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Date: Thu, 29 Aug 2013 20:35:13 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: "Markezana, William" <William.Markezana@...s-spec.com>
CC: khali@...ux-fr.org, lm-sensors@...sensors.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH] hwmon: (htu21) Add Measurement Specialties HTU21D support
On 08/29/2013 04:51 AM, Markezana, William wrote:
> From: William Markezana <william.markezana@...s-spec.com>
>
> hwmon: (htu21) Add Measurement Specialties HTU21D support
> Signed-off-by: William Markezana <william.markezana@...s-spec.com>
> ---
Applied [ with minor formatting changes ] to -next.
Thanks,
Guenter
> diff --git a/Documentation/hwmon/htu21 b/Documentation/hwmon/htu21
> new file mode 100644
> index 0000000..8082879
> --- /dev/null
> +++ b/Documentation/hwmon/htu21
> @@ -0,0 +1,46 @@
> +Kernel driver htu21
> +===================
> +
> +Supported chips:
> + * Measurement Specialties HTU21D
> + Prefix: 'htu21'
> + Addresses scanned: none
> + Datasheet: Publicly available at the Measurement Specialties website
> + http://www.meas-spec.com/downloads/HTU21D.pdf
> +
> +
> +Author:
> + William Markezana <william.markezana@...s-spec.com>
> +
> +Description
> +-----------
> +
> +The HTU21D is a humidity and temperature sensor in a DFN package of
> +only 3 x 3 mm footprint and 0.9 mm height.
> +
> +The devices communicate with the I2C protocol. All sensors are set to the
> +same I2C address 0x40, so an entry with I2C_BOARD_INFO("htu21", 0x40) can
> +be used in the board setup code.
> +
> +This driver does not auto-detect devices. You will have to instantiate the
> +devices explicitly. Please see Documentation/i2c/instantiating-devices
> +for details."
> +
> +sysfs-Interface
> +---------------
> +
> +temp1_input - temperature input
> +humidity1_input - humidity input
> +
> +Notes
> +-----
> +
> +The driver uses the default resolution settings of 12 bit for humidity and 14
> +bit for temperature, which results in typical measurement times of 11 ms for
> +humidity and 44 ms for temperature. To keep self heating below 0.1 degree
> +Celsius, the device should not be active for more than 10% of the time. For
> +this reason, the driver performs no more than two measurements per second and
> +reports cached information if polled more frequently.
> +
> +Different resolutions, the on-chip heater, using the CRC checksum and reading
> +the serial number are not supported yet.
> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> index e989f7f..55973cd 100644
> --- a/drivers/hwmon/Kconfig
> +++ b/drivers/hwmon/Kconfig
> @@ -511,6 +511,16 @@ config SENSORS_HIH6130
> This driver can also be built as a module. If so, the module
> will be called hih6130.
>
> +config SENSORS_HTU21
> + tristate "Measurement Specialties HTU21D humidity/temperature sensors"
> + depends on I2C
> + help
> + If you say yes here you get support for the Measurement Specialties
> + HTU21D humidity and temperature sensors.
> +
> + This driver can also be built as a module. If so, the module
> + will be called htu21.
> +
> config SENSORS_CORETEMP
> tristate "Intel Core/Core2/Atom temperature sensor"
> depends on X86
> diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
> index 4f0fb52..ec7cde0 100644
> --- a/drivers/hwmon/Makefile
> +++ b/drivers/hwmon/Makefile
> @@ -65,6 +65,7 @@ obj-$(CONFIG_SENSORS_GL518SM) += gl518sm.o
> obj-$(CONFIG_SENSORS_GL520SM) += gl520sm.o
> obj-$(CONFIG_SENSORS_GPIO_FAN) += gpio-fan.o
> obj-$(CONFIG_SENSORS_HIH6130) += hih6130.o
> +obj-$(CONFIG_SENSORS_HTU21) += htu21.o
> obj-$(CONFIG_SENSORS_ULTRA45) += ultra45_env.o
> obj-$(CONFIG_SENSORS_I5K_AMB) += i5k_amb.o
> obj-$(CONFIG_SENSORS_IBMAEM) += ibmaem.o
> diff --git a/drivers/hwmon/htu21.c b/drivers/hwmon/htu21.c
> new file mode 100644
> index 0000000..743bf32
> --- /dev/null
> +++ b/drivers/hwmon/htu21.c
> @@ -0,0 +1,201 @@
> +/*
> + * Measurement Specialties HTU21D humidity and temperature sensor driver
> + *
> + * Copyright (C) 2013 William Markezana <william.markezana@...s-spec.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.
