ad44b40fe2847d219e50a5d51d799f2541b5d6d0
[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 int really_probe(struct device *dev, struct device_driver *drv)
354 {
355         int ret = -EPROBE_DEFER;
356         int local_trigger_count = atomic_read(&deferred_trigger_count);
357         bool test_remove = IS_ENABLED(CONFIG_DEBUG_TEST_DRIVER_REMOVE) &&
358                            !drv->suppress_bind_attrs;
359
360         if (defer_all_probes) {
361                 /*
362                  * Value of defer_all_probes can be set only by
363                  * device_defer_all_probes_enable() which, in turn, will call
364                  * wait_for_device_probe() right after that to avoid any races.
365                  */
366                 dev_dbg(dev, "Driver %s force probe deferral\n", drv->name);
367                 driver_deferred_probe_add(dev);
368                 return ret;
369         }
370
371         ret = device_links_check_suppliers(dev);
372         if (ret)
373                 return ret;
374
375         atomic_inc(&probe_count);
376         pr_debug("bus: '%s': %s: probing driver %s with device %s\n",
377                  drv->bus->name, __func__, drv->name, dev_name(dev));
378         WARN_ON(!list_empty(&dev->devres_head));
379
380 re_probe:
381         dev->driver = drv;
382
383         /* If using pinctrl, bind pins now before probing */
384         ret = pinctrl_bind_pins(dev);
385         if (ret)
386                 goto pinctrl_bind_failed;
387
388         ret = dma_configure(dev);
389         if (ret)
390                 goto dma_failed;
391
392         if (driver_sysfs_add(dev)) {
393                 printk(KERN_ERR "%s: driver_sysfs_add(%s) failed\n",
394                         __func__, dev_name(dev));
395                 goto probe_failed;
396         }
397
398         if (dev->pm_domain && dev->pm_domain->activate) {
399                 ret = dev->pm_domain->activate(dev);
400                 if (ret)
401                         goto probe_failed;
402         }
403
404         /*
405          * Ensure devices are listed in devices_kset in correct order
406          * It's important to move Dev to the end of devices_kset before
407          * calling .probe, because it could be recursive and parent Dev
408          * should always go first
409          */
410         devices_kset_move_last(dev);
411
412         if (dev->bus->probe) {
413                 ret = dev->bus->probe(dev);
414                 if (ret)
415                         goto probe_failed;
416         } else if (drv->probe) {
417                 ret = drv->probe(dev);
418                 if (ret)
419                         goto probe_failed;
420         }
421
422         if (test_remove) {
423                 test_remove = false;
424
425                 if (dev->bus->remove)
426                         dev->bus->remove(dev);
427                 else if (drv->remove)
428                         drv->remove(dev);
429
430                 devres_release_all(dev);
431                 driver_sysfs_remove(dev);
432                 dev->driver = NULL;
433                 dev_set_drvdata(dev, NULL);
434                 if (dev->pm_domain && dev->pm_domain->dismiss)
435                         dev->pm_domain->dismiss(dev);
436                 pm_runtime_reinit(dev);
437
438                 goto re_probe;
439         }
440
441         pinctrl_init_done(dev);
442
443         if (dev->pm_domain && dev->pm_domain->sync)
444                 dev->pm_domain->sync(dev);
445
446         driver_bound(dev);
447         ret = 1;
448         pr_debug("bus: '%s': %s: bound device %s to driver %s\n",
449                  drv->bus->name, __func__, dev_name(dev), drv->name);
450         goto done;
451
452 probe_failed:
453         dma_deconfigure(dev);
454 dma_failed:
455         if (dev->bus)
456                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
457                                              BUS_NOTIFY_DRIVER_NOT_BOUND, dev);
458 pinctrl_bind_failed:
459         device_links_no_driver(dev);
460         devres_release_all(dev);
461         driver_sysfs_remove(dev);
462         dev->driver = NULL;
463         dev_set_drvdata(dev, NULL);
464         if (dev->pm_domain && dev->pm_domain->dismiss)
465                 dev->pm_domain->dismiss(dev);
466         pm_runtime_reinit(dev);
467
468         switch (ret) {
469         case -EPROBE_DEFER:
470                 /* Driver requested deferred probing */
471                 dev_dbg(dev, "Driver %s requests probe deferral\n", drv->name);
472                 driver_deferred_probe_add(dev);
473                 /* Did a trigger occur while probing? Need to re-trigger if yes */
474                 if (local_trigger_count != atomic_read(&deferred_trigger_count))
475                         driver_deferred_probe_trigger();
476                 break;
477         case -ENODEV:
478         case -ENXIO:
479                 pr_debug("%s: probe of %s rejects match %d\n",
480                          drv->name, dev_name(dev), ret);
481                 break;
482         default:
483                 /* driver matched but the probe failed */
484                 printk(KERN_WARNING
485                        "%s: probe of %s failed with error %d\n",
486                        drv->name, dev_name(dev), ret);
487         }
488         /*
489          * Ignore errors returned by ->probe so that the next driver can try
490          * its luck.
