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// 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 <asm/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 = &scd30_pm_ops,
},
.probe_new = 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");
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