2 * drivers/base/dd.c - The core device/driver interactions.
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.
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'.
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.
17 * This file is released under the GPLv2
20 #include <linux/device.h>
21 #include <linux/delay.h>
22 #include <linux/dma-mapping.h>
23 #include <linux/module.h>
24 #include <linux/kthread.h>
25 #include <linux/wait.h>
26 #include <linux/async.h>
27 #include <linux/pm_runtime.h>
28 #include <linux/pinctrl/devinfo.h>
31 #include "power/power.h"
34 * Deferred Probe infrastructure.
36 * Sometimes driver probe order matters, but the kernel doesn't always have
37 * dependency information which means some drivers will get probed before a
38 * resource it depends on is available. For example, an SDHCI driver may
39 * first need a GPIO line from an i2c GPIO controller before it can be
40 * initialized. If a required resource is not available yet, a driver can
41 * request probing to be deferred by returning -EPROBE_DEFER from its probe hook
43 * Deferred probe maintains two lists of devices, a pending list and an active
44 * list. A driver returning -EPROBE_DEFER causes the device to be added to the
45 * pending list. A successful driver probe will trigger moving all devices
46 * from the pending to the active list so that the workqueue will eventually
49 * The deferred_probe_mutex must be held any time the deferred_probe_*_list
50 * of the (struct device*)->p->deferred_probe pointers are manipulated
52 static DEFINE_MUTEX(deferred_probe_mutex
);
53 static LIST_HEAD(deferred_probe_pending_list
);
54 static LIST_HEAD(deferred_probe_active_list
);
55 static atomic_t deferred_trigger_count
= ATOMIC_INIT(0);
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.
62 static bool defer_all_probes
;
65 * deferred_probe_work_func() - Retry probing devices in the active list.
67 static void deferred_probe_work_func(struct work_struct
*work
)
70 struct device_private
*private;
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.
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.
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
);
93 * Drop the mutex while probing each device; the probe path may
94 * manipulate the deferred list
96 mutex_unlock(&deferred_probe_mutex
);
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.
105 device_pm_move_last(dev
);
108 dev_dbg(dev
, "Retrying from deferred list\n");
109 bus_probe_device(dev
);
111 mutex_lock(&deferred_probe_mutex
);
115 mutex_unlock(&deferred_probe_mutex
);
117 static DECLARE_WORK(deferred_probe_work
, deferred_probe_work_func
);
119 static void driver_deferred_probe_add(struct device
*dev
)
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
);
126 mutex_unlock(&deferred_probe_mutex
);
129 void driver_deferred_probe_del(struct device
*dev
)
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
);
136 mutex_unlock(&deferred_probe_mutex
);
139 static bool driver_deferred_probe_enable
= false;
141 * driver_deferred_probe_trigger() - Kick off re-probing deferred devices
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.
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.
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
158 static void driver_deferred_probe_trigger(void)
160 if (!driver_deferred_probe_enable
)
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
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
);
175 * Kick the re-probe thread. It may already be scheduled, but it is
176 * safe to kick it again.
178 schedule_work(&deferred_probe_work
);
182 * device_block_probing() - Block/defere device's probes
184 * It will disable probing of devices and defer their probes instead.
186 void device_block_probing(void)
188 defer_all_probes
= true;
189 /* sync with probes to avoid races. */
190 wait_for_device_probe();
194 * device_unblock_probing() - Unblock/enable device's probes
196 * It will restore normal behavior and trigger re-probing of deferred
199 void device_unblock_probing(void)
201 defer_all_probes
= false;
202 driver_deferred_probe_trigger();
206 * deferred_probe_initcall() - Enable probing of deferred devices
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.
212 static int deferred_probe_initcall(void)
214 driver_deferred_probe_enable
= true;
215 driver_deferred_probe_trigger();
216 /* Sort as many dependencies as possible before exiting initcalls */
217 flush_work(&deferred_probe_work
);
220 late_initcall(deferred_probe_initcall
);
223 * device_is_bound() - Check if device is bound to a driver
224 * @dev: device to check
226 * Returns true if passed device has already finished probing successfully
229 * This function must be called with the device lock held.
