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 struct workqueue_struct
*deferred_wq
;
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 queue_work(deferred_wq
, &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 deferred_wq
= create_singlethread_workqueue("deferwq");
215 if (WARN_ON(!deferred_wq
))
218 driver_deferred_probe_enable
= true;
219 driver_deferred_probe_trigger();
220 /* Sort as many dependencies as possible before exiting initcalls */
221 flush_workqueue(deferred_wq
);
224 late_initcall(deferred_probe_initcall
);
226 static void driver_bound(struct device
*dev
)
228 if (klist_node_attached(&dev
->p
->knode_driver
)) {
229 printk(KERN_WARNING
"%s: device %s already bound\n",
230 __func__
, kobject_name(&dev
->kobj
));
234 pr_debug("driver: '%s': %s: bound to device '%s'\n", dev
->driver
->name
,
235 __func__
, dev_name(dev
));
237 klist_add_tail(&dev
->p
->knode_driver
, &dev
->driver
->p
->klist_devices
);
240 * Make sure the device is no longer in one of the deferred lists and
241 * kick off retrying all pending devices
243 driver_deferred_probe_del(dev
);
244 driver_deferred_probe_trigger();
247 blocking_notifier_call_chain(&dev
->bus
->p
->bus_notifier
,
248 BUS_NOTIFY_BOUND_DRIVER
, dev
);
251 static int driver_sysfs_add(struct device
*dev
)
256 blocking_notifier_call_chain(&dev
->bus
->p
->bus_notifier
,
257 BUS_NOTIFY_BIND_DRIVER
, dev
);
259 ret
= sysfs_create_link(&dev
->driver
->p
->kobj
, &dev
->kobj
,
260 kobject_name(&dev
->kobj
));
262 ret
= sysfs_create_link(&dev
->kobj
, &dev
->driver
->p
->kobj
,
265 sysfs_remove_link(&dev
->driver
->p
->kobj
,
266 kobject_name(&dev
->kobj
));
271 static void driver_sysfs_remove(struct device
*dev
)
273 struct device_driver
*drv
= dev
->driver
;
276 sysfs_remove_link(&drv
->p
->kobj
, kobject_name(&dev
->kobj
));
277 sysfs_remove_link(&dev
->kobj
, "driver");
282 * device_bind_driver - bind a driver to one device.
285 * Allow manual attachment of a driver to a device.
286 * Caller must have already set @dev->driver.
288 * Note that this does not modify the bus reference count
289 * nor take the bus's rwsem. Please verify those are accounted
290 * for before calling this. (It is ok to call with no other effort
291 * from a driver's probe() method.)
293 * This function must be called with the device lock held.
295 int device_bind_driver(struct device
*dev
)
299 ret
= driver_sysfs_add(dev
);
303 blocking_notifier_call_chain(&dev
->bus
->p
->bus_notifier
,
304 BUS_NOTIFY_DRIVER_NOT_BOUND
, dev
);
307 EXPORT_SYMBOL_GPL(device_bind_driver
);
309 static atomic_t probe_count
= ATOMIC_INIT(0);
310 static DECLARE_WAIT_QUEUE_HEAD(probe_waitqueue
);
312 static int really_probe(struct device
*dev
, struct device_driver
*drv
)
314 int ret
= -EPROBE_DEFER
;
315 int local_trigger_count
= atomic_read(&deferred_trigger_count
);
317 if (defer_all_probes
) {
319 * Value of defer_all_probes can be set only by
320 * device_defer_all_probes_enable() which, in turn, will call
321 * wait_for_device_probe() right after that to avoid any races.
