linux/drivers/hwmon/hih6130.c
<<
>>
Prefs
   1/* Honeywell HIH-6130/HIH-6131 humidity and temperature sensor driver
   2 *
   3 * Copyright (C) 2012 Iain Paton <ipaton0@gmail.com>
   4 *
   5 * heavily based on the sht21 driver
   6 * Copyright (C) 2010 Urs Fleisch <urs.fleisch@sensirion.com>
   7 *
   8 * This program is free software; you can redistribute it and/or modify
   9 * it under the terms of the GNU General Public License as published by
  10 * the Free Software Foundation; either version 2 of the License, or
  11 * (at your option) any later version.
  12 *
  13 * This program is distributed in the hope that it will be useful,
  14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16 * GNU General Public License for more details.
  17 *
  18 * You should have received a copy of the GNU General Public License
  19 * along with this program; if not, write to the Free Software
  20 * Foundation, Inc., 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA
  21 *
  22 * Data sheets available (2012-06-22) at
  23 * http://sensing.honeywell.com/index.php?ci_id=3106&la_id=1&defId=44872
  24 */
  25
  26#include <linux/module.h>
  27#include <linux/init.h>
  28#include <linux/slab.h>
  29#include <linux/i2c.h>
  30#include <linux/hwmon.h>
  31#include <linux/hwmon-sysfs.h>
  32#include <linux/err.h>
  33#include <linux/mutex.h>
  34#include <linux/device.h>
  35#include <linux/delay.h>
  36#include <linux/jiffies.h>
  37
  38/**
  39 * struct hih6130 - HIH-6130 device specific data
  40 * @hwmon_dev: device registered with hwmon
  41 * @lock: mutex to protect measurement values
  42 * @valid: only false before first measurement is taken
  43 * @last_update: time of last update (jiffies)
  44 * @temperature: cached temperature measurement value
  45 * @humidity: cached humidity measurement value
  46 */
  47struct hih6130 {
  48        struct device *hwmon_dev;
  49        struct mutex lock;
  50        bool valid;
  51        unsigned long last_update;
  52        int temperature;
  53        int humidity;
  54};
  55
  56/**
  57 * hih6130_temp_ticks_to_millicelsius() - convert raw temperature ticks to
  58 * milli celsius
  59 * @ticks: temperature ticks value received from sensor
  60 */
  61static inline int hih6130_temp_ticks_to_millicelsius(int ticks)
  62{
  63
  64        ticks = ticks >> 2;
  65        /*
  66         * from data sheet section 5.0
  67         * Formula T = ( ticks / ( 2^14 - 2 ) ) * 165 -40
  68         */
  69        return (DIV_ROUND_CLOSEST(ticks * 1650, 16382) - 400) * 100;
  70}
  71
  72/**
  73 * hih6130_rh_ticks_to_per_cent_mille() - convert raw humidity ticks to
  74 * one-thousandths of a percent relative humidity
  75 * @ticks: humidity ticks value received from sensor
  76 */
  77static inline int hih6130_rh_ticks_to_per_cent_mille(int ticks)
  78{
  79
  80        ticks &= ~0xC000; /* clear status bits */
  81        /*
  82         * from data sheet section 4.0
  83         * Formula RH = ( ticks / ( 2^14 -2 ) ) * 100
  84         */
  85        return DIV_ROUND_CLOSEST(ticks * 1000, 16382) * 100;
  86}
  87
  88/**
  89 * hih6130_update_measurements() - get updated measurements from device
  90 * @client: I2C client device
  91 *
  92 * Returns 0 on success, else negative errno.
  93 */
  94static int hih6130_update_measurements(struct i2c_client *client)
  95{
  96        int ret = 0;
  97        int t;
  98        struct hih6130 *hih6130 = i2c_get_clientdata(client);
  99        unsigned char tmp[4];
 100        struct i2c_msg msgs[1] = {
 101                {
 102                        .addr = client->addr,
 103                        .flags = I2C_M_RD,
 104                        .len = 4,
 105                        .buf = tmp,
 106                }
 107        };
 108
 109        mutex_lock(&hih6130->lock);
 110
 111        /*
 112         * While the measurement can be completed in ~40ms the sensor takes
 113         * much longer to react to a change in external conditions. How quickly
 114         * it reacts depends on airflow and other factors outwith our control.
 115         * The datasheet specifies maximum 'Response time' for humidity at 8s
 116         * and temperature at 30s under specified conditions.
 117         * We therefore choose to only read the sensor at most once per second.
 118         * This trades off pointless activity polling the sensor much faster
 119         * than it can react against better response times in conditions more
 120         * favourable than specified in the datasheet.
 121         */
 122        if (time_after(jiffies, hih6130->last_update + HZ) || !hih6130->valid) {
 123
 124                /* write to slave address, no data, to request a measurement */
 125                ret = i2c_master_send(client, tmp, 0);
 126                if (ret < 0)
 127                        goto out;
 128
 129                /* measurement cycle time is ~36.65msec */
 130                msleep(40);
 131
 132                ret = i2c_transfer(client->adapter, msgs, 1);
 133                if (ret < 0)
 134                        goto out;
 135
 136                if ((tmp[0] & 0xC0) != 0) {
 137                        dev_err(&client->dev, "Error while reading measurement result\n");
 138                        ret = -EIO;
 139                        goto out;
 140                }
 141
 142                t = (tmp[0] << 8) + tmp[1];
 143                hih6130->humidity = hih6130_rh_ticks_to_per_cent_mille(t);
 144
 145                t = (tmp[2] << 8) + tmp[3];
 146                hih6130->temperature = hih6130_temp_ticks_to_millicelsius(t);
 147
 148                hih6130->last_update = jiffies;
 149                hih6130->valid = true;
 150        }
 151out:
 152        mutex_unlock(&hih6130->lock);
 153
 154        return ret >= 0 ? 0 : ret;
 155}
 156
 157/**
 158 * hih6130_show_temperature() - show temperature measurement value in sysfs
 159 * @dev: device
 160 * @attr: device attribute
 161 * @buf: sysfs buffer (PAGE_SIZE) where measurement values are written to
 162 *
 163 * Will be called on read access to temp1_input sysfs attribute.
