iio: chemical: add SGX VZ89x VOC sensor support

Add support for VZ89X sensors VOC and CO2 reporting channels in
percentage which can be converted to part per million.
Signed-off-by: Matt Ranostay <mranostay@gmail.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

Documentation/ABI/testing/sysfs-bus-iio-chemical-vz89x

+What:		/sys/bus/iio/devices/iio:deviceX/in_concentration_VOC_short_raw
+Date:		September 2015
+KernelVersion:	4.3
+Contact:	Matt Ranostay <mranostay@gmail.com>
+Description:
+		Get the raw calibration VOC value from the sensor.
+		This value has little application outside of calibration.

Documentation/devicetree/bindings/i2c/trivial-devices.txt

@@ -88,6 +88,7 @@ ricoh,rs5c372b		I2C bus SERIAL INTERFACE REAL-TIME CLOCK IC
 ricoh,rv5c386		I2C bus SERIAL INTERFACE REAL-TIME CLOCK IC
 ricoh,rv5c387a		I2C bus SERIAL INTERFACE REAL-TIME CLOCK IC
 samsung,24ad0xd1	S524AD0XF1 (128K/256K-bit Serial EEPROM for Low Power)
+sgx,vz89x		SGX Sensortech VZ89X Sensors
 sii,s35390a		2-wire CMOS real-time clock
 skyworks,sky81452	Skyworks SKY81452: Six-Channel White LED Driver with Touch Panel Bias Supply
 st-micro,24c256		i2c serial eeprom  (24cxx)

drivers/iio/Kconfig

@@ -47,6 +47,7 @@ config IIO_TRIGGERED_EVENT
 source "drivers/iio/accel/Kconfig"
 source "drivers/iio/adc/Kconfig"
 source "drivers/iio/amplifiers/Kconfig"
+source "drivers/iio/chemical/Kconfig"
 source "drivers/iio/common/Kconfig"
 source "drivers/iio/dac/Kconfig"
 source "drivers/iio/frequency/Kconfig"

drivers/iio/Makefile

@@ -13,6 +13,7 @@ obj-y += accel/
 obj-y += adc/
 obj-y += amplifiers/
 obj-y += buffer/
+obj-y += chemical/
 obj-y += common/
 obj-y += dac/
 obj-y += gyro/

drivers/iio/chemical/Kconfig

+#
+# Chemical sensors
+#
+
+menu "Chemical Sensors"
+
+config VZ89X
+	tristate "SGX Sensortech MiCS VZ89X VOC sensor"
+	depends on I2C
+	help
+	  Say Y here to build I2C interface support for the SGX
+	  Sensortech MiCS VZ89X VOC (Volatile Organic Compounds)
+	  sensors
+
+endmenu

drivers/iio/chemical/Makefile

+#
+# Makefile for IIO chemical sensors
+#
+
+# When adding new entries keep the list in alphabetical order
+obj-$(CONFIG_VZ89X)		+= vz89x.o

