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/dma-mapping.h>
  23 #include <linux/init.h>
  24 #include <linux/module.h>
  25 #include <linux/kthread.h>
  26 #include <linux/wait.h>
  27 #include <linux/async.h>
  28 #include <linux/pm_runtime.h>
  29 #include <linux/pinctrl/devinfo.h>
  30
  31 #include "base.h"
  32 #include "power/power.h"
  33
  34 /*
  35  * Deferred Probe infrastructure.
  36  *
  37  * Sometimes driver probe order matters, but the kernel doesn't always have
  38  * dependency information which means some drivers will get probed before a
  39  * resource it depends on is available.  For example, an SDHCI driver may
  40  * first need a GPIO line from an i2c GPIO controller before it can be
  41  * initialized.  If a required resource is not available yet, a driver can
  42  * request probing to be deferred by returning -EPROBE_DEFER from its probe hook
  43  *
  44  * Deferred probe maintains two lists of devices, a pending list and an active
  45  * list.  A driver returning -EPROBE_DEFER causes the device to be added to the
  46  * pending list.  A successful driver probe will trigger moving all devices
  47  * from the pending to the active list so that the workqueue will eventually
  48  * retry them.
  49  *
  50  * The deferred_probe_mutex must be held any time the deferred_probe_*_list
  51  * of the (struct device*)->p->deferred_probe pointers are manipulated
  52  */
  53 static DEFINE_MUTEX(deferred_probe_mutex);
  54 static LIST_HEAD(deferred_probe_pending_list);
  55 static LIST_HEAD(deferred_probe_active_list);
  56 static atomic_t deferred_trigger_count = ATOMIC_INIT(0);
  57 static bool initcalls_done;
  58
  59 /*
  60  * In some cases, like suspend to RAM or hibernation, It might be reasonable
  61  * to prohibit probing of devices as it could be unsafe.
  62  * Once defer_all_probes is true all drivers probes will be forcibly deferred.
  63  */
  64 static bool defer_all_probes;
  65
  66 /*
  67  * For initcall_debug, show the deferred probes executed in late_initcall
  68  * processing.
  69  */
  70 static void deferred_probe_debug(struct device *dev)
  71 {
  72         ktime_t calltime, delta, rettime;
  73         unsigned long long duration;
  74
  75         printk(KERN_DEBUG "deferred probe %s @ %i\n", dev_name(dev),
  76                task_pid_nr(current));
  77         calltime = ktime_get();
  78         bus_probe_device(dev);
  79         rettime = ktime_get();
  80         delta = ktime_sub(rettime, calltime);
  81         duration = (unsigned long long) ktime_to_ns(delta) >> 10;
  82         printk(KERN_DEBUG "deferred probe %s returned after %lld usecs\n",
  83                dev_name(dev), duration);
  84 }
  85
  86 /*
  87  * deferred_probe_work_func() - Retry probing devices in the active list.
  88  */
  89 static void deferred_probe_work_func(struct work_struct *work)
  90 {
  91         struct device *dev;
  92         struct device_private *private;
  93         /*
  94          * This block processes every device in the deferred 'active' list.
  95          * Each device is removed from the active list and passed to
  96          * bus_probe_device() to re-attempt the probe.  The loop continues
  97          * until every device in the active list is removed and retried.
  98          *
  99          * Note: Once the device is removed from the list and the mutex is
 100          * released, it is possible for the device get freed by another thread
 101          * and cause a illegal pointer dereference.  This code uses
 102          * get/put_device() to ensure the device structure cannot disappear
 103          * from under our feet.
 104          */
 105         mutex_lock(&deferred_probe_mutex);
 106         while (!list_empty(&deferred_probe_active_list)) {
 107                 private = list_first_entry(&deferred_probe_active_list,
 108                                         typeof(*dev->p), deferred_probe);
 109                 dev = private->device;
 110                 list_del_init(&private->deferred_probe);
 111
 112                 get_device(dev);
 113
 114                 /*
 115                  * Drop the mutex while probing each device; the probe path may
 116                  * manipulate the deferred list
 117                  */
 118                 mutex_unlock(&deferred_probe_mutex);
 119
 120                 /*
 121                  * Force the device to the end of the dpm_list since
 122                  * the PM code assumes that the order we add things to
 123                  * the list is a good order for suspend but deferred
 124                  * probe makes that very unsafe.
