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/device.h>
 20#include <linux/delay.h>
 21#include <linux/dma-mapping.h>
 22#include <linux/init.h>
 23#include <linux/module.h>
 24#include <linux/kthread.h>
 25#include <linux/wait.h>
 26#include <linux/async.h>
 27#include <linux/pm_runtime.h>
 28#include <linux/pinctrl/devinfo.h>
 29
 30#include "base.h"
 31#include "power/power.h"
 32
 33/*
 34 * Deferred Probe infrastructure.
 35 *
 36 * Sometimes driver probe order matters, but the kernel doesn't always have
 37 * dependency information which means some drivers will get probed before a
 38 * resource it depends on is available.  For example, an SDHCI driver may
 39 * first need a GPIO line from an i2c GPIO controller before it can be
 40 * initialized.  If a required resource is not available yet, a driver can
 41 * request probing to be deferred by returning -EPROBE_DEFER from its probe hook
 42 *
 43 * Deferred probe maintains two lists of devices, a pending list and an active
 44 * list.  A driver returning -EPROBE_DEFER causes the device to be added to the
 45 * pending list.  A successful driver probe will trigger moving all devices
 46 * from the pending to the active list so that the workqueue will eventually
 47 * retry them.
 48 *
 49 * The deferred_probe_mutex must be held any time the deferred_probe_*_list
 50 * of the (struct device*)->p->deferred_probe pointers are manipulated
 51 */
 52static DEFINE_MUTEX(deferred_probe_mutex);
 53static LIST_HEAD(deferred_probe_pending_list);
 54static LIST_HEAD(deferred_probe_active_list);
 55static atomic_t deferred_trigger_count = ATOMIC_INIT(0);
 56static bool initcalls_done;
 57
 58/*
 59 * In some cases, like suspend to RAM or hibernation, It might be reasonable
 60 * to prohibit probing of devices as it could be unsafe.
 61 * Once defer_all_probes is true all drivers probes will be forcibly deferred.
 62 */
 63static bool defer_all_probes;
 64
 65/*
 66 * For initcall_debug, show the deferred probes executed in late_initcall
 67 * processing.
 68 */
 69static void deferred_probe_debug(struct device *dev)
 70{
 71	ktime_t calltime, delta, rettime;
 72	unsigned long long duration;
 73
 74	printk(KERN_DEBUG "deferred probe %s @ %i\n", dev_name(dev),
 75	       task_pid_nr(current));
 76	calltime = ktime_get();
 77	bus_probe_device(dev);
 78	rettime = ktime_get();
 79	delta = ktime_sub(rettime, calltime);
 80	duration = (unsigned long long) ktime_to_ns(delta) >> 10;
 81	printk(KERN_DEBUG "deferred probe %s returned after %lld usecs\n",
 82	       dev_name(dev), duration);
 83}
 84
 85/*
 86 * deferred_probe_work_func() - Retry probing devices in the active list.
 87 */
 88static void deferred_probe_work_func(struct work_struct *work)
 89{
 90	struct device *dev;
 91	struct device_private *private;
 92	/*
 93	 * This block processes every device in the deferred 'active' list.
 94	 * Each device is removed from the active list and passed to
 95	 * bus_probe_device() to re-attempt the probe.  The loop continues
 96	 * until every device in the active list is removed and retried.
 97	 *
 98	 * Note: Once the device is removed from the list and the mutex is
 99	 * released, it is possible for the device get freed by another thread
100	 * and cause a illegal pointer dereference.  This code uses
101	 * get/put_device() to ensure the device structure cannot disappear
102	 * from under our feet.
103	 */
104	mutex_lock(&deferred_probe_mutex);
105	while (!list_empty(&deferred_probe_active_list)) {
106		private = list_first_entry(&deferred_probe_active_list,
107					typeof(*dev->p), deferred_probe);
108		dev = private->device;
109		list_del_init(&private->deferred_probe);
110
111		get_device(dev);
112
113		/*
114		 * Drop the mutex while probing each device; the probe path may
115		 * manipulate the deferred list
116		 */
117		mutex_unlock(&deferred_probe_mutex);
118
119		/*
120		 * Force the device to the end of the dpm_list since
121		 * the PM code assumes that the order we add things to
122		 * the list is a good order for suspend but deferred
123		 * probe makes that very unsafe.
