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Linux/drivers/base/dd.c

  1 /*
  2  * drivers/base/dd.c - The core device/driver interactions.
  3  *
  4  * This file contains the (sometimes tricky) code that controls the
  5  * interactions between devices and drivers, which primarily includes
  6  * driver binding and unbinding.
  7  *
  8  * All of this code used to exist in drivers/base/bus.c, but was
  9  * relocated to here in the name of compartmentalization (since it wasn't
 10  * strictly code just for the 'struct bus_type'.
 11  *
 12  * Copyright (c) 2002-5 Patrick Mochel
 13  * Copyright (c) 2002-3 Open Source Development Labs
 14  * Copyright (c) 2007-2009 Greg Kroah-Hartman <gregkh@suse.de>
 15  * Copyright (c) 2007-2009 Novell Inc.
 16  *
 17  * This file is released under the GPLv2
 18  */
 19 
 20 #include <linux/device.h>
 21 #include <linux/delay.h>
 22 #include <linux/module.h>
 23 #include <linux/kthread.h>
 24 #include <linux/wait.h>
 25 #include <linux/async.h>
 26 #include <linux/pm_runtime.h>
 27 #include <linux/pinctrl/devinfo.h>
 28 
 29 #include "base.h"
 30 #include "power/power.h"
 31 
 32 /*
 33  * Deferred Probe infrastructure.
 34  *
 35  * Sometimes driver probe order matters, but the kernel doesn't always have
 36  * dependency information which means some drivers will get probed before a
 37  * resource it depends on is available.  For example, an SDHCI driver may
 38  * first need a GPIO line from an i2c GPIO controller before it can be
 39  * initialized.  If a required resource is not available yet, a driver can
 40  * request probing to be deferred by returning -EPROBE_DEFER from its probe hook
 41  *
 42  * Deferred probe maintains two lists of devices, a pending list and an active
 43  * list.  A driver returning -EPROBE_DEFER causes the device to be added to the
 44  * pending list.  A successful driver probe will trigger moving all devices
 45  * from the pending to the active list so that the workqueue will eventually
 46  * retry them.
 47  *
 48  * The deferred_probe_mutex must be held any time the deferred_probe_*_list
 49  * of the (struct device*)->p->deferred_probe pointers are manipulated
 50  */
 51 static DEFINE_MUTEX(deferred_probe_mutex);
 52 static LIST_HEAD(deferred_probe_pending_list);
 53 static LIST_HEAD(deferred_probe_active_list);
 54 static struct workqueue_struct *deferred_wq;
 55 static atomic_t deferred_trigger_count = ATOMIC_INIT(0);
 56 
 57 /*
 58  * In some cases, like suspend to RAM or hibernation, It might be reasonable
 59  * to prohibit probing of devices as it could be unsafe.
 60  * Once defer_all_probes is true all drivers probes will be forcibly deferred.
 61  */
 62 static bool defer_all_probes;
 63 
 64 /*
 65  * deferred_probe_work_func() - Retry probing devices in the active list.
 66  */
 67 static void deferred_probe_work_func(struct work_struct *work)
 68 {
 69         struct device *dev;
 70         struct device_private *private;
 71         /*
 72          * This block processes every device in the deferred 'active' list.
 73          * Each device is removed from the active list and passed to
 74          * bus_probe_device() to re-attempt the probe.  The loop continues
 75          * until every device in the active list is removed and retried.
 76          *
 77          * Note: Once the device is removed from the list and the mutex is
 78          * released, it is possible for the device get freed by another thread
 79          * and cause a illegal pointer dereference.  This code uses
 80          * get/put_device() to ensure the device structure cannot disappear
 81          * from under our feet.
 82          */
 83         mutex_lock(&deferred_probe_mutex);
 84         while (!list_empty(&deferred_probe_active_list)) {
 85                 private = list_first_entry(&deferred_probe_active_list,
 86                                         typeof(*dev->p), deferred_probe);
 87                 dev = private->device;
 88                 list_del_init(&private->deferred_probe);
 89 
 90                 get_device(dev);
 91 
 92                 /*
 93                  * Drop the mutex while probing each device; the probe path may
 94                  * manipulate the deferred list
 95                  */
 96                 mutex_unlock(&deferred_probe_mutex);
 97 
 98                 /*
 99                  * Force the device to the end of the dpm_list since
100                  * the PM code assumes that the order we add things to
101                  * the list is a good order for suspend but deferred
102                  * probe makes that very unsafe.
