iio: distance: srf08: add IIO driver for us ranger

This is the IIO driver for devantech srf08 ultrasonic ranger which can be used to measure the distances to an object.

The sensor supports I2C with some registers.

Supported Features include:
- read the distance in ranging mode in centimeters
- output of the driver is directly the read value
- together with the scale the driver delivers the distance in meters
- only the first echo of the nearest object is delivered
- set max gain register; userspace enters analogue value
- set range registers; userspace enters range in millimeters in 43 mm steps

Features not supported by this driver:
- ranging mode in inches or in microseconds
- ANN mode
- change I2C address through this driver
- light sensor

The driver was added in the directory "proximity" of the iio subsystem in absence of another directory named "distance".
There is also a new submenu "distance"

Signed-off-by Andreas Klinger <[email protected]>

---
 drivers/iio/proximity/Kconfig  |  15 ++
 drivers/iio/proximity/Makefile |   1 +
 drivers/iio/proximity/srf08.c  | 345 +++++++++++++++++++++++++++++++++++++++++
 3 files changed, 361 insertions(+)
 create mode 100644 drivers/iio/proximity/srf08.c

drivers/iio/proximity/Kconfig +15 -0

index ef4c73db5b53..7b10a137702b 100644
@@ -46,3 +46,18 @@ config SX9500
 	  module will be called sx9500.
 
 endmenu
+
+menu "Distance sensors"
+
+config SRF08
+	tristate "Devantech SRF08 ultrasonic ranger sensor"
+	depends on I2C
+	help
+	  Say Y here to build a driver for Devantech SRF08 ultrasonic
+	  ranger sensor. This driver can be used to measure the distance
+	  of objects.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called srf08.
+
+endmenu

drivers/iio/proximity/Makefile +0 -0

index 9aadd9a8ee99..14d8fe4e5cae 100644

drivers/iio/proximity/srf08.c new file +18 -0

new file mode 100644
index 000000000000..a888a230b419
@@ -0,0 +1,345 @@
+/*
+ * srf08.c - Support for Devantech SRF08 ultrasonic ranger
+ *
+ * Copyright (c) 2016 Andreas Klinger <[email protected]>
+ *
+ * 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.
+ *
+ * For details about the device see:
+ * http://www.robot-electronics.co.uk/htm/srf08tech.html
+ */
+
+#include <linux/err.h>
+#include <linux/i2c.h>
+#include <linux/delay.h>
+#include <linux/module.h>
+#include <linux/bitops.h>

drivers/iio/proximity/srf08.c new file +11 -0

+#define SRF08_READ_ECHO_1_LOW	0x03	/* range of first echo received */
+
+#define SRF08_CMD_RANGING_CM	0x51	/* Ranging Mode - Result in cm */
+
+struct srf08_data {
+	struct i2c_client	*client;
+	int			gain;			/* max gain */
+	int			range_mm;		/* range in mm */
+	struct mutex		lock;
+};
+

drivers/iio/proximity/srf08.c new file +8 -0

+	int ret, i;
+
+	mutex_lock(&data->lock);
+
+	ret = i2c_smbus_write_byte_data(data->client,
+			SRF08_WRITE_COMMAND, SRF08_CMD_RANGING_CM);
+	if (ret < 0) {
+		dev_err(&client->dev, "write command - err: %d\n", ret);

