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dd.c
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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 <[email protected]>
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 
58 static void deferred_probe_work_func(struct work_struct *work)
59 {
60  struct device *dev;
61  struct device_private *private;
62  /*
63  * This block processes every device in the deferred 'active' list.
64  * Each device is removed from the active list and passed to
65  * bus_probe_device() to re-attempt the probe. The loop continues
66  * until every device in the active list is removed and retried.
67  *
68  * Note: Once the device is removed from the list and the mutex is
69  * released, it is possible for the device get freed by another thread
70  * and cause a illegal pointer dereference. This code uses
71  * get/put_device() to ensure the device structure cannot disappear
72  * from under our feet.
73  */
74  mutex_lock(&deferred_probe_mutex);
75  while (!list_empty(&deferred_probe_active_list)) {
76  private = list_first_entry(&deferred_probe_active_list,
77  typeof(*dev->p), deferred_probe);
78  dev = private->device;
79  list_del_init(&private->deferred_probe);
80 
81  get_device(dev);
82 
83  /*
84  * Drop the mutex while probing each device; the probe path may
85  * manipulate the deferred list
86  */
87  mutex_unlock(&deferred_probe_mutex);
88 
89  /*
90  * Force the device to the end of the dpm_list since
91  * the PM code assumes that the order we add things to
92  * the list is a good order for suspend but deferred
93  * probe makes that very unsafe.
94  */
98 
99  dev_dbg(dev, "Retrying from deferred list\n");
100  bus_probe_device(dev);
101 
102  mutex_lock(&deferred_probe_mutex);
103 
104  put_device(dev);
105  }
106  mutex_unlock(&deferred_probe_mutex);
107 }
108 static DECLARE_WORK(deferred_probe_work, deferred_probe_work_func);
109 
110 static void driver_deferred_probe_add(struct device *dev)
111 {
112  mutex_lock(&deferred_probe_mutex);
113  if (list_empty(&dev->p->deferred_probe)) {
114  dev_dbg(dev, "Added to deferred list\n");
115  list_add_tail(&dev->p->deferred_probe, &deferred_probe_pending_list);
116  }
117  mutex_unlock(&deferred_probe_mutex);
118 }
119 
121 {
122  mutex_lock(&deferred_probe_mutex);
123  if (!list_empty(&dev->p->deferred_probe)) {
124  dev_dbg(dev, "Removed from deferred list\n");
125  list_del_init(&dev->p->deferred_probe);
126  }
127  mutex_unlock(&deferred_probe_mutex);
128 }
129 
130 static bool driver_deferred_probe_enable = false;
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  list_splice_tail_init(&deferred_probe_pending_list,
150  &deferred_probe_active_list);
151  mutex_unlock(&deferred_probe_mutex);
152 
153  /*
154  * Kick the re-probe thread. It may already be scheduled, but it is
155  * safe to kick it again.
156  */
157  queue_work(deferred_wq, &deferred_probe_work);
158 }
159 
167 static int deferred_probe_initcall(void)
168 {
169  deferred_wq = create_singlethread_workqueue("deferwq");
170  if (WARN_ON(!deferred_wq))
171  return -ENOMEM;
172 
173  driver_deferred_probe_enable = true;
174  driver_deferred_probe_trigger();
175  return 0;
176 }
177 late_initcall(deferred_probe_initcall);
178 
179 static void driver_bound(struct device *dev)
180 {
181  if (klist_node_attached(&dev->p->knode_driver)) {
182  printk(KERN_WARNING "%s: device %s already bound\n",
183  __func__, kobject_name(&dev->kobj));
184  return;
185  }
186 
187  pr_debug("driver: '%s': %s: bound to device '%s'\n", dev_name(dev),
188  __func__, dev->driver->name);
189 
190  klist_add_tail(&dev->p->knode_driver, &dev->driver->p->klist_devices);
191 
192  /*
193  * Make sure the device is no longer in one of the deferred lists and
194  * kick off retrying all pending devices
195  */
197  driver_deferred_probe_trigger();
198 
199  if (dev->bus)
200  blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
202 }
203 
204 static int driver_sysfs_add(struct device *dev)
205 {
206  int ret;
207 
208  if (dev->bus)
209  blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
211 
212  ret = sysfs_create_link(&dev->driver->p->kobj, &dev->kobj,
213  kobject_name(&dev->kobj));
214  if (ret == 0) {
215  ret = sysfs_create_link(&dev->kobj, &dev->driver->p->kobj,
