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         device_pm_check_callbacks(dev);
 209
 210         /*
 211          * Make sure the device is no longer in one of the deferred lists and
 212          * kick off retrying all pending devices
 213          */
 214         driver_deferred_probe_del(dev);
 215         driver_deferred_probe_trigger();
 216
 217         if (dev->bus)
 218                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 219                                              BUS_NOTIFY_BOUND_DRIVER, dev);
 220 }
 221
 222 static int driver_sysfs_add(struct device *dev)
 223 {
 224         int ret;
 225
 226         if (dev->bus)
 227                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 228                                              BUS_NOTIFY_BIND_DRIVER, dev);
 229
 230         ret = sysfs_create_link(&dev->driver->p->kobj, &dev->kobj,
 231                           kobject_name(&dev->kobj));
 232         if (ret == 0) {
 233                 ret = sysfs_create_link(&dev->kobj, &dev->driver->p->kobj,
 234                                         "driver");
 235                 if (ret)
 236                         sysfs_remove_link(&dev->driver->p->kobj,
 237                                         kobject_name(&dev->kobj));
 238         }
 239         return ret;
 240 }
 241
 242 static void driver_sysfs_remove(struct device *dev)
 243 {
 244         struct device_driver *drv = dev->driver;
 245
 246         if (drv) {
 247                 sysfs_remove_link(&drv->p->kobj, kobject_name(&dev->kobj));
 248                 sysfs_remove_link(&dev->kobj, "driver");
 249         }
 250 }
 251
 252 /**
 253  * device_bind_driver - bind a driver to one device.
 254  * @dev: device.
 255  *
 256  * Allow manual attachment of a driver to a device.
 257  * Caller must have already set @dev->driver.
 258  *
 259  * Note that this does not modify the bus reference count
 260  * nor take the bus's rwsem. Please verify those are accounted
 261  * for before calling this. (It is ok to call with no other effort
 262  * from a driver's probe() method.)
 263  *
 264  * This function must be called with the device lock held.
 265  */
 266 int device_bind_driver(struct device *dev)
 267 {
 268         int ret;
 269
 270         ret = driver_sysfs_add(dev);
 271         if (!ret)
 272                 driver_bound(dev);
 273         return ret;
 274 }
 275 EXPORT_SYMBOL_GPL(device_bind_driver);
 276
 277 static atomic_t probe_count = ATOMIC_INIT(0);
 278 static DECLARE_WAIT_QUEUE_HEAD(probe_waitqueue);
 279
 280 static int really_probe(struct device *dev, struct device_driver *drv)
 281 {
 282         int ret = 0;
 283         int local_trigger_count = atomic_read(&deferred_trigger_count);
 284
 285         atomic_inc(&probe_count);
 286         pr_debug("bus: '%s': %s: probing driver %s with device %s\n",
 287                  drv->bus->name, __func__, drv->name, dev_name(dev));
 288         WARN_ON(!list_empty(&dev->devres_head));
 289
 290         dev->driver = drv;
 291
 292         /* If using pinctrl, bind pins now before probing */
 293         ret = pinctrl_bind_pins(dev);
 294         if (ret)
 295                 goto probe_failed;
 296
 297         if (driver_sysfs_add(dev)) {
 298                 printk(KERN_ERR "%s: driver_sysfs_add(%s) failed\n",
 299                         __func__, dev_name(dev));
 300                 goto probe_failed;
 301         }
 302
 303         if (dev->pm_domain && dev->pm_domain->activate) {
 304                 ret = dev->pm_domain->activate(dev);
 305                 if (ret)
 306                         goto probe_failed;
 307         }
 308
 309         /*
 310          * Ensure devices are listed in devices_kset in correct order
 311          * It's important to move Dev to the end of devices_kset before
 312          * calling .probe, because it could be recursive and parent Dev
 313          * should always go first
 314          */
 315         devices_kset_move_last(dev);
 316
 317         if (dev->bus->probe) {
 318                 ret = dev->bus->probe(dev);
 319                 if (ret)
 320                         goto probe_failed;
 321         } else if (drv->probe) {
 322                 ret = drv->probe(dev);
 323                 if (ret)
 324                         goto probe_failed;
 325         }
 326
 327         pinctrl_init_done(dev);
 328
 329         if (dev->pm_domain && dev->pm_domain->sync)
 330                 dev->pm_domain->sync(dev);
 331
 332         driver_bound(dev);
 333         ret = 1;
 334         pr_debug("bus: '%s': %s: bound device %s to driver %s\n",
 335                  drv->bus->name, __func__, dev_name(dev), drv->name);
 336         goto done;
 337
 338 probe_failed:
 339         devres_release_all(dev);
 340         driver_sysfs_remove(dev);
 341         dev->driver = NULL;
 342         dev_set_drvdata(dev, NULL);
 343         if (dev->pm_domain && dev->pm_domain->dismiss)
 344                 dev->pm_domain->dismiss(dev);
 345
 346         switch (ret) {
 347         case -EPROBE_DEFER:
 348                 /* Driver requested deferred probing */
 349                 dev_dbg(dev, "Driver %s requests probe deferral\n", drv->name);
 350                 driver_deferred_probe_add(dev);
 351                 /* Did a trigger occur while probing? Need to re-trigger if yes */
 352                 if (local_trigger_count != atomic_read(&deferred_trigger_count))
 353                         driver_deferred_probe_trigger();
 354                 break;
 355         case -ENODEV:
 356         case -ENXIO:
 357                 pr_debug("%s: probe of %s rejects match %d\n",
 358                          drv->name, dev_name(dev), ret);
 359                 break;
 360         default:
 361                 /* driver matched but the probe failed */
 362                 printk(KERN_WARNING
 363                        "%s: probe of %s failed with error %d\n",
 364                        drv->name, dev_name(dev), ret);
 365         }
 366         /*
 367          * Ignore errors returned by ->probe so that the next driver can try
 368          * its luck.
