xref: /linux/drivers/base/dd.c (revision 3839a7460721b87501134697b7b90c45dcc7825d)
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * drivers/base/dd.c - The core device/driver interactions.
4  *
5  * This file contains the (sometimes tricky) code that controls the
6  * interactions between devices and drivers, which primarily includes
7  * driver binding and unbinding.
8  *
9  * All of this code used to exist in drivers/base/bus.c, but was
10  * relocated to here in the name of compartmentalization (since it wasn't
11  * strictly code just for the 'struct bus_type'.
12  *
13  * Copyright (c) 2002-5 Patrick Mochel
14  * Copyright (c) 2002-3 Open Source Development Labs
15  * Copyright (c) 2007-2009 Greg Kroah-Hartman <gregkh@suse.de>
16  * Copyright (c) 2007-2009 Novell Inc.
17  */
18 
19 #include <linux/debugfs.h>
20 #include <linux/device.h>
21 #include <linux/delay.h>
22 #include <linux/dma-mapping.h>
23 #include <linux/init.h>
24 #include <linux/module.h>
25 #include <linux/kthread.h>
26 #include <linux/wait.h>
27 #include <linux/async.h>
28 #include <linux/pm_runtime.h>
29 #include <linux/pinctrl/devinfo.h>
30 
31 #include "base.h"
32 #include "power/power.h"
33 
34 /*
35  * Deferred Probe infrastructure.
36  *
37  * Sometimes driver probe order matters, but the kernel doesn't always have
38  * dependency information which means some drivers will get probed before a
39  * resource it depends on is available.  For example, an SDHCI driver may
40  * first need a GPIO line from an i2c GPIO controller before it can be
41  * initialized.  If a required resource is not available yet, a driver can
42  * request probing to be deferred by returning -EPROBE_DEFER from its probe hook
43  *
44  * Deferred probe maintains two lists of devices, a pending list and an active
45  * list.  A driver returning -EPROBE_DEFER causes the device to be added to the
46  * pending list.  A successful driver probe will trigger moving all devices
47  * from the pending to the active list so that the workqueue will eventually
48  * retry them.
49  *
50  * The deferred_probe_mutex must be held any time the deferred_probe_*_list
51  * of the (struct device*)->p->deferred_probe pointers are manipulated
52  */
53 static DEFINE_MUTEX(deferred_probe_mutex);
54 static LIST_HEAD(deferred_probe_pending_list);
55 static LIST_HEAD(deferred_probe_active_list);
56 static atomic_t deferred_trigger_count = ATOMIC_INIT(0);
57 static struct dentry *deferred_devices;
58 static bool initcalls_done;
59 
60 /* Save the async probe drivers' name from kernel cmdline */
61 #define ASYNC_DRV_NAMES_MAX_LEN	256
62 static char async_probe_drv_names[ASYNC_DRV_NAMES_MAX_LEN];
63 
64 /*
65  * In some cases, like suspend to RAM or hibernation, It might be reasonable
66  * to prohibit probing of devices as it could be unsafe.
67  * Once defer_all_probes is true all drivers probes will be forcibly deferred.
68  */
69 static bool defer_all_probes;
70 
71 /*
72  * deferred_probe_work_func() - Retry probing devices in the active list.
73  */
74 static void deferred_probe_work_func(struct work_struct *work)
75 {
76 	struct device *dev;
77 	struct device_private *private;
78 	/*
79 	 * This block processes every device in the deferred 'active' list.
80 	 * Each device is removed from the active list and passed to
81 	 * bus_probe_device() to re-attempt the probe.  The loop continues
82 	 * until every device in the active list is removed and retried.
83 	 *
84 	 * Note: Once the device is removed from the list and the mutex is
85 	 * released, it is possible for the device get freed by another thread
86 	 * and cause a illegal pointer dereference.  This code uses
87 	 * get/put_device() to ensure the device structure cannot disappear
88 	 * from under our feet.
89 	 */
90 	mutex_lock(&deferred_probe_mutex);
91 	while (!list_empty(&deferred_probe_active_list)) {
92 		private = list_first_entry(&deferred_probe_active_list,
93 					typeof(*dev->p), deferred_probe);
94 		dev = private->device;
95 		list_del_init(&private->deferred_probe);
96 
97 		get_device(dev);
98 
99 		/*
100 		 * Drop the mutex while probing each device; the probe path may
101 		 * manipulate the deferred list
102 		 */
103 		mutex_unlock(&deferred_probe_mutex);
104 
105 		/*
106 		 * Force the device to the end of the dpm_list since
107 		 * the PM code assumes that the order we add things to
108 		 * the list is a good order for suspend but deferred
109 		 * probe makes that very unsafe.
