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 sensitivity as analog value in the range of 0-31  means setting
   gain register on device
 - set range registers; userspace enters max. 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 and
the menu in den config is now called "Proximity and distance sensors"

Signed-off-by: Andreas Klinger <ak@it-klinger.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/proximity/Kconfig

@@ -18,7 +18,7 @@ config AS3935
 
 endmenu
 
-menu "Proximity sensors"
+menu "Proximity and distance sensors"
 
 config LIDAR_LITE_V2
 	tristate "PulsedLight LIDAR sensor"
@@ -45,4 +45,15 @@ config SX9500
 	  To compile this driver as a module, choose M here: the
 	  module will be called sx9500.
 
+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

@@ -5,4 +5,5 @@
 # When adding new entries keep the list in alphabetical order
 obj-$(CONFIG_AS3935)		+= as3935.o
 obj-$(CONFIG_LIDAR_LITE_V2)	+= pulsedlight-lidar-lite-v2.o
+obj-$(CONFIG_SRF08)		+= srf08.o
 obj-$(CONFIG_SX9500)		+= sx9500.o

drivers/iio/proximity/srf08.c

@@ -0,0 +1,398 @@
+/*
+ * srf08.c - Support for Devantech SRF08 ultrasonic ranger
+ *
+ * Copyright (c) 2016 Andreas Klinger <ak@it-klinger.de>
+ *
+ * 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>
+#include <linux/iio/iio.h>
+#include <linux/iio/sysfs.h>
+
+/* registers of SRF08 device */
+#define SRF08_WRITE_COMMAND	0x00	/* Command Register */
+#define SRF08_WRITE_MAX_GAIN	0x01	/* Max Gain Register: 0 .. 31 */
+#define SRF08_WRITE_RANGE	0x02	/* Range Register: 0 .. 255 */
+#define SRF08_READ_SW_REVISION	0x00	/* Software Revision */
+#define SRF08_READ_LIGHT	0x01	/* Light Sensor during last echo */
+#define SRF08_READ_ECHO_1_HIGH	0x02	/* Range of first echo received */
+#define SRF08_READ_ECHO_1_LOW	0x03	/* Range of first echo received */
+
+#define SRF08_CMD_RANGING_CM	0x51	/* Ranging Mode - Result in cm */
+
+#define SRF08_DEFAULT_GAIN	1025	/* default analogue value of Gain */
+#define SRF08_DEFAULT_RANGE	6020	/* default value of Range in mm */
+
+struct srf08_data {
+	struct i2c_client	*client;
+	int			sensitivity;		/* Gain */
+	int			range_mm;		/* max. Range in mm */
+	struct mutex		lock;
+};
+
+/*
+ * in the documentation one can read about the "Gain" of the device
+ * which is used here for amplifying the signal and filtering out unwanted
+ * ones.
+ * But with ADC's this term is already used differently and that's why it
+ * is called "Sensitivity" here.
+ */
+static const int srf08_sensitivity[] = {
+	 94,  97, 100, 103, 107, 110, 114, 118,
+	123, 128, 133, 139, 145, 152, 159, 168,
+	177, 187, 199, 212, 227, 245, 265, 288,
+	317, 352, 395, 450, 524, 626, 777, 1025 };
+
+static int srf08_read_ranging(struct srf08_data *data)
+{
+	struct i2c_client *client = data->client;
+	int ret, i;
+	int waittime;
+
+	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);
+		mutex_unlock(&data->lock);
+		return ret;
+	}
+
+	/*
+	 * we read here until a correct version number shows up as
+	 * suggested by the documentation
+	 *
+	 * with an ultrasonic speed of 343 m/s and a roundtrip of it
+	 * sleep the expected duration and try to read from the device
+	 * if nothing useful is read try it in a shorter grid
+	 *
+	 * polling for not more than 20 ms should be enough
+	 */
+	waittime = 1 + data->range_mm / 172;
+	msleep(waittime);
+	for (i = 0; i < 4; i++) {
+		ret = i2c_smbus_read_byte_data(data->client,
+						SRF08_READ_SW_REVISION);
+
+		/* check if a valid version number is read */
+		if (ret < 255 && ret > 0)
+			break;
+		msleep(5);
+	}
+
+	if (ret >= 255 || ret <= 0) {
+		dev_err(&client->dev, "device not ready\n");
+		mutex_unlock(&data->lock);
+		return -EIO;
+	}
+
+	ret = i2c_smbus_read_word_swapped(data->client,
+						SRF08_READ_ECHO_1_HIGH);
+	if (ret < 0) {
+		dev_err(&client->dev, "cannot read distance: ret=%d\n", ret);
+		mutex_unlock(&data->lock);
+		return ret;
+	}
+
+	mutex_unlock(&data->lock);
+
+	return ret;
+}
+
+static int srf08_read_raw(struct iio_dev *indio_dev,
+			    struct iio_chan_spec const *channel, int *val,
+			    int *val2, long mask)
+{
+	struct srf08_data *data = iio_priv(indio_dev);
+	int ret;
+
+	if (channel->type != IIO_DISTANCE)
+		return -EINVAL;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		ret = srf08_read_ranging(data);
+		if (ret < 0)
+			return ret;
+		*val = ret;
+		return IIO_VAL_INT;
+	case IIO_CHAN_INFO_SCALE:
+		/* 1 LSB is 1 cm */
+		*val = 0;
+		*val2 = 10000;
+		return IIO_VAL_INT_PLUS_MICRO;
+	default:
+		return -EINVAL;
+	}
+}
+
+static ssize_t srf08_show_range_mm_available(struct device *dev,
+				struct device_attribute *attr, char *buf)
+{
+	return sprintf(buf, "[0.043 0.043 11.008]\n");
