xref: /openbmc/linux/drivers/base/dd.c (revision 55eb9a6c)
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-map-ops.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 #include <linux/slab.h>
31 
32 #include "base.h"
33 #include "power/power.h"
34 
35 /*
36  * Deferred Probe infrastructure.
37  *
38  * Sometimes driver probe order matters, but the kernel doesn't always have
39  * dependency information which means some drivers will get probed before a
40  * resource it depends on is available.  For example, an SDHCI driver may
41  * first need a GPIO line from an i2c GPIO controller before it can be
42  * initialized.  If a required resource is not available yet, a driver can
43  * request probing to be deferred by returning -EPROBE_DEFER from its probe hook
44  *
45  * Deferred probe maintains two lists of devices, a pending list and an active
46  * list.  A driver returning -EPROBE_DEFER causes the device to be added to the
47  * pending list.  A successful driver probe will trigger moving all devices
48  * from the pending to the active list so that the workqueue will eventually
49  * retry them.
50  *
51  * The deferred_probe_mutex must be held any time the deferred_probe_*_list
52  * of the (struct device*)->p->deferred_probe pointers are manipulated
53  */
54 static DEFINE_MUTEX(deferred_probe_mutex);
55 static LIST_HEAD(deferred_probe_pending_list);
56 static LIST_HEAD(deferred_probe_active_list);
57 static atomic_t deferred_trigger_count = ATOMIC_INIT(0);
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 static void __device_set_deferred_probe_reason(const struct device *dev, char *reason)
72 {
73 	kfree(dev->p->deferred_probe_reason);
74 	dev->p->deferred_probe_reason = reason;
75 }
76 
77 /*
78  * deferred_probe_work_func() - Retry probing devices in the active list.
79  */
80 static void deferred_probe_work_func(struct work_struct *work)
81 {
82 	struct device *dev;
83 	struct device_private *private;
84 	/*
85 	 * This block processes every device in the deferred 'active' list.
86 	 * Each device is removed from the active list and passed to
87 	 * bus_probe_device() to re-attempt the probe.  The loop continues
88 	 * until every device in the active list is removed and retried.
89 	 *
90 	 * Note: Once the device is removed from the list and the mutex is
91 	 * released, it is possible for the device get freed by another thread
92 	 * and cause a illegal pointer dereference.  This code uses
93 	 * get/put_device() to ensure the device structure cannot disappear
94 	 * from under our feet.
95 	 */
96 	mutex_lock(&deferred_probe_mutex);
97 	while (!list_empty(&deferred_probe_active_list)) {
98 		private = list_first_entry(&deferred_probe_active_list,
99 					typeof(*dev->p), deferred_probe);
100 		dev = private->device;
101 		list_del_init(&private->deferred_probe);
102 
103 		get_device(dev);
104 
105 		__device_set_deferred_probe_reason(dev, NULL);
106 
107 		/*
108 		 * Drop the mutex while probing each device; the probe path may
109 		 * manipulate the deferred list
110 		 */
111 		mutex_unlock(&deferred_probe_mutex);
112 
113 		/*
114 		 * Force the device to the end of the dpm_list since
115 		 * the PM code assumes that the order we add things to
116 		 * the list is a good order for suspend but deferred
117 		 * probe makes that very unsafe.
118 		 */
119 		device_pm_move_to_tail(dev);
120 
121 		dev_dbg(dev, "Retrying from deferred list\n");
122 		bus_probe_device(dev);
123 		mutex_lock(&deferred_probe_mutex);
124 
125 		put_device(dev);
126 	}
127 	mutex_unlock(&deferred_probe_mutex);
128 }
129 static DECLARE_WORK(deferred_probe_work, deferred_probe_work_func);
130 
131 void driver_deferred_probe_add(struct device *dev)
132 {
133 	if (!dev->can_match)
134 		return;
135 
136 	mutex_lock(&deferred_probe_mutex);
137 	if (list_empty(&dev->p->deferred_probe)) {
138 		dev_dbg(dev, "Added to deferred list\n");
139 		list_add_tail(&dev->p->deferred_probe, &deferred_probe_pending_list);
140 	}
141 	mutex_unlock(&deferred_probe_mutex);
142 }
143 
144 void driver_deferred_probe_del(struct device *dev)
145 {
146 	mutex_lock(&deferred_probe_mutex);
147 	if (!list_empty(&dev->p->deferred_probe)) {
148 		dev_dbg(dev, "Removed from deferred list\n");
149 		list_del_init(&dev->p->deferred_probe);
150 		__device_set_deferred_probe_reason(dev, NULL);
151 	}
152 	mutex_unlock(&deferred_probe_mutex);
153 }
154 
155 static bool driver_deferred_probe_enable;
156 /**
157  * driver_deferred_probe_trigger() - Kick off re-probing deferred devices
158  *
159  * This functions moves all devices from the pending list to the active
160  * list and schedules the deferred probe workqueue to process them.  It
161  * should be called anytime a driver is successfully bound to a device.
162  *
163  * Note, there is a race condition in multi-threaded probe. In the case where
164  * more than one device is probing at the same time, it is possible for one
165  * probe to complete successfully while another is about to defer. If the second
166  * depends on the first, then it will get put on the pending list after the
167  * trigger event has already occurred and will be stuck there.
168  *
169  * The atomic 'deferred_trigger_count' is used to determine if a successful
170  * trigger has occurred in the midst of probing a driver. If the trigger count
171  * changes in the midst of a probe, then deferred processing should be triggered
172  * again.
