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/module.h>
23 #include <linux/kthread.h>
24 #include <linux/wait.h>
25 #include <linux/async.h>
26 #include <linux/pm_runtime.h>
27 #include <linux/pinctrl/devinfo.h>
30 #include "power/power.h"
33 * Deferred Probe infrastructure.
35 * Sometimes driver probe order matters, but the kernel doesn't always have
36 * dependency information which means some drivers will get probed before a
37 * resource it depends on is available. For example, an SDHCI driver may
38 * first need a GPIO line from an i2c GPIO controller before it can be
39 * initialized. If a required resource is not available yet, a driver can
40 * request probing to be deferred by returning -EPROBE_DEFER from its probe hook
42 * Deferred probe maintains two lists of devices, a pending list and an active
43 * list. A driver returning -EPROBE_DEFER causes the device to be added to the
44 * pending list. A successful driver probe will trigger moving all devices
45 * from the pending to the active list so that the workqueue will eventually
48 * The deferred_probe_mutex must be held any time the deferred_probe_*_list
49 * of the (struct device*)->p->deferred_probe pointers are manipulated
51 static DEFINE_MUTEX(deferred_probe_mutex
);
52 static LIST_HEAD(deferred_probe_pending_list
);
53 static LIST_HEAD(deferred_probe_active_list
);
54 static atomic_t deferred_trigger_count
= ATOMIC_INIT(0);
57 * In some cases, like suspend to RAM or hibernation, It might be reasonable
58 * to prohibit probing of devices as it could be unsafe.
59 * Once defer_all_probes is true all drivers probes will be forcibly deferred.
61 static bool defer_all_probes
;
64 * deferred_probe_work_func() - Retry probing devices in the active list.
66 static void deferred_probe_work_func(struct work_struct
*work
)
69 struct device_private
*private;
71 * This block processes every device in the deferred 'active' list.
72 * Each device is removed from the active list and passed to
73 * bus_probe_device() to re-attempt the probe. The loop continues
74 * until every device in the active list is removed and retried.
76 * Note: Once the device is removed from the list and the mutex is
77 * released, it is possible for the device get freed by another thread
78 * and cause a illegal pointer dereference. This code uses
79 * get/put_device() to ensure the device structure cannot disappear
80 * from under our feet.
82 mutex_lock(&deferred_probe_mutex
);
83 while (!list_empty(&deferred_probe_active_list
)) {
84 private = list_first_entry(&deferred_probe_active_list
,
85 typeof(*dev
->p
), deferred_probe
);
86 dev
= private->device
;
87 list_del_init(&private->deferred_probe
);
92 * Drop the mutex while probing each device; the probe path may
93 * manipulate the deferred list
95 mutex_unlock(&deferred_probe_mutex
);
98 * Force the device to the end of the dpm_list since
99 * the PM code assumes that the order we add things to
100 * the list is a good order for suspend but deferred
101 * probe makes that very unsafe.
104 device_pm_move_last(dev
);
107 dev_dbg(dev
, "Retrying from deferred list\n");
108 bus_probe_device(dev
);
110 mutex_lock(&deferred_probe_mutex
);
114 mutex_unlock(&deferred_probe_mutex
);
116 static DECLARE_WORK(deferred_probe_work
, deferred_probe_work_func
);
118 static void driver_deferred_probe_add(struct device
*dev
)
120 mutex_lock(&deferred_probe_mutex
);
121 if (list_empty(&dev
->p
->deferred_probe
)) {
122 dev_dbg(dev
, "Added to deferred list\n");
123 list_add_tail(&dev
->p
->deferred_probe
, &deferred_probe_pending_list
);
125 mutex_unlock(&deferred_probe_mutex
);
128 void driver_deferred_probe_del(struct device
*dev
)
130 mutex_lock(&deferred_probe_mutex
);
131 if (!list_empty(&dev
->p
->deferred_probe
)) {
132 dev_dbg(dev
, "Removed from deferred list\n");
133 list_del_init(&dev
->p
->deferred_probe
);
135 mutex_unlock(&deferred_probe_mutex
);
138 static bool driver_deferred_probe_enable
= false;
140 * driver_deferred_probe_trigger() - Kick off re-probing deferred devices
142 * This functions moves all devices from the pending list to the active
143 * list and schedules the deferred probe workqueue to process them. It
144 * should be called anytime a driver is successfully bound to a device.
