/*
 * hdc100x.c - Support for the TI HDC100x temperature + humidity sensors
 *
 * 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.
 *
 */

#include <linux/delay.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/i2c.h>

#include <linux/iio/iio.h>
#include <linux/iio/sysfs.h>

#define HDC100X_REG_TEMP			0x00
#define HDC100X_REG_HUMIDITY			0x01

#define HDC100X_REG_CONFIG			0x02
#define HDC100X_REG_CONFIG_HEATER_EN		BIT(13)

struct hdc100x_data {
	struct i2c_client *client;
	struct mutex lock;
	u16 config;

	/* integration time of the sensor */
	int adc_int_us[2];
};

/* integration time in us */
static const int hdc100x_int_time[][3] = {
	{ 6350, 3650, 0 },	/* IIO_TEMP channel*/
	{ 6500, 3850, 2500 },	/* IIO_HUMIDITYRELATIVE channel */
};

/* HDC100X_REG_CONFIG shift and mask values */
static const struct {
	int shift;
	int mask;
} hdc100x_resolution_shift[2] = {
	{ /* IIO_TEMP channel */
		.shift = 10,
		.mask = 1
	},
	{ /* IIO_HUMIDITYRELATIVE channel */
		.shift = 8,
		.mask = 2,
	},
};

static IIO_CONST_ATTR(temp_integration_time_available,
		"0.00365 0.00635");

static IIO_CONST_ATTR(humidityrelative_integration_time_available,
		"0.0025 0.00385 0.0065");

static IIO_CONST_ATTR(out_current_heater_raw_available,
		"0 1");

static struct attribute *hdc100x_attributes[] = {
	&iio_const_attr_temp_integration_time_available.dev_attr.attr,
	&iio_const_attr_humidityrelative_integration_time_available.dev_attr.attr,
	&iio_const_attr_out_current_heater_raw_available.dev_attr.attr,
	NULL
};

static struct attribute_group hdc100x_attribute_group = {
	.attrs = hdc100x_attributes,
};

static const struct iio_chan_spec hdc100x_channels[] = {
	{
		.type = IIO_TEMP,
		.address = HDC100X_REG_TEMP,
		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
			BIT(IIO_CHAN_INFO_SCALE) |
			BIT(IIO_CHAN_INFO_INT_TIME) |
			BIT(IIO_CHAN_INFO_OFFSET),
	},
	{
		.type = IIO_HUMIDITYRELATIVE,
		.address = HDC100X_REG_HUMIDITY,
		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
			BIT(IIO_CHAN_INFO_SCALE) |
			BIT(IIO_CHAN_INFO_INT_TIME)
	},
	{
		.type = IIO_CURRENT,
		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
		.extend_name = "heater",
		.output = 1,
	},
};

static int hdc100x_update_config(struct hdc100x_data *data, int mask, int val)
{
	int tmp = (~mask & data->config) | val;
	int ret;

	ret = i2c_smbus_write_word_swapped(data->client,
						HDC100X_REG_CONFIG, tmp);
	if (!ret)
		data->config = tmp;

	return ret;
}

static int hdc100x_set_it_time(struct hdc100x_data *data, int chan, int val2)
{
	int shift = hdc100x_resolution_shift[chan].shift;
	int ret = -EINVAL;
	int i;

	for (i = 0; i < ARRAY_SIZE(hdc100x_int_time[chan]); i++) {
		if (val2 && val2 == hdc100x_int_time[chan][i]) {
			ret = hdc100x_update_config(data,
				hdc100x_resolution_shift[chan].mask << shift,
				i << shift);
			if (!ret)
				data->adc_int_us[chan] = val2;
			break;
		}
	}

	return ret;
}

static int hdc100x_get_measurement(struct hdc100x_data *data,
				   struct iio_chan_spec const *chan)
{
	struct i2c_client *client = data->client;
	int delay = data->adc_int_us[chan->address];
	int ret;
	int val;

	/* start measurement */
	ret = i2c_smbus_write_byte(client, chan->address);
	if (ret < 0) {
		dev_err(&client->dev, "cannot start measurement");
		return ret;
	}

	/* wait for integration time to pass */
	usleep_range(delay, delay + 1000);

