Merge tag 'driver-core-6.14-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core

Pull driver core api addition from Greg KH:
 "Here is a driver core new api for 6.14-rc3 that is being added to
  allow platform devices from stop being abused.

  It adds a new 'faux_device' structure and bus and api to allow almost
  a straight or simpler conversion from platform devices that were not
  really a platform device. It also comes with a binding for rust, with
  an example driver in rust showing how it's used.

  I'm adding this now so that the patches that convert the different
  drivers and subsystems can all start flowing into linux-next now
  through their different development trees, in time for 6.15-rc1.

  We have a number that are already reviewed and tested, but adding
  those conversions now doesn't seem right. For now, no one is using
  this, and it passes all build tests from 0-day and linux-next, so all
  should be good"

* tag 'driver-core-6.14-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core:
  rust/kernel: Add faux device bindings
  driver core: add a faux bus for use when a simple device/bus is needed

Author: torvalds

Documentation/driver-api/infrastructure.rst

@@ -41,6 +41,12 @@ Device Drivers Base
 .. kernel-doc:: drivers/base/class.c
    :export:
 
+.. kernel-doc:: include/linux/device/faux.h
+   :internal:
+
+.. kernel-doc:: drivers/base/faux.c
+   :export:
+
 .. kernel-doc:: drivers/base/node.c
    :internal:
 

MAINTAINERS

@@ -7108,8 +7108,10 @@ F:	rust/kernel/device.rs
 F:	rust/kernel/device_id.rs
 F:	rust/kernel/devres.rs
 F:	rust/kernel/driver.rs
+F:	rust/kernel/faux.rs
 F:	rust/kernel/platform.rs
 F:	samples/rust/rust_driver_platform.rs
+F:	samples/rust/rust_driver_faux.rs
 
 DRIVERS FOR OMAP ADAPTIVE VOLTAGE SCALING (AVS)
 M:	Nishanth Menon <[email protected]>

drivers/base/Makefile

@@ -6,7 +6,7 @@ obj-y			:= component.o core.o bus.o dd.o syscore.o \
 			   cpu.o firmware.o init.o map.o devres.o \
 			   attribute_container.o transport_class.o \
 			   topology.o container.o property.o cacheinfo.o \
-			   swnode.o
+			   swnode.o faux.o
 obj-$(CONFIG_AUXILIARY_BUS) += auxiliary.o
 obj-$(CONFIG_DEVTMPFS)	+= devtmpfs.o
 obj-y			+= power/

drivers/base/base.h

@@ -137,6 +137,7 @@ int hypervisor_init(void);
 static inline int hypervisor_init(void) { return 0; }
 #endif
 int platform_bus_init(void);
+int faux_bus_init(void);
 void cpu_dev_init(void);
 void container_dev_init(void);
 #ifdef CONFIG_AUXILIARY_BUS