+}
+
+static IIO_DEVICE_ATTR(sensor_max_range_available, S_IRUGO,
+				srf08_show_range_mm_available, NULL, 0);
+
+static ssize_t srf08_show_range_mm(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);
+
+	return sprintf(buf, "%d.%03d\n", data->range_mm / 1000,
+						data->range_mm % 1000);
+}
+
+/*
+ * set the range of the sensor to an even multiple of 43 mm
+ * which corresponds to 1 LSB in the register
+ *
+ * register value    corresponding range
+ *         0x00             43 mm
+ *         0x01             86 mm
+ *         0x02            129 mm
+ *         ...
+ *         0xFF          11008 mm
+ */
+static ssize_t srf08_write_range_mm(struct srf08_data *data, unsigned int val)
+{
+	int ret;
+	struct i2c_client *client = data->client;
+	unsigned int mod;
+	u8 regval;
+
+	ret = val / 43 - 1;
+	mod = val % 43;
+
+	if (mod || (ret < 0) || (ret > 255))
+		return -EINVAL;
+
+	regval = ret;
+
+	mutex_lock(&data->lock);
+
+	ret = i2c_smbus_write_byte_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 0;
+}
+
+static ssize_t srf08_store_range_mm(struct device *dev,
+					struct device_attribute *attr,
+					const char *buf, size_t len)
+{
+	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
+	struct srf08_data *data = iio_priv(indio_dev);
+	int ret;
+	int integer, fract;
+
+	ret = iio_str_to_fixpoint(buf, 100, &integer, &fract);
+	if (ret)
+		return ret;
+
+	ret = srf08_write_range_mm(data, integer * 1000 + fract);
+	if (ret < 0)
+		return ret;
+
+	return len;
+}
+
+static IIO_DEVICE_ATTR(sensor_max_range, S_IRUGO | S_IWUSR,
+			srf08_show_range_mm, srf08_store_range_mm, 0);
+
+static ssize_t srf08_show_sensitivity_available(struct device *dev,
+				struct device_attribute *attr, char *buf)
+{
+	int i, len = 0;
+
+	for (i = 0; i < ARRAY_SIZE(srf08_sensitivity); i++)
+		len += sprintf(buf + len, "%d ", srf08_sensitivity[i]);
+
+	len += sprintf(buf + len, "\n");
+
+	return len;
+}
+
+static IIO_DEVICE_ATTR(sensor_sensitivity_available, S_IRUGO,
+				srf08_show_sensitivity_available, NULL, 0);
+
+static ssize_t srf08_show_sensitivity(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->sensitivity);
+
+	return len;
+}
+
+static ssize_t srf08_write_sensitivity(struct srf08_data *data,
+							unsigned int val)
+{
+	struct i2c_client *client = data->client;
+	int ret, i;
+	u8 regval;
+
+	for (i = 0; i < ARRAY_SIZE(srf08_sensitivity); i++)
+		if (val == srf08_sensitivity[i]) {
+			regval = i;
+			break;
+		}
+
+	if (i >= ARRAY_SIZE(srf08_sensitivity))
+		return -EINVAL;
+
+	mutex_lock(&data->lock);
+
+	ret = i2c_smbus_write_byte_data(client,
+						SRF08_WRITE_MAX_GAIN, regval);
+	if (ret < 0) {
+		dev_err(&client->dev, "write_sensitivity - err: %d\n", ret);
+		mutex_unlock(&data->lock);
+		return ret;
+	}
+
+	data->sensitivity = val;
+
+	mutex_unlock(&data->lock);
+
+	return 0;
+}
+
+static ssize_t srf08_store_sensitivity(struct device *dev,
+						struct device_attribute *attr,
+						const char *buf, size_t len)
+{
+	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
+	struct srf08_data *data = iio_priv(indio_dev);
+	int ret;
+	unsigned int val;
+
+	ret = kstrtouint(buf, 10, &val);
+	if (ret)
+		return ret;
+
+	ret = srf08_write_sensitivity(data, val);
+	if (ret < 0)
+		return ret;
+
+	return len;
+}
+
+static IIO_DEVICE_ATTR(sensor_sensitivity, S_IRUGO | S_IWUSR,
+			srf08_show_sensitivity, srf08_store_sensitivity, 0);
+
+static struct attribute *srf08_attributes[] = {
+	&iio_dev_attr_sensor_max_range.dev_attr.attr,
+	&iio_dev_attr_sensor_max_range_available.dev_attr.attr,
+	&iio_dev_attr_sensor_sensitivity.dev_attr.attr,
+	&iio_dev_attr_sensor_sensitivity_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,
+};
+
+static int srf08_probe(struct i2c_client *client,
+					 const struct i2c_device_id *id)
+{
+	struct iio_dev *indio_dev;
+	struct srf08_data *data;
+	int ret;
+
+	if (!i2c_check_functionality(client->adapter,
+					I2C_FUNC_SMBUS_READ_BYTE_DATA |
+					I2C_FUNC_SMBUS_WRITE_BYTE_DATA |
+					I2C_FUNC_SMBUS_READ_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;
+
+	indio_dev->name = "srf08";
+	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);
+
+	/*
+	 * set default values of device here
+	 * these register values cannot be read from the hardware
+	 * therefore set driver specific default values
+	 */
+	ret = srf08_write_range_mm(data, SRF08_DEFAULT_RANGE);
+	if (ret < 0)
+		return ret;
+
+	ret = srf08_write_sensitivity(data, SRF08_DEFAULT_GAIN);
+	if (ret < 0)
+		return ret;
+
+	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 <ak@it-klinger.de>");
+MODULE_DESCRIPTION("Devantech SRF08 ultrasonic ranger driver");
+MODULE_LICENSE("GPL");