// SPDX-License-Identifier: GPL-2.0+
/*
 * ams-iaq-core.c - Support for AMS iAQ-Core VOC sensors
 *
 * Copyright (C) 2015, 2018
 * Author: Matt Ranostay <matt.ranostay@konsulko.com>
 */

#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/init.h>
#include <linux/i2c.h>
#include <linux/iio/iio.h>

#define AMS_IAQCORE_DATA_SIZE           9

#define AMS_IAQCORE_VOC_CO2_IDX         0
#define AMS_IAQCORE_VOC_RESISTANCE_IDX  1
#define AMS_IAQCORE_VOC_TVOC_IDX        2

struct ams_iaqcore_reading {
        __be16 co2_ppm;
        u8 status;
        __be32 resistance;
        __be16 voc_ppb;
} __packed;

struct ams_iaqcore_data {
        struct i2c_client *client;
        struct mutex lock;
        unsigned long last_update;

        struct ams_iaqcore_reading buffer;
};

static const struct iio_chan_spec ams_iaqcore_channels[] = {
        {
                .type = IIO_CONCENTRATION,
                .channel2 = IIO_MOD_CO2,
                .modified = 1,
                .info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),
                .address = AMS_IAQCORE_VOC_CO2_IDX,
        },
        {
                .type = IIO_RESISTANCE,
                .info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),
                .address = AMS_IAQCORE_VOC_RESISTANCE_IDX,
        },
        {
                .type = IIO_CONCENTRATION,
                .channel2 = IIO_MOD_VOC,
                .modified = 1,
                .info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),
                .address = AMS_IAQCORE_VOC_TVOC_IDX,
        },
};

static int ams_iaqcore_read_measurement(struct ams_iaqcore_data *data)
{
        struct i2c_client *client = data->client;
        int ret;

        struct i2c_msg msg = {
                .addr = client->addr,
                .flags = client->flags | I2C_M_RD,
                .len = AMS_IAQCORE_DATA_SIZE,
                .buf = (char *) &data->buffer,
        };

        ret = i2c_transfer(client->adapter, &msg, 1);

        return (ret == AMS_IAQCORE_DATA_SIZE) ? 0 : ret;
}

static int ams_iaqcore_get_measurement(struct ams_iaqcore_data *data)
{
        int ret;

        /* sensor can only be polled once a second max per datasheet */
        if (!time_after(jiffies, data->last_update + HZ))
                return 0;

        ret = ams_iaqcore_read_measurement(data);
        if (ret < 0)
                return ret;

        data->last_update = jiffies;

        return 0;
}

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

        if (mask != IIO_CHAN_INFO_PROCESSED)
                return -EINVAL;

        mutex_lock(&data->lock);
        ret = ams_iaqcore_get_measurement(data);

        if (ret)
                goto err_out;

        switch (chan->address) {
        case AMS_IAQCORE_VOC_CO2_IDX:
                *val = 0;
                *val2 = be16_to_cpu(data->buffer.co2_ppm);
                ret = IIO_VAL_INT_PLUS_MICRO;
                break;
        case AMS_IAQCORE_VOC_RESISTANCE_IDX:
                *val = be32_to_cpu(data->buffer.resistance);
                ret = IIO_VAL_INT;
                break;
        case AMS_IAQCORE_VOC_TVOC_IDX:
                *val = 0;
                *val2 = be16_to_cpu(data->buffer.voc_ppb);
                ret = IIO_VAL_INT_PLUS_NANO;
                break;
        default:
                ret = -EINVAL;
        }

err_out:
        mutex_unlock(&data->lock);

        return ret;
}

static const struct iio_info ams_iaqcore_info = {
        .read_raw       = ams_iaqcore_read_raw,
};

static int ams_iaqcore_probe(struct i2c_client *client)
{
        struct iio_dev *indio_dev;
        struct ams_iaqcore_data *data;

        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;

        /* so initial reading will complete */
        data->last_update = jiffies - HZ;
        mutex_init(&data->lock);

        indio_dev->info = &ams_iaqcore_info;
        indio_dev->name = dev_name(&client->dev);
        indio_dev->modes = INDIO_DIRECT_MODE;

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

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

static const struct i2c_device_id ams_iaqcore_id[] = {
        { .name = "ams-iaq-core" },
        { }
};
MODULE_DEVICE_TABLE(i2c, ams_iaqcore_id);

static const struct of_device_id ams_iaqcore_dt_ids[] = {
        { .compatible = "ams,iaq-core" },
        { }
};
MODULE_DEVICE_TABLE(of, ams_iaqcore_dt_ids);

static struct i2c_driver ams_iaqcore_driver = {
        .driver = {
                .name   = "ams-iaq-core",
                .of_match_table = ams_iaqcore_dt_ids,
        },
        .probe = ams_iaqcore_probe,
        .id_table = ams_iaqcore_id,
};
module_i2c_driver(ams_iaqcore_driver);

MODULE_AUTHOR("Matt Ranostay <matt.ranostay@konsulko.com>");
MODULE_DESCRIPTION("AMS iAQ-Core VOC sensors");
MODULE_LICENSE("GPL v2");