drivers/base/faux.c

@@ -0,0 +1,232 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2025 Greg Kroah-Hartman <[email protected]>
+ * Copyright (c) 2025 The Linux Foundation
+ *
+ * A "simple" faux bus that allows devices to be created and added
+ * automatically to it.  This is to be used whenever you need to create a
+ * device that is not associated with any "real" system resources, and do
+ * not want to have to deal with a bus/driver binding logic.  It is
+ * intended to be very simple, with only a create and a destroy function
+ * available.
+ */
+#include <linux/err.h>
+#include <linux/init.h>
+#include <linux/slab.h>
+#include <linux/string.h>
+#include <linux/container_of.h>
+#include <linux/device/faux.h>
+#include "base.h"
+
+/*
+ * Internal wrapper structure so we can hold a pointer to the
+ * faux_device_ops for this device.
+ */
+struct faux_object {
+	struct faux_device faux_dev;
+	const struct faux_device_ops *faux_ops;
+};
+#define to_faux_object(dev) container_of_const(dev, struct faux_object, faux_dev.dev)
+
+static struct device faux_bus_root = {
+	.init_name	= "faux",
+};
+
+static int faux_match(struct device *dev, const struct device_driver *drv)
+{
+	/* Match always succeeds, we only have one driver */
+	return 1;
+}
+
+static int faux_probe(struct device *dev)
+{
+	struct faux_object *faux_obj = to_faux_object(dev);
+	struct faux_device *faux_dev = &faux_obj->faux_dev;
+	const struct faux_device_ops *faux_ops = faux_obj->faux_ops;
+	int ret = 0;
+
+	if (faux_ops && faux_ops->probe)
+		ret = faux_ops->probe(faux_dev);
+
+	return ret;
+}
+
+static void faux_remove(struct device *dev)
+{
+	struct faux_object *faux_obj = to_faux_object(dev);
+	struct faux_device *faux_dev = &faux_obj->faux_dev;
+	const struct faux_device_ops *faux_ops = faux_obj->faux_ops;
+
+	if (faux_ops && faux_ops->remove)
+		faux_ops->remove(faux_dev);
+}
+
+static const struct bus_type faux_bus_type = {
+	.name		= "faux",
+	.match		= faux_match,
+	.probe		= faux_probe,
+	.remove		= faux_remove,
+};
+
+static struct device_driver faux_driver = {
+	.name		= "faux_driver",
+	.bus		= &faux_bus_type,
+	.probe_type	= PROBE_FORCE_SYNCHRONOUS,
+};
+
+static void faux_device_release(struct device *dev)
+{
+	struct faux_object *faux_obj = to_faux_object(dev);
+
+	kfree(faux_obj);
+}
+
+/**
+ * faux_device_create_with_groups - Create and register with the driver
+ *		core a faux device and populate the device with an initial
+ *		set of sysfs attributes.
+ * @name:	The name of the device we are adding, must be unique for
+ *		all faux devices.
+ * @parent:	Pointer to a potential parent struct device.  If set to
+ *		NULL, the device will be created in the "root" of the faux
+ *		device tree in sysfs.
+ * @faux_ops:	struct faux_device_ops that the new device will call back
+ *		into, can be NULL.
+ * @groups:	The set of sysfs attributes that will be created for this
+ *		device when it is registered with the driver core.
+ *
+ * Create a new faux device and register it in the driver core properly.
+ * If present, callbacks in @faux_ops will be called with the device that
+ * for the caller to do something with at the proper time given the
+ * device's lifecycle.
+ *
+ * Note, when this function is called, the functions specified in struct
+ * faux_ops can be called before the function returns, so be prepared for
+ * everything to be properly initialized before that point in time.
+ *
+ * Return:
+ * * NULL if an error happened with creating the device
+ * * pointer to a valid struct faux_device that is registered with sysfs
+ */
+struct faux_device *faux_device_create_with_groups(const char *name,
+						   struct device *parent,
+						   const struct faux_device_ops *faux_ops,
+						   const struct attribute_group **groups)
+{
+	struct faux_object *faux_obj;
+	struct faux_device *faux_dev;
+	struct device *dev;
+	int ret;
+
+	faux_obj = kzalloc(sizeof(*faux_obj), GFP_KERNEL);
+	if (!faux_obj)
+		return NULL;
+
+	/* Save off the callbacks so we can use them in the future */
+	faux_obj->faux_ops = faux_ops;
+
+	/* Initialize the device portion and register it with the driver core */
+	faux_dev = &faux_obj->faux_dev;
+	dev = &faux_dev->dev;
+
+	device_initialize(dev);
+	dev->release = faux_device_release;
+	if (parent)
+		dev->parent = parent;
+	else
+		dev->parent = &faux_bus_root;
+	dev->bus = &faux_bus_type;
+	dev->groups = groups;
+	dev_set_name(dev, "%s", name);
+
+	ret = device_add(dev);
+	if (ret) {
+		pr_err("%s: device_add for faux device '%s' failed with %d\n",
+		       __func__, name, ret);
+		put_device(dev);
+		return NULL;
+	}
+
+	return faux_dev;
+}
+EXPORT_SYMBOL_GPL(faux_device_create_with_groups);
+
+/**
+ * faux_device_create - create and register with the driver core a faux device
+ * @name:	The name of the device we are adding, must be unique for all
+ *		faux devices.
+ * @parent:	Pointer to a potential parent struct device.  If set to
+ *		NULL, the device will be created in the "root" of the faux
+ *		device tree in sysfs.
+ * @faux_ops:	struct faux_device_ops that the new device will call back
+ *		into, can be NULL.
+ *
+ * Create a new faux device and register it in the driver core properly.
+ * If present, callbacks in @faux_ops will be called with the device that
+ * for the caller to do something with at the proper time given the
+ * device's lifecycle.
+ *
+ * Note, when this function is called, the functions specified in struct
+ * faux_ops can be called before the function returns, so be prepared for
+ * everything to be properly initialized before that point in time.
+ *
+ * Return:
+ * * NULL if an error happened with creating the device
+ * * pointer to a valid struct faux_device that is registered with sysfs
+ */
+struct faux_device *faux_device_create(const char *name,
+				       struct device *parent,
+				       const struct faux_device_ops *faux_ops)
+{
+	return faux_device_create_with_groups(name, parent, faux_ops, NULL);
+}
+EXPORT_SYMBOL_GPL(faux_device_create);
+
+/**
+ * faux_device_destroy - destroy a faux device
+ * @faux_dev:	faux device to destroy
+ *
+ * Unregisters and cleans up a device that was created with a call to
+ * faux_device_create()
+ */
+void faux_device_destroy(struct faux_device *faux_dev)
+{
+	struct device *dev = &faux_dev->dev;
+
+	if (!faux_dev)
+		return;
+
+	device_del(dev);
+
+	/* The final put_device() will clean up the memory we allocated for this device. */
+	put_device(dev);
+}
+EXPORT_SYMBOL_GPL(faux_device_destroy);
+
+int __init faux_bus_init(void)
+{
+	int ret;
+
+	ret = device_register(&faux_bus_root);
+	if (ret) {
+		put_device(&faux_bus_root);
+		return ret;
+	}
+
+	ret = bus_register(&faux_bus_type);
+	if (ret)
+		goto error_bus;
+
+	ret = driver_register(&faux_driver);
+	if (ret)
+		goto error_driver;
+
+	return ret;
+
+error_driver:
+	bus_unregister(&faux_bus_type);
+
+error_bus:
+	device_unregister(&faux_bus_root);
+	return ret;
+}