 125                  */
 126                 device_pm_lock();
 127                 device_pm_move_last(dev);
 128                 device_pm_unlock();
 129
 130                 dev_dbg(dev, "Retrying from deferred list\n");
 131                 if (initcall_debug && !initcalls_done)
 132                         deferred_probe_debug(dev);
 133                 else
 134                         bus_probe_device(dev);
 135
 136                 mutex_lock(&deferred_probe_mutex);
 137
 138                 put_device(dev);
 139         }
 140         mutex_unlock(&deferred_probe_mutex);
 141 }
 142 static DECLARE_WORK(deferred_probe_work, deferred_probe_work_func);
 143
 144 static void driver_deferred_probe_add(struct device *dev)
 145 {
 146         mutex_lock(&deferred_probe_mutex);
 147         if (list_empty(&dev->p->deferred_probe)) {
 148                 dev_dbg(dev, "Added to deferred list\n");
 149                 list_add_tail(&dev->p->deferred_probe, &deferred_probe_pending_list);
 150         }
 151         mutex_unlock(&deferred_probe_mutex);
 152 }
 153
 154 void driver_deferred_probe_del(struct device *dev)
 155 {
 156         mutex_lock(&deferred_probe_mutex);
 157         if (!list_empty(&dev->p->deferred_probe)) {
 158                 dev_dbg(dev, "Removed from deferred list\n");
 159                 list_del_init(&dev->p->deferred_probe);
 160         }
 161         mutex_unlock(&deferred_probe_mutex);
 162 }
 163
 164 static bool driver_deferred_probe_enable = false;
 165 /**
 166  * driver_deferred_probe_trigger() - Kick off re-probing deferred devices
 167  *
 168  * This functions moves all devices from the pending list to the active
 169  * list and schedules the deferred probe workqueue to process them.  It
 170  * should be called anytime a driver is successfully bound to a device.
 171  *
 172  * Note, there is a race condition in multi-threaded probe. In the case where
 173  * more than one device is probing at the same time, it is possible for one
 174  * probe to complete successfully while another is about to defer. If the second
 175  * depends on the first, then it will get put on the pending list after the
 176  * trigger event has already occurred and will be stuck there.
 177  *
 178  * The atomic 'deferred_trigger_count' is used to determine if a successful
 179  * trigger has occurred in the midst of probing a driver. If the trigger count
 180  * changes in the midst of a probe, then deferred processing should be triggered
 181  * again.
 182  */
 183 void driver_deferred_probe_trigger(void)
 184 {
 185         if (!driver_deferred_probe_enable)
 186                 return;
 187
 188         /*
 189          * A successful probe means that all the devices in the pending list
 190          * should be triggered to be reprobed.  Move all the deferred devices
 191          * into the active list so they can be retried by the workqueue
 192          */
 193         mutex_lock(&deferred_probe_mutex);
 194         atomic_inc(&deferred_trigger_count);
 195         list_splice_tail_init(&deferred_probe_pending_list,
 196                               &deferred_probe_active_list);
 197         mutex_unlock(&deferred_probe_mutex);
 198
 199         /*
 200          * Kick the re-probe thread.  It may already be scheduled, but it is
 201          * safe to kick it again.
 202          */
 203         schedule_work(&deferred_probe_work);
 204 }
 205
 206 /**
 207  * device_block_probing() - Block/defere device's probes
 208  *
 209  *      It will disable probing of devices and defer their probes instead.
 210  */
 211 void device_block_probing(void)
 212 {
 213         defer_all_probes = true;
 214         /* sync with probes to avoid races. */
 215         wait_for_device_probe();
 216 }
 217
 218 /**
 219  * device_unblock_probing() - Unblock/enable device's probes
 220  *
 221  *      It will restore normal behavior and trigger re-probing of deferred
 222  * devices.
