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  * In some cases, like suspend to RAM or hibernation, It might be reasonable
  59  * to prohibit probing of devices as it could be unsafe.
  60  * Once defer_all_probes is true all drivers probes will be forcibly deferred.
  61  */
  62 static bool defer_all_probes;
  63
  64 /*
  65  * deferred_probe_work_func() - Retry probing devices in the active list.
  66  */
  67 static void deferred_probe_work_func(struct work_struct *work)
  68 {
  69         struct device *dev;
  70         struct device_private *private;
  71         /*
  72          * This block processes every device in the deferred 'active' list.
  73          * Each device is removed from the active list and passed to
  74          * bus_probe_device() to re-attempt the probe.  The loop continues
  75          * until every device in the active list is removed and retried.
  76          *
  77          * Note: Once the device is removed from the list and the mutex is
  78          * released, it is possible for the device get freed by another thread
  79          * and cause a illegal pointer dereference.  This code uses
  80          * get/put_device() to ensure the device structure cannot disappear
  81          * from under our feet.
  82          */
  83         mutex_lock(&deferred_probe_mutex);
  84         while (!list_empty(&deferred_probe_active_list)) {
  85                 private = list_first_entry(&deferred_probe_active_list,
  86                                         typeof(*dev->p), deferred_probe);
  87                 dev = private->device;
  88                 list_del_init(&private->deferred_probe);
  89
  90                 get_device(dev);
  91
  92                 /*
  93                  * Drop the mutex while probing each device; the probe path may
  94                  * manipulate the deferred list
  95                  */
  96                 mutex_unlock(&deferred_probe_mutex);
  97
  98                 /*
  99                  * Force the device to the end of the dpm_list since
 100                  * the PM code assumes that the order we add things to
 101                  * the list is a good order for suspend but deferred
 102                  * probe makes that very unsafe.
 103                  */
 104                 device_pm_lock();
 105                 device_pm_move_last(dev);
 106                 device_pm_unlock();
 107
 108                 dev_dbg(dev, "Retrying from deferred list\n");
 109                 bus_probe_device(dev);
 110
 111                 mutex_lock(&deferred_probe_mutex);
 112
 113                 put_device(dev);
 114         }
 115         mutex_unlock(&deferred_probe_mutex);
 116 }
 117 static DECLARE_WORK(deferred_probe_work, deferred_probe_work_func);
 118
 119 static void driver_deferred_probe_add(struct device *dev)
 120 {
 121         mutex_lock(&deferred_probe_mutex);
 122         if (list_empty(&dev->p->deferred_probe)) {
 123                 dev_dbg(dev, "Added to deferred list\n");
 124                 list_add_tail(&dev->p->deferred_probe, &deferred_probe_pending_list);
 125         }
 126         mutex_unlock(&deferred_probe_mutex);
 127 }
 128
 129 void driver_deferred_probe_del(struct device *dev)
 130 {
 131         mutex_lock(&deferred_probe_mutex);
 132         if (!list_empty(&dev->p->deferred_probe)) {
 133                 dev_dbg(dev, "Removed from deferred list\n");
 134                 list_del_init(&dev->p->deferred_probe);
 135         }
 136         mutex_unlock(&deferred_probe_mutex);
 137 }
 138
 139 static bool driver_deferred_probe_enable = false;
 140 /**
 141  * driver_deferred_probe_trigger() - Kick off re-probing deferred devices
 142  *
 143  * This functions moves all devices from the pending list to the active
 144  * list and schedules the deferred probe workqueue to process them.  It
 145  * should be called anytime a driver is successfully bound to a device.
 146  *
 147  * Note, there is a race condition in multi-threaded probe. In the case where
 148  * more than one device is probing at the same time, it is possible for one
 149  * probe to complete successfully while another is about to defer. If the second
 150  * depends on the first, then it will get put on the pending list after the
 151  * trigger event has already occurred and will be stuck there.
