +		break;
> +	}
> +	return 0;
> +}
> +
> +static const struct hwmon_channel_info *isl28022_info[] = {
> +	HWMON_CHANNEL_INFO(in,
> +			   HWMON_I_INPUT),	/* channel 0: bus voltage (mV) */
> +	HWMON_CHANNEL_INFO(curr,
> +			   HWMON_C_INPUT),	/* channel 1: current (mA) */
> +	HWMON_CHANNEL_INFO(power,
> +			   HWMON_P_INPUT),	/* channel 1: power (µW) */
> +	NULL
> +};
> +
> +static const struct hwmon_ops isl28022_hwmon_ops = {
> +	.is_visible = isl28022_is_visible,
> +	.read = isl28022_read,
> +};
> +
> +static const struct hwmon_chip_info isl28022_chip_info = {
> +	.ops = &isl28022_hwmon_ops,
> +	.info = isl28022_info,
> +};
> +
> +static bool isl28022_is_writeable_reg(struct device *dev, unsigned int reg)
> +{
> +	switch (reg) {
> +	case ISL28022_REG_CONFIG:
> +	case ISL28022_REG_CALIB:
> +	case ISL28022_REG_SHUNT_THR:
> +	case ISL28022_REG_BUS_THR:
> +	case ISL28022_REG_INT:
> +	case ISL28022_REG_AUX:
> +		return true;
> +	}
> +
> +	return false;
> +}
> +
> +static bool isl28022_is_volatile_reg(struct device *dev, unsigned int reg)
> +{
> +	switch (reg) {
> +	case ISL28022_REG_CONFIG:
> +	case ISL28022_REG_SHUNT:
> +	case ISL28022_REG_BUS:
> +	case ISL28022_REG_POWER:
> +	case ISL28022_REG_CURRENT:
> +	case ISL28022_REG_INT:
> +	case ISL28022_REG_AUX:
> +		return true;
> +	}
> +	return true;
> +}
> +
> +static const struct regmap_config isl28022_regmap_config = {
> +	.reg_bits = 8,
> +	.val_bits = 16,
> +	.max_register = ISL28022_REG_MAX,
> +	.writeable_reg = isl28022_is_writeable_reg,
> +	.volatile_reg = isl28022_is_volatile_reg,
> +	.val_format_endian = REGMAP_ENDIAN_BIG,
> +	.cache_type = REGCACHE_RBTREE,
> +	.use_single_read = true,
> +	.use_single_write = true,
> +};
> +
> +static const struct i2c_device_id isl28022_ids[] = {
> +	{ "isl28022", 0},
> +	{ /* LIST END */ }
> +};
> +MODULE_DEVICE_TABLE(i2c, isl28022_ids);
> +
> +#ifdef CONFIG_DEBUG_FS
> +static int shunt_voltage_show(struct seq_file *seqf, void *unused)
> +{
> +	struct isl28022_data *data = seqf->private;
> +	unsigned int regval;
> +	int err;
> +
> +	err = regmap_read(data->regmap,
> +			  ISL28022_REG_SHUNT, &regval);
> +	if (err)
> +		return err;
> +
> +	/* print shunt voltage in micro volt  */
> +	seq_printf(seqf, "%d\n", regval * 10);
> +
> +	return 0;
> +}
> +DEFINE_SHOW_ATTRIBUTE(shunt_voltage);
> +
> +static struct dentry *isl28022_debugfs_root;
> +
> +static void isl28022_debugfs_remove(void *res)
> +{
> +	debugfs_remove_recursive(res);
> +}
> +
> +static int isl28022_debugfs_init(struct isl28022_data *data)
> +{
> +	char name[16];
> +	int err;
> +	struct dentry *entry;
> +
> +	scnprintf(name, sizeof(name), "%d-%04hx", data->client->adapter->nr, data->client->addr);
> +
> +	data->debugfs = debugfs_create_dir(name, isl28022_debugfs_root);
> +	if (IS_ERR(data->debugfs))
> +		return PTR_ERR(data->debugfs);
> +
> +	err = devm_add_action_or_reset(&data->client->dev, isl28022_debugfs_remove, data->debugfs);
> +	if (err)
> +		return err;
> +
> +	entry = debugfs_create_file("shunt_voltage", 0444, data->debugfs, data,
> +			    &shunt_voltage_fops);
> +	if (IS_ERR(entry))
> +		return PTR_ERR(entry);
> +
> +	return 0;
> +}
> +#endif /* CONFIG_DEBUG_FS*/
> +
> +/*
> + * read property values and make consistency checks.