146 * Note, there is a race condition in multi-threaded probe. In the case where
147 * more than one device is probing at the same time, it is possible for one
148 * probe to complete successfully while another is about to defer. If the second
149 * depends on the first, then it will get put on the pending list after the
150 * trigger event has already occurred and will be stuck there.
152 * The atomic 'deferred_trigger_count' is used to determine if a successful
153 * trigger has occurred in the midst of probing a driver. If the trigger count
154 * changes in the midst of a probe, then deferred processing should be triggered
157 static void driver_deferred_probe_trigger(void)
159 if (!driver_deferred_probe_enable
)
163 * A successful probe means that all the devices in the pending list
164 * should be triggered to be reprobed. Move all the deferred devices
165 * into the active list so they can be retried by the workqueue
167 mutex_lock(&deferred_probe_mutex
);
168 atomic_inc(&deferred_trigger_count
);
169 list_splice_tail_init(&deferred_probe_pending_list
,
170 &deferred_probe_active_list
);
171 mutex_unlock(&deferred_probe_mutex
);
174 * Kick the re-probe thread. It may already be scheduled, but it is
175 * safe to kick it again.
177 schedule_work(&deferred_probe_work
);
181 * device_block_probing() - Block/defere device's probes
183 * It will disable probing of devices and defer their probes instead.
185 void device_block_probing(void)
187 defer_all_probes
= true;
188 /* sync with probes to avoid races. */
189 wait_for_device_probe();
193 * device_unblock_probing() - Unblock/enable device's probes
195 * It will restore normal behavior and trigger re-probing of deferred
198 void device_unblock_probing(void)
200 defer_all_probes
= false;
201 driver_deferred_probe_trigger();
205 * deferred_probe_initcall() - Enable probing of deferred devices
207 * We don't want to get in the way when the bulk of drivers are getting probed.
208 * Instead, this initcall makes sure that deferred probing is delayed until
209 * late_initcall time.
211 static int deferred_probe_initcall(void)
213 driver_deferred_probe_enable
= true;
214 driver_deferred_probe_trigger();
215 /* Sort as many dependencies as possible before exiting initcalls */
216 flush_work(&deferred_probe_work
);
219 late_initcall(deferred_probe_initcall
);
222 * device_is_bound() - Check if device is bound to a driver
223 * @dev: device to check
225 * Returns true if passed device has already finished probing successfully
228 * This function must be called with the device lock held.
230 bool device_is_bound(struct device
*dev
)
232 return dev
->p
&& klist_node_attached(&dev
->p
->knode_driver
);
235 static void driver_bound(struct device
*dev
)
237 if (device_is_bound(dev
)) {
238 printk(KERN_WARNING
"%s: device %s already bound\n",
239 __func__
, kobject_name(&dev
->kobj
));
243 pr_debug("driver: '%s': %s: bound to device '%s'\n", dev
->driver
->name
,
244 __func__
, dev_name(dev
));
246 klist_add_tail(&dev
->p
->knode_driver
, &dev
->driver
->p
->klist_devices
);
247 device_links_driver_bound(dev
);
249 device_pm_check_callbacks(dev
);
252 * Make sure the device is no longer in one of the deferred lists and
253 * kick off retrying all pending devices
255 driver_deferred_probe_del(dev
);
256 driver_deferred_probe_trigger();
259 blocking_notifier_call_chain(&dev
->bus
->p
->bus_notifier
,
260 BUS_NOTIFY_BOUND_DRIVER
, dev
);
263 static int driver_sysfs_add(struct device
*dev
)
268 blocking_notifier_call_chain(&dev
->bus
->p
->bus_notifier
,
269 BUS_NOTIFY_BIND_DRIVER
, dev
);
271 ret
= sysfs_create_link(&dev
->driver
->p
->kobj
, &dev
->kobj
,
272 kobject_name(&dev
->kobj
));
274 ret
= sysfs_create_link(&dev
->kobj
, &dev
->driver
->p
->kobj
,
277 sysfs_remove_link(&dev
->driver
->p
->kobj
,
278 kobject_name(&dev
->kobj
));
283 static void driver_sysfs_remove(struct device
*dev
)
285 struct device_driver
*drv
= dev
->driver
;
288 sysfs_remove_link(&drv
->p
->kobj
, kobject_name(&dev
->kobj
));
289 sysfs_remove_link(&dev
->kobj
, "driver");
294 * device_bind_driver - bind a driver to one device.
