/*
 * pulsedlight-lidar-lite-v2.c - Support for PulsedLight LIDAR sensor
 *
 * Copyright (C) 2015 Matt Ranostay <mranostay@gmail.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * TODO: runtime pm, interrupt mode, and signal strength reporting
 */

#include <linux/err.h>
#include <linux/init.h>
#include <linux/i2c.h>
#include <linux/delay.h>
#include <linux/module.h>
#include <linux/iio/iio.h>
#include <linux/iio/sysfs.h>
#include <linux/iio/buffer.h>
#include <linux/iio/trigger.h>
#include <linux/iio/triggered_buffer.h>
#include <linux/iio/trigger_consumer.h>

#define LIDAR_REG_CONTROL		0x00
#define LIDAR_REG_CONTROL_ACQUIRE	BIT(2)

#define LIDAR_REG_STATUS		0x01
#define LIDAR_REG_STATUS_INVALID	BIT(3)
#define LIDAR_REG_STATUS_READY		BIT(0)

#define LIDAR_REG_DATA_HBYTE	0x0f
#define LIDAR_REG_DATA_LBYTE	0x10

#define LIDAR_DRV_NAME "lidar"

struct lidar_data {
	struct iio_dev *indio_dev;
	struct i2c_client *client;

	u16 buffer[8]; /* 2 byte distance + 8 byte timestamp */
};

static const struct iio_chan_spec lidar_channels[] = {
	{
		.type = IIO_DISTANCE,
		.info_mask_separate =
			BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE),
		.scan_index = 0,
		.scan_type = {
			.sign = 'u',
			.realbits = 16,
			.storagebits = 16,
		},
	},
	IIO_CHAN_SOFT_TIMESTAMP(1),
};

static int lidar_read_byte(struct lidar_data *data, int reg)
{
	struct i2c_client *client = data->client;
	int ret;

	/*
	 * Device needs a STOP condition between address write, and data read
	 * so in turn i2c_smbus_read_byte_data cannot be used
	 */

	ret = i2c_smbus_write_byte(client, reg);
	if (ret < 0) {
		dev_err(&client->dev, "cannot write addr value");
		return ret;
	}

	ret = i2c_smbus_read_byte(client);
	if (ret < 0)
		dev_err(&client->dev, "cannot read data value");

	return ret;
}

static inline int lidar_write_control(struct lidar_data *data, int val)
{
	return i2c_smbus_write_byte_data(data->client, LIDAR_REG_CONTROL, val);
}

static int lidar_read_measurement(struct lidar_data *data, u16 *reg)
{
	int ret;
	int val;

	ret = lidar_read_byte(data, LIDAR_REG_DATA_HBYTE);
	if (ret < 0)
		return ret;
	val = ret << 8;

	ret = lidar_read_byte(data, LIDAR_REG_DATA_LBYTE);
	if (ret < 0)
		return ret;

	val |= ret;
	*reg = val;

	return 0;
}

static int lidar_get_measurement(struct lidar_data *data, u16 *reg)
{
	struct i2c_client *client = data->client;
	int tries = 10;
	int ret;

	/* start sample */
	ret = lidar_write_control(data, LIDAR_REG_CONTROL_ACQUIRE);
	if (ret < 0) {
		dev_err(&client->dev, "cannot send start measurement command");
		return ret;
	}

	while (tries--) {
		usleep_range(1000, 2000);

		ret = lidar_read_byte(data, LIDAR_REG_STATUS);
		if (ret < 0)
			break;

		/* return -EINVAL since laser is likely pointed out of range */
		if (ret & LIDAR_REG_STATUS_INVALID) {
			*reg = 0;
			ret = -EINVAL;
			break;
		}