 369          */
 370         ret = 0;
 371 done:
 372         atomic_dec(&probe_count);
 373         wake_up(&probe_waitqueue);
 374         return ret;
 375 }
 376
 377 /**
 378  * driver_probe_done
 379  * Determine if the probe sequence is finished or not.
 380  *
 381  * Should somehow figure out how to use a semaphore, not an atomic variable...
 382  */
 383 int driver_probe_done(void)
 384 {
 385         pr_debug("%s: probe_count = %d\n", __func__,
 386                  atomic_read(&probe_count));
 387         if (atomic_read(&probe_count))
 388                 return -EBUSY;
 389         return 0;
 390 }
 391
 392 /**
 393  * wait_for_device_probe
 394  * Wait for device probing to be completed.
 395  */
 396 void wait_for_device_probe(void)
 397 {
 398         /* wait for the known devices to complete their probing */
 399         wait_event(probe_waitqueue, atomic_read(&probe_count) == 0);
 400         async_synchronize_full();
 401 }
 402 EXPORT_SYMBOL_GPL(wait_for_device_probe);
 403
 404 /**
 405  * driver_probe_device - attempt to bind device & driver together
 406  * @drv: driver to bind a device to
 407  * @dev: device to try to bind to the driver
 408  *
 409  * This function returns -ENODEV if the device is not registered,
 410  * 1 if the device is bound successfully and 0 otherwise.
 411  *
 412  * This function must be called with @dev lock held.  When called for a
 413  * USB interface, @dev->parent lock must be held as well.
 414  *
 415  * If the device has a parent, runtime-resume the parent before driver probing.
 416  */
 417 int driver_probe_device(struct device_driver *drv, struct device *dev)
 418 {
 419         int ret = 0;
 420
 421         if (!device_is_registered(dev))
 422                 return -ENODEV;
 423
 424         pr_debug("bus: '%s': %s: matched device %s with driver %s\n",
 425                  drv->bus->name, __func__, dev_name(dev), drv->name);
 426
 427         if (dev->parent)
 428                 pm_runtime_get_sync(dev->parent);
 429
 430         pm_runtime_barrier(dev);
 431         ret = really_probe(dev, drv);
 432         pm_request_idle(dev);
 433
 434         if (dev->parent)
 435                 pm_runtime_put(dev->parent);
 436
 437         return ret;
 438 }
 439
 440 bool driver_allows_async_probing(struct device_driver *drv)
 441 {
 442         switch (drv->probe_type) {
 443         case PROBE_PREFER_ASYNCHRONOUS:
 444                 return true;
 445
 446         case PROBE_FORCE_SYNCHRONOUS:
 447                 return false;
 448
 449         default:
 450                 if (module_requested_async_probing(drv->owner))
 451                         return true;
 452
 453                 return false;
 454         }
 455 }
 456
 457 struct device_attach_data {
 458         struct device *dev;
 459
 460         /*
 461          * Indicates whether we are are considering asynchronous probing or
 462          * not. Only initial binding after device or driver registration
 463          * (including deferral processing) may be done asynchronously, the
 464          * rest is always synchronous, as we expect it is being done by
 465          * request from userspace.
 466          */
 467         bool check_async;
 468
 469         /*
 470          * Indicates if we are binding synchronous or asynchronous drivers.
 471          * When asynchronous probing is enabled we'll execute 2 passes
 472          * over drivers: first pass doing synchronous probing and second
 473          * doing asynchronous probing (if synchronous did not succeed -
 474          * most likely because there was no driver requiring synchronous
 475          * probing - and we found asynchronous driver during first pass).
