Initial import

5 files changed, 698 insertions, 0 deletions

diff --git a/drivers/iio/humidity/Kconfig b/drivers/iio/humidity/Kconfig
new file mode 100644
index 000000000..4813b793b
--- /dev/null
+++ b/drivers/iio/humidity/Kconfig
@@ -0,0 +1,35 @@
+#
+# humidity sensor drivers
+#
+menu "Humidity sensors"
+
+config DHT11
+	tristate "DHT11 (and compatible sensors) driver"
+	depends on GPIOLIB
+	help
+	  This driver supports reading data via a single interrupt
+	  generating GPIO line. Currently tested are DHT11 and DHT22.
+	  Other sensors should work as well as long as they speak the
+	  same protocol.
+
+config SI7005
+	tristate "SI7005 relative humidity and temperature sensor"
+	depends on I2C
+	help
+	  Say yes here to build support for the Silabs Si7005 relative
+	  humidity and temperature sensor.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called si7005.
+
+config SI7020
+	tristate "Si7013/20/21 Relative Humidity and Temperature Sensors"
+	depends on I2C
+	help
+	  Say yes here to build support for the Silicon Labs Si7013/20/21
+	  Relative Humidity and Temperature Sensors.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called si7020.
+
+endmenu
diff --git a/drivers/iio/humidity/Makefile b/drivers/iio/humidity/Makefile
new file mode 100644
index 000000000..86e2d26e9
--- /dev/null
+++ b/drivers/iio/humidity/Makefile
@@ -0,0 +1,7 @@
+#
+# Makefile for IIO humidity sensor drivers
+#
+
+obj-$(CONFIG_DHT11) += dht11.o
+obj-$(CONFIG_SI7005) += si7005.o
+obj-$(CONFIG_SI7020) += si7020.o
diff --git a/drivers/iio/humidity/dht11.c b/drivers/iio/humidity/dht11.c
new file mode 100644
index 000000000..7d79a1ac5
--- /dev/null
+++ b/drivers/iio/humidity/dht11.c
@@ -0,0 +1,306 @@
+/*
+ * DHT11/DHT22 bit banging GPIO driver
+ *
+ * Copyright (c) Harald Geyer <harald@ccbib.org>
+ *
+ * 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/err.h>
+#include <linux/interrupt.h>
+#include <linux/device.h>
+#include <linux/kernel.h>
+#include <linux/printk.h>
+#include <linux/slab.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/sysfs.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/wait.h>
+#include <linux/bitops.h>
+#include <linux/completion.h>
+#include <linux/mutex.h>
+#include <linux/delay.h>
+#include <linux/gpio.h>
+#include <linux/of_gpio.h>
+
+#include <linux/iio/iio.h>
+
+#define DRIVER_NAME	"dht11"
+
+#define DHT11_DATA_VALID_TIME	2000000000  /* 2s in ns */
+
+#define DHT11_EDGES_PREAMBLE 2
+#define DHT11_BITS_PER_READ 40
+/*
+ * Note that when reading the sensor actually 84 edges are detected, but
+ * since the last edge is not significant, we only store 83:
+ */
+#define DHT11_EDGES_PER_READ (2*DHT11_BITS_PER_READ + DHT11_EDGES_PREAMBLE + 1)
+
+/* Data transmission timing (nano seconds) */
+#define DHT11_START_TRANSMISSION	18  /* ms */
+#define DHT11_SENSOR_RESPONSE	80000
+#define DHT11_START_BIT		50000
+#define DHT11_DATA_BIT_LOW	27000
+#define DHT11_DATA_BIT_HIGH	70000
+
+struct dht11 {
+	struct device			*dev;
+
+	int				gpio;
+	int				irq;
+
+	struct completion		completion;
+	struct mutex			lock;
+
+	s64				timestamp;
+	int				temperature;
+	int				humidity;
+
+	/* num_edges: -1 means "no transmission in progress" */
+	int				num_edges;
+	struct {s64 ts; int value; }	edges[DHT11_EDGES_PER_READ];
+};
+