drivers/base/init.c

@@ -32,6 +32,7 @@ void __init driver_init(void)
 	/* These are also core pieces, but must come after the
 	 * core core pieces.
 	 */
+	faux_bus_init();
 	of_core_init();
 	platform_bus_init();
 	auxiliary_bus_init();

include/linux/device/faux.h

@@ -0,0 +1,69 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (c) 2025 Greg Kroah-Hartman <[email protected]>
+ * Copyright (c) 2025 The Linux Foundation
+ *
+ * A "simple" faux bus that allows devices to be created and added
+ * automatically to it.  This is to be used whenever you need to create a
+ * device that is not associated with any "real" system resources, and do
+ * not want to have to deal with a bus/driver binding logic.  It is
+ * intended to be very simple, with only a create and a destroy function
+ * available.
+ */
+#ifndef _FAUX_DEVICE_H_
+#define _FAUX_DEVICE_H_
+
+#include <linux/container_of.h>
+#include <linux/device.h>
+
+/**
+ * struct faux_device - a "faux" device
+ * @dev:	internal struct device of the object
+ *
+ * A simple faux device that can be created/destroyed.  To be used when a
+ * driver only needs to have a device to "hang" something off.  This can be
+ * used for downloading firmware or other basic tasks.  Use this instead of
+ * a struct platform_device if the device has no resources assigned to
+ * it at all.
+ */
+struct faux_device {
+	struct device dev;
+};
+#define to_faux_device(x) container_of_const((x), struct faux_device, dev)
+
+/**
+ * struct faux_device_ops - a set of callbacks for a struct faux_device
+ * @probe:	called when a faux device is probed by the driver core
+ *		before the device is fully bound to the internal faux bus
+ *		code.  If probe succeeds, return 0, otherwise return a
+ *		negative error number to stop the probe sequence from
+ *		succeeding.
+ * @remove:	called when a faux device is removed from the system
+ *
+ * Both @probe and @remove are optional, if not needed, set to NULL.
+ */
+struct faux_device_ops {
+	int (*probe)(struct faux_device *faux_dev);
+	void (*remove)(struct faux_device *faux_dev);
+};
+
+struct faux_device *faux_device_create(const char *name,
+				       struct device *parent,
+				       const struct faux_device_ops *faux_ops);
+struct faux_device *faux_device_create_with_groups(const char *name,
+						   struct device *parent,
+						   const struct faux_device_ops *faux_ops,
+						   const struct attribute_group **groups);
+void faux_device_destroy(struct faux_device *faux_dev);
+
+static inline void *faux_device_get_drvdata(const struct faux_device *faux_dev)
+{
+	return dev_get_drvdata(&faux_dev->dev);
+}
+
+static inline void faux_device_set_drvdata(struct faux_device *faux_dev, void *data)
+{
+	dev_set_drvdata(&faux_dev->dev, data);
+}
+
+#endif /* _FAUX_DEVICE_H_ */

rust/bindings/bindings_helper.h

@@ -11,6 +11,7 @@
 #include <linux/blk_types.h>
 #include <linux/blkdev.h>
 #include <linux/cred.h>
+#include <linux/device/faux.h>
 #include <linux/errname.h>
 #include <linux/ethtool.h>
 #include <linux/file.h>