173  */
174 static void driver_deferred_probe_trigger(void)
175 {
176 	if (!driver_deferred_probe_enable)
177 		return;
178 
179 	/*
180 	 * A successful probe means that all the devices in the pending list
181 	 * should be triggered to be reprobed.  Move all the deferred devices
182 	 * into the active list so they can be retried by the workqueue
183 	 */
184 	mutex_lock(&deferred_probe_mutex);
185 	atomic_inc(&deferred_trigger_count);
186 	list_splice_tail_init(&deferred_probe_pending_list,
187 			      &deferred_probe_active_list);
188 	mutex_unlock(&deferred_probe_mutex);
189 
190 	/*
191 	 * Kick the re-probe thread.  It may already be scheduled, but it is
192 	 * safe to kick it again.
193 	 */
194 	queue_work(system_unbound_wq, &deferred_probe_work);
195 }
196 
197 /**
198  * device_block_probing() - Block/defer device's probes
199  *
200  *	It will disable probing of devices and defer their probes instead.
201  */
202 void device_block_probing(void)
203 {
204 	defer_all_probes = true;
205 	/* sync with probes to avoid races. */
206 	wait_for_device_probe();
207 }
208 
209 /**
210  * device_unblock_probing() - Unblock/enable device's probes
211  *
212  *	It will restore normal behavior and trigger re-probing of deferred
213  * devices.
214  */
215 void device_unblock_probing(void)
216 {
217 	defer_all_probes = false;
218 	driver_deferred_probe_trigger();
219 }
220 
221 /**
222  * device_set_deferred_probe_reason() - Set defer probe reason message for device
223  * @dev: the pointer to the struct device
224  * @vaf: the pointer to va_format structure with message
225  */
226 void device_set_deferred_probe_reason(const struct device *dev, struct va_format *vaf)
227 {
228 	const char *drv = dev_driver_string(dev);
229 	char *reason;
230 
231 	mutex_lock(&deferred_probe_mutex);
232 
233 	reason = kasprintf(GFP_KERNEL, "%s: %pV", drv, vaf);
234 	__device_set_deferred_probe_reason(dev, reason);
235 
236 	mutex_unlock(&deferred_probe_mutex);
237 }
238 
239 /*
240  * deferred_devs_show() - Show the devices in the deferred probe pending list.
241  */
242 static int deferred_devs_show(struct seq_file *s, void *data)
243 {
244 	struct device_private *curr;
245 
246 	mutex_lock(&deferred_probe_mutex);
247 
248 	list_for_each_entry(curr, &deferred_probe_pending_list, deferred_probe)
249 		seq_printf(s, "%s\t%s", dev_name(curr->device),
250 			   curr->device->p->deferred_probe_reason ?: "\n");
251 
252 	mutex_unlock(&deferred_probe_mutex);
253 
254 	return 0;
255 }
256 DEFINE_SHOW_ATTRIBUTE(deferred_devs);
257 
258 int driver_deferred_probe_timeout;
259 EXPORT_SYMBOL_GPL(driver_deferred_probe_timeout);
260 static DECLARE_WAIT_QUEUE_HEAD(probe_timeout_waitqueue);
261 
262 static int __init deferred_probe_timeout_setup(char *str)
263 {
264 	int timeout;
265 
266 	if (!kstrtoint(str, 10, &timeout))
267 		driver_deferred_probe_timeout = timeout;
268 	return 1;
269 }
270 __setup("deferred_probe_timeout=", deferred_probe_timeout_setup);
271 
272 /**
273  * driver_deferred_probe_check_state() - Check deferred probe state
274  * @dev: device to check
275  *
276  * Return:
277  * -ENODEV if initcalls have completed and modules are disabled.
278  * -ETIMEDOUT if the deferred probe timeout was set and has expired
279  *  and modules are enabled.
280  * -EPROBE_DEFER in other cases.
281  *
282  * Drivers or subsystems can opt-in to calling this function instead of directly
283  * returning -EPROBE_DEFER.
284  */
285 int driver_deferred_probe_check_state(struct device *dev)
286 {
287 	if (!IS_ENABLED(CONFIG_MODULES) && initcalls_done) {
288 		dev_warn(dev, "ignoring dependency for device, assuming no driver\n");
289 		return -ENODEV;
290 	}
291 
292 	if (!driver_deferred_probe_timeout && initcalls_done) {
293 		dev_warn(dev, "deferred probe timeout, ignoring dependency\n");
294 		return -ETIMEDOUT;
295 	}
296 
297 	return -EPROBE_DEFER;
298 }
299 EXPORT_SYMBOL_GPL(driver_deferred_probe_check_state);
300 
301 static void deferred_probe_timeout_work_func(struct work_struct *work)
302 {
303 	struct device_private *p;
304 
305 	fw_devlink_drivers_done();
306 
307 	driver_deferred_probe_timeout = 0;
308 	driver_deferred_probe_trigger();
309 	flush_work(&deferred_probe_work);
310 
311 	mutex_lock(&deferred_probe_mutex);
312 	list_for_each_entry(p, &deferred_probe_pending_list, deferred_probe)
313 		dev_info(p->device, "deferred probe pending\n");
314 	mutex_unlock(&deferred_probe_mutex);
315 	wake_up_all(&probe_timeout_waitqueue);
316 }
317 static DECLARE_DELAYED_WORK(deferred_probe_timeout_work, deferred_probe_timeout_work_func);
318 
319 /**
320  * deferred_probe_initcall() - Enable probing of deferred devices
321  *
322  * We don't want to get in the way when the bulk of drivers are getting probed.
323  * Instead, this initcall makes sure that deferred probing is delayed until
324  * late_initcall time.
