// SPDX-License-Identifier: GPL-2.0
/*
 * Sensirion SCD30 carbon dioxide sensor i2c driver
 *
 * Copyright (c) 2020 Tomasz Duszynski <tomasz.duszynski@octakon.com>
 *
 * I2C slave address: 0x61
 */
#include <linux/crc8.h>
#include <linux/device.h>
#include <linux/errno.h>
#include <linux/i2c.h>
#include <linux/mod_devicetable.h>
#include <linux/module.h>
#include <linux/types.h>
#include <linux/unaligned.h>

#include "scd30.h"

#define SCD30_I2C_MAX_BUF_SIZE 18
#define SCD30_I2C_CRC8_POLYNOMIAL 0x31

static u16 scd30_i2c_cmd_lookup_tbl[] = {
        [CMD_START_MEAS] = 0x0010,
        [CMD_STOP_MEAS] = 0x0104,
        [CMD_MEAS_INTERVAL] = 0x4600,
        [CMD_MEAS_READY] = 0x0202,
        [CMD_READ_MEAS] = 0x0300,
        [CMD_ASC] = 0x5306,
        [CMD_FRC] = 0x5204,
        [CMD_TEMP_OFFSET] = 0x5403,
        [CMD_FW_VERSION] = 0xd100,
        [CMD_RESET] = 0xd304,
};

DECLARE_CRC8_TABLE(scd30_i2c_crc8_tbl);

static int scd30_i2c_xfer(struct scd30_state *state, char *txbuf, int txsize,
                          char *rxbuf, int rxsize)
{
        struct i2c_client *client = to_i2c_client(state->dev);
        int ret;

        /*
         * repeated start is not supported hence instead of sending two i2c
         * messages in a row we send one by one
         */
        ret = i2c_master_send(client, txbuf, txsize);
        if (ret < 0)
                return ret;
        if (ret != txsize)
                return -EIO;

        if (!rxbuf)
                return 0;

        ret = i2c_master_recv(client, rxbuf, rxsize);
        if (ret < 0)
                return ret;
        if (ret != rxsize)
                return -EIO;

        return 0;
}

static int scd30_i2c_command(struct scd30_state *state, enum scd30_cmd cmd, u16 arg,
                             void *response, int size)
{
        char buf[SCD30_I2C_MAX_BUF_SIZE];
        char *rsp = response;
        int i, ret;
        char crc;

        put_unaligned_be16(scd30_i2c_cmd_lookup_tbl[cmd], buf);
        i = 2;

        if (rsp) {
                /* each two bytes are followed by a crc8 */
                size += size / 2;
        } else {
                put_unaligned_be16(arg, buf + i);
                crc = crc8(scd30_i2c_crc8_tbl, buf + i, 2, CRC8_INIT_VALUE);
                i += 2;
                buf[i] = crc;
                i += 1;

                /* commands below don't take an argument */
                if ((cmd == CMD_STOP_MEAS) || (cmd == CMD_RESET))
                        i -= 3;
        }

        ret = scd30_i2c_xfer(state, buf, i, buf, size);
        if (ret)
                return ret;

        /* validate received data and strip off crc bytes */
        for (i = 0; i < size; i += 3) {
                crc = crc8(scd30_i2c_crc8_tbl, buf + i, 2, CRC8_INIT_VALUE);
                if (crc != buf[i + 2]) {
                        dev_err(state->dev, "data integrity check failed\n");
                        return -EIO;
                }

                *rsp++ = buf[i];
                *rsp++ = buf[i + 1];
        }

        return 0;
}

static int scd30_i2c_probe(struct i2c_client *client)
{
        if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
                return -EOPNOTSUPP;

        crc8_populate_msb(scd30_i2c_crc8_tbl, SCD30_I2C_CRC8_POLYNOMIAL);

        return scd30_probe(&client->dev, client->irq, client->name, NULL, scd30_i2c_command);
}

static const struct of_device_id scd30_i2c_of_match[] = {
        { .compatible = "sensirion,scd30" },
        { }
};
MODULE_DEVICE_TABLE(of, scd30_i2c_of_match);

static struct i2c_driver scd30_i2c_driver = {
        .driver = {
                .name = KBUILD_MODNAME,
                .of_match_table = scd30_i2c_of_match,
                .pm = pm_sleep_ptr(&scd30_pm_ops),
        },
        .probe = scd30_i2c_probe,
};
module_i2c_driver(scd30_i2c_driver);

MODULE_AUTHOR("Tomasz Duszynski <tomasz.duszynski@octakon.com>");
MODULE_DESCRIPTION("Sensirion SCD30 carbon dioxide sensor i2c driver");
MODULE_LICENSE("GPL v2");
MODULE_IMPORT_NS("IIO_SCD30");