drivers/iio/chemical/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 <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
  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
  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
 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");