/*
 * 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;

        /*
         * triggered buffer
         * 1x16-bit channel + 3x16 padding + 4x16 timestamp
         */
        s16                     buffer[8];

        /* 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->buffer[0] = sensor_data;
        iio_push_to_buffers_with_timestamp(indio_dev,
                                                data->buffer, 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");