// SPDX-License-Identifier: GPL-2.0+
/*
 * vz89x.c - Support for SGX Sensortech MiCS VZ89X 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/mod_devicetable.h>

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

#define VZ89X_REG_MEASUREMENT           0x09
#define VZ89X_REG_MEASUREMENT_RD_SIZE   6
#define VZ89X_REG_MEASUREMENT_WR_SIZE   3

#define VZ89X_VOC_CO2_IDX               0
#define VZ89X_VOC_SHORT_IDX             1
#define VZ89X_VOC_TVOC_IDX              2
#define VZ89X_VOC_RESISTANCE_IDX        3

#define VZ89TE_REG_MEASUREMENT          0x0c
#define VZ89TE_REG_MEASUREMENT_RD_SIZE  7
#define VZ89TE_REG_MEASUREMENT_WR_SIZE  6

#define VZ89TE_VOC_TVOC_IDX             0
#define VZ89TE_VOC_CO2_IDX              1
#define VZ89TE_VOC_RESISTANCE_IDX       2

enum {
        VZ89X,
        VZ89TE,
};

struct vz89x_chip_data;

struct vz89x_data {
        struct i2c_client *client;
        const struct vz89x_chip_data *chip;
        struct mutex lock;
        int (*xfer)(struct vz89x_data *data, u8 cmd);

        bool is_valid;
        unsigned long last_update;
        u8 buffer[VZ89TE_REG_MEASUREMENT_RD_SIZE];
};

struct vz89x_chip_data {
        bool (*valid)(struct vz89x_data *data);
        const struct iio_chan_spec *channels;
        u8 num_channels;

        u8 cmd;
        u8 read_size;
        u8 write_size;
};

static const struct iio_chan_spec vz89x_channels[] = {
        {
                .type = IIO_CONCENTRATION,
                .channel2 = IIO_MOD_CO2,
                .modified = 1,
                .info_mask_separate =
                        BIT(IIO_CHAN_INFO_OFFSET) | BIT(IIO_CHAN_INFO_RAW),
                .address = VZ89X_VOC_CO2_IDX,
        },
        {
                .type = IIO_CONCENTRATION,
                .channel2 = IIO_MOD_VOC,
                .modified = 1,
                .info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
                .address = VZ89X_VOC_SHORT_IDX,
                .extend_name = "short",
        },
        {
                .type = IIO_CONCENTRATION,
                .channel2 = IIO_MOD_VOC,
                .modified = 1,
                .info_mask_separate =
                        BIT(IIO_CHAN_INFO_OFFSET) | BIT(IIO_CHAN_INFO_RAW),
                .address = VZ89X_VOC_TVOC_IDX,
        },
        {
                .type = IIO_RESISTANCE,
                .info_mask_separate =
                        BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE),
                .address = VZ89X_VOC_RESISTANCE_IDX,
                .scan_index = -1,
                .scan_type = {
                        .endianness = IIO_LE,
                },
        },
};

static const struct iio_chan_spec vz89te_channels[] = {
        {
                .type = IIO_CONCENTRATION,
                .channel2 = IIO_MOD_VOC,
                .modified = 1,
                .info_mask_separate =
                        BIT(IIO_CHAN_INFO_OFFSET) | BIT(IIO_CHAN_INFO_RAW),
                .address = VZ89TE_VOC_TVOC_IDX,
        },

        {
                .type = IIO_CONCENTRATION,
                .channel2 = IIO_MOD_CO2,
                .modified = 1,
                .info_mask_separate =
                        BIT(IIO_CHAN_INFO_OFFSET) | BIT(IIO_CHAN_INFO_RAW),
                .address = VZ89TE_VOC_CO2_IDX,
        },
        {
                .type = IIO_RESISTANCE,
                .info_mask_separate =
                        BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE),
                .address = VZ89TE_VOC_RESISTANCE_IDX,
                .scan_index = -1,
                .scan_type = {
                        .endianness = IIO_BE,
                },
        },
};

static IIO_CONST_ATTR(in_concentration_co2_scale, "0.00000698689");
static IIO_CONST_ATTR(in_concentration_voc_scale, "0.00000000436681223");

static struct attribute *vz89x_attributes[] = {
        &iio_const_attr_in_concentration_co2_scale.dev_attr.attr,
        &iio_const_attr_in_concentration_voc_scale.dev_attr.attr,
        NULL,
};

static const struct attribute_group vz89x_attrs_group = {
        .attrs = vz89x_attributes,
};