297 * Allow manual attachment of a driver to a device.
298 * Caller must have already set @dev->driver.
300 * Note that this does not modify the bus reference count
301 * nor take the bus's rwsem. Please verify those are accounted
302 * for before calling this. (It is ok to call with no other effort
303 * from a driver's probe() method.)
305 * This function must be called with the device lock held.
307 int device_bind_driver(struct device
*dev
)
311 ret
= driver_sysfs_add(dev
);
315 blocking_notifier_call_chain(&dev
->bus
->p
->bus_notifier
,
316 BUS_NOTIFY_DRIVER_NOT_BOUND
, dev
);
319 EXPORT_SYMBOL_GPL(device_bind_driver
);
321 static atomic_t probe_count
= ATOMIC_INIT(0);
322 static DECLARE_WAIT_QUEUE_HEAD(probe_waitqueue
);
324 static int really_probe(struct device
*dev
, struct device_driver
*drv
)
326 int ret
= -EPROBE_DEFER
;
327 int local_trigger_count
= atomic_read(&deferred_trigger_count
);
328 bool test_remove
= IS_ENABLED(CONFIG_DEBUG_TEST_DRIVER_REMOVE
) &&
329 !drv
->suppress_bind_attrs
;
331 if (defer_all_probes
) {
333 * Value of defer_all_probes can be set only by
334 * device_defer_all_probes_enable() which, in turn, will call
335 * wait_for_device_probe() right after that to avoid any races.
337 dev_dbg(dev
, "Driver %s force probe deferral\n", drv
->name
);
338 driver_deferred_probe_add(dev
);
342 ret
= device_links_check_suppliers(dev
);
346 atomic_inc(&probe_count
);
347 pr_debug("bus: '%s': %s: probing driver %s with device %s\n",
348 drv
->bus
->name
, __func__
, drv
->name
, dev_name(dev
));
349 WARN_ON(!list_empty(&dev
->devres_head
));
354 /* If using pinctrl, bind pins now before probing */
355 ret
= pinctrl_bind_pins(dev
);
357 goto pinctrl_bind_failed
;
359 if (driver_sysfs_add(dev
)) {
360 printk(KERN_ERR
"%s: driver_sysfs_add(%s) failed\n",
361 __func__
, dev_name(dev
));
365 if (dev
->pm_domain
&& dev
->pm_domain
->activate
) {
366 ret
= dev
->pm_domain
->activate(dev
);
372 * Ensure devices are listed in devices_kset in correct order
373 * It's important to move Dev to the end of devices_kset before
374 * calling .probe, because it could be recursive and parent Dev
375 * should always go first
377 devices_kset_move_last(dev
);
379 if (dev
->bus
->probe
) {
380 ret
= dev
->bus
->probe(dev
);
383 } else if (drv
->probe
) {
384 ret
= drv
->probe(dev
);
392 if (dev
->bus
->remove
)
393 dev
->bus
->remove(dev
);
394 else if (drv
->remove
)
397 devres_release_all(dev
);
398 driver_sysfs_remove(dev
);
400 dev_set_drvdata(dev
, NULL
);
401 if (dev
->pm_domain
&& dev
->pm_domain
->dismiss
)
402 dev
->pm_domain
->dismiss(dev
);
403 pm_runtime_reinit(dev
);
408 pinctrl_init_done(dev
);
410 if (dev
->pm_domain
&& dev
->pm_domain
->sync
)
411 dev
->pm_domain
->sync(dev
);
415 pr_debug("bus: '%s': %s: bound device %s to driver %s\n",
416 drv
->bus
->name
, __func__
, dev_name(dev
), drv
->name
);
421 blocking_notifier_call_chain(&dev
->bus
->p
->bus_notifier
,
422 BUS_NOTIFY_DRIVER_NOT_BOUND
, dev
);
424 device_links_no_driver(dev
);
425 devres_release_all(dev
);
426 driver_sysfs_remove(dev
);
428 dev_set_drvdata(dev
, NULL
);
429 if (dev