+static unsigned char dht11_decode_byte(int *timing, int threshold)
+{
+	unsigned char ret = 0;
+	int i;
+
+	for (i = 0; i < 8; ++i) {
+		ret <<= 1;
+		if (timing[i] >= threshold)
+			++ret;
+	}
+
+	return ret;
+}
+
+static int dht11_decode(struct dht11 *dht11, int offset)
+{
+	int i, t, timing[DHT11_BITS_PER_READ], threshold,
+		timeres = DHT11_SENSOR_RESPONSE;
+	unsigned char temp_int, temp_dec, hum_int, hum_dec, checksum;
+
+	/* Calculate timestamp resolution */
+	for (i = 1; i < dht11->num_edges; ++i) {
+		t = dht11->edges[i].ts - dht11->edges[i-1].ts;
+		if (t > 0 && t < timeres)
+			timeres = t;
+	}
+	if (2*timeres > DHT11_DATA_BIT_HIGH) {
+		pr_err("dht11: timeresolution %d too bad for decoding\n",
+			timeres);
+		return -EIO;
+	}
+	threshold = DHT11_DATA_BIT_HIGH / timeres;
+	if (DHT11_DATA_BIT_LOW/timeres + 1 >= threshold)
+		pr_err("dht11: WARNING: decoding ambiguous\n");
+
+	/* scale down with timeres and check validity */
+	for (i = 0; i < DHT11_BITS_PER_READ; ++i) {
+		t = dht11->edges[offset + 2*i + 2].ts -
+			dht11->edges[offset + 2*i + 1].ts;
+		if (!dht11->edges[offset + 2*i + 1].value)
+			return -EIO;  /* lost synchronisation */
+		timing[i] = t / timeres;
+	}
+
+	hum_int = dht11_decode_byte(timing, threshold);
+	hum_dec = dht11_decode_byte(&timing[8], threshold);
+	temp_int = dht11_decode_byte(&timing[16], threshold);
+	temp_dec = dht11_decode_byte(&timing[24], threshold);
+	checksum = dht11_decode_byte(&timing[32], threshold);
+
+	if (((hum_int + hum_dec + temp_int + temp_dec) & 0xff) != checksum)
+		return -EIO;
+
+	dht11->timestamp = iio_get_time_ns();
+	if (hum_int < 20) {  /* DHT22 */
+		dht11->temperature = (((temp_int & 0x7f) << 8) + temp_dec) *
+					((temp_int & 0x80) ? -100 : 100);
+		dht11->humidity = ((hum_int << 8) + hum_dec) * 100;
+	} else if (temp_dec == 0 && hum_dec == 0) {  /* DHT11 */
+		dht11->temperature = temp_int * 1000;
+		dht11->humidity = hum_int * 1000;
+	} else {
+		dev_err(dht11->dev,
+			"Don't know how to decode data: %d %d %d %d\n",
+			hum_int, hum_dec, temp_int, temp_dec);
+		return -EIO;
+	}
+
+	return 0;
+}
+
+/*
+ * IRQ handler called on GPIO edges
+ */
+static irqreturn_t dht11_handle_irq(int irq, void *data)
+{
+	struct iio_dev *iio = data;
+	struct dht11 *dht11 = iio_priv(iio);
+
+	/* TODO: Consider making the handler safe for IRQ sharing */
+	if (dht11->num_edges < DHT11_EDGES_PER_READ && dht11->num_edges >= 0) {
+		dht11->edges[dht11->num_edges].ts = iio_get_time_ns();
+		dht11->edges[dht11->num_edges++].value =
+						gpio_get_value(dht11->gpio);
+
+		if (dht11->num_edges >= DHT11_EDGES_PER_READ)
+			complete(&dht11->completion);
+	}
+
+	return IRQ_HANDLED;
+}
+
+static int dht11_read_raw(struct iio_dev *iio_dev,
+			const struct iio_chan_spec *chan,
+			int *val, int *val2, long m)
+{
+	struct dht11 *dht11 = iio_priv(iio_dev);
+	int ret;
+
+	mutex_lock(&dht11->lock);
+	if (dht11->timestamp + DHT11_DATA_VALID_TIME < iio_get_time_ns()) {
+		reinit_completion(&dht11->completion);
+
+		dht11->num_edges = 0;
+		ret = gpio_direction_output(dht11->gpio, 0);
+		if (ret)
+			goto err;
+		msleep(DHT11_START_TRANSMISSION);
+		ret = gpio_direction_input(dht11->gpio);
+		if (ret)
+			goto err;
+
+		ret = request_irq(dht11->irq, dht11_handle_irq,
+				  IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING,
+				  iio_dev->name, iio_dev);