124		 */
125		device_pm_lock();
126		device_pm_move_last(dev);
127		device_pm_unlock();
128
129		dev_dbg(dev, "Retrying from deferred list\n");
130		if (initcall_debug && !initcalls_done)
131			deferred_probe_debug(dev);
132		else
133			bus_probe_device(dev);
134
135		mutex_lock(&deferred_probe_mutex);
136
137		put_device(dev);
138	}
139	mutex_unlock(&deferred_probe_mutex);
140}
141static DECLARE_WORK(deferred_probe_work, deferred_probe_work_func);
142
143static void driver_deferred_probe_add(struct device *dev)
144{
145	mutex_lock(&deferred_probe_mutex);
146	if (list_empty(&dev->p->deferred_probe)) {
147		dev_dbg(dev, "Added to deferred list\n");
148		list_add_tail(&dev->p->deferred_probe, &deferred_probe_pending_list);
149	}
150	mutex_unlock(&deferred_probe_mutex);
151}
152
153void driver_deferred_probe_del(struct device *dev)
154{
155	mutex_lock(&deferred_probe_mutex);
156	if (!list_empty(&dev->p->deferred_probe)) {
157		dev_dbg(dev, "Removed from deferred list\n");
158		list_del_init(&dev->p->deferred_probe);
159	}
160	mutex_unlock(&deferred_probe_mutex);
161}
162
163static bool driver_deferred_probe_enable = false;
164/**
165 * driver_deferred_probe_trigger() - Kick off re-probing deferred devices
166 *
167 * This functions moves all devices from the pending list to the active
168 * list and schedules the deferred probe workqueue to process them.  It
169 * should be called anytime a driver is successfully bound to a device.
170 *
171 * Note, there is a race condition in multi-threaded probe. In the case where
172 * more than one device is probing at the same time, it is possible for one
173 * probe to complete successfully while another is about to defer. If the second
174 * depends on the first, then it will get put on the pending list after the
175 * trigger event has already occurred and will be stuck there.
176 *
177 * The atomic 'deferred_trigger_count' is used to determine if a successful
178 * trigger has occurred in the midst of probing a driver. If the trigger count
179 * changes in the midst of a probe, then deferred processing should be triggered
180 * again.
181 */
182static void driver_deferred_probe_trigger(void)
183{
184	if (!driver_deferred_probe_enable)
185		return;
186
187	/*
188	 * A successful probe means that all the devices in the pending list
189	 * should be triggered to be reprobed.  Move all the deferred devices
190	 * into the active list so they can be retried by the workqueue
191	 */
192	mutex_lock(&deferred_probe_mutex);
193	atomic_inc(&deferred_trigger_count);
194	list_splice_tail_init(&deferred_probe_pending_list,
195			      &deferred_probe_active_list);
196	mutex_unlock(&deferred_probe_mutex);
197
198	/*
199	 * Kick the re-probe thread.  It may already be scheduled, but it is
200	 * safe to kick it again.
201	 */
202	schedule_work(&deferred_probe_work);
203}
204
205/**
206 * device_block_probing() - Block/defere device's probes
207 *
208 *	It will disable probing of devices and defer their probes instead.
209 */
210void device_block_probing(void)
211{
212	defer_all_probes = true;
213	/* sync with probes to avoid races. */
214	wait_for_device_probe();
215}
216
217/**
218 * device_unblock_probing() - Unblock/enable device's probes
219 *
220 *	It will restore normal behavior and trigger re-probing of deferred
221 * devices.
222 */
223void device_unblock_probing(void)
224{
225	defer_all_probes = false;
226	driver_deferred_probe_trigger();
227}
228
229/**
230 * deferred_probe_initcall() - Enable probing of deferred devices
231 *
232 * We don't want to get in the way when the bulk of drivers are getting probed.