->pm_domain
&& dev
->pm_domain
->dismiss
)
430 dev
->pm_domain
->dismiss(dev
);
431 pm_runtime_reinit(dev
);
435 /* Driver requested deferred probing */
436 dev_dbg(dev
, "Driver %s requests probe deferral\n", drv
->name
);
437 driver_deferred_probe_add(dev
);
438 /* Did a trigger occur while probing? Need to re-trigger if yes */
439 if (local_trigger_count
!= atomic_read(&deferred_trigger_count
))
440 driver_deferred_probe_trigger();
444 pr_debug("%s: probe of %s rejects match %d\n",
445 drv
->name
, dev_name(dev
), ret
);
448 /* driver matched but the probe failed */
450 "%s: probe of %s failed with error %d\n",
451 drv
->name
, dev_name(dev
), ret
);
454 * Ignore errors returned by ->probe so that the next driver can try
459 atomic_dec(&probe_count
);
460 wake_up(&probe_waitqueue
);
466 * Determine if the probe sequence is finished or not.
468 * Should somehow figure out how to use a semaphore, not an atomic variable...
470 int driver_probe_done(void)
472 pr_debug("%s: probe_count = %d\n", __func__
,
473 atomic_read(&probe_count
));
474 if (atomic_read(&probe_count
))
480 * wait_for_device_probe
481 * Wait for device probing to be completed.
483 void wait_for_device_probe(void)
485 /* wait for the deferred probe workqueue to finish */
486 flush_work(&deferred_probe_work
);
488 /* wait for the known devices to complete their probing */
489 wait_event(probe_waitqueue
, atomic_read(&probe_count
) == 0);
490 async_synchronize_full();
492 EXPORT_SYMBOL_GPL(wait_for_device_probe
);
495 * driver_probe_device - attempt to bind device & driver together
496 * @drv: driver to bind a device to
497 * @dev: device to try to bind to the driver
499 * This function returns -ENODEV if the device is not registered,
500 * 1 if the device is bound successfully and 0 otherwise.
502 * This function must be called with @dev lock held. When called for a
503 * USB interface, @dev->parent lock must be held as well.
505 * If the device has a parent, runtime-resume the parent before driver probing.
507 int driver_probe_device(struct device_driver
*drv
, struct device
*dev
)
511 if (!device_is_registered(dev
))
514 pr_debug("bus: '%s': %s: matched device %s with driver %s\n",
515 drv
->bus
->name
, __func__
, dev_name(dev
), drv
->name
);
517 pm_runtime_get_suppliers(dev
);
519 pm_runtime_get_sync(dev
->parent
);
521 pm_runtime_barrier(dev
);
522 ret
= really_probe(dev
, drv
);
523 pm_request_idle(dev
);
526 pm_runtime_put(dev
->parent
);
528 pm_runtime_put_suppliers(dev
);
532 bool driver_allows_async_probing(struct device_driver
*drv
)
534 switch (drv
->probe_type
) {
535 case PROBE_PREFER_ASYNCHRONOUS
:
538 case PROBE_FORCE_SYNCHRONOUS
:
542 if (module_requested_async_probing(drv
->owner
))
549 struct device_attach_data
{
553 * Indicates whether we are are considering asynchronous probing or
554 * not. Only initial binding after device or driver registration
555 * (including deferral processing) may be done asynchronously, the
556 * rest is always synchronous, as we expect it is being done by
557 * request from userspace.
562 * Indicates if we are binding synchronous or asynchronous drivers.
