Date:   Sun, 22 Jan 2017 13:46:46 +0000
From:   Jonathan Cameron <jic23@...nel.org>
To:     Andreas Klinger <ak@...klinger.de>, knaack.h@....de,
        lars@...afoo.de, pmeerw@...erw.net, linux-iio@...r.kernel.org,
        linux-kernel@...r.kernel.org, ktsai@...ellamicro.com,
        wsa@...-dreams.de, robh+dt@...nel.org, pawel.moll@....com,
        mark.rutland@....com, ijc+devicetree@...lion.org.uk,
        galak@...eaurora.org, trivial@...nel.org, mranostay@...il.com,
        linux-i2c@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v3 2/3] iio: distance: srf08: add IIO driver for us ranger

On 17/01/17 13:49, Andreas Klinger wrote:
> 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@...klinger.de>
One suggestion inline. Otherwise, just the units of your new max_range
attribute as per comment on ABI docs.

Looking good.

Jonathan
> ---
>  drivers/iio/proximity/Kconfig  |  13 +-
>  drivers/iio/proximity/Makefile |   1 +
>  drivers/iio/proximity/srf08.c  | 405 +++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 418 insertions(+), 1 deletion(-)
>  create mode 100644 drivers/iio/proximity/srf08.c
> 
> diff --git a/drivers/iio/proximity/Kconfig b/drivers/iio/proximity/Kconfig
> index ef4c73db5b53..ab96cb7a0054 100644
> --- a/drivers/iio/proximity/Kconfig
> +++ b/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
> diff --git a/drivers/iio/proximity/Makefile b/drivers/iio/proximity/Makefile
> index 9aadd9a8ee99..e914c2a5dd49 100644
> --- a/drivers/iio/proximity/Makefile
> +++ b/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
> diff --git a/drivers/iio/proximity/srf08.c b/drivers/iio/proximity/srf08.c
> new file mode 100644
> index 000000000000..faab6cf3f1a2
> --- /dev/null
> +++ b/drivers/iio/proximity/srf08.c
> @@ -0,0 +1,405 @@
> +/*
> + * srf08.c - Support for Devantech SRF08 ultrasonic ranger
> + *
> + * Copyright (c) 2016 Andreas Klinger <ak@...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)
> +{
> +	int i, len = 0;
> +
> +	for (i = 0; i < 256; i++)
> +		len += scnprintf(buf + len, PAGE_SIZE - len,
> +							"%d ", (i + 1) * 43);
Does this fit in the page length? Guess it probably does.  See comment below.
> +
> +	buf[len - 1] = '\n';
> +
> +	return len;
> +}
> +
> +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\n", data->range_mm);
> +}
> +
> +/*
> + * 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;
> +	unsigned int val;
> +
> +	ret = kstrtouint(buf, 10, &val);
> +	if (ret)
> +		return ret;
> +
> +	ret = srf08_write_range_mm(data, val);
> +	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,
Might be useful to note we now allow more complex available descriptions
though they are not well documented at the moment (my fault - had a busy
few weeks).  See Documentation/ABI/testing/sysfs-bus-iio-dac-dpot for
a simplex example.

> +	&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_sensitivity(data, SRF08_DEFAULT_GAIN);
> +	if (ret < 0)
> +		return ret;
> +
> +	ret = srf08_write_range_mm(data, SRF08_DEFAULT_RANGE);
> +	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@...klinger.de>");
> +MODULE_DESCRIPTION("Devantech SRF08 ultrasonic ranger driver");
> +MODULE_LICENSE("GPL");
> 

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