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 <asm/unaligned.h>
17
18 #include "scd30.h"
19
20 #define SCD30_I2C_MAX_BUF_SIZE 18
21 #define SCD30_I2C_CRC8_POLYNOMIAL 0x31
22
23 static 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
36 DECLARE_CRC8_TABLE(scd30_i2c_crc8_tbl);
37
scd30_i2c_xfer(struct scd30_state * state,char * txbuf,int txsize,char * rxbuf,int rxsize)38 static 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
scd30_i2c_command(struct scd30_state * state,enum scd30_cmd cmd,u16 arg,void * response,int size)66 static 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
scd30_i2c_probe(struct i2c_client * client)111 static 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
121 static const struct of_device_id scd30_i2c_of_match[] = {
122 { .compatible = "sensirion,scd30" },
123 { }
124 };
125 MODULE_DEVICE_TABLE(of, scd30_i2c_of_match);
126
127 static struct i2c_driver scd30_i2c_driver = {
128 .driver = {
129 .name = KBUILD_MODNAME,
130 .of_match_table = scd30_i2c_of_match,
131 .pm = &scd30_pm_ops,
132 },
133 .probe_new = scd30_i2c_probe,
134 };
135 module_i2c_driver(scd30_i2c_driver);
136
137 MODULE_AUTHOR("Tomasz Duszynski <tomasz.duszynski@octakon.com>");
138 MODULE_DESCRIPTION("Sensirion SCD30 carbon dioxide sensor i2c driver");
139 MODULE_LICENSE("GPL v2");
140