 152  *
 153  * The atomic 'deferred_trigger_count' is used to determine if a successful
 154  * trigger has occurred in the midst of probing a driver. If the trigger count
 155  * changes in the midst of a probe, then deferred processing should be triggered
 156  * again.
 157  */
 158 static void driver_deferred_probe_trigger(void)
 159 {
 160         if (!driver_deferred_probe_enable)
 161                 return;
 162
 163         /*
 164          * A successful probe means that all the devices in the pending list
 165          * should be triggered to be reprobed.  Move all the deferred devices
 166          * into the active list so they can be retried by the workqueue
 167          */
 168         mutex_lock(&deferred_probe_mutex);
 169         atomic_inc(&deferred_trigger_count);
 170         list_splice_tail_init(&deferred_probe_pending_list,
 171                               &deferred_probe_active_list);
 172         mutex_unlock(&deferred_probe_mutex);
 173
 174         /*
 175          * Kick the re-probe thread.  It may already be scheduled, but it is
 176          * safe to kick it again.
 177          */
 178         queue_work(deferred_wq, &deferred_probe_work);
 179 }
 180
 181 /**
 182  * device_block_probing() - Block/defere device's probes
 183  *
 184  *      It will disable probing of devices and defer their probes instead.
 185  */
 186 void device_block_probing(void)
 187 {
 188         defer_all_probes = true;
 189         /* sync with probes to avoid races. */
 190         wait_for_device_probe();
 191 }
 192
 193 /**
 194  * device_unblock_probing() - Unblock/enable device's probes
 195  *
 196  *      It will restore normal behavior and trigger re-probing of deferred
 197  * devices.
 198  */
 199 void device_unblock_probing(void)
 200 {
 201         defer_all_probes = false;
 202         driver_deferred_probe_trigger();
 203 }
 204
 205 /**
 206  * deferred_probe_initcall() - Enable probing of deferred devices
 207  *
 208  * We don't want to get in the way when the bulk of drivers are getting probed.
 209  * Instead, this initcall makes sure that deferred probing is delayed until
 210  * late_initcall time.
 211  */
 212 static int deferred_probe_initcall(void)
 213 {
 214         deferred_wq = create_singlethread_workqueue("deferwq");
 215         if (WARN_ON(!deferred_wq))
 216                 return -ENOMEM;
 217
 218         driver_deferred_probe_enable = true;
 219         driver_deferred_probe_trigger();
 220         /* Sort as many dependencies as possible before exiting initcalls */
 221         flush_workqueue(deferred_wq);
 222         return 0;
 223 }
 224 late_initcall(deferred_probe_initcall);
 225
 226 /**
 227  * device_is_bound() - Check if device is bound to a driver
 228  * @dev: device to check
 229  *
 230  * Returns true if passed device has already finished probing successfully
 231  * against a driver.
 232  *
 233  * This function must be called with the device lock held.
