drivers/iio/amplifiers/hmc425a.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /*
  * HMC425A and similar Gain Amplifiers
  *
  * Copyright 2020, 2024 Analog Devices Inc.
  */

 #include <linux/bits.h>
 #include <linux/bitops.h>
 #include <linux/device.h>
 #include <linux/err.h>
 #include <linux/gpio/consumer.h>
 #include <linux/iio/iio.h>
 #include <linux/iio/sysfs.h>
 #include <linux/kernel.h>
 #include <linux/math.h>
 #include <linux/mod_devicetable.h>
 #include <linux/module.h>
 #include <linux/platform_device.h>
 #include <linux/property.h>
 #include <linux/slab.h>
 #include <linux/regulator/consumer.h>
 #include <linux/sysfs.h>

 /*
  * The LTC6373 amplifier supports configuring gain using GPIO's with the following
  *  values (OUTPUT_V / INPUT_V): 0(shutdown), 0.25, 0.5, 1, 2, 4, 8, 16
  *
  * Except for the shutdown value, all can be converted to dB using 20 * log10(x)
  * From here, it is observed that all values are multiples of the '2' gain setting,
  *  with the correspondent of 6.020dB.
  */
 #define LTC6373_CONVERSION_CONSTANT	6020
 #define LTC6373_MIN_GAIN_CODE		0x6
 #define LTC6373_CONVERSION_MASK		GENMASK(2, 0)
 #define LTC6373_SHUTDOWN		GENMASK(2, 0)

 enum hmc425a_type {
 	ID_HMC425A,
 	ID_HMC540S,
 	ID_ADRF5740,
 	ID_LTC6373,
 };

 struct hmc425a_chip_info {
 	const char			*name;
 	const struct iio_chan_spec	*channels;
 	unsigned int			num_channels;
 	unsigned int			num_gpios;
 	int				gain_min;
 	int				gain_max;
 	int				default_gain;
 	int				powerdown_val;
 	bool				has_powerdown;

 	int				(*gain_dB_to_code)(int gain, int *code);
 	int				(*code_to_gain_dB)(int code, int *val, int *val2);
 };

 struct hmc425a_state {
 	struct	mutex lock; /* protect sensor state */
 	const struct	hmc425a_chip_info *chip_info;
 	struct	gpio_descs *gpios;
 	u32	gain;
 	bool	powerdown;
 };

 static int gain_dB_to_code(struct hmc425a_state *st, int val, int val2, int *code)
 {
 	const struct hmc425a_chip_info *inf = st->chip_info;
 	int gain;

 	if (val < 0)
 		gain = (val * 1000) - (val2 / 1000);
 	else
 		gain = (val * 1000) + (val2 / 1000);

 	if (gain > inf->gain_max || gain < inf->gain_min)
 		return -EINVAL;
 	if (st->powerdown)
 		return -EPERM;

 	return st->chip_info->gain_dB_to_code(gain, code);
 }

 static int hmc425a_gain_dB_to_code(int gain, int *code)
 {
 	*code = ~((abs(gain) / 500) & 0x3F);
 	return 0;
 }

 static int hmc540s_gain_dB_to_code(int gain, int *code)
 {
 	*code = ~((abs(gain) / 1000) & 0xF);
 	return 0;
 }

 static int adrf5740_gain_dB_to_code(int gain, int *code)
 {
 	int temp = (abs(gain) / 2000) & 0xF;

 	/* Bit [0-3]: 2dB 4dB 8dB 8dB */
 	*code = temp & BIT(3) ? temp | BIT(2) : temp;
 	return 0;
 }

 static int ltc6373_gain_dB_to_code(int gain, int *code)
 {
 	*code = ~(DIV_ROUND_CLOSEST(gain, LTC6373_CONVERSION_CONSTANT) + 3)
 		& LTC6373_CONVERSION_MASK;
 	return 0;
 }

 static int code_to_gain_dB(struct hmc425a_state *st, int *val, int *val2)
 {
 	if (st->powerdown)
 		return -EPERM;
 	return st->chip_info->code_to_gain_dB(st->gain, val, val2);
 }

 static int hmc425a_code_to_gain_dB(int code, int *val, int *val2)
 {
 	*val = (~code * -500) / 1000;
 	*val2 = ((~code * -500) % 1000) * 1000;
 	return 0;
 }