216  "driver");
217  if (ret)
218  sysfs_remove_link(&dev->driver->p->kobj,
219  kobject_name(&dev->kobj));
220  }
221  return ret;
222 }
223 
224 static void driver_sysfs_remove(struct device *dev)
225 {
226  struct device_driver *drv = dev->driver;
227 
228  if (drv) {
229  sysfs_remove_link(&drv->p->kobj, kobject_name(&dev->kobj));
230  sysfs_remove_link(&dev->kobj, "driver");
231  }
232 }
233 
248 int device_bind_driver(struct device *dev)
249 {
250  int ret;
251 
252  ret = driver_sysfs_add(dev);
253  if (!ret)
254  driver_bound(dev);
255  return ret;
256 }
258 
259 static atomic_t probe_count = ATOMIC_INIT(0);
260 static DECLARE_WAIT_QUEUE_HEAD(probe_waitqueue);
261 
262 static int really_probe(struct device *dev, struct device_driver *drv)
263 {
264  int ret = 0;
265 
266  atomic_inc(&probe_count);
267  pr_debug("bus: '%s': %s: probing driver %s with device %s\n",
268  drv->bus->name, __func__, drv->name, dev_name(dev));
269  WARN_ON(!list_empty(&dev->devres_head));
270 
271  dev->driver = drv;
272  if (driver_sysfs_add(dev)) {
273  printk(KERN_ERR "%s: driver_sysfs_add(%s) failed\n",
274  __func__, dev_name(dev));
275  goto probe_failed;
276  }
277 
278  if (dev->bus->probe) {
279  ret = dev->bus->probe(dev);
280  if (ret)
281  goto probe_failed;
282  } else if (drv->probe) {
283  ret = drv->probe(dev);
284  if (ret)
285  goto probe_failed;
286  }
287 
288  driver_bound(dev);
289  ret = 1;
290  pr_debug("bus: '%s': %s: bound device %s to driver %s\n",
291  drv->bus->name, __func__, dev_name(dev), drv->name);
292  goto done;
293 
294 probe_failed:
295  devres_release_all(dev);
296  driver_sysfs_remove(dev);
297  dev->driver = NULL;
298  dev_set_drvdata(dev, NULL);
299 
300  if (ret == -EPROBE_DEFER) {
301  /* Driver requested deferred probing */
302  dev_info(dev, "Driver %s requests probe deferral\n", drv->name);
303  driver_deferred_probe_add(dev);
304  } else if (ret != -ENODEV && ret != -ENXIO) {
305  /* driver matched but the probe failed */
307  "%s: probe of %s failed with error %d\n",
308  drv->name, dev_name(dev), ret);
309  } else {
310  pr_debug("%s: probe of %s rejects match %d\n",
311  drv->name, dev_name(dev), ret);
312  }
313  /*
314  * Ignore errors returned by ->probe so that the next driver can try
315  * its luck.
316  */
317  ret = 0;
318 done:
319  atomic_dec(&probe_count);
320  wake_up(&probe_waitqueue);
321  return ret;
322 }
323 
331 {
332  pr_debug("%s: probe_count = %d\n", __func__,
333  atomic_read(&probe_count));
334  if (atomic_read(&probe_count))
335  return -EBUSY;
336  return 0;
337 }
338 
344 {
345  /* wait for the known devices to complete their probing */
346  wait_event(probe_waitqueue, atomic_read(&probe_count) == 0);
348 }
350 
362 int driver_probe_device(struct device_driver *drv, struct device *dev)
363 {
364  int ret = 0;
365 
366  if (!device_is_registered(dev))
367  return -ENODEV;
368 
369  pr_debug("bus: '%s': %s: matched device %s with driver %s\n",
370  drv->bus->name, __func__, dev_name(dev), drv->name);
371 
372  pm_runtime_barrier(dev);
373  ret = really_probe(dev, drv);
374  pm_runtime_idle(dev);
375 
376  return ret;
377 }
378 
379 static int __device_attach(struct device_driver *drv, void *data)
380 {
381  struct device *dev = data;
382 
383  if (!driver_match_device(drv, dev))
384  return 0;
385 
386  return driver_probe_device(drv, dev);
387 }
388 
403 int device_attach(struct device *dev)
404 {
405  int ret = 0;
406 
407  device_lock(dev);
408  if (dev->driver) {
409  if (klist_node_attached(&dev->p->knode_driver)) {
410  ret = 1;
411  goto out_unlock;
412  }
413  ret = device_bind_driver(dev);
414  if (ret == 0)
415  ret = 1;
416  else {
417  dev->driver = NULL;
418  ret = 0;
419  }
420  } else {
421  ret = bus_for_each_drv(dev->bus, NULL, dev, __device_attach);
422  pm_runtime_idle(dev);
423  }
424 out_unlock:
425  device_unlock(dev);
426  return ret;
427 }
429 
430 static int __driver_attach(struct device *dev, void *data)
431 {
432  struct device_driver *drv = data;
433 
434  /*
435  * Lock device and try to bind to it. We drop the error
436  * here and always return 0, because we need to keep trying
437  * to bind to devices and some drivers will return an error
438  * simply if it didn't support the device.