325  */
326 static int deferred_probe_initcall(void)
327 {
328 	debugfs_create_file("devices_deferred", 0444, NULL, NULL,
329 			    &deferred_devs_fops);
330 
331 	driver_deferred_probe_enable = true;
332 	driver_deferred_probe_trigger();
333 	/* Sort as many dependencies as possible before exiting initcalls */
334 	flush_work(&deferred_probe_work);
335 	initcalls_done = true;
336 
337 	if (!IS_ENABLED(CONFIG_MODULES))
338 		fw_devlink_drivers_done();
339 
340 	/*
341 	 * Trigger deferred probe again, this time we won't defer anything
342 	 * that is optional
343 	 */
344 	driver_deferred_probe_trigger();
345 	flush_work(&deferred_probe_work);
346 
347 	if (driver_deferred_probe_timeout > 0) {
348 		schedule_delayed_work(&deferred_probe_timeout_work,
349 			driver_deferred_probe_timeout * HZ);
350 	}
351 	return 0;
352 }
353 late_initcall(deferred_probe_initcall);
354 
355 static void __exit deferred_probe_exit(void)
356 {
357 	debugfs_remove_recursive(debugfs_lookup("devices_deferred", NULL));
358 }
359 __exitcall(deferred_probe_exit);
360 
361 /**
362  * device_is_bound() - Check if device is bound to a driver
363  * @dev: device to check
364  *
365  * Returns true if passed device has already finished probing successfully
366  * against a driver.
367  *
368  * This function must be called with the device lock held.
369  */
370 bool device_is_bound(struct device *dev)
371 {
372 	return dev->p && klist_node_attached(&dev->p->knode_driver);
373 }
374 
375 static void driver_bound(struct device *dev)
376 {
377 	if (device_is_bound(dev)) {
378 		pr_warn("%s: device %s already bound\n",
379 			__func__, kobject_name(&dev->kobj));
380 		return;
381 	}
382 
383 	pr_debug("driver: '%s': %s: bound to device '%s'\n", dev->driver->name,
384 		 __func__, dev_name(dev));
385 
386 	klist_add_tail(&dev->p->knode_driver, &dev->driver->p->klist_devices);
387 	device_links_driver_bound(dev);
388 
389 	device_pm_check_callbacks(dev);
390 
391 	/*
392 	 * Make sure the device is no longer in one of the deferred lists and
393 	 * kick off retrying all pending devices
394 	 */
395 	driver_deferred_probe_del(dev);
396 	driver_deferred_probe_trigger();
397 
398 	if (dev->bus)
399 		blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
400 					     BUS_NOTIFY_BOUND_DRIVER, dev);
401 
402 	kobject_uevent(&dev->kobj, KOBJ_BIND);
403 }
404 
405 static ssize_t coredump_store(struct device *dev, struct device_attribute *attr,
406 			    const char *buf, size_t count)
407 {
408 	device_lock(dev);
409 	dev->driver->coredump(dev);
410 	device_unlock(dev);
411 
412 	return count;
413 }
414 static DEVICE_ATTR_WO(coredump);
415 
416 static int driver_sysfs_add(struct device *dev)
417 {
418 	int ret;
419 
420 	if (dev->bus)
421 		blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
422 					     BUS_NOTIFY_BIND_DRIVER, dev);
423 
424 	ret = sysfs_create_link(&dev->driver->p->kobj, &dev->kobj,
425 				kobject_name(&dev->kobj));
426 	if (ret)
427 		goto fail;
428 
429 	ret = sysfs_create_link(&dev->kobj, &dev->driver->p->kobj,
430 				"driver");
431 	if (ret)
432 		goto rm_dev;
433 
434 	if (!IS_ENABLED(CONFIG_DEV_COREDUMP) || !dev->driver->coredump)
435 		return 0;
436 
437 	ret = device_create_file(dev, &dev_attr_coredump);
438 	if (!ret)
439 		return 0;
440 
441 	sysfs_remove_link(&dev->kobj, "driver");
442 
443 rm_dev:
444 	sysfs_remove_link(&dev->driver->p->kobj,
445 			  kobject_name(&dev->kobj));
446 
447 fail:
448 	return ret;
449 }
450 
451 static void driver_sysfs_remove(struct device *dev)
452 {
453 	struct device_driver *drv = dev->driver;
454 
455 	if (drv) {
456 		if (drv->coredump)
457 			device_remove_file(dev, &dev_attr_coredump);
458 		sysfs_remove_link(&drv->p->kobj, kobject_name(&dev->kobj));
459 		sysfs_remove_link(&dev->kobj, "driver");
460 	}
461 }
462 
463 /**
464  * device_bind_driver - bind a driver to one device.
465  * @dev: device.
466  *
467  * Allow manual attachment of a driver to a device.
468  * Caller must have already set @dev->driver.
469  *
470  * Note that this does not modify the bus reference count.
471  * Please verify that is accounted for before calling this.
472  * (It is ok to call with no other effort from a driver's probe() method.)
473  *
474  * This function must be called with the device lock held.
475  *
476  * Callers should prefer to use device_driver_attach() instead.
