Messages in this thread Patch in this message | | | Date | Wed, 29 Dec 2010 13:45:11 +0100 | From | Urs Fleisch <> | Subject | [PATCH] hwmon: driver for Sensirion SHT21 humidity and temperature sensor |
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Hi,
This is a driver for the new humidity and temperature sensors SHT21 and SHT25 from Sensirion.
Regards, Urs
diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig index 95ccbe3..4a96429 100644 --- a/drivers/hwmon/Kconfig +++ b/drivers/hwmon/Kconfig @@ -688,6 +688,16 @@ config SENSORS_SHT15 This driver can also be built as a module. If so, the module will be called sht15. +config SENSORS_SHT21 + tristate "Sensiron humidity and temperature sensors. SHT21 and compat." + depends on I2C + help + If you say yes here you get support for the Sensiron SHT21, SHT25 + humidity and temperature sensors. + + This driver can also be built as a module. If so, the module + will be called sht21. + config SENSORS_S3C tristate "S3C24XX/S3C64XX Inbuilt ADC" depends on ARCH_S3C2410 diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile index 33c2ee1..7439653 100644 --- a/drivers/hwmon/Makefile +++ b/drivers/hwmon/Makefile @@ -80,6 +80,7 @@ obj-$(CONFIG_SENSORS_PC87427) += pc87427.o obj-$(CONFIG_SENSORS_PCF8591) += pcf8591.o obj-$(CONFIG_SENSORS_S3C) += s3c-hwmon.o obj-$(CONFIG_SENSORS_SHT15) += sht15.o +obj-$(CONFIG_SENSORS_SHT21) += sht21.o obj-$(CONFIG_SENSORS_SIS5595) += sis5595.o obj-$(CONFIG_SENSORS_SMM665) += smm665.o obj-$(CONFIG_SENSORS_SMSC47B397)+= smsc47b397.o diff --git a/drivers/hwmon/sht21.c b/drivers/hwmon/sht21.c new file mode 100644 index 0000000..7d3ec82 --- /dev/null +++ b/drivers/hwmon/sht21.c @@ -0,0 +1,392 @@ +/* Sensirion SHT21 humidity and temperature sensor driver + * + * Copyright (C) 2010 Urs Fleisch <urs.fleisch@sensirion.com> + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA + * + * Data sheet available (5/2010) at + * http://www.sensirion.com/en/pdf/product_information/Datasheet-humidity-sensor-SHT21.pdf + */ + +#include <linux/module.h> +#include <linux/init.h> +#include <linux/slab.h> +#include <linux/i2c.h> +#include <linux/hwmon.h> +#include <linux/hwmon-sysfs.h> +#include <linux/err.h> +#include <linux/mutex.h> +#include <linux/device.h> + +/* I2C commands bytes */ +enum sht21_command { + SHT21_TRIG_T_MEASUREMENT_HM = 0xe3, + SHT21_TRIG_RH_MEASUREMENT_HM = 0xe5, + SHT21_TRIG_T_MEASUREMENT_POLL = 0xf3, + SHT21_TRIG_RH_MEASUREMENT_POLL = 0xf5, + SHT21_USER_REG_W = 0xe6, + SHT21_USER_REG_R = 0xe7, + SHT21_SOFT_RESET = 0xfe +}; + +/* User register bit masks */ +enum sht21_userreg { + SHT21_RES_12_14BIT = 0x00, + SHT21_RES_8_12BIT = 0x01, + SHT21_RES_10_13BIT = 0x80, + SHT21_RES_11_11BIT = 0x81, + SHT21_RES_MASK = 0x81, + SHT21_END_OF_BATTERY = 0x40, + SHT21_ENABLE_HEATER = 0x04, + SHT21_WRITABLE_MASK = 0x87 +}; + +/* Types of measurements */ +enum sht21_measurement_index { + SHT21_TEMPERATURE, + SHT21_HUMIDITY, + SHT21_NUM_MEASUREMENTS +}; + +/** + * struct sht21 - SHT21 device specific data + * @hwmon_dev: device registered with hwmon + * @lock: mutex to ensure only one I2C transfer in progress at a time + * @userreg_orig: original value of user register + * @valid: !=0 if measurements are valid + * @last_update: time of last update (jiffies) + * @measurements: cached measurement values, temperature and humidity + */ +struct sht21 { + struct device *hwmon_dev; + struct mutex lock; + u8 userreg_orig; + char valid; + unsigned long last_update; + int measurements[SHT21_NUM_MEASUREMENTS]; +}; + +/* I2C command to be used for a specifc measurement */ +static u8 sht21_measurement_commands[SHT21_NUM_MEASUREMENTS] = { + SHT21_TRIG_T_MEASUREMENT_HM, + SHT21_TRIG_RH_MEASUREMENT_HM +}; + +/** + * sht21_temp_ticks_to_millicelsius() - convert raw temperature ticks to + * milli celsius + * @ticks: temperature ticks value received from sensor + */ +static int sht21_temp_ticks_to_millicelsius(int ticks) +{ + ticks &= ~0x0003; /* clear status bits */ + /* Formula T = -46.85 + 175.72 * ST / 2^16 from data sheet 6.2, + optimized for integer fixed point (3 digits) arithmetic */ + return ((21965 * ticks) >> 13) - 46850; +} + +/** + * sht21_rh_ticks_to_per_cent_mille() - convert raw humidity ticks to + * one-thousandths of a percent relative humidity + * @ticks: humidity ticks value received from sensor + */ +static int sht21_rh_ticks_to_per_cent_mille(int ticks) +{ + ticks &= ~0x0003; /* clear status bits */ + /* Formula RH = -6 + 125 * SRH / 2^16 from data sheet 6.1, + optimized for integer fixed point (3 digits) arithmetic */ + return ((15625 * ticks) >> 13) - 6000; +} + +typedef int (*convert_func)(int); + +/* Conversion function to be used for a specifc measurement */ +static convert_func sht21_convert_raw_value[SHT21_NUM_MEASUREMENTS] = { + sht21_temp_ticks_to_millicelsius, + sht21_rh_ticks_to_per_cent_mille +}; + +/** + * sht21_update_measurements() - get updated measurements from device + * @client: I2C client device + * + * Returns SHT21 client data containing measurements. + */ +static struct sht21 *sht21_update_measurements(struct i2c_client *client) +{ + struct sht21 *sht21 = i2c_get_clientdata(client); + + mutex_lock(&sht21->lock); + /* Data sheet 2.4: + * SHT2x should not be active for more than 10% of the time - e.g. maximum + * two measurements per second at 12bit accuracy shall be made. */ + if (time_after(jiffies, sht21->last_update + HZ / 2) || !sht21->valid) { + int meas_idx; + for (meas_idx = 0; meas_idx < SHT21_NUM_MEASUREMENTS; ++meas_idx) { + int result = i2c_smbus_read_word_data(client, + sht21_measurement_commands[meas_idx]); + /* SMBus specifies low byte first, but the SHT21 returns MSB first, + * so we have to swab16 the values */ + if (result >= 0) + sht21->measurements[meas_idx] = + sht21_convert_raw_value[meas_idx](swab16(result)); + } + sht21->last_update = jiffies; + sht21->valid = 1; + } + mutex_unlock(&sht21->lock); + + return sht21; +} + +/** + * sht21_show_measurement() - show measurement value in sysfs + * @dev: device + * @attr: device attribute + * @buf: sysfs buffer (PAGE_SIZE) where measurement values are written to + * + * Will be called on read access to a measurement sysfs attribute. + * Returns number of bytes written into buffer. + */ +static ssize_t sht21_show_measurement(struct device *dev, + struct device_attribute *attr, + char *buf) +{ + struct sensor_device_attribute *sda = to_sensor_dev_attr(attr); + struct sht21 *sht21 = sht21_update_measurements(to_i2c_client(dev)); + + return sprintf(buf, "%d\n", sht21->measurements[sda->index]); +} + +/** + * sht21_show_userreg() - show user register value in sysfs + * @dev: device + * @attr: device attribute + * @buf: sysfs buffer (PAGE_SIZE) where user register value is written to + * + * Will be called on read access to user_register sysfs attribute. + * Returns number of bytes written into buffer, -EIO on error. + */ +static ssize_t sht21_show_userreg(struct device *dev, + struct device_attribute *attr, + char *buf) +{ + struct i2c_client *client = to_i2c_client(dev); + struct sht21 *sht21 = i2c_get_clientdata(client); + int result; + mutex_lock(&sht21->lock); + result = i2c_smbus_read_byte_data(client, SHT21_USER_REG_R); + mutex_unlock(&sht21->lock); + + return result >= 0 ? sprintf(buf, "%d\n", result) : -EIO; +} + +/** + * sht21_store_userreg() - store sysfs value in user register + * @dev: device + * @attr: device attribute + * @buf: sysfs buffer containing value as string + * @count: number of characters in @buf + * + * Will be called on write access to user_register sysfs attribute. + * Returns @count, -EIO on error. + */ +static ssize_t sht21_store_userreg(struct device *dev, struct device_attribute *attr, + const char *buf, size_t count) +{ + struct i2c_client *client = to_i2c_client(dev); + struct sht21 *sht21 = i2c_get_clientdata(client); + int result; + char *endptr; + unsigned long value = simple_strtoul(buf, &endptr, 0); + if (endptr == buf || value > 0xff) + return -EINVAL; + + mutex_lock(&sht21->lock); + result = i2c_smbus_read_byte_data(client, SHT21_USER_REG_R); + if (result >= 0) + result = i2c_smbus_write_byte_data(client, SHT21_USER_REG_W, + (result & ~SHT21_WRITABLE_MASK) | (value & SHT21_WRITABLE_MASK)); + mutex_unlock(&sht21->lock); + + return result >= 0 ? count : -EIO; +} + +/* sysfs attributes */ +static SENSOR_DEVICE_ATTR(temp1_input, S_IRUGO, sht21_show_measurement, + NULL, SHT21_TEMPERATURE); +static SENSOR_DEVICE_ATTR(humidity1_input, S_IRUGO, sht21_show_measurement, + NULL, SHT21_HUMIDITY); +static SENSOR_DEVICE_ATTR(user_register, S_IRUGO | S_IWUSR, sht21_show_userreg, + sht21_store_userreg, 0); + +static struct attribute *sht21_attributes[] = { + &sensor_dev_attr_temp1_input.dev_attr.attr, + &sensor_dev_attr_humidity1_input.dev_attr.attr, + &sensor_dev_attr_user_register.dev_attr.attr, + NULL +}; + +static const struct attribute_group sht21_attr_group = { + .attrs = sht21_attributes, +}; + +/** + * sht21_probe() - probe device + * @client: I2C client device + * @id: device ID + * + * Called by the I2C core when an entry in the ID table matches a + * device's name. + * Returns 0 on success. + */ +static int __devinit sht21_probe(struct i2c_client *client, + const struct i2c_device_id *id) +{ + struct sht21 *sht21; + int status; + u8 userreg_changed; + + if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_WORD_DATA)) { + dev_err(&client->dev, "adapter does not support SMBus word transactions\n"); + return -ENODEV; + } + + sht21 = kzalloc(sizeof(*sht21), GFP_KERNEL); + if (!sht21) { + dev_dbg(&client->dev, "kzalloc failed\n"); + return -ENOMEM; + } + i2c_set_clientdata(client, sht21); + + status = i2c_smbus_read_byte_data(client, SHT21_USER_REG_R); + if (status < 0) { + dev_err(&client->dev, "error reading user register\n"); + goto fail_free; + } + sht21->userreg_orig = status; + + userreg_changed = status ^ SHT21_RES_MASK; + status = i2c_smbus_write_byte_data(client, SHT21_USER_REG_W, userreg_changed); + if (status < 0) { + dev_err(&client->dev, "error writing user register\n"); + goto fail_restore_config; + } + status = i2c_smbus_read_byte_data(client, SHT21_USER_REG_R); + if (status < 0) { + dev_err(&client->dev, "error reading user register\n"); + goto fail_restore_config; + } + if (status != userreg_changed) { + dev_err(&client->dev, "user register settings did not stick\n"); + status = -ENODEV; + goto fail_restore_config; + } + status = i2c_smbus_write_byte_data(client, SHT21_USER_REG_W, sht21->userreg_orig); + if (status < 0) { + dev_err(&client->dev, "error restoring user register\n"); + goto fail_restore_config; + } + sht21->last_update = jiffies - HZ; + mutex_init(&sht21->lock); + + status = sysfs_create_group(&client->dev.kobj, &sht21_attr_group); + if (status) { + dev_dbg(&client->dev, "could not create sysfs files\n"); + goto fail_restore_config; + } + sht21->hwmon_dev = hwmon_device_register(&client->dev); + if (IS_ERR(sht21->hwmon_dev)) { + dev_dbg(&client->dev, "unable to register hwmon device\n"); + status = PTR_ERR(sht21->hwmon_dev); + goto fail_remove_sysfs; + } + + dev_info(&client->dev, "initialized\n"); + + return 0; + +fail_remove_sysfs: + sysfs_remove_group(&client->dev.kobj, &sht21_attr_group); +fail_restore_config: + i2c_smbus_write_byte_data(client, SHT21_USER_REG_W, sht21->userreg_orig); +fail_free: + kfree(sht21); + + return status; +} + +/** + * sht21_remove() - remove device + * @client: I2C client device + */ +static int __devexit sht21_remove(struct i2c_client *client) +{ + struct sht21 *sht21 = i2c_get_clientdata(client); + int status; + + hwmon_device_unregister(sht21->hwmon_dev); + sysfs_remove_group(&client->dev.kobj, &sht21_attr_group); + + status = i2c_smbus_read_byte_data(client, SHT21_USER_REG_R); + if (status >= 0 && status != sht21->userreg_orig) { + i2c_smbus_write_byte_data(client, SHT21_USER_REG_W, sht21->userreg_orig); + } + + kfree(sht21); + + return 0; +} + +/* Device ID table */ +static const struct i2c_device_id sht21_id[] = { + { "sht21", 0 }, + { } +}; +MODULE_DEVICE_TABLE(i2c, sht21_id); + +static struct i2c_driver sht21_driver = { + .driver.name = "sht21", + .probe = sht21_probe, + .remove = __devexit_p(sht21_remove), + .id_table = sht21_id, +}; + +/** + * sht21_init() - initialize driver + * + * Called when kernel is booted or module is inserted. + * Returns 0 on success. + */ +static int __init sht21_init(void) +{ + return i2c_add_driver(&sht21_driver); +} +module_init(sht21_init); + +/** + * sht21_init() - clean up driver + * + * Called when module is removed. + */ +static void __exit sht21_exit(void) +{ + i2c_del_driver(&sht21_driver); +} +module_exit(sht21_exit); + +MODULE_AUTHOR("Urs Fleisch <urs.fleisch@sensirion.com>"); +MODULE_DESCRIPTION("Sensirion SHT21 humidity and temperature sensor driver"); +MODULE_LICENSE("GPL");
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