drivers/iio/proximity/srf08.c new file +5 -0

+			break;
+		msleep(20);
+	}
+
+	if ((ret >= 255) || (ret <= 0)) {

drivers/iio/proximity/srf08.c new file +5 -0

+
+	return len;
+}
+
+static IIO_DEVICE_ATTR(range_mm_available, S_IRUGO,

drivers/iio/proximity/srf08.c new file +56 -0

+	if (ret)
+		return ret;
+
+	regval = val / 43 - 1;
+	mod = val % 43;
+
+	if (mod || (regval < 0) || (regval > 255))
+		return -EINVAL;
+
+	mutex_lock(&data->lock);
+
+	ret = i2c_smbus_write_byte_data(data->client,
+						SRF08_WRITE_RANGE, regval);
+	if (ret < 0) {
+		dev_err(&client->dev, "write_range - err: %d\n", ret);
+		mutex_unlock(&data->lock);
+		return ret;
+	}
+
+	data->range_mm = val;
+
+	mutex_unlock(&data->lock);
+
+	return len;
+}
+
+static IIO_DEVICE_ATTR(range_mm, S_IRUGO | S_IWUSR,
+			srf08_show_range_mm, srf08_write_range_mm, 0);
+
+static ssize_t srf08_show_gain_available(struct device *dev,
+				struct device_attribute *attr, char *buf)
+{
+	int i, len = 0;
+
+	for (i = 0; i < ARRAY_SIZE(srf08_gain); i++)
+		len += sprintf(buf + len, "%d ", srf08_gain[i]);
+
+	len += sprintf(buf + len, "\n");
+
+	return len;
+}
+
+static IIO_DEVICE_ATTR(gain_available, S_IRUGO,
+				srf08_show_gain_available, NULL, 0);
+
+static ssize_t srf08_show_gain(struct device *dev,
+				struct device_attribute *attr, char *buf)
+{
+	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
+	struct srf08_data *data = iio_priv(indio_dev);
+	int len;
+
+	len = sprintf(buf, "%d\n", data->gain);
+
+	return len;
+}

drivers/iio/proximity/srf08.c new file +49 -0

+	if (regval == -1)
+		return -EINVAL;
+
+	mutex_lock(&data->lock);
+
+	ret = i2c_smbus_write_byte_data(data->client,
+						SRF08_WRITE_MAX_GAIN, regval);
+	if (ret < 0) {
+		dev_err(&client->dev, "write_gain - err: %d\n", ret);
+		mutex_unlock(&data->lock);
+		return ret;
+	}
+
+	data->gain = val;
+
+	mutex_unlock(&data->lock);
+
+	return len;
+}
+
+static IIO_DEVICE_ATTR(gain, S_IRUGO | S_IWUSR,
+					srf08_show_gain, srf08_write_gain, 0);
+
+static struct attribute *srf08_attributes[] = {
+	&iio_dev_attr_range_mm.dev_attr.attr,
+	&iio_dev_attr_range_mm_available.dev_attr.attr,
+	&iio_dev_attr_gain.dev_attr.attr,
+	&iio_dev_attr_gain_available.dev_attr.attr,
+	NULL,
+};
+
+static const struct attribute_group srf08_attribute_group = {
+	.attrs = srf08_attributes,
+};
+
+static const struct iio_chan_spec srf08_channels[] = {
+	{
+		.type = IIO_DISTANCE,
+		.info_mask_separate =
+				BIT(IIO_CHAN_INFO_RAW) |
+				BIT(IIO_CHAN_INFO_SCALE),
+	},
+};
+
+static const struct iio_info srf08_info = {
+	.read_raw = srf08_read_raw,
+	.attrs = &srf08_attribute_group,
+	.driver_module = THIS_MODULE,
+};

drivers/iio/proximity/srf08.c new file +32 -0

+	data->range_mm = 11008;
+
+	indio_dev->name = dev_name(&client->dev);
+	indio_dev->dev.parent = &client->dev;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->info = &srf08_info;
+	indio_dev->channels = srf08_channels;
+	indio_dev->num_channels = ARRAY_SIZE(srf08_channels);
+
+	mutex_init(&data->lock);
+
+	return devm_iio_device_register(&client->dev, indio_dev);
+}
+
+static const struct i2c_device_id srf08_id[] = {
+	{ "srf08", 0 },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, srf08_id);
+
+static struct i2c_driver srf08_driver = {
+	.driver = {
+		.name	= "srf08",
+	},
+	.probe = srf08_probe,
+	.id_table = srf08_id,
+};
+module_i2c_driver(srf08_driver);
+
+MODULE_AUTHOR("Andreas Klinger <[email protected]>");
+MODULE_DESCRIPTION("Devantech SRF08 ultrasonic ranger driver");
+MODULE_LICENSE("GPL");