 476          * The 2 passes are done because we can't shoot asynchronous
 477          * probe for given device and driver from bus_for_each_drv() since
 478          * driver pointer is not guaranteed to stay valid once
 479          * bus_for_each_drv() iterates to the next driver on the bus.
 480          */
 481         bool want_async;
 482
 483         /*
 484          * We'll set have_async to 'true' if, while scanning for matching
 485          * driver, we'll encounter one that requests asynchronous probing.
 486          */
 487         bool have_async;
 488 };
 489
 490 static int __device_attach_driver(struct device_driver *drv, void *_data)
 491 {
 492         struct device_attach_data *data = _data;
 493         struct device *dev = data->dev;
 494         bool async_allowed;
 495
 496         /*
 497          * Check if device has already been claimed. This may
 498          * happen with driver loading, device discovery/registration,
 499          * and deferred probe processing happens all at once with
 500          * multiple threads.
 501          */
 502         if (dev->driver)
 503                 return -EBUSY;
 504
 505         if (!driver_match_device(drv, dev))
 506                 return 0;
 507
 508         async_allowed = driver_allows_async_probing(drv);
 509
 510         if (async_allowed)
 511                 data->have_async = true;
 512
 513         if (data->check_async && async_allowed != data->want_async)
 514                 return 0;
 515
 516         return driver_probe_device(drv, dev);
 517 }
 518
 519 static void __device_attach_async_helper(void *_dev, async_cookie_t cookie)
 520 {
 521         struct device *dev = _dev;
 522         struct device_attach_data data = {
 523                 .dev            = dev,
 524                 .check_async    = true,
 525                 .want_async     = true,
 526         };
 527
 528         device_lock(dev);
 529
 530         if (dev->parent)
 531                 pm_runtime_get_sync(dev->parent);
 532
 533         bus_for_each_drv(dev->bus, NULL, &data, __device_attach_driver);
 534         dev_dbg(dev, "async probe completed\n");
 535
 536         pm_request_idle(dev);
 537
 538         if (dev->parent)
 539                 pm_runtime_put(dev->parent);
 540
 541         device_unlock(dev);
 542
 543         put_device(dev);
 544 }
 545
 546 static int __device_attach(struct device *dev, bool allow_async)
 547 {
 548         int ret = 0;
 549
 550         device_lock(dev);
 551         if (dev->driver) {
 552                 if (klist_node_attached(&dev->p->knode_driver)) {
 553                         ret = 1;
 554                         goto out_unlock;
 555                 }
 556                 ret = device_bind_driver(dev);
 557                 if (ret == 0)
 558                         ret = 1;
 559                 else {
 560                         dev->driver = NULL;
 561                         ret = 0;
 562                 }
 563         } else {
 564                 struct device_attach_data data = {
 565                         .dev = dev,
 566                         .check_async = allow_async,
 567                         .want_async = false,
 568                 };
 569
 570                 if (dev->parent)
 571                         pm_runtime_get_sync(dev->parent);
 572
 573                 ret = bus_for_each_drv(dev->bus, NULL, &data,
 574                                         __device_attach_driver);
 575                 if (!ret && allow_async && data.have_async) {
 576                         /*
 577                          * If we could not find appropriate driver
 578                          * synchronously and we are allowed to do
 579                          * async probes and there are drivers that
 580                          * want to probe asynchronously, we'll
 581                          * try them.
 582                          */
 583                         dev_dbg(dev, "scheduling asynchronous probe\n");
 584                         get_device(dev);
 585                         async_schedule(__device_attach_async_helper, dev);
 586                 } else {
 587                         pm_request_idle(dev);
 588                 }
 589
 590                 if (dev->parent)
 591                         pm_runtime_put(dev->parent);
 592         }
 593 out_unlock:
 594         device_unlock(dev);
 595         return ret;
 596 }
 597
 598 /**
 599  * device_attach - try to attach device to a driver.
 600  * @dev: device.
 601  *
 602  * Walk the list of drivers that the bus has and call
 603  * driver_probe_device() for each pair. If a compatible
 604  * pair is found, break out and return.
 605  *
 606  * Returns 1 if the device was bound to a driver;
 607  * 0 if no matching driver was found;
 608  * -ENODEV if the device is not registered.
 609  *
 610  * When called for a USB interface, @dev->parent lock must be held.
 611  */
 612 int device_attach(struct device *dev)
 613 {
 614         return __device_attach(dev, false);
 615 }
 616 EXPORT_SYMBOL_GPL(device_attach);
 617
 618 void device_initial_probe(struct device *dev)
 619 {
 620         __device_attach(dev, true);
 621 }
 622
 623 static int __driver_attach(struct device *dev, void *data)
 624 {
 625         struct device_driver *drv = data;
 626
 627         /*
 628          * Lock device and try to bind to it. We drop the error
 629          * here and always return 0, because we need to keep trying
 630          * to bind to devices and some drivers will return an error
 631          * simply if it didn't support the device.
