1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * Copyright (c) 2019-2020 Intel Corporation
4  *
5  * Please see Documentation/driver-api/auxiliary_bus.rst for more information.
6  */
7 
8 #define pr_fmt(fmt) "%s:%s: " fmt, KBUILD_MODNAME, __func__
9 
10 #include <linux/device.h>
11 #include <linux/init.h>
12 #include <linux/slab.h>
13 #include <linux/module.h>
14 #include <linux/pm_domain.h>
15 #include <linux/pm_runtime.h>
16 #include <linux/string.h>
17 #include <linux/auxiliary_bus.h>
18 #include "base.h"
19 
20 /**
21  * DOC: PURPOSE
22  *
23  * In some subsystems, the functionality of the core device (PCI/ACPI/other) is
24  * too complex for a single device to be managed by a monolithic driver (e.g.
25  * Sound Open Firmware), multiple devices might implement a common intersection
26  * of functionality (e.g. NICs + RDMA), or a driver may want to export an
27  * interface for another subsystem to drive (e.g. SIOV Physical Function export
28  * Virtual Function management).  A split of the functionality into child-
29  * devices representing sub-domains of functionality makes it possible to
30  * compartmentalize, layer, and distribute domain-specific concerns via a Linux
31  * device-driver model.
32  *
33  * An example for this kind of requirement is the audio subsystem where a
34  * single IP is handling multiple entities such as HDMI, Soundwire, local
35  * devices such as mics/speakers etc. The split for the core's functionality
36  * can be arbitrary or be defined by the DSP firmware topology and include
37  * hooks for test/debug. This allows for the audio core device to be minimal
38  * and focused on hardware-specific control and communication.
39  *
40  * Each auxiliary_device represents a part of its parent functionality. The
41  * generic behavior can be extended and specialized as needed by encapsulating
42  * an auxiliary_device within other domain-specific structures and the use of
43  * .ops callbacks. Devices on the auxiliary bus do not share any structures and
44  * the use of a communication channel with the parent is domain-specific.
45  *
46  * Note that ops are intended as a way to augment instance behavior within a
47  * class of auxiliary devices, it is not the mechanism for exporting common
48  * infrastructure from the parent. Consider EXPORT_SYMBOL_NS() to convey
49  * infrastructure from the parent module to the auxiliary module(s).
50  */
51 
52 /**
53  * DOC: USAGE
54  *
55  * The auxiliary bus is to be used when a driver and one or more kernel
56  * modules, who share a common header file with the driver, need a mechanism to
57  * connect and provide access to a shared object allocated by the
58  * auxiliary_device's registering driver.  The registering driver for the
59  * auxiliary_device(s) and the kernel module(s) registering auxiliary_drivers
60  * can be from the same subsystem, or from multiple subsystems.
61  *
62  * The emphasis here is on a common generic interface that keeps subsystem
63  * customization out of the bus infrastructure.
64  *
65  * One example is a PCI network device that is RDMA-capable and exports a child
66  * device to be driven by an auxiliary_driver in the RDMA subsystem.  The PCI
67  * driver allocates and registers an auxiliary_device for each physical
68  * function on the NIC.  The RDMA driver registers an auxiliary_driver that
69  * claims each of these auxiliary_devices.  This conveys data/ops published by
70  * the parent PCI device/driver to the RDMA auxiliary_driver.
71  *
72  * Another use case is for the PCI device to be split out into multiple sub
73  * functions.  For each sub function an auxiliary_device is created.  A PCI sub
74  * function driver binds to such devices that creates its own one or more class
75  * devices.  A PCI sub function auxiliary device is likely to be contained in a
76  * struct with additional attributes such as user defined sub function number
77  * and optional attributes such as resources and a link to the parent device.
78  * These attributes could be used by systemd/udev; and hence should be
79  * initialized before a driver binds to an auxiliary_device.
80  *
81  * A key requirement for utilizing the auxiliary bus is that there is no
82  * dependency on a physical bus, device, register accesses or regmap support.
83  * These individual devices split from the core cannot live on the platform bus
84  * as they are not physical devices that are controlled by DT/ACPI.  The same
85  * argument applies for not using MFD in this scenario as MFD relies on
86  * individual function devices being physical devices.
87  */
88 
89 /**
90  * DOC: EXAMPLE
91  *
92  * Auxiliary devices are created and registered by a subsystem-level core
93  * device that needs to break up its functionality into smaller fragments. One
94  * way to extend the scope of an auxiliary_device is to encapsulate it within a
95  * domain- pecific structure defined by the parent device. This structure
96  * contains the auxiliary_device and any associated shared data/callbacks
97  * needed to establish the connection with the parent.
