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 atomic_t deferred_trigger_count = ATOMIC_INIT(0);
  55
  56 /*
  57  * In some cases, like suspend to RAM or hibernation, It might be reasonable
  58  * to prohibit probing of devices as it could be unsafe.
  59  * Once defer_all_probes is true all drivers probes will be forcibly deferred.
  60  */
  61 static bool defer_all_probes;
  62
  63 /*
  64  * deferred_probe_work_func() - Retry probing devices in the active list.
  65  */
  66 static void deferred_probe_work_func(struct work_struct *work)
  67 {
  68         struct device *dev;
  69         struct device_private *private;
  70         /*
  71          * This block processes every device in the deferred 'active' list.
  72          * Each device is removed from the active list and passed to
  73          * bus_probe_device() to re-attempt the probe.  The loop continues
  74          * until every device in the active list is removed and retried.
  75          *
  76          * Note: Once the device is removed from the list and the mutex is
  77          * released, it is possible for the device get freed by another thread
  78          * and cause a illegal pointer dereference.  This code uses
  79          * get/put_device() to ensure the device structure cannot disappear
  80          * from under our feet.
  81          */
  82         mutex_lock(&deferred_probe_mutex);
  83         while (!list_empty(&deferred_probe_active_list)) {
  84                 private = list_first_entry(&deferred_probe_active_list,
  85                                         typeof(*dev->p), deferred_probe);
  86                 dev = private->device;
  87                 list_del_init(&private->deferred_probe);
  88
  89                 get_device(dev);
  90
  91                 /*
  92                  * Drop the mutex while probing each device; the probe path may
  93                  * manipulate the deferred list
  94                  */
  95                 mutex_unlock(&deferred_probe_mutex);
  96
  97                 /*
  98                  * Force the device to the end of the dpm_list since
  99                  * the PM code assumes that the order we add things to
 100                  * the list is a good order for suspend but deferred
 101                  * probe makes that very unsafe.
 102                  */
 103                 device_pm_lock();
 104                 device_pm_move_last(dev);
 105                 device_pm_unlock();
 106
 107                 dev_dbg(dev, "Retrying from deferred list\n");
 108                 bus_probe_device(dev);
 109
 110                 mutex_lock(&deferred_probe_mutex);
 111
 112                 put_device(dev);
 113         }
 114         mutex_unlock(&deferred_probe_mutex);
 115 }
 116 static DECLARE_WORK(deferred_probe_work, deferred_probe_work_func);
 117
 118 static void driver_deferred_probe_add(struct device *dev)
 119 {
 120         mutex_lock(&deferred_probe_mutex);
 121         if (list_empty(&dev->p->deferred_probe)) {
 122                 dev_dbg(dev, "Added to deferred list\n");
 123                 list_add_tail(&dev->p->deferred_probe, &deferred_probe_pending_list);
 124         }
 125         mutex_unlock(&deferred_probe_mutex);
 126 }
 127
 128 void driver_deferred_probe_del(struct device *dev)
 129 {
 130         mutex_lock(&deferred_probe_mutex);
 131         if (!list_empty(&dev->p->deferred_probe)) {
 132                 dev_dbg(dev, "Removed from deferred list\n");
 133                 list_del_init(&dev->p->deferred_probe);
 134         }
 135         mutex_unlock(&deferred_probe_mutex);
 136 }
 137
 138 static bool driver_deferred_probe_enable = false;
 139 /**
 140  * driver_deferred_probe_trigger() - Kick off re-probing deferred devices
 141  *
 142  * This functions moves all devices from the pending list to the active
 143  * list and schedules the deferred probe workqueue to process them.  It
 144  * should be called anytime a driver is successfully bound to a device.
 145  *
 146  * Note, there is a race condition in multi-threaded probe. In the case where
 147  * more than one device is probing at the same time, it is possible for one
 148  * probe to complete successfully while another is about to defer. If the second
 149  * depends on the first, then it will get put on the pending list after the
 150  * trigger event has already occurred and will be stuck there.
 151  *
 152  * The atomic 'deferred_trigger_count' is used to determine if a successful
 153  * trigger has occurred in the midst of probing a driver. If the trigger count
 154  * changes in the midst of a probe, then deferred processing should be triggered
 155  * again.