103                  */
104                 device_pm_lock();
105                 device_pm_move_last(dev);
106                 device_pm_unlock();
107 
108                 dev_dbg(dev, "Retrying from deferred list\n");
109                 bus_probe_device(dev);
110 
111                 mutex_lock(&deferred_probe_mutex);
112 
113                 put_device(dev);
114         }
115         mutex_unlock(&deferred_probe_mutex);
116 }
117 static DECLARE_WORK(deferred_probe_work, deferred_probe_work_func);
118 
119 static void driver_deferred_probe_add(struct device *dev)
120 {
121         mutex_lock(&deferred_probe_mutex);
122         if (list_empty(&dev->p->deferred_probe)) {
123                 dev_dbg(dev, "Added to deferred list\n");
124                 list_add_tail(&dev->p->deferred_probe, &deferred_probe_pending_list);
125         }
126         mutex_unlock(&deferred_probe_mutex);
127 }
128 
129 void driver_deferred_probe_del(struct device *dev)
130 {
131         mutex_lock(&deferred_probe_mutex);
132         if (!list_empty(&dev->p->deferred_probe)) {
133                 dev_dbg(dev, "Removed from deferred list\n");
134                 list_del_init(&dev->p->deferred_probe);
135         }
136         mutex_unlock(&deferred_probe_mutex);
137 }
138 
139 static bool driver_deferred_probe_enable = false;
140 /**
141  * driver_deferred_probe_trigger() - Kick off re-probing deferred devices
142  *
143  * This functions moves all devices from the pending list to the active
144  * list and schedules the deferred probe workqueue to process them.  It
145  * should be called anytime a driver is successfully bound to a device.
146  *
147  * Note, there is a race condition in multi-threaded probe. In the case where
148  * more than one device is probing at the same time, it is possible for one
149  * probe to complete successfully while another is about to defer. If the second
150  * depends on the first, then it will get put on the pending list after the
151  * trigger event has already occurred and will be stuck there.
152  *
153  * The atomic 'deferred_trigger_count' is used to determine if a successful
154  * trigger has occurred in the midst of probing a driver. If the trigger count
155  * changes in the midst of a probe, then deferred processing should be triggered
156  * again.
157  */
158 static void driver_deferred_probe_trigger(void)
159 {
160         if (!driver_deferred_probe_enable)
161                 return;
162 
163         /*
164          * A successful probe means that all the devices in the pending list
165          * should be triggered to be reprobed.  Move all the deferred devices
166          * into the active list so they can be retried by the workqueue
167          */
168         mutex_lock(&deferred_probe_mutex);
169         atomic_inc(&deferred_trigger_count);
170         list_splice_tail_init(&deferred_probe_pending_list,
171                               &deferred_probe_active_list);
172         mutex_unlock(&deferred_probe_mutex);
173 
174         /*
175          * Kick the re-probe thread.  It may already be scheduled, but it is
176          * safe to kick it again.
177          */
178         queue_work(deferred_wq, &deferred_probe_work);
179 }
180 
181 /**
182  * device_block_probing() - Block/defere device's probes
183  *
184  *      It will disable probing of devices and defer their probes instead.
185  */
186 void device_block_probing(void)
187 {
188         defer_all_probes = true;
189         /* sync with probes to avoid races. */
190         wait_for_device_probe();
191 }
192 
193 /**
194  * device_unblock_probing() - Unblock/enable device's probes
195  *
196  *      It will restore normal behavior and trigger re-probing of deferred
197  * devices.
198  */
199 void device_unblock_probing(void)
200 {
201         defer_all_probes = false;
202         driver_deferred_probe_trigger();
203 }
204 
205 /**
206  * deferred_probe_initcall() - Enable probing of deferred devices
207  *
208  * We don't want to get in the way when the bulk of drivers are getting probed.
209  * Instead, this initcall makes sure that deferred probing is delayed until
210  * late_initcall time.