477  */
478 int device_bind_driver(struct device *dev)
479 {
480 	int ret;
481 
482 	ret = driver_sysfs_add(dev);
483 	if (!ret) {
484 		device_links_force_bind(dev);
485 		driver_bound(dev);
486 	}
487 	else if (dev->bus)
488 		blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
489 					     BUS_NOTIFY_DRIVER_NOT_BOUND, dev);
490 	return ret;
491 }
492 EXPORT_SYMBOL_GPL(device_bind_driver);
493 
494 static atomic_t probe_count = ATOMIC_INIT(0);
495 static DECLARE_WAIT_QUEUE_HEAD(probe_waitqueue);
496 
497 static ssize_t state_synced_show(struct device *dev,
498 				 struct device_attribute *attr, char *buf)
499 {
500 	bool val;
501 
502 	device_lock(dev);
503 	val = dev->state_synced;
504 	device_unlock(dev);
505 
506 	return sysfs_emit(buf, "%u\n", val);
507 }
508 static DEVICE_ATTR_RO(state_synced);
509 
510 static void device_unbind_cleanup(struct device *dev)
511 {
512 	devres_release_all(dev);
513 	arch_teardown_dma_ops(dev);
514 	kfree(dev->dma_range_map);
515 	dev->dma_range_map = NULL;
516 	dev->driver = NULL;
517 	dev_set_drvdata(dev, NULL);
518 	if (dev->pm_domain && dev->pm_domain->dismiss)
519 		dev->pm_domain->dismiss(dev);
520 	pm_runtime_reinit(dev);
521 	dev_pm_set_driver_flags(dev, 0);
522 }
523 
524 static void device_remove(struct device *dev)
525 {
526 	device_remove_file(dev, &dev_attr_state_synced);
527 	device_remove_groups(dev, dev->driver->dev_groups);
528 
529 	if (dev->bus && dev->bus->remove)
530 		dev->bus->remove(dev);
531 	else if (dev->driver->remove)
532 		dev->driver->remove(dev);
533 }
534 
535 static int call_driver_probe(struct device *dev, struct device_driver *drv)
536 {
537 	int ret = 0;
538 
539 	if (dev->bus->probe)
540 		ret = dev->bus->probe(dev);
541 	else if (drv->probe)
542 		ret = drv->probe(dev);
543 
544 	switch (ret) {
545 	case 0:
546 		break;
547 	case -EPROBE_DEFER:
548 		/* Driver requested deferred probing */
549 		dev_dbg(dev, "Driver %s requests probe deferral\n", drv->name);
550 		break;
551 	case -ENODEV:
552 	case -ENXIO:
553 		pr_debug("%s: probe of %s rejects match %d\n",
554 			 drv->name, dev_name(dev), ret);
555 		break;
556 	default:
557 		/* driver matched but the probe failed */
558 		pr_warn("%s: probe of %s failed with error %d\n",
559 			drv->name, dev_name(dev), ret);
560 		break;
561 	}
562 
563 	return ret;
564 }
565 
566 static int really_probe(struct device *dev, struct device_driver *drv)
567 {
568 	bool test_remove = IS_ENABLED(CONFIG_DEBUG_TEST_DRIVER_REMOVE) &&
569 			   !drv->suppress_bind_attrs;
570 	int ret;
571 
572 	if (defer_all_probes) {
573 		/*
574 		 * Value of defer_all_probes can be set only by
575 		 * device_block_probing() which, in turn, will call
576 		 * wait_for_device_probe() right after that to avoid any races.
577 		 */
578 		dev_dbg(dev, "Driver %s force probe deferral\n", drv->name);
579 		return -EPROBE_DEFER;
580 	}
581 
582 	ret = device_links_check_suppliers(dev);
583 	if (ret)
584 		return ret;
585 
586 	pr_debug("bus: '%s': %s: probing driver %s with device %s\n",
587 		 drv->bus->name, __func__, drv->name, dev_name(dev));
588 	if (!list_empty(&dev->devres_head)) {
589 		dev_crit(dev, "Resources present before probing\n");
590 		ret = -EBUSY;
591 		goto done;
592 	}
593 
594 re_probe:
595 	dev->driver = drv;
596 
597 	/* If using pinctrl, bind pins now before probing */
598 	ret = pinctrl_bind_pins(dev);
599 	if (ret)
600 		goto pinctrl_bind_failed;
601 
602 	if (dev->bus->dma_configure) {
603 		ret = dev->bus->dma_configure(dev);
604 		if (ret)
605 			goto pinctrl_bind_failed;
606 	}
607 
608 	ret = driver_sysfs_add(dev);
609 	if (ret) {
610 		pr_err("%s: driver_sysfs_add(%s) failed\n",
611 		       __func__, dev_name(dev));
612 		goto sysfs_failed;
613 	}
614 
615 	if (dev->pm_domain && dev->pm_domain->activate) {
616 		ret = dev->pm_domain->activate(dev);
617 		if (ret)
618 			goto probe_failed;
619 	}
620 
621 	ret = call_driver_probe(dev, drv);
622 	if (ret) {
623 		/*
624 		 * Return probe errors as positive values so that the callers
625 		 * can distinguish them from other errors.