 156  */
 157 static void driver_deferred_probe_trigger(void)
 158 {
 159         if (!driver_deferred_probe_enable)
 160                 return;
 161
 162         /*
 163          * A successful probe means that all the devices in the pending list
 164          * should be triggered to be reprobed.  Move all the deferred devices
 165          * into the active list so they can be retried by the workqueue
 166          */
 167         mutex_lock(&deferred_probe_mutex);
 168         atomic_inc(&deferred_trigger_count);
 169         list_splice_tail_init(&deferred_probe_pending_list,
 170                               &deferred_probe_active_list);
 171         mutex_unlock(&deferred_probe_mutex);
 172
 173         /*
 174          * Kick the re-probe thread.  It may already be scheduled, but it is
 175          * safe to kick it again.
 176          */
 177         schedule_work(&deferred_probe_work);
 178 }
 179
 180 /**
 181  * device_block_probing() - Block/defere device's probes
 182  *
 183  *      It will disable probing of devices and defer their probes instead.
 184  */
 185 void device_block_probing(void)
 186 {
 187         defer_all_probes = true;
 188         /* sync with probes to avoid races. */
 189         wait_for_device_probe();
 190 }
 191
 192 /**
 193  * device_unblock_probing() - Unblock/enable device's probes
 194  *
 195  *      It will restore normal behavior and trigger re-probing of deferred
 196  * devices.
 197  */
 198 void device_unblock_probing(void)
 199 {
 200         defer_all_probes = false;
 201         driver_deferred_probe_trigger();
 202 }
 203
 204 /**
 205  * deferred_probe_initcall() - Enable probing of deferred devices
 206  *
 207  * We don't want to get in the way when the bulk of drivers are getting probed.
 208  * Instead, this initcall makes sure that deferred probing is delayed until
 209  * late_initcall time.
 210  */
 211 static int deferred_probe_initcall(void)
 212 {
 213         driver_deferred_probe_enable = true;
 214         driver_deferred_probe_trigger();
 215         /* Sort as many dependencies as possible before exiting initcalls */
 216         flush_work(&deferred_probe_work);
 217         return 0;
 218 }
 219 late_initcall(deferred_probe_initcall);
 220
 221 /**
 222  * device_is_bound() - Check if device is bound to a driver
 223  * @dev: device to check
 224  *
 225  * Returns true if passed device has already finished probing successfully
 226  * against a driver.
 227  *
 228  * This function must be called with the device lock held.
 229  */
 230 bool device_is_bound(struct device *dev)
 231 {
 232         return dev->p && klist_node_attached(&dev->p->knode_driver);
 233 }
 234
 235 static void driver_bound(struct device *dev)
 236 {
 237         if (device_is_bound(dev)) {
 238                 printk(KERN_WARNING "%s: device %s already bound\n",
 239                         __func__, kobject_name(&dev->kobj));
 240                 return;
 241         }
 242
 243         pr_debug("driver: '%s': %s: bound to device '%s'\n", dev->driver->name,
 244                  __func__, dev_name(dev));
 245
 246         klist_add_tail(&dev->p->knode_driver, &dev->driver->p->klist_devices);
 247         device_links_driver_bound(dev);
 248
 249         device_pm_check_callbacks(dev);
 250
 251         /*
 252          * Make sure the device is no longer in one of the deferred lists and
 253          * kick off retrying all pending devices
 254          */
 255         driver_deferred_probe_del(dev);
 256         driver_deferred_probe_trigger();
 257
 258         if (dev->bus)
 259                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 260                                              BUS_NOTIFY_BOUND_DRIVER, dev);
 261 }
 262
 263 static int driver_sysfs_add(struct device *dev)
 264 {
 265         int ret;
 266
 267         if (dev->bus)
 268                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 269                                              BUS_NOTIFY_BIND_DRIVER, dev);
 270
 271         ret = sysfs_create_link(&dev->driver->p->kobj, &dev->kobj,
 272                           kobject_name(&dev->kobj));
 273         if (ret == 0) {
 274                 ret = sysfs_create_link(&dev->kobj, &dev->driver->p->kobj,
 275                                         "driver");
 276                 if (ret)
 277                         sysfs_remove_link(&dev->driver->p->kobj,
 278                                         kobject_name(&dev->kobj));
 279         }
 280         return ret;
 281 }
 282
 283 static void driver_sysfs_remove(struct device *dev)
 284 {
 285         struct device_driver *drv = dev->driver;
 286
 287         if (drv) {
 288                 sysfs_remove_link(&drv->p->kobj, kobject_name(&dev->kobj));
 289                 sysfs_remove_link(&dev->kobj, "driver");
 290         }
 291 }
 292
 293 /**
 294  * device_bind_driver - bind a driver to one device.
