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Linux/drivers/base/dd.c

  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 #include <linux/pinctrl/devinfo.h>
 28 
 29 #include "base.h"
 30 #include "power/power.h"
 31 
 32 /*
 33  * Deferred Probe infrastructure.
 34  *
 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
 41  *
 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
 46  * retry them.
 47  *
 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
 50  */
 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);
 56 
 57 /*
 58  * deferred_probe_work_func() - Retry probing devices in the active list.
 59  */
 60 static void deferred_probe_work_func(struct work_struct *work)
 61 {
 62         struct device *dev;
 63         struct device_private *private;
 64         /*
 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.
 69          *
 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.
 75          */
 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);
 82 
 83                 get_device(dev);
 84 
 85                 /*
 86                  * Drop the mutex while probing each device; the probe path may
 87                  * manipulate the deferred list
 88                  */
 89                 mutex_unlock(&deferred_probe_mutex);
 90 
 91                 /*
 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.
 96                  */
 97                 device_pm_lock();
 98                 device_pm_move_last(dev);
 99                 device_pm_unlock();
100 
101                 dev_dbg(dev, "Retrying from deferred list\n");
102                 bus_probe_device(dev);
103 
104                 mutex_lock(&deferred_probe_mutex);
105 
106                 put_device(dev);
107         }
108         mutex_unlock(&deferred_probe_mutex);
109 }
110 static DECLARE_WORK(deferred_probe_work, deferred_probe_work_func);
111 
112 static void driver_deferred_probe_add(struct device *dev)
113 {
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);
118         }
119         mutex_unlock(&deferred_probe_mutex);
120 }
121 
122 void driver_deferred_probe_del(struct device *dev)
123 {
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);
128         }
129         mutex_unlock(&deferred_probe_mutex);
130 }
131 
132 static bool driver_deferred_probe_enable = false;
133 /**
134  * driver_deferred_probe_trigger() - Kick off re-probing deferred devices
135  *
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.
139  *
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.
145  *
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
149  * again.
150  */
151 static void driver_deferred_probe_trigger(void)
152 {
153         if (!driver_deferred_probe_enable)
154                 return;
155 
156         /*
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
160          */
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);
166 
167         /*
168          * Kick the re-probe thread.  It may already be scheduled, but it is
169          * safe to kick it again.
170          */
171         queue_work(deferred_wq, &deferred_probe_work);
172 }
173 
174 /**
175  * deferred_probe_initcall() - Enable probing of deferred devices
176  *
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.
180  */
181 static int deferred_probe_initcall(void)
182 {
183         deferred_wq = create_singlethread_workqueue("deferwq");
184         if (WARN_ON(!deferred_wq))
185                 return -ENOMEM;
186 
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);
191         return 0;
192 }
193 late_initcall(deferred_probe_initcall);
194 
195 static void driver_bound(struct device *dev)
196 {
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));
200                 return;
201         }
202 
203         pr_debug("driver: '%s': %s: bound to device '%s'\n", dev->driver->name,
204                  __func__, dev_name(dev));
205 
206         klist_add_tail(&dev->p->knode_driver, &dev->driver->p->klist_devices);
207 
208         /*
209          * Make sure the device is no longer in one of the deferred lists and
210          * kick off retrying all pending devices
211          */
212         driver_deferred_probe_del(dev);
213         driver_deferred_probe_trigger();
214 
215         if (dev->bus)
216                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
217                                              BUS_NOTIFY_BOUND_DRIVER, dev);
218 }
219 
220 static int driver_sysfs_add(struct device *dev)
221 {
222         int ret;
223 
224         if (dev->bus)
225                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
226                                              BUS_NOTIFY_BIND_DRIVER, dev);
227 
228         ret = sysfs_create_link(&dev->driver->p->kobj, &dev->kobj,
229                           kobject_name(&dev->kobj));
230         if (ret == 0) {
231                 ret = sysfs_create_link(&dev->kobj, &dev->driver->p->kobj,
232                                         "driver");
233                 if (ret)
234                         sysfs_remove_link(&dev->driver->p->kobj,
235                                         kobject_name(&dev->kobj));
236         }
237         return ret;
238 }
239 
240 static void driver_sysfs_remove(struct device *dev)
241 {
242         struct device_driver *drv = dev->driver;
243 
244         if (drv) {
245                 sysfs_remove_link(&drv->p->kobj, kobject_name(&dev->kobj));
246                 sysfs_remove_link(&dev->kobj, "driver");
247         }
248 }
249 
250 /**
251  * device_bind_driver - bind a driver to one device.