 223  */
 224 void device_unblock_probing(void)
 225 {
 226         defer_all_probes = false;
 227         driver_deferred_probe_trigger();
 228 }
 229
 230 /**
 231  * deferred_probe_initcall() - Enable probing of deferred devices
 232  *
 233  * We don't want to get in the way when the bulk of drivers are getting probed.
 234  * Instead, this initcall makes sure that deferred probing is delayed until
 235  * late_initcall time.
 236  */
 237 static int deferred_probe_initcall(void)
 238 {
 239         driver_deferred_probe_enable = true;
 240         driver_deferred_probe_trigger();
 241         /* Sort as many dependencies as possible before exiting initcalls */
 242         flush_work(&deferred_probe_work);
 243         initcalls_done = true;
 244         return 0;
 245 }
 246 late_initcall(deferred_probe_initcall);
 247
 248 /**
 249  * device_is_bound() - Check if device is bound to a driver
 250  * @dev: device to check
 251  *
 252  * Returns true if passed device has already finished probing successfully
 253  * against a driver.
 254  *
 255  * This function must be called with the device lock held.
 256  */
 257 bool device_is_bound(struct device *dev)
 258 {
 259         return dev->p && klist_node_attached(&dev->p->knode_driver);
 260 }
 261
 262 static void driver_bound(struct device *dev)
 263 {
 264         if (device_is_bound(dev)) {
 265                 printk(KERN_WARNING "%s: device %s already bound\n",
 266                         __func__, kobject_name(&dev->kobj));
 267                 return;
 268         }
 269
 270         pr_debug("driver: '%s': %s: bound to device '%s'\n", dev->driver->name,
 271                  __func__, dev_name(dev));
 272
 273         klist_add_tail(&dev->p->knode_driver, &dev->driver->p->klist_devices);
 274         device_links_driver_bound(dev);
 275
 276         device_pm_check_callbacks(dev);
 277
 278         /*
 279          * Make sure the device is no longer in one of the deferred lists and
 280          * kick off retrying all pending devices
 281          */
 282         driver_deferred_probe_del(dev);
 283         driver_deferred_probe_trigger();
 284
 285         if (dev->bus)
 286                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 287                                              BUS_NOTIFY_BOUND_DRIVER, dev);
 288
 289         kobject_uevent(&dev->kobj, KOBJ_BIND);
 290 }
 291
 292 static int driver_sysfs_add(struct device *dev)
 293 {
 294         int ret;
 295
 296         if (dev->bus)
 297                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 298                                              BUS_NOTIFY_BIND_DRIVER, dev);
 299
 300         ret = sysfs_create_link(&dev->driver->p->kobj, &dev->kobj,
 301                           kobject_name(&dev->kobj));
 302         if (ret == 0) {
 303                 ret = sysfs_create_link(&dev->kobj, &dev->driver->p->kobj,
 304                                         "driver");
 305                 if (ret)
 306                         sysfs_remove_link(&dev->driver->p->kobj,
 307                                         kobject_name(&dev->kobj));
 308         }
 309         return ret;
 310 }
 311
 312 static void driver_sysfs_remove(struct device *dev)
 313 {
 314         struct device_driver *drv = dev->driver;
 315
 316         if (drv) {
 317                 sysfs_remove_link(&drv->p->kobj, kobject_name(&dev->kobj));
 318                 sysfs_remove_link(&dev->kobj, "driver");
 319         }
 320 }
 321
 322 /**
 323  * device_bind_driver - bind a driver to one device.
 324  * @dev: device.
 325  *
 326  * Allow manual attachment of a driver to a device.
 327  * Caller must have already set @dev->driver.
 328  *
 329  * Note that this does not modify the bus reference count
 330  * nor take the bus's rwsem. Please verify those are accounted
 331  * for before calling this. (It is ok to call with no other effort
 332  * from a driver's probe() method.)
 333  *
 334  * This function must be called with the device lock held.