	/*
	 * i2c_smbus_read_word_data cannot() be used here due to the command
	 * value not being understood and causes NAKs preventing any reading
	 * from being accessed.
	 */
	ret = i2c_smbus_read_byte(client);
	if (ret < 0) {
		dev_err(&client->dev, "cannot read high byte measurement");
		return ret;
	}
	val = ret << 6;

	ret = i2c_smbus_read_byte(client);
	if (ret < 0) {
		dev_err(&client->dev, "cannot read low byte measurement");
		return ret;
	}
	val |= ret >> 2;

	return val;
}

static int hdc100x_get_heater_status(struct hdc100x_data *data)
{
	return !!(data->config & HDC100X_REG_CONFIG_HEATER_EN);
}

static int hdc100x_read_raw(struct iio_dev *indio_dev,
			    struct iio_chan_spec const *chan, int *val,
			    int *val2, long mask)
{
	struct hdc100x_data *data = iio_priv(indio_dev);

	switch (mask) {
	case IIO_CHAN_INFO_RAW: {
		int ret;

		mutex_lock(&data->lock);
		if (chan->type == IIO_CURRENT) {
			*val = hdc100x_get_heater_status(data);
			ret = IIO_VAL_INT;
		} else {
			ret = hdc100x_get_measurement(data, chan);
			if (ret >= 0) {
				*val = ret;
				ret = IIO_VAL_INT;
			}
		}
		mutex_unlock(&data->lock);
		return ret;
	}
	case IIO_CHAN_INFO_INT_TIME:
		*val = 0;
		*val2 = data->adc_int_us[chan->address];
		return IIO_VAL_INT_PLUS_MICRO;
	case IIO_CHAN_INFO_SCALE:
		if (chan->type == IIO_TEMP) {
			*val = 165;
			*val2 = 65536 >> 2;
			return IIO_VAL_FRACTIONAL;
		} else {
			*val = 0;
			*val2 = 10000;
			return IIO_VAL_INT_PLUS_MICRO;
		}
		break;
	case IIO_CHAN_INFO_OFFSET:
		*val = -3971;
		*val2 = 879096;
		return IIO_VAL_INT_PLUS_MICRO;
	default:
		return -EINVAL;
	}
}

static int hdc100x_write_raw(struct iio_dev *indio_dev,
			     struct iio_chan_spec const *chan,
			     int val, int val2, long mask)
{
	struct hdc100x_data *data = iio_priv(indio_dev);
	int ret = -EINVAL;

	switch (mask) {
	case IIO_CHAN_INFO_INT_TIME:
		if (val != 0)
			return -EINVAL;

		mutex_lock(&data->lock);
		ret = hdc100x_set_it_time(data, chan->address, val2);
		mutex_unlock(&data->lock);
		return ret;
	case IIO_CHAN_INFO_RAW:
		if (chan->type != IIO_CURRENT || val2 != 0)
			return -EINVAL;

		mutex_lock(&data->lock);
		ret = hdc100x_update_config(data, HDC100X_REG_CONFIG_HEATER_EN,
					val ? HDC100X_REG_CONFIG_HEATER_EN : 0);
		mutex_unlock(&data->lock);
		return ret;
	default:
		return -EINVAL;
	}
}

static const struct iio_info hdc100x_info = {
	.read_raw = hdc100x_read_raw,
	.write_raw = hdc100x_write_raw,
	.attrs = &hdc100x_attribute_group,
	.driver_module = THIS_MODULE,
};

static int hdc100x_probe(struct i2c_client *client,
			 const struct i2c_device_id *id)
{
	struct iio_dev *indio_dev;
	struct hdc100x_data *data;

	if (!i2c_check_functionality(client->adapter,
				I2C_FUNC_SMBUS_WORD_DATA | I2C_FUNC_SMBUS_BYTE))
		return -EOPNOTSUPP;

	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;
	mutex_init(&data->lock);

	indio_dev->dev.parent = &client->dev;
	indio_dev->name = dev_name(&client->dev);
	indio_dev->modes = INDIO_DIRECT_MODE;
	indio_dev->info = &hdc100x_info;

	indio_dev->channels = hdc100x_channels;
	indio_dev->num_channels = ARRAY_SIZE(hdc100x_channels);

	/* be sure we are in a known state */
	hdc100x_set_it_time(data, 0, hdc100x_int_time[0][0]);
	hdc100x_set_it_time(data, 1, hdc100x_int_time[1][0]);

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

static const struct i2c_device_id hdc100x_id[] = {
	{ "hdc100x", 0 },
	{ }
};
MODULE_DEVICE_TABLE(i2c, hdc100x_id);

static struct i2c_driver hdc100x_driver = {
	.driver = {
		.name	= "hdc100x",
	},
	.probe = hdc100x_probe,
	.id_table = hdc100x_id,
};
module_i2c_driver(hdc100x_driver);

MODULE_AUTHOR("Matt Ranostay <mranostay@gmail.com>");
MODULE_DESCRIPTION("TI HDC100x humidity and temperature sensor driver");
MODULE_LICENSE("GPL");