auxiliary.c

  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-specific 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 * Please note that such custom ops approach is valid, but it is hard to implement
161 * it right without global locks per-device to protect from auxiliary_drv removal
162 * during call to that ops. In addition, this implementation lacks proper module
163 * dependency, which causes to load/unload races between auxiliary parent and devices
164 * modules.
165 *
166 * The most easiest way to provide these ops reliably without needing to
167 * have a lock is to EXPORT_SYMBOL*() them and rely on already existing
168 * modules infrastructure for validity and correct dependencies chains.
169 */
170
171static const struct auxiliary_device_id *auxiliary_match_id(const struct auxiliary_device_id *id,
172							    const struct auxiliary_device *auxdev)
173{
174	const char *auxdev_name = dev_name(&auxdev->dev);
175	const char *p = strrchr(auxdev_name, '.');
176	int match_size;
177
178	if (!p)
179		return NULL;
180	match_size = p - auxdev_name;
181
182	for (; id->name[0]; id++) {
183		/* use dev_name(&auxdev->dev) prefix before last '.' char to match to */
184		if (strlen(id->name) == match_size &&
185		    !strncmp(auxdev_name, id->name, match_size))
186			return id;
187	}
188	return NULL;
189}
190
191static int auxiliary_match(struct device *dev, const struct device_driver *drv)
192{
193	struct auxiliary_device *auxdev = to_auxiliary_dev(dev);
194	const struct auxiliary_driver *auxdrv = to_auxiliary_drv(drv);
195
196	return !!auxiliary_match_id(auxdrv->id_table, auxdev);
197}
198
199static int auxiliary_uevent(const struct device *dev, struct kobj_uevent_env *env)
200{
201	const char *name, *p;
202
203	name = dev_name(dev);
204	p = strrchr(name, '.');
205
206	return add_uevent_var(env, "MODALIAS=%s%.*s", AUXILIARY_MODULE_PREFIX,
207			      (int)(p - name), name);
208}
209
210static const struct dev_pm_ops auxiliary_dev_pm_ops = {
211	SET_RUNTIME_PM_OPS(pm_generic_runtime_suspend, pm_generic_runtime_resume, NULL)
212	SET_SYSTEM_SLEEP_PM_OPS(pm_generic_suspend, pm_generic_resume)
213};
214
215static int auxiliary_bus_probe(struct device *dev)
216{
217	const struct auxiliary_driver *auxdrv = to_auxiliary_drv(dev->driver);
218	struct auxiliary_device *auxdev = to_auxiliary_dev(dev);
219	int ret;
220
221	ret = dev_pm_domain_attach(dev, PD_FLAG_ATTACH_POWER_ON |
222					PD_FLAG_DETACH_POWER_OFF);
223	if (ret) {
224		dev_warn(dev, "Failed to attach to PM Domain : %d\n", ret);
225		return ret;
226	}
227
228	return auxdrv->probe(auxdev, auxiliary_match_id(auxdrv->id_table, auxdev));
229}
230
231static void auxiliary_bus_remove(struct device *dev)
232{
233	const struct auxiliary_driver *auxdrv = to_auxiliary_drv(dev->driver);
234	struct auxiliary_device *auxdev = to_auxiliary_dev(dev);
235
236	if (auxdrv->remove)
237		auxdrv->remove(auxdev);
238}
239
240static void auxiliary_bus_shutdown(struct device *dev)
241{
242	const struct auxiliary_driver *auxdrv = NULL;
243	struct auxiliary_device *auxdev;
244
245	if (dev->driver) {
246		auxdrv = to_auxiliary_drv(dev->driver);
247		auxdev = to_auxiliary_dev(dev);
248	}
249
250	if (auxdrv && auxdrv->shutdown)
251		auxdrv->shutdown(auxdev);
252}
253
254static const struct bus_type auxiliary_bus_type = {
255	.name = "auxiliary",
256	.probe = auxiliary_bus_probe,
257	.remove = auxiliary_bus_remove,
258	.shutdown = auxiliary_bus_shutdown,
259	.match = auxiliary_match,
260	.uevent = auxiliary_uevent,
261	.pm = &auxiliary_dev_pm_ops,
262};
263
264/**
265 * auxiliary_device_init - check auxiliary_device and initialize
266 * @auxdev: auxiliary device struct
267 *
268 * This is the second step in the three-step process to register an
269 * auxiliary_device.
