drivers/iio/light/ltr390.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * IIO driver for Lite-On LTR390 ALS and UV sensor
  * (7-bit I2C slave address 0x53)
  *
  * Based on the work of:
  *   Shreeya Patel and Shi Zhigang (LTRF216 Driver)
  *
  * Copyright (C) 2023 Anshul Dalal <anshulusr@gmail.com>
  *
  * Datasheet:
  *   https://optoelectronics.liteon.com/upload/download/DS86-2015-0004/LTR-390UV_Final_%20DS_V1%201.pdf
  *
  * TODO:
  *   - Support for configurable gain and resolution
  *   - Sensor suspend/resume support
  *   - Add support for reading the ALS
  *   - Interrupt support
  */

 #include <linux/i2c.h>
 #include <linux/math.h>
 #include <linux/module.h>
 #include <linux/mutex.h>
 #include <linux/regmap.h>
 #include <linux/bitfield.h>

 #include <linux/iio/iio.h>

 #include <linux/unaligned.h>

 #define LTR390_MAIN_CTRL		0x00
 #define LTR390_ALS_UVS_MEAS_RATE	0x04
 #define LTR390_ALS_UVS_GAIN		0x05
 #define LTR390_PART_ID			0x06
 #define LTR390_ALS_DATA			0x0D
 #define LTR390_UVS_DATA			0x10
 #define LTR390_INT_CFG			0x19

 #define LTR390_PART_NUMBER_ID		0xb
 #define LTR390_ALS_UVS_GAIN_MASK	0x07
 #define LTR390_ALS_UVS_INT_TIME_MASK	0x70
 #define LTR390_ALS_UVS_INT_TIME(x)	FIELD_PREP(LTR390_ALS_UVS_INT_TIME_MASK, (x))

 #define LTR390_SW_RESET	      BIT(4)
 #define LTR390_UVS_MODE	      BIT(3)
 #define LTR390_SENSOR_ENABLE  BIT(1)

 #define LTR390_FRACTIONAL_PRECISION 100

 /*
  * At 20-bit resolution (integration time: 400ms) and 18x gain, 2300 counts of
  * the sensor are equal to 1 UV Index [Datasheet Page#8].
  *
  * For the default resolution of 18-bit (integration time: 100ms) and default
  * gain of 3x, the counts/uvi are calculated as follows:
  * 2300 / ((3/18) * (100/400)) = 95.83
  */
 #define LTR390_COUNTS_PER_UVI 96

 /*
  * Window Factor is needed when the device is under Window glass with coated
  * tinted ink. This is to compensate for the light loss due to the lower
  * transmission rate of the window glass and helps * in calculating lux.
  */
 #define LTR390_WINDOW_FACTOR 1

 enum ltr390_mode {
 	LTR390_SET_ALS_MODE,
 	LTR390_SET_UVS_MODE,
 };

 struct ltr390_data {
 	struct regmap *regmap;
 	struct i2c_client *client;
 	/* Protects device from simulataneous reads */
 	struct mutex lock;
 	enum ltr390_mode mode;
 	int gain;
 	int int_time_us;
 };

 static const struct regmap_config ltr390_regmap_config = {
 	.name = "ltr390",
 	.reg_bits = 8,
 	.reg_stride = 1,
 	.val_bits = 8,
 };

 static int ltr390_register_read(struct ltr390_data *data, u8 register_address)
 {
 	struct device *dev = &data->client->dev;
 	int ret;
 	u8 recieve_buffer[3];

 	ret = regmap_bulk_read(data->regmap, register_address, recieve_buffer,
 			       sizeof(recieve_buffer));
 	if (ret) {
 		dev_err(dev, "failed to read measurement data");
 		return ret;
 	}

 	return get_unaligned_le24(recieve_buffer);
 }

 static int ltr390_set_mode(struct ltr390_data *data, enum ltr390_mode mode)
 {
 	int ret;

