diff --git a/drivers/iio/proximity/srf04.c b/drivers/iio/proximity/srf04.c
new file mode 100644
index 0000000..e37667f
--- /dev/null
+++ b/drivers/iio/proximity/srf04.c
@@ -0,0 +1,304 @@
+/*
+ * SRF04: ultrasonic sensor for distance measuring by using GPIOs
+ *
+ * Copyright (c) 2017 Andreas Klinger <ak@it-klinger.de>
+ *
+ * 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.
+ *
+ * For details about the device see:
+ * http://www.robot-electronics.co.uk/htm/srf04tech.htm
+ *
+ * the measurement cycle as timing diagram looks like:
+ *
+ *          +---+
+ * GPIO     |   |
+ * trig:  --+   +------------------------------------------------------
+ *          ^   ^
+ *          |<->|
+ *         udelay(10)
+ *
+ * ultra           +-+ +-+ +-+
+ * sonic           | | | | | |
+ * burst: ---------+ +-+ +-+ +-----------------------------------------
+ *                           .
+ * ultra                     .              +-+ +-+ +-+
+ * sonic                     .              | | | | | |
+ * echo:  ----------------------------------+ +-+ +-+ +----------------
+ *                           .                        .
+ *                           +------------------------+
+ * GPIO                      |                        |
+ * echo:  -------------------+                        +---------------
+ *                           ^                        ^
+ *                           interrupt                interrupt
+ *                           (ts_rising)              (ts_falling)
+ *                           |<---------------------->|
+ *                              pulse time measured
+ *                              --> one round trip of ultra sonic waves
+ */
+#include <linux/err.h>
+#include <linux/gpio/consumer.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/property.h>
+#include <linux/sched.h>
+#include <linux/interrupt.h>
+#include <linux/delay.h>
+#include <linux/iio/iio.h>
+#include <linux/iio/sysfs.h>
+
+struct srf04_data {
+	struct device		*dev;
+	struct gpio_desc	*gpiod_trig;
+	struct gpio_desc	*gpiod_echo;
+	struct mutex		lock;
+	int			irqnr;
+	ktime_t			ts_rising;
+	ktime_t			ts_falling;
+	struct completion	rising;
+	struct completion	falling;
+};
+
+static irqreturn_t srf04_handle_irq(int irq, void *dev_id)
+{
+	struct iio_dev *indio_dev = dev_id;
+	struct srf04_data *data = iio_priv(indio_dev);
+	ktime_t now = ktime_get();
+
+	if (gpiod_get_value(data->gpiod_echo)) {
+		data->ts_rising = now;
+		complete(&data->rising);
+	} else {
+		data->ts_falling = now;
+		complete(&data->falling);
+	}
+
+	return IRQ_HANDLED;
+}
+
+static int srf04_read(struct srf04_data *data)
+{
+	int ret;
+	ktime_t ktime_dt;
+	u64 dt_ns;
+	u32 time_ns, distance_mm;
+
+	/*
+	 * just one read-echo-cycle can take place at a time
+	 * ==> lock against concurrent reading calls
+	 */
+	mutex_lock(&data->lock);
+
+	reinit_completion(&data->rising);
+	reinit_completion(&data->falling);
+
+	gpiod_set_value(data->gpiod_trig, 1);
+	udelay(10);
+	gpiod_set_value(data->gpiod_trig, 0);
+
+	/* it cannot take more than 20 ms */
+	ret = wait_for_completion_killable_timeout(&data->rising, HZ/50);
+	if (ret < 0) {
+		mutex_unlock(&data->lock);
+		return ret;
+	} else if (ret == 0) {
+		mutex_unlock(&data->lock);
+		return -ETIMEDOUT;
+	}
+
+	ret = wait_for_completion_killable_timeout(&data->falling, HZ/50);
+	if (ret < 0) {
+		mutex_unlock(&data->lock);
+		return ret;
+	} else if (ret == 0) {
+		mutex_unlock(&data->lock);
+		return -ETIMEDOUT;
+	}
+
+	ktime_dt = ktime_sub(data->ts_falling, data->ts_rising);
+
+	mutex_unlock(&data->lock);
+
+	dt_ns = ktime_to_ns(ktime_dt);
+	/*
+	 * measuring more than 3 meters is beyond the capabilities of
+	 * the sensor
+	 * ==> filter out invalid results for not measuring echos of
+	 *     another us sensor
+	 *
+	 * formula:
+	 *         distance       3 m
+	 * time = ---------- = --------- = 9404389 ns
+	 *          speed       319 m/s
+	 *
