hwmon: (acpi_power_meter) Use acpi_bus_get_acpi_device()

In read_domain_devices(), acpi_bus_get_device() is called to obtain
the ACPI device object attached to the given ACPI handle and
subsequently that object is passed to get_device() for reference
counting, but there is a window between the acpi_bus_get_device()
and get_device() calls in which the ACPI device object in question
may go away.

To address this issue, make read_domain_devices() use
acpi_bus_get_acpi_device() to reference count and return the given
ACPI device object in one go and export that function to modules.

While at it, also make read_domain_devices() and
remove_domain_devices() use acpi_dev_put() instead of calling
put_device() directly on the ACPI device objects returned by
acpi_bus_get_acpi_device().

Signed-off-by: Rafael J. Wysocki <[e-mail]>
Reviewed-by: Andy Shevchenko <[e-mail]>
Link: https://lore.kernel.org/r/11871063.O9o76ZdvQC@kreacher
Signed-off-by: Guenter Roeck <[e-mail]>

drivers/acpi/scan.c

···
 {
 	return handle_to_device(handle, get_acpi_device);
 }
+EXPORT_SYMBOL_GPL(acpi_bus_get_acpi_device);
 
 static struct acpi_device_bus_id *acpi_device_bus_id_match(const char *dev_id)
 {

drivers/hwmon/acpi_power_meter.c

···
 
 		sysfs_remove_link(resource->holders_dir,
 				  kobject_name(&obj->dev.kobj));
-		put_device(&obj->dev);
+		acpi_dev_put(obj);
 	}
 
 	kfree(resource->domain_devices);
···
 			continue;
 
 		/* Create a symlink to domain objects */
-		resource->domain_devices[i] = NULL;
-		if (acpi_bus_get_device(element->reference.handle,
-					&resource->domain_devices[i]))
+		obj = acpi_bus_get_acpi_device(element->reference.handle);
+		resource->domain_devices[i] = obj;
+		if (!obj)
 			continue;
-
-		obj = resource->domain_devices[i];
-		get_device(&obj->dev);
 
 		res = sysfs_create_link(resource->holders_dir, &obj->dev.kobj,
 				      kobject_name(&obj->dev.kobj));
 		if (res) {
-			put_device(&obj->dev);
+			acpi_dev_put(obj);
 			resource->domain_devices[i] = NULL;
 		}
 	}