Merge tag 'driver-core-4.15-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git...
[muen/linux.git] / 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/dma-mapping.h>
23 #include <linux/init.h>
24 #include <linux/module.h>
25 #include <linux/kthread.h>
26 #include <linux/wait.h>
27 #include <linux/async.h>
28 #include <linux/pm_runtime.h>
29 #include <linux/pinctrl/devinfo.h>
30
31 #include "base.h"
32 #include "power/power.h"
33
34 /*
35  * Deferred Probe infrastructure.
36  *
37  * Sometimes driver probe order matters, but the kernel doesn't always have
38  * dependency information which means some drivers will get probed before a
39  * resource it depends on is available.  For example, an SDHCI driver may
40  * first need a GPIO line from an i2c GPIO controller before it can be
41  * initialized.  If a required resource is not available yet, a driver can
42  * request probing to be deferred by returning -EPROBE_DEFER from its probe hook
43  *
44  * Deferred probe maintains two lists of devices, a pending list and an active
45  * list.  A driver returning -EPROBE_DEFER causes the device to be added to the
46  * pending list.  A successful driver probe will trigger moving all devices
47  * from the pending to the active list so that the workqueue will eventually
48  * retry them.
49  *
50  * The deferred_probe_mutex must be held any time the deferred_probe_*_list
51  * of the (struct device*)->p->deferred_probe pointers are manipulated
52  */
53 static DEFINE_MUTEX(deferred_probe_mutex);
54 static LIST_HEAD(deferred_probe_pending_list);
55 static LIST_HEAD(deferred_probe_active_list);
56 static atomic_t deferred_trigger_count = ATOMIC_INIT(0);
57 static bool initcalls_done;
58
59 /*
60  * In some cases, like suspend to RAM or hibernation, It might be reasonable
61  * to prohibit probing of devices as it could be unsafe.
62  * Once defer_all_probes is true all drivers probes will be forcibly deferred.
63  */
64 static bool defer_all_probes;
65
66 /*
67  * For initcall_debug, show the deferred probes executed in late_initcall
68  * processing.
69  */
70 static void deferred_probe_debug(struct device *dev)
71 {
72         ktime_t calltime, delta, rettime;
73         unsigned long long duration;
74
75         printk(KERN_DEBUG "deferred probe %s @ %i\n", dev_name(dev),
76                task_pid_nr(current));
77         calltime = ktime_get();
78         bus_probe_device(dev);
79         rettime = ktime_get();
80         delta = ktime_sub(rettime, calltime);
81         duration = (unsigned long long) ktime_to_ns(delta) >> 10;
82         printk(KERN_DEBUG "deferred probe %s returned after %lld usecs\n",
83                dev_name(dev), duration);
84 }
85
86 /*
87  * deferred_probe_work_func() - Retry probing devices in the active list.
88  */
89 static void deferred_probe_work_func(struct work_struct *work)
90 {
91         struct device *dev;
92         struct device_private *private;
93         /*
94          * This block processes every device in the deferred 'active' list.
95          * Each device is removed from the active list and passed to
96          * bus_probe_device() to re-attempt the probe.  The loop continues
97          * until every device in the active list is removed and retried.
98          *
99          * Note: Once the device is removed from the list and the mutex is
100          * released, it is possible for the device get freed by another thread
101          * and cause a illegal pointer dereference.  This code uses
102          * get/put_device() to ensure the device structure cannot disappear
103          * from under our feet.
104          */
105         mutex_lock(&deferred_probe_mutex);
106         while (!list_empty(&deferred_probe_active_list)) {
107                 private = list_first_entry(&deferred_probe_active_list,
108                                         typeof(*dev->p), deferred_probe);
109                 dev = private->device;
110                 list_del_init(&private->deferred_probe);
111
112                 get_device(dev);
113
114                 /*
115                  * Drop the mutex while probing each device; the probe path may
116                  * manipulate the deferred list
117                  */
118                 mutex_unlock(&deferred_probe_mutex);
119
120                 /*
121                  * Force the device to the end of the dpm_list since
122                  * the PM code assumes that the order we add things to
123                  * the list is a good order for suspend but deferred
124                  * probe makes that very unsafe.