> + *
> + */
> +
> +#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>
> +#include <linux/jiffies.h>
> +
> +/* HTU21 Commands */
> +#define HTU21_T_MEASUREMENT_HM 0xE3
> +#define HTU21_RH_MEASUREMENT_HM 0xE5
> +
> +struct htu21 {
> + struct device *hwmon_dev;
> + struct mutex lock;
> + bool valid;
> + unsigned long last_update;
> + int temperature;
> + int humidity;
> +};
> +
> +static inline int htu21_temp_ticks_to_millicelsius(int ticks)
> +{
> + ticks &= ~0x0003; /* clear status bits */
> + /*
> + * Formula T = -46.85 + 175.72 * ST / 2^16 from datasheet p14,
> + * optimized for integer fixed point (3 digits) arithmetic
> + */
> + return ((21965 * ticks) >> 13) - 46850;
> +}
> +
> +static inline int htu21_rh_ticks_to_per_cent_mille(int ticks)
> +{
> + ticks &= ~0x0003; /* clear status bits */
> + /*
> + * Formula RH = -6 + 125 * SRH / 2^16 from datasheet p14,
> + * optimized for integer fixed point (3 digits) arithmetic
> + */
> + return ((15625 * ticks) >> 13) - 6000;
> +}
> +
> +static int htu21_update_measurements(struct i2c_client *client)
> +{
> + int ret = 0;
> + struct htu21 *htu21 = i2c_get_clientdata(client);
> +
> + mutex_lock(&htu21->lock);
> +
> + if (time_after(jiffies, htu21->last_update + HZ / 2) ||
> + !htu21->valid) {
> + ret = i2c_smbus_read_word_swapped(client,
> + HTU21_T_MEASUREMENT_HM);
> + if (ret < 0)
> + goto out;
> + htu21->temperature = htu21_temp_ticks_to_millicelsius(ret);
> + ret = i2c_smbus_read_word_swapped(client,
> + HTU21_RH_MEASUREMENT_HM);
> + if (ret < 0)
> + goto out;
> + htu21->humidity = htu21_rh_ticks_to_per_cent_mille(ret);
> + htu21->last_update = jiffies;
> + htu21->valid = true;
> + }
> +out:
> + mutex_unlock(&htu21->lock);
> +
> + return ret >= 0 ? 0 : ret;
> +}
> +
> +static ssize_t htu21_show_temperature(struct device *dev,
> + struct device_attribute *attr,
> + char *buf)
> +{
> + struct i2c_client *client = to_i2c_client(dev);
> + struct htu21 *htu21 = i2c_get_clientdata(client);
> + int ret = htu21_update_measurements(client);
> + if (ret < 0)
> + return ret;
> + return sprintf(buf, "%d\n", htu21->temperature);
> +}
> +
> +static ssize_t htu21_show_humidity(struct device *dev,
> + struct device_attribute *attr,
> + char *buf)
> +{
> + struct i2c_client *client = to_i2c_client(dev);
> + struct htu21 *htu21 = i2c_get_clientdata(client);
> + int ret = htu21_update_measurements(client);
> + if (ret < 0)
> + return ret;
> + return sprintf(buf, "%d\n", htu21->humidity);
> +}
> +
> +static SENSOR_DEVICE_ATTR(temp1_input, S_IRUGO,
> + htu21_show_temperature, NULL, 0);
> +static SENSOR_DEVICE_ATTR(humidity1_input, S_IRUGO,
> + htu21_show_humidity, NULL, 0);
> +
> +static struct attribute *htu21_attributes[] = {
> + &sensor_dev_attr_temp1_input.dev_attr.attr,
> + &sensor_dev_attr_humidity1_input.dev_attr.attr,
> + NULL
> +};
> +
> +static const struct attribute_group htu21_group = {
> + .attrs = htu21_attributes,
> +};
> +
> +static int htu21_probe(struct i2c_client *client,
> + const struct i2c_device_id *id)
> +{
> + struct htu21 *htu21;
> + int err;
> +
> + if (!i2c_check_functionality(client->adapter,
> + I2C_FUNC_SMBUS_READ_WORD_DATA)) {
> + dev_err(&client->dev,
> + "adapter does not support SMBus word transactions\n");
> + return -ENODEV;
> + }
> +
> + htu21 = devm_kzalloc(&client->dev, sizeof(*htu21), GFP_KERNEL);
> + if (!htu21)
> + return -ENOMEM;
> +
> + i2c_set_clientdata(client, htu21);
> +
> + mutex_init(&htu21->lock);
> +
> + err = sysfs_create_group(&client->dev.kobj, &htu21_group);
> + if (err) {
> + dev_dbg(&client->dev, "could not create sysfs files\n");
> + return err;
> + }
> + htu21->hwmon_dev = hwmon_device_register(&client->dev);
> + if (IS_ERR(htu21->hwmon_dev)) {
> + dev_dbg(&client->dev, "unable to register hwmon device\n");
> + err = PTR_ERR(htu21->hwmon_dev);
> + goto error;
> + }
> +
> + dev_info(&client->dev, "initialized\n");
> +
> + return 0;
> +
> +error:
> + sysfs_remove_group(&client->dev.kobj, &htu21_group);
> + return err;
> +}
> +
> +static int htu21_remove(struct i2c_client *client)
> +{
> + struct htu21 *htu21 = i2c_get_clientdata(client);
> +
> + hwmon_device_unregister(htu21->hwmon_dev);
> + sysfs_remove_group(&client->dev.kobj, &htu21_group);
> +
> + return 0;
> +}
> +
> +static const struct i2c_device_id htu21_id[] = {
> + { "htu21", 0 },
> + { }
> +};
> +MODULE_DEVICE_TABLE(i2c, htu21_id);
> +
> +static struct i2c_driver htu21_driver = {
> + .class = I2C_CLASS_HWMON,
> + .driver = {
> + .name = "htu21",
> + },
> + .probe = htu21_probe,
> + .remove = htu21_remove,
> + .id_table = htu21_id,
> +};
> +
> +module_i2c_driver(htu21_driver);
> +
> +MODULE_AUTHOR("William Markezana <william.markezana@...s-spec.com>");
> +MODULE_DESCRIPTION("MEAS HTU21D humidity and temperature sensor driver");
> +MODULE_LICENSE("GPL");
>
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