Re: [PATCH] hwmon: (htu21) Add Measurement Specialties HTU21D support

[Guenter Roeck]

On 08/29/2013 04:51 AM, Markezana, William wrote:
> From: William Markezana <william.markezana@xxxxxxxxxxxxx>
>
> hwmon: (htu21) Add Measurement Specialties HTU21D support
> Signed-off-by: William Markezana <william.markezana@xxxxxxxxxxxxx>
> ---

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@xxxxxxxxxxxxx>
> +
> +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@xxxxxxxxxxxxx>
> + *
> + * 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@xxxxxxxxxxxxx>");
> +MODULE_DESCRIPTION("MEAS HTU21D humidity and temperature sensor driver");
> +MODULE_LICENSE("GPL");

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