 	if (data->mode == mode)
 		return 0;

 	switch (mode) {
 	case LTR390_SET_ALS_MODE:
 		ret = regmap_clear_bits(data->regmap, LTR390_MAIN_CTRL, LTR390_UVS_MODE);
 		break;

 	case LTR390_SET_UVS_MODE:
 		ret = regmap_set_bits(data->regmap, LTR390_MAIN_CTRL, LTR390_UVS_MODE);
 		break;
 	}

 	if (ret)
 		return ret;

 	data->mode = mode;
 	return 0;
 }

 static int ltr390_counts_per_uvi(struct ltr390_data *data)
 {
 	const int orig_gain = 18;
 	const int orig_int_time = 400;

 	return DIV_ROUND_CLOSEST(23 * data->gain * data->int_time_us, 10 * orig_gain * orig_int_time);
 }

 static int ltr390_read_raw(struct iio_dev *iio_device,
 			   struct iio_chan_spec const *chan, int *val,
 			   int *val2, long mask)
 {
 	int ret;
 	struct ltr390_data *data = iio_priv(iio_device);

 	guard(mutex)(&data->lock);
 	switch (mask) {
 	case IIO_CHAN_INFO_RAW:
 		switch (chan->type) {
 		case IIO_UVINDEX:
 			ret = ltr390_set_mode(data, LTR390_SET_UVS_MODE);
 			if (ret < 0)
 				return ret;

 			ret = ltr390_register_read(data, LTR390_UVS_DATA);
 			if (ret < 0)
 				return ret;
 			break;

 		case IIO_LIGHT:
 			ret = ltr390_set_mode(data, LTR390_SET_ALS_MODE);
 			if (ret < 0)
 				return ret;

 			ret = ltr390_register_read(data, LTR390_ALS_DATA);
 			if (ret < 0)
 				return ret;
 			break;

 		default:
 			return -EINVAL;
 		}
 		*val = ret;
 		return IIO_VAL_INT;
 	case IIO_CHAN_INFO_SCALE:
 		switch (chan->type) {
 		case IIO_UVINDEX:
 			*val = LTR390_WINDOW_FACTOR * LTR390_FRACTIONAL_PRECISION;
 			*val2 = ltr390_counts_per_uvi(data);
 			return IIO_VAL_FRACTIONAL;

 		case IIO_LIGHT:
 			*val = LTR390_WINDOW_FACTOR * 6 * 100;
 			*val2 = data->gain * data->int_time_us;
 			return IIO_VAL_FRACTIONAL;

 		default:
 			return -EINVAL;
 		}

 	case IIO_CHAN_INFO_INT_TIME:
 		*val = data->int_time_us;
 		return IIO_VAL_INT;

 	default:
 		return -EINVAL;
 	}
 }

 /* integration time in us */
 static const int ltr390_int_time_map_us[] = { 400000, 200000, 100000, 50000, 25000, 12500 };
 static const int ltr390_gain_map[] = { 1, 3, 6, 9, 18 };

 static const struct iio_chan_spec ltr390_channels[] = {
 	/* UV sensor */
 	{
 		.type = IIO_UVINDEX,
 		.scan_index = 0,
 		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE),
 		.info_mask_shared_by_all = BIT(IIO_CHAN_INFO_INT_TIME),
 		.info_mask_shared_by_all_available = BIT(IIO_CHAN_INFO_INT_TIME) | BIT(IIO_CHAN_INFO_SCALE)
 	},
 	/* ALS sensor */
 	{
 		.type = IIO_LIGHT,
 		.scan_index = 1,
 		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE),
 		.info_mask_shared_by_all = BIT(IIO_CHAN_INFO_INT_TIME),
 		.info_mask_shared_by_all_available = BIT(IIO_CHAN_INFO_INT_TIME) | BIT(IIO_CHAN_INFO_SCALE)
 	},
 };

