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 * deferred_probe_work_func() - Retry probing devices in the active list.
60 static void deferred_probe_work_func(struct work_struct
*work
)
63 struct device_private
*private;
65 * This block processes every device in the deferred 'active' list.
66 * Each device is removed from the active list and passed to
67 * bus_probe_device() to re-attempt the probe. The loop continues
68 * until every device in the active list is removed and retried.
70 * Note: Once the device is removed from the list and the mutex is
71 * released, it is possible for the device get freed by another thread
72 * and cause a illegal pointer dereference. This code uses
73 * get/put_device() to ensure the device structure cannot disappear
74 * from under our feet.
76 mutex_lock(&deferred_probe_mutex
);
77 while (!list_empty(&deferred_probe_active_list
)) {
78 private = list_first_entry(&deferred_probe_active_list
,
79 typeof(*dev
->p
), deferred_probe
);
80 dev
= private->device
;
81 list_del_init(&private->deferred_probe
);
86 * Drop the mutex while probing each device; the probe path may
87 * manipulate the deferred list
89 mutex_unlock(&deferred_probe_mutex
);
92 * Force the device to the end of the dpm_list since
93 * the PM code assumes that the order we add things to
94 * the list is a good order for suspend but deferred
95 * probe makes that very unsafe.
98 device_pm_move_last(dev
);
101 dev_dbg(dev
, "Retrying from deferred list\n");
102 bus_probe_device(dev
);
104 mutex_lock(&deferred_probe_mutex
);
108 mutex_unlock(&deferred_probe_mutex
);
110 static DECLARE_WORK(deferred_probe_work
, deferred_probe_work_func
);
112 static void driver_deferred_probe_add(struct device
*dev
)
114 mutex_lock(&deferred_probe_mutex
);
115 if (list_empty(&dev
->p
->deferred_probe
)) {
116 dev_dbg(dev
, "Added to deferred list\n");
117 list_add_tail(&dev
->p
->deferred_probe
, &deferred_probe_pending_list
);
119 mutex_unlock(&deferred_probe_mutex
);
122 void driver_deferred_probe_del(struct device
*dev
)
124 mutex_lock(&deferred_probe_mutex
);
125 if (!list_empty(&dev
->p
->deferred_probe
)) {
126 dev_dbg(dev
, "Removed from deferred list\n");
127 list_del_init(&dev
->p
->deferred_probe
);
129 mutex_unlock(&deferred_probe_mutex
);
132 static bool driver_deferred_probe_enable
= false;
134 * driver_deferred_probe_trigger() - Kick off re-probing deferred devices
136 * This functions moves all devices from the pending list to the active
137 * list and schedules the deferred probe workqueue to process them. It
138 * should be called anytime a driver is successfully bound to a device.
140 * Note, there is a race condition in multi-threaded probe. In the case where
141 * more than one device is probing at the same time, it is possible for one
142 * probe to complete successfully while another is about to defer. If the second
143 * depends on the first, then it will get put on the pending list after the
144 * trigger event has already occured and will be stuck there.
146 * The atomic 'deferred_trigger_count' is used to determine if a successful
147 * trigger has occurred in the midst of probing a driver. If the trigger count
148 * changes in the midst of a probe, then deferred processing should be triggered
151 static void driver_deferred_probe_trigger(void)
153 if (!driver_deferred_probe_enable
)
157 * A successful probe means that all the devices in the pending list
158 * should be triggered to be reprobed. Move all the deferred devices
159 * into the active list so they can be retried by the workqueue
161 mutex_lock(&deferred_probe_mutex
);
162 atomic_inc(&deferred_trigger_count
);
163 list_splice_tail_init(&deferred_probe_pending_list
,
164 &deferred_probe_active_list
);
165 mutex_unlock(&deferred_probe_mutex
);
168 * Kick the re-probe thread. It may already be scheduled, but it is
169 * safe to kick it again.
171 queue_work(deferred_wq
, &deferred_probe_work
);
175 * deferred_probe_initcall() - Enable probing of deferred devices
177 * We don't want to get in the way when the bulk of drivers are getting probed.
178 * Instead, this initcall makes sure that deferred probing is delayed until
179 * late_initcall time.