211  */
212 static int deferred_probe_initcall(void)
213 {
214         deferred_wq = create_singlethread_workqueue("deferwq");
215         if (WARN_ON(!deferred_wq))
216                 return -ENOMEM;
217 
218         driver_deferred_probe_enable = true;
219         driver_deferred_probe_trigger();
220         /* Sort as many dependencies as possible before exiting initcalls */
221         flush_workqueue(deferred_wq);
222         return 0;
223 }
224 late_initcall(deferred_probe_initcall);
225 
226 /**
227  * device_is_bound() - Check if device is bound to a driver
228  * @dev: device to check
229  *
230  * Returns true if passed device has already finished probing successfully
231  * against a driver.
232  *
233  * This function must be called with the device lock held.
234  */
235 bool device_is_bound(struct device *dev)
236 {
237         return dev->p && klist_node_attached(&dev->p->knode_driver);
238 }
239 
240 static void driver_bound(struct device *dev)
241 {
242         if (device_is_bound(dev)) {
243                 printk(KERN_WARNING "%s: device %s already bound\n",
244                         __func__, kobject_name(&dev->kobj));
245                 return;
246         }
247 
248         pr_debug("driver: '%s': %s: bound to device '%s'\n", dev->driver->name,
249                  __func__, dev_name(dev));
250 
251         klist_add_tail(&dev->p->knode_driver, &dev->driver->p->klist_devices);
252 
253         device_pm_check_callbacks(dev);
254 
255         /*
256          * Make sure the device is no longer in one of the deferred lists and
257          * kick off retrying all pending devices
258          */
259         driver_deferred_probe_del(dev);
260         driver_deferred_probe_trigger();
261 
262         if (dev->bus)
263                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
264                                              BUS_NOTIFY_BOUND_DRIVER, dev);
265 }
266 
267 static int driver_sysfs_add(struct device *dev)
268 {
269         int ret;
270 
271         if (dev->bus)
272                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
273                                              BUS_NOTIFY_BIND_DRIVER, dev);
274 
275         ret = sysfs_create_link(&dev->driver->p->kobj, &dev->kobj,
276                           kobject_name(&dev->kobj));
277         if (ret == 0) {
278                 ret = sysfs_create_link(&dev->kobj, &dev->driver->p->kobj,
279                                         "driver");
280                 if (ret)
281                         sysfs_remove_link(&dev->driver->p->kobj,
282                                         kobject_name(&dev->kobj));
283         }
284         return ret;
285 }
286 
287 static void driver_sysfs_remove(struct device *dev)
288 {
289         struct device_driver *drv = dev->driver;
290 
291         if (drv) {
292                 sysfs_remove_link(&drv->p->kobj, kobject_name(&dev->kobj));
293                 sysfs_remove_link(&dev->kobj, "driver");
294         }
295 }
296 
297 /**
298  * device_bind_driver - bind a driver to one device.
299  * @dev: device.
300  *
301  * Allow manual attachment of a driver to a device.
302  * Caller must have already set @dev->driver.
303  *
304  * Note that this does not modify the bus reference count
305  * nor take the bus's rwsem. Please verify those are accounted
306  * for before calling this. (It is ok to call with no other effort
307  * from a driver's probe() method.)
308  *
309  * This function must be called with the device lock held.
310  */
311 int device_bind_driver(struct device *dev)
312 {
313         int ret;
314 
315         ret = driver_sysfs_add(dev);
316         if (!ret)
317                 driver_bound(dev);
318         else if (dev->bus)
319                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
320                                              BUS_NOTIFY_DRIVER_NOT_BOUND, dev);
321         return ret;
322 }
323 EXPORT_SYMBOL_GPL(device_bind_driver);
324 
325 static atomic_t probe_count = ATOMIC_INIT(0);
326 static DECLARE_WAIT_QUEUE_HEAD(probe_waitqueue);
327 
328 static int really_probe(struct device *dev, struct device_driver *drv)
329 {
330         int ret = -EPROBE_DEFER;
331         int local_trigger_count = atomic_read(&deferred_trigger_count);
332 
333         if (defer_all_probes) {
334                 /*
335                  * Value of defer_all_probes can be set only by
336                  * device_defer_all_probes_enable() which, in turn, will call
337                  * wait_for_device_probe() right after that to avoid any races.