 static int ltr390_set_gain(struct ltr390_data *data, int val)
 {
 	int ret, idx;

 	for (idx = 0; idx < ARRAY_SIZE(ltr390_gain_map); idx++) {
 		if (ltr390_gain_map[idx] != val)
 			continue;

 		guard(mutex)(&data->lock);
 		ret = regmap_update_bits(data->regmap,
 					LTR390_ALS_UVS_GAIN,
 					LTR390_ALS_UVS_GAIN_MASK, idx);
 		if (ret)
 			return ret;

 		data->gain = ltr390_gain_map[idx];
 		return 0;
 	}

 	return -EINVAL;
 }

 static int ltr390_set_int_time(struct ltr390_data *data, int val)
 {
 	int ret, idx;

 	for (idx = 0; idx < ARRAY_SIZE(ltr390_int_time_map_us); idx++) {
 		if (ltr390_int_time_map_us[idx] != val)
 			continue;

 		guard(mutex)(&data->lock);
 		ret = regmap_update_bits(data->regmap,
 					LTR390_ALS_UVS_MEAS_RATE,
 					LTR390_ALS_UVS_INT_TIME_MASK,
 					LTR390_ALS_UVS_INT_TIME(idx));
 		if (ret)
 			return ret;

 		data->int_time_us = ltr390_int_time_map_us[idx];
 		return 0;
 	}

 	return -EINVAL;
 }

 static int ltr390_read_avail(struct iio_dev *indio_dev, struct iio_chan_spec const *chan,
 				const int **vals, int *type, int *length, long mask)
 {
 	switch (mask) {
 	case IIO_CHAN_INFO_SCALE:
 		*length = ARRAY_SIZE(ltr390_gain_map);
 		*type = IIO_VAL_INT;
 		*vals = ltr390_gain_map;
 		return IIO_AVAIL_LIST;
 	case IIO_CHAN_INFO_INT_TIME:
 		*length = ARRAY_SIZE(ltr390_int_time_map_us);
 		*type = IIO_VAL_INT;
 		*vals = ltr390_int_time_map_us;
 		return IIO_AVAIL_LIST;
 	default:
 		return -EINVAL;
 	}
 }

 static int ltr390_write_raw(struct iio_dev *indio_dev, struct iio_chan_spec const *chan,
 				int val, int val2, long mask)
 {
 	struct ltr390_data *data = iio_priv(indio_dev);

 	switch (mask) {
 	case IIO_CHAN_INFO_SCALE:
 		if (val2 != 0)
 			return -EINVAL;

 		return ltr390_set_gain(data, val);

 	case IIO_CHAN_INFO_INT_TIME:
 		if (val2 != 0)
 			return -EINVAL;

 		return ltr390_set_int_time(data, val);

 	default:
 		return -EINVAL;
 	}
 }

 static const struct iio_info ltr390_info = {
 	.read_raw = ltr390_read_raw,
 	.write_raw = ltr390_write_raw,
 	.read_avail = ltr390_read_avail,
 };

 static int ltr390_probe(struct i2c_client *client)
 {
 	struct ltr390_data *data;
 	struct iio_dev *indio_dev;
 	struct device *dev;
 	int ret, part_number;

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

 	data = iio_priv(indio_dev);

 	data->regmap = devm_regmap_init_i2c(client, &ltr390_regmap_config);
 	if (IS_ERR(data->regmap))
 		return dev_err_probe(dev, PTR_ERR(data->regmap),
 				     "regmap initialization failed\n");

 	data->client = client;
 	/* default value of integration time from pg: 15 of the datasheet */
 	data->int_time_us = 100000;
 	/* default value of gain from pg: 16 of the datasheet */
 	data->gain = 3;
 	/* default mode for ltr390 is ALS mode */
 	data->mode = LTR390_SET_ALS_MODE;

 	mutex_init(&data->lock);

