hwmon: (sht3x) Add new non-stardard sysfs attribute

Add "repeatability" attribute to sysfs, it could be
read or written to control the sensor.

Signed-off-by: JuenKit Yip <JuenKit_Yip@hotmail.com>
Link: https://lore.kernel.org/r/DB4PR10MB6261B507C7656E3568DA33E39258A@DB4PR10MB6261.EURPRD10.PROD.OUTLOOK.COM
[groeck: Fixed multi-line alignment; dropped check of unsigned against < 0]
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

Documentation/hwmon/sht3x.rst

@@ -28,11 +28,6 @@ The device communicates with the I2C protocol. Sensors can have the I2C
 addresses 0x44 or 0x45, depending on the wiring. See
 Documentation/i2c/instantiating-devices.rst for methods to instantiate the device.
 
-There is only one option configurable by means of sht3x_data:
-
-   repeatability: high repeatability is used by default and using it is
-   strongly recommended.
-
 Even if sht3x sensor supports clock-strech(blocking mode) and non-strench
 (non-blocking mode) in single-shot mode, this driver only supports the latter.
 
@@ -83,4 +78,11 @@ heater_enable:      heater enable, heating element removes excess humidity from
 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
+repeatability:      write or read repeatability, higher repeatability means
+                    longer measurement duration, lower noise level and
+                    larger energy consumption:
+
+                        - 0: low repeatability
+                        - 1: medium repeatability
+                        - 2: high repeatability
 =================== ============================================================

drivers/hwmon/sht3x.c

@@ -637,6 +637,37 @@ out:
 	return count;
 }
 
+static ssize_t repeatability_show(struct device *dev,
+				  struct device_attribute *attr,
+				  char *buf)
+{
+	struct sht3x_data *data = dev_get_drvdata(dev);
+
+	return sysfs_emit(buf, "%d\n", data->repeatability);
+}
+
+static ssize_t repeatability_store(struct device *dev,
+				   struct device_attribute *attr,
+				   const char *buf,
+				   size_t count)
+{
+	int ret;
+	u8 val;
+
+	struct sht3x_data *data = dev_get_drvdata(dev);
+
+	ret = kstrtou8(buf, 0, &val);
+	if (ret)
+		return ret;
+
+	if (val > 2)
+		return -EINVAL;
+
+	data->repeatability = val;
+
+	return count;
+}
+
 static SENSOR_DEVICE_ATTR_RO(temp1_input, temp1_input, 0);
 static SENSOR_DEVICE_ATTR_RO(humidity1_input, humidity1_input, 0);
 static SENSOR_DEVICE_ATTR_RW(temp1_max, temp1_limit, limit_max);
@@ -653,6 +684,7 @@ static SENSOR_DEVICE_ATTR_RO(temp1_alarm, temp1_alarm, 0);
 static SENSOR_DEVICE_ATTR_RO(humidity1_alarm, humidity1_alarm, 0);
 static SENSOR_DEVICE_ATTR_RW(heater_enable, heater_enable, 0);
 static SENSOR_DEVICE_ATTR_RW(update_interval, update_interval, 0);
+static SENSOR_DEVICE_ATTR_RW(repeatability, repeatability, 0);
 
 static struct attribute *sht3x_attrs[] = {
 	&sensor_dev_attr_temp1_input.dev_attr.attr,
@@ -669,6 +701,7 @@ static struct attribute *sht3x_attrs[] = {
 	&sensor_dev_attr_humidity1_alarm.dev_attr.attr,
 	&sensor_dev_attr_heater_enable.dev_attr.attr,
 	&sensor_dev_attr_update_interval.dev_attr.attr,
+	&sensor_dev_attr_repeatability.dev_attr.attr,
 	NULL
 };