125                  */
126                 device_pm_lock();
127                 device_pm_move_last(dev);
128                 device_pm_unlock();
129
130                 dev_dbg(dev, "Retrying from deferred list\n");
131                 if (initcall_debug && !initcalls_done)
132                         deferred_probe_debug(dev);
133                 else
134                         bus_probe_device(dev);
135
136                 mutex_lock(&deferred_probe_mutex);
137
138                 put_device(dev);
139         }
140         mutex_unlock(&deferred_probe_mutex);
141 }
142 static DECLARE_WORK(deferred_probe_work, deferred_probe_work_func);
143
144 static void driver_deferred_probe_add(struct device *dev)
145 {
146         mutex_lock(&deferred_probe_mutex);
147         if (list_empty(&dev->p->deferred_probe)) {
148                 dev_dbg(dev, "Added to deferred list\n");
149                 list_add_tail(&dev->p->deferred_probe, &deferred_probe_pending_list);
150         }
151         mutex_unlock(&deferred_probe_mutex);
152 }
153
154 void driver_deferred_probe_del(struct device *dev)
155 {
156         mutex_lock(&deferred_probe_mutex);
157         if (!list_empty(&dev->p->deferred_probe)) {
158                 dev_dbg(dev, "Removed from deferred list\n");
159                 list_del_init(&dev->p->deferred_probe);
160         }
161         mutex_unlock(&deferred_probe_mutex);
162 }
163
164 static bool driver_deferred_probe_enable = false;
165 /**
166  * driver_deferred_probe_trigger() - Kick off re-probing deferred devices
167  *
168  * This functions moves all devices from the pending list to the active
169  * list and schedules the deferred probe workqueue to process them.  It
170  * should be called anytime a driver is successfully bound to a device.
171  *
172  * Note, there is a race condition in multi-threaded probe. In the case where
173  * more than one device is probing at the same time, it is possible for one
174  * probe to complete successfully while another is about to defer. If the second
175  * depends on the first, then it will get put on the pending list after the
176  * trigger event has already occurred and will be stuck there.
177  *
178  * The atomic 'deferred_trigger_count' is used to determine if a successful
179  * trigger has occurred in the midst of probing a driver. If the trigger count
180  * changes in the midst of a probe, then deferred processing should be triggered
181  * again.
182  */
183 static void driver_deferred_probe_trigger(void)
184 {
185         if (!driver_deferred_probe_enable)
186                 return;
187
188         /*
189          * A successful probe means that all the devices in the pending list
190          * should be triggered to be reprobed.  Move all the deferred devices
191          * into the active list so they can be retried by the workqueue
192          */
193         mutex_lock(&deferred_probe_mutex);
194         atomic_inc(&deferred_trigger_count);
195         list_splice_tail_init(&deferred_probe_pending_list,
196                               &deferred_probe_active_list);
197         mutex_unlock(&deferred_probe_mutex);
198
199         /*
200          * Kick the re-probe thread.  It may already be scheduled, but it is
201          * safe to kick it again.
202          */
203         schedule_work(&deferred_probe_work);
204 }
205
206 /**
207  * device_block_probing() - Block/defere device's probes
208  *
209  *      It will disable probing of devices and defer their probes instead.
210  */
211 void device_block_probing(void)
212 {
213         defer_all_probes = true;
214         /* sync with probes to avoid races. */
215         wait_for_device_probe();
216 }
217
218 /**
219  * device_unblock_probing() - Unblock/enable device's probes
220  *
221  *      It will restore normal behavior and trigger re-probing of deferred
222  * devices.
223  */
224 void device_unblock_probing(void)
225 {
226         defer_all_probes = false;
227         driver_deferred_probe_trigger();
228 }
229
230 /**
231  * deferred_probe_initcall() - Enable probing of deferred devices
232  *
233  * We don't want to get in the way when the bulk of drivers are getting probed.