> + *
> + * following values for shunt range and resistor are allowed:
> + *   40 mV -> gain 1, shunt min.  800 micro ohms
> + *   80 mV -> gain 2, shunt min. 1600 micro ohms
> + *  160 mV -> gain 4, shunt min. 3200 micro ohms
> + *  320 mV -> gain 8, shunt min. 6400 micro ohms
> + */
> +static int isl28022_read_properties(struct device *dev, struct isl28022_data *data)
> +{
> +	u32 val;
> +	int err;
> +
> +	err = device_property_read_u32(dev, "shunt-resistor-micro-ohms", &val);
> +	if (err == -ENODATA)
> +		val = 10000;
> +	else if (err < 0)
> +		return err;
> +	data->shunt = val;
> +
> +	err = device_property_read_u32(dev, "renesas,shunt-range-microvolt", &val);
> +	if (err == -ENODATA)
> +		val = 320000;
> +	else if (err < 0)
> +		return err;
> +	switch (val) {
> +	case 40000:
> +		data->gain = 1;
> +		if (data->shunt < 800)
> +			goto shunt_invalid;
> +		break;
> +	case 80000:
> +		data->gain = 2;
> +		if (data->shunt < 1600)
> +			goto shunt_invalid;
> +		break;
> +	case 160000:
> +		data->gain = 4;
> +		if (data->shunt < 3200)
> +			goto shunt_invalid;
> +		break;
> +	case 320000:
> +		data->gain = 8;
> +		if (data->shunt < 6400)
> +			goto shunt_invalid;
> +		break;
> +	default:
> +		dev_err(dev, "renesas,shunt-range-microvolt invalid value %d\n", val);
> +		return -EINVAL;
> +	}
> +
> +	err = device_property_read_u32(dev, "renesas,average-samples", &val);
> +	if (err == -ENODATA)
> +		val = 1;
> +	else if (err < 0)
> +		return err;
> +	if ((val > 128) || (BIT(__ffs(val)) != val)) {
> +		dev_err(dev, "renesas,average-samples invalid value %d\n", val);
> +		return -EINVAL;
> +	}
> +	data->average = val;
> +
> +	return 0;
> +
> +shunt_invalid:
> +	dev_err(dev, "renesas,shunt-resistor-microvolt invalid value %d\n", data->shunt);
> +	return -EINVAL;
> +}
> +
> +/*
> + * write configuration and calibration registers
> + *
> + * The driver supports only shunt and bus continuous ADC mode at 15bit resolution
> + * with averaging from 1 to 128 samples (pow of 2) on both channels.
> + * Shunt voltage gain 1,2,4 or 8 is allowed.
> + * The bus voltage range is 60V fixed.
> + */
> +static int isl28022_config(struct isl28022_data *data)
> +{
> +	int err;
> +
> +	data->config = (ISL28022_MODE_CONT_SB << ISL28022_MODE_SHIFT) |
> +			(ISL28022_BRNG_60 << ISL28022_BRNG_SHIFT) |
> +			(__ffs(data->gain) << ISL28022_PG_SHIFT) |
> +			((ISL28022_ADC_15_1 + __ffs(data->average)) << ISL28022_SADC_SHIFT) |
> +			((ISL28022_ADC_15_1 + __ffs(data->average)) << ISL28022_BADC_SHIFT);
> +
> +	data->calib = data->shunt ? 0x8000 / data->gain : 0;
> +
> +	err = regmap_write(data->regmap, ISL28022_REG_CONFIG, data->config);
> +	if (err < 0)
> +		return err;
> +
> +	err = regmap_write(data->regmap, ISL28022_REG_CALIB, data->calib);
> +	if (err < 0)
> +		return err;
> +
> +	return 0;
> +}
> +
> +static int isl28022_probe(struct i2c_client *client)
> +{
> +	struct device *dev = &client->dev;
> +	struct device *hwmon_dev;
> +	struct isl28022_data *data;
> +	int err;
> +
> +	if (!i2c_check_functionality(client->adapter,
> +				     I2C_FUNC_SMBUS_BYTE_DATA |
> +				     I2C_FUNC_SMBUS_WORD_DATA))
> +		return -ENODEV;
> +
> +	data = devm_kzalloc(dev, sizeof(struct isl28022_data), GFP_KERNEL);
> +	if (!data)
> +		return -ENOMEM;
> +
> +	data->client = client;
> +
> +	err = isl28022_read_properties(dev, data);
> +	if (err)
> +		return err;
> +
> +	data->regmap = devm_regmap_init_i2c(client, &isl28022_regmap_config);
> +	if (IS_ERR(data->regmap))
> +		return PTR_ERR(data->regmap);
> +
> +	err = isl28022_config(data);
> +	if (err)
> +		return err;
> +
> +#ifdef CONFIG_DEBUG_FS
> +	err = isl28022_debugfs_init(data);
> +	if (err)
> +		return err;
> +#endif
> +
> +	hwmon_dev = devm_hwmon_device_register_with_info(dev, "isl28022_hwmon",
> +							 data, &isl28022_chip_info, NULL);
> +	if (IS_ERR(hwmon_dev))
> +		return PTR_ERR(hwmon_dev);
> +
> +	dev_info(dev, "%s: sensor '%s'\n", dev_name(hwmon_dev), client->name);
> +	return 0;
> +}
> +
> +static const struct of_device_id __maybe_unused isl28022_of_match[] = {
> +	{ .compatible = "renesas,isl28022"},
> +	{ /* LIST END */ }
> +};
> +MODULE_DEVICE_TABLE(of, isl28022_of_match);
> +
> +static struct i2c_driver isl28022_driver = {
> +	.class		= I2C_CLASS_HWMON,
> +	.driver = {
> +		.name	= "isl28022",
> +	},
> +	.probe_new	= isl28022_probe,
> +	.id_table	= isl28022_ids,
> +};
> +
> +#ifdef CONFIG_DEBUG_FS
> +static int __init
> +isl28022_init(void)
> +{
> +	int err;
> +
> +	isl28022_debugfs_root = debugfs_create_dir("isl28022", NULL);
> +	err = i2c_add_driver(&isl28022_driver);
> +	if (!err)
> +		return 0;
> +
> +	debugfs_remove_recursive(isl28022_debugfs_root);
> +	return err;
> +}
> +
> +static void __exit
> +isl28022_exit(void)
> +{
> +	i2c_del_driver(&isl28022_driver);
> +	debugfs_remove_recursive(isl28022_debugfs_root);
> +}
> +
> +module_init(isl28022_init);
> +module_exit(isl28022_exit);
> +#else /* CONFIG_DEBUG_FS */
> +module_i2c_driver(isl28022_driver);
> +#endif /* CONFIG_DEBUG_FS */
> +
> +MODULE_AUTHOR("Carsten Spieß <mail@carsten-spiess.de>");
> +MODULE_DESCRIPTION("ISL28022 driver");
> +MODULE_LICENSE("GPL");