diff options
Diffstat (limited to 'drivers/hwmon/shtc1.c')
| -rw-r--r-- | drivers/hwmon/shtc1.c | 251 |
1 files changed, 251 insertions, 0 deletions
diff --git a/drivers/hwmon/shtc1.c b/drivers/hwmon/shtc1.c new file mode 100644 index 000000000..2a1853959 --- /dev/null +++ b/drivers/hwmon/shtc1.c @@ -0,0 +1,251 @@ +/* Sensirion SHTC1 humidity and temperature sensor driver + * + * Copyright (C) 2014 Sensirion AG, Switzerland + * Author: Johannes Winkelmann <johannes.winkelmann@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. + * + */ + +#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/delay.h> +#include <linux/platform_data/shtc1.h> + +/* commands (high precision mode) */ +static const unsigned char shtc1_cmd_measure_blocking_hpm[] = { 0x7C, 0xA2 }; +static const unsigned char shtc1_cmd_measure_nonblocking_hpm[] = { 0x78, 0x66 }; + +/* commands (low precision mode) */ +static const unsigned char shtc1_cmd_measure_blocking_lpm[] = { 0x64, 0x58 }; +static const unsigned char shtc1_cmd_measure_nonblocking_lpm[] = { 0x60, 0x9c }; + +/* command for reading the ID register */ +static const unsigned char shtc1_cmd_read_id_reg[] = { 0xef, 0xc8 }; + +/* constants for reading the ID register */ +#define SHTC1_ID 0x07 +#define SHTC1_ID_REG_MASK 0x3f + +/* delays for non-blocking i2c commands, both in us */ +#define SHTC1_NONBLOCKING_WAIT_TIME_HPM 14400 +#define SHTC1_NONBLOCKING_WAIT_TIME_LPM 1000 + +#define SHTC1_CMD_LENGTH 2 +#define SHTC1_RESPONSE_LENGTH 6 + +struct shtc1_data { + struct i2c_client *client; + struct mutex update_lock; + bool valid; + unsigned long last_updated; /* in jiffies */ + + const unsigned char *command; + unsigned int nonblocking_wait_time; /* in us */ + + struct shtc1_platform_data setup; + + int temperature; /* 1000 * temperature in dgr C */ + int humidity; /* 1000 * relative humidity in %RH */ +}; + +static int shtc1_update_values(struct i2c_client *client, + struct shtc1_data *data, + char *buf, int bufsize) +{ + int ret = i2c_master_send(client, data->command, SHTC1_CMD_LENGTH); + if (ret != SHTC1_CMD_LENGTH) { + dev_err(&client->dev, "failed to send command: %d\n", ret); + return ret < 0 ? ret : -EIO; + } + + /* + * In blocking mode (clock stretching mode) the I2C bus + * is blocked for other traffic, thus the call to i2c_master_recv() + * will wait until the data is ready. For non blocking mode, we + * have to wait ourselves. + */ + if (!data->setup.blocking_io) + usleep_range(data->nonblocking_wait_time, + data->nonblocking_wait_time + 1000); + + ret = i2c_master_recv(client, buf, bufsize); + if (ret != bufsize) { + dev_err(&client->dev, "failed to read values: %d\n", ret); + return ret < 0 ? ret : -EIO; + } + + return 0; +} + +/* sysfs attributes */ +static struct shtc1_data *shtc1_update_client(struct device *dev) +{ + struct shtc1_data *data = dev_get_drvdata(dev); + struct i2c_client *client = data->client; + unsigned char buf[SHTC1_RESPONSE_LENGTH]; + int val; + int ret = 0; + + mutex_lock(&data->update_lock); + + if (time_after(jiffies, data->last_updated + HZ / 10) || !data->valid) { + ret = shtc1_update_values(client, data, buf, sizeof(buf)); + if (ret) + goto out; + + /* + * From datasheet: + * T = -45 + 175 * ST / 2^16 + * RH = 100 * SRH / 2^16 + * + * Adapted for integer fixed point (3 digit) arithmetic. + */ + val = be16_to_cpup((__be16 *)buf); + data->temperature = ((21875 * val) >> 13) - 45000; + val = be16_to_cpup((__be16 *)(buf + 3)); + data->humidity = ((12500 * val) >> 13); + + data->last_updated = jiffies; + data->valid = true; + } + +out: + mutex_unlock(&data->update_lock); + + return ret == 0 ? data : ERR_PTR(ret); +} + +static ssize_t temp1_input_show(struct device *dev, + struct device_attribute *attr, + char *buf) +{ + struct shtc1_data *data = shtc1_update_client(dev); + if (IS_ERR(data)) + return PTR_ERR(data); + + return sprintf(buf, "%d\n", data->temperature); +} + +static ssize_t humidity1_input_show(struct device *dev, + struct device_attribute *attr, char *buf) +{ + struct shtc1_data *data = shtc1_update_client(dev); + if (IS_ERR(data)) + return PTR_ERR(data); + + return sprintf(buf, "%d\n", data->humidity); +} + +static DEVICE_ATTR_RO(temp1_input); +static DEVICE_ATTR_RO(humidity1_input); + +static struct attribute *shtc1_attrs[] = { + &dev_attr_temp1_input.attr, + &dev_attr_humidity1_input.attr, + NULL +}; + +ATTRIBUTE_GROUPS(shtc1); + +static void shtc1_select_command(struct shtc1_data *data) +{ + if (data->setup.high_precision) { + data->command = data->setup.blocking_io ? + shtc1_cmd_measure_blocking_hpm : + shtc1_cmd_measure_nonblocking_hpm; + data->nonblocking_wait_time = SHTC1_NONBLOCKING_WAIT_TIME_HPM; + + } else { + data->command = data->setup.blocking_io ? + shtc1_cmd_measure_blocking_lpm : + shtc1_cmd_measure_nonblocking_lpm; + data->nonblocking_wait_time = SHTC1_NONBLOCKING_WAIT_TIME_LPM; + } +} + +static int shtc1_probe(struct i2c_client *client, + const struct i2c_device_id *id) +{ + int ret; + char id_reg[2]; + struct shtc1_data *data; + struct device *hwmon_dev; + struct i2c_adapter *adap = client->adapter; + struct device *dev = &client->dev; + + if (!i2c_check_functionality(adap, I2C_FUNC_I2C)) { + dev_err(dev, "plain i2c transactions not supported\n"); + return -ENODEV; + } + + ret = i2c_master_send(client, shtc1_cmd_read_id_reg, SHTC1_CMD_LENGTH); + if (ret != SHTC1_CMD_LENGTH) { + dev_err(dev, "could not send read_id_reg command: %d\n", ret); + return ret < 0 ? ret : -ENODEV; + } + ret = i2c_master_recv(client, id_reg, sizeof(id_reg)); + if (ret != sizeof(id_reg)) { + dev_err(dev, "could not read ID register: %d\n", ret); + return -ENODEV; + } + if ((id_reg[1] & SHTC1_ID_REG_MASK) != SHTC1_ID) { + dev_err(dev, "ID register doesn't match\n"); + return -ENODEV; + } + + data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL); + if (!data) + return -ENOMEM; + + data->setup.blocking_io = false; + data->setup.high_precision = true; + data->client = client; + + if (client->dev.platform_data) + data->setup = *(struct shtc1_platform_data *)dev->platform_data; + shtc1_select_command(data); + mutex_init(&data->update_lock); + + hwmon_dev = devm_hwmon_device_register_with_groups(dev, + client->name, + data, + shtc1_groups); + if (IS_ERR(hwmon_dev)) + dev_dbg(dev, "unable to register hwmon device\n"); + + return PTR_ERR_OR_ZERO(hwmon_dev); +} + +/* device ID table */ +static const struct i2c_device_id shtc1_id[] = { + { "shtc1", 0 }, + { "shtw1", 0 }, + { } +}; +MODULE_DEVICE_TABLE(i2c, shtc1_id); + +static struct i2c_driver shtc1_i2c_driver = { + .driver.name = "shtc1", + .probe = shtc1_probe, + .id_table = shtc1_id, +}; + +module_i2c_driver(shtc1_i2c_driver); + +MODULE_AUTHOR("Johannes Winkelmann <johannes.winkelmann@sensirion.com>"); +MODULE_DESCRIPTION("Sensirion SHTC1 humidity and temperature sensor driver"); +MODULE_LICENSE("GPL"); |