ACPICA: Introduce acpi_get_data_full() and rework acpi_get_data()

Introduce a new function, acpi_get_data_full(), working in analogy
with acpi_get_data() except that it can execute a callback provided
as its 4th argument right after acpi_ns_get_attached_data() has
returned a success.

That will allow Linux to reference count the object pointed to by
*data before the namespace mutex is released so as to ensure that it
will not be freed going forward until the reference to it acquired
by acpi_get_data_full() is dropped.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: Mika Westerberg <mika.westerberg@linux.intel.com>

drivers/acpi/acpica/nsxfeval.c

@@ -923,19 +923,22 @@ ACPI_EXPORT_SYMBOL(acpi_detach_data)
 
 /*******************************************************************************
  *
- * FUNCTION:    acpi_get_data
+ * FUNCTION:    acpi_get_data_full
  *
  * PARAMETERS:  obj_handle          - Namespace node
  *              handler             - Handler used in call to attach_data
  *              data                - Where the data is returned
+ *              callback            - function to execute before returning
  *
  * RETURN:      Status
  *
- * DESCRIPTION: Retrieve data that was previously attached to a namespace node.
+ * DESCRIPTION: Retrieve data that was previously attached to a namespace node
+ *              and execute a callback before returning.
  *
  ******************************************************************************/
 acpi_status
-acpi_get_data(acpi_handle obj_handle, acpi_object_handler handler, void **data)
+acpi_get_data_full(acpi_handle obj_handle, acpi_object_handler handler,
+		   void **data, void (*callback)(void *))
 {
 	struct acpi_namespace_node *node;
 	acpi_status status;
@@ -960,10 +963,34 @@ acpi_get_data(acpi_handle obj_handle, acpi_object_handler handler, void **data)
 	}
 
 	status = acpi_ns_get_attached_data(node, handler, data);
+	if (ACPI_SUCCESS(status) && callback) {
+		callback(*data);
+	}
 
 unlock_and_exit:
 	(void)acpi_ut_release_mutex(ACPI_MTX_NAMESPACE);
 	return (status);
 }
 
+ACPI_EXPORT_SYMBOL(acpi_get_data_full)
+
+/*******************************************************************************
+ *
+ * FUNCTION:    acpi_get_data
+ *
+ * PARAMETERS:  obj_handle          - Namespace node
+ *              handler             - Handler used in call to attach_data
+ *              data                - Where the data is returned
+ *
+ * RETURN:      Status
+ *
+ * DESCRIPTION: Retrieve data that was previously attached to a namespace node.
+ *
+ ******************************************************************************/
+acpi_status
+acpi_get_data(acpi_handle obj_handle, acpi_object_handler handler, void **data)
+{
+	return acpi_get_data_full(obj_handle, handler, data, NULL);
+}
+
 ACPI_EXPORT_SYMBOL(acpi_get_data)

include/acpi/acpixf.h

@@ -229,6 +229,10 @@ acpi_attach_data(acpi_handle object, acpi_object_handler handler, void *data);
 
 acpi_status acpi_detach_data(acpi_handle object, acpi_object_handler handler);
 
+acpi_status
+acpi_get_data_full(acpi_handle object, acpi_object_handler handler, void **data,
+		   void (*callback)(void *));
+
 acpi_status
 acpi_get_data(acpi_handle object, acpi_object_handler handler, void **data);