626 		 */
627 		ret = -ret;
628 		goto probe_failed;
629 	}
630 
631 	ret = device_add_groups(dev, drv->dev_groups);
632 	if (ret) {
633 		dev_err(dev, "device_add_groups() failed\n");
634 		goto dev_groups_failed;
635 	}
636 
637 	if (dev_has_sync_state(dev)) {
638 		ret = device_create_file(dev, &dev_attr_state_synced);
639 		if (ret) {
640 			dev_err(dev, "state_synced sysfs add failed\n");
641 			goto dev_sysfs_state_synced_failed;
642 		}
643 	}
644 
645 	if (test_remove) {
646 		test_remove = false;
647 
648 		device_remove(dev);
649 		driver_sysfs_remove(dev);
650 		device_unbind_cleanup(dev);
651 
652 		goto re_probe;
653 	}
654 
655 	pinctrl_init_done(dev);
656 
657 	if (dev->pm_domain && dev->pm_domain->sync)
658 		dev->pm_domain->sync(dev);
659 
660 	driver_bound(dev);
661 	pr_debug("bus: '%s': %s: bound device %s to driver %s\n",
662 		 drv->bus->name, __func__, dev_name(dev), drv->name);
663 	goto done;
664 
665 dev_sysfs_state_synced_failed:
666 dev_groups_failed:
667 	device_remove(dev);
668 probe_failed:
669 	driver_sysfs_remove(dev);
670 sysfs_failed:
671 	if (dev->bus)
672 		blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
673 					     BUS_NOTIFY_DRIVER_NOT_BOUND, dev);
674 	if (dev->bus && dev->bus->dma_cleanup)
675 		dev->bus->dma_cleanup(dev);
676 pinctrl_bind_failed:
677 	device_links_no_driver(dev);
678 	device_unbind_cleanup(dev);
679 done:
680 	return ret;
681 }
682 
683 /*
684  * For initcall_debug, show the driver probe time.
685  */
686 static int really_probe_debug(struct device *dev, struct device_driver *drv)
687 {
688 	ktime_t calltime, rettime;
689 	int ret;
690 
691 	calltime = ktime_get();
692 	ret = really_probe(dev, drv);
693 	rettime = ktime_get();
694 	pr_debug("probe of %s returned %d after %lld usecs\n",
695 		 dev_name(dev), ret, ktime_us_delta(rettime, calltime));
696 	return ret;
697 }
698 
699 /**
700  * driver_probe_done
701  * Determine if the probe sequence is finished or not.
702  *
703  * Should somehow figure out how to use a semaphore, not an atomic variable...
704  */
705 int driver_probe_done(void)
706 {
707 	int local_probe_count = atomic_read(&probe_count);
708 
709 	pr_debug("%s: probe_count = %d\n", __func__, local_probe_count);
710 	if (local_probe_count)
711 		return -EBUSY;
712 	return 0;
713 }
714 
715 /**
716  * wait_for_device_probe
717  * Wait for device probing to be completed.
718  */
719 void wait_for_device_probe(void)
720 {
721 	/* wait for probe timeout */
722 	wait_event(probe_timeout_waitqueue, !driver_deferred_probe_timeout);
723 
724 	/* wait for the deferred probe workqueue to finish */
725 	flush_work(&deferred_probe_work);
726 
727 	/* wait for the known devices to complete their probing */
728 	wait_event(probe_waitqueue, atomic_read(&probe_count) == 0);
729 	async_synchronize_full();
730 }
731 EXPORT_SYMBOL_GPL(wait_for_device_probe);
732 
733 static int __driver_probe_device(struct device_driver *drv, struct device *dev)
734 {
735 	int ret = 0;
736 
737 	if (dev->p->dead || !device_is_registered(dev))
738 		return -ENODEV;
739 	if (dev->driver)
740 		return -EBUSY;
741 
742 	dev->can_match = true;
743 	pr_debug("bus: '%s': %s: matched device %s with driver %s\n",
744 		 drv->bus->name, __func__, dev_name(dev), drv->name);
745 
746 	pm_runtime_get_suppliers(dev);
747 	if (dev->parent)
748 		pm_runtime_get_sync(dev->parent);
749 
750 	pm_runtime_barrier(dev);
751 	if (initcall_debug)
752 		ret = really_probe_debug(dev, drv);
753 	else
754 		ret = really_probe(dev, drv);
755 	pm_request_idle(dev);
756 
757 	if (dev->parent)
758 		pm_runtime_put(dev->parent);
759 
760 	pm_runtime_put_suppliers(dev);
761 	return ret;
762 }
763 
764 /**
765  * driver_probe_device - attempt to bind device & driver together
766  * @drv: driver to bind a device to
767  * @dev: device to try to bind to the driver
768  *
769  * This function returns -ENODEV if the device is not registered, -EBUSY if it
770  * already has a driver, 0 if the device is bound successfully and a positive
771  * (inverted) error code for failures from the ->probe method.
772  *
773  * This function must be called with @dev lock held.  When called for a
774  * USB interface, @dev->parent lock must be held as well.
775  *
776  * If the device has a parent, runtime-resume the parent before driver probing.
777  */
778 static int driver_probe_device(struct device_driver *drv, struct device *dev)
779 {
780 	int trigger_count = atomic_read(&deferred_trigger_count);
781 	int ret;
782 
783 	atomic_inc(&probe_count);
784 	ret = __driver_probe_device(drv, dev);
785 	if (ret == -EPROBE_DEFER || ret == EPROBE_DEFER) {
786 		driver_deferred_probe_add(dev);
787 
788 		/*
789 		 * Did a trigger occur while probing? Need to re-trigger if yes
790 		 */
791 		if (trigger_count != atomic_read(&deferred_trigger_count) &&
792 		    !defer_all_probes)
793 			driver_deferred_probe_trigger();
794 	}
795 	atomic_dec(&probe_count);
796 	wake_up_all(&probe_waitqueue);
797 	return ret;
798 }
799 
800 static inline bool cmdline_requested_async_probing(const char *drv_name)
801 {
802 	return parse_option_str(async_probe_drv_names, drv_name);
803 }
804 
805 /* The option format is "driver_async_probe=drv_name1,drv_name2,..." */
806 static int __init save_async_options(char *buf)
807 {
808 	if (strlen(buf) >= ASYNC_DRV_NAMES_MAX_LEN)
809 		pr_warn("Too long list of driver names for 'driver_async_probe'!\n");
810 
811 	strlcpy(async_probe_drv_names, buf, ASYNC_DRV_NAMES_MAX_LEN);
812 	return 1;
813 }
814 __setup("driver_async_probe=", save_async_options);
815 
816 bool driver_allows_async_probing(struct device_driver *drv)
817 {
818 	switch (drv->probe_type) {
819 	case PROBE_PREFER_ASYNCHRONOUS:
820 		return true;
821 
822 	case PROBE_FORCE_SYNCHRONOUS:
823 		return false;
824 
825 	default:
826 		if (cmdline_requested_async_probing(drv->name))
827 			return true;
828 
829 		if (module_requested_async_probing(drv->owner))
830 			return true;
831 
832 		return false;
833 	}
834 }
835 
836 struct device_attach_data {
837 	struct device *dev;
838 
839 	/*
840 	 * Indicates whether we are considering asynchronous probing or
841 	 * not. Only initial binding after device or driver registration
842 	 * (including deferral processing) may be done asynchronously, the
843 	 * rest is always synchronous, as we expect it is being done by
844 	 * request from userspace.