270 *
271 * When this function returns an error code, then the device_initialize will
272 * *not* have been performed, and the caller will be responsible to free any
273 * memory allocated for the auxiliary_device in the error path directly.
274 *
275 * It returns 0 on success.  On success, the device_initialize has been
276 * performed.  After this point any error unwinding will need to include a call
277 * to auxiliary_device_uninit().  In this post-initialize error scenario, a call
278 * to the device's .release callback will be triggered, and all memory clean-up
279 * is expected to be handled there.
280 */
281int auxiliary_device_init(struct auxiliary_device *auxdev)
282{
283	struct device *dev = &auxdev->dev;
284
285	if (!dev->parent) {
286		pr_err("auxiliary_device has a NULL dev->parent\n");
287		return -EINVAL;
288	}
289
290	if (!auxdev->name) {
291		pr_err("auxiliary_device has a NULL name\n");
292		return -EINVAL;
293	}
294
295	dev->bus = &auxiliary_bus_type;
296	device_initialize(&auxdev->dev);
297	mutex_init(&auxdev->sysfs.lock);
298	return 0;
299}
300EXPORT_SYMBOL_GPL(auxiliary_device_init);
301
302/**
303 * __auxiliary_device_add - add an auxiliary bus device
304 * @auxdev: auxiliary bus device to add to the bus
305 * @modname: name of the parent device's driver module
306 *
307 * This is the third step in the three-step process to register an
308 * auxiliary_device.
309 *
310 * This function must be called after a successful call to
311 * auxiliary_device_init(), which will perform the device_initialize.  This
312 * means that if this returns an error code, then a call to
313 * auxiliary_device_uninit() must be performed so that the .release callback
314 * will be triggered to free the memory associated with the auxiliary_device.
315 *
316 * The expectation is that users will call the "auxiliary_device_add" macro so
317 * that the caller's KBUILD_MODNAME is automatically inserted for the modname
318 * parameter.  Only if a user requires a custom name would this version be
319 * called directly.
320 */
321int __auxiliary_device_add(struct auxiliary_device *auxdev, const char *modname)
322{
323	struct device *dev = &auxdev->dev;
324	int ret;
325
326	if (!modname) {
327		dev_err(dev, "auxiliary device modname is NULL\n");
328		return -EINVAL;
329	}
330
331	ret = dev_set_name(dev, "%s.%s.%d", modname, auxdev->name, auxdev->id);
332	if (ret) {
333		dev_err(dev, "auxiliary device dev_set_name failed: %d\n", ret);
334		return ret;
335	}
336
337	ret = device_add(dev);
338	if (ret)
339		dev_err(dev, "adding auxiliary device failed!: %d\n", ret);
340
341	return ret;
342}
343EXPORT_SYMBOL_GPL(__auxiliary_device_add);
344
345/**
346 * __auxiliary_driver_register - register a driver for auxiliary bus devices
347 * @auxdrv: auxiliary_driver structure
348 * @owner: owning module/driver
349 * @modname: KBUILD_MODNAME for parent driver
350 *
351 * The expectation is that users will call the "auxiliary_driver_register"
352 * macro so that the caller's KBUILD_MODNAME is automatically inserted for the
353 * modname parameter.  Only if a user requires a custom name would this version
354 * be called directly.
355 */
356int __auxiliary_driver_register(struct auxiliary_driver *auxdrv,
357				struct module *owner, const char *modname)
358{
359	int ret;
360
361	if (WARN_ON(!auxdrv->probe) || WARN_ON(!auxdrv->id_table))
362		return -EINVAL;
363
364	if (auxdrv->name)
365		auxdrv->driver.name = kasprintf(GFP_KERNEL, "%s.%s", modname,
366						auxdrv->name);
367	else
368		auxdrv->driver.name = kasprintf(GFP_KERNEL, "%s", modname);
369	if (!auxdrv->driver.name)
370		return -ENOMEM;
371
372	auxdrv->driver.owner = owner;
373	auxdrv->driver.bus = &auxiliary_bus_type;
374	auxdrv->driver.mod_name = modname;
375
376	ret = driver_register(&auxdrv->driver);
377	if (ret)
378		kfree(auxdrv->driver.name);
379
380	return ret;
381}
382EXPORT_SYMBOL_GPL(__auxiliary_driver_register);
383
384/**
385 * auxiliary_driver_unregister - unregister a driver
386 * @auxdrv: auxiliary_driver structure
387 */
388void auxiliary_driver_unregister(struct auxiliary_driver *auxdrv)
389{
390	driver_unregister(&auxdrv->driver);
391	kfree(auxdrv->driver.name);
392}
393EXPORT_SYMBOL_GPL(auxiliary_driver_unregister);
394
395static void auxiliary_device_release(struct device *dev)
396{
397	struct auxiliary_device *auxdev = to_auxiliary_dev(dev);
398
399	of_node_put(dev->of_node);
400	kfree(auxdev);
401}
402
403/**
404 * auxiliary_device_create - create a device on the auxiliary bus
405 * @dev: parent device
406 * @modname: module name used to create the auxiliary driver name.