 234  */
 235 bool device_is_bound(struct device *dev)
 236 {
 237         return klist_node_attached(&dev->p->knode_driver);
 238 }
 239
 240 static void driver_bound(struct device *dev)
 241 {
 242         if (device_is_bound(dev)) {
 243                 printk(KERN_WARNING "%s: device %s already bound\n",
 244                         __func__, kobject_name(&dev->kobj));
 245                 return;
 246         }
 247
 248         pr_debug("driver: '%s': %s: bound to device '%s'\n", dev->driver->name,
 249                  __func__, dev_name(dev));
 250
 251         klist_add_tail(&dev->p->knode_driver, &dev->driver->p->klist_devices);
 252
 253         device_pm_check_callbacks(dev);
 254
 255         /*
 256          * Make sure the device is no longer in one of the deferred lists and
 257          * kick off retrying all pending devices
 258          */
 259         driver_deferred_probe_del(dev);
 260         driver_deferred_probe_trigger();
 261
 262         if (dev->bus)
 263                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 264                                              BUS_NOTIFY_BOUND_DRIVER, dev);
 265 }
 266
 267 static int driver_sysfs_add(struct device *dev)
 268 {
 269         int ret;
 270
 271         if (dev->bus)
 272                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 273                                              BUS_NOTIFY_BIND_DRIVER, dev);
 274
 275         ret = sysfs_create_link(&dev->driver->p->kobj, &dev->kobj,
 276                           kobject_name(&dev->kobj));
 277         if (ret == 0) {
 278                 ret = sysfs_create_link(&dev->kobj, &dev->driver->p->kobj,
 279                                         "driver");
 280                 if (ret)
 281                         sysfs_remove_link(&dev->driver->p->kobj,
 282                                         kobject_name(&dev->kobj));
 283         }
 284         return ret;
 285 }
 286
 287 static void driver_sysfs_remove(struct device *dev)
 288 {
 289         struct device_driver *drv = dev->driver;
 290
 291         if (drv) {
 292                 sysfs_remove_link(&drv->p->kobj, kobject_name(&dev->kobj));
 293                 sysfs_remove_link(&dev->kobj, "driver");
 294         }
 295 }
 296
 297 /**
 298  * device_bind_driver - bind a driver to one device.
 299  * @dev: device.
 300  *
 301  * Allow manual attachment of a driver to a device.
 302  * Caller must have already set @dev->driver.
 303  *
 304  * Note that this does not modify the bus reference count
 305  * nor take the bus's rwsem. Please verify those are accounted
 306  * for before calling this. (It is ok to call with no other effort
 307  * from a driver's probe() method.)
 308  *
 309  * This function must be called with the device lock held.
 310  */
 311 int device_bind_driver(struct device *dev)
 312 {
 313         int ret;
 314
 315         ret = driver_sysfs_add(dev);
 316         if (!ret)
 317                 driver_bound(dev);
 318         else if (dev->bus)
 319                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 320                                              BUS_NOTIFY_DRIVER_NOT_BOUND, dev);
 321         return ret;
 322 }
 323 EXPORT_SYMBOL_GPL(device_bind_driver);
 324
 325 static atomic_t probe_count = ATOMIC_INIT(0);
 326 static DECLARE_WAIT_QUEUE_HEAD(probe_waitqueue);
 327
 328 static int really_probe(struct device *dev, struct device_driver *drv)
 329 {
 330         int ret = -EPROBE_DEFER;
 331         int local_trigger_count = atomic_read(&deferred_trigger_count);
 332
 333         if (defer_all_probes) {
 334                 /*
 335                  * Value of defer_all_probes can be set only by
 336                  * device_defer_all_probes_enable() which, in turn, will call
 337                  * wait_for_device_probe() right after that to avoid any races.
 338                  */
 339                 dev_dbg(dev, "Driver %s force probe deferral\n", drv->name);
 340                 driver_deferred_probe_add(dev);
 341                 return ret;
 342         }
 343
 344         atomic_inc(&probe_count);
 345         pr_debug("bus: '%s': %s: probing driver %s with device %s\n",
 346                  drv->bus->name, __func__, drv->name, dev_name(dev));
 347         WARN_ON(!list_empty(&dev->devres_head));
 348
 349         dev->driver = drv;
 350
 351         /* If using pinctrl, bind pins now before probing */
 352         ret = pinctrl_bind_pins(dev);
 353         if (ret)
 354                 goto pinctrl_bind_failed;
 355
 356         if (driver_sysfs_add(dev)) {