338                  */
339                 dev_dbg(dev, "Driver %s force probe deferral\n", drv->name);
340                 driver_deferred_probe_add(dev);
341                 return ret;
342         }
343 
344         atomic_inc(&probe_count);
345         pr_debug("bus: '%s': %s: probing driver %s with device %s\n",
346                  drv->bus->name, __func__, drv->name, dev_name(dev));
347         WARN_ON(!list_empty(&dev->devres_head));
348 
349         dev->driver = drv;
350 
351         /* If using pinctrl, bind pins now before probing */
352         ret = pinctrl_bind_pins(dev);
353         if (ret)
354                 goto pinctrl_bind_failed;
355 
356         if (driver_sysfs_add(dev)) {
357                 printk(KERN_ERR "%s: driver_sysfs_add(%s) failed\n",
358                         __func__, dev_name(dev));
359                 goto probe_failed;
360         }
361 
362         if (dev->pm_domain && dev->pm_domain->activate) {
363                 ret = dev->pm_domain->activate(dev);
364                 if (ret)
365                         goto probe_failed;
366         }
367 
368         /*
369          * Ensure devices are listed in devices_kset in correct order
370          * It's important to move Dev to the end of devices_kset before
371          * calling .probe, because it could be recursive and parent Dev
372          * should always go first
373          */
374         devices_kset_move_last(dev);
375 
376         if (dev->bus->probe) {
377                 ret = dev->bus->probe(dev);
378                 if (ret)
379                         goto probe_failed;
380         } else if (drv->probe) {
381                 ret = drv->probe(dev);
382                 if (ret)
383                         goto probe_failed;
384         }
385 
386         pinctrl_init_done(dev);
387 
388         if (dev->pm_domain && dev->pm_domain->sync)
389                 dev->pm_domain->sync(dev);
390 
391         driver_bound(dev);
392         ret = 1;
393         pr_debug("bus: '%s': %s: bound device %s to driver %s\n",
394                  drv->bus->name, __func__, dev_name(dev), drv->name);
395         goto done;
396 
397 probe_failed:
398         if (dev->bus)
399                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
400                                              BUS_NOTIFY_DRIVER_NOT_BOUND, dev);
401 pinctrl_bind_failed:
402         devres_release_all(dev);
403         driver_sysfs_remove(dev);
404         dev->driver = NULL;
405         dev_set_drvdata(dev, NULL);
406         if (dev->pm_domain && dev->pm_domain->dismiss)
407                 dev->pm_domain->dismiss(dev);
408         pm_runtime_reinit(dev);
409 
410         switch (ret) {
411         case -EPROBE_DEFER:
412                 /* Driver requested deferred probing */
413                 dev_dbg(dev, "Driver %s requests probe deferral\n", drv->name);
414                 driver_deferred_probe_add(dev);
415                 /* Did a trigger occur while probing? Need to re-trigger if yes */
416                 if (local_trigger_count != atomic_read(&deferred_trigger_count))
417                         driver_deferred_probe_trigger();
418                 break;
419         case -ENODEV:
420         case -ENXIO:
421                 pr_debug("%s: probe of %s rejects match %d\n",
422                          drv->name, dev_name(dev), ret);
423                 break;
424         default:
425                 /* driver matched but the probe failed */
426                 printk(KERN_WARNING
427                        "%s: probe of %s failed with error %d\n",
428                        drv->name, dev_name(dev), ret);
429         }
430         /*
431          * Ignore errors returned by ->probe so that the next driver can try
432          * its luck.
433          */
434         ret = 0;
435 done:
436         atomic_dec(&probe_count);
437         wake_up(&probe_waitqueue);
438         return ret;
439 }
440 
441 /**
442  * driver_probe_done
443  * Determine if the probe sequence is finished or not.
444  *
445  * Should somehow figure out how to use a semaphore, not an atomic variable...
446  */
447 int driver_probe_done(void)
448 {
449         pr_debug("%s: probe_count = %d\n", __func__,
450                  atomic_read(&probe_count));
451         if (atomic_read(&probe_count))
452                 return -EBUSY;
453         return 0;
454 }
455 
456 /**
457  * wait_for_device_probe
458  * Wait for device probing to be completed.