 295  * @dev: device.
 296  *
 297  * Allow manual attachment of a driver to a device.
 298  * Caller must have already set @dev->driver.
 299  *
 300  * Note that this does not modify the bus reference count
 301  * nor take the bus's rwsem. Please verify those are accounted
 302  * for before calling this. (It is ok to call with no other effort
 303  * from a driver's probe() method.)
 304  *
 305  * This function must be called with the device lock held.
 306  */
 307 int device_bind_driver(struct device *dev)
 308 {
 309         int ret;
 310
 311         ret = driver_sysfs_add(dev);
 312         if (!ret)
 313                 driver_bound(dev);
 314         else if (dev->bus)
 315                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 316                                              BUS_NOTIFY_DRIVER_NOT_BOUND, dev);
 317         return ret;
 318 }
 319 EXPORT_SYMBOL_GPL(device_bind_driver);
 320
 321 static atomic_t probe_count = ATOMIC_INIT(0);
 322 static DECLARE_WAIT_QUEUE_HEAD(probe_waitqueue);
 323
 324 static int really_probe(struct device *dev, struct device_driver *drv)
 325 {
 326         int ret = -EPROBE_DEFER;
 327         int local_trigger_count = atomic_read(&deferred_trigger_count);
 328         bool test_remove = IS_ENABLED(CONFIG_DEBUG_TEST_DRIVER_REMOVE) &&
 329                            !drv->suppress_bind_attrs;
 330
 331         if (defer_all_probes) {
 332                 /*
 333                  * Value of defer_all_probes can be set only by
 334                  * device_defer_all_probes_enable() which, in turn, will call
 335                  * wait_for_device_probe() right after that to avoid any races.
 336                  */
 337                 dev_dbg(dev, "Driver %s force probe deferral\n", drv->name);
 338                 driver_deferred_probe_add(dev);
 339                 return ret;
 340         }
 341
 342         ret = device_links_check_suppliers(dev);
 343         if (ret)
 344                 return ret;
 345
 346         atomic_inc(&probe_count);
 347         pr_debug("bus: '%s': %s: probing driver %s with device %s\n",
 348                  drv->bus->name, __func__, drv->name, dev_name(dev));
 349         WARN_ON(!list_empty(&dev->devres_head));
 350
 351 re_probe:
 352         dev->driver = drv;
 353
 354         /* If using pinctrl, bind pins now before probing */
 355         ret = pinctrl_bind_pins(dev);
 356         if (ret)
 357                 goto pinctrl_bind_failed;
 358
 359         if (driver_sysfs_add(dev)) {
 360                 printk(KERN_ERR "%s: driver_sysfs_add(%s) failed\n",
 361                         __func__, dev_name(dev));
 362                 goto probe_failed;
 363         }
 364
 365         if (dev->pm_domain && dev->pm_domain->activate) {
 366                 ret = dev->pm_domain->activate(dev);
 367                 if (ret)
 368                         goto probe_failed;
 369         }
 370
 371         /*
 372          * Ensure devices are listed in devices_kset in correct order
 373          * It's important to move Dev to the end of devices_kset before
 374          * calling .probe, because it could be recursive and parent Dev
 375          * should always go first
 376          */
 377         devices_kset_move_last(dev);
 378
 379         if (dev->bus->probe) {
 380                 ret = dev->bus->probe(dev);
 381                 if (ret)
 382                         goto probe_failed;
 383         } else if (drv->probe) {
 384                 ret = drv->probe(dev);
 385                 if (ret)
 386                         goto probe_failed;
 387         }
 388
 389         if (test_remove) {
 390                 test_remove = false;
 391
 392                 if (dev->bus->remove)
 393                         dev->bus->remove(dev);
 394                 else if (drv->remove)
 395                         drv->remove(dev);
 396
 397                 devres_release_all(dev);
 398                 driver_sysfs_remove(dev);
 399                 dev->driver = NULL;
