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/module.h>
23 #include <linux/kthread.h>
24 #include <linux/wait.h>
25 #include <linux/async.h>
26 #include <linux/pm_runtime.h>
27
28 #include "base.h"
29 #include "power/power.h"
30
31 /*
32 * Deferred Probe infrastructure.
33 *
34 * Sometimes driver probe order matters, but the kernel doesn't always have
35 * dependency information which means some drivers will get probed before a
36 * resource it depends on is available. For example, an SDHCI driver may
37 * first need a GPIO line from an i2c GPIO controller before it can be
38 * initialized. If a required resource is not available yet, a driver can
39 * request probing to be deferred by returning -EPROBE_DEFER from its probe hook
40 *
41 * Deferred probe maintains two lists of devices, a pending list and an active
42 * list. A driver returning -EPROBE_DEFER causes the device to be added to the
43 * pending list. A successful driver probe will trigger moving all devices
44 * from the pending to the active list so that the workqueue will eventually
45 * retry them.
46 *
47 * The deferred_probe_mutex must be held any time the deferred_probe_*_list
48 * of the (struct device*)->p->deferred_probe pointers are manipulated
49 */
50 static DEFINE_MUTEX(deferred_probe_mutex);
51 static LIST_HEAD(deferred_probe_pending_list);
52 static LIST_HEAD(deferred_probe_active_list);
53 static struct workqueue_struct *deferred_wq;
54 static atomic_t deferred_trigger_count = ATOMIC_INIT(0);
55
56 /**
57 * deferred_probe_work_func() - Retry probing devices in the active list.
58 */
deferred_probe_work_func(struct work_struct * work)59 static void deferred_probe_work_func(struct work_struct *work)
60 {
61 struct device *dev;
62 struct device_private *private;
63 /*
64 * This block processes every device in the deferred 'active' list.
65 * Each device is removed from the active list and passed to
66 * bus_probe_device() to re-attempt the probe. The loop continues
67 * until every device in the active list is removed and retried.
68 *
69 * Note: Once the device is removed from the list and the mutex is
70 * released, it is possible for the device get freed by another thread
71 * and cause a illegal pointer dereference. This code uses
72 * get/put_device() to ensure the device structure cannot disappear
73 * from under our feet.
74 */
75 mutex_lock(&deferred_probe_mutex);
76 while (!list_empty(&deferred_probe_active_list)) {
77 private = list_first_entry(&deferred_probe_active_list,
78 typeof(*dev->p), deferred_probe);
79 dev = private->device;
80 list_del_init(&private->deferred_probe);
81
82 get_device(dev);
83
84 /*
85 * Drop the mutex while probing each device; the probe path may
86 * manipulate the deferred list
87 */
88 mutex_unlock(&deferred_probe_mutex);
89 dev_dbg(dev, "Retrying from deferred list\n");
90 bus_probe_device(dev);
91 mutex_lock(&deferred_probe_mutex);
92
93 put_device(dev);
94 }
95 mutex_unlock(&deferred_probe_mutex);
96 }
97 static DECLARE_WORK(deferred_probe_work, deferred_probe_work_func);
98
driver_deferred_probe_add(struct device * dev)99 static void driver_deferred_probe_add(struct device *dev)
100 {
101 mutex_lock(&deferred_probe_mutex);
102 if (list_empty(&dev->p->deferred_probe)) {
103 dev_dbg(dev, "Added to deferred list\n");
104 list_add(&dev->p->deferred_probe, &deferred_probe_pending_list);
105 }
106 mutex_unlock(&deferred_probe_mutex);
107 }
108
driver_deferred_probe_del(struct device * dev)109 void driver_deferred_probe_del(struct device *dev)
110 {
111 mutex_lock(&deferred_probe_mutex);
112 if (!list_empty(&dev->p->deferred_probe)) {
113 dev_dbg(dev, "Removed from deferred list\n");
114 list_del_init(&dev->p->deferred_probe);
115 }
116 mutex_unlock(&deferred_probe_mutex);
117 }
118
119 static bool driver_deferred_probe_enable = false;
120 /**
121 * driver_deferred_probe_trigger() - Kick off re-probing deferred devices
122 *
123 * This functions moves all devices from the pending list to the active
124 * list and schedules the deferred probe workqueue to process them. It
125 * should be called anytime a driver is successfully bound to a device.
