1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* Honeywell HIH-6130/HIH-6131 humidity and temperature sensor driver 3 * 4 * Copyright (C) 2012 Iain Paton <ipaton0@gmail.com> 5 * 6 * heavily based on the sht21 driver 7 * Copyright (C) 2010 Urs Fleisch <urs.fleisch@sensirion.com> 8 * 9 * Data sheets available (2012-06-22) at 10 * http://sensing.honeywell.com/index.php?ci_id=3106&la_id=1&defId=44872 11 */ 12 13 #include <linux/module.h> 14 #include <linux/init.h> 15 #include <linux/slab.h> 16 #include <linux/i2c.h> 17 #include <linux/hwmon.h> 18 #include <linux/hwmon-sysfs.h> 19 #include <linux/err.h> 20 #include <linux/mutex.h> 21 #include <linux/device.h> 22 #include <linux/delay.h> 23 #include <linux/jiffies.h> 24 25 /** 26 * struct hih6130 - HIH-6130 device specific data 27 * @client: pointer to I2C client device 28 * @lock: mutex to protect measurement values 29 * @valid: only false before first measurement is taken 30 * @last_update: time of last update (jiffies) 31 * @temperature: cached temperature measurement value 32 * @humidity: cached humidity measurement value 33 * @write_length: length for I2C measurement request 34 */ 35 struct hih6130 { 36 struct i2c_client *client; 37 struct mutex lock; 38 bool valid; 39 unsigned long last_update; 40 int temperature; 41 int humidity; 42 size_t write_length; 43 }; 44 45 /** 46 * hih6130_temp_ticks_to_millicelsius() - convert raw temperature ticks to 47 * milli celsius 48 * @ticks: temperature ticks value received from sensor 49 */ 50 static inline int hih6130_temp_ticks_to_millicelsius(int ticks) 51 { 52 ticks = ticks >> 2; 53 /* 54 * from data sheet section 5.0 55 * Formula T = ( ticks / ( 2^14 - 2 ) ) * 165 -40 56 */ 57 return (DIV_ROUND_CLOSEST(ticks * 1650, 16382) - 400) * 100; 58 } 59 60 /** 61 * hih6130_rh_ticks_to_per_cent_mille() - convert raw humidity ticks to 62 * one-thousandths of a percent relative humidity 63 * @ticks: humidity ticks value received from sensor 64 */ 65 static inline int hih6130_rh_ticks_to_per_cent_mille(int ticks) 66 { 67 ticks &= ~0xC000; /* clear status bits */ 68 /* 69 * from data sheet section 4.0 70 * Formula RH = ( ticks / ( 2^14 -2 ) ) * 100 71 */ 72 return DIV_ROUND_CLOSEST(ticks * 1000, 16382) * 100; 73 } 74 75 /** 76 * hih6130_update_measurements() - get updated measurements from device 77 * @dev: device 78 * 79 * Returns 0 on success, else negative errno. 80 */ 81 static int hih6130_update_measurements(struct device *dev) 82 { 83 struct hih6130 *hih6130 = dev_get_drvdata(dev); 84 struct i2c_client *client = hih6130->client; 85 int ret = 0; 86 int t; 87 unsigned char tmp[4]; 88 struct i2c_msg msgs[1] = { 89 { 90 .addr = client->addr, 91 .flags = I2C_M_RD, 92 .len = 4, 93 .buf = tmp, 94 } 95 }; 96 97 mutex_lock(&hih6130->lock); 98 99 /* 100 * While the measurement can be completed in ~40ms the sensor takes 101 * much longer to react to a change in external conditions. How quickly 102 * it reacts depends on airflow and other factors outwith our control. 103 * The datasheet specifies maximum 'Response time' for humidity at 8s 104 * and temperature at 30s under specified conditions. 105 * We therefore choose to only read the sensor at most once per second. 106 * This trades off pointless activity polling the sensor much faster 107 * than it can react against better response times in conditions more 108 * favourable than specified in the datasheet. 109 */ 110 if (time_after(jiffies, hih6130->last_update + HZ) || !hih6130->valid) { 111 112 /* 113 * Write to slave address to request a measurement. 