// SPDX-License-Identifier: GPL-2.0-only
/*
 * Driver for Linear Technology LTC2471 and LTC2473 voltage monitors
 * The LTC2473 is identical to the 2471, but reports a differential signal.
 *
 * Copyright (C) 2017 Topic Embedded Products
 * Author: Mike Looijmans <mike.looijmans@topic.nl>
 */

#include <linux/err.h>
#include <linux/i2c.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/iio/iio.h>
#include <linux/iio/sysfs.h>

enum ltc2471_chips {
        ltc2471,
        ltc2473,
};

struct ltc2471_data {
        struct i2c_client *client;
};

/* Reference voltage is 1.25V */
#define LTC2471_VREF 1250

/* Read two bytes from the I2C bus to obtain the ADC result */
static int ltc2471_get_value(struct i2c_client *client)
{
        int ret;
        __be16 buf;

        ret = i2c_master_recv(client, (char *)&buf, sizeof(buf));
        if (ret < 0)
                return ret;
        if (ret != sizeof(buf))
                return -EIO;

        /* MSB first */
        return be16_to_cpu(buf);
}

static int ltc2471_read_raw(struct iio_dev *indio_dev,
                            struct iio_chan_spec const *chan,
                            int *val, int *val2, long info)
{
        struct ltc2471_data *data = iio_priv(indio_dev);
        int ret;

        switch (info) {
        case IIO_CHAN_INFO_RAW:
                ret = ltc2471_get_value(data->client);
                if (ret < 0)
                        return ret;
                *val = ret;
                return IIO_VAL_INT;

        case IIO_CHAN_INFO_SCALE:
                if (chan->differential)
                        /* Output ranges from -VREF to +VREF */
                        *val = 2 * LTC2471_VREF;
                else
                        /* Output ranges from 0 to VREF */
                        *val = LTC2471_VREF;
                *val2 = 16;     /* 16 data bits */
                return IIO_VAL_FRACTIONAL_LOG2;

        case IIO_CHAN_INFO_OFFSET:
                /* Only differential chip has this property */
                *val = -LTC2471_VREF;
                return IIO_VAL_INT;

        default:
                return -EINVAL;
        }
}

static const struct iio_chan_spec ltc2471_channel[] = {
        {
                .type = IIO_VOLTAGE,
                .info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
                .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),
        },
};

static const struct iio_chan_spec ltc2473_channel[] = {
        {
                .type = IIO_VOLTAGE,
                .info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
                .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE) |
                                            BIT(IIO_CHAN_INFO_OFFSET),
                .differential = 1,
        },
};

static const struct iio_info ltc2471_info = {
        .read_raw = ltc2471_read_raw,
};

static int ltc2471_i2c_probe(struct i2c_client *client)
{
        const struct i2c_device_id *id = i2c_client_get_device_id(client);
        struct iio_dev *indio_dev;
        struct ltc2471_data *data;
        int ret;

        if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
                return -EOPNOTSUPP;

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

        data = iio_priv(indio_dev);
        data->client = client;

        indio_dev->name = id->name;
        indio_dev->info = &ltc2471_info;
        indio_dev->modes = INDIO_DIRECT_MODE;
        if (id->driver_data == ltc2473)
                indio_dev->channels = ltc2473_channel;
        else
                indio_dev->channels = ltc2471_channel;
        indio_dev->num_channels = 1;

        /* Trigger once to start conversion and check if chip is there */
        ret = ltc2471_get_value(client);
        if (ret < 0) {
                dev_err(&client->dev, "Cannot read from device.\n");
                return ret;
        }

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

static const struct i2c_device_id ltc2471_i2c_id[] = {
        { "ltc2471", ltc2471 },
        { "ltc2473", ltc2473 },
        { }
};
MODULE_DEVICE_TABLE(i2c, ltc2471_i2c_id);

static struct i2c_driver ltc2471_i2c_driver = {
        .driver = {
                .name = "ltc2471",
        },
        .probe = ltc2471_i2c_probe,
        .id_table = ltc2471_i2c_id,
};

module_i2c_driver(ltc2471_i2c_driver);

MODULE_DESCRIPTION("LTC2471/LTC2473 ADC driver");
MODULE_AUTHOR("Topic Embedded Products");
MODULE_LICENSE("GPL v2");