Many drivers abuse the platform driver/bus system as it provides a simple way to create and bind a device to a driver-specific set of probe/release functions. Instead of doing that, and wasting all of the memory associated with a platform device, here is a "faux" bus that can be used instead.
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| 1 | /* SPDX-License-Identifier: GPL-2.0-only */ | ||
| 2 | /* | ||
| 3 | * Copyright (c) 2025 Greg Kroah-Hartman <gregkh@linuxfoundation.org> | ||
| 4 | * Copyright (c) 2025 The Linux Foundation | ||
| 5 | * | ||
| 6 | * A "simple" faux bus that allows devices to be created and added | ||
| 7 | * automatically to it. This is to be used whenever you need to create a | ||
| 8 | * device that is not associated with any "real" system resources, and do | ||
| 9 | * not want to have to deal with a bus/driver binding logic. It is | ||
| 10 | * intended to be very simple, with only a create and a destroy function | ||
| 11 | * available. | ||
| 12 | */ | ||
| 13 | #ifndef _FAUX_DEVICE_H_ | ||
| 14 | #define _FAUX_DEVICE_H_ | ||
| 15 | |||
| 16 | #include <linux/container_of.h> | ||
| 17 | #include <linux/device.h> | ||
| 18 | |||
| 19 | /** | ||
| 20 | * struct faux_device - a "faux" device | ||
| 21 | * @dev: internal struct device of the object | ||
| 22 | * | ||
| 23 | * A simple faux device that can be created/destroyed. To be used when a | ||
| 24 | * driver only needs to have a device to "hang" something off. This can be | ||
| 25 | * used for downloading firmware or other basic tasks. Use this instead of | ||
| 26 | * a struct platform_device if the device has no resources assigned to | ||
| 27 | * it at all. | ||
| 28 | */ | ||
| 29 | struct faux_device { | ||
| 30 | struct device dev; | ||
| 31 | }; | ||
| 32 | #define to_faux_device(x) container_of_const((x), struct faux_device, dev) | ||
| 33 | |||
| 34 | /** | ||
| 35 | * struct faux_device_ops - a set of callbacks for a struct faux_device | ||
| 36 | * @probe: called when a faux device is probed by the driver core | ||
| 37 | * before the device is fully bound to the internal faux bus | ||
| 38 | * code. If probe succeeds, return 0, otherwise return a | ||
| 39 | * negative error number to stop the probe sequence from | ||
| 40 | * succeeding. | ||
| 41 | * @remove: called when a faux device is removed from the system | ||
| 42 | * | ||
| 43 | * Both @probe and @remove are optional, if not needed, set to NULL. | ||
| 44 | */ | ||
| 45 | struct faux_device_ops { | ||
| 46 | int (*probe)(struct faux_device *faux_dev); | ||
| 47 | void (*remove)(struct faux_device *faux_dev); | ||
| 48 | }; | ||
| 49 | |||
| 50 | struct faux_device *faux_device_create(const char *name, | ||
| 51 | struct device *parent, | ||
| 52 | const struct faux_device_ops *faux_ops); | ||
| 53 | struct faux_device *faux_device_create_with_groups(const char *name, | ||
| 54 | struct device *parent, | ||
| 55 | const struct faux_device_ops *faux_ops, | ||
| 56 | const struct attribute_group **groups); | ||
| 57 | void faux_device_destroy(struct faux_device *faux_dev); | ||
| 58 | |||
| 59 | static inline void *faux_device_get_drvdata(const struct faux_device *faux_dev) | ||
| 60 | { | ||
| 61 | return dev_get_drvdata(&faux_dev->dev); | ||
| 62 | } | ||
| 63 | |||
| 64 | static inline void faux_device_set_drvdata(struct faux_device *faux_dev, void *data) | ||
| 65 | { | ||
| 66 | dev_set_drvdata(&faux_dev->dev, data); | ||
| 67 | } | ||
| 68 | |||
| 69 | #endif /* _FAUX_DEVICE_H_ */ | ||