234  * Instead, this initcall makes sure that deferred probing is delayed until
235  * late_initcall time.
236  */
237 static int deferred_probe_initcall(void)
238 {
239         driver_deferred_probe_enable = true;
240         driver_deferred_probe_trigger();
241         /* Sort as many dependencies as possible before exiting initcalls */
242         flush_work(&deferred_probe_work);
243         initcalls_done = true;
244         return 0;
245 }
246 late_initcall(deferred_probe_initcall);
247
248 /**
249  * device_is_bound() - Check if device is bound to a driver
250  * @dev: device to check
251  *
252  * Returns true if passed device has already finished probing successfully
253  * against a driver.
254  *
255  * This function must be called with the device lock held.
256  */
257 bool device_is_bound(struct device *dev)
258 {
259         return dev->p && klist_node_attached(&dev->p->knode_driver);
260 }
261
262 static void driver_bound(struct device *dev)
263 {
264         if (device_is_bound(dev)) {
265                 printk(KERN_WARNING "%s: device %s already bound\n",
266                         __func__, kobject_name(&dev->kobj));
267                 return;
268         }
269
270         pr_debug("driver: '%s': %s: bound to device '%s'\n", dev->driver->name,
271                  __func__, dev_name(dev));
272
273         klist_add_tail(&dev->p->knode_driver, &dev->driver->p->klist_devices);
274         device_links_driver_bound(dev);
275
276         device_pm_check_callbacks(dev);
277
278         /*
279          * Make sure the device is no longer in one of the deferred lists and
280          * kick off retrying all pending devices
281          */
282         driver_deferred_probe_del(dev);
283         driver_deferred_probe_trigger();
284
285         if (dev->bus)
286                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
287                                              BUS_NOTIFY_BOUND_DRIVER, dev);
288
289         kobject_uevent(&dev->kobj, KOBJ_BIND);
290 }
291
292 static int driver_sysfs_add(struct device *dev)
293 {
294         int ret;
295
296         if (dev->bus)
297                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
298                                              BUS_NOTIFY_BIND_DRIVER, dev);
299
300         ret = sysfs_create_link(&dev->driver->p->kobj, &dev->kobj,
301                           kobject_name(&dev->kobj));
302         if (ret == 0) {
303                 ret = sysfs_create_link(&dev->kobj, &dev->driver->p->kobj,
304                                         "driver");
305                 if (ret)
306                         sysfs_remove_link(&dev->driver->p->kobj,
307                                         kobject_name(&dev->kobj));
308         }
309         return ret;
310 }
311
312 static void driver_sysfs_remove(struct device *dev)
313 {
314         struct device_driver *drv = dev->driver;
315
316         if (drv) {
317                 sysfs_remove_link(&drv->p->kobj, kobject_name(&dev->kobj));
318                 sysfs_remove_link(&dev->kobj, "driver");
319         }
320 }
321
322 /**
323  * device_bind_driver - bind a driver to one device.
324  * @dev: device.
325  *
326  * Allow manual attachment of a driver to a device.
327  * Caller must have already set @dev->driver.
328  *
329  * Note that this does not modify the bus reference count
330  * nor take the bus's rwsem. Please verify those are accounted
331  * for before calling this. (It is ok to call with no other effort
332  * from a driver's probe() method.)
333  *
334  * This function must be called with the device lock held.
