/*
 * srf08.c - Support for Devantech SRFxx ultrasonic ranger
 *           with i2c interface
 * actually supported are srf02, srf08, srf10
 *
 * Copyright (c) 2016, 2017 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
 * http://www.robot-electronics.co.uk/htm/srf10tech.htm
 * http://www.robot-electronics.co.uk/htm/srf02tech.htm
 */

#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>
#include <linux/iio/buffer.h>
#include <linux/iio/trigger_consumer.h>
#include <linux/iio/triggered_buffer.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 */

enum srf08_sensor_type {
	SRF02,
	SRF08,
	SRF10,
	SRF_MAX_TYPE
};

struct srf08_chip_info {
	const int		*sensitivity_avail;
	int			num_sensitivity_avail;
	int			sensitivity_default;

	/* default value of Range in mm */
	int			range_default;
};

struct srf08_data {
	struct i2c_client	*client;

	/*
	 * Gain in the datasheet is called sensitivity here to distinct it
	 * from the gain used with amplifiers of adc's
	 */
	int			sensitivity;

	/* max. Range in mm */
	int			range_mm;
	struct mutex		lock;

	/* Ensure timestamp is naturally aligned */
	struct {
		s16 chan;
		s64 timestamp __aligned(8);
	} scan;

	/* Sensor-Type */
	enum srf08_sensor_type	sensor_type;

	/* Chip-specific information */
	const struct srf08_chip_info	*chip_info;
};

/*
 * 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 struct srf08_chip_info srf02_chip_info = {
	.sensitivity_avail	= NULL,
	.num_sensitivity_avail	= 0,
	.sensitivity_default	= 0,

	.range_default		= 0,
};

static const int srf08_sensitivity_avail[] = {
	 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 const struct srf08_chip_info srf08_chip_info = {
	.sensitivity_avail	= srf08_sensitivity_avail,
	.num_sensitivity_avail	= ARRAY_SIZE(srf08_sensitivity_avail),
	.sensitivity_default	= 1025,

	.range_default		= 6020,
};

static const int srf10_sensitivity_avail[] = {
	 40,  40,  50,  60,  70,  80, 100, 120,
	140, 200, 250, 300, 350, 400, 500, 600,
	700,
	};

static const struct srf08_chip_info srf10_chip_info = {
	.sensitivity_avail	= srf10_sensitivity_avail,
	.num_sensitivity_avail	= ARRAY_SIZE(srf10_sensitivity_avail),
	.sensitivity_default	= 700,

	.range_default		= 6020,
};

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 irqreturn_t srf08_trigger_handler(int irq, void *p)
{
	struct iio_poll_func *pf = p;
	struct iio_dev *indio_dev = pf->indio_dev;
	struct srf08_data *data = iio_priv(indio_dev);
	s16 sensor_data;

	sensor_data = srf08_read_ranging(data);
	if (sensor_data < 0)
		goto err;

	mutex_lock(&data->lock);

	data->scan.chan = sensor_data;
	iio_push_to_buffers_with_timestamp(indio_dev,
					   &data->scan, pf->timestamp);

	mutex_unlock(&data->lock);
err:
	iio_trigger_notify_done(indio_dev->trig);
	return IRQ_HANDLED;
}

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;
	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
	struct srf08_data *data = iio_priv(indio_dev);

	for (i = 0; i < data->chip_info->num_sensitivity_avail; i++)
		if (data->chip_info->sensitivity_avail[i])
			len += sprintf(buf + len, "%d ",
				data->chip_info->sensitivity_avail[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;

	if (!val)
		return -EINVAL;

	for (i = 0; i < data->chip_info->num_sensitivity_avail; i++)
		if (val && (val == data->chip_info->sensitivity_avail[i])) {
			regval = i;
			break;
		}

	if (i >= data->chip_info->num_sensitivity_avail)
		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),
		.scan_index = 0,
		.scan_type = {
			.sign = 's',
			.realbits = 16,
			.storagebits = 16,
			.endianness = IIO_CPU,
		},
	},
	IIO_CHAN_SOFT_TIMESTAMP(1),
};

static const struct iio_info srf08_info = {
	.read_raw = srf08_read_raw,
	.attrs = &srf08_attribute_group,
	.driver_module = THIS_MODULE,
};

/*
 * srf02 don't have an adjustable range or sensitivity,
 * so we don't need attributes at all
 */
static const struct iio_info srf02_info = {
	.read_raw = srf08_read_raw,
	.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;
	data->sensor_type = (enum srf08_sensor_type)id->driver_data;

	switch (data->sensor_type) {
	case SRF02:
		data->chip_info = &srf02_chip_info;
		indio_dev->info = &srf02_info;
		break;
	case SRF08:
		data->chip_info = &srf08_chip_info;
		indio_dev->info = &srf08_info;
		break;
	case SRF10:
		data->chip_info = &srf10_chip_info;
		indio_dev->info = &srf08_info;
		break;
	default:
		return -EINVAL;
	}

	indio_dev->name = id->name;
	indio_dev->dev.parent = &client->dev;
	indio_dev->modes = INDIO_DIRECT_MODE;
	indio_dev->channels = srf08_channels;
	indio_dev->num_channels = ARRAY_SIZE(srf08_channels);

	mutex_init(&data->lock);

	ret = devm_iio_triggered_buffer_setup(&client->dev, indio_dev,
			iio_pollfunc_store_time, srf08_trigger_handler, NULL);
	if (ret < 0) {
		dev_err(&client->dev, "setup of iio triggered buffer failed\n");
		return ret;
	}

	if (data->chip_info->range_default) {
		/*
		 * set default range of device in mm here
		 * these register values cannot be read from the hardware
		 * therefore set driver specific default values
		 *
		 * srf02 don't have a default value so it'll be omitted
		 */
		ret = srf08_write_range_mm(data,
					data->chip_info->range_default);
		if (ret < 0)
			return ret;
	}

	if (data->chip_info->sensitivity_default) {
		/*
		 * set default sensitivity of device here
		 * these register values cannot be read from the hardware
		 * therefore set driver specific default values
		 *
		 * srf02 don't have a default value so it'll be omitted
		 */
		ret = srf08_write_sensitivity(data,
				data->chip_info->sensitivity_default);
		if (ret < 0)
			return ret;
	}

	return devm_iio_device_register(&client->dev, indio_dev);
}

static const struct of_device_id of_srf08_match[] = {
	{ .compatible = "devantech,srf02", (void *)SRF02},
	{ .compatible = "devantech,srf08", (void *)SRF08},
	{ .compatible = "devantech,srf10", (void *)SRF10},
	{},
};

MODULE_DEVICE_TABLE(of, of_srf08_match);

static const struct i2c_device_id srf08_id[] = {
	{ "srf02", SRF02 },
	{ "srf08", SRF08 },
	{ "srf10", SRF10 },
	{ }
};
MODULE_DEVICE_TABLE(i2c, srf08_id);

static struct i2c_driver srf08_driver = {
	.driver = {
		.name	= "srf08",
		.of_match_table	= of_srf08_match,
	},
	.probe = srf08_probe,
	.id_table = srf08_id,
};
module_i2c_driver(srf08_driver);

MODULE_AUTHOR("Andreas Klinger <ak@it-klinger.de>");
MODULE_DESCRIPTION("Devantech SRF02/SRF08/SRF10 i2c ultrasonic ranger driver");
MODULE_LICENSE("GPL");