233 * Instead, this initcall makes sure that deferred probing is delayed until
234 * late_initcall time.
235 */
236static int deferred_probe_initcall(void)
237{
 
 
 
 
238	driver_deferred_probe_enable = true;
239	driver_deferred_probe_trigger();
240	/* Sort as many dependencies as possible before exiting initcalls */
241	flush_work(&deferred_probe_work);
242	initcalls_done = true;
243	return 0;
244}
245late_initcall(deferred_probe_initcall);
246
247/**
248 * device_is_bound() - Check if device is bound to a driver
249 * @dev: device to check
250 *
251 * Returns true if passed device has already finished probing successfully
252 * against a driver.
253 *
254 * This function must be called with the device lock held.
255 */
256bool device_is_bound(struct device *dev)
257{
258	return dev->p && klist_node_attached(&dev->p->knode_driver);
259}
260
261static void driver_bound(struct device *dev)
262{
263	if (device_is_bound(dev)) {
264		printk(KERN_WARNING "%s: device %s already bound\n",
265			__func__, kobject_name(&dev->kobj));
266		return;
267	}
268
269	pr_debug("driver: '%s': %s: bound to device '%s'\n", dev->driver->name,
270		 __func__, dev_name(dev));
271
272	klist_add_tail(&dev->p->knode_driver, &dev->driver->p->klist_devices);
273	device_links_driver_bound(dev);
274
275	device_pm_check_callbacks(dev);
276
277	/*
278	 * Make sure the device is no longer in one of the deferred lists and
279	 * kick off retrying all pending devices
280	 */
281	driver_deferred_probe_del(dev);
282	driver_deferred_probe_trigger();
283
284	if (dev->bus)
285		blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
286					     BUS_NOTIFY_BOUND_DRIVER, dev);
287
288	kobject_uevent(&dev->kobj, KOBJ_BIND);
289}
290
291static ssize_t coredump_store(struct device *dev, struct device_attribute *attr,
292			    const char *buf, size_t count)
293{
294	device_lock(dev);
295	dev->driver->coredump(dev);
296	device_unlock(dev);
297
298	return count;
299}
300static DEVICE_ATTR_WO(coredump);
301
302static int driver_sysfs_add(struct device *dev)
303{
304	int ret;
305
306	if (dev->bus)
307		blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
308					     BUS_NOTIFY_BIND_DRIVER, dev);
309
310	ret = sysfs_create_link(&dev->driver->p->kobj, &dev->kobj,
311				kobject_name(&dev->kobj));
312	if (ret)
313		goto fail;
314
315	ret = sysfs_create_link(&dev->kobj, &dev->driver->p->kobj,
316				"driver");
317	if (ret)
318		goto rm_dev;
319
320	if (!IS_ENABLED(CONFIG_DEV_COREDUMP) || !dev->driver->coredump ||
321	    !device_create_file(dev, &dev_attr_coredump))
322		return 0;
323
324	sysfs_remove_link(&dev->kobj, "driver");
325
326rm_dev:
327	sysfs_remove_link(&dev->driver->p->kobj,
328			  kobject_name(&dev->kobj));
329
330fail:
 
 
 
 
 
331	return ret;
332}
333
334static void driver_sysfs_remove(struct device *dev)
335{
336	struct device_driver *drv = dev->driver;
337
338	if (drv) {
339		if (drv->coredump)
340			device_remove_file(dev, &dev_attr_coredump);
341		sysfs_remove_link(&drv->p->kobj, kobject_name(&dev->kobj));
342		sysfs_remove_link(&dev->kobj, "driver");
343	}
344}
345
346/**
347 * device_bind_driver - bind a driver to one device.
348 * @dev: device.
349 *
350 * Allow manual attachment of a driver to a device.
351 * Caller must have already set @dev->driver.