 	indio_dev->info = &ltr390_info;
 	indio_dev->channels = ltr390_channels;
 	indio_dev->num_channels = ARRAY_SIZE(ltr390_channels);
 	indio_dev->name = "ltr390";

 	ret = regmap_read(data->regmap, LTR390_PART_ID, &part_number);
 	if (ret)
 		return dev_err_probe(dev, ret,
 				     "failed to get sensor's part id\n");
 	/* Lower 4 bits of `part_number` change with hardware revisions */
 	if (part_number >> 4 != LTR390_PART_NUMBER_ID)
 		dev_info(dev, "received invalid product id: 0x%x", part_number);
 	dev_dbg(dev, "LTR390, product id: 0x%x\n", part_number);

 	/* reset sensor, chip fails to respond to this, so ignore any errors */
 	regmap_set_bits(data->regmap, LTR390_MAIN_CTRL, LTR390_SW_RESET);

 	/* Wait for the registers to reset before proceeding */
 	usleep_range(1000, 2000);

 	ret = regmap_set_bits(data->regmap, LTR390_MAIN_CTRL, LTR390_SENSOR_ENABLE);
 	if (ret)
 		return dev_err_probe(dev, ret, "failed to enable the sensor\n");

 	return devm_iio_device_register(dev, indio_dev);
 }

 static const struct i2c_device_id ltr390_id[] = {
 	{ "ltr390" },
 	{ /* Sentinel */ }
 };
 MODULE_DEVICE_TABLE(i2c, ltr390_id);

 static const struct of_device_id ltr390_of_table[] = {
 	{ .compatible = "liteon,ltr390" },
 	{ /* Sentinel */ }
 };
 MODULE_DEVICE_TABLE(of, ltr390_of_table);

 static struct i2c_driver ltr390_driver = {
 	.driver = {
 		.name = "ltr390",
 		.of_match_table = ltr390_of_table,
 	},
 	.probe = ltr390_probe,
 	.id_table = ltr390_id,
 };
 module_i2c_driver(ltr390_driver);

 MODULE_AUTHOR("Anshul Dalal <anshulusr@gmail.com>");
 MODULE_DESCRIPTION("Lite-On LTR390 ALS and UV sensor Driver");
 MODULE_LICENSE("GPL");
	// SPDX-License-Identifier: GPL-2.0-or-later
	/*
	* IIO driver for Lite-On LTR390 ALS and UV sensor
	* (7-bit I2C slave address 0x53)
	*
	* Based on the work of:
	* Shreeya Patel and Shi Zhigang (LTRF216 Driver)
	*
	* Copyright (C) 2023 Anshul Dalal <anshulusr@gmail.com>
	*
	* Datasheet:
	* https://optoelectronics.liteon.com/upload/download/DS86-2015-0004/LTR-390UV_Final_%20DS_V1%201.pdf
	*
	* TODO:
	* - Support for configurable gain and resolution
	* - Sensor suspend/resume support
	* - Add support for reading the ALS
	* - Interrupt support
	*/

	#include <linux/i2c.h>
	#include <linux/math.h>
	#include <linux/module.h>
	#include <linux/mutex.h>
	#include <linux/regmap.h>
	#include <linux/bitfield.h>

	#include <linux/iio/iio.h>

	#include <linux/unaligned.h>

	#define LTR390_MAIN_CTRL 0x00
	#define LTR390_ALS_UVS_MEAS_RATE 0x04
	#define LTR390_ALS_UVS_GAIN 0x05
	#define LTR390_PART_ID 0x06
	#define LTR390_ALS_DATA 0x0D
	#define LTR390_UVS_DATA 0x10
	#define LTR390_INT_CFG 0x19

	#define LTR390_PART_NUMBER_ID 0xb
	#define LTR390_ALS_UVS_GAIN_MASK 0x07
	#define LTR390_ALS_UVS_INT_TIME_MASK 0x70
	#define LTR390_ALS_UVS_INT_TIME(x) FIELD_PREP(LTR390_ALS_UVS_INT_TIME_MASK, (x))