+		if (ret)
+			goto err;
+
+		ret = wait_for_completion_killable_timeout(&dht11->completion,
+								 HZ);
+
+		free_irq(dht11->irq, iio_dev);
+
+		if (ret == 0 && dht11->num_edges < DHT11_EDGES_PER_READ - 1) {
+			dev_err(&iio_dev->dev,
+					"Only %d signal edges detected\n",
+					dht11->num_edges);
+			ret = -ETIMEDOUT;
+		}
+		if (ret < 0)
+			goto err;
+
+		ret = dht11_decode(dht11,
+				dht11->num_edges == DHT11_EDGES_PER_READ ?
+					DHT11_EDGES_PREAMBLE :
+					DHT11_EDGES_PREAMBLE - 2);
+		if (ret)
+			goto err;
+	}
+
+	ret = IIO_VAL_INT;
+	if (chan->type == IIO_TEMP)
+		*val = dht11->temperature;
+	else if (chan->type == IIO_HUMIDITYRELATIVE)
+		*val = dht11->humidity;
+	else
+		ret = -EINVAL;
+err:
+	dht11->num_edges = -1;
+	mutex_unlock(&dht11->lock);
+	return ret;
+}
+
+static const struct iio_info dht11_iio_info = {
+	.driver_module		= THIS_MODULE,
+	.read_raw		= dht11_read_raw,
+};
+
+static const struct iio_chan_spec dht11_chan_spec[] = {
+	{ .type = IIO_TEMP,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED), },
+	{ .type = IIO_HUMIDITYRELATIVE,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED), }
+};
+
+static const struct of_device_id dht11_dt_ids[] = {
+	{ .compatible = "dht11", },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, dht11_dt_ids);
+
+static int dht11_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct device_node *node = dev->of_node;
+	struct dht11 *dht11;
+	struct iio_dev *iio;
+	int ret;
+
+	iio = devm_iio_device_alloc(dev, sizeof(*dht11));
+	if (!iio) {
+		dev_err(dev, "Failed to allocate IIO device\n");
+		return -ENOMEM;
+	}
+
+	dht11 = iio_priv(iio);
+	dht11->dev = dev;
+
+	dht11->gpio = ret = of_get_gpio(node, 0);
+	if (ret < 0)
+		return ret;
+	ret = devm_gpio_request_one(dev, dht11->gpio, GPIOF_IN, pdev->name);
+	if (ret)
+		return ret;
+
+	dht11->irq = gpio_to_irq(dht11->gpio);
+	if (dht11->irq < 0) {
+		dev_err(dev, "GPIO %d has no interrupt\n", dht11->gpio);
+		return -EINVAL;
+	}
+
+	dht11->timestamp = iio_get_time_ns() - DHT11_DATA_VALID_TIME - 1;
+	dht11->num_edges = -1;
+
+	platform_set_drvdata(pdev, iio);
+
+	init_completion(&dht11->completion);
+	mutex_init(&dht11->lock);
+	iio->name = pdev->name;
+	iio->dev.parent = &pdev->dev;
+	iio->info = &dht11_iio_info;
+	iio->modes = INDIO_DIRECT_MODE;
+	iio->channels = dht11_chan_spec;
+	iio->num_channels = ARRAY_SIZE(dht11_chan_spec);
+
+	return devm_iio_device_register(dev, iio);
+}
+
+static struct platform_driver dht11_driver = {
+	.driver = {
+		.name	= DRIVER_NAME,
+		.of_match_table = dht11_dt_ids,
+	},
+	.probe  = dht11_probe,
+};
+
+module_platform_driver(dht11_driver);
+
+MODULE_AUTHOR("Harald Geyer <harald@ccbib.org>");
+MODULE_DESCRIPTION("DHT11 humidity/temperature sensor driver");
+MODULE_LICENSE("GPL v2");
diff --git a/drivers/iio/humidity/si7005.c b/drivers/iio/humidity/si7005.c
new file mode 100644
index 000000000..bdd586e6d
--- /dev/null
+++ b/drivers/iio/humidity/si7005.c
@@ -0,0 +1,189 @@
+/*
+ * si7005.c - Support for Silabs Si7005 humidity and temperature sensor
+ *
+ * Copyright (c) 2014 Peter Meerwald <pmeerw@pmeerw.net>
+ *
+ * This file is subject to the terms and conditions of version 2 of
+ * the GNU General Public License.  See the file COPYING in the main
+ * directory of this archive for more details.
