[PATCH v2] hwmon: sht3x: add humidity heater element control

Matt Ranostay
2016-07-10T06:49:18Z

The enables control of the SHT31 sensors heating element that can turned
on to remove excess humidity.

Cc: Guenter Roeck <linux@roeck-us.net>
Cc: David Frey <david.frey@sensirion.com>
Signed-off-by: Matt Ranostay <mranostay@gmail.com>
---
Changes from v1:
* Remove useless mutex_lock on data
* Changed documentation to be more

Documentation/hwmon/sht3x | 4 ++++
drivers/hwmon/sht3x.c | 50 +++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 54 insertions(+)

diff --git a/Documentation/hwmon/sht3x b/Documentation/hwmon/sht3x
index f5aa633ed383..b0d88184f48e 100644
--- a/Documentation/hwmon/sht3x
+++ b/Documentation/hwmon/sht3x
@@ -67,6 +67,10 @@ temp1_alarm: alarm flag is set to 1 if the temperature is outside the
configured limits. Alarm only works in periodic measure mode
humidity1_alarm: alarm flag is set to 1 if the humidity is outside the
configured limits. Alarm only works in periodic measure mode
+heater_enable: heater enable, heating element removes excess humidity from
+ sensor
+ 0: turned off
+ 1: turned on
update_interval: update interval, 0 for single shot, interval in msec
for periodic measurement. If the interval is not supported
by the sensor, the next faster interval is chosen
diff --git a/drivers/hwmon/sht3x.c b/drivers/hwmon/sht3x.c
index b2c655add70e..e586fe9cb2b9 100644
--- a/drivers/hwmon/sht3x.c
+++ b/drivers/hwmon/sht3x.c
@@ -44,6 +44,10 @@ static const unsigned char sht3x_cmd_measure_nonblocking_lpm[] = { 0x24, 0x16 };
static const unsigned char sht3x_cmd_measure_periodic_mode[] = { 0xe0, 0x00 };
static const unsigned char sht3x_cmd_break[] = { 0x30, 0x93 };

+/* commands for heater control */
+static const unsigned char sht3x_cmd_heater_on[] = { 0x30, 0x6d };
+static const unsigned char sht3x_cmd_heater_off[] = { 0x30, 0x66 };
+
/* other commands */
static const unsigned char sht3x_cmd_read_status_reg[] = { 0xf3, 0x2d };
static const unsigned char sht3x_cmd_clear_status_reg[] = { 0x30, 0x41 };
@@ -507,6 +511,49 @@ static ssize_t humidity1_alarm_show(struct device *dev,
return scnprintf(buf, PAGE_SIZE, "%d\n", !!(buffer[0] & 0x08));
}

+static ssize_t heater_enable_show(struct device *dev,
+ struct device_attribute *attr,
+ char *buf)
+{
+ char buffer[SHT3X_WORD_LEN + SHT3X_CRC8_LEN];
+ int ret;
+
+ ret = status_register_read(dev, attr, buffer,
+ SHT3X_WORD_LEN + SHT3X_CRC8_LEN);
+ if (ret)
+ return ret;
+
+ return scnprintf(buf, PAGE_SIZE, "%d\n", !!(buffer[0] & 0x20));
+}
+
+static ssize_t heater_enable_store(struct device *dev,
+ struct device_attribute *attr,
+ const char *buf,
+ size_t count)
+{
+ struct sht3x_data *data = dev_get_drvdata(dev);
+ struct i2c_client *client = data->client;
+ int ret;
+ bool status;
+
+ ret = kstrtobool(buf, &status);
+ if (ret)
+ return ret;
+
+ mutex_lock(&data->i2c_lock);
+
+ if (status)
+ ret = i2c_master_send(client, (char *) &sht3x_cmd_heater_on,
+ SHT3X_CMD_LENGTH);
+ else
+ ret = i2c_master_send(client, (char *) &sht3x_cmd_heater_off,
+ SHT3X_CMD_LENGTH);
+
+ mutex_unlock(&data->i2c_lock);
+
+ return ret;
+}
+
static ssize_t update_interval_show(struct device *dev,
struct device_attribute *attr,
char *buf)
@@ -612,6 +659,8 @@ static SENSOR_DEVICE_ATTR(humidity1_min_hyst, S_IRUGO | S_IWUSR,
static SENSOR_DEVICE_ATTR(temp1_alarm, S_IRUGO, temp1_alarm_show, NULL, 0);
static SENSOR_DEVICE_ATTR(humidity1_alarm, S_IRUGO, humidity1_alarm_show,
NULL, 0);
+static SENSOR_DEVICE_ATTR(heater_enable, S_IRUGO | S_IWUSR,
+ heater_enable_show, heater_enable_store, 0);
static SENSOR_DEVICE_ATTR(update_interval, S_IRUGO | S_IWUSR,
update_interval_show, update_interval_store, 0);

@@ -628,6 +677,7 @@ static struct attribute *sht3x_attrs[] = {
&sensor_dev_attr_humidity1_min_hyst.dev_attr.attr,
&sensor_dev_attr_temp1_alarm.dev_attr.attr,
&sensor_dev_attr_humidity1_alarm.dev_attr.attr,
+ &sensor_dev_attr_heater_enable.dev_attr.attr,
&sensor_dev_attr_update_interval.dev_attr.attr,
NULL
};
--
2.7.4