459  */
460 void wait_for_device_probe(void)
461 {
462         /* wait for the deferred probe workqueue to finish */
463         if (driver_deferred_probe_enable)
464                 flush_workqueue(deferred_wq);
465 
466         /* wait for the known devices to complete their probing */
467         wait_event(probe_waitqueue, atomic_read(&probe_count) == 0);
468         async_synchronize_full();
469 }
470 EXPORT_SYMBOL_GPL(wait_for_device_probe);
471 
472 /**
473  * driver_probe_device - attempt to bind device & driver together
474  * @drv: driver to bind a device to
475  * @dev: device to try to bind to the driver
476  *
477  * This function returns -ENODEV if the device is not registered,
478  * 1 if the device is bound successfully and 0 otherwise.
479  *
480  * This function must be called with @dev lock held.  When called for a
481  * USB interface, @dev->parent lock must be held as well.
482  *
483  * If the device has a parent, runtime-resume the parent before driver probing.
484  */
485 int driver_probe_device(struct device_driver *drv, struct device *dev)
486 {
487         int ret = 0;
488 
489         if (!device_is_registered(dev))
490                 return -ENODEV;
491 
492         pr_debug("bus: '%s': %s: matched device %s with driver %s\n",
493                  drv->bus->name, __func__, dev_name(dev), drv->name);
494 
495         if (dev->parent)
496                 pm_runtime_get_sync(dev->parent);
497 
498         pm_runtime_barrier(dev);
499         ret = really_probe(dev, drv);
500         pm_request_idle(dev);
501 
502         if (dev->parent)
503                 pm_runtime_put(dev->parent);
504 
505         return ret;
506 }
507 
508 bool driver_allows_async_probing(struct device_driver *drv)
509 {
510         switch (drv->probe_type) {
511         case PROBE_PREFER_ASYNCHRONOUS:
512                 return true;
513 
514         case PROBE_FORCE_SYNCHRONOUS:
515                 return false;
516 
517         default:
518                 if (module_requested_async_probing(drv->owner))
519                         return true;
520 
521                 return false;
522         }
523 }
524 
525 struct device_attach_data {
526         struct device *dev;
527 
528         /*
529          * Indicates whether we are are considering asynchronous probing or
530          * not. Only initial binding after device or driver registration
531          * (including deferral processing) may be done asynchronously, the
532          * rest is always synchronous, as we expect it is being done by
533          * request from userspace.
534          */
535         bool check_async;
536 
537         /*
538          * Indicates if we are binding synchronous or asynchronous drivers.
539          * When asynchronous probing is enabled we'll execute 2 passes
540          * over drivers: first pass doing synchronous probing and second
541          * doing asynchronous probing (if synchronous did not succeed -
542          * most likely because there was no driver requiring synchronous
543          * probing - and we found asynchronous driver during first pass).
544          * The 2 passes are done because we can't shoot asynchronous
545          * probe for given device and driver from bus_for_each_drv() since
546          * driver pointer is not guaranteed to stay valid once
547          * bus_for_each_drv() iterates to the next driver on the bus.
548          */
549         bool want_async;
550 
551         /*
552          * We'll set have_async to 'true' if, while scanning for matching
553          * driver, we'll encounter one that requests asynchronous probing.
554          */
555         bool have_async;
556 };
557 
558 static int __device_attach_driver(struct device_driver *drv, void *_data)
559 {
560         struct device_attach_data *data = _data;
561         struct device *dev = data->dev;
562         bool async_allowed;
563         int ret;
564 
565         /*
566          * Check if device has already been claimed. This may
567          * happen with driver loading, device discovery/registration,
568          * and deferred probe processing happens all at once with
569          * multiple threads.