252  * @dev: device.
253  *
254  * Allow manual attachment of a driver to a device.
255  * Caller must have already set @dev->driver.
256  *
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.)
261  *
262  * This function must be called with the device lock held.
263  */
264 int device_bind_driver(struct device *dev)
265 {
266         int ret;
267 
268         ret = driver_sysfs_add(dev);
269         if (!ret)
270                 driver_bound(dev);
271         return ret;
272 }
273 EXPORT_SYMBOL_GPL(device_bind_driver);
274 
275 static atomic_t probe_count = ATOMIC_INIT(0);
276 static DECLARE_WAIT_QUEUE_HEAD(probe_waitqueue);
277 
278 static int really_probe(struct device *dev, struct device_driver *drv)
279 {
280         int ret = 0;
281         int local_trigger_count = atomic_read(&deferred_trigger_count);
282 
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));
287 
288         dev->driver = drv;
289 
290         /* If using pinctrl, bind pins now before probing */
291         ret = pinctrl_bind_pins(dev);
292         if (ret)
293                 goto probe_failed;
294 
295         if (driver_sysfs_add(dev)) {
296                 printk(KERN_ERR "%s: driver_sysfs_add(%s) failed\n",
297                         __func__, dev_name(dev));
298                 goto probe_failed;
299         }
300 
301         if (dev->pm_domain && dev->pm_domain->activate) {
302                 ret = dev->pm_domain->activate(dev);
303                 if (ret)
304                         goto probe_failed;
305         }
306 
307         if (dev->bus->probe) {
308                 ret = dev->bus->probe(dev);
309                 if (ret)
310                         goto probe_failed;
311         } else if (drv->probe) {
312                 ret = drv->probe(dev);
313                 if (ret)
314                         goto probe_failed;
315         }
316 
317         if (dev->pm_domain && dev->pm_domain->sync)
318                 dev->pm_domain->sync(dev);
319 
320         driver_bound(dev);
321         ret = 1;
322         pr_debug("bus: '%s': %s: bound device %s to driver %s\n",
323                  drv->bus->name, __func__, dev_name(dev), drv->name);
324         goto done;
325 
326 probe_failed:
327         devres_release_all(dev);
328         driver_sysfs_remove(dev);
329         dev->driver = NULL;
330         dev_set_drvdata(dev, NULL);
331         if (dev->pm_domain && dev->pm_domain->dismiss)
332                 dev->pm_domain->dismiss(dev);
333 
334         switch (ret) {
335         case -EPROBE_DEFER:
336                 /* Driver requested deferred probing */
337                 dev_dbg(dev, "Driver %s requests probe deferral\n", drv->name);
338                 driver_deferred_probe_add(dev);
339                 /* Did a trigger occur while probing? Need to re-trigger if yes */
340                 if (local_trigger_count != atomic_read(&deferred_trigger_count))
341                         driver_deferred_probe_trigger();
342                 break;
343         case -ENODEV:
344         case -ENXIO:
345                 pr_debug("%s: probe of %s rejects match %d\n",
346                          drv->name, dev_name(dev), ret);
347                 break;
348         default:
349                 /* driver matched but the probe failed */
350                 printk(KERN_WARNING
351                        "%s: probe of %s failed with error %d\n",
352                        drv->name, dev_name(dev), ret);
353         }
354         /*
355          * Ignore errors returned by ->probe so that the next driver can try
356          * its luck.