 357                 printk(KERN_ERR "%s: driver_sysfs_add(%s) failed\n",
 358                         __func__, dev_name(dev));
 359                 goto probe_failed;
 360         }
 361
 362         if (dev->pm_domain && dev->pm_domain->activate) {
 363                 ret = dev->pm_domain->activate(dev);
 364                 if (ret)
 365                         goto probe_failed;
 366         }
 367
 368         /*
 369          * Ensure devices are listed in devices_kset in correct order
 370          * It's important to move Dev to the end of devices_kset before
 371          * calling .probe, because it could be recursive and parent Dev
 372          * should always go first
 373          */
 374         devices_kset_move_last(dev);
 375
 376         if (dev->bus->probe) {
 377                 ret = dev->bus->probe(dev);
 378                 if (ret)
 379                         goto probe_failed;
 380         } else if (drv->probe) {
 381                 ret = drv->probe(dev);
 382                 if (ret)
 383                         goto probe_failed;
 384         }
 385
 386         pinctrl_init_done(dev);
 387
 388         if (dev->pm_domain && dev->pm_domain->sync)
 389                 dev->pm_domain->sync(dev);
 390
 391         driver_bound(dev);
 392         ret = 1;
 393         pr_debug("bus: '%s': %s: bound device %s to driver %s\n",
 394                  drv->bus->name, __func__, dev_name(dev), drv->name);
 395         goto done;
 396
 397 probe_failed:
 398         if (dev->bus)
 399                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 400                                              BUS_NOTIFY_DRIVER_NOT_BOUND, dev);
 401 pinctrl_bind_failed:
 402         devres_release_all(dev);
 403         driver_sysfs_remove(dev);
 404         dev->driver = NULL;
 405         dev_set_drvdata(dev, NULL);
 406         if (dev->pm_domain && dev->pm_domain->dismiss)
 407                 dev->pm_domain->dismiss(dev);
 408         pm_runtime_reinit(dev);
 409
 410         switch (ret) {
 411         case -EPROBE_DEFER:
 412                 /* Driver requested deferred probing */
 413                 dev_dbg(dev, "Driver %s requests probe deferral\n", drv->name);
 414                 driver_deferred_probe_add(dev);
 415                 /* Did a trigger occur while probing? Need to re-trigger if yes */
 416                 if (local_trigger_count != atomic_read(&deferred_trigger_count))
 417                         driver_deferred_probe_trigger();
 418                 break;
 419         case -ENODEV:
 420         case -ENXIO:
 421                 pr_debug("%s: probe of %s rejects match %d\n",
 422                          drv->name, dev_name(dev), ret);
 423                 break;
 424         default:
 425                 /* driver matched but the probe failed */
 426                 printk(KERN_WARNING
 427                        "%s: probe of %s failed with error %d\n",
 428                        drv->name, dev_name(dev), ret);
 429         }
 430         /*
 431          * Ignore errors returned by ->probe so that the next driver can try
 432          * its luck.
 433          */
 434         ret = 0;
 435 done:
 436         atomic_dec(&probe_count);
 437         wake_up(&probe_waitqueue);
 438         return ret;
 439 }
 440
 441 /**
 442  * driver_probe_done
 443  * Determine if the probe sequence is finished or not.
 444  *
 445  * Should somehow figure out how to use a semaphore, not an atomic variable...
 446  */
 447 int driver_probe_done(void)
 448 {
 449         pr_debug("%s: probe_count = %d\n", __func__,
 450                  atomic_read(&probe_count));
 451         if (atomic_read(&probe_count))
 452                 return -EBUSY;
 453         return 0;
 454 }
 455
 456 /**
 457  * wait_for_device_probe
 458  * Wait for device probing to be completed.
 459  */
 460 void wait_for_device_probe(void)
 461 {
 462         /* wait for the deferred probe workqueue to finish */
 463         if (driver_deferred_probe_enable)
 464                 flush_workqueue(deferred_wq);
 465
 466         /* wait for the known devices to complete their probing */
 467         wait_event(probe_waitqueue, atomic_read(&probe_count) == 0);
 468         async_synchronize_full();
 469 }
 470 EXPORT_SYMBOL_GPL(wait_for_device_probe);
 471
 472 /**
 473  * driver_probe_device - attempt to bind device & driver together
 474  * @drv: driver to bind a device to
 475  * @dev: device to try to bind to the driver
 476  *
 477  * This function returns -ENODEV if the device is not registered,
 478  * 1 if the device is bound successfully and 0 otherwise.