845 	 */
846 	bool check_async;
847 
848 	/*
849 	 * Indicates if we are binding synchronous or asynchronous drivers.
850 	 * When asynchronous probing is enabled we'll execute 2 passes
851 	 * over drivers: first pass doing synchronous probing and second
852 	 * doing asynchronous probing (if synchronous did not succeed -
853 	 * most likely because there was no driver requiring synchronous
854 	 * probing - and we found asynchronous driver during first pass).
855 	 * The 2 passes are done because we can't shoot asynchronous
856 	 * probe for given device and driver from bus_for_each_drv() since
857 	 * driver pointer is not guaranteed to stay valid once
858 	 * bus_for_each_drv() iterates to the next driver on the bus.
859 	 */
860 	bool want_async;
861 
862 	/*
863 	 * We'll set have_async to 'true' if, while scanning for matching
864 	 * driver, we'll encounter one that requests asynchronous probing.
865 	 */
866 	bool have_async;
867 };
868 
869 static int __device_attach_driver(struct device_driver *drv, void *_data)
870 {
871 	struct device_attach_data *data = _data;
872 	struct device *dev = data->dev;
873 	bool async_allowed;
874 	int ret;
875 
876 	ret = driver_match_device(drv, dev);
877 	if (ret == 0) {
878 		/* no match */
879 		return 0;
880 	} else if (ret == -EPROBE_DEFER) {
881 		dev_dbg(dev, "Device match requests probe deferral\n");
882 		dev->can_match = true;
883 		driver_deferred_probe_add(dev);
884 	} else if (ret < 0) {
885 		dev_dbg(dev, "Bus failed to match device: %d\n", ret);
886 		return ret;
887 	} /* ret > 0 means positive match */
888 
889 	async_allowed = driver_allows_async_probing(drv);
890 
891 	if (async_allowed)
892 		data->have_async = true;
893 
894 	if (data->check_async && async_allowed != data->want_async)
895 		return 0;
896 
897 	/*
898 	 * Ignore errors returned by ->probe so that the next driver can try
899 	 * its luck.
900 	 */
901 	ret = driver_probe_device(drv, dev);
902 	if (ret < 0)
903 		return ret;
904 	return ret == 0;
905 }
906 
907 static void __device_attach_async_helper(void *_dev, async_cookie_t cookie)
908 {
909 	struct device *dev = _dev;
910 	struct device_attach_data data = {
911 		.dev		= dev,
912 		.check_async	= true,
913 		.want_async	= true,
914 	};
915 
916 	device_lock(dev);
917 
918 	/*
919 	 * Check if device has already been removed or claimed. This may
920 	 * happen with driver loading, device discovery/registration,
921 	 * and deferred probe processing happens all at once with
922 	 * multiple threads.
923 	 */
924 	if (dev->p->dead || dev->driver)
925 		goto out_unlock;
926 
927 	if (dev->parent)
928 		pm_runtime_get_sync(dev->parent);
929 
930 	bus_for_each_drv(dev->bus, NULL, &data, __device_attach_driver);
931 	dev_dbg(dev, "async probe completed\n");
932 
933 	pm_request_idle(dev);
934 
935 	if (dev->parent)
936 		pm_runtime_put(dev->parent);
937 out_unlock:
938 	device_unlock(dev);
939 
940 	put_device(dev);
941 }
942 
943 static int __device_attach(struct device *dev, bool allow_async)
944 {
945 	int ret = 0;
946 
947 	device_lock(dev);
948 	if (dev->p->dead) {
949 		goto out_unlock;
950 	} else if (dev->driver) {
951 		if (device_is_bound(dev)) {
952 			ret = 1;
953 			goto out_unlock;
954 		}
955 		ret = device_bind_driver(dev);
956 		if (ret == 0)
957 			ret = 1;
958 		else {
959 			dev->driver = NULL;
960 			ret = 0;
961 		}
962 	} else {
963 		struct device_attach_data data = {
964 			.dev = dev,
965 			.check_async = allow_async,
966 			.want_async = false,
967 		};
968 
969 		if (dev->parent)
970 			pm_runtime_get_sync(dev->parent);
971 
972 		ret = bus_for_each_drv(dev->bus, NULL, &data,
973 					__device_attach_driver);
974 		if (!ret && allow_async && data.have_async) {
975 			/*
976 			 * If we could not find appropriate driver
977 			 * synchronously and we are allowed to do
978 			 * async probes and there are drivers that
979 			 * want to probe asynchronously, we'll
980 			 * try them.
