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296 lines
7.4 KiB
296 lines
7.4 KiB
// SPDX-License-Identifier: GPL-2.0-or-later |
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/* Sensirion SHT21 humidity and temperature sensor driver |
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* |
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* Copyright (C) 2010 Urs Fleisch <[email protected]> |
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* |
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* Data sheet available at https://www.sensirion.com/file/datasheet_sht21 |
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*/ |
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#include <linux/module.h> |
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#include <linux/init.h> |
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#include <linux/slab.h> |
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#include <linux/i2c.h> |
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#include <linux/hwmon.h> |
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#include <linux/hwmon-sysfs.h> |
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#include <linux/err.h> |
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#include <linux/mutex.h> |
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#include <linux/device.h> |
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#include <linux/jiffies.h> |
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/* I2C command bytes */ |
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#define SHT21_TRIG_T_MEASUREMENT_HM 0xe3 |
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#define SHT21_TRIG_RH_MEASUREMENT_HM 0xe5 |
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#define SHT21_READ_SNB_CMD1 0xFA |
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#define SHT21_READ_SNB_CMD2 0x0F |
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#define SHT21_READ_SNAC_CMD1 0xFC |
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#define SHT21_READ_SNAC_CMD2 0xC9 |
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/** |
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* struct sht21 - SHT21 device specific data |
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* @client: I2C client device |
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* @lock: mutex to protect measurement values |
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* @last_update: time of last update (jiffies) |
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* @temperature: cached temperature measurement value |
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* @humidity: cached humidity measurement value |
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* @valid: only 0 before first measurement is taken |
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* @eic: cached electronic identification code text |
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*/ |
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struct sht21 { |
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struct i2c_client *client; |
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struct mutex lock; |
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unsigned long last_update; |
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int temperature; |
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int humidity; |
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char valid; |
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char eic[18]; |
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}; |
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/** |
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* sht21_temp_ticks_to_millicelsius() - convert raw temperature ticks to |
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* milli celsius |
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* @ticks: temperature ticks value received from sensor |
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*/ |
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static inline int sht21_temp_ticks_to_millicelsius(int ticks) |
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{ |
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ticks &= ~0x0003; /* clear status bits */ |
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/* |
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* Formula T = -46.85 + 175.72 * ST / 2^16 from data sheet 6.2, |
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* optimized for integer fixed point (3 digits) arithmetic |
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*/ |
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return ((21965 * ticks) >> 13) - 46850; |
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} |
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/** |
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* sht21_rh_ticks_to_per_cent_mille() - convert raw humidity ticks to |
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* one-thousandths of a percent relative humidity |
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* @ticks: humidity ticks value received from sensor |
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*/ |
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static inline int sht21_rh_ticks_to_per_cent_mille(int ticks) |
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{ |
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ticks &= ~0x0003; /* clear status bits */ |
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/* |
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* Formula RH = -6 + 125 * SRH / 2^16 from data sheet 6.1, |
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* optimized for integer fixed point (3 digits) arithmetic |
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*/ |
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return ((15625 * ticks) >> 13) - 6000; |
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} |
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/** |
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* sht21_update_measurements() - get updated measurements from device |
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* @dev: device |
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* |
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* Returns 0 on success, else negative errno. |
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*/ |
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static int sht21_update_measurements(struct device *dev) |
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{ |
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int ret = 0; |
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struct sht21 *sht21 = dev_get_drvdata(dev); |
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struct i2c_client *client = sht21->client; |
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mutex_lock(&sht21->lock); |
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/* |
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* Data sheet 2.4: |
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* SHT2x should not be active for more than 10% of the time - e.g. |
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* maximum two measurements per second at 12bit accuracy shall be made. |
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*/ |
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if (time_after(jiffies, sht21->last_update + HZ / 2) || !sht21->valid) { |
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ret = i2c_smbus_read_word_swapped(client, |
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SHT21_TRIG_T_MEASUREMENT_HM); |
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if (ret < 0) |
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goto out; |
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sht21->temperature = sht21_temp_ticks_to_millicelsius(ret); |
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ret = i2c_smbus_read_word_swapped(client, |
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SHT21_TRIG_RH_MEASUREMENT_HM); |
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if (ret < 0) |
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goto out; |
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sht21->humidity = sht21_rh_ticks_to_per_cent_mille(ret); |
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sht21->last_update = jiffies; |
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sht21->valid = 1; |
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} |
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out: |
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mutex_unlock(&sht21->lock); |
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return ret >= 0 ? 0 : ret; |
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} |
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/** |
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* sht21_show_temperature() - show temperature measurement value in sysfs |
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* @dev: device |
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* @attr: device attribute |
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* @buf: sysfs buffer (PAGE_SIZE) where measurement values are written to |
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* |
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* Will be called on read access to temp1_input sysfs attribute. |
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* Returns number of bytes written into buffer, negative errno on error. |
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*/ |
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static ssize_t sht21_temperature_show(struct device *dev, |
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struct device_attribute *attr, |
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char *buf) |
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{ |
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struct sht21 *sht21 = dev_get_drvdata(dev); |
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int ret; |
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ret = sht21_update_measurements(dev); |
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if (ret < 0) |
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return ret; |
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return sprintf(buf, "%d\n", sht21->temperature); |
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} |
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/** |
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* sht21_show_humidity() - show humidity measurement value in sysfs |
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* @dev: device |