352 *
353 * Note that this does not modify the bus reference count
354 * nor take the bus's rwsem. Please verify those are accounted
355 * for before calling this. (It is ok to call with no other effort
356 * from a driver's probe() method.)
357 *
358 * This function must be called with the device lock held.
359 */
360int device_bind_driver(struct device *dev)
361{
362	int ret;
363
364	ret = driver_sysfs_add(dev);
365	if (!ret)
366		driver_bound(dev);
367	else if (dev->bus)
368		blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
369					     BUS_NOTIFY_DRIVER_NOT_BOUND, dev);
370	return ret;
371}
372EXPORT_SYMBOL_GPL(device_bind_driver);
373
374static atomic_t probe_count = ATOMIC_INIT(0);
375static DECLARE_WAIT_QUEUE_HEAD(probe_waitqueue);
376
377static void driver_deferred_probe_add_trigger(struct device *dev,
378					      int local_trigger_count)
379{
380	driver_deferred_probe_add(dev);
381	/* Did a trigger occur while probing? Need to re-trigger if yes */
382	if (local_trigger_count != atomic_read(&deferred_trigger_count))
383		driver_deferred_probe_trigger();
384}
385
386static int really_probe(struct device *dev, struct device_driver *drv)
387{
388	int ret = -EPROBE_DEFER;
389	int local_trigger_count = atomic_read(&deferred_trigger_count);
390	bool test_remove = IS_ENABLED(CONFIG_DEBUG_TEST_DRIVER_REMOVE) &&
391			   !drv->suppress_bind_attrs;
392
393	if (defer_all_probes) {
394		/*
395		 * Value of defer_all_probes can be set only by
396		 * device_defer_all_probes_enable() which, in turn, will call
397		 * wait_for_device_probe() right after that to avoid any races.
398		 */
399		dev_dbg(dev, "Driver %s force probe deferral\n", drv->name);
400		driver_deferred_probe_add(dev);
401		return ret;
402	}
403
404	ret = device_links_check_suppliers(dev);
405	if (ret == -EPROBE_DEFER)
406		driver_deferred_probe_add_trigger(dev, local_trigger_count);
407	if (ret)
408		return ret;
409
410	atomic_inc(&probe_count);
411	pr_debug("bus: '%s': %s: probing driver %s with device %s\n",
412		 drv->bus->name, __func__, drv->name, dev_name(dev));
413	WARN_ON(!list_empty(&dev->devres_head));
414
415re_probe:
416	dev->driver = drv;
417
418	/* If using pinctrl, bind pins now before probing */
419	ret = pinctrl_bind_pins(dev);
420	if (ret)
421		goto pinctrl_bind_failed;
422
423	ret = dma_configure(dev);
424	if (ret)
425		goto dma_failed;
426
427	if (driver_sysfs_add(dev)) {
428		printk(KERN_ERR "%s: driver_sysfs_add(%s) failed\n",
429			__func__, dev_name(dev));
430		goto probe_failed;
431	}
432
433	if (dev->pm_domain && dev->pm_domain->activate) {
434		ret = dev->pm_domain->activate(dev);
435		if (ret)
436			goto probe_failed;
437	}
438
439	/*
440	 * Ensure devices are listed in devices_kset in correct order
441	 * It's important to move Dev to the end of devices_kset before
442	 * calling .probe, because it could be recursive and parent Dev
443	 * should always go first
444	 */
445	devices_kset_move_last(dev);
446
447	if (dev->bus->probe) {
448		ret = dev->bus->probe(dev);
449		if (ret)
450			goto probe_failed;
451	} else if (drv->probe) {
452		ret = drv->probe(dev);
453		if (ret)
454			goto probe_failed;
455	}
456
457	if (test_remove) {
458		test_remove = false;
459
460		if (dev->bus->remove)
461			dev->bus->remove(dev);