981 			 */
982 			dev_dbg(dev, "scheduling asynchronous probe\n");
983 			get_device(dev);
984 			async_schedule_dev(__device_attach_async_helper, dev);
985 		} else {
986 			pm_request_idle(dev);
987 		}
988 
989 		if (dev->parent)
990 			pm_runtime_put(dev->parent);
991 	}
992 out_unlock:
993 	device_unlock(dev);
994 	return ret;
995 }
996 
997 /**
998  * device_attach - try to attach device to a driver.
999  * @dev: device.
1000  *
1001  * Walk the list of drivers that the bus has and call
1002  * driver_probe_device() for each pair. If a compatible
1003  * pair is found, break out and return.
1004  *
1005  * Returns 1 if the device was bound to a driver;
1006  * 0 if no matching driver was found;
1007  * -ENODEV if the device is not registered.
1008  *
1009  * When called for a USB interface, @dev->parent lock must be held.
1010  */
1011 int device_attach(struct device *dev)
1012 {
1013 	return __device_attach(dev, false);
1014 }
1015 EXPORT_SYMBOL_GPL(device_attach);
1016 
1017 void device_initial_probe(struct device *dev)
1018 {
1019 	__device_attach(dev, true);
1020 }
1021 
1022 /*
1023  * __device_driver_lock - acquire locks needed to manipulate dev->drv
1024  * @dev: Device we will update driver info for
1025  * @parent: Parent device. Needed if the bus requires parent lock
1026  *
1027  * This function will take the required locks for manipulating dev->drv.
1028  * Normally this will just be the @dev lock, but when called for a USB
1029  * interface, @parent lock will be held as well.
1030  */
1031 static void __device_driver_lock(struct device *dev, struct device *parent)
1032 {
1033 	if (parent && dev->bus->need_parent_lock)
1034 		device_lock(parent);
1035 	device_lock(dev);
1036 }
1037 
1038 /*
1039  * __device_driver_unlock - release locks needed to manipulate dev->drv
1040  * @dev: Device we will update driver info for
1041  * @parent: Parent device. Needed if the bus requires parent lock
1042  *
1043  * This function will release the required locks for manipulating dev->drv.
1044  * Normally this will just be the @dev lock, but when called for a
1045  * USB interface, @parent lock will be released as well.
1046  */
1047 static void __device_driver_unlock(struct device *dev, struct device *parent)
1048 {
1049 	device_unlock(dev);
1050 	if (parent && dev->bus->need_parent_lock)
1051 		device_unlock(parent);
1052 }
1053 
1054 /**
1055  * device_driver_attach - attach a specific driver to a specific device
1056  * @drv: Driver to attach
1057  * @dev: Device to attach it to
1058  *
1059  * Manually attach driver to a device. Will acquire both @dev lock and
1060  * @dev->parent lock if needed. Returns 0 on success, -ERR on failure.
1061  */
1062 int device_driver_attach(struct device_driver *drv, struct device *dev)
1063 {
1064 	int ret;
1065 
1066 	__device_driver_lock(dev, dev->parent);
1067 	ret = __driver_probe_device(drv, dev);
1068 	__device_driver_unlock(dev, dev->parent);
1069 
1070 	/* also return probe errors as normal negative errnos */
1071 	if (ret > 0)
1072 		ret = -ret;
1073 	if (ret == -EPROBE_DEFER)
1074 		return -EAGAIN;
1075 	return ret;
1076 }
1077 EXPORT_SYMBOL_GPL(device_driver_attach);
1078 
1079 static void __driver_attach_async_helper(void *_dev, async_cookie_t cookie)
1080 {
1081 	struct device *dev = _dev;
1082 	struct device_driver *drv;
1083 	int ret;
1084 
1085 	__device_driver_lock(dev, dev->parent);
1086 	drv = dev->p->async_driver;
1087 	ret = driver_probe_device(drv, dev);
1088 	__device_driver_unlock(dev, dev->parent);
1089 
1090 	dev_dbg(dev, "driver %s async attach completed: %d\n", drv->name, ret);
1091 
1092 	put_device(dev);
1093 }
1094 
1095 static int __driver_attach(struct device *dev, void *data)
1096 {
1097 	struct device_driver *drv = data;
1098 	int ret;
1099 
1100 	/*
1101 	 * Lock device and try to bind to it. We drop the error
1102 	 * here and always return 0, because we need to keep trying
1103 	 * to bind to devices and some drivers will return an error
1104 	 * simply if it didn't support the device.
1105 	 *
1106 	 * driver_probe_device() will spit a warning if there
1107 	 * is an error.
1108 	 */
1109 
1110 	ret = driver_match_device(drv, dev);
1111 	if (ret == 0) {
1112 		/* no match */
1113 		return 0;
1114 	} else if (ret == -EPROBE_DEFER) {
1115 		dev_dbg(dev, "Device match requests probe deferral\n");
1116 		dev->can_match = true;
1117 		driver_deferred_probe_add(dev);
1118 	} else if (ret < 0) {
1119 		dev_dbg(dev, "Bus failed to match device: %d\n", ret);
1120 		return ret;
1121 	} /* ret > 0 means positive match */
1122 
1123 	if (driver_allows_async_probing(drv)) {
1124 		/*
1125 		 * Instead of probing the device synchronously we will
1126 		 * probe it asynchronously to allow for more parallelism.