 632          *
 633          * driver_probe_device() will spit a warning if there
 634          * is an error.
 635          */
 636
 637         if (!driver_match_device(drv, dev))
 638                 return 0;
 639
 640         if (dev->parent)        /* Needed for USB */
 641                 device_lock(dev->parent);
 642         device_lock(dev);
 643         if (!dev->driver)
 644                 driver_probe_device(drv, dev);
 645         device_unlock(dev);
 646         if (dev->parent)
 647                 device_unlock(dev->parent);
 648
 649         return 0;
 650 }
 651
 652 /**
 653  * driver_attach - try to bind driver to devices.
 654  * @drv: driver.
 655  *
 656  * Walk the list of devices that the bus has on it and try to
 657  * match the driver with each one.  If driver_probe_device()
 658  * returns 0 and the @dev->driver is set, we've found a
 659  * compatible pair.
 660  */
 661 int driver_attach(struct device_driver *drv)
 662 {
 663         return bus_for_each_dev(drv->bus, NULL, drv, __driver_attach);
 664 }
 665 EXPORT_SYMBOL_GPL(driver_attach);
 666
 667 /*
 668  * __device_release_driver() must be called with @dev lock held.
 669  * When called for a USB interface, @dev->parent lock must be held as well.
 670  */
 671 static void __device_release_driver(struct device *dev)
 672 {
 673         struct device_driver *drv;
 674
 675         drv = dev->driver;
 676         if (drv) {
 677                 if (driver_allows_async_probing(drv))
 678                         async_synchronize_full();
 679
 680                 pm_runtime_get_sync(dev);
 681
 682                 driver_sysfs_remove(dev);
 683
 684                 if (dev->bus)
 685                         blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 686                                                      BUS_NOTIFY_UNBIND_DRIVER,
 687                                                      dev);
 688
 689                 pm_runtime_put_sync(dev);
 690
 691                 if (dev->bus && dev->bus->remove)
 692                         dev->bus->remove(dev);
 693                 else if (drv->remove)
 694                         drv->remove(dev);
 695                 devres_release_all(dev);
 696                 dev->driver = NULL;
 697                 dev_set_drvdata(dev, NULL);
 698                 if (dev->pm_domain && dev->pm_domain->dismiss)
 699                         dev->pm_domain->dismiss(dev);
 700
 701                 klist_remove(&dev->p->knode_driver);
 702                 device_pm_check_callbacks(dev);
 703                 if (dev->bus)
 704                         blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 705                                                      BUS_NOTIFY_UNBOUND_DRIVER,
 706                                                      dev);
 707
 708         }
 709 }
 710
 711 /**
 712  * device_release_driver - manually detach device from driver.
 713  * @dev: device.
 714  *
 715  * Manually detach device from driver.
 716  * When called for a USB interface, @dev->parent lock must be held.
 717  */
 718 void device_release_driver(struct device *dev)
 719 {
 720         /*
 721          * If anyone calls device_release_driver() recursively from
 722          * within their ->remove callback for the same device, they
 723          * will deadlock right here.
 724          */
 725         device_lock(dev);
 726         __device_release_driver(dev);
 727         device_unlock(dev);
 728 }
 729 EXPORT_SYMBOL_GPL(device_release_driver);
 730
 731 /**
 732  * driver_detach - detach driver from all devices it controls.
 733  * @drv: driver.
 734  */
 735 void driver_detach(struct device_driver *drv)
 736 {
 737         struct device_private *dev_prv;
 738         struct device *dev;
 739
 740         for (;;) {
 741                 spin_lock(&drv->p->klist_devices.k_lock);
 742                 if (list_empty(&drv->p->klist_devices.k_list)) {
 743                         spin_unlock(&drv->p->klist_devices.k_lock);
 744                         break;
 745                 }
 746                 dev_prv = list_entry(drv->p->klist_devices.k_list.prev,
 747                                      struct device_private,
 748                                      knode_driver.n_node);
 749                 dev = dev_prv->device;
 750                 get_device(dev);
 751                 spin_unlock(&drv->p->klist_devices.k_lock);
 752
 753                 if (dev->parent)        /* Needed for USB */
 754                         device_lock(dev->parent);
 755                 device_lock(dev);
 756                 if (dev->driver == drv)
 757                         __device_release_driver(dev);
 758                 device_unlock(dev);
 759                 if (dev->parent)
 760                         device_unlock(dev->parent);
 761                 put_device(dev);
 762         }
 763 }