563 * When asynchronous probing is enabled we'll execute 2 passes
564 * over drivers: first pass doing synchronous probing and second
565 * doing asynchronous probing (if synchronous did not succeed -
566 * most likely because there was no driver requiring synchronous
567 * probing - and we found asynchronous driver during first pass).
568 * The 2 passes are done because we can't shoot asynchronous
569 * probe for given device and driver from bus_for_each_drv() since
570 * driver pointer is not guaranteed to stay valid once
571 * bus_for_each_drv() iterates to the next driver on the bus.
576 * We'll set have_async to 'true' if, while scanning for matching
577 * driver, we'll encounter one that requests asynchronous probing.
582 static int __device_attach_driver(struct device_driver
*drv
, void *_data
)
584 struct device_attach_data
*data
= _data
;
585 struct device
*dev
= data
->dev
;
590 * Check if device has already been claimed. This may
591 * happen with driver loading, device discovery/registration,
592 * and deferred probe processing happens all at once with
598 ret
= driver_match_device(drv
, dev
);
602 } else if (ret
== -EPROBE_DEFER
) {
603 dev_dbg(dev
, "Device match requests probe deferral\n");
604 driver_deferred_probe_add(dev
);
605 } else if (ret
< 0) {
606 dev_dbg(dev
, "Bus failed to match device: %d", ret
);
608 } /* ret > 0 means positive match */
610 async_allowed
= driver_allows_async_probing(drv
);
613 data
->have_async
= true;
615 if (data
->check_async
&& async_allowed
!= data
->want_async
)
618 return driver_probe_device(drv
, dev
);
621 static void __device_attach_async_helper(void *_dev
, async_cookie_t cookie
)
623 struct device
*dev
= _dev
;
624 struct device_attach_data data
= {
633 pm_runtime_get_sync(dev
->parent
);
635 bus_for_each_drv(dev
->bus
, NULL
, &data
, __device_attach_driver
);
636 dev_dbg(dev
, "async probe completed\n");
638 pm_request_idle(dev
);
641 pm_runtime_put(dev
->parent
);
648 static int __device_attach(struct device
*dev
, bool allow_async
)
654 if (device_is_bound(dev
)) {
658 ret
= device_bind_driver(dev
);
666 struct device_attach_data data
= {
668 .check_async
= allow_async
,
673 pm_runtime_get_sync(dev
->parent
);
675 ret
= bus_for_each_drv(dev
->bus
, NULL
, &data
,
676 __device_attach_driver
);
677 if (!ret
&& allow_async
&& data
.have_async
) {
679 * If we could not find appropriate driver
680 * synchronously and we are allowed to do
681 * async probes and there are drivers that
682 * want to probe asynchronously, we'll
685 dev_dbg(dev
, "scheduling asynchronous probe\n");
687 async_schedule(__device_attach_async_helper
, dev
);
689 pm_request_idle(dev
);
693 pm_runtime_put(dev
->parent
);
701 * device_attach - try to attach device to a driver.
704 * Walk the list of drivers that the bus has and call
705 * driver_probe_device() for each pair. If a compatible
706 * pair is found, break out and return.
708 * Returns 1 if the device was bound to a driver;
709 * 0 if no matching driver was found;
710 * -ENODEV if the device is not registered.
712 * When called for a USB interface, @dev->parent lock must be held.
714 int device_attach(struct device
*dev
)
716 return __device_attach(dev
, false);
718 EXPORT_SYMBOL_GPL(device_attach
);
720 void device_initial_probe(struct device
*dev
)
722 __device_attach(dev
, true);
725 static int __driver_attach(struct device
*dev
, void *data
)
727 struct device_driver
*drv
= data
;
731 * Lock device and try to bind to it. We drop the error
732 * here and always return 0, because we need to keep trying
733 * to bind to devices and some drivers will return an error
734 * simply if it didn't support the device.