 static int hmc540s_code_to_gain_dB(int code, int *val, int *val2)
 {
 	*val = (~code * -1000) / 1000;
 	*val2 = ((~code * -1000) % 1000) * 1000;
 	return 0;
 }

 static int adrf5740_code_to_gain_dB(int code, int *val, int *val2)
 {
 	/*
 	 * Bit [0-3]: 2dB 4dB 8dB 8dB
 	 * When BIT(3) is set, unset BIT(2) and use 3 as double the place value
 	 */
 	code = code & BIT(3) ? code & ~BIT(2) : code;
 	*val = (code * -2000) / 1000;
 	*val2 = ((code * -2000) % 1000) * 1000;
 	return 0;
 }

 static int ltc6373_code_to_gain_dB(int code, int *val, int *val2)
 {
 	int gain = ((~code & LTC6373_CONVERSION_MASK) - 3) *
 		   LTC6373_CONVERSION_CONSTANT;

 	*val = gain / 1000;
 	*val2 = (gain % 1000) * 1000;
 	return 0;
 }

 static int hmc425a_write(struct iio_dev *indio_dev, u32 value)
 {
 	struct hmc425a_state *st = iio_priv(indio_dev);
 	DECLARE_BITMAP(values, BITS_PER_TYPE(value));

 	values[0] = value;

 	gpiod_set_array_value_cansleep(st->gpios->ndescs, st->gpios->desc,
 				       NULL, values);
 	return 0;
 }

 static int hmc425a_read_raw(struct iio_dev *indio_dev,
 			    struct iio_chan_spec const *chan, int *val,
 			    int *val2, long m)
 {
 	struct hmc425a_state *st = iio_priv(indio_dev);
 	int ret;

 	mutex_lock(&st->lock);
 	switch (m) {
 	case IIO_CHAN_INFO_HARDWAREGAIN:
 		ret = code_to_gain_dB(st, val, val2);
 		if (ret)
 			break;
 		ret = IIO_VAL_INT_PLUS_MICRO_DB;
 		break;
 	default:
 		ret = -EINVAL;
 	}
 	mutex_unlock(&st->lock);

 	return ret;
 };

 static int hmc425a_write_raw(struct iio_dev *indio_dev,
 			     struct iio_chan_spec const *chan, int val,
 			     int val2, long mask)
 {
 	struct hmc425a_state *st = iio_priv(indio_dev);
 	int code = 0, ret;

 	mutex_lock(&st->lock);
 	switch (mask) {
 	case IIO_CHAN_INFO_HARDWAREGAIN:
 		ret = gain_dB_to_code(st, val, val2, &code);
 		if (ret)
 			break;
 		st->gain = code;

 		ret = hmc425a_write(indio_dev, st->gain);
 		break;
 	default:
 		ret = -EINVAL;
 	}
 	mutex_unlock(&st->lock);

 	return ret;
 }

 static int hmc425a_write_raw_get_fmt(struct iio_dev *indio_dev,
 				     struct iio_chan_spec const *chan,
 				     long mask)
 {
 	switch (mask) {
 	case IIO_CHAN_INFO_HARDWAREGAIN:
 		return IIO_VAL_INT_PLUS_MICRO_DB;
 	default:
 		return -EINVAL;
 	}
 }

 static const struct iio_info hmc425a_info = {
 	.read_raw = &hmc425a_read_raw,
 	.write_raw = &hmc425a_write_raw,
 	.write_raw_get_fmt = &hmc425a_write_raw_get_fmt,
 };

 static ssize_t ltc6373_read_powerdown(struct iio_dev *indio_dev,
 				      uintptr_t private,
 				      const struct iio_chan_spec *chan,
 				      char *buf)
 {
 	struct hmc425a_state *st = iio_priv(indio_dev);

 	return sysfs_emit(buf, "%d\n", st->powerdown);
 }

 static ssize_t ltc6373_write_powerdown(struct iio_dev *indio_dev,
 				       uintptr_t private,
 				       const struct iio_chan_spec *chan,
 				       const char *buf,
 				       size_t len)
 {
 	struct hmc425a_state *st = iio_priv(indio_dev);
 	bool powerdown;
 	int code, ret;

 	ret = kstrtobool(buf, &powerdown);
 	if (ret)
 		return ret;

 	mutex_lock(&st->lock);
 	st->powerdown = powerdown;
 	code = (powerdown) ? LTC6373_SHUTDOWN : st->gain;
 	hmc425a_write(indio_dev, code);
 	mutex_unlock(&st->lock);
 	return len;
 }

 static const struct iio_chan_spec_ext_info ltc6373_ext_info[] = {
 	{
 		.name = "powerdown",
 		.read = ltc6373_read_powerdown,
 		.write = ltc6373_write_powerdown,
 		.shared = IIO_SEPARATE,
 	},
 	{}
 };