98  *
99  * An example is:
100  *
101  * .. code-block:: c
102  *
103  *         struct foo {
104  *		struct auxiliary_device auxdev;
105  *		void (*connect)(struct auxiliary_device *auxdev);
106  *		void (*disconnect)(struct auxiliary_device *auxdev);
107  *		void *data;
108  *        };
109  *
110  * The parent device then registers the auxiliary_device by calling
111  * auxiliary_device_init(), and then auxiliary_device_add(), with the pointer
112  * to the auxdev member of the above structure. The parent provides a name for
113  * the auxiliary_device that, combined with the parent's KBUILD_MODNAME,
114  * creates a match_name that is be used for matching and binding with a driver.
115  *
116  * Whenever an auxiliary_driver is registered, based on the match_name, the
117  * auxiliary_driver's probe() is invoked for the matching devices.  The
118  * auxiliary_driver can also be encapsulated inside custom drivers that make
119  * the core device's functionality extensible by adding additional
120  * domain-specific ops as follows:
121  *
122  * .. code-block:: c
123  *
124  *	struct my_ops {
125  *		void (*send)(struct auxiliary_device *auxdev);
126  *		void (*receive)(struct auxiliary_device *auxdev);
127  *	};
128  *
129  *
130  *	struct my_driver {
131  *		struct auxiliary_driver auxiliary_drv;
132  *		const struct my_ops ops;
133  *	};
134  *
135  * An example of this type of usage is:
136  *
137  * .. code-block:: c
138  *
139  *	const struct auxiliary_device_id my_auxiliary_id_table[] = {
140  *		{ .name = "foo_mod.foo_dev" },
141  *		{ },
142  *	};
143  *
144  *	const struct my_ops my_custom_ops = {
145  *		.send = my_tx,
146  *		.receive = my_rx,
147  *	};
148  *
149  *	const struct my_driver my_drv = {
150  *		.auxiliary_drv = {
151  *			.name = "myauxiliarydrv",
152  *			.id_table = my_auxiliary_id_table,
153  *			.probe = my_probe,
154  *			.remove = my_remove,
155  *			.shutdown = my_shutdown,
156  *		},
157  *		.ops = my_custom_ops,
158  *	};
159  */
160 
auxiliary_match_id(const struct auxiliary_device_id * id,const struct auxiliary_device * auxdev)161 static const struct auxiliary_device_id *auxiliary_match_id(const struct auxiliary_device_id *id,
162 							    const struct auxiliary_device *auxdev)
163 {
164 	for (; id->name[0]; id++) {
165 		const char *p = strrchr(dev_name(&auxdev->dev), '.');
166 		int match_size;
167 
168 		if (!p)
169 			continue;
170 		match_size = p - dev_name(&auxdev->dev);
171 
172 		/* use dev_name(&auxdev->dev) prefix before last '.' char to match to */
173 		if (strlen(id->name) == match_size &&
174 		    !strncmp(dev_name(&auxdev->dev), id->name, match_size))
175 			return id;
176 	}
177 	return NULL;
178 }
179 
auxiliary_match(struct device * dev,struct device_driver * drv)180 static int auxiliary_match(struct device *dev, struct device_driver *drv)
181 {
182 	struct auxiliary_device *auxdev = to_auxiliary_dev(dev);
183 	struct auxiliary_driver *auxdrv = to_auxiliary_drv(drv);
184 
185 	return !!auxiliary_match_id(auxdrv->id_table, auxdev);
186 }
187 
auxiliary_uevent(const struct device * dev,struct kobj_uevent_env * env)188 static int auxiliary_uevent(const struct device *dev, struct kobj_uevent_env *env)
189 {
190 	const char *name, *p;
191 
192 	name = dev_name(dev);
193 	p = strrchr(name, '.');
194 
195 	return add_uevent_var(env, "MODALIAS=%s%.*s", AUXILIARY_MODULE_PREFIX,
196 			      (int)(p - name), name);
197 }
198 
199 static const struct dev_pm_ops auxiliary_dev_pm_ops = {
200 	SET_RUNTIME_PM_OPS(pm_generic_runtime_suspend, pm_generic_runtime_resume, NULL)
201 	SET_SYSTEM_SLEEP_PM_OPS(pm_generic_suspend, pm_generic_resume)
202 };
203 
auxiliary_bus_probe(struct device * dev)204 static int auxiliary_bus_probe(struct device *dev)
205 {
206 	struct auxiliary_driver *auxdrv = to_auxiliary_drv(dev->driver);