 479  *
 480  * This function must be called with @dev lock held.  When called for a
 481  * USB interface, @dev->parent lock must be held as well.
 482  *
 483  * If the device has a parent, runtime-resume the parent before driver probing.
 484  */
 485 int driver_probe_device(struct device_driver *drv, struct device *dev)
 486 {
 487         int ret = 0;
 488
 489         if (!device_is_registered(dev))
 490                 return -ENODEV;
 491
 492         pr_debug("bus: '%s': %s: matched device %s with driver %s\n",
 493                  drv->bus->name, __func__, dev_name(dev), drv->name);
 494
 495         if (dev->parent)
 496                 pm_runtime_get_sync(dev->parent);
 497
 498         pm_runtime_barrier(dev);
 499         ret = really_probe(dev, drv);
 500         pm_request_idle(dev);
 501
 502         if (dev->parent)
 503                 pm_runtime_put(dev->parent);
 504
 505         return ret;
 506 }
 507
 508 bool driver_allows_async_probing(struct device_driver *drv)
 509 {
 510         switch (drv->probe_type) {
 511         case PROBE_PREFER_ASYNCHRONOUS:
 512                 return true;
 513
 514         case PROBE_FORCE_SYNCHRONOUS:
 515                 return false;
 516
 517         default:
 518                 if (module_requested_async_probing(drv->owner))
 519                         return true;
 520
 521                 return false;
 522         }
 523 }
 524
 525 struct device_attach_data {
 526         struct device *dev;
 527
 528         /*
 529          * Indicates whether we are are considering asynchronous probing or
 530          * not. Only initial binding after device or driver registration
 531          * (including deferral processing) may be done asynchronously, the
 532          * rest is always synchronous, as we expect it is being done by
 533          * request from userspace.
 534          */
 535         bool check_async;
 536
 537         /*
 538          * Indicates if we are binding synchronous or asynchronous drivers.
 539          * When asynchronous probing is enabled we'll execute 2 passes
 540          * over drivers: first pass doing synchronous probing and second
 541          * doing asynchronous probing (if synchronous did not succeed -
 542          * most likely because there was no driver requiring synchronous
 543          * probing - and we found asynchronous driver during first pass).
 544          * The 2 passes are done because we can't shoot asynchronous
 545          * probe for given device and driver from bus_for_each_drv() since
 546          * driver pointer is not guaranteed to stay valid once
 547          * bus_for_each_drv() iterates to the next driver on the bus.
 548          */
 549         bool want_async;
 550
 551         /*
 552          * We'll set have_async to 'true' if, while scanning for matching
 553          * driver, we'll encounter one that requests asynchronous probing.
 554          */
 555         bool have_async;
 556 };
 557
 558 static int __device_attach_driver(struct device_driver *drv, void *_data)
 559 {
 560         struct device_attach_data *data = _data;
 561         struct device *dev = data->dev;
 562         bool async_allowed;
 563
 564         /*
 565          * Check if device has already been claimed. This may
 566          * happen with driver loading, device discovery/registration,
 567          * and deferred probe processing happens all at once with
 568          * multiple threads.