 #define HMC425A_CHAN(_channel)						\
 {									\
 	.type = IIO_VOLTAGE,						\
 	.output = 1,							\
 	.indexed = 1,							\
 	.channel = _channel,						\
 	.info_mask_separate = BIT(IIO_CHAN_INFO_HARDWAREGAIN),		\
 }

 #define LTC6373_CHAN(_channel)						\
 {									\
 	.type = IIO_VOLTAGE,						\
 	.output = 1,							\
 	.indexed = 1,							\
 	.channel = _channel,						\
 	.info_mask_separate = BIT(IIO_CHAN_INFO_HARDWAREGAIN),		\
 	.ext_info = ltc6373_ext_info,					\
 }

 static const struct iio_chan_spec hmc425a_channels[] = {
 	HMC425A_CHAN(0),
 };

 static const struct iio_chan_spec ltc6373_channels[] = {
 	LTC6373_CHAN(0),
 };

 static const struct hmc425a_chip_info hmc425a_chip_info_tbl[] = {
 	[ID_HMC425A] = {
 		.name = "hmc425a",
 		.channels = hmc425a_channels,
 		.num_channels = ARRAY_SIZE(hmc425a_channels),
 		.num_gpios = 6,
 		.gain_min = -31500,
 		.gain_max = 0,
 		.default_gain = -0x40, /* set default gain -31.5db*/
 		.gain_dB_to_code = hmc425a_gain_dB_to_code,
 		.code_to_gain_dB = hmc425a_code_to_gain_dB,
 	},
 	[ID_HMC540S] = {
 		.name = "hmc540s",
 		.channels = hmc425a_channels,
 		.num_channels = ARRAY_SIZE(hmc425a_channels),
 		.num_gpios = 4,
 		.gain_min = -15000,
 		.gain_max = 0,
 		.default_gain = -0x10, /* set default gain -15.0db*/
 		.gain_dB_to_code = hmc540s_gain_dB_to_code,
 		.code_to_gain_dB = hmc540s_code_to_gain_dB,
 	},
 	[ID_ADRF5740] = {
 		.name = "adrf5740",
 		.channels = hmc425a_channels,
 		.num_channels = ARRAY_SIZE(hmc425a_channels),
 		.num_gpios = 4,
 		.gain_min = -22000,
 		.gain_max = 0,
 		.default_gain = 0xF, /* set default gain -22.0db*/
 		.gain_dB_to_code = adrf5740_gain_dB_to_code,
 		.code_to_gain_dB = adrf5740_code_to_gain_dB,
 	},
 	[ID_LTC6373] = {
 		.name = "ltc6373",
 		.channels = ltc6373_channels,
 		.num_channels = ARRAY_SIZE(ltc6373_channels),
 		.num_gpios = 3,
 		.gain_min = -12041, /* gain setting x0.25*/
 		.gain_max = 24082,  /* gain setting x16  */
 		.default_gain = LTC6373_MIN_GAIN_CODE,
 		.powerdown_val = LTC6373_SHUTDOWN,
 		.has_powerdown = true,
 		.gain_dB_to_code = ltc6373_gain_dB_to_code,
 		.code_to_gain_dB = ltc6373_code_to_gain_dB,
 	},
 };

 static int hmc425a_probe(struct platform_device *pdev)
 {
 	struct iio_dev *indio_dev;
 	struct hmc425a_state *st;
 	int ret;

 	indio_dev = devm_iio_device_alloc(&pdev->dev, sizeof(*st));
 	if (!indio_dev)
 		return -ENOMEM;

 	st = iio_priv(indio_dev);