462		else if (drv->remove)
463			drv->remove(dev);
464
465		devres_release_all(dev);
466		driver_sysfs_remove(dev);
467		dev->driver = NULL;
468		dev_set_drvdata(dev, NULL);
469		if (dev->pm_domain && dev->pm_domain->dismiss)
470			dev->pm_domain->dismiss(dev);
471		pm_runtime_reinit(dev);
472
473		goto re_probe;
474	}
475
476	pinctrl_init_done(dev);
477
478	if (dev->pm_domain && dev->pm_domain->sync)
479		dev->pm_domain->sync(dev);
480
481	driver_bound(dev);
482	ret = 1;
483	pr_debug("bus: '%s': %s: bound device %s to driver %s\n",
484		 drv->bus->name, __func__, dev_name(dev), drv->name);
485	goto done;
486
487probe_failed:
488	dma_deconfigure(dev);
489dma_failed:
490	if (dev->bus)
491		blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
492					     BUS_NOTIFY_DRIVER_NOT_BOUND, dev);
493pinctrl_bind_failed:
494	device_links_no_driver(dev);
495	devres_release_all(dev);
496	driver_sysfs_remove(dev);
497	dev->driver = NULL;
498	dev_set_drvdata(dev, NULL);
499	if (dev->pm_domain && dev->pm_domain->dismiss)
500		dev->pm_domain->dismiss(dev);
501	pm_runtime_reinit(dev);
502	dev_pm_set_driver_flags(dev, 0);
503
504	switch (ret) {
505	case -EPROBE_DEFER:
506		/* Driver requested deferred probing */
507		dev_dbg(dev, "Driver %s requests probe deferral\n", drv->name);
508		driver_deferred_probe_add_trigger(dev, local_trigger_count);
509		break;
510	case -ENODEV:
511	case -ENXIO:
512		pr_debug("%s: probe of %s rejects match %d\n",
513			 drv->name, dev_name(dev), ret);
514		break;
515	default:
516		/* driver matched but the probe failed */
517		printk(KERN_WARNING
518		       "%s: probe of %s failed with error %d\n",
519		       drv->name, dev_name(dev), ret);
 
 
 
520	}
521	/*
522	 * Ignore errors returned by ->probe so that the next driver can try
523	 * its luck.
524	 */
525	ret = 0;
526done:
527	atomic_dec(&probe_count);
528	wake_up(&probe_waitqueue);
529	return ret;
530}
531
532/**
533 * driver_probe_done
534 * Determine if the probe sequence is finished or not.
535 *
536 * Should somehow figure out how to use a semaphore, not an atomic variable...
537 */
538int driver_probe_done(void)
539{
540	pr_debug("%s: probe_count = %d\n", __func__,
541		 atomic_read(&probe_count));
542	if (atomic_read(&probe_count))
543		return -EBUSY;
544	return 0;
545}
546
547/**
548 * wait_for_device_probe
549 * Wait for device probing to be completed.
550 */
551void wait_for_device_probe(void)
552{
553	/* wait for the deferred probe workqueue to finish */
554	flush_work(&deferred_probe_work);
555
556	/* wait for the known devices to complete their probing */
557	wait_event(probe_waitqueue, atomic_read(&probe_count) == 0);
558	async_synchronize_full();
 
559}
560EXPORT_SYMBOL_GPL(wait_for_device_probe);
561
562/**
563 * driver_probe_device - attempt to bind device & driver together
564 * @drv: driver to bind a device to
565 * @dev: device to try to bind to the driver
566 *
567 * This function returns -ENODEV if the device is not registered,
568 * 1 if the device is bound successfully and 0 otherwise.
569 *
570 * This function must be called with @dev lock held.  When called for a
571 * USB interface, @dev->parent lock must be held as well.
572 *
573 * If the device has a parent, runtime-resume the parent before driver probing.