110 		 */
111 		device_pm_move_to_tail(dev);
112 
113 		dev_dbg(dev, "Retrying from deferred list\n");
114 		bus_probe_device(dev);
115 		mutex_lock(&deferred_probe_mutex);
116 
117 		put_device(dev);
118 	}
119 	mutex_unlock(&deferred_probe_mutex);
120 }
121 static DECLARE_WORK(deferred_probe_work, deferred_probe_work_func);
122 
123 void driver_deferred_probe_add(struct device *dev)
124 {
125 	mutex_lock(&deferred_probe_mutex);
126 	if (list_empty(&dev->p->deferred_probe)) {
127 		dev_dbg(dev, "Added to deferred list\n");
128 		list_add_tail(&dev->p->deferred_probe, &deferred_probe_pending_list);
129 	}
130 	mutex_unlock(&deferred_probe_mutex);
131 }
132 
133 void driver_deferred_probe_del(struct device *dev)
134 {
135 	mutex_lock(&deferred_probe_mutex);
136 	if (!list_empty(&dev->p->deferred_probe)) {
137 		dev_dbg(dev, "Removed from deferred list\n");
138 		list_del_init(&dev->p->deferred_probe);
139 	}
140 	mutex_unlock(&deferred_probe_mutex);
141 }
142 
143 static bool driver_deferred_probe_enable = false;
144 /**
145  * driver_deferred_probe_trigger() - Kick off re-probing deferred devices
146  *
147  * This functions moves all devices from the pending list to the active
148  * list and schedules the deferred probe workqueue to process them.  It
149  * should be called anytime a driver is successfully bound to a device.
150  *
151  * Note, there is a race condition in multi-threaded probe. In the case where
152  * more than one device is probing at the same time, it is possible for one
153  * probe to complete successfully while another is about to defer. If the second
154  * depends on the first, then it will get put on the pending list after the
155  * trigger event has already occurred and will be stuck there.
156  *
157  * The atomic 'deferred_trigger_count' is used to determine if a successful
158  * trigger has occurred in the midst of probing a driver. If the trigger count
159  * changes in the midst of a probe, then deferred processing should be triggered
160  * again.
161  */
162 static void driver_deferred_probe_trigger(void)
163 {
164 	if (!driver_deferred_probe_enable)
165 		return;
166 
167 	driver_deferred_probe_force_trigger();
168 }
169 
170 void driver_deferred_probe_force_trigger(void)
171 {
172 	/*
173 	 * A successful probe means that all the devices in the pending list
174 	 * should be triggered to be reprobed.  Move all the deferred devices
175 	 * into the active list so they can be retried by the workqueue
176 	 */
177 	mutex_lock(&deferred_probe_mutex);
178 	atomic_inc(&deferred_trigger_count);
179 	list_splice_tail_init(&deferred_probe_pending_list,
180 			      &deferred_probe_active_list);
181 	mutex_unlock(&deferred_probe_mutex);
182 
183 	/*
184 	 * Kick the re-probe thread.  It may already be scheduled, but it is
185 	 * safe to kick it again.
186 	 */
187 	schedule_work(&deferred_probe_work);
188 }
189 
190 /**
191  * device_block_probing() - Block/defer device's probes
192  *
193  *	It will disable probing of devices and defer their probes instead.
194  */
195 void device_block_probing(void)
196 {
197 	defer_all_probes = true;
198 	/* sync with probes to avoid races. */
199 	wait_for_device_probe();
200 }
201 
202 /**
203  * device_unblock_probing() - Unblock/enable device's probes
204  *
205  *	It will restore normal behavior and trigger re-probing of deferred
206  * devices.
207  */
208 void device_unblock_probing(void)
209 {
210 	defer_all_probes = false;
211 	driver_deferred_probe_trigger();
212 }
213 
214 /*
215  * deferred_devs_show() - Show the devices in the deferred probe pending list.
216  */
217 static int deferred_devs_show(struct seq_file *s, void *data)
218 {
219 	struct device_private *curr;
220 
221 	mutex_lock(&deferred_probe_mutex);
222 
223 	list_for_each_entry(curr, &deferred_probe_pending_list, deferred_probe)
224 		seq_printf(s, "%s\n", dev_name(curr->device));
225 
226 	mutex_unlock(&deferred_probe_mutex);
227 
228 	return 0;
229 }
230 DEFINE_SHOW_ATTRIBUTE(deferred_devs);
231 
232 int driver_deferred_probe_timeout;
233 EXPORT_SYMBOL_GPL(driver_deferred_probe_timeout);
234 static DECLARE_WAIT_QUEUE_HEAD(probe_timeout_waitqueue);
235 
236 static int __init deferred_probe_timeout_setup(char *str)
237 {
238 	int timeout;
239 
240 	if (!kstrtoint(str, 10, &timeout))
241 		driver_deferred_probe_timeout = timeout;
242 	return 1;
243 }
244 __setup("deferred_probe_timeout=", deferred_probe_timeout_setup);
245 
246 /**
247  * driver_deferred_probe_check_state() - Check deferred probe state
248  * @dev: device to check
249  *
250  * Return:
251  * -ENODEV if initcalls have completed and modules are disabled.
252  * -ETIMEDOUT if the deferred probe timeout was set and has expired
253  *  and modules are enabled.
254  * -EPROBE_DEFER in other cases.
255  *
256  * Drivers or subsystems can opt-in to calling this function instead of directly
257  * returning -EPROBE_DEFER.
258  */
259 int driver_deferred_probe_check_state(struct device *dev)
260 {
261 	if (!IS_ENABLED(CONFIG_MODULES) && initcalls_done) {
262 		dev_warn(dev, "ignoring dependency for device, assuming no driver\n");
263 		return -ENODEV;
264 	}
265 
266 	if (!driver_deferred_probe_timeout && initcalls_done) {
267 		dev_warn(dev, "deferred probe timeout, ignoring dependency\n");
268 		return -ETIMEDOUT;
269 	}
270 
271 	return -EPROBE_DEFER;
272 }
273 
274 static void deferred_probe_timeout_work_func(struct work_struct *work)
275 {
276 	struct device_private *private, *p;
277 
278 	driver_deferred_probe_timeout = 0;
279 	driver_deferred_probe_trigger();
280 	flush_work(&deferred_probe_work);
281 
282 	list_for_each_entry_safe(private, p, &deferred_probe_pending_list, deferred_probe)
283 		dev_info(private->device, "deferred probe pending\n");
284 	wake_up(&probe_timeout_waitqueue);
285 }
286 static DECLARE_DELAYED_WORK(deferred_probe_timeout_work, deferred_probe_timeout_work_func);
287 
288 /**
289  * deferred_probe_initcall() - Enable probing of deferred devices
290  *
291  * We don't want to get in the way when the bulk of drivers are getting probed.