1127 		 *
1128 		 * We only take the device lock here in order to guarantee
1129 		 * that the dev->driver and async_driver fields are protected
1130 		 */
1131 		dev_dbg(dev, "probing driver %s asynchronously\n", drv->name);
1132 		device_lock(dev);
1133 		if (!dev->driver) {
1134 			get_device(dev);
1135 			dev->p->async_driver = drv;
1136 			async_schedule_dev(__driver_attach_async_helper, dev);
1137 		}
1138 		device_unlock(dev);
1139 		return 0;
1140 	}
1141 
1142 	__device_driver_lock(dev, dev->parent);
1143 	driver_probe_device(drv, dev);
1144 	__device_driver_unlock(dev, dev->parent);
1145 
1146 	return 0;
1147 }
1148 
1149 /**
1150  * driver_attach - try to bind driver to devices.
1151  * @drv: driver.
1152  *
1153  * Walk the list of devices that the bus has on it and try to
1154  * match the driver with each one.  If driver_probe_device()
1155  * returns 0 and the @dev->driver is set, we've found a
1156  * compatible pair.
1157  */
1158 int driver_attach(struct device_driver *drv)
1159 {
1160 	return bus_for_each_dev(drv->bus, NULL, drv, __driver_attach);
1161 }
1162 EXPORT_SYMBOL_GPL(driver_attach);
1163 
1164 /*
1165  * __device_release_driver() must be called with @dev lock held.
1166  * When called for a USB interface, @dev->parent lock must be held as well.
1167  */
1168 static void __device_release_driver(struct device *dev, struct device *parent)
1169 {
1170 	struct device_driver *drv;
1171 
1172 	drv = dev->driver;
1173 	if (drv) {
1174 		pm_runtime_get_sync(dev);
1175 
1176 		while (device_links_busy(dev)) {
1177 			__device_driver_unlock(dev, parent);
1178 
1179 			device_links_unbind_consumers(dev);
1180 
1181 			__device_driver_lock(dev, parent);
1182 			/*
1183 			 * A concurrent invocation of the same function might
1184 			 * have released the driver successfully while this one
1185 			 * was waiting, so check for that.
1186 			 */
1187 			if (dev->driver != drv) {
1188 				pm_runtime_put(dev);
1189 				return;
1190 			}
1191 		}
1192 
1193 		driver_sysfs_remove(dev);
1194 
1195 		if (dev->bus)
1196 			blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
1197 						     BUS_NOTIFY_UNBIND_DRIVER,
1198 						     dev);
1199 
1200 		pm_runtime_put_sync(dev);
1201 
1202 		device_remove(dev);
1203 
1204 		if (dev->bus && dev->bus->dma_cleanup)
1205 			dev->bus->dma_cleanup(dev);
1206 
1207 		device_links_driver_cleanup(dev);
1208 		device_unbind_cleanup(dev);
1209 
1210 		klist_remove(&dev->p->knode_driver);
1211 		device_pm_check_callbacks(dev);
1212 		if (dev->bus)
1213 			blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
1214 						     BUS_NOTIFY_UNBOUND_DRIVER,
1215 						     dev);
1216 
1217 		kobject_uevent(&dev->kobj, KOBJ_UNBIND);
1218 	}
1219 }
1220 
1221 void device_release_driver_internal(struct device *dev,
1222 				    struct device_driver *drv,
1223 				    struct device *parent)
1224 {
1225 	__device_driver_lock(dev, parent);
1226 
1227 	if (!drv || drv == dev->driver)
1228 		__device_release_driver(dev, parent);
1229 
1230 	__device_driver_unlock(dev, parent);
1231 }
1232 
1233 /**
1234  * device_release_driver - manually detach device from driver.
1235  * @dev: device.
1236  *
1237  * Manually detach device from driver.
1238  * When called for a USB interface, @dev->parent lock must be held.
1239  *
1240  * If this function is to be called with @dev->parent lock held, ensure that
1241  * the device's consumers are unbound in advance or that their locks can be
1242  * acquired under the @dev->parent lock.
1243  */
1244 void device_release_driver(struct device *dev)
1245 {
1246 	/*
1247 	 * If anyone calls device_release_driver() recursively from
1248 	 * within their ->remove callback for the same device, they
1249 	 * will deadlock right here.
1250 	 */
1251 	device_release_driver_internal(dev, NULL, NULL);
1252 }
1253 EXPORT_SYMBOL_GPL(device_release_driver);
1254 
1255 /**
1256  * device_driver_detach - detach driver from a specific device
1257  * @dev: device to detach driver from
1258  *
1259  * Detach driver from device. Will acquire both @dev lock and @dev->parent
1260  * lock if needed.
1261  */
1262 void device_driver_detach(struct device *dev)
1263 {
1264 	device_release_driver_internal(dev, NULL, dev->parent);
1265 }
1266 
1267 /**
1268  * driver_detach - detach driver from all devices it controls.
1269  * @drv: driver.
1270  */
1271 void driver_detach(struct device_driver *drv)
1272 {
1273 	struct device_private *dev_prv;
1274 	struct device *dev;
1275 
1276 	if (driver_allows_async_probing(drv))
1277 		async_synchronize_full();
1278 
1279 	for (;;) {
1280 		spin_lock(&drv->p->klist_devices.k_lock);
1281 		if (list_empty(&drv->p->klist_devices.k_list)) {
1282 			spin_unlock(&drv->p->klist_devices.k_lock);
1283 			break;
1284 		}
1285 		dev_prv = list_last_entry(&drv->p->klist_devices.k_list,
1286 				     struct device_private,
1287 				     knode_driver.n_node);
1288 		dev = dev_prv->device;
1289 		get_device(dev);
1290 		spin_unlock(&drv->p->klist_devices.k_lock);
1291 		device_release_driver_internal(dev, drv, dev->parent);
1292 		put_device(dev);
1293 	}
1294 }
1295