231 bool device_is_bound(struct device
*dev
)
233 return dev
->p
&& klist_node_attached(&dev
->p
->knode_driver
);
236 static void driver_bound(struct device
*dev
)
238 if (device_is_bound(dev
)) {
239 printk(KERN_WARNING
"%s: device %s already bound\n",
240 __func__
, kobject_name(&dev
->kobj
));
244 pr_debug("driver: '%s': %s: bound to device '%s'\n", dev
->driver
->name
,
245 __func__
, dev_name(dev
));
247 klist_add_tail(&dev
->p
->knode_driver
, &dev
->driver
->p
->klist_devices
);
248 device_links_driver_bound(dev
);
250 device_pm_check_callbacks(dev
);
253 * Make sure the device is no longer in one of the deferred lists and
254 * kick off retrying all pending devices
256 driver_deferred_probe_del(dev
);
257 driver_deferred_probe_trigger();
260 blocking_notifier_call_chain(&dev
->bus
->p
->bus_notifier
,
261 BUS_NOTIFY_BOUND_DRIVER
, dev
);
263 kobject_uevent(&dev
->kobj
, KOBJ_BIND
);
266 static int driver_sysfs_add(struct device
*dev
)
271 blocking_notifier_call_chain(&dev
->bus
->p
->bus_notifier
,
272 BUS_NOTIFY_BIND_DRIVER
, dev
);
274 ret
= sysfs_create_link(&dev
->driver
->p
->kobj
, &dev
->kobj
,
275 kobject_name(&dev
->kobj
));
277 ret
= sysfs_create_link(&dev
->kobj
, &dev
->driver
->p
->kobj
,
280 sysfs_remove_link(&dev
->driver
->p
->kobj
,
281 kobject_name(&dev
->kobj
));
286 static void driver_sysfs_remove(struct device
*dev
)
288 struct device_driver
*drv
= dev
->driver
;
291 sysfs_remove_link(&drv
->p
->kobj
, kobject_name(&dev
->kobj
));
292 sysfs_remove_link(&dev
->kobj
, "driver");
297 * device_bind_driver - bind a driver to one device.
300 * Allow manual attachment of a driver to a device.
301 * Caller must have already set @dev->driver.
303 * Note that this does not modify the bus reference count
304 * nor take the bus's rwsem. Please verify those are accounted
305 * for before calling this. (It is ok to call with no other effort
306 * from a driver's probe() method.)
308 * This function must be called with the device lock held.
310 int device_bind_driver(struct device
*dev
)
314 ret
= driver_sysfs_add(dev
);
318 blocking_notifier_call_chain(&dev
->bus
->p
->bus_notifier
,
319 BUS_NOTIFY_DRIVER_NOT_BOUND
, dev
);
322 EXPORT_SYMBOL_GPL(device_bind_driver
);
324 static atomic_t probe_count
= ATOMIC_INIT(0);
325 static DECLARE_WAIT_QUEUE_HEAD(probe_waitqueue
);
327 static int really_probe(struct device
*dev
, struct device_driver
*drv
)
329 int ret
= -EPROBE_DEFER
;
330 int local_trigger_count
= atomic_read(&deferred_trigger_count
);
331 bool test_remove
= IS_ENABLED(CONFIG_DEBUG_TEST_DRIVER_REMOVE
) &&
332 !drv
->suppress_bind_attrs
;
334 if (defer_all_probes
) {
336 * Value of defer_all_probes can be set only by
337 * device_defer_all_probes_enable() which, in turn, will call
338 * wait_for_device_probe() right after that to avoid any races.