323 dev_dbg(dev
, "Driver %s force probe deferral\n", drv
->name
);
324 driver_deferred_probe_add(dev
);
328 atomic_inc(&probe_count
);
329 pr_debug("bus: '%s': %s: probing driver %s with device %s\n",
330 drv
->bus
->name
, __func__
, drv
->name
, dev_name(dev
));
331 WARN_ON(!list_empty(&dev
->devres_head
));
335 /* If using pinctrl, bind pins now before probing */
336 ret
= pinctrl_bind_pins(dev
);
338 goto pinctrl_bind_failed
;
340 if (driver_sysfs_add(dev
)) {
341 printk(KERN_ERR
"%s: driver_sysfs_add(%s) failed\n",
342 __func__
, dev_name(dev
));
346 if (dev
->pm_domain
&& dev
->pm_domain
->activate
) {
347 ret
= dev
->pm_domain
->activate(dev
);
353 * Ensure devices are listed in devices_kset in correct order
354 * It's important to move Dev to the end of devices_kset before
355 * calling .probe, because it could be recursive and parent Dev
356 * should always go first
358 devices_kset_move_last(dev
);
360 if (dev
->bus
->probe
) {
361 ret
= dev
->bus
->probe(dev
);
364 } else if (drv
->probe
) {
365 ret
= drv
->probe(dev
);
370 pinctrl_init_done(dev
);
372 if (dev
->pm_domain
&& dev
->pm_domain
->sync
)
373 dev
->pm_domain
->sync(dev
);
377 pr_debug("bus: '%s': %s: bound device %s to driver %s\n",
378 drv
->bus
->name
, __func__
, dev_name(dev
), drv
->name
);
383 blocking_notifier_call_chain(&dev
->bus
->p
->bus_notifier
,
384 BUS_NOTIFY_DRIVER_NOT_BOUND
, dev
);
386 devres_release_all(dev
);
387 driver_sysfs_remove(dev
);
389 dev_set_drvdata(dev
, NULL
);
390 if (dev
->pm_domain
&& dev
->pm_domain
->dismiss
)
391 dev
->pm_domain
->dismiss(dev
);
392 pm_runtime_reinit(dev
);
396 /* Driver requested deferred probing */
397 dev_dbg(dev
, "Driver %s requests probe deferral\n", drv
->name
);
398 driver_deferred_probe_add(dev
);
399 /* Did a trigger occur while probing? Need to re-trigger if yes */
400 if (local_trigger_count
!= atomic_read(&deferred_trigger_count
))
401 driver_deferred_probe_trigger();
405 pr_debug("%s: probe of %s rejects match %d\n",
406 drv
->name
, dev_name(dev
), ret
);
409 /* driver matched but the probe failed */
411 "%s: probe of %s failed with error %d\n",
412 drv
->name
, dev_name(dev
), ret
);
415 * Ignore errors returned by ->probe so that the next driver can try
420 atomic_dec(&probe_count
);
421 wake_up(&probe_waitqueue
);
427 * Determine if the probe sequence is finished or not.
429 * Should somehow figure out how to use a semaphore, not an atomic variable...
431 int driver_probe_done(void)
433 pr_debug("%s: probe_count = %d\n", __func__
,
434 atomic_read(&probe_count
));
435 if (atomic_read(&probe_count
))
441 * wait_for_device_probe
442 * Wait for device probing to be completed.
444 void wait_for_device_probe(void)
446 /* wait for the deferred probe workqueue to finish */
447 if (driver_deferred_probe_enable
)
448 flush_workqueue(deferred_wq
);
450 /* wait for the known devices to complete their probing */
451 wait_event(probe_waitqueue
, atomic_read(&probe_count
) == 0);
452 async_synchronize_full();
454 EXPORT_SYMBOL_GPL(wait_for_device_probe
);
457 * driver_probe_device - attempt to bind device & driver together
458 * @drv: driver to bind a device to
459 * @dev: device to try to bind to the driver
461 * This function returns -ENODEV if the device is not registered,
462 * 1 if the device is bound successfully and 0 otherwise.
464 * This function must be called with @dev lock held. When called for a
465 * USB interface, @dev->parent lock must be held as well.
467 * If the device has a parent, runtime-resume the parent before driver probing.