		/* sample ready to read */
		if (!(ret & LIDAR_REG_STATUS_READY)) {
			ret = lidar_read_measurement(data, reg);
			break;
		}
		ret = -EIO;
	}

	return ret;
}

static int lidar_read_raw(struct iio_dev *indio_dev,
			  struct iio_chan_spec const *chan,
			  int *val, int *val2, long mask)
{
	struct lidar_data *data = iio_priv(indio_dev);
	int ret = -EINVAL;

	mutex_lock(&indio_dev->mlock);

	if (iio_buffer_enabled(indio_dev) && mask == IIO_CHAN_INFO_RAW) {
		ret = -EBUSY;
		goto error_busy;
	}

	switch (mask) {
	case IIO_CHAN_INFO_RAW: {
		u16 reg;

		ret = lidar_get_measurement(data, &reg);
		if (!ret) {
			*val = reg;
			ret = IIO_VAL_INT;
		}
		break;
	}
	case IIO_CHAN_INFO_SCALE:
		*val = 0;
		*val2 = 10000;
		ret = IIO_VAL_INT_PLUS_MICRO;
		break;
	}

error_busy:
	mutex_unlock(&indio_dev->mlock);

	return ret;
}

static irqreturn_t lidar_trigger_handler(int irq, void *private)
{
	struct iio_poll_func *pf = private;
	struct iio_dev *indio_dev = pf->indio_dev;
	struct lidar_data *data = iio_priv(indio_dev);
	int ret;

	ret = lidar_get_measurement(data, data->buffer);
	if (!ret) {
		iio_push_to_buffers_with_timestamp(indio_dev, data->buffer,
						   iio_get_time_ns());
	} else if (ret != -EINVAL) {
		dev_err(&data->client->dev, "cannot read LIDAR measurement");
	}

	iio_trigger_notify_done(indio_dev->trig);

	return IRQ_HANDLED;
}

static const struct iio_info lidar_info = {
	.driver_module = THIS_MODULE,
	.read_raw = lidar_read_raw,
};

static int lidar_probe(struct i2c_client *client,
		       const struct i2c_device_id *id)
{
	struct lidar_data *data;
	struct iio_dev *indio_dev;
	int ret;

	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
	if (!indio_dev)
		return -ENOMEM;

	indio_dev->info = &lidar_info;
	indio_dev->name = LIDAR_DRV_NAME;
	indio_dev->channels = lidar_channels;
	indio_dev->num_channels = ARRAY_SIZE(lidar_channels);
	indio_dev->modes = INDIO_DIRECT_MODE;

	data = iio_priv(indio_dev);
	i2c_set_clientdata(client, indio_dev);

	data->client = client;
	data->indio_dev = indio_dev;

	ret = iio_triggered_buffer_setup(indio_dev, NULL,
					 lidar_trigger_handler, NULL);
	if (ret)
		return ret;

	ret = iio_device_register(indio_dev);
	if (ret)
		goto error_unreg_buffer;

	return 0;

error_unreg_buffer:
	iio_triggered_buffer_cleanup(indio_dev);

	return ret;
}

static int lidar_remove(struct i2c_client *client)
{
	struct iio_dev *indio_dev = i2c_get_clientdata(client);

	iio_device_unregister(indio_dev);
	iio_triggered_buffer_cleanup(indio_dev);

	return 0;
}

static const struct i2c_device_id lidar_id[] = {
	{"lidar-lite-v2", 0},
	{ },
};
MODULE_DEVICE_TABLE(i2c, lidar_id);

static const struct of_device_id lidar_dt_ids[] = {
	{ .compatible = "pulsedlight,lidar-lite-v2" },
	{ }
};
MODULE_DEVICE_TABLE(of, lidar_dt_ids);

static struct i2c_driver lidar_driver = {
	.driver = {
		.name	= LIDAR_DRV_NAME,
		.of_match_table	= of_match_ptr(lidar_dt_ids),
	},
	.probe		= lidar_probe,
	.remove		= lidar_remove,
	.id_table	= lidar_id,
};
module_i2c_driver(lidar_driver);

MODULE_AUTHOR("Matt Ranostay <mranostay@gmail.com>");
MODULE_DESCRIPTION("PulsedLight LIDAR sensor");
MODULE_LICENSE("GPL");