/*
 * Chipset sometime updates in the middle of a reading causing it to reset the
 * data pointer, and causing invalid reading of previous data.
 * We can check for this by reading MSB of the resistance reading that is
 * always zero, and by also confirming the VOC_short isn't zero.
 */

static bool vz89x_measurement_is_valid(struct vz89x_data *data)
{
        if (data->buffer[VZ89X_VOC_SHORT_IDX] == 0)
                return true;

        return !!(data->buffer[data->chip->read_size - 1] > 0);
}

/* VZ89TE device has a modified CRC-8 two complement check */
static bool vz89te_measurement_is_valid(struct vz89x_data *data)
{
        u8 crc = 0;
        int i, sum = 0;

        for (i = 0; i < (data->chip->read_size - 1); i++) {
                sum = crc + data->buffer[i];
                crc = sum;
                crc += sum / 256;
        }

        return !((0xff - crc) == data->buffer[data->chip->read_size - 1]);
}

static int vz89x_i2c_xfer(struct vz89x_data *data, u8 cmd)
{
        const struct vz89x_chip_data *chip = data->chip;
        struct i2c_client *client = data->client;
        struct i2c_msg msg[2];
        int ret;
        u8 buf[6] = { cmd, 0, 0, 0, 0, 0xf3 };

        msg[0].addr = client->addr;
        msg[0].flags = client->flags;
        msg[0].len = chip->write_size;
        msg[0].buf  = (char *) &buf;

        msg[1].addr = client->addr;
        msg[1].flags = client->flags | I2C_M_RD;
        msg[1].len = chip->read_size;
        msg[1].buf = (char *) &data->buffer;

        ret = i2c_transfer(client->adapter, msg, 2);

        return (ret == 2) ? 0 : ret;
}

static int vz89x_smbus_xfer(struct vz89x_data *data, u8 cmd)
{
        struct i2c_client *client = data->client;
        int ret;
        int i;

        ret = i2c_smbus_write_word_data(client, cmd, 0);
        if (ret < 0)
                return ret;

        for (i = 0; i < data->chip->read_size; i++) {
                ret = i2c_smbus_read_byte(client);
                if (ret < 0)
                        return ret;
                data->buffer[i] = ret;
        }

        return 0;
}

static int vz89x_get_measurement(struct vz89x_data *data)
{
        const struct vz89x_chip_data *chip = data->chip;
        int ret;

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

        data->is_valid = false;
        data->last_update = jiffies;

        ret = data->xfer(data, chip->cmd);
        if (ret < 0)
                return ret;

        ret = chip->valid(data);
        if (ret)
                return -EAGAIN;

        data->is_valid = true;

        return 0;
}

static int vz89x_get_resistance_reading(struct vz89x_data *data,
                                        struct iio_chan_spec const *chan,
                                        int *val)
{
        u8 *tmp = &data->buffer[chan->address];

        switch (chan->scan_type.endianness) {
        case IIO_LE:
                *val = le32_to_cpup((__le32 *) tmp) & GENMASK(23, 0);
                break;
        case IIO_BE:
                *val = be32_to_cpup((__be32 *) tmp) >> 8;
                break;
        default:
                return -EINVAL;
        }

        return 0;
}

static int vz89x_read_raw(struct iio_dev *indio_dev,
                          struct iio_chan_spec const *chan, int *val,
                          int *val2, long mask)
{
        struct vz89x_data *data = iio_priv(indio_dev);
        int ret = -EINVAL;

        switch (mask) {
        case IIO_CHAN_INFO_RAW:
                mutex_lock(&data->lock);
                ret = vz89x_get_measurement(data);
                mutex_unlock(&data->lock);

                if (ret)
                        return ret;