292  * Instead, this initcall makes sure that deferred probing is delayed until
293  * late_initcall time.
294  */
295 static int deferred_probe_initcall(void)
296 {
297 	deferred_devices = debugfs_create_file("devices_deferred", 0444, NULL,
298 					       NULL, &deferred_devs_fops);
299 
300 	driver_deferred_probe_enable = true;
301 	driver_deferred_probe_trigger();
302 	/* Sort as many dependencies as possible before exiting initcalls */
303 	flush_work(&deferred_probe_work);
304 	initcalls_done = true;
305 
306 	/*
307 	 * Trigger deferred probe again, this time we won't defer anything
308 	 * that is optional
309 	 */
310 	driver_deferred_probe_trigger();
311 	flush_work(&deferred_probe_work);
312 
313 	if (driver_deferred_probe_timeout > 0) {
314 		schedule_delayed_work(&deferred_probe_timeout_work,
315 			driver_deferred_probe_timeout * HZ);
316 	}
317 	return 0;
318 }
319 late_initcall(deferred_probe_initcall);
320 
321 static void __exit deferred_probe_exit(void)
322 {
323 	debugfs_remove_recursive(deferred_devices);
324 }
325 __exitcall(deferred_probe_exit);
326 
327 /**
328  * device_is_bound() - Check if device is bound to a driver
329  * @dev: device to check
330  *
331  * Returns true if passed device has already finished probing successfully
332  * against a driver.
333  *
334  * This function must be called with the device lock held.
335  */
336 bool device_is_bound(struct device *dev)
337 {
338 	return dev->p && klist_node_attached(&dev->p->knode_driver);
339 }
340 
341 static void driver_bound(struct device *dev)
342 {
343 	if (device_is_bound(dev)) {
344 		pr_warn("%s: device %s already bound\n",
345 			__func__, kobject_name(&dev->kobj));
346 		return;
347 	}
348 
349 	pr_debug("driver: '%s': %s: bound to device '%s'\n", dev->driver->name,
350 		 __func__, dev_name(dev));
351 
352 	klist_add_tail(&dev->p->knode_driver, &dev->driver->p->klist_devices);
353 	device_links_driver_bound(dev);
354 
355 	device_pm_check_callbacks(dev);
356 
357 	/*
358 	 * Make sure the device is no longer in one of the deferred lists and
359 	 * kick off retrying all pending devices
360 	 */
361 	driver_deferred_probe_del(dev);
362 	driver_deferred_probe_trigger();
363 
364 	if (dev->bus)
365 		blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
366 					     BUS_NOTIFY_BOUND_DRIVER, dev);
367 
368 	kobject_uevent(&dev->kobj, KOBJ_BIND);
369 }
370 
371 static ssize_t coredump_store(struct device *dev, struct device_attribute *attr,
372 			    const char *buf, size_t count)
373 {
374 	device_lock(dev);
375 	dev->driver->coredump(dev);
376 	device_unlock(dev);
377 
378 	return count;
379 }
380 static DEVICE_ATTR_WO(coredump);
381 
382 static int driver_sysfs_add(struct device *dev)
383 {
384 	int ret;
385 
386 	if (dev->bus)
387 		blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
388 					     BUS_NOTIFY_BIND_DRIVER, dev);
389 
390 	ret = sysfs_create_link(&dev->driver->p->kobj, &dev->kobj,
391 				kobject_name(&dev->kobj));
392 	if (ret)
393 		goto fail;
394 
395 	ret = sysfs_create_link(&dev->kobj, &dev->driver->p->kobj,
396 				"driver");
397 	if (ret)
398 		goto rm_dev;
399 
400 	if (!IS_ENABLED(CONFIG_DEV_COREDUMP) || !dev->driver->coredump ||
401 	    !device_create_file(dev, &dev_attr_coredump))
402 		return 0;
403 
404 	sysfs_remove_link(&dev->kobj, "driver");
405 
406 rm_dev:
407 	sysfs_remove_link(&dev->driver->p->kobj,
408 			  kobject_name(&dev->kobj));
409 
410 fail:
411 	return ret;
412 }
413 
414 static void driver_sysfs_remove(struct device *dev)
415 {
416 	struct device_driver *drv = dev->driver;
417 
418 	if (drv) {
419 		if (drv->coredump)
420 			device_remove_file(dev, &dev_attr_coredump);
421 		sysfs_remove_link(&drv->p->kobj, kobject_name(&dev->kobj));
422 		sysfs_remove_link(&dev->kobj, "driver");
423 	}
424 }
425 
426 /**
427  * device_bind_driver - bind a driver to one device.
428  * @dev: device.
429  *
430  * Allow manual attachment of a driver to a device.
431  * Caller must have already set @dev->driver.