357          */
358         ret = 0;
359 done:
360         atomic_dec(&probe_count);
361         wake_up(&probe_waitqueue);
362         return ret;
363 }
364 
365 /**
366  * driver_probe_done
367  * Determine if the probe sequence is finished or not.
368  *
369  * Should somehow figure out how to use a semaphore, not an atomic variable...
370  */
371 int driver_probe_done(void)
372 {
373         pr_debug("%s: probe_count = %d\n", __func__,
374                  atomic_read(&probe_count));
375         if (atomic_read(&probe_count))
376                 return -EBUSY;
377         return 0;
378 }
379 
380 /**
381  * wait_for_device_probe
382  * Wait for device probing to be completed.
383  */
384 void wait_for_device_probe(void)
385 {
386         /* wait for the known devices to complete their probing */
387         wait_event(probe_waitqueue, atomic_read(&probe_count) == 0);
388         async_synchronize_full();
389 }
390 EXPORT_SYMBOL_GPL(wait_for_device_probe);
391 
392 /**
393  * driver_probe_device - attempt to bind device & driver together
394  * @drv: driver to bind a device to
395  * @dev: device to try to bind to the driver
396  *
397  * This function returns -ENODEV if the device is not registered,
398  * 1 if the device is bound successfully and 0 otherwise.
399  *
400  * This function must be called with @dev lock held.  When called for a
401  * USB interface, @dev->parent lock must be held as well.
402  */
403 int driver_probe_device(struct device_driver *drv, struct device *dev)
404 {
405         int ret = 0;
406 
407         if (!device_is_registered(dev))
408                 return -ENODEV;
409 
410         pr_debug("bus: '%s': %s: matched device %s with driver %s\n",
411                  drv->bus->name, __func__, dev_name(dev), drv->name);
412 
413         pm_runtime_barrier(dev);
414         ret = really_probe(dev, drv);
415         pm_request_idle(dev);
416 
417         return ret;
418 }
419 
420 static int __device_attach(struct device_driver *drv, void *data)
421 {
422         struct device *dev = data;
423 
424         if (!driver_match_device(drv, dev))
425                 return 0;
426 
427         return driver_probe_device(drv, dev);
428 }
429 
430 /**
431  * device_attach - try to attach device to a driver.
432  * @dev: device.
433  *
434  * Walk the list of drivers that the bus has and call
435  * driver_probe_device() for each pair. If a compatible
436  * pair is found, break out and return.
437  *
438  * Returns 1 if the device was bound to a driver;
439  * 0 if no matching driver was found;
440  * -ENODEV if the device is not registered.
441  *
442  * When called for a USB interface, @dev->parent lock must be held.
443  */
444 int device_attach(struct device *dev)
445 {
446         int ret = 0;
447 
448         device_lock(dev);
449         if (dev->driver) {
450                 if (klist_node_attached(&dev->p->knode_driver)) {
451                         ret = 1;
452                         goto out_unlock;
453                 }
454                 ret = device_bind_driver(dev);
455                 if (ret == 0)
456                         ret = 1;
457                 else {
458                         dev->driver = NULL;
459                         ret = 0;
460                 }
461         } else {
462                 ret = bus_for_each_drv(dev->bus, NULL, dev, __device_attach);
463                 pm_request_idle(dev);
464         }
465 out_unlock:
466         device_unlock(dev);
467         return ret;
468 }
469 EXPORT_SYMBOL_GPL(device_attach);
470 
471 static int __driver_attach(struct device *dev, void *data)
472 {
473         struct device_driver *drv = data;
474 
475         /*
476          * Lock device and try to bind to it. We drop the error
477          * here and always return 0, because we need to keep trying
478          * to bind to devices and some drivers will return an error
479          * simply if it didn't support the device.
480          *
481          * driver_probe_device() will spit a warning if there
482          * is an error.