335  */
336 int device_bind_driver(struct device *dev)
337 {
338         int ret;
339
340         ret = driver_sysfs_add(dev);
341         if (!ret)
342                 driver_bound(dev);
343         else if (dev->bus)
344                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
345                                              BUS_NOTIFY_DRIVER_NOT_BOUND, dev);
346         return ret;
347 }
348 EXPORT_SYMBOL_GPL(device_bind_driver);
349
350 static atomic_t probe_count = ATOMIC_INIT(0);
351 static DECLARE_WAIT_QUEUE_HEAD(probe_waitqueue);
352
353 static void driver_deferred_probe_add_trigger(struct device *dev,
354                                               int local_trigger_count)
355 {
356         driver_deferred_probe_add(dev);
357         /* Did a trigger occur while probing? Need to re-trigger if yes */
358         if (local_trigger_count != atomic_read(&deferred_trigger_count))
359                 driver_deferred_probe_trigger();
360 }
361
362 static int really_probe(struct device *dev, struct device_driver *drv)
363 {
364         int ret = -EPROBE_DEFER;
365         int local_trigger_count = atomic_read(&deferred_trigger_count);
366         bool test_remove = IS_ENABLED(CONFIG_DEBUG_TEST_DRIVER_REMOVE) &&
367                            !drv->suppress_bind_attrs;
368
369         if (defer_all_probes) {
370                 /*
371                  * Value of defer_all_probes can be set only by
372                  * device_defer_all_probes_enable() which, in turn, will call
373                  * wait_for_device_probe() right after that to avoid any races.
374                  */
375                 dev_dbg(dev, "Driver %s force probe deferral\n", drv->name);
376                 driver_deferred_probe_add(dev);
377                 return ret;
378         }
379
380         ret = device_links_check_suppliers(dev);
381         if (ret == -EPROBE_DEFER)
382                 driver_deferred_probe_add_trigger(dev, local_trigger_count);
383         if (ret)
384                 return ret;
385
386         atomic_inc(&probe_count);
387         pr_debug("bus: '%s': %s: probing driver %s with device %s\n",
388                  drv->bus->name, __func__, drv->name, dev_name(dev));
389         WARN_ON(!list_empty(&dev->devres_head));
390
391 re_probe:
392         dev->driver = drv;
393
394         /* If using pinctrl, bind pins now before probing */
395         ret = pinctrl_bind_pins(dev);
396         if (ret)
397                 goto pinctrl_bind_failed;
398
399         ret = dma_configure(dev);
400         if (ret)
401                 goto dma_failed;
402
403         if (driver_sysfs_add(dev)) {
404                 printk(KERN_ERR "%s: driver_sysfs_add(%s) failed\n",
405                         __func__, dev_name(dev));
406                 goto probe_failed;
407         }
408
409         if (dev->pm_domain && dev->pm_domain->activate) {
410                 ret = dev->pm_domain->activate(dev);
411                 if (ret)
412                         goto probe_failed;
413         }
414
415         /*
416          * Ensure devices are listed in devices_kset in correct order
417          * It's important to move Dev to the end of devices_kset before
418          * calling .probe, because it could be recursive and parent Dev
419          * should always go first
420          */
421         devices_kset_move_last(dev);
422
423         if (dev->bus->probe) {
424                 ret = dev->bus->probe(dev);
425                 if (ret)
426                         goto probe_failed;
427         } else if (drv->probe) {
428                 ret = drv->probe(dev);
429                 if (ret)
430                         goto probe_failed;
431         }
432
433         if (test_remove) {
434                 test_remove = false;
435
436                 if (dev->bus->remove)
437                         dev->bus->remove(dev);
438                 else if (drv->remove)
439                         drv->remove(dev);
440
441                 devres_release_all(dev);
442                 driver_sysfs_remove(dev);
443                 dev->driver = NULL;
444                 dev_set_drvdata(dev, NULL);
445                 if (dev->pm_domain && dev->pm_domain->dismiss)
446                         dev->pm_domain->dismiss(dev);
447                 pm_runtime_reinit(dev);
448
449                 goto re_probe;
450         }
451
452         pinctrl_init_done(dev);
453
454         if (dev->pm_domain && dev->pm_domain->sync)
455                 dev->pm_domain->sync(dev);
456
457         driver_bound(dev);
458         ret = 1;
459         pr_debug("bus: '%s': %s: bound device %s to driver %s\n",
460                  drv->bus->name, __func__, dev_name(dev), drv->name);
461         goto done;
462
463 probe_failed:
464         dma_deconfigure(dev);