+ *
+ * (7-bit I2C slave address 0x40)
+ *
+ * TODO: heater, fast mode, processed mode (temp. / linearity compensation)
+ */
+
+#include <linux/err.h>
+#include <linux/i2c.h>
+#include <linux/delay.h>
+#include <linux/module.h>
+#include <linux/pm.h>
+
+#include <linux/iio/iio.h>
+#include <linux/iio/sysfs.h>
+
+#define SI7005_STATUS 0x00
+#define SI7005_DATA 0x01 /* 16-bit, MSB */
+#define SI7005_CONFIG 0x03
+#define SI7005_ID 0x11
+
+#define SI7005_STATUS_NRDY BIT(0)
+#define SI7005_CONFIG_TEMP BIT(4)
+#define SI7005_CONFIG_START BIT(0)
+
+#define SI7005_ID_7005 0x50
+#define SI7005_ID_7015 0xf0
+
+struct si7005_data {
+	struct i2c_client *client;
+	struct mutex lock;
+	u8 config;
+};
+
+static int si7005_read_measurement(struct si7005_data *data, bool temp)
+{
+	int tries = 50;
+	int ret;
+
+	mutex_lock(&data->lock);
+
+	ret = i2c_smbus_write_byte_data(data->client, SI7005_CONFIG,
+		data->config | SI7005_CONFIG_START |
+		(temp ? SI7005_CONFIG_TEMP : 0));
+	if (ret < 0)
+		goto done;
+
+	while (tries-- > 0) {
+		msleep(20);
+		ret = i2c_smbus_read_byte_data(data->client, SI7005_STATUS);
+		if (ret < 0)
+			goto done;
+		if (!(ret & SI7005_STATUS_NRDY))
+			break;
+	}
+	if (tries < 0) {
+		ret = -EIO;
+		goto done;
+	}
+
+	ret = i2c_smbus_read_word_swapped(data->client, SI7005_DATA);
+
+done:
+	mutex_unlock(&data->lock);
+
+	return ret;
+}
+
+static int si7005_read_raw(struct iio_dev *indio_dev,
+			    struct iio_chan_spec const *chan, int *val,
+			    int *val2, long mask)
+{
+	struct si7005_data *data = iio_priv(indio_dev);
+	int ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		ret = si7005_read_measurement(data, chan->type == IIO_TEMP);
+		if (ret < 0)
+			return ret;
+		*val = ret;
+		return IIO_VAL_INT;
+	case IIO_CHAN_INFO_SCALE:
+		if (chan->type == IIO_TEMP) {
+			*val = 7;
+			*val2 = 812500;
+		} else {
+			*val = 3;
+			*val2 = 906250;
+		}
+		return IIO_VAL_INT_PLUS_MICRO;
+	case IIO_CHAN_INFO_OFFSET:
+		if (chan->type == IIO_TEMP)
+			*val = -50 * 32 * 4;
+		else
+			*val = -24 * 16 * 16;
+		return IIO_VAL_INT;
+	default:
+		break;
+	}
+
+	return -EINVAL;
+}
+
+static const struct iio_chan_spec si7005_channels[] = {
+	{
+		.type = IIO_HUMIDITYRELATIVE,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
+			BIT(IIO_CHAN_INFO_SCALE) | BIT(IIO_CHAN_INFO_OFFSET),
+	},
+	{
+		.type = IIO_TEMP,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
+			BIT(IIO_CHAN_INFO_SCALE) | BIT(IIO_CHAN_INFO_OFFSET),
+	}
+};
+
+static const struct iio_info si7005_info = {
+	.read_raw = si7005_read_raw,
+	.driver_module = THIS_MODULE,
+};
+
+static int si7005_probe(struct i2c_client *client,
+			 const struct i2c_device_id *id)
+{
+	struct iio_dev *indio_dev;
+	struct si7005_data *data;
+	int ret;
+
+	if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_WORD_DATA))
+		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;