574 */
575int driver_probe_device(struct device_driver *drv, struct device *dev)
576{
577	int ret = 0;
578
579	if (!device_is_registered(dev))
580		return -ENODEV;
581
582	pr_debug("bus: '%s': %s: matched device %s with driver %s\n",
583		 drv->bus->name, __func__, dev_name(dev), drv->name);
584
585	pm_runtime_get_suppliers(dev);
586	if (dev->parent)
587		pm_runtime_get_sync(dev->parent);
588
589	pm_runtime_barrier(dev);
590	ret = really_probe(dev, drv);
591	pm_request_idle(dev);
592
593	if (dev->parent)
594		pm_runtime_put(dev->parent);
595
596	pm_runtime_put_suppliers(dev);
597	return ret;
598}
599
600bool driver_allows_async_probing(struct device_driver *drv)
601{
602	switch (drv->probe_type) {
603	case PROBE_PREFER_ASYNCHRONOUS:
604		return true;
605
606	case PROBE_FORCE_SYNCHRONOUS:
607		return false;
608
609	default:
610		if (module_requested_async_probing(drv->owner))
611			return true;
612
613		return false;
614	}
615}
616
617struct device_attach_data {
618	struct device *dev;
619
620	/*
621	 * Indicates whether we are are considering asynchronous probing or
622	 * not. Only initial binding after device or driver registration
623	 * (including deferral processing) may be done asynchronously, the
624	 * rest is always synchronous, as we expect it is being done by
625	 * request from userspace.
626	 */
627	bool check_async;
628
629	/*
630	 * Indicates if we are binding synchronous or asynchronous drivers.
631	 * When asynchronous probing is enabled we'll execute 2 passes
632	 * over drivers: first pass doing synchronous probing and second
633	 * doing asynchronous probing (if synchronous did not succeed -
634	 * most likely because there was no driver requiring synchronous
635	 * probing - and we found asynchronous driver during first pass).
636	 * The 2 passes are done because we can't shoot asynchronous
637	 * probe for given device and driver from bus_for_each_drv() since
638	 * driver pointer is not guaranteed to stay valid once
639	 * bus_for_each_drv() iterates to the next driver on the bus.
640	 */
641	bool want_async;
642
643	/*
644	 * We'll set have_async to 'true' if, while scanning for matching
645	 * driver, we'll encounter one that requests asynchronous probing.
646	 */
647	bool have_async;
648};
649
650static int __device_attach_driver(struct device_driver *drv, void *_data)
651{
652	struct device_attach_data *data = _data;
653	struct device *dev = data->dev;
654	bool async_allowed;
655	int ret;
656
657	/*
658	 * Check if device has already been claimed. This may
659	 * happen with driver loading, device discovery/registration,
660	 * and deferred probe processing happens all at once with
661	 * multiple threads.
662	 */
663	if (dev->driver)
664		return -EBUSY;
665
666	ret = driver_match_device(drv, dev);
667	if (ret == 0) {
668		/* no match */
669		return 0;
670	} else if (ret == -EPROBE_DEFER) {
671		dev_dbg(dev, "Device match requests probe deferral\n");
672		driver_deferred_probe_add(dev);
673	} else if (ret < 0) {
674		dev_dbg(dev, "Bus failed to match device: %d", ret);
675		return ret;
676	} /* ret > 0 means positive match */
677
678	async_allowed = driver_allows_async_probing(drv);
679
680	if (async_allowed)
681		data->have_async = true;
682
683	if (data->check_async && async_allowed != data->want_async)
684		return 0;
685
686	return driver_probe_device(drv, dev);
687}
688
689static void __device_attach_async_helper(void *_dev, async_cookie_t cookie)
690{
691	struct device *dev = _dev;
692	struct device_attach_data data = {
693		.dev		= dev,
694		.check_async	= true,
695		.want_async	= true,
696	};
697
698	device_lock(dev);
699
700	if (dev->parent)
701		pm_runtime_get_sync(dev->parent);
702
703	bus_for_each_drv(dev->bus, NULL, &data, __device_attach_driver);
704	dev_dbg(dev, "async probe completed\n");
705
706	pm_request_idle(dev);
707
708	if (dev->parent)
709		pm_runtime_put(dev->parent);
710
711	device_unlock(dev);
712
713	put_device(dev);
714}
715
716static int __device_attach(struct device *dev, bool allow_async)
717{
718	int ret = 0;
719
720	device_lock(dev);
721	if (dev->driver) {
722		if (device_is_bound(dev)) {
723			ret = 1;
724			goto out_unlock;
725		}
726		ret = device_bind_driver(dev);
727		if (ret == 0)
728			ret = 1;
729		else {
730			dev->driver = NULL;
731			ret = 0;
732		}
733	} else {
734		struct device_attach_data data = {
735			.dev = dev,
736			.check_async = allow_async,
737			.want_async = false,
738		};
739
740		if (dev->parent)
741			pm_runtime_get_sync(dev->parent);
742
743		ret = bus_for_each_drv(dev->bus, NULL, &data,
744					__device_attach_driver);
745		if (!ret && allow_async && data.have_async) {
746			/*
747			 * If we could not find appropriate driver
748			 * synchronously and we are allowed to do
749			 * async probes and there are drivers that
750			 * want to probe asynchronously, we'll
751			 * try them.