432  *
433  * Note that this does not modify the bus reference count
434  * nor take the bus's rwsem. Please verify those are accounted
435  * for before calling this. (It is ok to call with no other effort
436  * from a driver's probe() method.)
437  *
438  * This function must be called with the device lock held.
439  */
440 int device_bind_driver(struct device *dev)
441 {
442 	int ret;
443 
444 	ret = driver_sysfs_add(dev);
445 	if (!ret)
446 		driver_bound(dev);
447 	else if (dev->bus)
448 		blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
449 					     BUS_NOTIFY_DRIVER_NOT_BOUND, dev);
450 	return ret;
451 }
452 EXPORT_SYMBOL_GPL(device_bind_driver);
453 
454 static atomic_t probe_count = ATOMIC_INIT(0);
455 static DECLARE_WAIT_QUEUE_HEAD(probe_waitqueue);
456 
457 static void driver_deferred_probe_add_trigger(struct device *dev,
458 					      int local_trigger_count)
459 {
460 	driver_deferred_probe_add(dev);
461 	/* Did a trigger occur while probing? Need to re-trigger if yes */
462 	if (local_trigger_count != atomic_read(&deferred_trigger_count))
463 		driver_deferred_probe_trigger();
464 }
465 
466 static int really_probe(struct device *dev, struct device_driver *drv)
467 {
468 	int ret = -EPROBE_DEFER;
469 	int local_trigger_count = atomic_read(&deferred_trigger_count);
470 	bool test_remove = IS_ENABLED(CONFIG_DEBUG_TEST_DRIVER_REMOVE) &&
471 			   !drv->suppress_bind_attrs;
472 
473 	if (defer_all_probes) {
474 		/*
475 		 * Value of defer_all_probes can be set only by
476 		 * device_block_probing() which, in turn, will call
477 		 * wait_for_device_probe() right after that to avoid any races.
478 		 */
479 		dev_dbg(dev, "Driver %s force probe deferral\n", drv->name);
480 		driver_deferred_probe_add(dev);
481 		return ret;
482 	}
483 
484 	ret = device_links_check_suppliers(dev);
485 	if (ret == -EPROBE_DEFER)
486 		driver_deferred_probe_add_trigger(dev, local_trigger_count);
487 	if (ret)
488 		return ret;
489 
490 	atomic_inc(&probe_count);
491 	pr_debug("bus: '%s': %s: probing driver %s with device %s\n",
492 		 drv->bus->name, __func__, drv->name, dev_name(dev));
493 	if (!list_empty(&dev->devres_head)) {
494 		dev_crit(dev, "Resources present before probing\n");
495 		return -EBUSY;
496 	}
497 
498 re_probe:
499 	dev->driver = drv;
500 
501 	/* If using pinctrl, bind pins now before probing */
502 	ret = pinctrl_bind_pins(dev);
503 	if (ret)
504 		goto pinctrl_bind_failed;
505 
506 	if (dev->bus->dma_configure) {
507 		ret = dev->bus->dma_configure(dev);
508 		if (ret)
509 			goto probe_failed;
510 	}
511 
512 	if (driver_sysfs_add(dev)) {
513 		pr_err("%s: driver_sysfs_add(%s) failed\n",
514 		       __func__, dev_name(dev));
515 		goto probe_failed;
516 	}
517 
518 	if (dev->pm_domain && dev->pm_domain->activate) {
519 		ret = dev->pm_domain->activate(dev);
520 		if (ret)
521 			goto probe_failed;
522 	}
523 
524 	if (dev->bus->probe) {
525 		ret = dev->bus->probe(dev);
526 		if (ret)
527 			goto probe_failed;
528 	} else if (drv->probe) {
529 		ret = drv->probe(dev);
530 		if (ret)
531 			goto probe_failed;
532 	}
533 
534 	if (device_add_groups(dev, drv->dev_groups)) {
535 		dev_err(dev, "device_add_groups() failed\n");
536 		goto dev_groups_failed;
537 	}
538 
539 	if (test_remove) {
540 		test_remove = false;
541 
542 		device_remove_groups(dev, drv->dev_groups);
543 
544 		if (dev->bus->remove)
545 			dev->bus->remove(dev);
546 		else if (drv->remove)
547 			drv->remove(dev);
548 
549 		devres_release_all(dev);
550 		driver_sysfs_remove(dev);
551 		dev->driver = NULL;
552 		dev_set_drvdata(dev, NULL);
553 		if (dev->pm_domain && dev->pm_domain->dismiss)
554 			dev->pm_domain->dismiss(dev);
555 		pm_runtime_reinit(dev);
556 
557 		goto re_probe;
558 	}
559 
560 	pinctrl_init_done(dev);
561 
562 	if (dev->pm_domain && dev->pm_domain->sync)
563 		dev->pm_domain->sync(dev);
564 
565 	driver_bound(dev);
566 	ret = 1;
567 	pr_debug("bus: '%s': %s: bound device %s to driver %s\n",
568 		 drv->bus->name, __func__, dev_name(dev), drv->name);
569 	goto done;
570 
571 dev_groups_failed:
572 	if (dev->bus->remove)
573 		dev->bus->remove(dev);
574 	else if (drv->remove)
575 		drv->remove(dev);
576 probe_failed:
577 	if (dev->bus)
578 		blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
579 					     BUS_NOTIFY_DRIVER_NOT_BOUND, dev);
580 pinctrl_bind_failed:
581 	device_links_no_driver(dev);
582 	devres_release_all(dev);
583 	arch_teardown_dma_ops(dev);
584 	driver_sysfs_remove(dev);
585 	dev->driver = NULL;
586 	dev_set_drvdata(dev, NULL);
587 	if (dev->pm_domain && dev->pm_domain->dismiss)
588 		dev->pm_domain->dismiss(dev);
589 	pm_runtime_reinit(dev);
590 	dev_pm_set_driver_flags(dev, 0);
591 
592 	switch (ret) {
593 	case -EPROBE_DEFER:
594 		/* Driver requested deferred probing */
595 		dev_dbg(dev, "Driver %s requests probe deferral\n", drv->name);
596 		driver_deferred_probe_add_trigger(dev, local_trigger_count);
597 		break;
598 	case -ENODEV:
599 	case -ENXIO:
600 		pr_debug("%s: probe of %s rejects match %d\n",
601 			 drv->name, dev_name(dev), ret);
602 		break;
603 	default:
604 		/* driver matched but the probe failed */
605 		pr_warn("%s: probe of %s failed with error %d\n",
606 			drv->name, dev_name(dev), ret);
607 	}
608 	/*
609 	 * Ignore errors returned by ->probe so that the next driver can try
610 	 * its luck.
