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 occurred 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         /*
 308          * Ensure devices are listed in devices_kset in correct order
 309          * It's important to move Dev to the end of devices_kset before
 310          * calling .probe, because it could be recursive and parent Dev
 311          * should always go first
 312          */
 313         devices_kset_move_last(dev);
 314
 315         if (dev->bus->probe) {
 316                 ret = dev->bus->probe(dev);
 317                 if (ret)
 318                         goto probe_failed;
 319         } else if (drv->probe) {
 320                 ret = drv->probe(dev);
 321                 if (ret)
 322                         goto probe_failed;
 323         }
 324
 325         pinctrl_init_done(dev);
 326
 327         if (dev->pm_domain && dev->pm_domain->sync)
 328                 dev->pm_domain->sync(dev);
 329
 330         driver_bound(dev);
 331         ret = 1;
 332         pr_debug("bus: '%s': %s: bound device %s to driver %s\n",
 333                  drv->bus->name, __func__, dev_name(dev), drv->name);
 334         goto done;
 335
 336 probe_failed:
 337         devres_release_all(dev);
 338         driver_sysfs_remove(dev);
 339         dev->driver = NULL;
 340         dev_set_drvdata(dev, NULL);
 341         if (dev->pm_domain && dev->pm_domain->dismiss)
 342                 dev->pm_domain->dismiss(dev);
 343
 344         switch (ret) {
 345         case -EPROBE_DEFER:
 346                 /* Driver requested deferred probing */
 347                 dev_dbg(dev, "Driver %s requests probe deferral\n", drv->name);
 348                 driver_deferred_probe_add(dev);
 349                 /* Did a trigger occur while probing? Need to re-trigger if yes */
 350                 if (local_trigger_count != atomic_read(&deferred_trigger_count))
 351                         driver_deferred_probe_trigger();
 352                 break;
 353         case -ENODEV:
 354         case -ENXIO:
 355                 pr_debug("%s: probe of %s rejects match %d\n",
 356                          drv->name, dev_name(dev), ret);
 357                 break;
 358         default:
 359                 /* driver matched but the probe failed */
 360                 printk(KERN_WARNING
 361                        "%s: probe of %s failed with error %d\n",
 362                        drv->name, dev_name(dev), ret);
 363         }
 364         /*
 365          * Ignore errors returned by ->probe so that the next driver can try
 366          * its luck.
 367          */
 368         ret = 0;
 369 done:
 370         atomic_dec(&probe_count);
 371         wake_up(&probe_waitqueue);
 372         return ret;
 373 }
 374
 375 /**
 376  * driver_probe_done
 377  * Determine if the probe sequence is finished or not.
 378  *
 379  * Should somehow figure out how to use a semaphore, not an atomic variable...
 380  */
 381 int driver_probe_done(void)
 382 {
 383         pr_debug("%s: probe_count = %d\n", __func__,
 384                  atomic_read(&probe_count));
 385         if (atomic_read(&probe_count))
 386                 return -EBUSY;
 387         return 0;
 388 }
 389
 390 /**
 391  * wait_for_device_probe
 392  * Wait for device probing to be completed.
 393  */
 394 void wait_for_device_probe(void)
 395 {
 396         /* wait for the known devices to complete their probing */
 397         wait_event(probe_waitqueue, atomic_read(&probe_count) == 0);
 398         async_synchronize_full();
 399 }
 400 EXPORT_SYMBOL_GPL(wait_for_device_probe);
 401
 402 /**
 403  * driver_probe_device - attempt to bind device & driver together
 404  * @drv: driver to bind a device to
 405  * @dev: device to try to bind to the driver
 406  *
 407  * This function returns -ENODEV if the device is not registered,
 408  * 1 if the device is bound successfully and 0 otherwise.
 409  *
 410  * This function must be called with @dev lock held.  When called for a
 411  * USB interface, @dev->parent lock must be held as well.
 412  *
 413  * If the device has a parent, runtime-resume the parent before driver probing.
 414  */
 415 int driver_probe_device(struct device_driver *drv, struct device *dev)
 416 {
 417         int ret = 0;
 418
 419         if (!device_is_registered(dev))
 420                 return -ENODEV;
 421
 422         pr_debug("bus: '%s': %s: matched device %s with driver %s\n",
 423                  drv->bus->name, __func__, dev_name(dev), drv->name);
 424
 425         if (dev->parent)
 426                 pm_runtime_get_sync(dev->parent);
 427
 428         pm_runtime_barrier(dev);
 429         ret = really_probe(dev, drv);
 430         pm_request_idle(dev);
 431
 432         if (dev->parent)
 433                 pm_runtime_put(dev->parent);
 434
 435         return ret;
 436 }
 437
 438 bool driver_allows_async_probing(struct device_driver *drv)
 439 {
 440         switch (drv->probe_type) {
 441         case PROBE_PREFER_ASYNCHRONOUS:
 442                 return true;
 443
 444         case PROBE_FORCE_SYNCHRONOUS:
 445                 return false;
 446
 447         default:
 448                 if (module_requested_async_probing(drv->owner))
 449                         return true;
 450
 451                 return false;
 452         }
 453 }
 454
 455 struct device_attach_data {
 456         struct device *dev;
 457
 458         /*
 459          * Indicates whether we are are considering asynchronous probing or
 460          * not. Only initial binding after device or driver registration
 461          * (including deferral processing) may be done asynchronously, the
 462          * rest is always synchronous, as we expect it is being done by
 463          * request from userspace.