 	st->chip_info = device_get_match_data(&pdev->dev);
 	indio_dev->num_channels = st->chip_info->num_channels;
 	indio_dev->channels = st->chip_info->channels;
 	indio_dev->name = st->chip_info->name;
 	st->gain = st->chip_info->default_gain;

 	st->gpios = devm_gpiod_get_array(&pdev->dev, "ctrl", GPIOD_OUT_LOW);
 	if (IS_ERR(st->gpios))
 		return dev_err_probe(&pdev->dev, PTR_ERR(st->gpios),
 				     "failed to get gpios\n");

 	if (st->gpios->ndescs != st->chip_info->num_gpios) {
 		dev_err(&pdev->dev, "%d GPIOs needed to operate\n",
 			st->chip_info->num_gpios);
 		return -ENODEV;
 	}

 	ret = devm_regulator_get_enable(&pdev->dev, "vcc-supply");
 	if (ret)
 		return ret;

 	mutex_init(&st->lock);

 	indio_dev->info = &hmc425a_info;
 	indio_dev->modes = INDIO_DIRECT_MODE;

 	if (st->chip_info->has_powerdown) {
 		st->powerdown = true;
 		hmc425a_write(indio_dev, st->chip_info->powerdown_val);
 	} else {
 		/* Set default gain */
 		hmc425a_write(indio_dev, st->gain);
 	}

 	return devm_iio_device_register(&pdev->dev, indio_dev);
 }

 /* Match table for of_platform binding */
 static const struct of_device_id hmc425a_of_match[] = {
 	{ .compatible = "adi,hmc425a",
 	  .data = &hmc425a_chip_info_tbl[ID_HMC425A]},
 	{ .compatible = "adi,hmc540s",
 	  .data = &hmc425a_chip_info_tbl[ID_HMC540S]},
 	{ .compatible = "adi,adrf5740",
 	  .data = &hmc425a_chip_info_tbl[ID_ADRF5740]},
 	{ .compatible = "adi,ltc6373",
 	  .data = &hmc425a_chip_info_tbl[ID_LTC6373]},
 	{}
 };
 MODULE_DEVICE_TABLE(of, hmc425a_of_match);

 static struct platform_driver hmc425a_driver = {
 	.driver = {
 		.name = KBUILD_MODNAME,
 		.of_match_table = hmc425a_of_match,
 	},
 	.probe = hmc425a_probe,
 };
 module_platform_driver(hmc425a_driver);

 MODULE_AUTHOR("Michael Hennerich <michael.hennerich@analog.com>");
 MODULE_DESCRIPTION("Analog Devices HMC425A and similar GPIO control Gain Amplifiers");
 MODULE_LICENSE("GPL v2");
	// SPDX-License-Identifier: GPL-2.0
	/*
	* HMC425A and similar Gain Amplifiers
	*
	* Copyright 2020, 2024 Analog Devices Inc.
	*/

	#include <linux/bits.h>
	#include <linux/bitops.h>
	#include <linux/device.h>
	#include <linux/err.h>
	#include <linux/gpio/consumer.h>
	#include <linux/iio/iio.h>
	#include <linux/iio/sysfs.h>
	#include <linux/kernel.h>
	#include <linux/math.h>
	#include <linux/mod_devicetable.h>
	#include <linux/module.h>
	#include <linux/platform_device.h>
	#include <linux/property.h>
	#include <linux/slab.h>
	#include <linux/regulator/consumer.h>
	#include <linux/sysfs.h>

	/*
	* The LTC6373 amplifier supports configuring gain using GPIO's with the following
	* values (OUTPUT_V / INPUT_V): 0(shutdown), 0.25, 0.5, 1, 2, 4, 8, 16
	*
	* Except for the shutdown value, all can be converted to dB using 20 * log10(x)
	* From here, it is observed that all values are multiples of the '2' gain setting,
	* with the correspondent of 6.020dB.
	*/
	#define LTC6373_CONVERSION_CONSTANT 6020
	#define LTC6373_MIN_GAIN_CODE 0x6
	#define LTC6373_CONVERSION_MASK GENMASK(2, 0)
	#define LTC6373_SHUTDOWN GENMASK(2, 0)

	enum hmc425a_type {
	ID_HMC425A,
	ID_HMC540S,
	ID_ADRF5740,
	ID_LTC6373,
	};