439  *
440  * driver_probe_device() will spit a warning if there
441  * is an error.
442  */
443 
444  if (!driver_match_device(drv, dev))
445  return 0;
446 
447  if (dev->parent) /* Needed for USB */
448  device_lock(dev->parent);
449  device_lock(dev);
450  if (!dev->driver)
451  driver_probe_device(drv, dev);
452  device_unlock(dev);
453  if (dev->parent)
454  device_unlock(dev->parent);
455 
456  return 0;
457 }
458 
468 int driver_attach(struct device_driver *drv)
469 {
470  return bus_for_each_dev(drv->bus, NULL, drv, __driver_attach);
471 }
473 
474 /*
475  * __device_release_driver() must be called with @dev lock held.
476  * When called for a USB interface, @dev->parent lock must be held as well.
477  */
478 static void __device_release_driver(struct device *dev)
479 {
480  struct device_driver *drv;
481 
482  drv = dev->driver;
483  if (drv) {
484  pm_runtime_get_sync(dev);
485 
486  driver_sysfs_remove(dev);
487 
488  if (dev->bus)
489  blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
491  dev);
492 
493  pm_runtime_put_sync(dev);
494 
495  if (dev->bus && dev->bus->remove)
496  dev->bus->remove(dev);
497  else if (drv->remove)
498  drv->remove(dev);
499  devres_release_all(dev);
500  dev->driver = NULL;
501  dev_set_drvdata(dev, NULL);
502  klist_remove(&dev->p->knode_driver);
503  if (dev->bus)
504  blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
506  dev);
507 
508  }
509 }
510 
518 void device_release_driver(struct device *dev)
519 {
520  /*
521  * If anyone calls device_release_driver() recursively from
522  * within their ->remove callback for the same device, they
523  * will deadlock right here.
524  */
525  device_lock(dev);
526  __device_release_driver(dev);
527  device_unlock(dev);
528 }
530 
535 void driver_detach(struct device_driver *drv)
536 {
537  struct device_private *dev_prv;
538  struct device *dev;
539 
540  for (;;) {
541  spin_lock(&drv->p->klist_devices.k_lock);
542  if (list_empty(&drv->p->klist_devices.k_list)) {
543  spin_unlock(&drv->p->klist_devices.k_lock);
544  break;
545  }
546  dev_prv = list_entry(drv->p->klist_devices.k_list.prev,
547  struct device_private,
548  knode_driver.n_node);
549  dev = dev_prv->device;
550  get_device(dev);
551  spin_unlock(&drv->p->klist_devices.k_lock);
552 
553  if (dev->parent) /* Needed for USB */
554  device_lock(dev->parent);
555  device_lock(dev);
556  if (dev->driver == drv)
557  __device_release_driver(dev);
558  device_unlock(dev);
559  if (dev->parent)
560  device_unlock(dev->parent);
561  put_device(dev);
562  }
563 }
564 
565 /*
566  * These exports can't be _GPL due to .h files using this within them, and it
567  * might break something that was previously working...
568  */
569 void *dev_get_drvdata(const struct device *dev)
570 {
571  if (dev && dev->p)
572  return dev->p->driver_data;
573  return NULL;
574 }
576 
577 int dev_set_drvdata(struct device *dev, void *data)
578 {
579  int error;
580 
581  if (!dev->p) {
582  error = device_private_init(dev);
583  if (error)
584  return error;
585  }
586  dev->p->driver_data = data;
587  return 0;
588 }