465 dma_failed:
466         if (dev->bus)
467                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
468                                              BUS_NOTIFY_DRIVER_NOT_BOUND, dev);
469 pinctrl_bind_failed:
470         device_links_no_driver(dev);
471         devres_release_all(dev);
472         driver_sysfs_remove(dev);
473         dev->driver = NULL;
474         dev_set_drvdata(dev, NULL);
475         if (dev->pm_domain && dev->pm_domain->dismiss)
476                 dev->pm_domain->dismiss(dev);
477         pm_runtime_reinit(dev);
478         dev_pm_set_driver_flags(dev, 0);
479
480         switch (ret) {
481         case -EPROBE_DEFER:
482                 /* Driver requested deferred probing */
483                 dev_dbg(dev, "Driver %s requests probe deferral\n", drv->name);
484                 driver_deferred_probe_add_trigger(dev, local_trigger_count);
485                 break;
486         case -ENODEV:
487         case -ENXIO:
488                 pr_debug("%s: probe of %s rejects match %d\n",
489                          drv->name, dev_name(dev), ret);
490                 break;
491         default:
492                 /* driver matched but the probe failed */
493                 printk(KERN_WARNING
494                        "%s: probe of %s failed with error %d\n",
495                        drv->name, dev_name(dev), ret);
496         }
497         /*
498          * Ignore errors returned by ->probe so that the next driver can try
499          * its luck.
500          */
501         ret = 0;
502 done:
503         atomic_dec(&probe_count);
504         wake_up(&probe_waitqueue);
505         return ret;
506 }
507
508 /**
509  * driver_probe_done
510  * Determine if the probe sequence is finished or not.
511  *
512  * Should somehow figure out how to use a semaphore, not an atomic variable...
513  */
514 int driver_probe_done(void)
515 {
516         pr_debug("%s: probe_count = %d\n", __func__,
517                  atomic_read(&probe_count));
518         if (atomic_read(&probe_count))
519                 return -EBUSY;
520         return 0;
521 }
522
523 /**
524  * wait_for_device_probe
525  * Wait for device probing to be completed.
526  */
527 void wait_for_device_probe(void)
528 {
529         /* wait for the deferred probe workqueue to finish */
530         flush_work(&deferred_probe_work);
531
532         /* wait for the known devices to complete their probing */
533         wait_event(probe_waitqueue, atomic_read(&probe_count) == 0);
534         async_synchronize_full();
535 }
536 EXPORT_SYMBOL_GPL(wait_for_device_probe);
537
538 /**
539  * driver_probe_device - attempt to bind device & driver together
540  * @drv: driver to bind a device to
541  * @dev: device to try to bind to the driver
542  *
543  * This function returns -ENODEV if the device is not registered,
544  * 1 if the device is bound successfully and 0 otherwise.
545  *
546  * This function must be called with @dev lock held.  When called for a
547  * USB interface, @dev->parent lock must be held as well.
548  *
549  * If the device has a parent, runtime-resume the parent before driver probing.
550  */
551 int driver_probe_device(struct device_driver *drv, struct device *dev)
552 {
553         int ret = 0;
554
555         if (!device_is_registered(dev))
556                 return -ENODEV;
557
558         pr_debug("bus: '%s': %s: matched device %s with driver %s\n",
559                  drv->bus->name, __func__, dev_name(dev), drv->name);
560
561         pm_runtime_get_suppliers(dev);
562         if (dev->parent)
563                 pm_runtime_get_sync(dev->parent);
564
565         pm_runtime_barrier(dev);
566         ret = really_probe(dev, drv);
567         pm_request_idle(dev);
568
569         if (dev->parent)
570                 pm_runtime_put(dev->parent);
571
572         pm_runtime_put_suppliers(dev);
573         return ret;
574 }
575
576 bool driver_allows_async_probing(struct device_driver *drv)
577 {
578         switch (drv->probe_type) {
579         case PROBE_PREFER_ASYNCHRONOUS:
580                 return true;
581
582         case PROBE_FORCE_SYNCHRONOUS:
583                 return false;
584
585         default:
586                 if (module_requested_async_probing(drv->owner))
587                         return true;
588
589                 return false;
590         }
591 }
592
593 struct device_attach_data {
594         struct device *dev;
595
596         /*
597          * Indicates whether we are are considering asynchronous probing or
598          * not. Only initial binding after device or driver registration
599          * (including deferral processing) may be done asynchronously, the
600          * rest is always synchronous, as we expect it is being done by
601          * request from userspace.