611 	 */
612 	ret = 0;
613 done:
614 	atomic_dec(&probe_count);
615 	wake_up(&probe_waitqueue);
616 	return ret;
617 }
618 
619 /*
620  * For initcall_debug, show the driver probe time.
621  */
622 static int really_probe_debug(struct device *dev, struct device_driver *drv)
623 {
624 	ktime_t calltime, delta, rettime;
625 	int ret;
626 
627 	calltime = ktime_get();
628 	ret = really_probe(dev, drv);
629 	rettime = ktime_get();
630 	delta = ktime_sub(rettime, calltime);
631 	pr_debug("probe of %s returned %d after %lld usecs\n",
632 		 dev_name(dev), ret, (s64) ktime_to_us(delta));
633 	return ret;
634 }
635 
636 /**
637  * driver_probe_done
638  * Determine if the probe sequence is finished or not.
639  *
640  * Should somehow figure out how to use a semaphore, not an atomic variable...
641  */
642 int driver_probe_done(void)
643 {
644 	int local_probe_count = atomic_read(&probe_count);
645 
646 	pr_debug("%s: probe_count = %d\n", __func__, local_probe_count);
647 	if (local_probe_count)
648 		return -EBUSY;
649 	return 0;
650 }
651 
652 /**
653  * wait_for_device_probe
654  * Wait for device probing to be completed.
655  */
656 void wait_for_device_probe(void)
657 {
658 	/* wait for probe timeout */
659 	wait_event(probe_timeout_waitqueue, !driver_deferred_probe_timeout);
660 
661 	/* wait for the deferred probe workqueue to finish */
662 	flush_work(&deferred_probe_work);
663 
664 	/* wait for the known devices to complete their probing */
665 	wait_event(probe_waitqueue, atomic_read(&probe_count) == 0);
666 	async_synchronize_full();
667 }
668 EXPORT_SYMBOL_GPL(wait_for_device_probe);
669 
670 /**
671  * driver_probe_device - attempt to bind device & driver together
672  * @drv: driver to bind a device to
673  * @dev: device to try to bind to the driver
674  *
675  * This function returns -ENODEV if the device is not registered,
676  * 1 if the device is bound successfully and 0 otherwise.
677  *
678  * This function must be called with @dev lock held.  When called for a
679  * USB interface, @dev->parent lock must be held as well.
680  *
681  * If the device has a parent, runtime-resume the parent before driver probing.
682  */
683 int driver_probe_device(struct device_driver *drv, struct device *dev)
684 {
685 	int ret = 0;
686 
687 	if (!device_is_registered(dev))
688 		return -ENODEV;
689 
690 	pr_debug("bus: '%s': %s: matched device %s with driver %s\n",
691 		 drv->bus->name, __func__, dev_name(dev), drv->name);
692 
693 	pm_runtime_get_suppliers(dev);
694 	if (dev->parent)
695 		pm_runtime_get_sync(dev->parent);
696 
697 	pm_runtime_barrier(dev);
698 	if (initcall_debug)
699 		ret = really_probe_debug(dev, drv);
700 	else
701 		ret = really_probe(dev, drv);
702 	pm_request_idle(dev);
703 
704 	if (dev->parent)
705 		pm_runtime_put(dev->parent);
706 
707 	pm_runtime_put_suppliers(dev);
708 	return ret;
709 }
710 
711 static inline bool cmdline_requested_async_probing(const char *drv_name)
712 {
713 	return parse_option_str(async_probe_drv_names, drv_name);
714 }
715 
716 /* The option format is "driver_async_probe=drv_name1,drv_name2,..." */
717 static int __init save_async_options(char *buf)
718 {
719 	if (strlen(buf) >= ASYNC_DRV_NAMES_MAX_LEN)
720 		pr_warn("Too long list of driver names for 'driver_async_probe'!\n");
721 
722 	strlcpy(async_probe_drv_names, buf, ASYNC_DRV_NAMES_MAX_LEN);
723 	return 0;
724 }
725 __setup("driver_async_probe=", save_async_options);
726 
727 bool driver_allows_async_probing(struct device_driver *drv)
728 {
729 	switch (drv->probe_type) {
730 	case PROBE_PREFER_ASYNCHRONOUS:
731 		return true;
732 
733 	case PROBE_FORCE_SYNCHRONOUS:
734 		return false;
735 
736 	default:
737 		if (cmdline_requested_async_probing(drv->name))
738 			return true;
739 
740 		if (module_requested_async_probing(drv->owner))
741 			return true;
742 
743 		return false;
744 	}
745 }
746 
747 struct device_attach_data {
748 	struct device *dev;
749 
750 	/*
751 	 * Indicates whether we are are considering asynchronous probing or
752 	 * not. Only initial binding after device or driver registration
753 	 * (including deferral processing) may be done asynchronously, the
754 	 * rest is always synchronous, as we expect it is being done by
755 	 * request from userspace.