126 *
127 * Note, there is a race condition in multi-threaded probe. In the case where
128 * more than one device is probing at the same time, it is possible for one
129 * probe to complete successfully while another is about to defer. If the second
130 * depends on the first, then it will get put on the pending list after the
131 * trigger event has already occured and will be stuck there.
132 *
133 * The atomic 'deferred_trigger_count' is used to determine if a successful
134 * trigger has occurred in the midst of probing a driver. If the trigger count
135 * changes in the midst of a probe, then deferred processing should be triggered
136 * again.
137 */
driver_deferred_probe_trigger(void)138 static void driver_deferred_probe_trigger(void)
139 {
140 if (!driver_deferred_probe_enable)
141 return;
142
143 /*
144 * A successful probe means that all the devices in the pending list
145 * should be triggered to be reprobed. Move all the deferred devices
146 * into the active list so they can be retried by the workqueue
147 */
148 mutex_lock(&deferred_probe_mutex);
149 atomic_inc(&deferred_trigger_count);
150 list_splice_tail_init(&deferred_probe_pending_list,
151 &deferred_probe_active_list);
152 mutex_unlock(&deferred_probe_mutex);
153
154 /*
155 * Kick the re-probe thread. It may already be scheduled, but it is
156 * safe to kick it again.
157 */
158 queue_work(deferred_wq, &deferred_probe_work);
159 }
160
161 /**
162 * deferred_probe_initcall() - Enable probing of deferred devices
163 *
164 * We don't want to get in the way when the bulk of drivers are getting probed.
165 * Instead, this initcall makes sure that deferred probing is delayed until
166 * late_initcall time.
167 */
deferred_probe_initcall(void)168 static int deferred_probe_initcall(void)
169 {
170 deferred_wq = create_singlethread_workqueue("deferwq");
171 if (WARN_ON(!deferred_wq))
172 return -ENOMEM;
173
174 driver_deferred_probe_enable = true;
175 driver_deferred_probe_trigger();
176 /* Sort as many dependencies as possible before exiting initcalls */
177 flush_workqueue(deferred_wq);
178 return 0;
179 }
180 late_initcall(deferred_probe_initcall);
181
driver_bound(struct device * dev)182 static void driver_bound(struct device *dev)
183 {
184 if (klist_node_attached(&dev->p->knode_driver)) {
185 printk(KERN_WARNING "%s: device %s already bound\n",
186 __func__, kobject_name(&dev->kobj));
187 return;
188 }
189
190 pr_debug("driver: '%s': %s: bound to device '%s'\n", dev_name(dev),
191 __func__, dev->driver->name);
192
193 klist_add_tail(&dev->p->knode_driver, &dev->driver->p->klist_devices);
194
195 /*
196 * Make sure the device is no longer in one of the deferred lists and
197 * kick off retrying all pending devices
198 */
199 driver_deferred_probe_del(dev);
200 driver_deferred_probe_trigger();
201
202 if (dev->bus)
203 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
204 BUS_NOTIFY_BOUND_DRIVER, dev);
205 }
206
driver_sysfs_add(struct device * dev)207 static int driver_sysfs_add(struct device *dev)
208 {
209 int ret;
210
211 if (dev->bus)
212 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
213 BUS_NOTIFY_BIND_DRIVER, dev);
214
215 ret = sysfs_create_link(&dev->driver->p->kobj, &dev->kobj,
216 kobject_name(&dev->kobj));
217 if (ret == 0) {
218 ret = sysfs_create_link(&dev->kobj, &dev->driver->p->kobj,
219 "driver");
220 if (ret)
221 sysfs_remove_link(&dev->driver->p->kobj,
222 kobject_name(&dev->kobj));
223 }
224 return ret;
225 }
226
driver_sysfs_remove(struct device * dev)227 static void driver_sysfs_remove(struct device *dev)
228 {
229 struct device_driver *drv = dev->driver;
230
231 if (drv) {
232 sysfs_remove_link(&drv->p->kobj, kobject_name(&dev->kobj));
233 sysfs_remove_link(&dev->kobj, "driver");
234 }
235 }
236
237 /**
238 * device_bind_driver - bind a driver to one device.