 569          */
 570         if (dev->driver)
 571                 return -EBUSY;
 572
 573         if (!driver_match_device(drv, dev))
 574                 return 0;
 575
 576         async_allowed = driver_allows_async_probing(drv);
 577
 578         if (async_allowed)
 579                 data->have_async = true;
 580
 581         if (data->check_async && async_allowed != data->want_async)
 582                 return 0;
 583
 584         return driver_probe_device(drv, dev);
 585 }
 586
 587 static void __device_attach_async_helper(void *_dev, async_cookie_t cookie)
 588 {
 589         struct device *dev = _dev;
 590         struct device_attach_data data = {
 591                 .dev            = dev,
 592                 .check_async    = true,
 593                 .want_async     = true,
 594         };
 595
 596         device_lock(dev);
 597
 598         if (dev->parent)
 599                 pm_runtime_get_sync(dev->parent);
 600
 601         bus_for_each_drv(dev->bus, NULL, &data, __device_attach_driver);
 602         dev_dbg(dev, "async probe completed\n");
 603
 604         pm_request_idle(dev);
 605
 606         if (dev->parent)
 607                 pm_runtime_put(dev->parent);
 608
 609         device_unlock(dev);
 610
 611         put_device(dev);
 612 }
 613
 614 static int __device_attach(struct device *dev, bool allow_async)
 615 {
 616         int ret = 0;
 617
 618         device_lock(dev);
 619         if (dev->driver) {
 620                 if (device_is_bound(dev)) {
 621                         ret = 1;
 622                         goto out_unlock;
 623                 }
 624                 ret = device_bind_driver(dev);
 625                 if (ret == 0)
 626                         ret = 1;
 627                 else {
 628                         dev->driver = NULL;
 629                         ret = 0;
 630                 }
 631         } else {
 632                 struct device_attach_data data = {
 633                         .dev = dev,
 634                         .check_async = allow_async,
 635                         .want_async = false,
 636                 };
 637
 638                 if (dev->parent)
 639                         pm_runtime_get_sync(dev->parent);
 640
 641                 ret = bus_for_each_drv(dev->bus, NULL, &data,
 642                                         __device_attach_driver);
 643                 if (!ret && allow_async && data.have_async) {
 644                         /*
 645                          * If we could not find appropriate driver
 646                          * synchronously and we are allowed to do
 647                          * async probes and there are drivers that
 648                          * want to probe asynchronously, we'll
 649                          * try them.
 650                          */
 651                         dev_dbg(dev, "scheduling asynchronous probe\n");
 652                         get_device(dev);
 653                         async_schedule(__device_attach_async_helper, dev);
 654                 } else {
 655                         pm_request_idle(dev);
 656                 }
 657
 658                 if (dev->parent)
 659                         pm_runtime_put(dev->parent);
 660         }
 661 out_unlock:
 662         device_unlock(dev);
 663         return ret;
 664 }
 665
 666 /**
 667  * device_attach - try to attach device to a driver.
 668  * @dev: device.
 669  *
 670  * Walk the list of drivers that the bus has and call
 671  * driver_probe_device() for each pair. If a compatible
 672  * pair is found, break out and return.
 673  *
 674  * Returns 1 if the device was bound to a driver;
 675  * 0 if no matching driver was found;
 676  * -ENODEV if the device is not registered.
 677  *
 678  * When called for a USB interface, @dev->parent lock must be held.
 679  */
 680 int device_attach(struct device *dev)
 681 {
 682         return __device_attach(dev, false);
 683 }
 684 EXPORT_SYMBOL_GPL(device_attach);
 685
 686 void device_initial_probe(struct device *dev)
 687 {
 688         __device_attach(dev, true);
 689 }
 690
 691 static int __driver_attach(struct device *dev, void *data)
 692 {
 693         struct device_driver *drv = data;
 694
 695         /*
 696          * Lock device and try to bind to it. We drop the error
 697          * here and always return 0, because we need to keep trying
 698          * to bind to devices and some drivers will return an error
 699          * simply if it didn't support the device.
 700          *
 701          * driver_probe_device() will spit a warning if there
 702          * is an error.
 703          */
 704
 705         if (!driver_match_device(drv, dev))
 706                 return 0;
 707
 708         if (dev->parent)        /* Needed for USB */
 709                 device_lock(dev->parent);
 710         device_lock(dev);
 711         if (!dev->driver)
 712                 driver_probe_device(drv, dev);
 713         device_unlock(dev);
 714         if (dev->parent)
 715                 device_unlock(dev->parent);
 716
 717         return 0;
 718 }
 719
 720 /**
 721  * driver_attach - try to bind driver to devices.