114 * According with the datasheet it should be with no data, but 115 * for systems with I2C bus drivers that do not allow zero 116 * length packets we write one dummy byte to allow sensor 117 * measurements on them. 118 */ 119 tmp[0] = 0; 120 ret = i2c_master_send(client, tmp, hih6130->write_length); 121 if (ret < 0) 122 goto out; 123 124 /* measurement cycle time is ~36.65msec */ 125 msleep(40); 126 127 ret = i2c_transfer(client->adapter, msgs, 1); 128 if (ret < 0) 129 goto out; 130 131 if ((tmp[0] & 0xC0) != 0) { 132 dev_err(&client->dev, "Error while reading measurement result\n"); 133 ret = -EIO; 134 goto out; 135 } 136 137 t = (tmp[0] << 8) + tmp[1]; 138 hih6130->humidity = hih6130_rh_ticks_to_per_cent_mille(t); 139 140 t = (tmp[2] << 8) + tmp[3]; 141 hih6130->temperature = hih6130_temp_ticks_to_millicelsius(t); 142 143 hih6130->last_update = jiffies; 144 hih6130->valid = true; 145 } 146 out: 147 mutex_unlock(&hih6130->lock); 148 149 return ret >= 0 ? 0 : ret; 150 } 151 152 /** 153 * hih6130_show_temperature() - show temperature measurement value in sysfs 154 * @dev: device 155 * @attr: device attribute 156 * @buf: sysfs buffer (PAGE_SIZE) where measurement values are written to 157 * 158 * Will be called on read access to temp1_input sysfs attribute. 159 * Returns number of bytes written into buffer, negative errno on error. 160 */ 161 static ssize_t hih6130_temperature_show(struct device *dev, 162 struct device_attribute *attr, 163 char *buf) 164 { 165 struct hih6130 *hih6130 = dev_get_drvdata(dev); 166 int ret; 167 168 ret = hih6130_update_measurements(dev); 169 if (ret < 0) 170 return ret; 171 return sprintf(buf, "%d\n", hih6130->temperature); 172 } 173 174 /** 175 * hih6130_show_humidity() - show humidity measurement value in sysfs 176 * @dev: device 177 * @attr: device attribute 178 * @buf: sysfs buffer (PAGE_SIZE) where measurement values are written to 179 * 180 * Will be called on read access to humidity1_input sysfs attribute. 181 * Returns number of bytes written into buffer, negative errno on error. 182 */ 183 static ssize_t hih6130_humidity_show(struct device *dev, 184 struct device_attribute *attr, char *buf) 185 { 186 struct hih6130 *hih6130 = dev_get_drvdata(dev); 187 int ret; 188 189 ret = hih6130_update_measurements(dev); 190 if (ret < 0) 191 return ret; 192 return sprintf(buf, "%d\n", hih6130->humidity); 193 } 194 195 /* sysfs attributes */ 196 static SENSOR_DEVICE_ATTR_RO(temp1_input, hih6130_temperature, 0); 197 static SENSOR_DEVICE_ATTR_RO(humidity1_input, hih6130_humidity, 0); 198 199 static struct attribute *hih6130_attrs[] = { 200 &sensor_dev_attr_temp1_input.dev_attr.attr, 201 &sensor_dev_attr_humidity1_input.dev_attr.attr, 202 NULL 203 }; 204 205 ATTRIBUTE_GROUPS(hih6130); 206 207 static int hih6130_probe(struct i2c_client *client) 208 { 209 struct device *dev = &client->dev; 210 struct hih6130 *hih6130; 211 struct device *hwmon_dev; 212 213 if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) { 214 dev_err(&client->dev, "adapter does not support true I2C\n"); 215 return -ENODEV; 216 } 217 218 hih6130 = devm_kzalloc(dev, sizeof(*hih6130), GFP_KERNEL); 219 if (!hih6130) 220 return -ENOMEM; 221 222 hih6130->client = client; 223 mutex_init(&hih6130->lock); 224 225 if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_QUICK)) 226 hih6130->write_length = 1; 227 228 hwmon_dev = devm_hwmon_device_register_with_groups(dev, client->name, 229 hih6130, 230 hih6130_groups); 231 return PTR_ERR_OR_ZERO(hwmon_dev); 232 } 233 234 /* Device ID table */ 235 static const struct i2c_device_id hih6130_id[] = { 236 { "hih6130", 0 }, 237 { } 238 }; 239 MODULE_DEVICE_TABLE(i2c, hih6130_id); 240 241 static const struct of_device_id __maybe_unused hih6130_of_match[] = { 242 { .compatible = "honeywell,hih6130", }, 243 { } 244 }; 245 MODULE_DEVICE_TABLE(of, hih6130_of_match); 246 247 static struct i2c_driver hih6130_driver = { 248 .driver = { 249 .name = "hih6130", 250 .of_match_table = of_match_ptr(hih6130_of_match), 251 }, 252 .probe_new = hih6130_probe, 253 .id_table = hih6130_id, 254 }; 255 256 module_i2c_driver(hih6130_driver); 257 258 MODULE_AUTHOR("Iain Paton <ipaton0@gmail.com>"); 259 MODULE_DESCRIPTION("Honeywell HIH-6130 humidity and temperature sensor driver"); 260 MODULE_LICENSE("GPL"); 261