340 dev_dbg(dev
, "Driver %s force probe deferral\n", drv
->name
);
341 driver_deferred_probe_add(dev
);
345 ret
= device_links_check_suppliers(dev
);
349 atomic_inc(&probe_count
);
350 pr_debug("bus: '%s': %s: probing driver %s with device %s\n",
351 drv
->bus
->name
, __func__
, drv
->name
, dev_name(dev
));
352 WARN_ON(!list_empty(&dev
->devres_head
));
357 /* If using pinctrl, bind pins now before probing */
358 ret
= pinctrl_bind_pins(dev
);
360 goto pinctrl_bind_failed
;
362 ret
= dma_configure(dev
);
366 if (driver_sysfs_add(dev
)) {
367 printk(KERN_ERR
"%s: driver_sysfs_add(%s) failed\n",
368 __func__
, dev_name(dev
));
372 if (dev
->pm_domain
&& dev
->pm_domain
->activate
) {
373 ret
= dev
->pm_domain
->activate(dev
);
379 * Ensure devices are listed in devices_kset in correct order
380 * It's important to move Dev to the end of devices_kset before
381 * calling .probe, because it could be recursive and parent Dev
382 * should always go first
384 devices_kset_move_last(dev
);
386 if (dev
->bus
->probe
) {
387 ret
= dev
->bus
->probe(dev
);
390 } else if (drv
->probe
) {
391 ret
= drv
->probe(dev
);
399 if (dev
->bus
->remove
)
400 dev
->bus
->remove(dev
);
401 else if (drv
->remove
)
404 devres_release_all(dev
);
405 driver_sysfs_remove(dev
);
407 dev_set_drvdata(dev
, NULL
);
408 if (dev
->pm_domain
&& dev
->pm_domain
->dismiss
)
409 dev
->pm_domain
->dismiss(dev
);
410 pm_runtime_reinit(dev
);
415 pinctrl_init_done(dev
);
417 if (dev
->pm_domain
&& dev
->pm_domain
->sync
)
418 dev
->pm_domain
->sync(dev
);
422 pr_debug("bus: '%s': %s: bound device %s to driver %s\n",
423 drv
->bus
->name
, __func__
, dev_name(dev
), drv
->name
);
427 dma_deconfigure(dev
);
430 blocking_notifier_call_chain(&dev
->bus
->p
->bus_notifier
,
431 BUS_NOTIFY_DRIVER_NOT_BOUND
, dev
);
433 device_links_no_driver(dev
);
434 devres_release_all(dev
);
435 driver_sysfs_remove(dev
);
437 dev_set_drvdata(dev
, NULL
);
438 if (dev
->pm_domain
&& dev
->pm_domain
->dismiss
)
439 dev
->pm_domain
->dismiss(dev
);
440 pm_runtime_reinit(dev
);
444 /* Driver requested deferred probing */
445 dev_dbg(dev
, "Driver %s requests probe deferral\n", drv
->name
);
446 driver_deferred_probe_add(dev
);
447 /* Did a trigger occur while probing? Need to re-trigger if yes */
448 if (local_trigger_count
!= atomic_read(&deferred_trigger_count
))
449 driver_deferred_probe_trigger();
453 pr_debug("%s: probe of %s rejects match %d\n",
454 drv
->name
, dev_name(dev
), ret
);
457 /* driver matched but the probe failed */
459 "%s: probe of %s failed with error %d\n",
460 drv
->name
, dev_name(dev
), ret
);
463 * Ignore errors returned by ->probe so that the next driver can try
468 atomic_dec(&probe_count
);
469 wake_up(&probe_waitqueue
);
475 * Determine if the probe sequence is finished or not.
477 * Should somehow figure out how to use a semaphore, not an atomic variable...
479 int driver_probe_done(void)
481 pr_debug("%s: probe_count = %d\n", __func__
,
482 atomic_read(&probe_count
));
483 if (atomic_read(&probe_count
))
489 * wait_for_device_probe
490 * Wait for device probing to be completed.
492 void wait_for_device_probe(void)
494 /* wait for the deferred probe workqueue to finish */
495 flush_work(&deferred_probe_work
);
497 /* wait for the known devices to complete their probing */
498 wait_event(probe_waitqueue
, atomic_read(&probe_count
) == 0);
499 async_synchronize_full();
501 EXPORT_SYMBOL_GPL(wait_for_device_probe
);
504 * driver_probe_device - attempt to bind device & driver together
505 * @drv: driver to bind a device to
506 * @dev: device to try to bind to the driver
508 * This function returns -ENODEV if the device is not registered,
509 * 1 if the device is bound successfully and 0 otherwise.
511 * This function must be called with @dev lock held. When called for a
512 * USB interface, @dev->parent lock must be held as well.
514 * If the device has a parent, runtime-resume the parent before driver probing.
516 int driver_probe_device(struct device_driver
*drv
, struct device
*dev
)
520 if (!device_is_registered(dev
))
523 pr_debug("bus: '%s': %s: matched device %s with driver %s\n",
524 drv
->bus
->name
, __func__
, dev_name(dev
), drv
->name
);
526 pm_runtime_get_suppliers(dev
);
528 pm_runtime_get_sync(dev
->parent
);
530 pm_runtime_barrier(dev
);
531 ret
= really_probe(dev
, drv
);
532 pm_request_idle(dev
);
535 pm_runtime_put(dev
->parent
);
537 pm_runtime_put_suppliers(dev
);
541 bool driver_allows_async_probing(struct device_driver
*drv
)
543 switch (drv
->probe_type
) {
544 case PROBE_PREFER_ASYNCHRONOUS
:
547 case PROBE_FORCE_SYNCHRONOUS
:
551 if (module_requested_async_probing(drv
->owner
))
558 struct device_attach_data
{
562 * Indicates whether we are are considering asynchronous probing or
563 * not. Only initial binding after device or driver registration
564 * (including deferral processing) may be done asynchronously, the
565 * rest is always synchronous, as we expect it is being done by
566 * request from userspace.