	struct hmc425a_chip_info {
	const char *name;
	const struct iio_chan_spec *channels;
	unsigned int num_channels;
	unsigned int num_gpios;
	int gain_min;
	int gain_max;
	int default_gain;
	int powerdown_val;
	bool has_powerdown;

	int (gain_dB_to_code)(int gain, int code);
	int (code_to_gain_dB)(int code, int val, int *val2);
	};

	struct hmc425a_state {
	struct mutex lock; /* protect sensor state */
	const struct hmc425a_chip_info *chip_info;
	struct gpio_descs *gpios;
	u32 gain;
	bool powerdown;
	};

	static int gain_dB_to_code(struct hmc425a_state st, int val, int val2, int code)
	{
	const struct hmc425a_chip_info *inf = st->chip_info;
	int gain;

	if (val < 0)
	gain = (val * 1000) - (val2 / 1000);
	else
	gain = (val * 1000) + (val2 / 1000);

	if (gain > inf->gain_max \|\| gain < inf->gain_min)
	return -EINVAL;
	if (st->powerdown)
	return -EPERM;

	return st->chip_info->gain_dB_to_code(gain, code);
	}

	static int hmc425a_gain_dB_to_code(int gain, int *code)
	{
	*code = ~((abs(gain) / 500) & 0x3F);
	return 0;
	}

	static int hmc540s_gain_dB_to_code(int gain, int *code)
	{
	*code = ~((abs(gain) / 1000) & 0xF);
	return 0;
	}

	static int adrf5740_gain_dB_to_code(int gain, int *code)
	{
	int temp = (abs(gain) / 2000) & 0xF;

	/* Bit [0-3]: 2dB 4dB 8dB 8dB */
	*code = temp & BIT(3) ? temp \| BIT(2) : temp;
	return 0;
	}

	static int ltc6373_gain_dB_to_code(int gain, int *code)
	{
	*code = ~(DIV_ROUND_CLOSEST(gain, LTC6373_CONVERSION_CONSTANT) + 3)
	& LTC6373_CONVERSION_MASK;
	return 0;
	}

	static int code_to_gain_dB(struct hmc425a_state st, int val, int *val2)
	{
	if (st->powerdown)
	return -EPERM;
	return st->chip_info->code_to_gain_dB(st->gain, val, val2);
	}

	static int hmc425a_code_to_gain_dB(int code, int val, int val2)
	{
	val = (~code -500) / 1000;
	val2 = ((~code -500) % 1000) * 1000;
	return 0;
	}

	static int hmc540s_code_to_gain_dB(int code, int val, int val2)
	{
	val = (~code -1000) / 1000;
	val2 = ((~code -1000) % 1000) * 1000;
	return 0;
	}

	static int adrf5740_code_to_gain_dB(int code, int val, int val2)
	{
	/*
	* Bit [0-3]: 2dB 4dB 8dB 8dB
	* When BIT(3) is set, unset BIT(2) and use 3 as double the place value
	*/
	code = code & BIT(3) ? code & ~BIT(2) : code;
	val = (code -2000) / 1000;
	val2 = ((code -2000) % 1000) * 1000;
	return 0;
	}

	static int ltc6373_code_to_gain_dB(int code, int val, int val2)
	{
	int gain = ((~code & LTC6373_CONVERSION_MASK) - 3) *
	LTC6373_CONVERSION_CONSTANT;

	*val = gain / 1000;
	val2 = (gain % 1000) 1000;
	return 0;
	}

	static int hmc425a_write(struct iio_dev *indio_dev, u32 value)
	{
	struct hmc425a_state *st = iio_priv(indio_dev);
	DECLARE_BITMAP(values, BITS_PER_TYPE(value));

	values[0] = value;

	gpiod_set_array_value_cansleep(st->gpios->ndescs, st->gpios->desc,
	NULL, values);
	return 0;
	}

	static int hmc425a_read_raw(struct iio_dev *indio_dev,
	struct iio_chan_spec const chan, int val,
	int *val2, long m)
	{
	struct hmc425a_state *st = iio_priv(indio_dev);
	int ret;

	mutex_lock(&st->lock);
	switch (m) {
	case IIO_CHAN_INFO_HARDWAREGAIN:
	ret = code_to_gain_dB(st, val, val2);
	if (ret)
	break;
	ret = IIO_VAL_INT_PLUS_MICRO_DB;
	break;
	default:
	ret = -EINVAL;
	}
	mutex_unlock(&st->lock);