 335  */
 336 int device_bind_driver(struct device *dev)
 337 {
 338         int ret;
 339
 340         ret = driver_sysfs_add(dev);
 341         if (!ret)
 342                 driver_bound(dev);
 343         else if (dev->bus)
 344                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 345                                              BUS_NOTIFY_DRIVER_NOT_BOUND, dev);
 346         return ret;
 347 }
 348 EXPORT_SYMBOL_GPL(device_bind_driver);
 349
 350 static atomic_t probe_count = ATOMIC_INIT(0);
 351 static DECLARE_WAIT_QUEUE_HEAD(probe_waitqueue);
 352
 353 static int really_probe(struct device *dev, struct device_driver *drv)
 354 {
 355         int ret = -EPROBE_DEFER;
 356         int local_trigger_count = atomic_read(&deferred_trigger_count);
 357         bool test_remove = IS_ENABLED(CONFIG_DEBUG_TEST_DRIVER_REMOVE) &&
 358                            !drv->suppress_bind_attrs;
 359
 360         if (defer_all_probes) {
 361                 /*
 362                  * Value of defer_all_probes can be set only by
 363                  * device_defer_all_probes_enable() which, in turn, will call
 364                  * wait_for_device_probe() right after that to avoid any races.
 365                  */
 366                 dev_dbg(dev, "Driver %s force probe deferral\n", drv->name);
 367                 driver_deferred_probe_add(dev);
 368                 return ret;
 369         }
 370
 371         ret = device_links_check_suppliers(dev);
 372         if (ret)
 373                 return ret;
 374
 375         atomic_inc(&probe_count);
 376         pr_debug("bus: '%s': %s: probing driver %s with device %s\n",
 377                  drv->bus->name, __func__, drv->name, dev_name(dev));
 378         WARN_ON(!list_empty(&dev->devres_head));
 379
 380 re_probe:
 381         dev->driver = drv;
 382
 383         /* If using pinctrl, bind pins now before probing */
 384         ret = pinctrl_bind_pins(dev);
 385         if (ret)
 386                 goto pinctrl_bind_failed;
 387
 388         ret = dma_configure(dev);
 389         if (ret)
 390                 goto dma_failed;
 391
 392         if (driver_sysfs_add(dev)) {
 393                 printk(KERN_ERR "%s: driver_sysfs_add(%s) failed\n",
 394                         __func__, dev_name(dev));
 395                 goto probe_failed;
 396         }
 397
 398         if (dev->pm_domain && dev->pm_domain->activate) {
 399                 ret = dev->pm_domain->activate(dev);
 400                 if (ret)
 401                         goto probe_failed;
 402         }
 403
 404         if (dev->bus->probe) {
 405                 ret = dev->bus->probe(dev);
 406                 if (ret)
 407                         goto probe_failed;
 408         } else if (drv->probe) {
 409                 ret = drv->probe(dev);
 410                 if (ret)
 411                         goto probe_failed;
 412         }
 413
 414         if (test_remove) {
 415                 test_remove = false;
 416
 417                 if (dev->bus->remove)
 418                         dev->bus->remove(dev);
 419                 else if (drv->remove)
 420                         drv->remove(dev);
 421
 422                 devres_release_all(dev);
 423                 driver_sysfs_remove(dev);
 424                 dev->driver = NULL;
 425                 dev_set_drvdata(dev, NULL);
 426                 if (dev->pm_domain && dev->pm_domain->dismiss)
 427                         dev->pm_domain->dismiss(dev);
 428                 pm_runtime_reinit(dev);
 429
 430                 goto re_probe;
 431         }
 432
 433         pinctrl_init_done(dev);
 434
 435         if (dev->pm_domain && dev->pm_domain->sync)
 436                 dev->pm_domain->sync(dev);
 437
 438         driver_bound(dev);
 439         ret = 1;
 440         pr_debug("bus: '%s': %s: bound device %s to driver %s\n",
 441                  drv->bus->name, __func__, dev_name(dev), drv->name);
 442         goto done;
 443
 444 probe_failed:
 445         dma_deconfigure(dev);
 446 dma_failed:
 447         if (dev->bus)
 448                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 449                                              BUS_NOTIFY_DRIVER_NOT_BOUND, dev);
 450 pinctrl_bind_failed:
 451         device_links_no_driver(dev);
 452         devres_release_all(dev);
 453         driver_sysfs_remove(dev);
 454         dev->driver = NULL;
 455         dev_set_drvdata(dev, NULL);
 456         if (dev->pm_domain && dev->pm_domain->dismiss)
 457                 dev->pm_domain->dismiss(dev);
 458         pm_runtime_reinit(dev);
 459
 460         switch (ret) {
 461         case -EPROBE_DEFER:
 462                 /* Driver requested deferred probing */
 463                 dev_dbg(dev, "Driver %s requests probe deferral\n", drv->name);
 464                 driver_deferred_probe_add(dev);
 465                 /* Did a trigger occur while probing? Need to re-trigger if yes */
 466                 if (local_trigger_count != atomic_read(&deferred_trigger_count))
 467                         driver_deferred_probe_trigger();
 468                 break;
 469         case -ENODEV:
 470         case -ENXIO:
 471                 pr_debug("%s: probe of %s rejects match %d\n",
 472                          drv->name, dev_name(dev), ret);
 473                 break;
 474         default:
 475                 /* driver matched but the probe failed */
 476                 printk(KERN_WARNING
 477                        "%s: probe of %s failed with error %d\n",
 478                        drv->name, dev_name(dev), ret);
 479         }
 480         /*
 481          * Ignore errors returned by ->probe so that the next driver can try
 482          * its luck.