469 int driver_probe_device(struct device_driver
*drv
, struct device
*dev
)
473 if (!device_is_registered(dev
))
476 pr_debug("bus: '%s': %s: matched device %s with driver %s\n",
477 drv
->bus
->name
, __func__
, dev_name(dev
), drv
->name
);
480 pm_runtime_get_sync(dev
->parent
);
482 pm_runtime_barrier(dev
);
483 ret
= really_probe(dev
, drv
);
484 pm_request_idle(dev
);
487 pm_runtime_put(dev
->parent
);
492 bool driver_allows_async_probing(struct device_driver
*drv
)
494 switch (drv
->probe_type
) {
495 case PROBE_PREFER_ASYNCHRONOUS
:
498 case PROBE_FORCE_SYNCHRONOUS
:
502 if (module_requested_async_probing(drv
->owner
))
509 struct device_attach_data
{
513 * Indicates whether we are are considering asynchronous probing or
514 * not. Only initial binding after device or driver registration
515 * (including deferral processing) may be done asynchronously, the
516 * rest is always synchronous, as we expect it is being done by
517 * request from userspace.
522 * Indicates if we are binding synchronous or asynchronous drivers.
523 * When asynchronous probing is enabled we'll execute 2 passes
524 * over drivers: first pass doing synchronous probing and second
525 * doing asynchronous probing (if synchronous did not succeed -
526 * most likely because there was no driver requiring synchronous
527 * probing - and we found asynchronous driver during first pass).
528 * The 2 passes are done because we can't shoot asynchronous
529 * probe for given device and driver from bus_for_each_drv() since
530 * driver pointer is not guaranteed to stay valid once
531 * bus_for_each_drv() iterates to the next driver on the bus.
536 * We'll set have_async to 'true' if, while scanning for matching
537 * driver, we'll encounter one that requests asynchronous probing.
542 static int __device_attach_driver(struct device_driver
*drv
, void *_data
)
544 struct device_attach_data
*data
= _data
;
545 struct device
*dev
= data
->dev
;
549 * Check if device has already been claimed. This may
550 * happen with driver loading, device discovery/registration,
551 * and deferred probe processing happens all at once with
557 if (!driver_match_device(drv
, dev
))
560 async_allowed
= driver_allows_async_probing(drv
);
563 data
->have_async
= true;
565 if (data
->check_async
&& async_allowed
!= data
->want_async
)
568 return driver_probe_device(drv
, dev
);
571 static void __device_attach_async_helper(void *_dev
, async_cookie_t cookie
)
573 struct device
*dev
= _dev
;
574 struct device_attach_data data
= {
583 pm_runtime_get_sync(dev
->parent
);
585 bus_for_each_drv(dev
->bus
, NULL
, &data
, __device_attach_driver
);
586 dev_dbg(dev
, "async probe completed\n");
588 pm_request_idle(dev
);
591 pm_runtime_put(dev
->parent
);
598 static int __device_attach(struct device
*dev
, bool allow_async
)
604 if (klist_node_attached(&dev
->p
->knode_driver
)) {
608 ret
= device_bind_driver(dev
);
616 struct device_attach_data data
= {
618 .check_async
= allow_async
,
623 pm_runtime_get_sync(dev
->parent
);
625 ret
= bus_for_each_drv(dev
->bus
, NULL
, &data
,
626 __device_attach_driver
);
627 if (!ret
&& allow_async
&& data
.have_async
) {
629 * If we could not find appropriate driver
630 * synchronously and we are allowed to do
631 * async probes and there are drivers that
632 * want to probe asynchronously, we'll
635 dev_dbg(dev
, "scheduling asynchronous probe\n");
637 async_schedule(__device_attach_async_helper
, dev
);
639 pm_request_idle(dev
);
643 pm_runtime_put(dev
->parent
);
651 * device_attach - try to attach device to a driver.
654 * Walk the list of drivers that the bus has and call
655 * driver_probe_device() for each pair. If a compatible
656 * pair is found, break out and return.
658 * Returns 1 if the device was bound to a driver;
659 * 0 if no matching driver was found;
660 * -ENODEV if the device is not registered.