602          */
603         bool check_async;
604
605         /*
606          * Indicates if we are binding synchronous or asynchronous drivers.
607          * When asynchronous probing is enabled we'll execute 2 passes
608          * over drivers: first pass doing synchronous probing and second
609          * doing asynchronous probing (if synchronous did not succeed -
610          * most likely because there was no driver requiring synchronous
611          * probing - and we found asynchronous driver during first pass).
612          * The 2 passes are done because we can't shoot asynchronous
613          * probe for given device and driver from bus_for_each_drv() since
614          * driver pointer is not guaranteed to stay valid once
615          * bus_for_each_drv() iterates to the next driver on the bus.
616          */
617         bool want_async;
618
619         /*
620          * We'll set have_async to 'true' if, while scanning for matching
621          * driver, we'll encounter one that requests asynchronous probing.
622          */
623         bool have_async;
624 };
625
626 static int __device_attach_driver(struct device_driver *drv, void *_data)
627 {
628         struct device_attach_data *data = _data;
629         struct device *dev = data->dev;
630         bool async_allowed;
631         int ret;
632
633         /*
634          * Check if device has already been claimed. This may
635          * happen with driver loading, device discovery/registration,
636          * and deferred probe processing happens all at once with
637          * multiple threads.
638          */
639         if (dev->driver)
640                 return -EBUSY;
641
642         ret = driver_match_device(drv, dev);
643         if (ret == 0) {
644                 /* no match */
645                 return 0;
646         } else if (ret == -EPROBE_DEFER) {
647                 dev_dbg(dev, "Device match requests probe deferral\n");
648                 driver_deferred_probe_add(dev);
649         } else if (ret < 0) {
650                 dev_dbg(dev, "Bus failed to match device: %d", ret);
651                 return ret;
652         } /* ret > 0 means positive match */
653
654         async_allowed = driver_allows_async_probing(drv);
655
656         if (async_allowed)
657                 data->have_async = true;
658
659         if (data->check_async && async_allowed != data->want_async)
660                 return 0;
661
662         return driver_probe_device(drv, dev);
663 }
664
665 static void __device_attach_async_helper(void *_dev, async_cookie_t cookie)
666 {
667         struct device *dev = _dev;
668         struct device_attach_data data = {
669                 .dev            = dev,
670                 .check_async    = true,
671                 .want_async     = true,
672         };
673
674         device_lock(dev);
675
676         if (dev->parent)
677                 pm_runtime_get_sync(dev->parent);
678
679         bus_for_each_drv(dev->bus, NULL, &data, __device_attach_driver);
680         dev_dbg(dev, "async probe completed\n");
681
682         pm_request_idle(dev);
683
684         if (dev->parent)
685                 pm_runtime_put(dev->parent);
686
687         device_unlock(dev);
688
689         put_device(dev);
690 }
691
692 static int __device_attach(struct device *dev, bool allow_async)
693 {
694         int ret = 0;
695
696         device_lock(dev);
697         if (dev->driver) {
698                 if (device_is_bound(dev)) {
699                         ret = 1;
700                         goto out_unlock;
701                 }
702                 ret = device_bind_driver(dev);
703                 if (ret == 0)
704                         ret = 1;
705                 else {
706                         dev->driver = NULL;
707                         ret = 0;
708                 }
709         } else {
710                 struct device_attach_data data = {
711                         .dev = dev,
712                         .check_async = allow_async,
713                         .want_async = false,
714                 };
715
716                 if (dev->parent)
717                         pm_runtime_get_sync(dev->parent);
718
719                 ret = bus_for_each_drv(dev->bus, NULL, &data,
720                                         __device_attach_driver);
721                 if (!ret && allow_async && data.have_async) {
722                         /*
723                          * If we could not find appropriate driver
724                          * synchronously and we are allowed to do
725                          * async probes and there are drivers that
726                          * want to probe asynchronously, we'll
727                          * try them.