 483          */
 484         ret = 0;
 485 done:
 486         atomic_dec(&probe_count);
 487         wake_up(&probe_waitqueue);
 488         return ret;
 489 }
 490
 491 /**
 492  * driver_probe_done
 493  * Determine if the probe sequence is finished or not.
 494  *
 495  * Should somehow figure out how to use a semaphore, not an atomic variable...
 496  */
 497 int driver_probe_done(void)
 498 {
 499         pr_debug("%s: probe_count = %d\n", __func__,
 500                  atomic_read(&probe_count));
 501         if (atomic_read(&probe_count))
 502                 return -EBUSY;
 503         return 0;
 504 }
 505
 506 /**
 507  * wait_for_device_probe
 508  * Wait for device probing to be completed.
 509  */
 510 void wait_for_device_probe(void)
 511 {
 512         /* wait for the deferred probe workqueue to finish */
 513         flush_work(&deferred_probe_work);
 514
 515         /* wait for the known devices to complete their probing */
 516         wait_event(probe_waitqueue, atomic_read(&probe_count) == 0);
 517         async_synchronize_full();
 518 }
 519 EXPORT_SYMBOL_GPL(wait_for_device_probe);
 520
 521 /**
 522  * driver_probe_device - attempt to bind device & driver together
 523  * @drv: driver to bind a device to
 524  * @dev: device to try to bind to the driver
 525  *
 526  * This function returns -ENODEV if the device is not registered,
 527  * 1 if the device is bound successfully and 0 otherwise.
 528  *
 529  * This function must be called with @dev lock held.  When called for a
 530  * USB interface, @dev->parent lock must be held as well.
 531  *
 532  * If the device has a parent, runtime-resume the parent before driver probing.
 533  */
 534 int driver_probe_device(struct device_driver *drv, struct device *dev)
 535 {
 536         int ret = 0;
 537
 538         if (!device_is_registered(dev))
 539                 return -ENODEV;
 540
 541         pr_debug("bus: '%s': %s: matched device %s with driver %s\n",
 542                  drv->bus->name, __func__, dev_name(dev), drv->name);
 543
 544         pm_runtime_get_suppliers(dev);
 545         if (dev->parent)
 546                 pm_runtime_get_sync(dev->parent);
 547
 548         pm_runtime_barrier(dev);
 549         ret = really_probe(dev, drv);
 550         pm_request_idle(dev);
 551
 552         if (dev->parent)
 553                 pm_runtime_put(dev->parent);
 554
 555         pm_runtime_put_suppliers(dev);
 556         return ret;
 557 }
 558
 559 bool driver_allows_async_probing(struct device_driver *drv)
 560 {
 561         switch (drv->probe_type) {
 562         case PROBE_PREFER_ASYNCHRONOUS:
 563                 return true;
 564
 565         case PROBE_FORCE_SYNCHRONOUS:
 566                 return false;
 567
 568         default:
 569                 if (module_requested_async_probing(drv->owner))
 570                         return true;
 571
 572                 return false;
 573         }
 574 }
 575
 576 struct device_attach_data {
 577         struct device *dev;
 578
 579         /*
 580          * Indicates whether we are are considering asynchronous probing or
 581          * not. Only initial binding after device or driver registration
 582          * (including deferral processing) may be done asynchronously, the
 583          * rest is always synchronous, as we expect it is being done by
 584          * request from userspace.