662 * When called for a USB interface, @dev->parent lock must be held.
664 int device_attach(struct device
*dev
)
666 return __device_attach(dev
, false);
668 EXPORT_SYMBOL_GPL(device_attach
);
670 void device_initial_probe(struct device
*dev
)
672 __device_attach(dev
, true);
675 static int __driver_attach(struct device
*dev
, void *data
)
677 struct device_driver
*drv
= data
;
680 * Lock device and try to bind to it. We drop the error
681 * here and always return 0, because we need to keep trying
682 * to bind to devices and some drivers will return an error
683 * simply if it didn't support the device.
685 * driver_probe_device() will spit a warning if there
689 if (!driver_match_device(drv
, dev
))
692 if (dev
->parent
) /* Needed for USB */
693 device_lock(dev
->parent
);
696 driver_probe_device(drv
, dev
);
699 device_unlock(dev
->parent
);
705 * driver_attach - try to bind driver to devices.
708 * Walk the list of devices that the bus has on it and try to
709 * match the driver with each one. If driver_probe_device()
710 * returns 0 and the @dev->driver is set, we've found a
713 int driver_attach(struct device_driver
*drv
)
715 return bus_for_each_dev(drv
->bus
, NULL
, drv
, __driver_attach
);
717 EXPORT_SYMBOL_GPL(driver_attach
);
720 * __device_release_driver() must be called with @dev lock held.
721 * When called for a USB interface, @dev->parent lock must be held as well.
723 static void __device_release_driver(struct device
*dev
)
725 struct device_driver
*drv
;
729 if (driver_allows_async_probing(drv
))
730 async_synchronize_full();
732 pm_runtime_get_sync(dev
);
734 driver_sysfs_remove(dev
);
737 blocking_notifier_call_chain(&dev
->bus
->p
->bus_notifier
,
738 BUS_NOTIFY_UNBIND_DRIVER
,
741 pm_runtime_put_sync(dev
);
743 if (dev
->bus
&& dev
->bus
->remove
)
744 dev
->bus
->remove(dev
);
745 else if (drv
->remove
)
747 devres_release_all(dev
);
749 dev_set_drvdata(dev
, NULL
);
750 if (dev
->pm_domain
&& dev
->pm_domain
->dismiss
)
751 dev
->pm_domain
->dismiss(dev
);
752 pm_runtime_reinit(dev
);
754 klist_remove(&dev
->p
->knode_driver
);
756 blocking_notifier_call_chain(&dev
->bus
->p
->bus_notifier
,
757 BUS_NOTIFY_UNBOUND_DRIVER
,
763 * device_release_driver - manually detach device from driver.
766 * Manually detach device from driver.
767 * When called for a USB interface, @dev->parent lock must be held.
769 void device_release_driver(struct device
*dev
)
772 * If anyone calls device_release_driver() recursively from
773 * within their ->remove callback for the same device, they
774 * will deadlock right here.
777 __device_release_driver(dev
);
780 EXPORT_SYMBOL_GPL(device_release_driver
);
783 * driver_detach - detach driver from all devices it controls.
786 void driver_detach(struct device_driver
*drv
)
788 struct device_private
*dev_prv
;
792 spin_lock(&drv
->p
->klist_devices
.k_lock
);
793 if (list_empty(&drv
->p
->klist_devices
.k_list
)) {
794 spin_unlock(&drv
->p
->klist_devices
.k_lock
);
797 dev_prv
= list_entry(drv
->p
->klist_devices
.k_list
.prev
,
798 struct device_private
,
799 knode_driver
.n_node
);
800 dev
= dev_prv
->device
;
802 spin_unlock(&drv
->p
->klist_devices
.k_lock
);
804 if (dev
->parent
) /* Needed for USB */
805 device_lock(dev
->parent
);
807 if (dev
->driver
== drv
)
808 __device_release_driver(dev
);
811 device_unlock(dev
->parent
);