driver core: auxiliary bus: add device creation helpers

Add helper functions to create a device on the auxiliary bus.

This is meant for fairly simple usage of the auxiliary bus, to avoid having
the same code repeated in the different drivers.

Suggested-by: Stephen Boyd <sboyd@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Link: https://lore.kernel.org/r/20250218-aux-device-create-helper-v4-1-c3d7dfdea2e6@baylibre.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/base/auxiliary.c

@@ -385,6 +385,114 @@ 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 (IS_ERR(auxdev))
+		return auxdev;
+
+	ret = devm_add_action_or_reset(dev, auxiliary_device_destroy,
+				       auxdev);
+	if (ret)
+		return ERR_PTR(ret);
+
+	return auxdev;
+}
+EXPORT_SYMBOL_GPL(__devm_auxiliary_device_create);
+
 void __init auxiliary_bus_init(void)
 {
 	WARN_ON(bus_register(&auxiliary_bus_type));

include/linux/auxiliary_bus.h

@@ -254,6 +254,23 @@ int __auxiliary_driver_register(struct auxiliary_driver *auxdrv, struct module *
 
 void auxiliary_driver_unregister(struct auxiliary_driver *auxdrv);
 
+struct auxiliary_device *auxiliary_device_create(struct device *dev,
+						 const char *modname,
+						 const char *devname,
+						 void *platform_data,
+						 int id);
+void auxiliary_device_destroy(void *auxdev);
+
+struct auxiliary_device *__devm_auxiliary_device_create(struct device *dev,
+							const char *modname,
+							const char *devname,
+							void *platform_data,
+							int id);
+
+#define devm_auxiliary_device_create(dev, devname, platform_data)     \
+	__devm_auxiliary_device_create(dev, KBUILD_MODNAME, devname,  \
+				       platform_data, 0)
+
 /**
  * module_auxiliary_driver() - Helper macro for registering an auxiliary driver
  * @__auxiliary_driver: auxiliary driver struct