570          */
571         if (dev->driver)
572                 return -EBUSY;
573 
574         ret = driver_match_device(drv, dev);
575         if (ret == 0) {
576                 /* no match */
577                 return 0;
578         } else if (ret == -EPROBE_DEFER) {
579                 dev_dbg(dev, "Device match requests probe deferral\n");
580                 driver_deferred_probe_add(dev);
581         } else if (ret < 0) {
582                 dev_dbg(dev, "Bus failed to match device: %d", ret);
583                 return ret;
584         } /* ret > 0 means positive match */
585 
586         async_allowed = driver_allows_async_probing(drv);
587 
588         if (async_allowed)
589                 data->have_async = true;
590 
591         if (data->check_async && async_allowed != data->want_async)
592                 return 0;
593 
594         return driver_probe_device(drv, dev);
595 }
596 
597 static void __device_attach_async_helper(void *_dev, async_cookie_t cookie)
598 {
599         struct device *dev = _dev;
600         struct device_attach_data data = {
601                 .dev            = dev,
602                 .check_async    = true,
603                 .want_async     = true,
604         };
605 
606         device_lock(dev);
607 
608         if (dev->parent)
609                 pm_runtime_get_sync(dev->parent);
610 
611         bus_for_each_drv(dev->bus, NULL, &data, __device_attach_driver);
612         dev_dbg(dev, "async probe completed\n");
613 
614         pm_request_idle(dev);
615 
616         if (dev->parent)
617                 pm_runtime_put(dev->parent);
618 
619         device_unlock(dev);
620 
621         put_device(dev);
622 }
623 
624 static int __device_attach(struct device *dev, bool allow_async)
625 {
626         int ret = 0;
627 
628         device_lock(dev);
629         if (dev->driver) {
630                 if (device_is_bound(dev)) {
631                         ret = 1;
632                         goto out_unlock;
633                 }
634                 ret = device_bind_driver(dev);
635                 if (ret == 0)
636                         ret = 1;
637                 else {
638                         dev->driver = NULL;
639                         ret = 0;
640                 }
641         } else {
642                 struct device_attach_data data = {
643                         .dev = dev,
644                         .check_async = allow_async,
645                         .want_async = false,
646                 };
647 
648                 if (dev->parent)
649                         pm_runtime_get_sync(dev->parent);
650 
651                 ret = bus_for_each_drv(dev->bus, NULL, &data,
652                                         __device_attach_driver);
653                 if (!ret && allow_async && data.have_async) {
654                         /*
655                          * If we could not find appropriate driver
656                          * synchronously and we are allowed to do
657                          * async probes and there are drivers that
658                          * want to probe asynchronously, we'll
659                          * try them.
660                          */
661                         dev_dbg(dev, "scheduling asynchronous probe\n");
662                         get_device(dev);
663                         async_schedule(__device_attach_async_helper, dev);
664                 } else {
665                         pm_request_idle(dev);
666                 }
667 
668                 if (dev->parent)
669                         pm_runtime_put(dev->parent);
670         }
671 out_unlock:
672         device_unlock(dev);
673         return ret;
674 }
675 
676 /**
677  * device_attach - try to attach device to a driver.
678  * @dev: device.
679  *
680  * Walk the list of drivers that the bus has and call
681  * driver_probe_device() for each pair. If a compatible
682  * pair is found, break out and return.
683  *
684  * Returns 1 if the device was bound to a driver;
685  * 0 if no matching driver was found;
686  * -ENODEV if the device is not registered.
687  *
688  * When called for a USB interface, @dev->parent lock must be held.
689  */
690 int device_attach(struct device *dev)
691 {
692         return __device_attach(dev, false);
693 }
694 EXPORT_SYMBOL_GPL(device_attach);
695 
696 void device_initial_probe(struct device *dev)
697 {
698         __device_attach(dev, true);
699 }
700 
701 static int __driver_attach(struct device *dev, void *data)
702 {
703         struct device_driver *drv = data;
704         int ret;
705 
706         /*
707          * Lock device and try to bind to it. We drop the error
708          * here and always return 0, because we need to keep trying
709          * to bind to devices and some drivers will return an error
710          * simply if it didn't support the device.
711          *
712          * driver_probe_device() will spit a warning if there
713          * is an error.