181 static int deferred_probe_initcall(void)
183 deferred_wq
= create_singlethread_workqueue("deferwq");
184 if (WARN_ON(!deferred_wq
))
187 driver_deferred_probe_enable
= true;
188 driver_deferred_probe_trigger();
189 /* Sort as many dependencies as possible before exiting initcalls */
190 flush_workqueue(deferred_wq
);
193 late_initcall(deferred_probe_initcall
);
195 static void driver_bound(struct device
*dev
)
197 if (klist_node_attached(&dev
->p
->knode_driver
)) {
198 printk(KERN_WARNING
"%s: device %s already bound\n",
199 __func__
, kobject_name(&dev
->kobj
));
203 pr_debug("driver: '%s': %s: bound to device '%s'\n", dev
->driver
->name
,
204 __func__
, dev_name(dev
));
206 klist_add_tail(&dev
->p
->knode_driver
, &dev
->driver
->p
->klist_devices
);
209 * Make sure the device is no longer in one of the deferred lists and
210 * kick off retrying all pending devices
212 driver_deferred_probe_del(dev
);
213 driver_deferred_probe_trigger();
216 blocking_notifier_call_chain(&dev
->bus
->p
->bus_notifier
,
217 BUS_NOTIFY_BOUND_DRIVER
, dev
);
220 static int driver_sysfs_add(struct device
*dev
)
225 blocking_notifier_call_chain(&dev
->bus
->p
->bus_notifier
,
226 BUS_NOTIFY_BIND_DRIVER
, dev
);
228 ret
= sysfs_create_link(&dev
->driver
->p
->kobj
, &dev
->kobj
,
229 kobject_name(&dev
->kobj
));
231 ret
= sysfs_create_link(&dev
->kobj
, &dev
->driver
->p
->kobj
,
234 sysfs_remove_link(&dev
->driver
->p
->kobj
,
235 kobject_name(&dev
->kobj
));
240 static void driver_sysfs_remove(struct device
*dev
)
242 struct device_driver
*drv
= dev
->driver
;
245 sysfs_remove_link(&drv
->p
->kobj
, kobject_name(&dev
->kobj
));
246 sysfs_remove_link(&dev
->kobj
, "driver");
251 * device_bind_driver - bind a driver to one device.
254 * Allow manual attachment of a driver to a device.
255 * Caller must have already set @dev->driver.
257 * Note that this does not modify the bus reference count
258 * nor take the bus's rwsem. Please verify those are accounted
259 * for before calling this. (It is ok to call with no other effort
260 * from a driver's probe() method.)
262 * This function must be called with the device lock held.
264 int device_bind_driver(struct device
*dev
)
268 ret
= driver_sysfs_add(dev
);
273 EXPORT_SYMBOL_GPL(device_bind_driver
);
275 static atomic_t probe_count
= ATOMIC_INIT(0);
276 static DECLARE_WAIT_QUEUE_HEAD(probe_waitqueue
);
278 static int really_probe(struct device
*dev
, struct device_driver
*drv
)
281 int local_trigger_count
= atomic_read(&deferred_trigger_count
);
283 atomic_inc(&probe_count
);
284 pr_debug("bus: '%s': %s: probing driver %s with device %s\n",
285 drv
->bus
->name
, __func__
, drv
->name
, dev_name(dev
));
286 WARN_ON(!list_empty(&dev
->devres_head
));
290 /* If using pinctrl, bind pins now before probing */
291 ret
= pinctrl_bind_pins(dev
);
295 if (driver_sysfs_add(dev
)) {
296 printk(KERN_ERR
"%s: driver_sysfs_add(%s) failed\n",
297 __func__
, dev_name(dev
));
301 if (dev
->bus
->probe
) {
302 ret
= dev
->bus
->probe(dev
);
305 } else if (drv
->probe
) {
306 ret
= drv
->probe(dev
);
313 pr_debug("bus: '%s': %s: bound device %s to driver %s\n",
314 drv
->bus
->name
, __func__
, dev_name(dev
), drv
->name
);
318 devres_release_all(dev
);
319 driver_sysfs_remove(dev
);
321 dev_set_drvdata(dev
, NULL
);
325 /* Driver requested deferred probing */
326 dev_dbg(dev
, "Driver %s requests probe deferral\n", drv
->name
);
327 driver_deferred_probe_add(dev
);
328 /* Did a trigger occur while probing? Need to re-trigger if yes */
329 if (local_trigger_count
!= atomic_read(&deferred_trigger_count
))
330 driver_deferred_probe_trigger();
334 pr_debug("%s: probe of %s rejects match %d\n",
335 drv
->name
, dev_name(dev
), ret
);
338 /* driver matched but the probe failed */
340 "%s: probe of %s failed with error %d\n",
341 drv
->name
, dev_name(dev
), ret
);
344 * Ignore errors returned by ->probe so that the next driver can try
349 atomic_dec(&probe_count
);
350 wake_up(&probe_waitqueue
);
356 * Determine if the probe sequence is finished or not.
358 * Should somehow figure out how to use a semaphore, not an atomic variable...
360 int driver_probe_done(void)
362 pr_debug("%s: probe_count = %d\n", __func__
,
363 atomic_read(&probe_count
));
364 if (atomic_read(&probe_count
))
370 * wait_for_device_probe
371 * Wait for device probing to be completed.
373 void wait_for_device_probe(void)
375 /* wait for the known devices to complete their probing */
376 wait_event(probe_waitqueue
, atomic_read(&probe_count
) == 0);
377 async_synchronize_full();
379 EXPORT_SYMBOL_GPL(wait_for_device_probe
);
382 * driver_probe_device - attempt to bind device & driver together
383 * @drv: driver to bind a device to
384 * @dev: device to try to bind to the driver
386 * This function returns -ENODEV if the device is not registered,
387 * 1 if the device is bound successfully and 0 otherwise.