 585          */
 586         bool check_async;
 587
 588         /*
 589          * Indicates if we are binding synchronous or asynchronous drivers.
 590          * When asynchronous probing is enabled we'll execute 2 passes
 591          * over drivers: first pass doing synchronous probing and second
 592          * doing asynchronous probing (if synchronous did not succeed -
 593          * most likely because there was no driver requiring synchronous
 594          * probing - and we found asynchronous driver during first pass).
 595          * The 2 passes are done because we can't shoot asynchronous
 596          * probe for given device and driver from bus_for_each_drv() since
 597          * driver pointer is not guaranteed to stay valid once
 598          * bus_for_each_drv() iterates to the next driver on the bus.
 599          */
 600         bool want_async;
 601
 602         /*
 603          * We'll set have_async to 'true' if, while scanning for matching
 604          * driver, we'll encounter one that requests asynchronous probing.
 605          */
 606         bool have_async;
 607 };
 608
 609 static int __device_attach_driver(struct device_driver *drv, void *_data)
 610 {
 611         struct device_attach_data *data = _data;
 612         struct device *dev = data->dev;
 613         bool async_allowed;
 614         int ret;
 615
 616         /*
 617          * Check if device has already been claimed. This may
 618          * happen with driver loading, device discovery/registration,
 619          * and deferred probe processing happens all at once with
 620          * multiple threads.
 621          */
 622         if (dev->driver)
 623                 return -EBUSY;
 624
 625         ret = driver_match_device(drv, dev);
 626         if (ret == 0) {
 627                 /* no match */
 628                 return 0;
 629         } else if (ret == -EPROBE_DEFER) {
 630                 dev_dbg(dev, "Device match requests probe deferral\n");
 631                 driver_deferred_probe_add(dev);
 632         } else if (ret < 0) {
 633                 dev_dbg(dev, "Bus failed to match device: %d", ret);
 634                 return ret;
 635         } /* ret > 0 means positive match */
 636
 637         async_allowed = driver_allows_async_probing(drv);
 638
 639         if (async_allowed)
 640                 data->have_async = true;
 641
 642         if (data->check_async && async_allowed != data->want_async)
 643                 return 0;
 644
 645         return driver_probe_device(drv, dev);
 646 }
 647
 648 static void __device_attach_async_helper(void *_dev, async_cookie_t cookie)
 649 {
 650         struct device *dev = _dev;
 651         struct device_attach_data data = {
 652                 .dev            = dev,
 653                 .check_async    = true,
 654                 .want_async     = true,
 655         };
 656
 657         device_lock(dev);
 658
 659         if (dev->parent)
 660                 pm_runtime_get_sync(dev->parent);
 661
 662         bus_for_each_drv(dev->bus, NULL, &data, __device_attach_driver);
 663         dev_dbg(dev, "async probe completed\n");
 664
 665         pm_request_idle(dev);
 666
 667         if (dev->parent)
 668                 pm_runtime_put(dev->parent);
 669
 670         device_unlock(dev);
 671
 672         put_device(dev);
 673 }
 674
 675 static int __device_attach(struct device *dev, bool allow_async)
 676 {
 677         int ret = 0;
 678
 679         device_lock(dev);
 680         if (dev->driver) {
 681                 if (device_is_bound(dev)) {
 682                         ret = 1;
 683                         goto out_unlock;
 684                 }
 685                 ret = device_bind_driver(dev);
 686                 if (ret == 0)
 687                         ret = 1;
 688                 else {
 689                         dev->driver = NULL;
 690                         ret = 0;
 691                 }
 692         } else {
 693                 struct device_attach_data data = {
 694                         .dev = dev,
 695                         .check_async = allow_async,
 696                         .want_async = false,
 697                 };
 698
 699                 if (dev->parent)
 700                         pm_runtime_get_sync(dev->parent);
 701
 702                 ret = bus_for_each_drv(dev->bus, NULL, &data,
 703                                         __device_attach_driver);
 704                 if (!ret && allow_async && data.have_async) {
 705                         /*
 706                          * If we could not find appropriate driver
 707                          * synchronously and we are allowed to do
 708                          * async probes and there are drivers that
 709                          * want to probe asynchronously, we'll
 710                          * try them.
