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_ */ | |