491          */
492         ret = 0;
493 done:
494         atomic_dec(&probe_count);
495         wake_up(&probe_waitqueue);
496         return ret;
497 }
498
499 /**
500  * driver_probe_done
501  * Determine if the probe sequence is finished or not.
502  *
503  * Should somehow figure out how to use a semaphore, not an atomic variable...
504  */
505 int driver_probe_done(void)
506 {
507         pr_debug("%s: probe_count = %d\n", __func__,
508                  atomic_read(&probe_count));
509         if (atomic_read(&probe_count))
510                 return -EBUSY;
511         return 0;
512 }
513
514 /**
515  * wait_for_device_probe
516  * Wait for device probing to be completed.
517  */
518 void wait_for_device_probe(void)
519 {
520         /* wait for the deferred probe workqueue to finish */
521         flush_work(&deferred_probe_work);
522
523         /* wait for the known devices to complete their probing */
524         wait_event(probe_waitqueue, atomic_read(&probe_count) == 0);
525         async_synchronize_full();
526 }
527 EXPORT_SYMBOL_GPL(wait_for_device_probe);
528
529 /**
530  * driver_probe_device - attempt to bind device & driver together
531  * @drv: driver to bind a device to
532  * @dev: device to try to bind to the driver
533  *
534  * This function returns -ENODEV if the device is not registered,
535  * 1 if the device is bound successfully and 0 otherwise.
536  *
537  * This function must be called with @dev lock held.  When called for a
538  * USB interface, @dev->parent lock must be held as well.
539  *
540  * If the device has a parent, runtime-resume the parent before driver probing.
541  */
542 int driver_probe_device(struct device_driver *drv, struct device *dev)
543 {
544         int ret = 0;
545
546         if (!device_is_registered(dev))
547                 return -ENODEV;
548
549         pr_debug("bus: '%s': %s: matched device %s with driver %s\n",
550                  drv->bus->name, __func__, dev_name(dev), drv->name);
551
552         pm_runtime_get_suppliers(dev);
553         if (dev->parent)
554                 pm_runtime_get_sync(dev->parent);
555
556         pm_runtime_barrier(dev);
557         ret = really_probe(dev, drv);
558         pm_request_idle(dev);
559
560         if (dev->parent)
561                 pm_runtime_put(dev->parent);
562
563         pm_runtime_put_suppliers(dev);
564         return ret;
565 }
566
567 bool driver_allows_async_probing(struct device_driver *drv)
568 {
569         switch (drv->probe_type) {
570         case PROBE_PREFER_ASYNCHRONOUS:
571                 return true;
572
573         case PROBE_FORCE_SYNCHRONOUS:
574                 return false;
575
576         default:
577                 if (module_requested_async_probing(drv->owner))
578                         return true;
579
580                 return false;
581         }
582 }
583
584 struct device_attach_data {
585         struct device *dev;
586
587         /*
588          * Indicates whether we are are considering asynchronous probing or
589          * not. Only initial binding after device or driver registration
590          * (including deferral processing) may be done asynchronously, the
591          * rest is always synchronous, as we expect it is being done by
592          * request from userspace.
593          */
594         bool check_async;
595
596         /*
597          * Indicates if we are binding synchronous or asynchronous drivers.
598          * When asynchronous probing is enabled we'll execute 2 passes
599          * over drivers: first pass doing synchronous probing and second
600          * doing asynchronous probing (if synchronous did not succeed -
601          * most likely because there was no driver requiring synchronous
602          * probing - and we found asynchronous driver during first pass).
603          * The 2 passes are done because we can't shoot asynchronous
604          * probe for given device and driver from bus_for_each_drv() since
605          * driver pointer is not guaranteed to stay valid once
606          * bus_for_each_drv() iterates to the next driver on the bus.
607          */
608         bool want_async;
609
610         /*
611          * We'll set have_async to 'true' if, while scanning for matching
612          * driver, we'll encounter one that requests asynchronous probing.
613          */
614         bool have_async;
615 };
616
617 static int __device_attach_driver(struct device_driver *drv, void *_data)
618 {
619         struct device_attach_data *data = _data;
620         struct device *dev = data->dev;
621         bool async_allowed;
622         int ret;
623
624         /*
625          * Check if device has already been claimed. This may
626          * happen with driver loading, device discovery/registration,
627          * and deferred probe processing happens all at once with
628          * multiple threads.