752			 */
753			dev_dbg(dev, "scheduling asynchronous probe\n");
754			get_device(dev);
755			async_schedule(__device_attach_async_helper, dev);
756		} else {
757			pm_request_idle(dev);
758		}
759
760		if (dev->parent)
761			pm_runtime_put(dev->parent);
762	}
763out_unlock:
764	device_unlock(dev);
765	return ret;
766}
767
768/**
769 * device_attach - try to attach device to a driver.
770 * @dev: device.
771 *
772 * Walk the list of drivers that the bus has and call
773 * driver_probe_device() for each pair. If a compatible
774 * pair is found, break out and return.
775 *
776 * Returns 1 if the device was bound to a driver;
777 * 0 if no matching driver was found;
778 * -ENODEV if the device is not registered.
779 *
780 * When called for a USB interface, @dev->parent lock must be held.
781 */
782int device_attach(struct device *dev)
783{
784	return __device_attach(dev, false);
785}
786EXPORT_SYMBOL_GPL(device_attach);
787
788void device_initial_probe(struct device *dev)
789{
790	__device_attach(dev, true);
791}
792
793static int __driver_attach(struct device *dev, void *data)
794{
795	struct device_driver *drv = data;
796	int ret;
797
798	/*
799	 * Lock device and try to bind to it. We drop the error
800	 * here and always return 0, because we need to keep trying
801	 * to bind to devices and some drivers will return an error
802	 * simply if it didn't support the device.
803	 *
804	 * driver_probe_device() will spit a warning if there
805	 * is an error.
806	 */
807
808	ret = driver_match_device(drv, dev);
809	if (ret == 0) {
810		/* no match */
811		return 0;
812	} else if (ret == -EPROBE_DEFER) {
813		dev_dbg(dev, "Device match requests probe deferral\n");
814		driver_deferred_probe_add(dev);
815	} else if (ret < 0) {
816		dev_dbg(dev, "Bus failed to match device: %d", ret);
817		return ret;
818	} /* ret > 0 means positive match */
819
820	if (dev->parent)	/* Needed for USB */
821		device_lock(dev->parent);
822	device_lock(dev);
823	if (!dev->driver)
824		driver_probe_device(drv, dev);
825	device_unlock(dev);
826	if (dev->parent)
827		device_unlock(dev->parent);
828
829	return 0;
830}
831
832/**
833 * driver_attach - try to bind driver to devices.
834 * @drv: driver.
835 *
836 * Walk the list of devices that the bus has on it and try to
837 * match the driver with each one.  If driver_probe_device()
838 * returns 0 and the @dev->driver is set, we've found a
839 * compatible pair.
840 */
841int driver_attach(struct device_driver *drv)
842{
843	return bus_for_each_dev(drv->bus, NULL, drv, __driver_attach);
844}
845EXPORT_SYMBOL_GPL(driver_attach);
846
847/*
848 * __device_release_driver() must be called with @dev lock held.
849 * When called for a USB interface, @dev->parent lock must be held as well.
