1 files changed, 118 insertions, 0 deletions
diff --git a/drivers/base/auxiliary.c b/drivers/base/auxiliary.c
index afa4df4c5a3f..dba7c8e13a53 100644
--- a/drivers/base/auxiliary.c
+++ b/drivers/base/auxiliary.c
@@ -156,6 +156,16 @@
  *		},
  *		.ops = my_custom_ops,
  *	};
+ *
+ * Please note that such custom ops approach is valid, but it is hard to implement
+ * it right without global locks per-device to protect from auxiliary_drv removal
+ * during call to that ops. In addition, this implementation lacks proper module
+ * dependency, which causes to load/unload races between auxiliary parent and devices
+ * modules.
+ *
+ * The most easiest way to provide these ops reliably without needing to
+ * have a lock is to EXPORT_SYMBOL*() them and rely on already existing
+ * modules infrastructure for validity and correct dependencies chains.
  */
 
 static const struct auxiliary_device_id *auxiliary_match_id(const struct auxiliary_device_id *id,
@@ -385,6 +395,114 @@ void auxiliary_driver_unregister(struct auxiliary_driver *auxdrv)
 }
 EXPORT_SYMBOL_GPL(auxiliary_driver_unregister);
 
+static void auxiliary_device_release(struct device *dev)
+{
+	struct auxiliary_device *auxdev = to_auxiliary_dev(dev);
+
+	kfree(auxdev);
+}
+
+/**
+ * auxiliary_device_create - create a device on the auxiliary bus
+ * @dev: parent device
+ * @modname: module name used to create the auxiliary driver name.
+ * @devname: auxiliary bus device name
+ * @platform_data: auxiliary bus device platform data
+ * @id: auxiliary bus device id
+ *
+ * Helper to create an auxiliary bus device.
+ * The device created matches driver 'modname.devname' on the auxiliary bus.
+ */
+struct auxiliary_device *auxiliary_device_create(struct device *dev,
+						 const char *modname,
+						 const char *devname,
+						 void *platform_data,
+						 int id)
+{
+	struct auxiliary_device *auxdev;
+	int ret;
+
+	auxdev = kzalloc(sizeof(*auxdev), GFP_KERNEL);
+	if (!auxdev)
+		return NULL;
+
+	auxdev->id = id;
+	auxdev->name = devname;
+	auxdev->dev.parent = dev;
+	auxdev->dev.platform_data = platform_data;
+	auxdev->dev.release = auxiliary_device_release;
+	device_set_of_node_from_dev(&auxdev->dev, dev);
+
+	ret = auxiliary_device_init(auxdev);
+	if (ret) {
+		kfree(auxdev);
+		return NULL;
+	}
+
+	ret = __auxiliary_device_add(auxdev, modname);
+	if (ret) {
+		/*
+		 * It may look odd but auxdev should not be freed here.
+		 * auxiliary_device_uninit() calls device_put() which call
+		 * the device release function, freeing auxdev.
+		 */
+		auxiliary_device_uninit(auxdev);
+		return NULL;
+	}
+
+	return auxdev;
+}
+EXPORT_SYMBOL_GPL(auxiliary_device_create);
+
+/**
+ * auxiliary_device_destroy - remove an auxiliary device
+ * @auxdev: pointer to the auxdev to be removed
+ *
+ * Helper to remove an auxiliary device created with
+ * auxiliary_device_create()
+ */
+void auxiliary_device_destroy(void *auxdev)
+{
+	struct auxiliary_device *_auxdev = auxdev;
+
+	auxiliary_device_delete(_auxdev);
+	auxiliary_device_uninit(_auxdev);
+}
+EXPORT_SYMBOL_GPL(auxiliary_device_destroy);
+
+/**
+ * __devm_auxiliary_device_create - create a managed device on the auxiliary bus
+ * @dev: parent device
+ * @modname: module name used to create the auxiliary driver name.
+ * @devname: auxiliary bus device name
+ * @platform_data: auxiliary bus device platform data
+ * @id: auxiliary bus device id
+ *
+ * Device managed helper to create an auxiliary bus device.
+ * The device created matches driver 'modname.devname' on the auxiliary bus.
+ */
+struct auxiliary_device *__devm_auxiliary_device_create(struct device *dev,
+							const char *modname,
+							const char *devname,
+							void *platform_data,
+							int id)
+{
+	struct auxiliary_device *auxdev;
+	int ret;
+
+	auxdev = auxiliary_device_create(dev, modname, devname, platform_data, id);
+	if (!auxdev)
+		return NULL;
+
+	ret = devm_add_action_or_reset(dev, auxiliary_device_destroy,
+				       auxdev);
+	if (ret)
+		return NULL;
+
+	return auxdev;
+}
+EXPORT_SYMBOL_GPL(__devm_auxiliary_device_create);
+
 void __init auxiliary_bus_init(void)
 {
 	WARN_ON(bus_register(&auxiliary_bus_type));