736 * driver_probe_device() will spit a warning if there
740 ret
= driver_match_device(drv
, dev
);
744 } else if (ret
== -EPROBE_DEFER
) {
745 dev_dbg(dev
, "Device match requests probe deferral\n");
746 driver_deferred_probe_add(dev
);
747 } else if (ret
< 0) {
748 dev_dbg(dev
, "Bus failed to match device: %d", ret
);
750 } /* ret > 0 means positive match */
752 if (dev
->parent
) /* Needed for USB */
753 device_lock(dev
->parent
);
756 driver_probe_device(drv
, dev
);
759 device_unlock(dev
->parent
);
765 * driver_attach - try to bind driver to devices.
768 * Walk the list of devices that the bus has on it and try to
769 * match the driver with each one. If driver_probe_device()
770 * returns 0 and the @dev->driver is set, we've found a
773 int driver_attach(struct device_driver
*drv
)
775 return bus_for_each_dev(drv
->bus
, NULL
, drv
, __driver_attach
);
777 EXPORT_SYMBOL_GPL(driver_attach
);
780 * __device_release_driver() must be called with @dev lock held.
781 * When called for a USB interface, @dev->parent lock must be held as well.
783 static void __device_release_driver(struct device
*dev
, struct device
*parent
)
785 struct device_driver
*drv
;
789 if (driver_allows_async_probing(drv
))
790 async_synchronize_full();
792 while (device_links_busy(dev
)) {
795 device_unlock(parent
);
797 device_links_unbind_consumers(dev
);
803 * A concurrent invocation of the same function might
804 * have released the driver successfully while this one
805 * was waiting, so check for that.
807 if (dev
->driver
!= drv
)
811 pm_runtime_get_sync(dev
);
812 pm_runtime_clean_up_links(dev
);
814 driver_sysfs_remove(dev
);
817 blocking_notifier_call_chain(&dev
->bus
->p
->bus_notifier
,
818 BUS_NOTIFY_UNBIND_DRIVER
,
821 pm_runtime_put_sync(dev
);
823 if (dev
->bus
&& dev
->bus
->remove
)
824 dev
->bus
->remove(dev
);
825 else if (drv
->remove
)
828 device_links_driver_cleanup(dev
);
829 devres_release_all(dev
);
831 dev_set_drvdata(dev
, NULL
);
832 if (dev
->pm_domain
&& dev
->pm_domain
->dismiss
)
833 dev
->pm_domain
->dismiss(dev
);
834 pm_runtime_reinit(dev
);
836 klist_remove(&dev
->p
->knode_driver
);
837 device_pm_check_callbacks(dev
);
839 blocking_notifier_call_chain(&dev
->bus
->p
->bus_notifier
,
840 BUS_NOTIFY_UNBOUND_DRIVER
,
845 void device_release_driver_internal(struct device
*dev
,
846 struct device_driver
*drv
,
847 struct device
*parent
)
853 if (!drv
|| drv
== dev
->driver
)
854 __device_release_driver(dev
, parent
);
858 device_unlock(parent
);
862 * device_release_driver - manually detach device from driver.
865 * Manually detach device from driver.
866 * When called for a USB interface, @dev->parent lock must be held.
868 * If this function is to be called with @dev->parent lock held, ensure that
869 * the device's consumers are unbound in advance or that their locks can be
870 * acquired under the @dev->parent lock.
872 void device_release_driver(struct device
*dev
)
875 * If anyone calls device_release_driver() recursively from
876 * within their ->remove callback for the same device, they
877 * will deadlock right here.
879 device_release_driver_internal(dev
, NULL
, NULL
);
881 EXPORT_SYMBOL_GPL(device_release_driver
);
884 * driver_detach - detach driver from all devices it controls.
887 void driver_detach(struct device_driver
*drv
)
889 struct device_private
*dev_prv
;
893 spin_lock(&drv
->p
->klist_devices
.k_lock
);
894 if (list_empty(&drv
->p
->klist_devices
.k_list
)) {
895 spin_unlock(&drv
->p
->klist_devices
.k_lock
);
898 dev_prv
= list_entry(drv
->p
->klist_devices
.k_list
.prev
,
899 struct device_private
,
900 knode_driver
.n_node
);
901 dev
= dev_prv
->device
;
903 spin_unlock(&drv
->p
->klist_devices
.k_lock
);
904 device_release_driver_internal(dev
, drv
, dev
->parent
);