728                          */
729                         dev_dbg(dev, "scheduling asynchronous probe\n");
730                         get_device(dev);
731                         async_schedule(__device_attach_async_helper, dev);
732                 } else {
733                         pm_request_idle(dev);
734                 }
735
736                 if (dev->parent)
737                         pm_runtime_put(dev->parent);
738         }
739 out_unlock:
740         device_unlock(dev);
741         return ret;
742 }
743
744 /**
745  * device_attach - try to attach device to a driver.
746  * @dev: device.
747  *
748  * Walk the list of drivers that the bus has and call
749  * driver_probe_device() for each pair. If a compatible
750  * pair is found, break out and return.
751  *
752  * Returns 1 if the device was bound to a driver;
753  * 0 if no matching driver was found;
754  * -ENODEV if the device is not registered.
755  *
756  * When called for a USB interface, @dev->parent lock must be held.
757  */
758 int device_attach(struct device *dev)
759 {
760         return __device_attach(dev, false);
761 }
762 EXPORT_SYMBOL_GPL(device_attach);
763
764 void device_initial_probe(struct device *dev)
765 {
766         __device_attach(dev, true);
767 }
768
769 static int __driver_attach(struct device *dev, void *data)
770 {
771         struct device_driver *drv = data;
772         int ret;
773
774         /*
775          * Lock device and try to bind to it. We drop the error
776          * here and always return 0, because we need to keep trying
777          * to bind to devices and some drivers will return an error
778          * simply if it didn't support the device.
779          *
780          * driver_probe_device() will spit a warning if there
781          * is an error.
782          */
783
784         ret = driver_match_device(drv, dev);
785         if (ret == 0) {
786                 /* no match */
787                 return 0;
788         } else if (ret == -EPROBE_DEFER) {
789                 dev_dbg(dev, "Device match requests probe deferral\n");
790                 driver_deferred_probe_add(dev);
791         } else if (ret < 0) {
792                 dev_dbg(dev, "Bus failed to match device: %d", ret);
793                 return ret;
794         } /* ret > 0 means positive match */
795
796         if (dev->parent)        /* Needed for USB */
797                 device_lock(dev->parent);
798         device_lock(dev);
799         if (!dev->driver)
800                 driver_probe_device(drv, dev);
801         device_unlock(dev);
802         if (dev->parent)
803                 device_unlock(dev->parent);
804
805         return 0;
806 }
807
808 /**
809  * driver_attach - try to bind driver to devices.
810  * @drv: driver.
811  *
812  * Walk the list of devices that the bus has on it and try to
813  * match the driver with each one.  If driver_probe_device()
814  * returns 0 and the @dev->driver is set, we've found a
815  * compatible pair.
816  */
817 int driver_attach(struct device_driver *drv)
818 {
819         return bus_for_each_dev(drv->bus, NULL, drv, __driver_attach);
820 }
821 EXPORT_SYMBOL_GPL(driver_attach);
822
823 /*
824  * __device_release_driver() must be called with @dev lock held.
825  * When called for a USB interface, @dev->parent lock must be held as well.