571 * Indicates if we are binding synchronous or asynchronous drivers.
572 * When asynchronous probing is enabled we'll execute 2 passes
573 * over drivers: first pass doing synchronous probing and second
574 * doing asynchronous probing (if synchronous did not succeed -
575 * most likely because there was no driver requiring synchronous
576 * probing - and we found asynchronous driver during first pass).
577 * The 2 passes are done because we can't shoot asynchronous
578 * probe for given device and driver from bus_for_each_drv() since
579 * driver pointer is not guaranteed to stay valid once
580 * bus_for_each_drv() iterates to the next driver on the bus.
585 * We'll set have_async to 'true' if, while scanning for matching
586 * driver, we'll encounter one that requests asynchronous probing.
591 static int __device_attach_driver(struct device_driver
*drv
, void *_data
)
593 struct device_attach_data
*data
= _data
;
594 struct device
*dev
= data
->dev
;
599 * Check if device has already been claimed. This may
600 * happen with driver loading, device discovery/registration,
601 * and deferred probe processing happens all at once with
607 ret
= driver_match_device(drv
, dev
);
611 } else if (ret
== -EPROBE_DEFER
) {
612 dev_dbg(dev
, "Device match requests probe deferral\n");
613 driver_deferred_probe_add(dev
);
614 } else if (ret
< 0) {
615 dev_dbg(dev
, "Bus failed to match device: %d", ret
);
617 } /* ret > 0 means positive match */
619 async_allowed
= driver_allows_async_probing(drv
);
622 data
->have_async
= true;
624 if (data
->check_async
&& async_allowed
!= data
->want_async
)
627 return driver_probe_device(drv
, dev
);
630 static void __device_attach_async_helper(void *_dev
, async_cookie_t cookie
)
632 struct device
*dev
= _dev
;
633 struct device_attach_data data
= {
642 pm_runtime_get_sync(dev
->parent
);
644 bus_for_each_drv(dev
->bus
, NULL
, &data
, __device_attach_driver
);
645 dev_dbg(dev
, "async probe completed\n");
647 pm_request_idle(dev
);
650 pm_runtime_put(dev
->parent
);
657 static int __device_attach(struct device
*dev
, bool allow_async
)
663 if (device_is_bound(dev
)) {
667 ret
= device_bind_driver(dev
);
675 struct device_attach_data data
= {
677 .check_async
= allow_async
,
682 pm_runtime_get_sync(dev
->parent
);
684 ret
= bus_for_each_drv(dev
->bus
, NULL
, &data
,
685 __device_attach_driver
);
686 if (!ret
&& allow_async
&& data
.have_async
) {
688 * If we could not find appropriate driver
689 * synchronously and we are allowed to do
690 * async probes and there are drivers that
691 * want to probe asynchronously, we'll
694 dev_dbg(dev
, "scheduling asynchronous probe\n");
696 async_schedule(__device_attach_async_helper
, dev
);
698 pm_request_idle(dev
);
702 pm_runtime_put(dev
->parent
);
710 * device_attach - try to attach device to a driver.
713 * Walk the list of drivers that the bus has and call
714 * driver_probe_device() for each pair. If a compatible
715 * pair is found, break out and return.
717 * Returns 1 if the device was bound to a driver;
718 * 0 if no matching driver was found;
719 * -ENODEV if the device is not registered.
721 * When called for a USB interface, @dev->parent lock must be held.
723 int device_attach(struct device
*dev
)
725 return __device_attach(dev
, false);
727 EXPORT_SYMBOL_GPL(device_attach
);
729 void device_initial_probe(struct device
*dev
)
731 __device_attach(dev
, true);
734 static int __driver_attach(struct device
*dev
, void *data
)
736 struct device_driver
*drv
= data
;
740 * Lock device and try to bind to it. We drop the error
741 * here and always return 0, because we need to keep trying
742 * to bind to devices and some drivers will return an error
743 * simply if it didn't support the device.