239 * @dev: device.
240 *
241 * Allow manual attachment of a driver to a device.
242 * Caller must have already set @dev->driver.
243 *
244 * Note that this does not modify the bus reference count
245 * nor take the bus's rwsem. Please verify those are accounted
246 * for before calling this. (It is ok to call with no other effort
247 * from a driver's probe() method.)
248 *
249 * This function must be called with the device lock held.
250 */
device_bind_driver(struct device * dev)251 int device_bind_driver(struct device *dev)
252 {
253 int ret;
254
255 ret = driver_sysfs_add(dev);
256 if (!ret)
257 driver_bound(dev);
258 return ret;
259 }
260 EXPORT_SYMBOL_GPL(device_bind_driver);
261
262 static atomic_t probe_count = ATOMIC_INIT(0);
263 static DECLARE_WAIT_QUEUE_HEAD(probe_waitqueue);
264
really_probe(struct device * dev,struct device_driver * drv)265 static int really_probe(struct device *dev, struct device_driver *drv)
266 {
267 int ret = 0;
268 int local_trigger_count = atomic_read(&deferred_trigger_count);
269
270 atomic_inc(&probe_count);
271 pr_debug("bus: '%s': %s: probing driver %s with device %s\n",
272 drv->bus->name, __func__, drv->name, dev_name(dev));
273 WARN_ON(!list_empty(&dev->devres_head));
274
275 dev->driver = drv;
276 if (driver_sysfs_add(dev)) {
277 printk(KERN_ERR "%s: driver_sysfs_add(%s) failed\n",
278 __func__, dev_name(dev));
279 goto probe_failed;
280 }
281
282 if (dev->bus->probe) {
283 ret = dev->bus->probe(dev);
284 if (ret)
285 goto probe_failed;
286 } else if (drv->probe) {
287 ret = drv->probe(dev);
288 if (ret)
289 goto probe_failed;
290 }
291
292 driver_bound(dev);
293 ret = 1;
294 pr_debug("bus: '%s': %s: bound device %s to driver %s\n",
295 drv->bus->name, __func__, dev_name(dev), drv->name);
296 goto done;
297
298 probe_failed:
299 devres_release_all(dev);
300 driver_sysfs_remove(dev);
301 dev->driver = NULL;
302
303 if (ret == -EPROBE_DEFER) {
304 /* Driver requested deferred probing */
305 dev_info(dev, "Driver %s requests probe deferral\n", drv->name);
306 driver_deferred_probe_add(dev);
307 /* Did a trigger occur while probing? Need to re-trigger if yes */
308 if (local_trigger_count != atomic_read(&deferred_trigger_count))
309 driver_deferred_probe_trigger();
310 } else if (ret != -ENODEV && ret != -ENXIO) {
311 /* driver matched but the probe failed */
312 printk(KERN_WARNING
313 "%s: probe of %s failed with error %d\n",
314 drv->name, dev_name(dev), ret);
315 } else {
316 pr_debug("%s: probe of %s rejects match %d\n",
317 drv->name, dev_name(dev), ret);
318 }
319 /*
320 * Ignore errors returned by ->probe so that the next driver can try
321 * its luck.
322 */
323 ret = 0;
324 done:
325 atomic_dec(&probe_count);
326 wake_up(&probe_waitqueue);
327 return ret;
328 }
329
330 /**
331 * driver_probe_done
332 * Determine if the probe sequence is finished or not.
333 *
334 * Should somehow figure out how to use a semaphore, not an atomic variable...
335 */
driver_probe_done(void)336 int driver_probe_done(void)
337 {
338 pr_debug("%s: probe_count = %d\n", __func__,
339 atomic_read(&probe_count));
340 if (atomic_read(&probe_count))
341 return -EBUSY;
342 return 0;
343 }
344
345 /**
346 * wait_for_device_probe
347 * Wait for device probing to be completed.