 464          */
 465         bool check_async;
 466
 467         /*
 468          * Indicates if we are binding synchronous or asynchronous drivers.
 469          * When asynchronous probing is enabled we'll execute 2 passes
 470          * over drivers: first pass doing synchronous probing and second
 471          * doing asynchronous probing (if synchronous did not succeed -
 472          * most likely because there was no driver requiring synchronous
 473          * probing - and we found asynchronous driver during first pass).
 474          * The 2 passes are done because we can't shoot asynchronous
 475          * probe for given device and driver from bus_for_each_drv() since
 476          * driver pointer is not guaranteed to stay valid once
 477          * bus_for_each_drv() iterates to the next driver on the bus.
 478          */
 479         bool want_async;
 480
 481         /*
 482          * We'll set have_async to 'true' if, while scanning for matching
 483          * driver, we'll encounter one that requests asynchronous probing.
 484          */
 485         bool have_async;
 486 };
 487
 488 static int __device_attach_driver(struct device_driver *drv, void *_data)
 489 {
 490         struct device_attach_data *data = _data;
 491         struct device *dev = data->dev;
 492         bool async_allowed;
 493
 494         /*
 495          * Check if device has already been claimed. This may
 496          * happen with driver loading, device discovery/registration,
 497          * and deferred probe processing happens all at once with
 498          * multiple threads.
 499          */
 500         if (dev->driver)
 501                 return -EBUSY;
 502
 503         if (!driver_match_device(drv, dev))
 504                 return 0;
 505
 506         async_allowed = driver_allows_async_probing(drv);
 507
 508         if (async_allowed)
 509                 data->have_async = true;
 510
 511         if (data->check_async && async_allowed != data->want_async)
 512                 return 0;
 513
 514         return driver_probe_device(drv, dev);
 515 }
 516
 517 static void __device_attach_async_helper(void *_dev, async_cookie_t cookie)
 518 {
 519         struct device *dev = _dev;
 520         struct device_attach_data data = {
 521                 .dev            = dev,
 522                 .check_async    = true,
 523                 .want_async     = true,
 524         };
 525
 526         device_lock(dev);
 527
 528         if (dev->parent)
 529                 pm_runtime_get_sync(dev->parent);
 530
 531         bus_for_each_drv(dev->bus, NULL, &data, __device_attach_driver);
 532         dev_dbg(dev, "async probe completed\n");
 533
 534         pm_request_idle(dev);
 535
 536         if (dev->parent)
 537                 pm_runtime_put(dev->parent);
 538
 539         device_unlock(dev);
 540
 541         put_device(dev);
 542 }
 543
 544 static int __device_attach(struct device *dev, bool allow_async)
 545 {
 546         int ret = 0;
 547
 548         device_lock(dev);
 549         if (dev->driver) {
 550                 if (klist_node_attached(&dev->p->knode_driver)) {
 551                         ret = 1;
 552                         goto out_unlock;
 553                 }
 554                 ret = device_bind_driver(dev);
 555                 if (ret == 0)
 556                         ret = 1;
 557                 else {
 558                         dev->driver = NULL;
 559                         ret = 0;
 560                 }
 561         } else {
 562                 struct device_attach_data data = {
 563                         .dev = dev,
 564                         .check_async = allow_async,
 565                         .want_async = false,
 566                 };
 567
 568                 if (dev->parent)
 569                         pm_runtime_get_sync(dev->parent);
 570
 571                 ret = bus_for_each_drv(dev->bus, NULL, &data,
 572                                         __device_attach_driver);
 573                 if (!ret && allow_async && data.have_async) {
 574                         /*
 575                          * If we could not find appropriate driver
 576                          * synchronously and we are allowed to do
 577                          * async probes and there are drivers that
 578                          * want to probe asynchronously, we'll
 579                          * try them.
 580                          */
 581                         dev_dbg(dev, "scheduling asynchronous probe\n");
 582                         get_device(dev);
 583                         async_schedule(__device_attach_async_helper, dev);
 584                 } else {
 585                         pm_request_idle(dev);
 586                 }
 587
 588                 if (dev->parent)
 589                         pm_runtime_put(dev->parent);
 590         }
 591 out_unlock:
 592         device_unlock(dev);
 593         return ret;
 594 }
 595
 596 /**
 597  * device_attach - try to attach device to a driver.
 598  * @dev: device.
 599  *
 600  * Walk the list of drivers that the bus has and call
 601  * driver_probe_device() for each pair. If a compatible
 602  * pair is found, break out and return.
 603  *
 604  * Returns 1 if the device was bound to a driver;
 605  * 0 if no matching driver was found;
 606  * -ENODEV if the device is not registered.