 400                 dev_set_drvdata(dev, NULL);
 401                 if (dev->pm_domain && dev->pm_domain->dismiss)
 402                         dev->pm_domain->dismiss(dev);
 403                 pm_runtime_reinit(dev);
 404
 405                 goto re_probe;
 406         }
 407
 408         pinctrl_init_done(dev);
 409
 410         if (dev->pm_domain && dev->pm_domain->sync)
 411                 dev->pm_domain->sync(dev);
 412
 413         driver_bound(dev);
 414         ret = 1;
 415         pr_debug("bus: '%s': %s: bound device %s to driver %s\n",
 416                  drv->bus->name, __func__, dev_name(dev), drv->name);
 417         goto done;
 418
 419 probe_failed:
 420         if (dev->bus)
 421                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 422                                              BUS_NOTIFY_DRIVER_NOT_BOUND, dev);
 423 pinctrl_bind_failed:
 424         device_links_no_driver(dev);
 425         devres_release_all(dev);
 426         driver_sysfs_remove(dev);
 427         dev->driver = NULL;
 428         dev_set_drvdata(dev, NULL);
 429         if (dev->pm_domain && dev->pm_domain->dismiss)
 430                 dev->pm_domain->dismiss(dev);
 431         pm_runtime_reinit(dev);
 432
 433         switch (ret) {
 434         case -EPROBE_DEFER:
 435                 /* Driver requested deferred probing */
 436                 dev_dbg(dev, "Driver %s requests probe deferral\n", drv->name);
 437                 driver_deferred_probe_add(dev);
 438                 /* Did a trigger occur while probing? Need to re-trigger if yes */
 439                 if (local_trigger_count != atomic_read(&deferred_trigger_count))
 440                         driver_deferred_probe_trigger();
 441                 break;
 442         case -ENODEV:
 443         case -ENXIO:
 444                 pr_debug("%s: probe of %s rejects match %d\n",
 445                          drv->name, dev_name(dev), ret);
 446                 break;
 447         default:
 448                 /* driver matched but the probe failed */
 449                 printk(KERN_WARNING
 450                        "%s: probe of %s failed with error %d\n",
 451                        drv->name, dev_name(dev), ret);
 452         }
 453         /*
 454          * Ignore errors returned by ->probe so that the next driver can try
 455          * its luck.
 456          */
 457         ret = 0;
 458 done:
 459         atomic_dec(&probe_count);
 460         wake_up(&probe_waitqueue);
 461         return ret;
 462 }
 463
 464 /**
 465  * driver_probe_done
 466  * Determine if the probe sequence is finished or not.
 467  *
 468  * Should somehow figure out how to use a semaphore, not an atomic variable...
 469  */
 470 int driver_probe_done(void)
 471 {
 472         pr_debug("%s: probe_count = %d\n", __func__,
 473                  atomic_read(&probe_count));
 474         if (atomic_read(&probe_count))
 475                 return -EBUSY;
 476         return 0;
 477 }
 478
 479 /**
 480  * wait_for_device_probe
 481  * Wait for device probing to be completed.
 482  */
 483 void wait_for_device_probe(void)
 484 {
 485         /* wait for the deferred probe workqueue to finish */
 486         flush_work(&deferred_probe_work);
 487
 488         /* wait for the known devices to complete their probing */
 489         wait_event(probe_waitqueue, atomic_read(&probe_count) == 0);
 490         async_synchronize_full();
 491 }
 492 EXPORT_SYMBOL_GPL(wait_for_device_probe);
 493
 494 /**
 495  * driver_probe_device - attempt to bind device & driver together
 496  * @drv: driver to bind a device to
 497  * @dev: device to try to bind to the driver
 498  *
 499  * This function returns -ENODEV if the device is not registered,
 500  * 1 if the device is bound successfully and 0 otherwise.
 501  *
 502  * This function must be called with @dev lock held.  When called for a
 503  * USB interface, @dev->parent lock must be held as well.
 504  *
 505  * If the device has a parent, runtime-resume the parent before driver probing.