 711                          */
 712                         dev_dbg(dev, "scheduling asynchronous probe\n");
 713                         get_device(dev);
 714                         async_schedule(__device_attach_async_helper, dev);
 715                 } else {
 716                         pm_request_idle(dev);
 717                 }
 718
 719                 if (dev->parent)
 720                         pm_runtime_put(dev->parent);
 721         }
 722 out_unlock:
 723         device_unlock(dev);
 724         return ret;
 725 }
 726
 727 /**
 728  * device_attach - try to attach device to a driver.
 729  * @dev: device.
 730  *
 731  * Walk the list of drivers that the bus has and call
 732  * driver_probe_device() for each pair. If a compatible
 733  * pair is found, break out and return.
 734  *
 735  * Returns 1 if the device was bound to a driver;
 736  * 0 if no matching driver was found;
 737  * -ENODEV if the device is not registered.
 738  *
 739  * When called for a USB interface, @dev->parent lock must be held.
 740  */
 741 int device_attach(struct device *dev)
 742 {
 743         return __device_attach(dev, false);
 744 }
 745 EXPORT_SYMBOL_GPL(device_attach);
 746
 747 void device_initial_probe(struct device *dev)
 748 {
 749         __device_attach(dev, true);
 750 }
 751
 752 static int __driver_attach(struct device *dev, void *data)
 753 {
 754         struct device_driver *drv = data;
 755         int ret;
 756
 757         /*
 758          * Lock device and try to bind to it. We drop the error
 759          * here and always return 0, because we need to keep trying
 760          * to bind to devices and some drivers will return an error
 761          * simply if it didn't support the device.
 762          *
 763          * driver_probe_device() will spit a warning if there
 764          * is an error.
 765          */
 766
 767         ret = driver_match_device(drv, dev);
 768         if (ret == 0) {
 769                 /* no match */
 770                 return 0;
 771         } else if (ret == -EPROBE_DEFER) {
 772                 dev_dbg(dev, "Device match requests probe deferral\n");
 773                 driver_deferred_probe_add(dev);
 774         } else if (ret < 0) {
 775                 dev_dbg(dev, "Bus failed to match device: %d", ret);
 776                 return ret;
 777         } /* ret > 0 means positive match */
 778
 779         if (dev->parent)        /* Needed for USB */
 780                 device_lock(dev->parent);
 781         device_lock(dev);
 782         if (!dev->driver)
 783                 driver_probe_device(drv, dev);
 784         device_unlock(dev);
 785         if (dev->parent)
 786                 device_unlock(dev->parent);
 787
 788         return 0;
 789 }
 790
 791 /**
 792  * driver_attach - try to bind driver to devices.
 793  * @drv: driver.
 794  *
 795  * Walk the list of devices that the bus has on it and try to
 796  * match the driver with each one.  If driver_probe_device()
 797  * returns 0 and the @dev->driver is set, we've found a
 798  * compatible pair.
 799  */
 800 int driver_attach(struct device_driver *drv)
 801 {
 802         return bus_for_each_dev(drv->bus, NULL, drv, __driver_attach);
 803 }
 804 EXPORT_SYMBOL_GPL(driver_attach);
 805
 806 /*
 807  * __device_release_driver() must be called with @dev lock held.
 808  * When called for a USB interface, @dev->parent lock must be held as well.