756 	 */
757 	bool check_async;
758 
759 	/*
760 	 * Indicates if we are binding synchronous or asynchronous drivers.
761 	 * When asynchronous probing is enabled we'll execute 2 passes
762 	 * over drivers: first pass doing synchronous probing and second
763 	 * doing asynchronous probing (if synchronous did not succeed -
764 	 * most likely because there was no driver requiring synchronous
765 	 * probing - and we found asynchronous driver during first pass).
766 	 * The 2 passes are done because we can't shoot asynchronous
767 	 * probe for given device and driver from bus_for_each_drv() since
768 	 * driver pointer is not guaranteed to stay valid once
769 	 * bus_for_each_drv() iterates to the next driver on the bus.
770 	 */
771 	bool want_async;
772 
773 	/*
774 	 * We'll set have_async to 'true' if, while scanning for matching
775 	 * driver, we'll encounter one that requests asynchronous probing.
776 	 */
777 	bool have_async;
778 };
779 
780 static int __device_attach_driver(struct device_driver *drv, void *_data)
781 {
782 	struct device_attach_data *data = _data;
783 	struct device *dev = data->dev;
784 	bool async_allowed;
785 	int ret;
786 
787 	ret = driver_match_device(drv, dev);
788 	if (ret == 0) {
789 		/* no match */
790 		return 0;
791 	} else if (ret == -EPROBE_DEFER) {
792 		dev_dbg(dev, "Device match requests probe deferral\n");
793 		driver_deferred_probe_add(dev);
794 	} else if (ret < 0) {
795 		dev_dbg(dev, "Bus failed to match device: %d\n", ret);
796 		return ret;
797 	} /* ret > 0 means positive match */
798 
799 	async_allowed = driver_allows_async_probing(drv);
800 
801 	if (async_allowed)
802 		data->have_async = true;
803 
804 	if (data->check_async && async_allowed != data->want_async)
805 		return 0;
806 
807 	return driver_probe_device(drv, dev);
808 }
809 
810 static void __device_attach_async_helper(void *_dev, async_cookie_t cookie)
811 {
812 	struct device *dev = _dev;
813 	struct device_attach_data data = {
814 		.dev		= dev,
815 		.check_async	= true,
816 		.want_async	= true,
817 	};
818 
819 	device_lock(dev);
820 
821 	/*
822 	 * Check if device has already been removed or claimed. This may
823 	 * happen with driver loading, device discovery/registration,
824 	 * and deferred probe processing happens all at once with
825 	 * multiple threads.
826 	 */
827 	if (dev->p->dead || dev->driver)
828 		goto out_unlock;
829 
830 	if (dev->parent)
831 		pm_runtime_get_sync(dev->parent);
832 
833 	bus_for_each_drv(dev->bus, NULL, &data, __device_attach_driver);
834 	dev_dbg(dev, "async probe completed\n");
835 
836 	pm_request_idle(dev);
837 
838 	if (dev->parent)
839 		pm_runtime_put(dev->parent);
840 out_unlock:
841 	device_unlock(dev);
842 
843 	put_device(dev);
844 }
845 
846 static int __device_attach(struct device *dev, bool allow_async)
847 {
848 	int ret = 0;
849 
850 	device_lock(dev);
851 	if (dev->driver) {
852 		if (device_is_bound(dev)) {
853 			ret = 1;
854 			goto out_unlock;
855 		}
856 		ret = device_bind_driver(dev);
857 		if (ret == 0)
858 			ret = 1;
859 		else {
860 			dev->driver = NULL;
861 			ret = 0;
862 		}
863 	} else {
864 		struct device_attach_data data = {
865 			.dev = dev,
866 			.check_async = allow_async,
867 			.want_async = false,
868 		};
869 
870 		if (dev->parent)
871 			pm_runtime_get_sync(dev->parent);
872 
873 		ret = bus_for_each_drv(dev->bus, NULL, &data,
874 					__device_attach_driver);
875 		if (!ret && allow_async && data.have_async) {
876 			/*
877 			 * If we could not find appropriate driver
878 			 * synchronously and we are allowed to do
879 			 * async probes and there are drivers that
880 			 * want to probe asynchronously, we'll
881 			 * try them.
882 			 */
883 			dev_dbg(dev, "scheduling asynchronous probe\n");
884 			get_device(dev);
885 			async_schedule_dev(__device_attach_async_helper, dev);
886 		} else {
887 			pm_request_idle(dev);
888 		}
889 
890 		if (dev->parent)
891 			pm_runtime_put(dev->parent);
892 	}
893 out_unlock:
894 	device_unlock(dev);
895 	return ret;
896 }
897 
898 /**
899  * device_attach - try to attach device to a driver.
900  * @dev: device.
