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
161static 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(dev: &auxdev->dev), '.');
166 int match_size;
167
168 if (!p)
169 continue;
170 match_size = p - dev_name(dev: &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(dev: &auxdev->dev), id->name, match_size))
175 return id;
176 }
177 return NULL;
178}
179
180static 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(id: auxdrv->id_table, auxdev);
186}
187
188static 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, format: "MODALIAS=%s%.*s", AUXILIARY_MODULE_PREFIX,
196 (int)(p - name), name);
197}
198
199static 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
204static int auxiliary_bus_probe(struct device *dev)
205{
206 struct auxiliary_driver *auxdrv = to_auxiliary_drv(drv: dev->driver);
207 struct auxiliary_device *auxdev = to_auxiliary_dev(dev);
208 int ret;
209
210 ret = dev_pm_domain_attach(dev, power_on: 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(id: auxdrv->id_table, auxdev));
217 if (ret)
218 dev_pm_domain_detach(dev, power_off: true);
219
220 return ret;
221}
222
223static void auxiliary_bus_remove(struct device *dev)
224{
225 struct auxiliary_driver *auxdrv = to_auxiliary_drv(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, power_off: true);
231}
232
233static 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(drv: dev->driver);
240 auxdev = to_auxiliary_dev(dev);
241 }
242
243 if (auxdrv && auxdrv->shutdown)
244 auxdrv->shutdown(auxdev);
245}
246
247static 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 */
274int 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(dev: &auxdev->dev);
290 return 0;
291}
292EXPORT_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 */
313int __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, name: "%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}
335EXPORT_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 */
352struct 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(bus: &auxiliary_bus_type, start, data, match);
359 if (!dev)
360 return NULL;
361
362 return to_auxiliary_dev(dev);
363}
364EXPORT_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 */
377int __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, fmt: "%s.%s", modname,
387 auxdrv->name);
388 else
389 auxdrv->driver.name = kasprintf(GFP_KERNEL, fmt: "%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(drv: &auxdrv->driver);
398 if (ret)
399 kfree(objp: auxdrv->driver.name);
400
401 return ret;
402}
403EXPORT_SYMBOL_GPL(__auxiliary_driver_register);
404
405/**
406 * auxiliary_driver_unregister - unregister a driver
407 * @auxdrv: auxiliary_driver structure
408 */
409void auxiliary_driver_unregister(struct auxiliary_driver *auxdrv)
410{
411 driver_unregister(drv: &auxdrv->driver);
412 kfree(objp: auxdrv->driver.name);
413}
414EXPORT_SYMBOL_GPL(auxiliary_driver_unregister);
415
416void __init auxiliary_bus_init(void)
417{
418 WARN_ON(bus_register(&auxiliary_bus_type));
419}
420

source code of linux/drivers/base/auxiliary.c