826  */
827 static void __device_release_driver(struct device *dev, struct device *parent)
828 {
829         struct device_driver *drv;
830
831         drv = dev->driver;
832         if (drv) {
833                 if (driver_allows_async_probing(drv))
834                         async_synchronize_full();
835
836                 while (device_links_busy(dev)) {
837                         device_unlock(dev);
838                         if (parent)
839                                 device_unlock(parent);
840
841                         device_links_unbind_consumers(dev);
842                         if (parent)
843                                 device_lock(parent);
844
845                         device_lock(dev);
846                         /*
847                          * A concurrent invocation of the same function might
848                          * have released the driver successfully while this one
849                          * was waiting, so check for that.
850                          */
851                         if (dev->driver != drv)
852                                 return;
853                 }
854
855                 pm_runtime_get_sync(dev);
856                 pm_runtime_clean_up_links(dev);
857
858                 driver_sysfs_remove(dev);
859
860                 if (dev->bus)
861                         blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
862                                                      BUS_NOTIFY_UNBIND_DRIVER,
863                                                      dev);
864
865                 pm_runtime_put_sync(dev);
866
867                 if (dev->bus && dev->bus->remove)
868                         dev->bus->remove(dev);
869                 else if (drv->remove)
870                         drv->remove(dev);
871
872                 device_links_driver_cleanup(dev);
873                 dma_deconfigure(dev);
874
875                 devres_release_all(dev);
876                 dev->driver = NULL;
877                 dev_set_drvdata(dev, NULL);
878                 if (dev->pm_domain && dev->pm_domain->dismiss)
879                         dev->pm_domain->dismiss(dev);
880                 pm_runtime_reinit(dev);
881                 dev_pm_set_driver_flags(dev, 0);
882
883                 klist_remove(&dev->p->knode_driver);
884                 device_pm_check_callbacks(dev);
885                 if (dev->bus)
886                         blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
887                                                      BUS_NOTIFY_UNBOUND_DRIVER,
888                                                      dev);
889
890                 kobject_uevent(&dev->kobj, KOBJ_UNBIND);
891         }
892 }
893
894 void device_release_driver_internal(struct device *dev,
895                                     struct device_driver *drv,
896                                     struct device *parent)
897 {
898         if (parent)
899                 device_lock(parent);
900
901         device_lock(dev);
902         if (!drv || drv == dev->driver)
903                 __device_release_driver(dev, parent);
904
905         device_unlock(dev);
906         if (parent)
907                 device_unlock(parent);
908 }
909
910 /**
911  * device_release_driver - manually detach device from driver.
912  * @dev: device.
913  *
914  * Manually detach device from driver.
915  * When called for a USB interface, @dev->parent lock must be held.
916  *
917  * If this function is to be called with @dev->parent lock held, ensure that
918  * the device's consumers are unbound in advance or that their locks can be
919  * acquired under the @dev->parent lock.
920  */
921 void device_release_driver(struct device *dev)
922 {
923         /*
924          * If anyone calls device_release_driver() recursively from
925          * within their ->remove callback for the same device, they
926          * will deadlock right here.
927          */
928         device_release_driver_internal(dev, NULL, NULL);
929 }
930 EXPORT_SYMBOL_GPL(device_release_driver);
931
932 /**
933  * driver_detach - detach driver from all devices it controls.
934  * @drv: driver.
935  */
936 void driver_detach(struct device_driver *drv)
937 {
938         struct device_private *dev_prv;
939         struct device *dev;
940
941         for (;;) {
942                 spin_lock(&drv->p->klist_devices.k_lock);
943                 if (list_empty(&drv->p->klist_devices.k_list)) {
944                         spin_unlock(&drv->p->klist_devices.k_lock);
945                         break;
946                 }
947                 dev_prv = list_entry(drv->p->klist_devices.k_list.prev,
948                                      struct device_private,
949                                      knode_driver.n_node);
950                 dev = dev_prv->device;
951                 get_device(dev);
952                 spin_unlock(&drv->p->klist_devices.k_lock);
953                 device_release_driver_internal(dev, drv, dev->parent);
954                 put_device(dev);
955         }
956 }