                switch (chan->type) {
                case IIO_CONCENTRATION:
                        *val = data->buffer[chan->address];
                        return IIO_VAL_INT;
                case IIO_RESISTANCE:
                        ret = vz89x_get_resistance_reading(data, chan, val);
                        if (!ret)
                                return IIO_VAL_INT;
                        break;
                default:
                        return -EINVAL;
                }
                break;
        case IIO_CHAN_INFO_SCALE:
                switch (chan->type) {
                case IIO_RESISTANCE:
                        *val = 10;
                        return IIO_VAL_INT;
                default:
                        return -EINVAL;
                }
                break;
        case IIO_CHAN_INFO_OFFSET:
                switch (chan->channel2) {
                case IIO_MOD_CO2:
                        *val = 44;
                        *val2 = 250000;
                        return IIO_VAL_INT_PLUS_MICRO;
                case IIO_MOD_VOC:
                        *val = -13;
                        return IIO_VAL_INT;
                default:
                        return -EINVAL;
                }
        }

        return ret;
}

static const struct iio_info vz89x_info = {
        .attrs          = &vz89x_attrs_group,
        .read_raw       = vz89x_read_raw,
};

static const struct vz89x_chip_data vz89x_chips[] = {
        {
                .valid = vz89x_measurement_is_valid,

                .cmd = VZ89X_REG_MEASUREMENT,
                .read_size = VZ89X_REG_MEASUREMENT_RD_SIZE,
                .write_size = VZ89X_REG_MEASUREMENT_WR_SIZE,

                .channels = vz89x_channels,
                .num_channels = ARRAY_SIZE(vz89x_channels),
        },
        {
                .valid = vz89te_measurement_is_valid,

                .cmd = VZ89TE_REG_MEASUREMENT,
                .read_size = VZ89TE_REG_MEASUREMENT_RD_SIZE,
                .write_size = VZ89TE_REG_MEASUREMENT_WR_SIZE,

                .channels = vz89te_channels,
                .num_channels = ARRAY_SIZE(vz89te_channels),
        },
};

static const struct of_device_id vz89x_dt_ids[] = {
        { .compatible = "sgx,vz89x", .data = &vz89x_chips[VZ89X] },
        { .compatible = "sgx,vz89te", .data = &vz89x_chips[VZ89TE] },
        { }
};
MODULE_DEVICE_TABLE(of, vz89x_dt_ids);

static int vz89x_probe(struct i2c_client *client)
{
        struct device *dev = &client->dev;
        struct iio_dev *indio_dev;
        struct vz89x_data *data;

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

        if (i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
                data->xfer = vz89x_i2c_xfer;
        else if (i2c_check_functionality(client->adapter,
                                I2C_FUNC_SMBUS_WORD_DATA | I2C_FUNC_SMBUS_BYTE))
                data->xfer = vz89x_smbus_xfer;
        else
                return -EOPNOTSUPP;

        data->chip = i2c_get_match_data(client);

        i2c_set_clientdata(client, indio_dev);
        data->client = client;
        data->last_update = jiffies - HZ;
        mutex_init(&data->lock);

        indio_dev->info = &vz89x_info;
        indio_dev->name = dev_name(dev);
        indio_dev->modes = INDIO_DIRECT_MODE;

        indio_dev->channels = data->chip->channels;
        indio_dev->num_channels = data->chip->num_channels;

        return devm_iio_device_register(dev, indio_dev);
}

static const struct i2c_device_id vz89x_id[] = {
        { "vz89x", (kernel_ulong_t)&vz89x_chips[VZ89X] },
        { "vz89te", (kernel_ulong_t)&vz89x_chips[VZ89TE] },
        { }
};
MODULE_DEVICE_TABLE(i2c, vz89x_id);

static struct i2c_driver vz89x_driver = {
        .driver = {
                .name   = "vz89x",
                .of_match_table = vz89x_dt_ids,
        },
        .probe = vz89x_probe,
        .id_table = vz89x_id,
};
module_i2c_driver(vz89x_driver);

MODULE_AUTHOR("Matt Ranostay <matt.ranostay@konsulko.com>");
MODULE_DESCRIPTION("SGX Sensortech MiCS VZ89X VOC sensors");
MODULE_LICENSE("GPL v2");