714          */
715 
716         ret = driver_match_device(drv, dev);
717         if (ret == 0) {
718                 /* no match */
719                 return 0;
720         } else if (ret == -EPROBE_DEFER) {
721                 dev_dbg(dev, "Device match requests probe deferral\n");
722                 driver_deferred_probe_add(dev);
723         } else if (ret < 0) {
724                 dev_dbg(dev, "Bus failed to match device: %d", ret);
725                 return ret;
726         } /* ret > 0 means positive match */
727 
728         if (dev->parent)        /* Needed for USB */
729                 device_lock(dev->parent);
730         device_lock(dev);
731         if (!dev->driver)
732                 driver_probe_device(drv, dev);
733         device_unlock(dev);
734         if (dev->parent)
735                 device_unlock(dev->parent);
736 
737         return 0;
738 }
739 
740 /**
741  * driver_attach - try to bind driver to devices.
742  * @drv: driver.
743  *
744  * Walk the list of devices that the bus has on it and try to
745  * match the driver with each one.  If driver_probe_device()
746  * returns 0 and the @dev->driver is set, we've found a
747  * compatible pair.
748  */
749 int driver_attach(struct device_driver *drv)
750 {
751         return bus_for_each_dev(drv->bus, NULL, drv, __driver_attach);
752 }
753 EXPORT_SYMBOL_GPL(driver_attach);
754 
755 /*
756  * __device_release_driver() must be called with @dev lock held.
757  * When called for a USB interface, @dev->parent lock must be held as well.
758  */
759 static void __device_release_driver(struct device *dev)
760 {
761         struct device_driver *drv;
762 
763         drv = dev->driver;
764         if (drv) {
765                 if (driver_allows_async_probing(drv))
766                         async_synchronize_full();
767 
768                 pm_runtime_get_sync(dev);
769 
770                 driver_sysfs_remove(dev);
771 
772                 if (dev->bus)
773                         blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
774                                                      BUS_NOTIFY_UNBIND_DRIVER,
775                                                      dev);
776 
777                 pm_runtime_put_sync(dev);
778 
779                 if (dev->bus && dev->bus->remove)
780                         dev->bus->remove(dev);
781                 else if (drv->remove)
782                         drv->remove(dev);
783                 devres_release_all(dev);
784                 dev->driver = NULL;
785                 dev_set_drvdata(dev, NULL);
786                 if (dev->pm_domain && dev->pm_domain->dismiss)
787                         dev->pm_domain->dismiss(dev);
788                 pm_runtime_reinit(dev);
789 
790                 klist_remove(&dev->p->knode_driver);
791                 device_pm_check_callbacks(dev);
792                 if (dev->bus)
793                         blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
794                                                      BUS_NOTIFY_UNBOUND_DRIVER,
795                                                      dev);
796         }
797 }
798 
799 /**
800  * device_release_driver - manually detach device from driver.
801  * @dev: device.
802  *
803  * Manually detach device from driver.
804  * When called for a USB interface, @dev->parent lock must be held.
805  */
806 void device_release_driver(struct device *dev)
807 {
808         /*
809          * If anyone calls device_release_driver() recursively from
810          * within their ->remove callback for the same device, they
811          * will deadlock right here.
812          */
813         device_lock(dev);
814         __device_release_driver(dev);
815         device_unlock(dev);
816 }
817 EXPORT_SYMBOL_GPL(device_release_driver);
818 
819 /**
820  * driver_detach - detach driver from all devices it controls.
821  * @drv: driver.
822  */
823 void driver_detach(struct device_driver *drv)
824 {
825         struct device_private *dev_prv;
826         struct device *dev;
827 
828         for (;;) {
829                 spin_lock(&drv->p->klist_devices.k_lock);
830                 if (list_empty(&drv->p->klist_devices.k_list)) {
831                         spin_unlock(&drv->p->klist_devices.k_lock);
832                         break;
833                 }
834                 dev_prv = list_entry(drv->p->klist_devices.k_list.prev,
835                                      struct device_private,
836                                      knode_driver.n_node);
837                 dev = dev_prv->device;
838                 get_device(dev);
839                 spin_unlock(&drv->p->klist_devices.k_lock);
840 
841                 if (dev->parent)        /* Needed for USB */
842                         device_lock(dev->parent);
843                 device_lock(dev);
844                 if (dev->driver == drv)
845                         __device_release_driver(dev);
846                 device_unlock(dev);
847                 if (dev->parent)
848                         device_unlock(dev->parent);
849                 put_device(dev);
850         }
851 }
852 

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