Re: [PATCH 05/16] hwmon: lm75: expose to thermal fw via DT nodes

This patch adds to lm75 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 lm75 DT node. Otherwise, the driver behavior
will be the same.

Cc: Jean Delvare <redacted>
Cc: Guenter Roeck <redacted>
Cc: lm-sensors-GZX6beZjE8VD60Wz+7aTrA@public.gmane.org
Cc: linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Signed-off-by: Eduardo Valentin <redacted>
---
  drivers/hwmon/lm75.c | 46 +++++++++++++++++++++++++++++++++++++++++-----
  1 file changed, 41 insertions(+), 5 deletions(-)

diff --git a/drivers/hwmon/lm75.c b/drivers/hwmon/lm75.c
index c03b490..2ba09ef 100644
--- a/drivers/hwmon/lm75.c
+++ b/drivers/hwmon/lm75.c

@@ -27,6 +27,8 @@
  #include <linux/hwmon-sysfs.h>
  #include <linux/err.h>
  #include <linux/mutex.h>
+#include <linux/of.h>
+#include <linux/thermal.h>
  #include "lm75.h"

@@ -70,6 +72,7 @@ static const u8 LM75_REG_TEMP[3] = {
  /* Each client has this additional data */
  struct lm75_data {
  	struct device		*hwmon_dev;
+	struct thermal_zone_device	*tz;
  	struct mutex		update_lock;
  	u8			orig_conf;
  	u8			resolution;	/* In bits, between 9 and 12 */

@@ -90,22 +93,42 @@ static struct lm75_data *lm75_update_device(struct device *dev);

  /*-----------------------------------------------------------------------*/

+static inline long lm75_reg_to_mc(s16 temp, u8 resolution)
+{
+	return ((temp >> (16 - resolution)) * 1000) >> (resolution - 8);
+}
+
  /* sysfs attributes for hwmon */

+static int lm75_read_temp(void *dev, long *temp)
+{
+	struct lm75_data *data = lm75_update_device(dev);
+	long temperature;
+
+	if (IS_ERR(data))
+		return PTR_ERR(data);
+
+	temperature = lm75_reg_to_mc(data->temp[0], data->resolution);
+	if (temperature < 0)
+		dev_warn(data->hwmon_dev,
+			 "operating in negative temp: %ld\n", temperature);

+
+	*temp = temperature;
+
+	return 0;
+}
+
  static ssize_t show_temp(struct device *dev, struct device_attribute *da,
  			 char *buf)
  {
  	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
  	struct lm75_data *data = lm75_update_device(dev);
-	long temp;

  	if (IS_ERR(data))
  		return PTR_ERR(data);

-	temp = ((data->temp[attr->index] >> (16 - data->resolution)) * 1000)
-	       >> (data->resolution - 8);
-
-	return sprintf(buf, "%ld\n", temp);
+	return sprintf(buf, "%ld\n", lm75_reg_to_mc(data->temp[attr->index],
+						    data->resolution));
  }

  static ssize_t set_temp(struct device *dev, struct device_attribute *da,

@@ -271,6 +294,17 @@ lm75_probe(struct i2c_client *client, const struct i2c_device_id *id)
  		goto exit_remove;
  	}

+	data->tz = thermal_zone_of_sensor_register(&client->dev,
+						   0,
+						   &client->dev,
+						   lm75_read_temp, NULL);
+	if (IS_ERR(data->tz)) {
+		dev_warn(&client->dev,
+			 "Could not parse thermal data in device tree: %ld\n",
+			 PTR_ERR(data->tz));
+		data->tz = NULL;
+	}
+
  	dev_info(&client->dev, "%s: sensor '%s'\n",
  		 dev_name(data->hwmon_dev), client->name);

@@ -285,6 +319,8 @@ static int lm75_remove(struct i2c_client *client)
  {
  	struct lm75_data *data = i2c_get_clientdata(client);

+	/* thermal zone life cycle is not our responsibility */
+	thermal_zone_of_sensor_unregister(&client->dev, data->tz);
  	hwmon_device_unregister(data->hwmon_dev);
  	sysfs_remove_group(&client->dev.kobj, &lm75_group);
  	lm75_write_value(client, LM75_REG_CONF, data->orig_conf);