407 * @devname: auxiliary bus device name
408 * @platform_data: auxiliary bus device platform data
409 * @id: auxiliary bus device id
410 *
411 * Helper to create an auxiliary bus device.
412 * The device created matches driver 'modname.devname' on the auxiliary bus.
413 */
414struct auxiliary_device *auxiliary_device_create(struct device *dev,
415						 const char *modname,
416						 const char *devname,
417						 void *platform_data,
418						 int id)
419{
420	struct auxiliary_device *auxdev;
421	int ret;
422
423	auxdev = kzalloc(sizeof(*auxdev), GFP_KERNEL);
424	if (!auxdev)
425		return NULL;
426
427	auxdev->id = id;
428	auxdev->name = devname;
429	auxdev->dev.parent = dev;
430	auxdev->dev.platform_data = platform_data;
431	auxdev->dev.release = auxiliary_device_release;
432	device_set_of_node_from_dev(&auxdev->dev, dev);
433
434	ret = auxiliary_device_init(auxdev);
435	if (ret) {
436		of_node_put(auxdev->dev.of_node);
437		kfree(auxdev);
438		return NULL;
439	}
440
441	ret = __auxiliary_device_add(auxdev, modname);
442	if (ret) {
443		/*
444		 * It may look odd but auxdev should not be freed here.
445		 * auxiliary_device_uninit() calls device_put() which call
446		 * the device release function, freeing auxdev.
447		 */
448		auxiliary_device_uninit(auxdev);
449		return NULL;
450	}
451
452	return auxdev;
453}
454EXPORT_SYMBOL_GPL(auxiliary_device_create);
455
456/**
457 * auxiliary_device_destroy - remove an auxiliary device
458 * @auxdev: pointer to the auxdev to be removed
459 *
460 * Helper to remove an auxiliary device created with
461 * auxiliary_device_create()
462 */
463void auxiliary_device_destroy(void *auxdev)
464{
465	struct auxiliary_device *_auxdev = auxdev;
466
467	auxiliary_device_delete(_auxdev);
468	auxiliary_device_uninit(_auxdev);
469}
470EXPORT_SYMBOL_GPL(auxiliary_device_destroy);
471
472/**
473 * __devm_auxiliary_device_create - create a managed device on the auxiliary bus
474 * @dev: parent device
475 * @modname: module name used to create the auxiliary driver name.
476 * @devname: auxiliary bus device name
477 * @platform_data: auxiliary bus device platform data
478 * @id: auxiliary bus device id
479 *
480 * Device managed helper to create an auxiliary bus device.
481 * The device created matches driver 'modname.devname' on the auxiliary bus.
482 */
483struct auxiliary_device *__devm_auxiliary_device_create(struct device *dev,
484							const char *modname,
485							const char *devname,
486							void *platform_data,
487							int id)
488{
489	struct auxiliary_device *auxdev;
490	int ret;
491
492	auxdev = auxiliary_device_create(dev, modname, devname, platform_data, id);
493	if (!auxdev)
494		return NULL;
495
496	ret = devm_add_action_or_reset(dev, auxiliary_device_destroy,
497				       auxdev);
498	if (ret)
499		return NULL;
500
501	return auxdev;
502}
503EXPORT_SYMBOL_GPL(__devm_auxiliary_device_create);
504
505void __init auxiliary_bus_init(void)
506{
507	WARN_ON(bus_register(&auxiliary_bus_type));
508}