348 */
wait_for_device_probe(void)349 void wait_for_device_probe(void)
350 {
351 /* wait for the known devices to complete their probing */
352 wait_event(probe_waitqueue, atomic_read(&probe_count) == 0);
353 async_synchronize_full();
354 }
355 EXPORT_SYMBOL_GPL(wait_for_device_probe);
356
357 /**
358 * driver_probe_device - attempt to bind device & driver together
359 * @drv: driver to bind a device to
360 * @dev: device to try to bind to the driver
361 *
362 * This function returns -ENODEV if the device is not registered,
363 * 1 if the device is bound successfully and 0 otherwise.
364 *
365 * This function must be called with @dev lock held. When called for a
366 * USB interface, @dev->parent lock must be held as well.
367 */
driver_probe_device(struct device_driver * drv,struct device * dev)368 int driver_probe_device(struct device_driver *drv, struct device *dev)
369 {
370 int ret = 0;
371
372 if (!device_is_registered(dev))
373 return -ENODEV;
374
375 pr_debug("bus: '%s': %s: matched device %s with driver %s\n",
376 drv->bus->name, __func__, dev_name(dev), drv->name);
377
378 pm_runtime_get_noresume(dev);
379 pm_runtime_barrier(dev);
380 ret = really_probe(dev, drv);
381 pm_runtime_put_sync(dev);
382
383 return ret;
384 }
385
__device_attach(struct device_driver * drv,void * data)386 static int __device_attach(struct device_driver *drv, void *data)
387 {
388 struct device *dev = data;
389
390 if (!driver_match_device(drv, dev))
391 return 0;
392
393 return driver_probe_device(drv, dev);
394 }
395
396 /**
397 * device_attach - try to attach device to a driver.
398 * @dev: device.
399 *
400 * Walk the list of drivers that the bus has and call
401 * driver_probe_device() for each pair. If a compatible
402 * pair is found, break out and return.
403 *
404 * Returns 1 if the device was bound to a driver;
405 * 0 if no matching driver was found;
406 * -ENODEV if the device is not registered.
407 *
408 * When called for a USB interface, @dev->parent lock must be held.
409 */
device_attach(struct device * dev)410 int device_attach(struct device *dev)
411 {
412 int ret = 0;
413
414 device_lock(dev);
415 if (dev->driver) {
416 if (klist_node_attached(&dev->p->knode_driver)) {
417 ret = 1;
418 goto out_unlock;
419 }
420 ret = device_bind_driver(dev);
421 if (ret == 0)
422 ret = 1;
423 else {
424 dev->driver = NULL;
425 ret = 0;
426 }
427 } else {
428 pm_runtime_get_noresume(dev);
429 ret = bus_for_each_drv(dev->bus, NULL, dev, __device_attach);
430 pm_runtime_put_sync(dev);
431 }
432 out_unlock:
433 device_unlock(dev);
434 return ret;
435 }
436 EXPORT_SYMBOL_GPL(device_attach);
437
__driver_attach(struct device * dev,void * data)438 static int __driver_attach(struct device *dev, void *data)
439 {
440 struct device_driver *drv = data;
441
442 /*
443 * Lock device and try to bind to it. We drop the error
444 * here and always return 0, because we need to keep trying
445 * to bind to devices and some drivers will return an error
446 * simply if it didn't support the device.
447 *
448 * driver_probe_device() will spit a warning if there
449 * is an error.
450 */
451
452 if (!driver_match_device(drv, dev))
453 return 0;
454
455 if (dev->parent) /* Needed for USB */
456 device_lock(dev->parent);
457 device_lock(dev);
458 if (!dev->driver)
459 driver_probe_device(drv, dev);
460 device_unlock(dev);
461 if (dev->parent)
462 device_unlock(dev->parent);
463
464 return 0;
465 }
466
467 /**
468 * driver_attach - try to bind driver to devices.
469 * @drv: driver.
