drivers/iio/chemical/sen0322.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Driver for the DFRobot SEN0322 oxygen sensor.
 *
 * Datasheet:
 *	https://wiki.dfrobot.com/Gravity_I2C_Oxygen_Sensor_SKU_SEN0322
 *
 * Possible I2C slave addresses:
 *	0x70
 *	0x71
 *	0x72
 *	0x73
 *
 * Copyright (C) 2025 Tóth János <gomba007@gmail.com>
 */

#include <linux/i2c.h>
#include <linux/regmap.h>

#include <linux/iio/iio.h>

#define SEN0322_REG_DATA	0x03
#define SEN0322_REG_COEFF	0x0A

struct sen0322 {
	struct regmap	*regmap;
};

static int sen0322_read_data(struct sen0322 *sen0322)
{
	u8 data[3] = { };
	int ret;

	ret = regmap_bulk_read(sen0322->regmap, SEN0322_REG_DATA, data,
			       sizeof(data));
	if (ret < 0)
		return ret;

	/*
	 * The actual value in the registers is:
	 *	val = data[0] + data[1] / 10 + data[2] / 100
	 * but it is multiplied by 100 here to avoid floating-point math
	 * and the scale is divided by 100 to compensate this.
	 */
	return data[0] * 100 + data[1] * 10 + data[2];
}

static int sen0322_read_scale(struct sen0322 *sen0322, int *num, int *den)
{
	u32 val;
	int ret;

	ret = regmap_read(sen0322->regmap, SEN0322_REG_COEFF, &val);
	if (ret < 0)
		return ret;

	if (val) {
		*num = val;
		*den = 100000;	/* Coeff is scaled by 1000 at calibration. */
	} else { /* The device is not calibrated, using the factory-defaults. */
		*num = 209;	/* Oxygen content in the atmosphere is 20.9%. */
		*den = 120000;	/* Output of the sensor at 20.9% is 120 uA. */
	}

	dev_dbg(regmap_get_device(sen0322->regmap), "scale: %d/%d\n",
		*num, *den);

	return 0;
}

static int sen0322_read_raw(struct iio_dev *iio_dev,
			    const struct iio_chan_spec *chan,
			    int *val, int *val2, long mask)
{
	struct sen0322 *sen0322 = iio_priv(iio_dev);
	int ret;

	if (chan->type != IIO_CONCENTRATION)
		return -EINVAL;

	switch (mask) {
	case IIO_CHAN_INFO_RAW:
		ret = sen0322_read_data(sen0322);
		if (ret < 0)
			return ret;

		*val = ret;
		return IIO_VAL_INT;

	case IIO_CHAN_INFO_SCALE:
		ret = sen0322_read_scale(sen0322, val, val2);
		if (ret < 0)
			return ret;

		return IIO_VAL_FRACTIONAL;

	default:
		return -EINVAL;
	}
}

static const struct iio_info sen0322_info = {
	.read_raw = sen0322_read_raw,
};

static const struct regmap_config sen0322_regmap_conf = {
	.reg_bits = 8,
	.val_bits = 8,
};

static const struct iio_chan_spec sen0322_channel = {
	.type = IIO_CONCENTRATION,
	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
			      BIT(IIO_CHAN_INFO_SCALE),
};

static int sen0322_probe(struct i2c_client *client)
{
	struct sen0322 *sen0322;
	struct iio_dev *iio_dev;

	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
		return -ENODEV;

	iio_dev = devm_iio_device_alloc(&client->dev, sizeof(*sen0322));
	if (!iio_dev)
		return -ENOMEM;

	sen0322 = iio_priv(iio_dev);

	sen0322->regmap = devm_regmap_init_i2c(client, &sen0322_regmap_conf);
	if (IS_ERR(sen0322->regmap))
		return PTR_ERR(sen0322->regmap);

	iio_dev->info = &sen0322_info;
	iio_dev->name = "sen0322";
	iio_dev->channels = &sen0322_channel;
	iio_dev->num_channels = 1;
	iio_dev->modes = INDIO_DIRECT_MODE;

	return devm_iio_device_register(&client->dev, iio_dev);
}

static const struct of_device_id sen0322_of_match[] = {
	{ .compatible = "dfrobot,sen0322" },
	{ }
};
MODULE_DEVICE_TABLE(of, sen0322_of_match);

static struct i2c_driver sen0322_driver = {
	.driver = {
		.name = "sen0322",
		.of_match_table = sen0322_of_match,
	},
	.probe = sen0322_probe,
};
module_i2c_driver(sen0322_driver);

MODULE_AUTHOR("Tóth János <gomba007@gmail.com>");
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("SEN0322 oxygen sensor driver");