901  *
902  * Walk the list of drivers that the bus has and call
903  * driver_probe_device() for each pair. If a compatible
904  * pair is found, break out and return.
905  *
906  * Returns 1 if the device was bound to a driver;
907  * 0 if no matching driver was found;
908  * -ENODEV if the device is not registered.
909  *
910  * When called for a USB interface, @dev->parent lock must be held.
911  */
912 int device_attach(struct device *dev)
913 {
914 	return __device_attach(dev, false);
915 }
916 EXPORT_SYMBOL_GPL(device_attach);
917 
918 void device_initial_probe(struct device *dev)
919 {
920 	__device_attach(dev, true);
921 }
922 
923 /*
924  * __device_driver_lock - acquire locks needed to manipulate dev->drv
925  * @dev: Device we will update driver info for
926  * @parent: Parent device. Needed if the bus requires parent lock
927  *
928  * This function will take the required locks for manipulating dev->drv.
929  * Normally this will just be the @dev lock, but when called for a USB
930  * interface, @parent lock will be held as well.
931  */
932 static void __device_driver_lock(struct device *dev, struct device *parent)
933 {
934 	if (parent && dev->bus->need_parent_lock)
935 		device_lock(parent);
936 	device_lock(dev);
937 }
938 
939 /*
940  * __device_driver_unlock - release locks needed to manipulate dev->drv
941  * @dev: Device we will update driver info for
942  * @parent: Parent device. Needed if the bus requires parent lock
943  *
944  * This function will release the required locks for manipulating dev->drv.
945  * Normally this will just be the the @dev lock, but when called for a
946  * USB interface, @parent lock will be released as well.
947  */
948 static void __device_driver_unlock(struct device *dev, struct device *parent)
949 {
950 	device_unlock(dev);
951 	if (parent && dev->bus->need_parent_lock)
952 		device_unlock(parent);
953 }
954 
955 /**
956  * device_driver_attach - attach a specific driver to a specific device
957  * @drv: Driver to attach
958  * @dev: Device to attach it to
959  *
960  * Manually attach driver to a device. Will acquire both @dev lock and
961  * @dev->parent lock if needed.
962  */
963 int device_driver_attach(struct device_driver *drv, struct device *dev)
964 {
965 	int ret = 0;
966 
967 	__device_driver_lock(dev, dev->parent);
968 
969 	/*
970 	 * If device has been removed or someone has already successfully
971 	 * bound a driver before us just skip the driver probe call.
972 	 */
973 	if (!dev->p->dead && !dev->driver)
974 		ret = driver_probe_device(drv, dev);
975 
976 	__device_driver_unlock(dev, dev->parent);
977 
978 	return ret;
979 }
980 
981 static void __driver_attach_async_helper(void *_dev, async_cookie_t cookie)
982 {
983 	struct device *dev = _dev;
984 	struct device_driver *drv;
985 	int ret = 0;
986 
987 	__device_driver_lock(dev, dev->parent);
988 
989 	drv = dev->p->async_driver;
990 
991 	/*
992 	 * If device has been removed or someone has already successfully
993 	 * bound a driver before us just skip the driver probe call.
994 	 */
995 	if (!dev->p->dead && !dev->driver)
996 		ret = driver_probe_device(drv, dev);
997 
998 	__device_driver_unlock(dev, dev->parent);
999 
1000 	dev_dbg(dev, "driver %s async attach completed: %d\n", drv->name, ret);
1001 
1002 	put_device(dev);
1003 }
1004 
1005 static int __driver_attach(struct device *dev, void *data)
1006 {
1007 	struct device_driver *drv = data;
1008 	int ret;
1009 
1010 	/*
1011 	 * Lock device and try to bind to it. We drop the error
1012 	 * here and always return 0, because we need to keep trying
1013 	 * to bind to devices and some drivers will return an error
1014 	 * simply if it didn't support the device.
1015 	 *
1016 	 * driver_probe_device() will spit a warning if there
1017 	 * is an error.
1018 	 */
1019 
1020 	ret = driver_match_device(drv, dev);
1021 	if (ret == 0) {
1022 		/* no match */
1023 		return 0;
1024 	} else if (ret == -EPROBE_DEFER) {
1025 		dev_dbg(dev, "Device match requests probe deferral\n");
1026 		driver_deferred_probe_add(dev);
1027 	} else if (ret < 0) {
1028 		dev_dbg(dev, "Bus failed to match device: %d\n", ret);
1029 		return ret;
1030 	} /* ret > 0 means positive match */
1031 
1032 	if (driver_allows_async_probing(drv)) {
1033 		/*
1034 		 * Instead of probing the device synchronously we will
1035 		 * probe it asynchronously to allow for more parallelism.
1036 		 *
1037 		 * We only take the device lock here in order to guarantee
1038 		 * that the dev->driver and async_driver fields are protected
1039 		 */
1040 		dev_dbg(dev, "probing driver %s asynchronously\n", drv->name);
1041 		device_lock(dev);
1042 		if (!dev->driver) {
1043 			get_device(dev);
1044 			dev->p->async_driver = drv;
1045 			async_schedule_dev(__driver_attach_async_helper, dev);
1046 		}
1047 		device_unlock(dev);
1048 		return 0;
1049 	}
1050 
1051 	device_driver_attach(drv, dev);
1052 
1053 	return 0;
1054 }
1055 
1056 /**
1057  * driver_attach - try to bind driver to devices.
1058  * @drv: driver.