207 	struct auxiliary_device *auxdev = to_auxiliary_dev(dev);
208 	int ret;
209 
210 	ret = dev_pm_domain_attach(dev, true);
211 	if (ret) {
212 		dev_warn(dev, "Failed to attach to PM Domain : %d\n", ret);
213 		return ret;
214 	}
215 
216 	ret = auxdrv->probe(auxdev, auxiliary_match_id(auxdrv->id_table, auxdev));
217 	if (ret)
218 		dev_pm_domain_detach(dev, true);
219 
220 	return ret;
221 }
222 
auxiliary_bus_remove(struct device * dev)223 static void auxiliary_bus_remove(struct device *dev)
224 {
225 	struct auxiliary_driver *auxdrv = to_auxiliary_drv(dev->driver);
226 	struct auxiliary_device *auxdev = to_auxiliary_dev(dev);
227 
228 	if (auxdrv->remove)
229 		auxdrv->remove(auxdev);
230 	dev_pm_domain_detach(dev, true);
231 }
232 
auxiliary_bus_shutdown(struct device * dev)233 static void auxiliary_bus_shutdown(struct device *dev)
234 {
235 	struct auxiliary_driver *auxdrv = NULL;
236 	struct auxiliary_device *auxdev;
237 
238 	if (dev->driver) {
239 		auxdrv = to_auxiliary_drv(dev->driver);
240 		auxdev = to_auxiliary_dev(dev);
241 	}
242 
243 	if (auxdrv && auxdrv->shutdown)
244 		auxdrv->shutdown(auxdev);
245 }
246 
247 static struct bus_type auxiliary_bus_type = {
248 	.name = "auxiliary",
249 	.probe = auxiliary_bus_probe,
250 	.remove = auxiliary_bus_remove,
251 	.shutdown = auxiliary_bus_shutdown,
252 	.match = auxiliary_match,
253 	.uevent = auxiliary_uevent,
254 	.pm = &auxiliary_dev_pm_ops,
255 };
256 
257 /**
258  * auxiliary_device_init - check auxiliary_device and initialize
259  * @auxdev: auxiliary device struct
260  *
261  * This is the second step in the three-step process to register an
262  * auxiliary_device.
263  *
264  * When this function returns an error code, then the device_initialize will
265  * *not* have been performed, and the caller will be responsible to free any
266  * memory allocated for the auxiliary_device in the error path directly.
267  *
268  * It returns 0 on success.  On success, the device_initialize has been
269  * performed.  After this point any error unwinding will need to include a call
270  * to auxiliary_device_uninit().  In this post-initialize error scenario, a call
271  * to the device's .release callback will be triggered, and all memory clean-up
272  * is expected to be handled there.
273  */
auxiliary_device_init(struct auxiliary_device * auxdev)274 int auxiliary_device_init(struct auxiliary_device *auxdev)
275 {
276 	struct device *dev = &auxdev->dev;
277 
278 	if (!dev->parent) {
279 		pr_err("auxiliary_device has a NULL dev->parent\n");
280 		return -EINVAL;
281 	}
282 
283 	if (!auxdev->name) {
284 		pr_err("auxiliary_device has a NULL name\n");
285 		return -EINVAL;
286 	}
287 
288 	dev->bus = &auxiliary_bus_type;
289 	device_initialize(&auxdev->dev);
290 	return 0;
291 }
292 EXPORT_SYMBOL_GPL(auxiliary_device_init);
293 
294 /**
295  * __auxiliary_device_add - add an auxiliary bus device
296  * @auxdev: auxiliary bus device to add to the bus
297  * @modname: name of the parent device's driver module
298  *
299  * This is the third step in the three-step process to register an
300  * auxiliary_device.
301  *
302  * This function must be called after a successful call to
303  * auxiliary_device_init(), which will perform the device_initialize.  This
304  * means that if this returns an error code, then a call to
305  * auxiliary_device_uninit() must be performed so that the .release callback
306  * will be triggered to free the memory associated with the auxiliary_device.
307  *
308  * The expectation is that users will call the "auxiliary_device_add" macro so
309  * that the caller's KBUILD_MODNAME is automatically inserted for the modname
310  * parameter.  Only if a user requires a custom name would this version be
311  * called directly.