629          */
630         if (dev->driver)
631                 return -EBUSY;
632
633         ret = driver_match_device(drv, dev);
634         if (ret == 0) {
635                 /* no match */
636                 return 0;
637         } else if (ret == -EPROBE_DEFER) {
638                 dev_dbg(dev, "Device match requests probe deferral\n");
639                 driver_deferred_probe_add(dev);
640         } else if (ret < 0) {
641                 dev_dbg(dev, "Bus failed to match device: %d", ret);
642                 return ret;
643         } /* ret > 0 means positive match */
644
645         async_allowed = driver_allows_async_probing(drv);
646
647         if (async_allowed)
648                 data->have_async = true;
649
650         if (data->check_async && async_allowed != data->want_async)
651                 return 0;
652
653         return driver_probe_device(drv, dev);
654 }
655
656 static void __device_attach_async_helper(void *_dev, async_cookie_t cookie)
657 {
658         struct device *dev = _dev;
659         struct device_attach_data data = {
660                 .dev            = dev,
661                 .check_async    = true,
662                 .want_async     = true,
663         };
664
665         device_lock(dev);
666
667         if (dev->parent)
668                 pm_runtime_get_sync(dev->parent);
669
670         bus_for_each_drv(dev->bus, NULL, &data, __device_attach_driver);
671         dev_dbg(dev, "async probe completed\n");
672
673         pm_request_idle(dev);
674
675         if (dev->parent)
676                 pm_runtime_put(dev->parent);
677
678         device_unlock(dev);
679
680         put_device(dev);
681 }
682
683 static int __device_attach(struct device *dev, bool allow_async)
684 {
685         int ret = 0;
686
687         device_lock(dev);
688         if (dev->driver) {
689                 if (device_is_bound(dev)) {
690                         ret = 1;
691                         goto out_unlock;
692                 }
693                 ret = device_bind_driver(dev);
694                 if (ret == 0)
695                         ret = 1;
696                 else {
697                         dev->driver = NULL;
698                         ret = 0;
699                 }
700         } else {
701                 struct device_attach_data data = {
702                         .dev = dev,
703                         .check_async = allow_async,
704                         .want_async = false,
705                 };
706
707                 if (dev->parent)
708                         pm_runtime_get_sync(dev->parent);
709
710                 ret = bus_for_each_drv(dev->bus, NULL, &data,
711                                         __device_attach_driver);
712                 if (!ret && allow_async && data.have_async) {
713                         /*
714                          * If we could not find appropriate driver
715                          * synchronously and we are allowed to do
716                          * async probes and there are drivers that
717                          * want to probe asynchronously, we'll
718                          * try them.
719                          */
720                         dev_dbg(dev, "scheduling asynchronous probe\n");
721                         get_device(dev);
722                         async_schedule(__device_attach_async_helper, dev);
723                 } else {
724                         pm_request_idle(dev);
725                 }
726
727                 if (dev->parent)
728                         pm_runtime_put(dev->parent);
729         }
730 out_unlock:
731         device_unlock(dev);
732         return ret;
733 }
734
735 /**
736  * device_attach - try to attach device to a driver.
737  * @dev: device.
738  *
739  * Walk the list of drivers that the bus has and call
740  * driver_probe_device() for each pair. If a compatible
741  * pair is found, break out and return.
742  *
743  * Returns 1 if the device was bound to a driver;
744  * 0 if no matching driver was found;
745  * -ENODEV if the device is not registered.
746  *
747  * When called for a USB interface, @dev->parent lock must be held.
748  */
749 int device_attach(struct device *dev)
750 {
751         return __device_attach(dev, false);
752 }
753 EXPORT_SYMBOL_GPL(device_attach);
754
755 void device_initial_probe(struct device *dev)
756 {
757         __device_attach(dev, true);
758 }
759
760 static int __driver_attach(struct device *dev, void *data)
761 {
762         struct device_driver *drv = data;
763         int ret;
764
765         /*
766          * Lock device and try to bind to it. We drop the error
767          * here and always return 0, because we need to keep trying
768          * to bind to devices and some drivers will return an error
769          * simply if it didn't support the device.
770          *
771          * driver_probe_device() will spit a warning if there
772          * is an error.
773          */
774
775         ret = driver_match_device(drv, dev);
776         if (ret == 0) {
777                 /* no match */
778                 return 0;
779         } else if (ret == -EPROBE_DEFER) {
780                 dev_dbg(dev, "Device match requests probe deferral\n");
781                 driver_deferred_probe_add(dev);
782         } else if (ret < 0) {
783                 dev_dbg(dev, "Bus failed to match device: %d", ret);
784                 return ret;
785         } /* ret > 0 means positive match */
786
787         if (dev->parent)        /* Needed for USB */
788                 device_lock(dev->parent);
789         device_lock(dev);
790         if (!dev->driver)
791                 driver_probe_device(drv, dev);
792         device_unlock(dev);
793         if (dev->parent)
794                 device_unlock(dev->parent);
795
796         return 0;
797 }
798
799 /**
800  * driver_attach - try to bind driver to devices.