	#define LTR390_SW_RESET BIT(4)
	#define LTR390_UVS_MODE BIT(3)
	#define LTR390_SENSOR_ENABLE BIT(1)

	#define LTR390_FRACTIONAL_PRECISION 100

	/*
	* At 20-bit resolution (integration time: 400ms) and 18x gain, 2300 counts of
	* the sensor are equal to 1 UV Index [Datasheet Page#8].
	*
	* For the default resolution of 18-bit (integration time: 100ms) and default
	* gain of 3x, the counts/uvi are calculated as follows:
	* 2300 / ((3/18) * (100/400)) = 95.83
	*/
	#define LTR390_COUNTS_PER_UVI 96

	/*
	* Window Factor is needed when the device is under Window glass with coated
	* tinted ink. This is to compensate for the light loss due to the lower
	* transmission rate of the window glass and helps * in calculating lux.
	*/
	#define LTR390_WINDOW_FACTOR 1

	enum ltr390_mode {
	LTR390_SET_ALS_MODE,
	LTR390_SET_UVS_MODE,
	};

	struct ltr390_data {
	struct regmap *regmap;
	struct i2c_client *client;
	/* Protects device from simulataneous reads */
	struct mutex lock;
	enum ltr390_mode mode;
	int gain;
	int int_time_us;
	};

	static const struct regmap_config ltr390_regmap_config = {
	.name = "ltr390",
	.reg_bits = 8,
	.reg_stride = 1,
	.val_bits = 8,
	};

	static int ltr390_register_read(struct ltr390_data *data, u8 register_address)
	{
	struct device *dev = &data->client->dev;
	int ret;
	u8 recieve_buffer[3];

	ret = regmap_bulk_read(data->regmap, register_address, recieve_buffer,
	sizeof(recieve_buffer));
	if (ret) {
	dev_err(dev, "failed to read measurement data");
	return ret;
	}

	return get_unaligned_le24(recieve_buffer);
	}

	static int ltr390_set_mode(struct ltr390_data *data, enum ltr390_mode mode)
	{
	int ret;

	if (data->mode == mode)
	return 0;

	switch (mode) {
	case LTR390_SET_ALS_MODE:
	ret = regmap_clear_bits(data->regmap, LTR390_MAIN_CTRL, LTR390_UVS_MODE);
	break;

	case LTR390_SET_UVS_MODE:
	ret = regmap_set_bits(data->regmap, LTR390_MAIN_CTRL, LTR390_UVS_MODE);
	break;
	}

	if (ret)
	return ret;

	data->mode = mode;
	return 0;
	}

	static int ltr390_counts_per_uvi(struct ltr390_data *data)
	{
	const int orig_gain = 18;
	const int orig_int_time = 400;

	return DIV_ROUND_CLOSEST(23 * data->gain * data->int_time_us, 10 * orig_gain * orig_int_time);
	}

	static int ltr390_read_raw(struct iio_dev *iio_device,
	struct iio_chan_spec const chan, int val,
	int *val2, long mask)
	{
	int ret;
	struct ltr390_data *data = iio_priv(iio_device);

	guard(mutex)(&data->lock);
	switch (mask) {
	case IIO_CHAN_INFO_RAW:
	switch (chan->type) {
	case IIO_UVINDEX:
	ret = ltr390_set_mode(data, LTR390_SET_UVS_MODE);
	if (ret < 0)
	return ret;

	ret = ltr390_register_read(data, LTR390_UVS_DATA);
	if (ret < 0)
	return ret;
	break;

	case IIO_LIGHT:
	ret = ltr390_set_mode(data, LTR390_SET_ALS_MODE);
	if (ret < 0)
	return ret;

	ret = ltr390_register_read(data, LTR390_ALS_DATA);
	if (ret < 0)
	return ret;
	break;