 722  * @drv: driver.
 723  *
 724  * Walk the list of devices that the bus has on it and try to
 725  * match the driver with each one.  If driver_probe_device()
 726  * returns 0 and the @dev->driver is set, we've found a
 727  * compatible pair.
 728  */
 729 int driver_attach(struct device_driver *drv)
 730 {
 731         return bus_for_each_dev(drv->bus, NULL, drv, __driver_attach);
 732 }
 733 EXPORT_SYMBOL_GPL(driver_attach);
 734
 735 /*
 736  * __device_release_driver() must be called with @dev lock held.
 737  * When called for a USB interface, @dev->parent lock must be held as well.
 738  */
 739 static void __device_release_driver(struct device *dev)
 740 {
 741         struct device_driver *drv;
 742
 743         drv = dev->driver;
 744         if (drv) {
 745                 if (driver_allows_async_probing(drv))
 746                         async_synchronize_full();
 747
 748                 pm_runtime_get_sync(dev);
 749
 750                 driver_sysfs_remove(dev);
 751
 752                 if (dev->bus)
 753                         blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 754                                                      BUS_NOTIFY_UNBIND_DRIVER,
 755                                                      dev);
 756
 757                 pm_runtime_put_sync(dev);
 758
 759                 if (dev->bus && dev->bus->remove)
 760                         dev->bus->remove(dev);
 761                 else if (drv->remove)
 762                         drv->remove(dev);
 763                 devres_release_all(dev);
 764                 dev->driver = NULL;
 765                 dev_set_drvdata(dev, NULL);
 766                 if (dev->pm_domain && dev->pm_domain->dismiss)
 767                         dev->pm_domain->dismiss(dev);
 768                 pm_runtime_reinit(dev);
 769
 770                 klist_remove(&dev->p->knode_driver);
 771                 device_pm_check_callbacks(dev);
 772                 if (dev->bus)
 773                         blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 774                                                      BUS_NOTIFY_UNBOUND_DRIVER,
 775                                                      dev);
 776         }
 777 }
 778
 779 /**
 780  * device_release_driver - manually detach device from driver.
 781  * @dev: device.
 782  *
 783  * Manually detach device from driver.
 784  * When called for a USB interface, @dev->parent lock must be held.
 785  */
 786 void device_release_driver(struct device *dev)
 787 {
 788         /*
 789          * If anyone calls device_release_driver() recursively from
 790          * within their ->remove callback for the same device, they
 791          * will deadlock right here.
 792          */
 793         device_lock(dev);
 794         __device_release_driver(dev);
 795         device_unlock(dev);
 796 }
 797 EXPORT_SYMBOL_GPL(device_release_driver);
 798
 799 /**
 800  * driver_detach - detach driver from all devices it controls.
 801  * @drv: driver.
 802  */
 803 void driver_detach(struct device_driver *drv)
 804 {
 805         struct device_private *dev_prv;
 806         struct device *dev;
 807
 808         for (;;) {
 809                 spin_lock(&drv->p->klist_devices.k_lock);
 810                 if (list_empty(&drv->p->klist_devices.k_list)) {
 811                         spin_unlock(&drv->p->klist_devices.k_lock);
 812                         break;
 813                 }
 814                 dev_prv = list_entry(drv->p->klist_devices.k_list.prev,
 815                                      struct device_private,
 816                                      knode_driver.n_node);
 817                 dev = dev_prv->device;
 818                 get_device(dev);
 819                 spin_unlock(&drv->p->klist_devices.k_lock);
 820
 821                 if (dev->parent)        /* Needed for USB */
 822                         device_lock(dev->parent);
 823                 device_lock(dev);
 824                 if (dev->driver == drv)
 825                         __device_release_driver(dev);
 826                 device_unlock(dev);
 827                 if (dev->parent)
 828                         device_unlock(dev->parent);
 829                 put_device(dev);
 830         }
 831 }