	return ret;
	};

	static int hmc425a_write_raw(struct iio_dev *indio_dev,
	struct iio_chan_spec const *chan, int val,
	int val2, long mask)
	{
	struct hmc425a_state *st = iio_priv(indio_dev);
	int code = 0, ret;

	mutex_lock(&st->lock);
	switch (mask) {
	case IIO_CHAN_INFO_HARDWAREGAIN:
	ret = gain_dB_to_code(st, val, val2, &code);
	if (ret)
	break;
	st->gain = code;

	ret = hmc425a_write(indio_dev, st->gain);
	break;
	default:
	ret = -EINVAL;
	}
	mutex_unlock(&st->lock);

	return ret;
	}

	static int hmc425a_write_raw_get_fmt(struct iio_dev *indio_dev,
	struct iio_chan_spec const *chan,
	long mask)
	{
	switch (mask) {
	case IIO_CHAN_INFO_HARDWAREGAIN:
	return IIO_VAL_INT_PLUS_MICRO_DB;
	default:
	return -EINVAL;
	}
	}

	static const struct iio_info hmc425a_info = {
	.read_raw = &hmc425a_read_raw,
	.write_raw = &hmc425a_write_raw,
	.write_raw_get_fmt = &hmc425a_write_raw_get_fmt,
	};

	static ssize_t ltc6373_read_powerdown(struct iio_dev *indio_dev,
	uintptr_t private,
	const struct iio_chan_spec *chan,
	char *buf)
	{
	struct hmc425a_state *st = iio_priv(indio_dev);

	return sysfs_emit(buf, "%d\n", st->powerdown);
	}

	static ssize_t ltc6373_write_powerdown(struct iio_dev *indio_dev,
	uintptr_t private,
	const struct iio_chan_spec *chan,
	const char *buf,
	size_t len)
	{
	struct hmc425a_state *st = iio_priv(indio_dev);
	bool powerdown;
	int code, ret;

	ret = kstrtobool(buf, &powerdown);
	if (ret)
	return ret;

	mutex_lock(&st->lock);
	st->powerdown = powerdown;
	code = (powerdown) ? LTC6373_SHUTDOWN : st->gain;
	hmc425a_write(indio_dev, code);
	mutex_unlock(&st->lock);
	return len;
	}

	static const struct iio_chan_spec_ext_info ltc6373_ext_info[] = {
	{
	.name = "powerdown",
	.read = ltc6373_read_powerdown,
	.write = ltc6373_write_powerdown,
	.shared = IIO_SEPARATE,
	},
	{}
	};

	#define HMC425A_CHAN(_channel) \
	{ \
	.type = IIO_VOLTAGE, \
	.output = 1, \
	.indexed = 1, \
	.channel = _channel, \
	.info_mask_separate = BIT(IIO_CHAN_INFO_HARDWAREGAIN), \
	}

	#define LTC6373_CHAN(_channel) \
	{ \
	.type = IIO_VOLTAGE, \
	.output = 1, \
	.indexed = 1, \
	.channel = _channel, \
	.info_mask_separate = BIT(IIO_CHAN_INFO_HARDWAREGAIN), \
	.ext_info = ltc6373_ext_info, \
	}

	static const struct iio_chan_spec hmc425a_channels[] = {
	HMC425A_CHAN(0),
	};

	static const struct iio_chan_spec ltc6373_channels[] = {
	LTC6373_CHAN(0),
	};