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* @attr: device attribute |
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* @buf: sysfs buffer (PAGE_SIZE) where measurement values are written to |
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* |
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* Will be called on read access to humidity1_input sysfs attribute. |
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* Returns number of bytes written into buffer, negative errno on error. |
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*/ |
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static ssize_t sht21_humidity_show(struct device *dev, |
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struct device_attribute *attr, char *buf) |
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{ |
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struct sht21 *sht21 = dev_get_drvdata(dev); |
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int ret; |
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ret = sht21_update_measurements(dev); |
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if (ret < 0) |
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return ret; |
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return sprintf(buf, "%d\n", sht21->humidity); |
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} |
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static ssize_t eic_read(struct sht21 *sht21) |
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{ |
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struct i2c_client *client = sht21->client; |
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u8 tx[2]; |
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u8 rx[8]; |
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u8 eic[8]; |
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struct i2c_msg msgs[2] = { |
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{ |
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.addr = client->addr, |
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.flags = 0, |
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.len = 2, |
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.buf = tx, |
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}, |
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{ |
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.addr = client->addr, |
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.flags = I2C_M_RD, |
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.len = 8, |
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.buf = rx, |
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}, |
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}; |
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int ret; |
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tx[0] = SHT21_READ_SNB_CMD1; |
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tx[1] = SHT21_READ_SNB_CMD2; |
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ret = i2c_transfer(client->adapter, msgs, 2); |
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if (ret < 0) |
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goto out; |
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eic[2] = rx[0]; |
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eic[3] = rx[2]; |
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eic[4] = rx[4]; |
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eic[5] = rx[6]; |
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tx[0] = SHT21_READ_SNAC_CMD1; |
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tx[1] = SHT21_READ_SNAC_CMD2; |
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msgs[1].len = 6; |
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ret = i2c_transfer(client->adapter, msgs, 2); |
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if (ret < 0) |
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goto out; |
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eic[0] = rx[3]; |
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eic[1] = rx[4]; |
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eic[6] = rx[0]; |
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eic[7] = rx[1]; |
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ret = snprintf(sht21->eic, sizeof(sht21->eic), |
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"%02x%02x%02x%02x%02x%02x%02x%02x\n", |
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eic[0], eic[1], eic[2], eic[3], |
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eic[4], eic[5], eic[6], eic[7]); |
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out: |
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if (ret < 0) |
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sht21->eic[0] = 0; |
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return ret; |
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} |
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/** |
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* eic_show() - show Electronic Identification Code in sysfs |
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* @dev: device |
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* @attr: device attribute |
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* @buf: sysfs buffer (PAGE_SIZE) where EIC is written |
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* |
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* Will be called on read access to eic sysfs attribute. |
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* Returns number of bytes written into buffer, negative errno on error. |
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*/ |
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static ssize_t eic_show(struct device *dev, |
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struct device_attribute *attr, |
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char *buf) |
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{ |
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struct sht21 *sht21 = dev_get_drvdata(dev); |
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int ret; |
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ret = sizeof(sht21->eic) - 1; |
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mutex_lock(&sht21->lock); |
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if (!sht21->eic[0]) |
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ret = eic_read(sht21); |
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if (ret > 0) |
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memcpy(buf, sht21->eic, ret); |
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mutex_unlock(&sht21->lock); |
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return ret; |
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} |
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/* sysfs attributes */ |
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static SENSOR_DEVICE_ATTR_RO(temp1_input, sht21_temperature, 0); |
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static SENSOR_DEVICE_ATTR_RO(humidity1_input, sht21_humidity, 0); |
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static DEVICE_ATTR_RO(eic); |
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static struct attribute *sht21_attrs[] = { |
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&sensor_dev_attr_temp1_input.dev_attr.attr, |
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&sensor_dev_attr_humidity1_input.dev_attr.attr, |
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&dev_attr_eic.attr, |
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NULL |
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}; |
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ATTRIBUTE_GROUPS(sht21); |
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static int sht21_probe(struct i2c_client *client) |
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{ |
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struct device *dev = &client->dev; |
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struct device *hwmon_dev; |
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struct sht21 *sht21; |
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if (!i2c_check_functionality(client->adapter, |
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I2C_FUNC_SMBUS_WORD_DATA)) { |
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dev_err(&client->dev, |
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"adapter does not support SMBus word transactions\n"); |
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return -ENODEV; |
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} |
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sht21 = devm_kzalloc(dev, sizeof(*sht21), GFP_KERNEL); |
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if (!sht21) |
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return -ENOMEM; |
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sht21->client = client; |
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mutex_init(&sht21->lock); |
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hwmon_dev = devm_hwmon_device_register_with_groups(dev, client->name, |
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sht21, sht21_groups); |
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return PTR_ERR_OR_ZERO(hwmon_dev); |
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} |
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/* Device ID table */ |
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static const struct i2c_device_id sht21_id[] = { |
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{ "sht21", 0 }, |
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{ } |
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}; |
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MODULE_DEVICE_TABLE(i2c, sht21_id); |
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static struct i2c_driver sht21_driver = { |
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.driver.name = "sht21", |
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.probe_new = sht21_probe, |
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.id_table = sht21_id, |
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}; |
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module_i2c_driver(sht21_driver); |
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MODULE_AUTHOR("Urs Fleisch <[email protected]>"); |
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MODULE_DESCRIPTION("Sensirion SHT21 humidity and temperature sensor driver"); |
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MODULE_LICENSE("GPL");
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