drivers/iio/chemical/vz89x.c

+/*
+ * vz89x.c - Support for SGX Sensortech MiCS VZ89X VOC sensors
+ *
+ * Copyright (C) 2015 Matt Ranostay <mranostay@gmail.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/init.h>
+#include <linux/i2c.h>
+
+#include <linux/iio/iio.h>
+#include <linux/iio/sysfs.h>
+
+#define VZ89X_REG_MEASUREMENT		0x09
+#define VZ89X_REG_MEASUREMENT_SIZE	6
+
+#define VZ89X_VOC_CO2_IDX		0
+#define VZ89X_VOC_SHORT_IDX		1
+#define VZ89X_VOC_TVOC_IDX		2
+#define VZ89X_VOC_RESISTANCE_IDX	3
+
+struct vz89x_data {
+	struct i2c_client *client;
+	struct mutex lock;
+	unsigned long last_update;
+
+	u8 buffer[VZ89X_REG_MEASUREMENT_SIZE];
+};
+
+static const struct iio_chan_spec vz89x_channels[] = {
+	{
+		.type = IIO_CONCENTRATION,
+		.channel2 = IIO_MOD_CO2,
+		.modified = 1,
+		.info_mask_separate =
+			BIT(IIO_CHAN_INFO_OFFSET) | BIT(IIO_CHAN_INFO_RAW),
+		.address = VZ89X_VOC_CO2_IDX,
+	},
+	{
+		.type = IIO_CONCENTRATION,
+		.channel2 = IIO_MOD_VOC,
+		.modified = 1,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
+		.address = VZ89X_VOC_SHORT_IDX,
+		.extend_name = "short",
+	},
+	{
+		.type = IIO_CONCENTRATION,
+		.channel2 = IIO_MOD_VOC,
+		.modified = 1,
+		.info_mask_separate =
+			BIT(IIO_CHAN_INFO_OFFSET) | BIT(IIO_CHAN_INFO_RAW),
+		.address = VZ89X_VOC_TVOC_IDX,
+	},
+	{
+		.type = IIO_RESISTANCE,
+		.info_mask_separate =
+			BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE),
+		.address = VZ89X_VOC_RESISTANCE_IDX,
+	},
+};
+
+static IIO_CONST_ATTR(in_concentration_co2_scale, "0.00000698689");
+static IIO_CONST_ATTR(in_concentration_voc_scale, "0.00000000436681223");
+
+static struct attribute *vz89x_attributes[] = {
+	&iio_const_attr_in_concentration_co2_scale.dev_attr.attr,
+	&iio_const_attr_in_concentration_voc_scale.dev_attr.attr,
+	NULL,
+};
+
+static const struct attribute_group vz89x_attrs_group = {
+	.attrs = vz89x_attributes,
+};
+
+static int vz89x_get_measurement(struct vz89x_data *data)
+{
+	int ret;
+	int i;
+
+	/* sensor can only be polled once a second max per datasheet */
+	if (!time_after(jiffies, data->last_update + HZ))
+		return 0;
+
+	ret = i2c_smbus_write_word_data(data->client,
+					VZ89X_REG_MEASUREMENT, 0);
+	if (ret < 0)
+		return ret;
+
+	for (i = 0; i < VZ89X_REG_MEASUREMENT_SIZE; i++) {
+		ret = i2c_smbus_read_byte(data->client);
+		if (ret < 0)
+			return ret;
+		data->buffer[i] = ret;
+	}
+
+	data->last_update = jiffies;
+
+	return 0;
+}
+
+static int vz89x_get_resistance_reading(struct vz89x_data *data)
+{
+	u8 *buf = &data->buffer[VZ89X_VOC_TVOC_IDX];
+
+	return buf[0] | (buf[1] << 8) | (buf[2] << 16);
+}
+
+static int vz89x_read_raw(struct iio_dev *indio_dev,
+			  struct iio_chan_spec const *chan, int *val,
+			  int *val2, long mask)
+{
+	struct vz89x_data *data = iio_priv(indio_dev);
+	int ret = -EINVAL;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		mutex_lock(&data->lock);
+		ret = vz89x_get_measurement(data);
+		mutex_unlock(&data->lock);
+
+		if (ret)
+			return ret;
+
+		switch (chan->address) {
+		case VZ89X_VOC_CO2_IDX:
+		case VZ89X_VOC_SHORT_IDX:
+		case VZ89X_VOC_TVOC_IDX:
+			*val = data->buffer[chan->address];
+			return IIO_VAL_INT;
+		case VZ89X_VOC_RESISTANCE_IDX:
+			*val = vz89x_get_resistance_reading(data);
+			return IIO_VAL_INT;
+		default:
+			return -EINVAL;
+		}
+		break;
+	case IIO_CHAN_INFO_SCALE:
+		switch (chan->type) {
+		case IIO_RESISTANCE:
+			*val = 10;
+			return IIO_VAL_INT;
+		default:
+			return -EINVAL;
+		}
+		break;
+	case IIO_CHAN_INFO_OFFSET:
+		switch (chan->address) {
+		case VZ89X_VOC_CO2_IDX:
+			*val = 44;
+			*val2 = 250000;
+			return IIO_VAL_INT_PLUS_MICRO;
+		case VZ89X_VOC_TVOC_IDX:
+			*val = -13;
+			return IIO_VAL_INT;
+		default:
+			return -EINVAL;
+		}
+	}
+
+	return ret;
+}
+
+static const struct iio_info vz89x_info = {
+	.attrs		= &vz89x_attrs_group,
+	.read_raw	= vz89x_read_raw,
+	.driver_module	= THIS_MODULE,
+};
+
+static int vz89x_probe(struct i2c_client *client,
+		       const struct i2c_device_id *id)
+{
+	struct iio_dev *indio_dev;
+	struct vz89x_data *data;
+
+	if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_WORD_DATA |
+				     I2C_FUNC_SMBUS_BYTE))
+		return -ENODEV;
+
+	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	data = iio_priv(indio_dev);
+	i2c_set_clientdata(client, indio_dev);
+	data->client = client;
+	data->last_update = jiffies - HZ;
+	mutex_init(&data->lock);
+
+	indio_dev->dev.parent = &client->dev;
+	indio_dev->info = &vz89x_info,
+	indio_dev->name = dev_name(&client->dev);
+	indio_dev->modes = INDIO_DIRECT_MODE;
+
+	indio_dev->channels = vz89x_channels;
+	indio_dev->num_channels = ARRAY_SIZE(vz89x_channels);
+
+	return devm_iio_device_register(&client->dev, indio_dev);
+}
+
+static const struct i2c_device_id vz89x_id[] = {
+	{ "vz89x", 0 },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, vz89x_id);
+
+static const struct of_device_id vz89x_dt_ids[] = {
+	{ .compatible = "sgx,vz89x" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, vz89x_dt_ids);
+
+static struct i2c_driver vz89x_driver = {
+	.driver = {
+		.name	= "vz89x",
+		.of_match_table = of_match_ptr(vz89x_dt_ids),
+	},
+	.probe = vz89x_probe,
+	.id_table = vz89x_id,
+};
+module_i2c_driver(vz89x_driver);
+
+MODULE_AUTHOR("Matt Ranostay <mranostay@gmail.com>");
+MODULE_DESCRIPTION("SGX Sensortech MiCS VZ89X VOC sensors");
+MODULE_LICENSE("GPL v2");