850 */
851static void __device_release_driver(struct device *dev, struct device *parent)
852{
853	struct device_driver *drv;
854
855	drv = dev->driver;
856	if (drv) {
857		if (driver_allows_async_probing(drv))
858			async_synchronize_full();
859
860		while (device_links_busy(dev)) {
861			device_unlock(dev);
862			if (parent)
863				device_unlock(parent);
864
865			device_links_unbind_consumers(dev);
866			if (parent)
867				device_lock(parent);
868
869			device_lock(dev);
870			/*
871			 * A concurrent invocation of the same function might
872			 * have released the driver successfully while this one
873			 * was waiting, so check for that.
874			 */
875			if (dev->driver != drv)
876				return;
877		}
878
879		pm_runtime_get_sync(dev);
880		pm_runtime_clean_up_links(dev);
881
882		driver_sysfs_remove(dev);
883
884		if (dev->bus)
885			blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
886						     BUS_NOTIFY_UNBIND_DRIVER,
887						     dev);
888
889		pm_runtime_put_sync(dev);
890
891		if (dev->bus && dev->bus->remove)
892			dev->bus->remove(dev);
893		else if (drv->remove)
894			drv->remove(dev);
895
896		device_links_driver_cleanup(dev);
897		dma_deconfigure(dev);
898
899		devres_release_all(dev);
900		dev->driver = NULL;
901		dev_set_drvdata(dev, NULL);
902		if (dev->pm_domain && dev->pm_domain->dismiss)
903			dev->pm_domain->dismiss(dev);
904		pm_runtime_reinit(dev);
905		dev_pm_set_driver_flags(dev, 0);
906
907		klist_remove(&dev->p->knode_driver);
908		device_pm_check_callbacks(dev);
909		if (dev->bus)
910			blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
911						     BUS_NOTIFY_UNBOUND_DRIVER,
912						     dev);
913
914		kobject_uevent(&dev->kobj, KOBJ_UNBIND);
915	}
916}
917
918void device_release_driver_internal(struct device *dev,
919				    struct device_driver *drv,
920				    struct device *parent)
921{
922	if (parent)
923		device_lock(parent);
924
925	device_lock(dev);
926	if (!drv || drv == dev->driver)
927		__device_release_driver(dev, parent);
928
929	device_unlock(dev);
930	if (parent)
931		device_unlock(parent);
932}
933
934/**
935 * device_release_driver - manually detach device from driver.
936 * @dev: device.
937 *
938 * Manually detach device from driver.
939 * When called for a USB interface, @dev->parent lock must be held.
940 *
941 * If this function is to be called with @dev->parent lock held, ensure that
942 * the device's consumers are unbound in advance or that their locks can be
943 * acquired under the @dev->parent lock.
944 */
945void device_release_driver(struct device *dev)
946{
947	/*
948	 * If anyone calls device_release_driver() recursively from
949	 * within their ->remove callback for the same device, they
950	 * will deadlock right here.
951	 */
952	device_release_driver_internal(dev, NULL, NULL);
 
 
953}
954EXPORT_SYMBOL_GPL(device_release_driver);
955
956/**
957 * driver_detach - detach driver from all devices it controls.
958 * @drv: driver.
959 */
960void driver_detach(struct device_driver *drv)
961{
962	struct device_private *dev_prv;
963	struct device *dev;
964
965	for (;;) {
966		spin_lock(&drv->p->klist_devices.k_lock);
967		if (list_empty(&drv->p->klist_devices.k_list)) {
968			spin_unlock(&drv->p->klist_devices.k_lock);
969			break;
970		}
971		dev_prv = list_entry(drv->p->klist_devices.k_list.prev,
972				     struct device_private,
973				     knode_driver.n_node);
974		dev = dev_prv->device;
975		get_device(dev);
976		spin_unlock(&drv->p->klist_devices.k_lock);
977		device_release_driver_internal(dev, drv, dev->parent);
 
 
 
 
 
 
 
 
978		put_device(dev);
979	}
980}