312  */
__auxiliary_device_add(struct auxiliary_device * auxdev,const char * modname)313 int __auxiliary_device_add(struct auxiliary_device *auxdev, const char *modname)
314 {
315 	struct device *dev = &auxdev->dev;
316 	int ret;
317 
318 	if (!modname) {
319 		dev_err(dev, "auxiliary device modname is NULL\n");
320 		return -EINVAL;
321 	}
322 
323 	ret = dev_set_name(dev, "%s.%s.%d", modname, auxdev->name, auxdev->id);
324 	if (ret) {
325 		dev_err(dev, "auxiliary device dev_set_name failed: %d\n", ret);
326 		return ret;
327 	}
328 
329 	ret = device_add(dev);
330 	if (ret)
331 		dev_err(dev, "adding auxiliary device failed!: %d\n", ret);
332 
333 	return ret;
334 }
335 EXPORT_SYMBOL_GPL(__auxiliary_device_add);
336 
337 /**
338  * auxiliary_find_device - auxiliary device iterator for locating a particular device.
339  * @start: Device to begin with
340  * @data: Data to pass to match function
341  * @match: Callback function to check device
342  *
343  * This function returns a reference to a device that is 'found'
344  * for later use, as determined by the @match callback.
345  *
346  * The reference returned should be released with put_device().
347  *
348  * The callback should return 0 if the device doesn't match and non-zero
349  * if it does.  If the callback returns non-zero, this function will
350  * return to the caller and not iterate over any more devices.
351  */
auxiliary_find_device(struct device * start,const void * data,int (* match)(struct device * dev,const void * data))352 struct auxiliary_device *auxiliary_find_device(struct device *start,
353 					       const void *data,
354 					       int (*match)(struct device *dev, const void *data))
355 {
356 	struct device *dev;
357 
358 	dev = bus_find_device(&auxiliary_bus_type, start, data, match);
359 	if (!dev)
360 		return NULL;
361 
362 	return to_auxiliary_dev(dev);
363 }
364 EXPORT_SYMBOL_GPL(auxiliary_find_device);
365 
366 /**
367  * __auxiliary_driver_register - register a driver for auxiliary bus devices
368  * @auxdrv: auxiliary_driver structure
369  * @owner: owning module/driver
370  * @modname: KBUILD_MODNAME for parent driver
371  *
372  * The expectation is that users will call the "auxiliary_driver_register"
373  * macro so that the caller's KBUILD_MODNAME is automatically inserted for the
374  * modname parameter.  Only if a user requires a custom name would this version
375  * be called directly.
376  */
__auxiliary_driver_register(struct auxiliary_driver * auxdrv,struct module * owner,const char * modname)377 int __auxiliary_driver_register(struct auxiliary_driver *auxdrv,
378 				struct module *owner, const char *modname)
379 {
380 	int ret;
381 
382 	if (WARN_ON(!auxdrv->probe) || WARN_ON(!auxdrv->id_table))
383 		return -EINVAL;
384 
385 	if (auxdrv->name)
386 		auxdrv->driver.name = kasprintf(GFP_KERNEL, "%s.%s", modname,
387 						auxdrv->name);
388 	else
389 		auxdrv->driver.name = kasprintf(GFP_KERNEL, "%s", modname);
390 	if (!auxdrv->driver.name)
391 		return -ENOMEM;
392 
393 	auxdrv->driver.owner = owner;
394 	auxdrv->driver.bus = &auxiliary_bus_type;
395 	auxdrv->driver.mod_name = modname;
396 
397 	ret = driver_register(&auxdrv->driver);
398 	if (ret)
399 		kfree(auxdrv->driver.name);
400 
401 	return ret;
402 }
403 EXPORT_SYMBOL_GPL(__auxiliary_driver_register);
404 
405 /**
406  * auxiliary_driver_unregister - unregister a driver
407  * @auxdrv: auxiliary_driver structure
408  */
auxiliary_driver_unregister(struct auxiliary_driver * auxdrv)409 void auxiliary_driver_unregister(struct auxiliary_driver *auxdrv)
410 {
411 	driver_unregister(&auxdrv->driver);
412 	kfree(auxdrv->driver.name);
413 }
414 EXPORT_SYMBOL_GPL(auxiliary_driver_unregister);
415 
auxiliary_bus_init(void)416 void __init auxiliary_bus_init(void)
417 {
418 	WARN_ON(bus_register(&auxiliary_bus_type));
419 }
420