platform/x86: dell-ddv: Use the power supply extension mechanism

Use the power supply extension mechanism for registering the battery
temperature properties so that they can show up in the hwmon device
associated with the ACPI battery.

Signed-off-by: Armin Wolf <W_Armin@gmx.de>
Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Link: https://lore.kernel.org/r/20250305053009.378609-4-W_Armin@gmx.de
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>

Author: Wer-Wolf

drivers/platform/x86/dell/dell-wmi-ddv.c

@@ -104,7 +104,6 @@ struct dell_wmi_ddv_sensors {
 
 struct dell_wmi_ddv_data {
 	struct acpi_battery_hook hook;
-	struct device_attribute temp_attr;
 	struct device_attribute eppid_attr;
 	struct dell_wmi_ddv_sensors fans;
 	struct dell_wmi_ddv_sensors temps;
@@ -651,26 +650,6 @@ static int dell_wmi_ddv_battery_index(struct acpi_device *acpi_dev, u32 *index)
 	return kstrtou32(uid_str, 10, index);
 }
 
-static ssize_t temp_show(struct device *dev, struct device_attribute *attr, char *buf)
-{
-	struct dell_wmi_ddv_data *data = container_of(attr, struct dell_wmi_ddv_data, temp_attr);
-	u32 index, value;
-	int ret;
-
-	ret = dell_wmi_ddv_battery_index(to_acpi_device(dev->parent), &index);
-	if (ret < 0)
-		return ret;
-
-	ret = dell_wmi_ddv_query_integer(data->wdev, DELL_DDV_BATTERY_TEMPERATURE, index, &value);
-	if (ret < 0)
-		return ret;
-
-	/* Use 2732 instead of 2731.5 to avoid unnecessary rounding and to emulate
-	 * the behaviour of the OEM application which seems to round down the result.
-	 */
-	return sysfs_emit(buf, "%d\n", value - 2732);
-}
-
 static ssize_t eppid_show(struct device *dev, struct device_attribute *attr, char *buf)
 {
 	struct dell_wmi_ddv_data *data = container_of(attr, struct dell_wmi_ddv_data, eppid_attr);
@@ -697,6 +676,46 @@ static ssize_t eppid_show(struct device *dev, struct device_attribute *attr, cha
 	return ret;
 }
 
+static int dell_wmi_ddv_get_property(struct power_supply *psy, const struct power_supply_ext *ext,
+				     void *drvdata, enum power_supply_property psp,
+				     union power_supply_propval *val)
+{
+	struct dell_wmi_ddv_data *data = drvdata;
+	u32 index, value;
+	int ret;
+
+	ret = dell_wmi_ddv_battery_index(to_acpi_device(psy->dev.parent), &index);
+	if (ret < 0)
+		return ret;
+
+	switch (psp) {
+	case POWER_SUPPLY_PROP_TEMP:
+		ret = dell_wmi_ddv_query_integer(data->wdev, DELL_DDV_BATTERY_TEMPERATURE, index,
+						 &value);
+		if (ret < 0)
+			return ret;
+
+		/* Use 2732 instead of 2731.5 to avoid unnecessary rounding and to emulate
+		 * the behaviour of the OEM application which seems to round down the result.
+		 */
+		val->intval = value - 2732;
+		return 0;
+	default:
+		return -EINVAL;
+	}
+}
+
+static const enum power_supply_property dell_wmi_ddv_properties[] = {
+	POWER_SUPPLY_PROP_TEMP,
+};
+
+static const struct power_supply_ext dell_wmi_ddv_extension = {
+	.name = DRIVER_NAME,
+	.properties = dell_wmi_ddv_properties,
+	.num_properties = ARRAY_SIZE(dell_wmi_ddv_properties),
+	.get_property = dell_wmi_ddv_get_property,
+};
+
 static int dell_wmi_ddv_add_battery(struct power_supply *battery, struct acpi_battery_hook *hook)
 {
 	struct dell_wmi_ddv_data *data = container_of(hook, struct dell_wmi_ddv_data, hook);
@@ -708,13 +727,14 @@ static int dell_wmi_ddv_add_battery(struct power_supply *battery, struct acpi_ba
 	if (ret < 0)
 		return 0;
 
-	ret = device_create_file(&battery->dev, &data->temp_attr);
+	ret = device_create_file(&battery->dev, &data->eppid_attr);
 	if (ret < 0)
 		return ret;
 
-	ret = device_create_file(&battery->dev, &data->eppid_attr);
+	ret = power_supply_register_extension(battery, &dell_wmi_ddv_extension, &data->wdev->dev,
+					      data);
 	if (ret < 0) {
-		device_remove_file(&battery->dev, &data->temp_attr);
+		device_remove_file(&battery->dev, &data->eppid_attr);
 
 		return ret;
 	}
@@ -726,8 +746,8 @@ static int dell_wmi_ddv_remove_battery(struct power_supply *battery, struct acpi
 {
 	struct dell_wmi_ddv_data *data = container_of(hook, struct dell_wmi_ddv_data, hook);
 
-	device_remove_file(&battery->dev, &data->temp_attr);
 	device_remove_file(&battery->dev, &data->eppid_attr);
+	power_supply_unregister_extension(battery, &dell_wmi_ddv_extension);
 
 	return 0;
 }
@@ -738,11 +758,6 @@ static int dell_wmi_ddv_battery_add(struct dell_wmi_ddv_data *data)
 	data->hook.add_battery = dell_wmi_ddv_add_battery;
 	data->hook.remove_battery = dell_wmi_ddv_remove_battery;
 
-	sysfs_attr_init(&data->temp_attr.attr);
-	data->temp_attr.attr.name = "temp";
-	data->temp_attr.attr.mode = 0444;
-	data->temp_attr.show = temp_show;
-
 	sysfs_attr_init(&data->eppid_attr.attr);
 	data->eppid_attr.attr.name = "eppid";
 	data->eppid_attr.attr.mode = 0444;