 164 * Returns number of bytes written into buffer, negative errno on error.
 165 */
 166static ssize_t hih6130_show_temperature(struct device *dev,
 167                                        struct device_attribute *attr,
 168                                        char *buf)
 169{
 170        struct i2c_client *client = to_i2c_client(dev);
 171        struct hih6130 *hih6130 = i2c_get_clientdata(client);
 172        int ret = hih6130_update_measurements(client);
 173        if (ret < 0)
 174                return ret;
 175        return sprintf(buf, "%d\n", hih6130->temperature);
 176}
 177
 178/**
 179 * hih6130_show_humidity() - show humidity measurement value in sysfs
 180 * @dev: device
 181 * @attr: device attribute
 182 * @buf: sysfs buffer (PAGE_SIZE) where measurement values are written to
 183 *
 184 * Will be called on read access to humidity1_input sysfs attribute.
 185 * Returns number of bytes written into buffer, negative errno on error.
 186 */
 187static ssize_t hih6130_show_humidity(struct device *dev,
 188                                     struct device_attribute *attr, char *buf)
 189{
 190        struct i2c_client *client = to_i2c_client(dev);
 191        struct hih6130 *hih6130 = i2c_get_clientdata(client);
 192        int ret = hih6130_update_measurements(client);
 193        if (ret < 0)
 194                return ret;
 195        return sprintf(buf, "%d\n", hih6130->humidity);
 196}
 197
 198/* sysfs attributes */
 199static SENSOR_DEVICE_ATTR(temp1_input, S_IRUGO, hih6130_show_temperature,
 200        NULL, 0);
 201static SENSOR_DEVICE_ATTR(humidity1_input, S_IRUGO, hih6130_show_humidity,
 202        NULL, 0);
 203
 204static struct attribute *hih6130_attributes[] = {
 205        &sensor_dev_attr_temp1_input.dev_attr.attr,
 206        &sensor_dev_attr_humidity1_input.dev_attr.attr,
 207        NULL
 208};
 209
 210static const struct attribute_group hih6130_attr_group = {
 211        .attrs = hih6130_attributes,
 212};
 213
 214/**
 215 * hih6130_probe() - probe device
 216 * @client: I2C client device
 217 * @id: device ID
 218 *
 219 * Called by the I2C core when an entry in the ID table matches a
 220 * device's name.
 221 * Returns 0 on success.
 222 */
 223static int hih6130_probe(struct i2c_client *client,
 224                                   const struct i2c_device_id *id)
 225{
 226        struct hih6130 *hih6130;
 227        int err;
 228
 229        if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
 230                dev_err(&client->dev, "adapter does not support true I2C\n");
 231                return -ENODEV;
 232        }
 233
 234        hih6130 = devm_kzalloc(&client->dev, sizeof(*hih6130), GFP_KERNEL);
 235        if (!hih6130)
 236                return -ENOMEM;
 237
 238        i2c_set_clientdata(client, hih6130);
 239
 240        mutex_init(&hih6130->lock);
 241
 242        err = sysfs_create_group(&client->dev.kobj, &hih6130_attr_group);
 243        if (err) {
 244                dev_dbg(&client->dev, "could not create sysfs files\n");
 245                return err;
 246        }
 247
 248        hih6130->hwmon_dev = hwmon_device_register(&client->dev);
 249        if (IS_ERR(hih6130->hwmon_dev)) {
 250                dev_dbg(&client->dev, "unable to register hwmon device\n");
 251                err = PTR_ERR(hih6130->hwmon_dev);
 252                goto fail_remove_sysfs;
 253        }
 254
 255        return 0;
 256
 257fail_remove_sysfs:
 258        sysfs_remove_group(&client->dev.kobj, &hih6130_attr_group);
 259        return err;
 260}
 261
 262/**
 263 * hih6130_remove() - remove device
 264 * @client: I2C client device
 265 */
 266static int hih6130_remove(struct i2c_client *client)
 267{
 268        struct hih6130 *hih6130 = i2c_get_clientdata(client);
 269
 270        hwmon_device_unregister(hih6130->hwmon_dev);
 271        sysfs_remove_group(&client->dev.kobj, &hih6130_attr_group);
 272
 273        return 0;
 274}
 275
 276/* Device ID table */
 277static const struct i2c_device_id hih6130_id[] = {
 278        { "hih6130", 0 },
 279        { }
 280};
 281MODULE_DEVICE_TABLE(i2c, hih6130_id);
 282
 283static struct i2c_driver hih6130_driver = {
 284        .driver.name = "hih6130",
 285        .probe       = hih6130_probe,
 286        .remove      = hih6130_remove,
 287        .id_table    = hih6130_id,
 288};
 289
 290module_i2c_driver(hih6130_driver);
 291
 292MODULE_AUTHOR("Iain Paton <ipaton0@gmail.com>");
 293MODULE_DESCRIPTION("Honeywell HIH-6130 humidity and temperature sensor driver");
 294MODULE_LICENSE("GPL");
 295
lxr.linux.no kindly hosted by Redpill Linpro AS, provider of Linux consulting and operations services since 1995.