+	mutex_init(&data->lock);
+
+	indio_dev->dev.parent = &client->dev;
+	indio_dev->name = dev_name(&client->dev);
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->info = &si7005_info;
+
+	indio_dev->channels = si7005_channels;
+	indio_dev->num_channels = ARRAY_SIZE(si7005_channels);
+
+	ret = i2c_smbus_read_byte_data(client, SI7005_ID);
+	if (ret < 0)
+		return ret;
+	if (ret != SI7005_ID_7005 && ret != SI7005_ID_7015)
+		return -ENODEV;
+
+	ret = i2c_smbus_read_byte_data(client, SI7005_CONFIG);
+	if (ret < 0)
+		return ret;
+	data->config = ret;
+
+	return devm_iio_device_register(&client->dev, indio_dev);
+}
+
+static const struct i2c_device_id si7005_id[] = {
+	{ "si7005", 0 },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, si7005_id);
+
+static struct i2c_driver si7005_driver = {
+	.driver = {
+		.name	= "si7005",
+		.owner	= THIS_MODULE,
+	},
+	.probe = si7005_probe,
+	.id_table = si7005_id,
+};
+module_i2c_driver(si7005_driver);
+
+MODULE_AUTHOR("Peter Meerwald <pmeerw@pmeerw.net>");
+MODULE_DESCRIPTION("Silabs Si7005 humidity and temperature sensor driver");
+MODULE_LICENSE("GPL");
diff --git a/drivers/iio/humidity/si7020.c b/drivers/iio/humidity/si7020.c
new file mode 100644
index 000000000..fa3b809af
--- /dev/null
+++ b/drivers/iio/humidity/si7020.c
@@ -0,0 +1,161 @@
+/*
+ * si7020.c - Silicon Labs Si7013/20/21 Relative Humidity and Temp Sensors
+ * Copyright (c) 2013,2014  Uplogix, Inc.
+ * David Barksdale <dbarksdale@uplogix.com>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * 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.
+ */
+
+/*
+ * The Silicon Labs Si7013/20/21 Relative Humidity and Temperature Sensors
+ * are i2c devices which have an identical programming interface for
+ * measuring relative humidity and temperature. The Si7013 has an additional
+ * temperature input which this driver does not support.
+ *
+ * Data Sheets:
+ *   Si7013: http://www.silabs.com/Support%20Documents/TechnicalDocs/Si7013.pdf
+ *   Si7020: http://www.silabs.com/Support%20Documents/TechnicalDocs/Si7020.pdf
+ *   Si7021: http://www.silabs.com/Support%20Documents/TechnicalDocs/Si7021.pdf
+ */
+
+#include <linux/delay.h>
+#include <linux/i2c.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/sysfs.h>
+
+#include <linux/iio/iio.h>
+#include <linux/iio/sysfs.h>
+
+/* Measure Relative Humidity, Hold Master Mode */
+#define SI7020CMD_RH_HOLD	0xE5
+/* Measure Temperature, Hold Master Mode */
+#define SI7020CMD_TEMP_HOLD	0xE3
+/* Software Reset */
+#define SI7020CMD_RESET		0xFE
+
+static int si7020_read_raw(struct iio_dev *indio_dev,
+			   struct iio_chan_spec const *chan, int *val,
+			   int *val2, long mask)
+{
+	struct i2c_client **client = iio_priv(indio_dev);
+	int ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		ret = i2c_smbus_read_word_data(*client,
+					       chan->type == IIO_TEMP ?