	default:
	return -EINVAL;
	}
	*val = ret;
	return IIO_VAL_INT;
	case IIO_CHAN_INFO_SCALE:
	switch (chan->type) {
	case IIO_UVINDEX:
	val = LTR390_WINDOW_FACTOR LTR390_FRACTIONAL_PRECISION;
	*val2 = ltr390_counts_per_uvi(data);
	return IIO_VAL_FRACTIONAL;

	case IIO_LIGHT:
	val = LTR390_WINDOW_FACTOR 6 * 100;
	val2 = data->gain data->int_time_us;
	return IIO_VAL_FRACTIONAL;

	default:
	return -EINVAL;
	}

	case IIO_CHAN_INFO_INT_TIME:
	*val = data->int_time_us;
	return IIO_VAL_INT;

	default:
	return -EINVAL;
	}
	}

	/* integration time in us */
	static const int ltr390_int_time_map_us[] = { 400000, 200000, 100000, 50000, 25000, 12500 };
	static const int ltr390_gain_map[] = { 1, 3, 6, 9, 18 };

	static const struct iio_chan_spec ltr390_channels[] = {
	/* UV sensor */
	{
	.type = IIO_UVINDEX,
	.scan_index = 0,
	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) \| BIT(IIO_CHAN_INFO_SCALE),
	.info_mask_shared_by_all = BIT(IIO_CHAN_INFO_INT_TIME),
	.info_mask_shared_by_all_available = BIT(IIO_CHAN_INFO_INT_TIME) \| BIT(IIO_CHAN_INFO_SCALE)
	},
	/* ALS sensor */
	{
	.type = IIO_LIGHT,
	.scan_index = 1,
	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) \| BIT(IIO_CHAN_INFO_SCALE),
	.info_mask_shared_by_all = BIT(IIO_CHAN_INFO_INT_TIME),
	.info_mask_shared_by_all_available = BIT(IIO_CHAN_INFO_INT_TIME) \| BIT(IIO_CHAN_INFO_SCALE)
	},
	};

	static int ltr390_set_gain(struct ltr390_data *data, int val)
	{
	int ret, idx;

	for (idx = 0; idx < ARRAY_SIZE(ltr390_gain_map); idx++) {
	if (ltr390_gain_map[idx] != val)
	continue;

	guard(mutex)(&data->lock);
	ret = regmap_update_bits(data->regmap,
	LTR390_ALS_UVS_GAIN,
	LTR390_ALS_UVS_GAIN_MASK, idx);
	if (ret)
	return ret;

	data->gain = ltr390_gain_map[idx];
	return 0;
	}

	return -EINVAL;
	}

	static int ltr390_set_int_time(struct ltr390_data *data, int val)
	{
	int ret, idx;

	for (idx = 0; idx < ARRAY_SIZE(ltr390_int_time_map_us); idx++) {
	if (ltr390_int_time_map_us[idx] != val)
	continue;

	guard(mutex)(&data->lock);
	ret = regmap_update_bits(data->regmap,
	LTR390_ALS_UVS_MEAS_RATE,
	LTR390_ALS_UVS_INT_TIME_MASK,
	LTR390_ALS_UVS_INT_TIME(idx));
	if (ret)
	return ret;

	data->int_time_us = ltr390_int_time_map_us[idx];
	return 0;
	}

	return -EINVAL;
	}

	static int ltr390_read_avail(struct iio_dev indio_dev, struct iio_chan_spec const chan,
	const int *vals, int type, int *length, long mask)
	{
	switch (mask) {
	case IIO_CHAN_INFO_SCALE:
	*length = ARRAY_SIZE(ltr390_gain_map);
	*type = IIO_VAL_INT;
	*vals = ltr390_gain_map;
	return IIO_AVAIL_LIST;
	case IIO_CHAN_INFO_INT_TIME:
	*length = ARRAY_SIZE(ltr390_int_time_map_us);
	*type = IIO_VAL_INT;
	*vals = ltr390_int_time_map_us;
	return IIO_AVAIL_LIST;
	default:
	return -EINVAL;
	}
	}