 506  */
 507 int driver_probe_device(struct device_driver *drv, struct device *dev)
 508 {
 509         int ret = 0;
 510
 511         if (!device_is_registered(dev))
 512                 return -ENODEV;
 513
 514         pr_debug("bus: '%s': %s: matched device %s with driver %s\n",
 515                  drv->bus->name, __func__, dev_name(dev), drv->name);
 516
 517         pm_runtime_get_suppliers(dev);
 518         if (dev->parent)
 519                 pm_runtime_get_sync(dev->parent);
 520
 521         pm_runtime_barrier(dev);
 522         ret = really_probe(dev, drv);
 523         pm_request_idle(dev);
 524
 525         if (dev->parent)
 526                 pm_runtime_put(dev->parent);
 527
 528         pm_runtime_put_suppliers(dev);
 529         return ret;
 530 }
 531
 532 bool driver_allows_async_probing(struct device_driver *drv)
 533 {
 534         switch (drv->probe_type) {
 535         case PROBE_PREFER_ASYNCHRONOUS:
 536                 return true;
 537
 538         case PROBE_FORCE_SYNCHRONOUS:
 539                 return false;
 540
 541         default:
 542                 if (module_requested_async_probing(drv->owner))
 543                         return true;
 544
 545                 return false;
 546         }
 547 }
 548
 549 struct device_attach_data {
 550         struct device *dev;
 551
 552         /*
 553          * Indicates whether we are are considering asynchronous probing or
 554          * not. Only initial binding after device or driver registration
 555          * (including deferral processing) may be done asynchronously, the
 556          * rest is always synchronous, as we expect it is being done by
 557          * request from userspace.
 558          */
 559         bool check_async;
 560
 561         /*
 562          * Indicates if we are binding synchronous or asynchronous drivers.
 563          * When asynchronous probing is enabled we'll execute 2 passes
 564          * over drivers: first pass doing synchronous probing and second
 565          * doing asynchronous probing (if synchronous did not succeed -
 566          * most likely because there was no driver requiring synchronous
 567          * probing - and we found asynchronous driver during first pass).
 568          * The 2 passes are done because we can't shoot asynchronous
 569          * probe for given device and driver from bus_for_each_drv() since
 570          * driver pointer is not guaranteed to stay valid once
 571          * bus_for_each_drv() iterates to the next driver on the bus.
 572          */
 573         bool want_async;
 574
 575         /*
 576          * We'll set have_async to 'true' if, while scanning for matching
 577          * driver, we'll encounter one that requests asynchronous probing.
 578          */
 579         bool have_async;
 580 };
 581
 582 static int __device_attach_driver(struct device_driver *drv, void *_data)
 583 {
 584         struct device_attach_data *data = _data;
 585         struct device *dev = data->dev;
 586         bool async_allowed;
 587         int ret;
 588
 589         /*
 590          * Check if device has already been claimed. This may
 591          * happen with driver loading, device discovery/registration,
 592          * and deferred probe processing happens all at once with
 593          * multiple threads.
 594          */
 595         if (dev->driver)
 596                 return -EBUSY;
 597
 598         ret = driver_match_device(drv, dev);
 599         if (ret == 0) {
 600                 /* no match */
 601                 return 0;
 602         } else if (ret == -EPROBE_DEFER) {
 603                 dev_dbg(dev, "Device match requests probe deferral\n");
 604                 driver_deferred_probe_add(dev);
 605         } else if (ret < 0) {
 606                 dev_dbg(dev, "Bus failed to match device: %d", ret);
 607                 return ret;
 608         } /* ret > 0 means positive match */
 609
 610         async_allowed = driver_allows_async_probing(drv);
 611
 612         if (async_allowed)
 613                 data->have_async = true;
 614
 615         if (data->check_async && async_allowed != data->want_async)
 616                 return 0;
 617
 618         return driver_probe_device(drv, dev);
 619 }
 620
 621 static void __device_attach_async_helper(void *_dev, async_cookie_t cookie)
 622 {
 623         struct device *dev = _dev;
 624         struct device_attach_data data = {
 625                 .dev            = dev,
 626                 .check_async    = true,
 627                 .want_async     = true,
 628         };
 629
 630         device_lock(dev);
 631
 632         if (dev->parent)
 633                 pm_runtime_get_sync(dev->parent);
 634
 635         bus_for_each_drv(dev->bus, NULL, &data, __device_attach_driver);
 636         dev_dbg(dev, "async probe completed\n");
 637
 638         pm_request_idle(dev);
 639
 640         if (dev->parent)
 641                 pm_runtime_put(dev->parent);
 642
 643         device_unlock(dev);
 644
 645         put_device(dev);
 646 }
 647
 648 static int __device_attach(struct device *dev, bool allow_async)
 649 {
 650         int ret = 0;
 651
 652         device_lock(dev);
 653         if (dev->driver) {
 654                 if (device_is_bound(dev)) {
 655                         ret = 1;
 656                         goto out_unlock;
 657                 }
 658                 ret = device_bind_driver(dev);
 659                 if (ret == 0)
 660                         ret = 1;
 661                 else {
 662                         dev->driver = NULL;
 663                         ret = 0;
 664                 }
 665         } else {
 666                 struct device_attach_data data = {
 667                         .dev = dev,
 668                         .check_async = allow_async,
 669                         .want_async = false,
 670                 };
 671
 672                 if (dev->parent)
 673                         pm_runtime_get_sync(dev->parent);
 674
 675                 ret = bus_for_each_drv(dev->bus, NULL, &data,
 676                                         __device_attach_driver);
 677                 if (!ret && allow_async && data.have_async) {
 678                         /*
 679                          * If we could not find appropriate driver
 680                          * synchronously and we are allowed to do
 681                          * async probes and there are drivers that
 682                          * want to probe asynchronously, we'll
 683                          * try them.