801  * @drv: driver.
802  *
803  * Walk the list of devices that the bus has on it and try to
804  * match the driver with each one.  If driver_probe_device()
805  * returns 0 and the @dev->driver is set, we've found a
806  * compatible pair.
807  */
808 int driver_attach(struct device_driver *drv)
809 {
810         return bus_for_each_dev(drv->bus, NULL, drv, __driver_attach);
811 }
812 EXPORT_SYMBOL_GPL(driver_attach);
813
814 /*
815  * __device_release_driver() must be called with @dev lock held.
816  * When called for a USB interface, @dev->parent lock must be held as well.
817  */
818 static void __device_release_driver(struct device *dev, struct device *parent)
819 {
820         struct device_driver *drv;
821
822         drv = dev->driver;
823         if (drv) {
824                 if (driver_allows_async_probing(drv))
825                         async_synchronize_full();
826
827                 while (device_links_busy(dev)) {
828                         device_unlock(dev);
829                         if (parent)
830                                 device_unlock(parent);
831
832                         device_links_unbind_consumers(dev);
833                         if (parent)
834                                 device_lock(parent);
835
836                         device_lock(dev);
837                         /*
838                          * A concurrent invocation of the same function might
839                          * have released the driver successfully while this one
840                          * was waiting, so check for that.
841                          */
842                         if (dev->driver != drv)
843                                 return;
844                 }
845
846                 pm_runtime_get_sync(dev);
847                 pm_runtime_clean_up_links(dev);
848
849                 driver_sysfs_remove(dev);
850
851                 if (dev->bus)
852                         blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
853                                                      BUS_NOTIFY_UNBIND_DRIVER,
854                                                      dev);
855
856                 pm_runtime_put_sync(dev);
857
858                 if (dev->bus && dev->bus->remove)
859                         dev->bus->remove(dev);
860                 else if (drv->remove)
861                         drv->remove(dev);
862
863                 device_links_driver_cleanup(dev);
864                 dma_deconfigure(dev);
865
866                 devres_release_all(dev);
867                 dev->driver = NULL;
868                 dev_set_drvdata(dev, NULL);
869                 if (dev->pm_domain && dev->pm_domain->dismiss)
870                         dev->pm_domain->dismiss(dev);
871                 pm_runtime_reinit(dev);
872
873                 klist_remove(&dev->p->knode_driver);
874                 device_pm_check_callbacks(dev);
875                 if (dev->bus)
876                         blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
877                                                      BUS_NOTIFY_UNBOUND_DRIVER,
878                                                      dev);
879
880                 kobject_uevent(&dev->kobj, KOBJ_UNBIND);
881         }
882 }
883
884 void device_release_driver_internal(struct device *dev,
885                                     struct device_driver *drv,
886                                     struct device *parent)
887 {
888         if (parent)
889                 device_lock(parent);
890
891         device_lock(dev);
892         if (!drv || drv == dev->driver)
893                 __device_release_driver(dev, parent);
894
895         device_unlock(dev);
896         if (parent)
897                 device_unlock(parent);
898 }
899
900 /**
901  * device_release_driver - manually detach device from driver.
902  * @dev: device.
903  *
904  * Manually detach device from driver.
905  * When called for a USB interface, @dev->parent lock must be held.
906  *
907  * If this function is to be called with @dev->parent lock held, ensure that
908  * the device's consumers are unbound in advance or that their locks can be
909  * acquired under the @dev->parent lock.
910  */
911 void device_release_driver(struct device *dev)
912 {
913         /*
914          * If anyone calls device_release_driver() recursively from
915          * within their ->remove callback for the same device, they
916          * will deadlock right here.
917          */
918         device_release_driver_internal(dev, NULL, NULL);
919 }
920 EXPORT_SYMBOL_GPL(device_release_driver);
921
922 /**
923  * driver_detach - detach driver from all devices it controls.
924  * @drv: driver.
925  */
926 void driver_detach(struct device_driver *drv)
927 {
928         struct device_private *dev_prv;
929         struct device *dev;
930
931         for (;;) {
932                 spin_lock(&drv->p->klist_devices.k_lock);
933                 if (list_empty(&drv->p->klist_devices.k_list)) {
934                         spin_unlock(&drv->p->klist_devices.k_lock);
935                         break;
936                 }
937                 dev_prv = list_entry(drv->p->klist_devices.k_list.prev,
938                                      struct device_private,
939                                      knode_driver.n_node);
940                 dev = dev_prv->device;
941                 get_device(dev);
942                 spin_unlock(&drv->p->klist_devices.k_lock);
943                 device_release_driver_internal(dev, drv, dev->parent);
944                 put_device(dev);
945         }
946 }