iio: chemical: add atlas-ezo-sensor initial support

Add driver for Atlas EZO line of sensors with initial support for
CO2 the sensor. This is effectively ASCII strings proxied over I2C
due to these series of sensors being by default UART.

Signed-off-by: Matt Ranostay <matt.ranostay@konsulko.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/chemical/Kconfig

@@ -22,6 +22,17 @@ config ATLAS_PH_SENSOR
 	  To compile this driver as module, choose M here: the
 	  module will be called atlas-ph-sensor.
 
+config ATLAS_EZO_SENSOR
+	tristate "Atlas Scientific EZO sensors"
+	depends on I2C
+	help
+	  Say Y here to build I2C interface support for the following
+	  Atlas Scientific EZO sensors
+	    * CO2 EZO Sensor
+
+	  To compile this driver as module, choose M here: the
+	  module will be called atlas-ezo-sensor.
+
 config BME680
 	tristate "Bosch Sensortec BME680 sensor driver"
 	depends on (I2C || SPI)

drivers/iio/chemical/Makefile

@@ -5,6 +5,7 @@
 
 # When adding new entries keep the list in alphabetical order
 obj-$(CONFIG_ATLAS_PH_SENSOR)	+= atlas-sensor.o
+obj-$(CONFIG_ATLAS_EZO_SENSOR)	+= atlas-ezo-sensor.o
 obj-$(CONFIG_BME680) += bme680_core.o
 obj-$(CONFIG_BME680_I2C) += bme680_i2c.o
 obj-$(CONFIG_BME680_SPI) += bme680_spi.o

drivers/iio/chemical/atlas-ezo-sensor.c

@@ -0,0 +1,177 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * atlas-ezo-sensor.c - Support for Atlas Scientific EZO sensors
+ *
+ * Copyright (C) 2020 Konsulko Group
+ * Author: Matt Ranostay <matt.ranostay@konsulko.com>
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/delay.h>
+#include <linux/mutex.h>
+#include <linux/err.h>
+#include <linux/i2c.h>
+#include <linux/of_device.h>
+#include <linux/iio/iio.h>
+
+#define ATLAS_EZO_DRV_NAME		"atlas-ezo-sensor"
+#define ATLAS_CO2_INT_TIME_IN_MS	950
+
+enum {
+	ATLAS_CO2_EZO,
+};
+
+struct atlas_ezo_device {
+	const struct iio_chan_spec *channels;
+	int num_channels;
+	int delay;
+};
+
+struct atlas_ezo_data {
+	struct i2c_client *client;
+	struct atlas_ezo_device *chip;
+
+	/* lock to avoid multiple concurrent read calls */
+	struct mutex lock;
+
+	u8 buffer[8];
+};
+
+static const struct iio_chan_spec atlas_co2_ezo_channels[] = {
+	{
+		.type = IIO_CONCENTRATION,
+		.modified = 1,
+		.channel2 = IIO_MOD_CO2,
+		.info_mask_separate =
+			BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE),
+		.scan_index = 0,
+		.scan_type = {
+			.sign = 'u',
+			.realbits = 32,
+			.storagebits = 32,
+			.endianness = IIO_CPU,
+		},
+	},
+};
+
+static struct atlas_ezo_device atlas_ezo_devices[] = {
+	[ATLAS_CO2_EZO] = {
+		.channels = atlas_co2_ezo_channels,
+		.num_channels = 1,
+		.delay = ATLAS_CO2_INT_TIME_IN_MS,
+	},
+};
+
+static int atlas_ezo_read_raw(struct iio_dev *indio_dev,
+			  struct iio_chan_spec const *chan,
+			  int *val, int *val2, long mask)
+{
+	struct atlas_ezo_data *data = iio_priv(indio_dev);
+	struct i2c_client *client = data->client;
+	int ret = 0;
+
+	if (chan->type != IIO_CONCENTRATION)
+		return -EINVAL;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW: {
+		long tmp;
+
+		mutex_lock(&data->lock);
+
+		tmp = i2c_smbus_write_byte(client, 'R');
+
+		if (tmp < 0) {
+			mutex_unlock(&data->lock);
+			return tmp;
+		}
+
+		msleep(data->chip->delay);
+
+		tmp = i2c_master_recv(client, data->buffer, sizeof(data->buffer));
+
+		if (tmp < 0 || data->buffer[0] != 1) {
+			mutex_unlock(&data->lock);
+			return -EBUSY;
+		}
+
+		ret = kstrtol(data->buffer + 1, 10, &tmp);
+
+		*val = tmp;
+
+		mutex_unlock(&data->lock);
+
+		return ret ? ret : IIO_VAL_INT;
+	}
+	case IIO_CHAN_INFO_SCALE:
+		*val = 0;
+		*val2 = 100; /* 0.0001 */
+		return IIO_VAL_INT_PLUS_MICRO;
+	}
+
+	return ret;
+}
+
+static const struct iio_info atlas_info = {
+	.read_raw = atlas_ezo_read_raw,
+};
+
+static const struct i2c_device_id atlas_ezo_id[] = {
+	{ "atlas-co2-ezo", ATLAS_CO2_EZO },
+	{}
+};
+MODULE_DEVICE_TABLE(i2c, atlas_ezo_id);
+
+static const struct of_device_id atlas_ezo_dt_ids[] = {
+	{ .compatible = "atlas,co2-ezo", .data = (void *)ATLAS_CO2_EZO, },
+	{}
+};
+MODULE_DEVICE_TABLE(of, atlas_ezo_dt_ids);
+
+static int atlas_ezo_probe(struct i2c_client *client,
+		       const struct i2c_device_id *id)
+{
+	struct atlas_ezo_data *data;
+	struct atlas_ezo_device *chip;
+	const struct of_device_id *of_id;
+	struct iio_dev *indio_dev;
+
+	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	of_id = of_match_device(atlas_ezo_dt_ids, &client->dev);
+	if (!of_id)
+		chip = &atlas_ezo_devices[id->driver_data];
+	else
+		chip = &atlas_ezo_devices[(unsigned long)of_id->data];
+
+	indio_dev->info = &atlas_info;
+	indio_dev->name = ATLAS_EZO_DRV_NAME;
+	indio_dev->channels = chip->channels;
+	indio_dev->num_channels = chip->num_channels;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->dev.parent = &client->dev;
+
+	data = iio_priv(indio_dev);
+	data->client = client;
+	data->chip = chip;
+	mutex_init(&data->lock);
+
+	return devm_iio_device_register(&client->dev, indio_dev);
+};
+
+static struct i2c_driver atlas_ezo_driver = {
+	.driver = {
+		.name	= ATLAS_EZO_DRV_NAME,
+		.of_match_table	= atlas_ezo_dt_ids,
+	},
+	.probe		= atlas_ezo_probe,
+	.id_table	= atlas_ezo_id,
+};
+module_i2c_driver(atlas_ezo_driver);
+
+MODULE_AUTHOR("Matt Ranostay <matt.ranostay@konsulko.com>");
+MODULE_DESCRIPTION("Atlas Scientific EZO sensors");
+MODULE_LICENSE("GPL");