745 * driver_probe_device() will spit a warning if there
749 ret
= driver_match_device(drv
, dev
);
753 } else if (ret
== -EPROBE_DEFER
) {
754 dev_dbg(dev
, "Device match requests probe deferral\n");
755 driver_deferred_probe_add(dev
);
756 } else if (ret
< 0) {
757 dev_dbg(dev
, "Bus failed to match device: %d", ret
);
759 } /* ret > 0 means positive match */
761 if (dev
->parent
) /* Needed for USB */
762 device_lock(dev
->parent
);
765 driver_probe_device(drv
, dev
);
768 device_unlock(dev
->parent
);
774 * driver_attach - try to bind driver to devices.
777 * Walk the list of devices that the bus has on it and try to
778 * match the driver with each one. If driver_probe_device()
779 * returns 0 and the @dev->driver is set, we've found a
782 int driver_attach(struct device_driver
*drv
)
784 return bus_for_each_dev(drv
->bus
, NULL
, drv
, __driver_attach
);
786 EXPORT_SYMBOL_GPL(driver_attach
);
789 * __device_release_driver() must be called with @dev lock held.
790 * When called for a USB interface, @dev->parent lock must be held as well.
792 static void __device_release_driver(struct device
*dev
, struct device
*parent
)
794 struct device_driver
*drv
;
798 if (driver_allows_async_probing(drv
))
799 async_synchronize_full();
801 while (device_links_busy(dev
)) {
804 device_unlock(parent
);
806 device_links_unbind_consumers(dev
);
812 * A concurrent invocation of the same function might
813 * have released the driver successfully while this one
814 * was waiting, so check for that.
816 if (dev
->driver
!= drv
)
820 pm_runtime_get_sync(dev
);
821 pm_runtime_clean_up_links(dev
);
823 driver_sysfs_remove(dev
);
826 blocking_notifier_call_chain(&dev
->bus
->p
->bus_notifier
,
827 BUS_NOTIFY_UNBIND_DRIVER
,
830 pm_runtime_put_sync(dev
);
832 if (dev
->bus
&& dev
->bus
->remove
)
833 dev
->bus
->remove(dev
);
834 else if (drv
->remove
)
837 device_links_driver_cleanup(dev
);
838 dma_deconfigure(dev
);
840 devres_release_all(dev
);
842 dev_set_drvdata(dev
, NULL
);
843 if (dev
->pm_domain
&& dev
->pm_domain
->dismiss
)
844 dev
->pm_domain
->dismiss(dev
);
845 pm_runtime_reinit(dev
);
847 klist_remove(&dev
->p
->knode_driver
);
848 device_pm_check_callbacks(dev
);
850 blocking_notifier_call_chain(&dev
->bus
->p
->bus_notifier
,
851 BUS_NOTIFY_UNBOUND_DRIVER
,
854 kobject_uevent(&dev
->kobj
, KOBJ_UNBIND
);
858 void device_release_driver_internal(struct device
*dev
,
859 struct device_driver
*drv
,
860 struct device
*parent
)
866 if (!drv
|| drv
== dev
->driver
)
867 __device_release_driver(dev
, parent
);
871 device_unlock(parent
);
875 * device_release_driver - manually detach device from driver.
878 * Manually detach device from driver.
879 * When called for a USB interface, @dev->parent lock must be held.
881 * If this function is to be called with @dev->parent lock held, ensure that
882 * the device's consumers are unbound in advance or that their locks can be
883 * acquired under the @dev->parent lock.
885 void device_release_driver(struct device
*dev
)
888 * If anyone calls device_release_driver() recursively from
889 * within their ->remove callback for the same device, they
890 * will deadlock right here.
892 device_release_driver_internal(dev
, NULL
, NULL
);
894 EXPORT_SYMBOL_GPL(device_release_driver
);
897 * driver_detach - detach driver from all devices it controls.
900 void driver_detach(struct device_driver
*drv
)
902 struct device_private
*dev_prv
;
906 spin_lock(&drv
->p
->klist_devices
.k_lock
);
907 if (list_empty(&drv
->p
->klist_devices
.k_list
)) {
908 spin_unlock(&drv
->p
->klist_devices
.k_lock
);
911 dev_prv
= list_entry(drv
->p
->klist_devices
.k_list
.prev
,
912 struct device_private
,
913 knode_driver
.n_node
);
914 dev
= dev_prv
->device
;
916 spin_unlock(&drv
->p
->klist_devices
.k_lock
);
917 device_release_driver_internal(dev
, drv
, dev
->parent
);