 684                          */
 685                         dev_dbg(dev, "scheduling asynchronous probe\n");
 686                         get_device(dev);
 687                         async_schedule(__device_attach_async_helper, dev);
 688                 } else {
 689                         pm_request_idle(dev);
 690                 }
 691
 692                 if (dev->parent)
 693                         pm_runtime_put(dev->parent);
 694         }
 695 out_unlock:
 696         device_unlock(dev);
 697         return ret;
 698 }
 699
 700 /**
 701  * device_attach - try to attach device to a driver.
 702  * @dev: device.
 703  *
 704  * Walk the list of drivers that the bus has and call
 705  * driver_probe_device() for each pair. If a compatible
 706  * pair is found, break out and return.
 707  *
 708  * Returns 1 if the device was bound to a driver;
 709  * 0 if no matching driver was found;
 710  * -ENODEV if the device is not registered.
 711  *
 712  * When called for a USB interface, @dev->parent lock must be held.
 713  */
 714 int device_attach(struct device *dev)
 715 {
 716         return __device_attach(dev, false);
 717 }
 718 EXPORT_SYMBOL_GPL(device_attach);
 719
 720 void device_initial_probe(struct device *dev)
 721 {
 722         __device_attach(dev, true);
 723 }
 724
 725 static int __driver_attach(struct device *dev, void *data)
 726 {
 727         struct device_driver *drv = data;
 728         int ret;
 729
 730         /*
 731          * Lock device and try to bind to it. We drop the error
 732          * here and always return 0, because we need to keep trying
 733          * to bind to devices and some drivers will return an error
 734          * simply if it didn't support the device.
 735          *
 736          * driver_probe_device() will spit a warning if there
 737          * is an error.
 738          */
 739
 740         ret = driver_match_device(drv, dev);
 741         if (ret == 0) {
 742                 /* no match */
 743                 return 0;
 744         } else if (ret == -EPROBE_DEFER) {
 745                 dev_dbg(dev, "Device match requests probe deferral\n");
 746                 driver_deferred_probe_add(dev);
 747         } else if (ret < 0) {
 748                 dev_dbg(dev, "Bus failed to match device: %d", ret);
 749                 return ret;
 750         } /* ret > 0 means positive match */
 751
 752         if (dev->parent)        /* Needed for USB */
 753                 device_lock(dev->parent);
 754         device_lock(dev);
 755         if (!dev->driver)
 756                 driver_probe_device(drv, dev);
 757         device_unlock(dev);
 758         if (dev->parent)
 759                 device_unlock(dev->parent);
 760
 761         return 0;
 762 }
 763
 764 /**
 765  * driver_attach - try to bind driver to devices.
 766  * @drv: driver.
 767  *
 768  * Walk the list of devices that the bus has on it and try to
 769  * match the driver with each one.  If driver_probe_device()
 770  * returns 0 and the @dev->driver is set, we've found a
 771  * compatible pair.
 772  */
 773 int driver_attach(struct device_driver *drv)
 774 {
 775         return bus_for_each_dev(drv->bus, NULL, drv, __driver_attach);
 776 }
 777 EXPORT_SYMBOL_GPL(driver_attach);
 778
 779 /*
 780  * __device_release_driver() must be called with @dev lock held.