+					       SI7020CMD_TEMP_HOLD :
+					       SI7020CMD_RH_HOLD);
+		if (ret < 0)
+			return ret;
+		*val = ret >> 2;
+		if (chan->type == IIO_HUMIDITYRELATIVE)
+			*val &= GENMASK(11, 0);
+		return IIO_VAL_INT;
+	case IIO_CHAN_INFO_SCALE:
+		if (chan->type == IIO_TEMP)
+			*val = 175720; /* = 175.72 * 1000 */
+		else
+			*val = 125 * 1000;
+		*val2 = 65536 >> 2;
+		return IIO_VAL_FRACTIONAL;
+	case IIO_CHAN_INFO_OFFSET:
+		/*
+		 * Since iio_convert_raw_to_processed_unlocked assumes offset
+		 * is an integer we have to round these values and lose
+		 * accuracy.
+		 * Relative humidity will be 0.0032959% too high and
+		 * temperature will be 0.00277344 degrees too high.
+		 * This is no big deal because it's within the accuracy of the
+		 * sensor.
+		 */
+		if (chan->type == IIO_TEMP)
+			*val = -4368; /* = -46.85 * (65536 >> 2) / 175.72 */
+		else
+			*val = -786; /* = -6 * (65536 >> 2) / 125 */
+		return IIO_VAL_INT;
+	default:
+		break;
+	}
+
+	return -EINVAL;
+}
+
+static const struct iio_chan_spec si7020_channels[] = {
+	{
+		.type = IIO_HUMIDITYRELATIVE,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
+			BIT(IIO_CHAN_INFO_SCALE) | BIT(IIO_CHAN_INFO_OFFSET),
+	},
+	{
+		.type = IIO_TEMP,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
+			BIT(IIO_CHAN_INFO_SCALE) | BIT(IIO_CHAN_INFO_OFFSET),
+	}
+};
+
+static const struct iio_info si7020_info = {
+	.read_raw = si7020_read_raw,
+	.driver_module = THIS_MODULE,
+};
+
+static int si7020_probe(struct i2c_client *client,
+			const struct i2c_device_id *id)
+{
+	struct iio_dev *indio_dev;
+	struct i2c_client **data;
+	int ret;
+
+	if (!i2c_check_functionality(client->adapter,
+				     I2C_FUNC_SMBUS_WRITE_BYTE |
+				     I2C_FUNC_SMBUS_READ_WORD_DATA))
+		return -ENODEV;
+
+	/* Reset device, loads default settings. */
+	ret = i2c_smbus_write_byte(client, SI7020CMD_RESET);
+	if (ret < 0)
+		return ret;
+	/* Wait the maximum power-up time after software reset. */
+	msleep(15);
+
+	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	data = iio_priv(indio_dev);
+	*data = client;
+
+	indio_dev->dev.parent = &client->dev;
+	indio_dev->name = dev_name(&client->dev);
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->info = &si7020_info;
+	indio_dev->channels = si7020_channels;
+	indio_dev->num_channels = ARRAY_SIZE(si7020_channels);
+
+	return devm_iio_device_register(&client->dev, indio_dev);
+}
+
+static const struct i2c_device_id si7020_id[] = {
+	{ "si7020", 0 },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, si7020_id);
+
+static struct i2c_driver si7020_driver = {
+	.driver.name	= "si7020",
+	.probe		= si7020_probe,
+	.id_table	= si7020_id,
+};
+
+module_i2c_driver(si7020_driver);
+MODULE_DESCRIPTION("Silicon Labs Si7013/20/21 Relative Humidity and Temperature Sensors");
+MODULE_AUTHOR("David Barksdale <dbarksdale@uplogix.com>");
+MODULE_LICENSE("GPL");