	static int ltr390_write_raw(struct iio_dev indio_dev, struct iio_chan_spec const chan,
	int val, int val2, long mask)
	{
	struct ltr390_data *data = iio_priv(indio_dev);

	switch (mask) {
	case IIO_CHAN_INFO_SCALE:
	if (val2 != 0)
	return -EINVAL;

	return ltr390_set_gain(data, val);

	case IIO_CHAN_INFO_INT_TIME:
	if (val2 != 0)
	return -EINVAL;

	return ltr390_set_int_time(data, val);

	default:
	return -EINVAL;
	}
	}

	static const struct iio_info ltr390_info = {
	.read_raw = ltr390_read_raw,
	.write_raw = ltr390_write_raw,
	.read_avail = ltr390_read_avail,
	};

	static int ltr390_probe(struct i2c_client *client)
	{
	struct ltr390_data *data;
	struct iio_dev *indio_dev;
	struct device *dev;
	int ret, part_number;

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

	data = iio_priv(indio_dev);

	data->regmap = devm_regmap_init_i2c(client, &ltr390_regmap_config);
	if (IS_ERR(data->regmap))
	return dev_err_probe(dev, PTR_ERR(data->regmap),
	"regmap initialization failed\n");

	data->client = client;
	/* default value of integration time from pg: 15 of the datasheet */
	data->int_time_us = 100000;
	/* default value of gain from pg: 16 of the datasheet */
	data->gain = 3;
	/* default mode for ltr390 is ALS mode */
	data->mode = LTR390_SET_ALS_MODE;

	mutex_init(&data->lock);

	indio_dev->info = &ltr390_info;
	indio_dev->channels = ltr390_channels;
	indio_dev->num_channels = ARRAY_SIZE(ltr390_channels);
	indio_dev->name = "ltr390";

	ret = regmap_read(data->regmap, LTR390_PART_ID, &part_number);
	if (ret)
	return dev_err_probe(dev, ret,
	"failed to get sensor's part id\n");
	/* Lower 4 bits of `part_number` change with hardware revisions */
	if (part_number >> 4 != LTR390_PART_NUMBER_ID)
	dev_info(dev, "received invalid product id: 0x%x", part_number);
	dev_dbg(dev, "LTR390, product id: 0x%x\n", part_number);

	/* reset sensor, chip fails to respond to this, so ignore any errors */
	regmap_set_bits(data->regmap, LTR390_MAIN_CTRL, LTR390_SW_RESET);

	/* Wait for the registers to reset before proceeding */
	usleep_range(1000, 2000);

	ret = regmap_set_bits(data->regmap, LTR390_MAIN_CTRL, LTR390_SENSOR_ENABLE);
	if (ret)
	return dev_err_probe(dev, ret, "failed to enable the sensor\n");

	return devm_iio_device_register(dev, indio_dev);
	}

	static const struct i2c_device_id ltr390_id[] = {
	{ "ltr390" },
	{ /* Sentinel */ }
	};
	MODULE_DEVICE_TABLE(i2c, ltr390_id);

	static const struct of_device_id ltr390_of_table[] = {
	{ .compatible = "liteon,ltr390" },
	{ /* Sentinel */ }
	};
	MODULE_DEVICE_TABLE(of, ltr390_of_table);

	static struct i2c_driver ltr390_driver = {
	.driver = {
	.name = "ltr390",
	.of_match_table = ltr390_of_table,
	},
	.probe = ltr390_probe,
	.id_table = ltr390_id,
	};
	module_i2c_driver(ltr390_driver);

	MODULE_AUTHOR("Anshul Dalal <anshulusr@gmail.com>");
	MODULE_DESCRIPTION("Lite-On LTR390 ALS and UV sensor Driver");
	MODULE_LICENSE("GPL");