483          */
484 
485         if (!driver_match_device(drv, dev))
486                 return 0;
487 
488         if (dev->parent)        /* Needed for USB */
489                 device_lock(dev->parent);
490         device_lock(dev);
491         if (!dev->driver)
492                 driver_probe_device(drv, dev);
493         device_unlock(dev);
494         if (dev->parent)
495                 device_unlock(dev->parent);
496 
497         return 0;
498 }
499 
500 /**
501  * driver_attach - try to bind driver to devices.
502  * @drv: driver.
503  *
504  * Walk the list of devices that the bus has on it and try to
505  * match the driver with each one.  If driver_probe_device()
506  * returns 0 and the @dev->driver is set, we've found a
507  * compatible pair.
508  */
509 int driver_attach(struct device_driver *drv)
510 {
511         return bus_for_each_dev(drv->bus, NULL, drv, __driver_attach);
512 }
513 EXPORT_SYMBOL_GPL(driver_attach);
514 
515 /*
516  * __device_release_driver() must be called with @dev lock held.
517  * When called for a USB interface, @dev->parent lock must be held as well.
518  */
519 static void __device_release_driver(struct device *dev)
520 {
521         struct device_driver *drv;
522 
523         drv = dev->driver;
524         if (drv) {
525                 pm_runtime_get_sync(dev);
526 
527                 driver_sysfs_remove(dev);
528 
529                 if (dev->bus)
530                         blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
531                                                      BUS_NOTIFY_UNBIND_DRIVER,
532                                                      dev);
533 
534                 pm_runtime_put_sync(dev);
535 
536                 if (dev->bus && dev->bus->remove)
537                         dev->bus->remove(dev);
538                 else if (drv->remove)
539                         drv->remove(dev);
540                 devres_release_all(dev);
541                 dev->driver = NULL;
542                 dev_set_drvdata(dev, NULL);
543                 if (dev->pm_domain && dev->pm_domain->dismiss)
544                         dev->pm_domain->dismiss(dev);
545 
546                 klist_remove(&dev->p->knode_driver);
547                 if (dev->bus)
548                         blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
549                                                      BUS_NOTIFY_UNBOUND_DRIVER,
550                                                      dev);
551 
552         }
553 }
554 
555 /**
556  * device_release_driver - manually detach device from driver.
557  * @dev: device.
558  *
559  * Manually detach device from driver.
560  * When called for a USB interface, @dev->parent lock must be held.
561  */
562 void device_release_driver(struct device *dev)
563 {
564         /*
565          * If anyone calls device_release_driver() recursively from
566          * within their ->remove callback for the same device, they
567          * will deadlock right here.
568          */
569         device_lock(dev);
570         __device_release_driver(dev);
571         device_unlock(dev);
572 }
573 EXPORT_SYMBOL_GPL(device_release_driver);
574 
575 /**
576  * driver_detach - detach driver from all devices it controls.
577  * @drv: driver.
578  */
579 void driver_detach(struct device_driver *drv)
580 {
581         struct device_private *dev_prv;
582         struct device *dev;
583 
584         for (;;) {
585                 spin_lock(&drv->p->klist_devices.k_lock);
586                 if (list_empty(&drv->p->klist_devices.k_list)) {
587                         spin_unlock(&drv->p->klist_devices.k_lock);
588                         break;
589                 }
590                 dev_prv = list_entry(drv->p->klist_devices.k_list.prev,
591                                      struct device_private,
592                                      knode_driver.n_node);
593                 dev = dev_prv->device;
594                 get_device(dev);
595                 spin_unlock(&drv->p->klist_devices.k_lock);
596 
597                 if (dev->parent)        /* Needed for USB */
598                         device_lock(dev->parent);
599                 device_lock(dev);
600                 if (dev->driver == drv)
601                         __device_release_driver(dev);
602                 device_unlock(dev);
603                 if (dev->parent)
604                         device_unlock(dev->parent);
605                 put_device(dev);
606         }
607 }
608 

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