Re: [PATCH 7/9] hwmon: Support registration of thermal zones for SCP temperature sensors

Hi Guenter,

Guenter Roeck [off-list ref] writes:

On 07/22/2015 07:02 AM, Punit Agrawal wrote:

quoted

Add support to create thermal zones based on the temperature sensors
provided by the SCP. The thermal zones can be defined using the
thermal DT bindings and should refer to the SCP sensor id to select
the sensor.

Signed-off-by: Punit Agrawal <redacted>
Cc: Jean Delvare <redacted>
Cc: Guenter Roeck <redacted>
Cc: Eduardo Valentin <redacted>
---
  drivers/hwmon/scpi-hwmon.c | 53 ++++++++++++++++++++++++++++++++++++++++++++++
  1 file changed, 53 insertions(+)

diff --git a/drivers/hwmon/scpi-hwmon.c b/drivers/hwmon/scpi-hwmon.c
index dd0a6f1..1e52ced 100644
--- a/drivers/hwmon/scpi-hwmon.c
+++ b/drivers/hwmon/scpi-hwmon.c

[...]

quoted

@@ -54,6 +61,20 @@ static int scpi_read_sensor(struct sensor_dev *sensor, u32 *value)
  	return 0;
  }

+static int scpi_read_temp(void *dev, long *temp)
+{
+	struct sensor_dev *sensor = dev;
+	u32 value;
+	int ret;
+
+	ret = scpi_read_sensor(sensor, &value);
+	if (ret)
+		return ret;
+
+	*temp = value;
+	return 0;
+}
+
  /* hwmon callback functions */
  static ssize_t
  scpi_hwmon_show_sensor(struct device *dev,

@@ -90,6 +111,10 @@ struct attribute *scpi_attrs[24] = { 0 };
  struct attribute_group scpi_group;
  const struct attribute_group *scpi_groups[2] = { 0 };

+struct thermal_zone_of_device_ops scpi_sensor_ops = {

static struct ...

Updated.

quoted

+	.get_temp = scpi_read_temp,
+};
+
  static int scpi_hwmon_probe(struct platform_device *pdev)
  {
  	u16 sensors, i;

@@ -108,9 +133,12 @@ static int scpi_hwmon_probe(struct platform_device *pdev)
  	if (!scpi_sensors.device)
  		return -ENOMEM;

+	INIT_LIST_HEAD(&scpi_sensors.thermal_zones);
+
  	dev_info(&pdev->dev, "Found %d sensors\n", sensors);
  	for (i = 0; i < sensors; i++) {
  		struct sensor_dev *dev = &scpi_sensors.device[i];
+		struct scpi_thermal_zone *zone;

  		ret = scpi_ops->sensor_get_info(i, &dev->info);
  		if (ret) {

@@ -130,6 +158,20 @@ static int scpi_hwmon_probe(struct platform_device *pdev)
  			snprintf(dev->label, 20,
  				 "temp%d_label", scpi_sensors.num_temp);
  			scpi_sensors.num_temp++;
+
+			zone = devm_kmalloc(&pdev->dev, sizeof(*zone),
+					    GFP_KERNEL);

Please consider using devm_kzalloc().

Done

quoted

+			if (!zone)
+				return -ENOMEM;
+
+			zone->tzd = thermal_zone_of_sensor_register(&pdev->dev,
+						    i, dev, &scpi_sensor_ops);
+			if (!IS_ERR(zone->tzd))
+				list_add(&zone->list,
+					 &scpi_sensors.thermal_zones);
+			else
+				devm_kfree(&pdev->dev, zone);
+

I would prefer

			if (IS_ERR_OR_NULL(zone->tzd)) {
				devm_kfree(&pdev->dev, zone);
				break;
			}
			list_add(&zone->list, &scpi_sensors.thermal_zones);

The code has a problem, though: You don't clean up thermal zones if
there is an error later on in the probe function. Either you need to
implement a cleanup function to be called from an error handler (and
from the remove function), or you need to wait with registering
thermal zones to the very end of the probe function.

I've re-factored to register the sensors at the end of the probe.

Note that thermal_zone_of_sensor_register can return NULL if thermal
zones are not configured, so you have to use IS_ERR_OR_NULL
when checking for errors.

You're right. I missed the NULL return when THERMAL_OF is configured
off. This doesn't match the documentation at the top of the function in
drivers/thermal/of-thermal.c

 * Return: On success returns a valid struct thermal_zone_device,
 * otherwise, it returns a corresponding ERR_PTR(). Caller must
 * check the return value with help of IS_ERR() helper.

Usage of thermal_zone_of_sensor_register in other drivers matches the above
doc. I'll include a patch fixing the NULL return with the next version.

quoted

  			break;
  		case VOLTAGE:
  			snprintf(dev->input, 20,

@@ -187,7 +229,18 @@ static int scpi_hwmon_probe(struct platform_device *pdev)

  static int scpi_hwmon_remove(struct platform_device *pdev)
  {
+	struct list_head *pos;
+
  	scpi_ops = NULL;
+
+	list_for_each(pos, &scpi_sensors.thermal_zones) {
+		struct scpi_thermal_zone *zone;
+
+		zone = list_entry(pos, struct scpi_thermal_zone, list);
+		thermal_zone_of_sensor_unregister(scpi_sensors.hwdev,

Not sure how this can work. The registration was with &pdev->dev,
not with hwdev. What happens if you actually unload this driver ?

Thanks for catching this! I'll fix this in the next version.

I had tested unloading the driver and didn't notice any adverse
ill-effects. Although thermal_zone_of_sensor_unregister expects a
pointer to a device, other then checking for non-NULLness, it doesn't do
anything with it.

Perhaps, this argument should be dropped from the function. If the
thermal maintainers agree I can cook up a patch. Eduardo?

Thanks,
Punit

quoted

+						  zone->tzd);
+	}
+
  	return 0;
  }

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