1059  *
1060  * Walk the list of devices that the bus has on it and try to
1061  * match the driver with each one.  If driver_probe_device()
1062  * returns 0 and the @dev->driver is set, we've found a
1063  * compatible pair.
1064  */
1065 int driver_attach(struct device_driver *drv)
1066 {
1067 	return bus_for_each_dev(drv->bus, NULL, drv, __driver_attach);
1068 }
1069 EXPORT_SYMBOL_GPL(driver_attach);
1070 
1071 /*
1072  * __device_release_driver() must be called with @dev lock held.
1073  * When called for a USB interface, @dev->parent lock must be held as well.
1074  */
1075 static void __device_release_driver(struct device *dev, struct device *parent)
1076 {
1077 	struct device_driver *drv;
1078 
1079 	drv = dev->driver;
1080 	if (drv) {
1081 		while (device_links_busy(dev)) {
1082 			__device_driver_unlock(dev, parent);
1083 
1084 			device_links_unbind_consumers(dev);
1085 
1086 			__device_driver_lock(dev, parent);
1087 			/*
1088 			 * A concurrent invocation of the same function might
1089 			 * have released the driver successfully while this one
1090 			 * was waiting, so check for that.
1091 			 */
1092 			if (dev->driver != drv)
1093 				return;
1094 		}
1095 
1096 		pm_runtime_get_sync(dev);
1097 		pm_runtime_clean_up_links(dev);
1098 
1099 		driver_sysfs_remove(dev);
1100 
1101 		if (dev->bus)
1102 			blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
1103 						     BUS_NOTIFY_UNBIND_DRIVER,
1104 						     dev);
1105 
1106 		pm_runtime_put_sync(dev);
1107 
1108 		device_remove_groups(dev, drv->dev_groups);
1109 
1110 		if (dev->bus && dev->bus->remove)
1111 			dev->bus->remove(dev);
1112 		else if (drv->remove)
1113 			drv->remove(dev);
1114 
1115 		device_links_driver_cleanup(dev);
1116 
1117 		devres_release_all(dev);
1118 		arch_teardown_dma_ops(dev);
1119 		dev->driver = NULL;
1120 		dev_set_drvdata(dev, NULL);
1121 		if (dev->pm_domain && dev->pm_domain->dismiss)
1122 			dev->pm_domain->dismiss(dev);
1123 		pm_runtime_reinit(dev);
1124 		dev_pm_set_driver_flags(dev, 0);
1125 
1126 		klist_remove(&dev->p->knode_driver);
1127 		device_pm_check_callbacks(dev);
1128 		if (dev->bus)
1129 			blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
1130 						     BUS_NOTIFY_UNBOUND_DRIVER,
1131 						     dev);
1132 
1133 		kobject_uevent(&dev->kobj, KOBJ_UNBIND);
1134 	}
1135 }
1136 
1137 void device_release_driver_internal(struct device *dev,
1138 				    struct device_driver *drv,
1139 				    struct device *parent)
1140 {
1141 	__device_driver_lock(dev, parent);
1142 
1143 	if (!drv || drv == dev->driver)
1144 		__device_release_driver(dev, parent);
1145 
1146 	__device_driver_unlock(dev, parent);
1147 }
1148 
1149 /**
1150  * device_release_driver - manually detach device from driver.
1151  * @dev: device.
1152  *
1153  * Manually detach device from driver.
1154  * When called for a USB interface, @dev->parent lock must be held.
1155  *
1156  * If this function is to be called with @dev->parent lock held, ensure that
1157  * the device's consumers are unbound in advance or that their locks can be
1158  * acquired under the @dev->parent lock.
1159  */
1160 void device_release_driver(struct device *dev)
1161 {
1162 	/*
1163 	 * If anyone calls device_release_driver() recursively from
1164 	 * within their ->remove callback for the same device, they
1165 	 * will deadlock right here.
1166 	 */
1167 	device_release_driver_internal(dev, NULL, NULL);
1168 }
1169 EXPORT_SYMBOL_GPL(device_release_driver);
1170 
1171 /**
1172  * device_driver_detach - detach driver from a specific device
1173  * @dev: device to detach driver from
1174  *
1175  * Detach driver from device. Will acquire both @dev lock and @dev->parent
1176  * lock if needed.
1177  */
1178 void device_driver_detach(struct device *dev)
1179 {
1180 	device_release_driver_internal(dev, NULL, dev->parent);
1181 }
1182 
1183 /**
1184  * driver_detach - detach driver from all devices it controls.
1185  * @drv: driver.
1186  */
1187 void driver_detach(struct device_driver *drv)
1188 {
1189 	struct device_private *dev_prv;
1190 	struct device *dev;
1191 
1192 	if (driver_allows_async_probing(drv))
1193 		async_synchronize_full();
1194 
1195 	for (;;) {
1196 		spin_lock(&drv->p->klist_devices.k_lock);
1197 		if (list_empty(&drv->p->klist_devices.k_list)) {
1198 			spin_unlock(&drv->p->klist_devices.k_lock);
1199 			break;
1200 		}
1201 		dev_prv = list_last_entry(&drv->p->klist_devices.k_list,
1202 				     struct device_private,
1203 				     knode_driver.n_node);
1204 		dev = dev_prv->device;
1205 		get_device(dev);
1206 		spin_unlock(&drv->p->klist_devices.k_lock);
1207 		device_release_driver_internal(dev, drv, dev->parent);
1208 		put_device(dev);
1209 	}
1210 }
1211