hwmon: tmp102: expose to thermal fw via DT nodes

This patch adds to tmp102 temperature sensor the possibility
to expose itself as thermal zone device, registered on the
thermal framework.

The thermal zone is built only if a device tree node
describing a thermal zone for this sensor is present
inside the tmp102 DT node. Otherwise, the driver behavior
will be the same.

Note: This patch has also been reviewed by Jean D. He has
requested to perform a wider inspection of possible
users of thermal and hwmon interaction API. On the other
hand, the change on this patch is acceptable on first
step of overall code change.

Cc: Jean Delvare <khali@linux-fr.org>
Cc: lm-sensors@lm-sensors.org
Cc: linux-kernel@vger.kernel.org
Acked-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Eduardo Valentin <eduardo.valentin@ti.com>

drivers/hwmon/tmp102.c

@@ -27,6 +27,8 @@
 #include <linux/mutex.h>
 #include <linux/device.h>
 #include <linux/jiffies.h>
+#include <linux/thermal.h>
+#include <linux/of.h>
 
 #define	DRIVER_NAME "tmp102"
 
@@ -50,6 +52,7 @@
 
 struct tmp102 {
 	struct device *hwmon_dev;
+	struct thermal_zone_device *tz;
 	struct mutex lock;
 	u16 config_orig;
 	unsigned long last_update;
@@ -93,6 +96,15 @@ static struct tmp102 *tmp102_update_device(struct i2c_client *client)
 	return tmp102;
 }
 
+static int tmp102_read_temp(void *dev, long *temp)
+{
+	struct tmp102 *tmp102 = tmp102_update_device(to_i2c_client(dev));
+
+	*temp = tmp102->temp[0];
+
+	return 0;
+}
+
 static ssize_t tmp102_show_temp(struct device *dev,
 				struct device_attribute *attr,
 				char *buf)
@@ -204,6 +216,12 @@ static int tmp102_probe(struct i2c_client *client,
 		goto fail_remove_sysfs;
 	}
 
+	tmp102->tz = thermal_zone_of_sensor_register(&client->dev, 0,
+						     &client->dev,
+						     tmp102_read_temp, NULL);
+	if (IS_ERR(tmp102->tz))
+		tmp102->tz = NULL;
+
 	dev_info(&client->dev, "initialized\n");
 
 	return 0;
@@ -220,6 +238,7 @@ static int tmp102_remove(struct i2c_client *client)
 {
 	struct tmp102 *tmp102 = i2c_get_clientdata(client);
 
+	thermal_zone_of_sensor_unregister(&client->dev, tmp102->tz);
 	hwmon_device_unregister(tmp102->hwmon_dev);
 	sysfs_remove_group(&client->dev.kobj, &tmp102_attr_group);