470 *
471 * Walk the list of devices that the bus has on it and try to
472 * match the driver with each one. If driver_probe_device()
473 * returns 0 and the @dev->driver is set, we've found a
474 * compatible pair.
475 */
driver_attach(struct device_driver * drv)476 int driver_attach(struct device_driver *drv)
477 {
478 return bus_for_each_dev(drv->bus, NULL, drv, __driver_attach);
479 }
480 EXPORT_SYMBOL_GPL(driver_attach);
481
482 /*
483 * __device_release_driver() must be called with @dev lock held.
484 * When called for a USB interface, @dev->parent lock must be held as well.
485 */
__device_release_driver(struct device * dev)486 static void __device_release_driver(struct device *dev)
487 {
488 struct device_driver *drv;
489
490 drv = dev->driver;
491 if (drv) {
492 pm_runtime_get_sync(dev);
493
494 driver_sysfs_remove(dev);
495
496 if (dev->bus)
497 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
498 BUS_NOTIFY_UNBIND_DRIVER,
499 dev);
500
501 pm_runtime_put_sync(dev);
502
503 if (dev->bus && dev->bus->remove)
504 dev->bus->remove(dev);
505 else if (drv->remove)
506 drv->remove(dev);
507 devres_release_all(dev);
508 dev->driver = NULL;
509 klist_remove(&dev->p->knode_driver);
510 if (dev->bus)
511 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
512 BUS_NOTIFY_UNBOUND_DRIVER,
513 dev);
514
515 }
516 }
517
518 /**
519 * device_release_driver - manually detach device from driver.
520 * @dev: device.
521 *
522 * Manually detach device from driver.
523 * When called for a USB interface, @dev->parent lock must be held.
524 */
device_release_driver(struct device * dev)525 void device_release_driver(struct device *dev)
526 {
527 /*
528 * If anyone calls device_release_driver() recursively from
529 * within their ->remove callback for the same device, they
530 * will deadlock right here.
531 */
532 device_lock(dev);
533 __device_release_driver(dev);
534 device_unlock(dev);
535 }
536 EXPORT_SYMBOL_GPL(device_release_driver);
537
538 /**
539 * driver_detach - detach driver from all devices it controls.
540 * @drv: driver.
541 */
driver_detach(struct device_driver * drv)542 void driver_detach(struct device_driver *drv)
543 {
544 struct device_private *dev_prv;
545 struct device *dev;
546
547 for (;;) {
548 spin_lock(&drv->p->klist_devices.k_lock);
549 if (list_empty(&drv->p->klist_devices.k_list)) {
550 spin_unlock(&drv->p->klist_devices.k_lock);
551 break;
552 }
553 dev_prv = list_entry(drv->p->klist_devices.k_list.prev,
554 struct device_private,
555 knode_driver.n_node);
556 dev = dev_prv->device;
557 get_device(dev);
558 spin_unlock(&drv->p->klist_devices.k_lock);
559
560 if (dev->parent) /* Needed for USB */
561 device_lock(dev->parent);
562 device_lock(dev);
563 if (dev->driver == drv)
564 __device_release_driver(dev);
565 device_unlock(dev);
566 if (dev->parent)
567 device_unlock(dev->parent);
568 put_device(dev);
569 }
570 }
571
572 /*
573 * These exports can't be _GPL due to .h files using this within them, and it
574 * might break something that was previously working...
575 */
dev_get_drvdata(const struct device * dev)576 void *dev_get_drvdata(const struct device *dev)
577 {
578 if (dev && dev->p)
579 return dev->p->driver_data;
580 return NULL;
581 }
582 EXPORT_SYMBOL(dev_get_drvdata);
583
dev_set_drvdata(struct device * dev,void * data)584 int dev_set_drvdata(struct device *dev, void *data)
585 {
586 int error;
587
588 if (!dev->p) {
589 error = device_private_init(dev);
590 if (error)
591 return error;
592 }
593 dev->p->driver_data = data;
594 return 0;
595 }
596 EXPORT_SYMBOL(dev_set_drvdata);
597