389 * This function must be called with @dev lock held. When called for a
390 * USB interface, @dev->parent lock must be held as well.
392 int driver_probe_device(struct device_driver
*drv
, struct device
*dev
)
396 if (!device_is_registered(dev
))
399 pr_debug("bus: '%s': %s: matched device %s with driver %s\n",
400 drv
->bus
->name
, __func__
, dev_name(dev
), drv
->name
);
402 pm_runtime_barrier(dev
);
403 ret
= really_probe(dev
, drv
);
404 pm_request_idle(dev
);
409 static int __device_attach(struct device_driver
*drv
, void *data
)
411 struct device
*dev
= data
;
413 if (!driver_match_device(drv
, dev
))
416 return driver_probe_device(drv
, dev
);
420 * device_attach - try to attach device to a driver.
423 * Walk the list of drivers that the bus has and call
424 * driver_probe_device() for each pair. If a compatible
425 * pair is found, break out and return.
427 * Returns 1 if the device was bound to a driver;
428 * 0 if no matching driver was found;
429 * -ENODEV if the device is not registered.
431 * When called for a USB interface, @dev->parent lock must be held.
433 int device_attach(struct device
*dev
)
439 if (klist_node_attached(&dev
->p
->knode_driver
)) {
443 ret
= device_bind_driver(dev
);
451 ret
= bus_for_each_drv(dev
->bus
, NULL
, dev
, __device_attach
);
452 pm_request_idle(dev
);
458 EXPORT_SYMBOL_GPL(device_attach
);
460 static int __driver_attach(struct device
*dev
, void *data
)
462 struct device_driver
*drv
= data
;
465 * Lock device and try to bind to it. We drop the error
466 * here and always return 0, because we need to keep trying
467 * to bind to devices and some drivers will return an error
468 * simply if it didn't support the device.
470 * driver_probe_device() will spit a warning if there
474 if (!driver_match_device(drv
, dev
))
477 if (dev
->parent
) /* Needed for USB */
478 device_lock(dev
->parent
);
481 driver_probe_device(drv
, dev
);
484 device_unlock(dev
->parent
);
490 * driver_attach - try to bind driver to devices.
493 * Walk the list of devices that the bus has on it and try to
494 * match the driver with each one. If driver_probe_device()
495 * returns 0 and the @dev->driver is set, we've found a
498 int driver_attach(struct device_driver
*drv
)
500 return bus_for_each_dev(drv
->bus
, NULL
, drv
, __driver_attach
);
502 EXPORT_SYMBOL_GPL(driver_attach
);
505 * __device_release_driver() must be called with @dev lock held.
506 * When called for a USB interface, @dev->parent lock must be held as well.
508 static void __device_release_driver(struct device
*dev
)
510 struct device_driver
*drv
;
514 pm_runtime_get_sync(dev
);
516 driver_sysfs_remove(dev
);
519 blocking_notifier_call_chain(&dev
->bus
->p
->bus_notifier
,
520 BUS_NOTIFY_UNBIND_DRIVER
,
523 pm_runtime_put_sync(dev
);
525 if (dev
->bus
&& dev
->bus
->remove
)
526 dev
->bus
->remove(dev
);
527 else if (drv
->remove
)
529 devres_release_all(dev
);
531 dev_set_drvdata(dev
, NULL
);
532 klist_remove(&dev
->p
->knode_driver
);
534 blocking_notifier_call_chain(&dev
->bus
->p
->bus_notifier
,
535 BUS_NOTIFY_UNBOUND_DRIVER
,
542 * device_release_driver - manually detach device from driver.
545 * Manually detach device from driver.
546 * When called for a USB interface, @dev->parent lock must be held.
548 void device_release_driver(struct device
*dev
)
551 * If anyone calls device_release_driver() recursively from
552 * within their ->remove callback for the same device, they
553 * will deadlock right here.
556 __device_release_driver(dev
);
559 EXPORT_SYMBOL_GPL(device_release_driver
);
562 * driver_detach - detach driver from all devices it controls.
565 void driver_detach(struct device_driver
*drv
)
567 struct device_private
*dev_prv
;
571 spin_lock(&drv
->p
->klist_devices
.k_lock
);
572 if (list_empty(&drv
->p
->klist_devices
.k_list
)) {
573 spin_unlock(&drv
->p
->klist_devices
.k_lock
);
576 dev_prv
= list_entry(drv
->p
->klist_devices
.k_list
.prev
,
577 struct device_private
,
578 knode_driver
.n_node
);
579 dev
= dev_prv
->device
;
581 spin_unlock(&drv
->p
->klist_devices
.k_lock
);
583 if (dev
->parent
) /* Needed for USB */
584 device_lock(dev
->parent
);
586 if (dev
->driver
== drv
)
587 __device_release_driver(dev
);
590 device_unlock(dev
->parent
);