 781  * When called for a USB interface, @dev->parent lock must be held as well.
 782  */
 783 static void __device_release_driver(struct device *dev, struct device *parent)
 784 {
 785         struct device_driver *drv;
 786
 787         drv = dev->driver;
 788         if (drv) {
 789                 if (driver_allows_async_probing(drv))
 790                         async_synchronize_full();
 791
 792                 while (device_links_busy(dev)) {
 793                         device_unlock(dev);
 794                         if (parent)
 795                                 device_unlock(parent);
 796
 797                         device_links_unbind_consumers(dev);
 798                         if (parent)
 799                                 device_lock(parent);
 800
 801                         device_lock(dev);
 802                         /*
 803                          * A concurrent invocation of the same function might
 804                          * have released the driver successfully while this one
 805                          * was waiting, so check for that.
 806                          */
 807                         if (dev->driver != drv)
 808                                 return;
 809                 }
 810
 811                 pm_runtime_get_sync(dev);
 812                 pm_runtime_clean_up_links(dev);
 813
 814                 driver_sysfs_remove(dev);
 815
 816                 if (dev->bus)
 817                         blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 818                                                      BUS_NOTIFY_UNBIND_DRIVER,
 819                                                      dev);
 820
 821                 pm_runtime_put_sync(dev);
 822
 823                 if (dev->bus && dev->bus->remove)
 824                         dev->bus->remove(dev);
 825                 else if (drv->remove)
 826                         drv->remove(dev);
 827
 828                 device_links_driver_cleanup(dev);
 829                 devres_release_all(dev);
 830                 dev->driver = NULL;
 831                 dev_set_drvdata(dev, NULL);
 832                 if (dev->pm_domain && dev->pm_domain->dismiss)
 833                         dev->pm_domain->dismiss(dev);
 834                 pm_runtime_reinit(dev);
 835
 836                 klist_remove(&dev->p->knode_driver);
 837                 device_pm_check_callbacks(dev);
 838                 if (dev->bus)
 839                         blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 840                                                      BUS_NOTIFY_UNBOUND_DRIVER,
 841                                                      dev);
 842         }
 843 }
 844
 845 void device_release_driver_internal(struct device *dev,
 846                                     struct device_driver *drv,
 847                                     struct device *parent)
 848 {
 849         if (parent)
 850                 device_lock(parent);
 851
 852         device_lock(dev);
 853         if (!drv || drv == dev->driver)
 854                 __device_release_driver(dev, parent);
 855
 856         device_unlock(dev);
 857         if (parent)
 858                 device_unlock(parent);
 859 }
 860
 861 /**
 862  * device_release_driver - manually detach device from driver.
 863  * @dev: device.
 864  *
 865  * Manually detach device from driver.
 866  * When called for a USB interface, @dev->parent lock must be held.
 867  *
 868  * If this function is to be called with @dev->parent lock held, ensure that
 869  * the device's consumers are unbound in advance or that their locks can be
 870  * acquired under the @dev->parent lock.
 871  */
 872 void device_release_driver(struct device *dev)
 873 {
 874         /*
 875          * If anyone calls device_release_driver() recursively from
 876          * within their ->remove callback for the same device, they
 877          * will deadlock right here.
 878          */
 879         device_release_driver_internal(dev, NULL, NULL);
 880 }
 881 EXPORT_SYMBOL_GPL(device_release_driver);
 882
 883 /**
 884  * driver_detach - detach driver from all devices it controls.
 885  * @drv: driver.
 886  */
 887 void driver_detach(struct device_driver *drv)
 888 {
 889         struct device_private *dev_prv;
 890         struct device *dev;
 891
 892         for (;;) {
 893                 spin_lock(&drv->p->klist_devices.k_lock);
 894                 if (list_empty(&drv->p->klist_devices.k_list)) {
 895                         spin_unlock(&drv->p->klist_devices.k_lock);
 896                         break;
 897                 }
 898                 dev_prv = list_entry(drv->p->klist_devices.k_list.prev,
 899                                      struct device_private,
 900                                      knode_driver.n_node);
 901                 dev = dev_prv->device;
 902                 get_device(dev);
 903                 spin_unlock(&drv->p->klist_devices.k_lock);
 904                 device_release_driver_internal(dev, drv, dev->parent);
 905                 put_device(dev);
 906         }
 907 }