+	 * using a minimum speed at -20 °C of 319 m/s
+	 */
+	if (dt_ns > 9404389)
+		return -EIO;
+
+	time_ns = dt_ns;
+
+	/*
+	 * the speed as function of the temperature is approximately:
+	 *
+	 * speed = 331,5 + 0,6 * Temp
+	 *   with Temp in °C
+	 *   and speed in m/s
+	 *
+	 * use 343 m/s as ultrasonic speed at 20 °C here in absence of the
+	 * temperature
+	 *
+	 * therefore:
+	 *             time     343
+	 * distance = ------ * -----
+	 *             10^6       2
+	 *   with time in ns
+	 *   and distance in mm (one way)
+	 *
+	 * because we limit to 3 meters the multiplication with 343 just
+	 * fits into 32 bit
+	 */
+	distance_mm = time_ns * 343 / 2000000;
+
+	return distance_mm;
+}
+
+static int srf04_read_raw(struct iio_dev *indio_dev,
+			    struct iio_chan_spec const *channel, int *val,
+			    int *val2, long info)
+{
+	struct srf04_data *data = iio_priv(indio_dev);
+	int ret;
+
+	if (channel->type != IIO_DISTANCE)
+		return -EINVAL;
+
+	switch (info) {
+	case IIO_CHAN_INFO_RAW:
+		ret = srf04_read(data);
+		if (ret < 0)
+			return ret;
+		*val = ret;
+		return IIO_VAL_INT;
+	case IIO_CHAN_INFO_SCALE:
+		/*
+		 * theoretical maximum resolution is 3 mm
+		 * 1 LSB is 1 mm
+		 */
+		*val = 0;
+		*val2 = 1000;
+		return IIO_VAL_INT_PLUS_MICRO;
+	default:
+		return -EINVAL;
+	}
+}
+
+static const struct iio_info srf04_iio_info = {
+	.driver_module		= THIS_MODULE,
+	.read_raw		= srf04_read_raw,
+};
+
+static const struct iio_chan_spec srf04_chan_spec[] = {
+	{
+		.type = IIO_DISTANCE,
+		.info_mask_separate =
+				BIT(IIO_CHAN_INFO_RAW) |
+				BIT(IIO_CHAN_INFO_SCALE),
+	},
+};
+
+static int srf04_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct srf04_data *data;
+	struct iio_dev *indio_dev;
+	int ret;
+
+	indio_dev = devm_iio_device_alloc(dev, sizeof(struct srf04_data));
+	if (!indio_dev) {
+		dev_err(dev, "failed to allocate IIO device\n");
+		return -ENOMEM;
+	}
+
+	data = iio_priv(indio_dev);
+	data->dev = dev;
+
+	mutex_init(&data->lock);
+	init_completion(&data->rising);
+	init_completion(&data->falling);
+
+	data->gpiod_trig = devm_gpiod_get(dev, "trig", GPIOD_OUT_LOW);
+	if (IS_ERR(data->gpiod_trig)) {
+		dev_err(dev, "failed to get trig-gpios: err=%ld\n",
+					PTR_ERR(data->gpiod_trig));
+		return PTR_ERR(data->gpiod_trig);
+	}
+
+	data->gpiod_echo = devm_gpiod_get(dev, "echo", GPIOD_IN);
+	if (IS_ERR(data->gpiod_echo)) {
+		dev_err(dev, "failed to get echo-gpios: err=%ld\n",
+					PTR_ERR(data->gpiod_echo));
+		return PTR_ERR(data->gpiod_echo);
+	}
+
+	if (gpiod_cansleep(data->gpiod_echo)) {
+		dev_err(data->dev, "cansleep-GPIOs not supported\n");
+		return -ENODEV;
+	}
+
+	data->irqnr = gpiod_to_irq(data->gpiod_echo);
+	if (data->irqnr < 0) {
+		dev_err(data->dev, "gpiod_to_irq: %d\n", data->irqnr);
+		return data->irqnr;
+	}
+
+	ret = devm_request_irq(dev, data->irqnr, srf04_handle_irq,
+			IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING,
+			pdev->name, indio_dev);
+	if (ret < 0) {
+		dev_err(data->dev, "request_irq: %d\n", ret);
+		return ret;
+	}
+
+	platform_set_drvdata(pdev, indio_dev);
+
+	indio_dev->name = "srf04";
+	indio_dev->dev.parent = &pdev->dev;
+	indio_dev->info = &srf04_iio_info;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->channels = srf04_chan_spec;
+	indio_dev->num_channels = ARRAY_SIZE(srf04_chan_spec);
+
+	return devm_iio_device_register(dev, indio_dev);
+}
+
+static const struct of_device_id of_srf04_match[] = {
+	{ .compatible = "devantech,srf04", },
+	{},
+};
+
+MODULE_DEVICE_TABLE(of, of_srf04_match);
+
+static struct platform_driver srf04_driver = {
+	.probe		= srf04_probe,
+	.driver		= {
+		.name		= "srf04-gpio",
+		.of_match_table	= of_srf04_match,
+	},
+};
+
+module_platform_driver(srf04_driver);
+
+MODULE_AUTHOR("Andreas Klinger <ak@it-klinger.de>");
+MODULE_DESCRIPTION("SRF04 ultrasonic sensor for distance measuring using GPIOs");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:srf04");