scd30_i2c.c

  1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * Sensirion SCD30 carbon dioxide sensor i2c driver
  4 *
  5 * Copyright (c) 2020 Tomasz Duszynski <tomasz.duszynski@octakon.com>
  6 *
  7 * I2C slave address: 0x61
  8 */
  9#include <linux/crc8.h>
 10#include <linux/device.h>
 11#include <linux/errno.h>
 12#include <linux/i2c.h>
 13#include <linux/mod_devicetable.h>
 14#include <linux/module.h>
 15#include <linux/types.h>
 16#include <linux/unaligned.h>
 17
 18#include "scd30.h"
 19
 20#define SCD30_I2C_MAX_BUF_SIZE 18
 21#define SCD30_I2C_CRC8_POLYNOMIAL 0x31
 22
 23static u16 scd30_i2c_cmd_lookup_tbl[] = {
 24	[CMD_START_MEAS] = 0x0010,
 25	[CMD_STOP_MEAS] = 0x0104,
 26	[CMD_MEAS_INTERVAL] = 0x4600,
 27	[CMD_MEAS_READY] = 0x0202,
 28	[CMD_READ_MEAS] = 0x0300,
 29	[CMD_ASC] = 0x5306,
 30	[CMD_FRC] = 0x5204,
 31	[CMD_TEMP_OFFSET] = 0x5403,
 32	[CMD_FW_VERSION] = 0xd100,
 33	[CMD_RESET] = 0xd304,
 34};
 35
 36DECLARE_CRC8_TABLE(scd30_i2c_crc8_tbl);
 37
 38static int scd30_i2c_xfer(struct scd30_state *state, char *txbuf, int txsize,
 39			  char *rxbuf, int rxsize)
 40{
 41	struct i2c_client *client = to_i2c_client(state->dev);
 42	int ret;
 43
 44	/*
 45	 * repeated start is not supported hence instead of sending two i2c
 46	 * messages in a row we send one by one
 47	 */
 48	ret = i2c_master_send(client, txbuf, txsize);
 49	if (ret < 0)
 50		return ret;
 51	if (ret != txsize)
 52		return -EIO;
 53
 54	if (!rxbuf)
 55		return 0;
 56
 57	ret = i2c_master_recv(client, rxbuf, rxsize);
 58	if (ret < 0)
 59		return ret;
 60	if (ret != rxsize)
 61		return -EIO;
 62
 63	return 0;
 64}
 65
 66static int scd30_i2c_command(struct scd30_state *state, enum scd30_cmd cmd, u16 arg,
 67			     void *response, int size)
 68{
 69	char buf[SCD30_I2C_MAX_BUF_SIZE];
 70	char *rsp = response;
 71	int i, ret;
 72	char crc;
 73
 74	put_unaligned_be16(scd30_i2c_cmd_lookup_tbl[cmd], buf);
 75	i = 2;
 76
 77	if (rsp) {
 78		/* each two bytes are followed by a crc8 */
 79		size += size / 2;
 80	} else {
 81		put_unaligned_be16(arg, buf + i);
 82		crc = crc8(scd30_i2c_crc8_tbl, buf + i, 2, CRC8_INIT_VALUE);
 83		i += 2;
 84		buf[i] = crc;
 85		i += 1;
 86
 87		/* commands below don't take an argument */
 88		if ((cmd == CMD_STOP_MEAS) || (cmd == CMD_RESET))
 89			i -= 3;
 90	}
 91
 92	ret = scd30_i2c_xfer(state, buf, i, buf, size);
 93	if (ret)
 94		return ret;
 95
 96	/* validate received data and strip off crc bytes */
 97	for (i = 0; i < size; i += 3) {
 98		crc = crc8(scd30_i2c_crc8_tbl, buf + i, 2, CRC8_INIT_VALUE);
 99		if (crc != buf[i + 2]) {
100			dev_err(state->dev, "data integrity check failed\n");
101			return -EIO;
102		}
103
104		*rsp++ = buf[i];
105		*rsp++ = buf[i + 1];
106	}
107
108	return 0;
109}
110
111static int scd30_i2c_probe(struct i2c_client *client)
112{
113	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
114		return -EOPNOTSUPP;
115
116	crc8_populate_msb(scd30_i2c_crc8_tbl, SCD30_I2C_CRC8_POLYNOMIAL);
117
118	return scd30_probe(&client->dev, client->irq, client->name, NULL, scd30_i2c_command);
119}
120
121static const struct of_device_id scd30_i2c_of_match[] = {
122	{ .compatible = "sensirion,scd30" },
123	{ }
124};
125MODULE_DEVICE_TABLE(of, scd30_i2c_of_match);
126
127static struct i2c_driver scd30_i2c_driver = {
128	.driver = {
129		.name = KBUILD_MODNAME,
130		.of_match_table = scd30_i2c_of_match,
131		.pm = pm_sleep_ptr(&scd30_pm_ops),
132	},
133	.probe = scd30_i2c_probe,
134};
135module_i2c_driver(scd30_i2c_driver);
136
137MODULE_AUTHOR("Tomasz Duszynski <tomasz.duszynski@octakon.com>");
138MODULE_DESCRIPTION("Sensirion SCD30 carbon dioxide sensor i2c driver");
139MODULE_LICENSE("GPL v2");
140MODULE_IMPORT_NS("IIO_SCD30");