 607  *
 608  * When called for a USB interface, @dev->parent lock must be held.
 609  */
 610 int device_attach(struct device *dev)
 611 {
 612         return __device_attach(dev, false);
 613 }
 614 EXPORT_SYMBOL_GPL(device_attach);
 615
 616 void device_initial_probe(struct device *dev)
 617 {
 618         __device_attach(dev, true);
 619 }
 620
 621 static int __driver_attach(struct device *dev, void *data)
 622 {
 623         struct device_driver *drv = data;
 624
 625         /*
 626          * Lock device and try to bind to it. We drop the error
 627          * here and always return 0, because we need to keep trying
 628          * to bind to devices and some drivers will return an error
 629          * simply if it didn't support the device.
 630          *
 631          * driver_probe_device() will spit a warning if there
 632          * is an error.
 633          */
 634
 635         if (!driver_match_device(drv, dev))
 636                 return 0;
 637
 638         if (dev->parent)        /* Needed for USB */
 639                 device_lock(dev->parent);
 640         device_lock(dev);
 641         if (!dev->driver)
 642                 driver_probe_device(drv, dev);
 643         device_unlock(dev);
 644         if (dev->parent)
 645                 device_unlock(dev->parent);
 646
 647         return 0;
 648 }
 649
 650 /**
 651  * driver_attach - try to bind driver to devices.
 652  * @drv: driver.
 653  *
 654  * Walk the list of devices that the bus has on it and try to
 655  * match the driver with each one.  If driver_probe_device()
 656  * returns 0 and the @dev->driver is set, we've found a
 657  * compatible pair.
 658  */
 659 int driver_attach(struct device_driver *drv)
 660 {
 661         return bus_for_each_dev(drv->bus, NULL, drv, __driver_attach);
 662 }
 663 EXPORT_SYMBOL_GPL(driver_attach);
 664
 665 /*
 666  * __device_release_driver() must be called with @dev lock held.
 667  * When called for a USB interface, @dev->parent lock must be held as well.
 668  */
 669 static void __device_release_driver(struct device *dev)
 670 {
 671         struct device_driver *drv;
 672
 673         drv = dev->driver;
 674         if (drv) {
 675                 if (driver_allows_async_probing(drv))
 676                         async_synchronize_full();
 677
 678                 pm_runtime_get_sync(dev);
 679
 680                 driver_sysfs_remove(dev);
 681
 682                 if (dev->bus)
 683                         blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 684                                                      BUS_NOTIFY_UNBIND_DRIVER,
 685                                                      dev);
 686
 687                 pm_runtime_put_sync(dev);
 688
 689                 if (dev->bus && dev->bus->remove)
 690                         dev->bus->remove(dev);
 691                 else if (drv->remove)
 692                         drv->remove(dev);
 693                 devres_release_all(dev);
 694                 dev->driver = NULL;
 695                 dev_set_drvdata(dev, NULL);
 696                 if (dev->pm_domain && dev->pm_domain->dismiss)
 697                         dev->pm_domain->dismiss(dev);
 698
 699                 klist_remove(&dev->p->knode_driver);
 700                 if (dev->bus)
 701                         blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 702                                                      BUS_NOTIFY_UNBOUND_DRIVER,
 703                                                      dev);
 704
 705         }
 706 }
 707
 708 /**
 709  * device_release_driver - manually detach device from driver.
 710  * @dev: device.
 711  *
 712  * Manually detach device from driver.
 713  * When called for a USB interface, @dev->parent lock must be held.
 714  */
 715 void device_release_driver(struct device *dev)
 716 {
 717         /*
 718          * If anyone calls device_release_driver() recursively from
 719          * within their ->remove callback for the same device, they
 720          * will deadlock right here.
 721          */
 722         device_lock(dev);
 723         __device_release_driver(dev);
 724         device_unlock(dev);
 725 }
 726 EXPORT_SYMBOL_GPL(device_release_driver);
 727
 728 /**
 729  * driver_detach - detach driver from all devices it controls.
 730  * @drv: driver.
 731  */
 732 void driver_detach(struct device_driver *drv)
 733 {
 734         struct device_private *dev_prv;
 735         struct device *dev;
 736
 737         for (;;) {
 738                 spin_lock(&drv->p->klist_devices.k_lock);
 739                 if (list_empty(&drv->p->klist_devices.k_list)) {
 740                         spin_unlock(&drv->p->klist_devices.k_lock);
 741                         break;
 742                 }
 743                 dev_prv = list_entry(drv->p->klist_devices.k_list.prev,
 744                                      struct device_private,
 745                                      knode_driver.n_node);
 746                 dev = dev_prv->device;
 747                 get_device(dev);
 748                 spin_unlock(&drv->p->klist_devices.k_lock);
 749
 750                 if (dev->parent)        /* Needed for USB */
 751                         device_lock(dev->parent);
 752                 device_lock(dev);
 753                 if (dev->driver == drv)
 754                         __device_release_driver(dev);
 755                 device_unlock(dev);
 756                 if (dev->parent)
 757                         device_unlock(dev->parent);
 758                 put_device(dev);
 759         }
 760 }