 809  */
 810 static void __device_release_driver(struct device *dev, struct device *parent)
 811 {
 812         struct device_driver *drv;
 813
 814         drv = dev->driver;
 815         if (drv) {
 816                 while (device_links_busy(dev)) {
 817                         device_unlock(dev);
 818                         if (parent)
 819                                 device_unlock(parent);
 820
 821                         device_links_unbind_consumers(dev);
 822                         if (parent)
 823                                 device_lock(parent);
 824
 825                         device_lock(dev);
 826                         /*
 827                          * A concurrent invocation of the same function might
 828                          * have released the driver successfully while this one
 829                          * was waiting, so check for that.
 830                          */
 831                         if (dev->driver != drv)
 832                                 return;
 833                 }
 834
 835                 pm_runtime_get_sync(dev);
 836                 pm_runtime_clean_up_links(dev);
 837
 838                 driver_sysfs_remove(dev);
 839
 840                 if (dev->bus)
 841                         blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 842                                                      BUS_NOTIFY_UNBIND_DRIVER,
 843                                                      dev);
 844
 845                 pm_runtime_put_sync(dev);
 846
 847                 if (dev->bus && dev->bus->remove)
 848                         dev->bus->remove(dev);
 849                 else if (drv->remove)
 850                         drv->remove(dev);
 851
 852                 device_links_driver_cleanup(dev);
 853                 dma_deconfigure(dev);
 854
 855                 devres_release_all(dev);
 856                 dev->driver = NULL;
 857                 dev_set_drvdata(dev, NULL);
 858                 if (dev->pm_domain && dev->pm_domain->dismiss)
 859                         dev->pm_domain->dismiss(dev);
 860                 pm_runtime_reinit(dev);
 861
 862                 klist_remove(&dev->p->knode_driver);
 863                 device_pm_check_callbacks(dev);
 864                 if (dev->bus)
 865                         blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 866                                                      BUS_NOTIFY_UNBOUND_DRIVER,
 867                                                      dev);
 868
 869                 kobject_uevent(&dev->kobj, KOBJ_UNBIND);
 870         }
 871 }
 872
 873 void device_release_driver_internal(struct device *dev,
 874                                     struct device_driver *drv,
 875                                     struct device *parent)
 876 {
 877         if (parent)
 878                 device_lock(parent);
 879
 880         device_lock(dev);
 881         if (!drv || drv == dev->driver)
 882                 __device_release_driver(dev, parent);
 883
 884         device_unlock(dev);
 885         if (parent)
 886                 device_unlock(parent);
 887 }
 888
 889 /**
 890  * device_release_driver - manually detach device from driver.
 891  * @dev: device.
 892  *
 893  * Manually detach device from driver.
 894  * When called for a USB interface, @dev->parent lock must be held.
 895  *
 896  * If this function is to be called with @dev->parent lock held, ensure that
 897  * the device's consumers are unbound in advance or that their locks can be
 898  * acquired under the @dev->parent lock.
 899  */
 900 void device_release_driver(struct device *dev)
 901 {
 902         /*
 903          * If anyone calls device_release_driver() recursively from
 904          * within their ->remove callback for the same device, they
 905          * will deadlock right here.
 906          */
 907         device_release_driver_internal(dev, NULL, NULL);
 908 }
 909 EXPORT_SYMBOL_GPL(device_release_driver);
 910
 911 /**
 912  * driver_detach - detach driver from all devices it controls.
 913  * @drv: driver.
 914  */
 915 void driver_detach(struct device_driver *drv)
 916 {
 917         struct device_private *dev_prv;
 918         struct device *dev;
 919
 920         if (driver_allows_async_probing(drv))
 921                 async_synchronize_full();
 922
 923         for (;;) {
 924                 spin_lock(&drv->p->klist_devices.k_lock);
 925                 if (list_empty(&drv->p->klist_devices.k_list)) {
 926                         spin_unlock(&drv->p->klist_devices.k_lock);
 927                         break;
 928                 }
 929                 dev_prv = list_entry(drv->p->klist_devices.k_list.prev,
 930                                      struct device_private,
 931                                      knode_driver.n_node);
 932                 dev = dev_prv->device;
 933                 get_device(dev);
 934                 spin_unlock(&drv->p->klist_devices.k_lock);
 935                 device_release_driver_internal(dev, drv, dev->parent);
 936                 put_device(dev);
 937         }
 938 }