	static const struct hmc425a_chip_info hmc425a_chip_info_tbl[] = {
	[ID_HMC425A] = {
	.name = "hmc425a",
	.channels = hmc425a_channels,
	.num_channels = ARRAY_SIZE(hmc425a_channels),
	.num_gpios = 6,
	.gain_min = -31500,
	.gain_max = 0,
	.default_gain = -0x40, /* set default gain -31.5db*/
	.gain_dB_to_code = hmc425a_gain_dB_to_code,
	.code_to_gain_dB = hmc425a_code_to_gain_dB,
	},
	[ID_HMC540S] = {
	.name = "hmc540s",
	.channels = hmc425a_channels,
	.num_channels = ARRAY_SIZE(hmc425a_channels),
	.num_gpios = 4,
	.gain_min = -15000,
	.gain_max = 0,
	.default_gain = -0x10, /* set default gain -15.0db*/
	.gain_dB_to_code = hmc540s_gain_dB_to_code,
	.code_to_gain_dB = hmc540s_code_to_gain_dB,
	},
	[ID_ADRF5740] = {
	.name = "adrf5740",
	.channels = hmc425a_channels,
	.num_channels = ARRAY_SIZE(hmc425a_channels),
	.num_gpios = 4,
	.gain_min = -22000,
	.gain_max = 0,
	.default_gain = 0xF, /* set default gain -22.0db*/
	.gain_dB_to_code = adrf5740_gain_dB_to_code,
	.code_to_gain_dB = adrf5740_code_to_gain_dB,
	},
	[ID_LTC6373] = {
	.name = "ltc6373",
	.channels = ltc6373_channels,
	.num_channels = ARRAY_SIZE(ltc6373_channels),
	.num_gpios = 3,
	.gain_min = -12041, /* gain setting x0.25*/
	.gain_max = 24082, /* gain setting x16 */
	.default_gain = LTC6373_MIN_GAIN_CODE,
	.powerdown_val = LTC6373_SHUTDOWN,
	.has_powerdown = true,
	.gain_dB_to_code = ltc6373_gain_dB_to_code,
	.code_to_gain_dB = ltc6373_code_to_gain_dB,
	},
	};

	static int hmc425a_probe(struct platform_device *pdev)
	{
	struct iio_dev *indio_dev;
	struct hmc425a_state *st;
	int ret;

	indio_dev = devm_iio_device_alloc(&pdev->dev, sizeof(*st));
	if (!indio_dev)
	return -ENOMEM;

	st = iio_priv(indio_dev);

	st->chip_info = device_get_match_data(&pdev->dev);
	indio_dev->num_channels = st->chip_info->num_channels;
	indio_dev->channels = st->chip_info->channels;
	indio_dev->name = st->chip_info->name;
	st->gain = st->chip_info->default_gain;

	st->gpios = devm_gpiod_get_array(&pdev->dev, "ctrl", GPIOD_OUT_LOW);
	if (IS_ERR(st->gpios))
	return dev_err_probe(&pdev->dev, PTR_ERR(st->gpios),
	"failed to get gpios\n");

	if (st->gpios->ndescs != st->chip_info->num_gpios) {
	dev_err(&pdev->dev, "%d GPIOs needed to operate\n",
	st->chip_info->num_gpios);
	return -ENODEV;
	}

	ret = devm_regulator_get_enable(&pdev->dev, "vcc-supply");
	if (ret)
	return ret;

	mutex_init(&st->lock);

	indio_dev->info = &hmc425a_info;
	indio_dev->modes = INDIO_DIRECT_MODE;

	if (st->chip_info->has_powerdown) {
	st->powerdown = true;
	hmc425a_write(indio_dev, st->chip_info->powerdown_val);
	} else {
	/* Set default gain */
	hmc425a_write(indio_dev, st->gain);
	}

	return devm_iio_device_register(&pdev->dev, indio_dev);
	}

	/* Match table for of_platform binding */
	static const struct of_device_id hmc425a_of_match[] = {
	{ .compatible = "adi,hmc425a",
	.data = &hmc425a_chip_info_tbl[ID_HMC425A]},
	{ .compatible = "adi,hmc540s",
	.data = &hmc425a_chip_info_tbl[ID_HMC540S]},
	{ .compatible = "adi,adrf5740",
	.data = &hmc425a_chip_info_tbl[ID_ADRF5740]},
	{ .compatible = "adi,ltc6373",
	.data = &hmc425a_chip_info_tbl[ID_LTC6373]},
	{}
	};
	MODULE_DEVICE_TABLE(of, hmc425a_of_match);

	static struct platform_driver hmc425a_driver = {
	.driver = {
	.name = KBUILD_MODNAME,
	.of_match_table = hmc425a_of_match,
	},
	.probe = hmc425a_probe,
	};
	module_platform_driver(hmc425a_driver);

	MODULE_AUTHOR("Michael Hennerich <michael.hennerich@analog.com>");
	MODULE_DESCRIPTION("Analog Devices HMC425A and similar GPIO control Gain Amplifiers");
	MODULE_LICENSE("GPL v2");