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 static 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         if (!list_empty(&dev->devres_head)) {
 379                 dev_crit(dev, "Resources present before probing\n");
 380                 ret = -EBUSY;
 381                 goto done;
 382         }
 383
 384 re_probe:
 385         dev->driver = drv;
 386
 387         /* If using pinctrl, bind pins now before probing */
 388         ret = pinctrl_bind_pins(dev);
 389         if (ret)
 390                 goto pinctrl_bind_failed;
 391
 392         ret = dma_configure(dev);
 393         if (ret)
 394                 goto probe_failed;
 395
 396         if (driver_sysfs_add(dev)) {
 397                 printk(KERN_ERR "%s: driver_sysfs_add(%s) failed\n",
 398                         __func__, dev_name(dev));
 399                 goto probe_failed;
 400         }
 401
 402         if (dev->pm_domain && dev->pm_domain->activate) {
 403                 ret = dev->pm_domain->activate(dev);
 404                 if (ret)
 405                         goto probe_failed;
 406         }
 407
 408         if (dev->bus->probe) {
 409                 ret = dev->bus->probe(dev);
 410                 if (ret)
 411                         goto probe_failed;
 412         } else if (drv->probe) {
 413                 ret = drv->probe(dev);
 414                 if (ret)
 415                         goto probe_failed;
 416         }
 417
 418         if (test_remove) {
 419                 test_remove = false;
 420
 421                 if (dev->bus->remove)
 422                         dev->bus->remove(dev);
 423                 else if (drv->remove)
 424                         drv->remove(dev);
 425
 426                 devres_release_all(dev);
 427                 driver_sysfs_remove(dev);
 428                 dev->driver = NULL;
 429                 dev_set_drvdata(dev, NULL);
 430                 if (dev->pm_domain && dev->pm_domain->dismiss)
 431                         dev->pm_domain->dismiss(dev);
 432                 pm_runtime_reinit(dev);
 433
 434                 goto re_probe;
 435         }
 436
 437         pinctrl_init_done(dev);
 438
 439         if (dev->pm_domain && dev->pm_domain->sync)
 440                 dev->pm_domain->sync(dev);
 441
 442         driver_bound(dev);
 443         ret = 1;
 444         pr_debug("bus: '%s': %s: bound device %s to driver %s\n",
 445                  drv->bus->name, __func__, dev_name(dev), drv->name);
 446         goto done;
 447
 448 probe_failed:
 449         if (dev->bus)
 450                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 451                                              BUS_NOTIFY_DRIVER_NOT_BOUND, dev);
 452 pinctrl_bind_failed:
 453         device_links_no_driver(dev);
 454         devres_release_all(dev);
 455         dma_deconfigure(dev);
 456         driver_sysfs_remove(dev);
 457         dev->driver = NULL;
 458         dev_set_drvdata(dev, NULL);
 459         if (dev->pm_domain && dev->pm_domain->dismiss)
 460                 dev->pm_domain->dismiss(dev);
 461         pm_runtime_reinit(dev);
 462
 463         switch (ret) {
 464         case -EPROBE_DEFER:
 465                 /* Driver requested deferred probing */
 466                 dev_dbg(dev, "Driver %s requests probe deferral\n", drv->name);
 467                 driver_deferred_probe_add(dev);
 468                 /* Did a trigger occur while probing? Need to re-trigger if yes */
 469                 if (local_trigger_count != atomic_read(&deferred_trigger_count))
 470                         driver_deferred_probe_trigger();
 471                 break;
 472         case -ENODEV:
 473         case -ENXIO:
 474                 pr_debug("%s: probe of %s rejects match %d\n",
 475                          drv->name, dev_name(dev), ret);
 476                 break;
 477         default:
 478                 /* driver matched but the probe failed */
 479                 printk(KERN_WARNING
 480                        "%s: probe of %s failed with error %d\n",
 481                        drv->name, dev_name(dev), ret);
 482         }
 483         /*
 484          * Ignore errors returned by ->probe so that the next driver can try
 485          * its luck.
 486          */
 487         ret = 0;
 488 done:
 489         atomic_dec(&probe_count);
 490         wake_up_all(&probe_waitqueue);
 491         return ret;
 492 }
 493
 494 /**
 495  * driver_probe_done
 496  * Determine if the probe sequence is finished or not.
 497  *
 498  * Should somehow figure out how to use a semaphore, not an atomic variable...
 499  */
 500 int driver_probe_done(void)
 501 {
 502         pr_debug("%s: probe_count = %d\n", __func__,
 503                  atomic_read(&probe_count));
 504         if (atomic_read(&probe_count))
 505                 return -EBUSY;
 506         return 0;
 507 }
 508
 509 /**
 510  * wait_for_device_probe
 511  * Wait for device probing to be completed.
 512  */
 513 void wait_for_device_probe(void)
 514 {
 515         /* wait for the deferred probe workqueue to finish */
 516         flush_work(&deferred_probe_work);
 517
 518         /* wait for the known devices to complete their probing */
 519         wait_event(probe_waitqueue, atomic_read(&probe_count) == 0);
 520         async_synchronize_full();
 521 }
 522 EXPORT_SYMBOL_GPL(wait_for_device_probe);
 523
 524 /**
 525  * driver_probe_device - attempt to bind device & driver together
 526  * @drv: driver to bind a device to
 527  * @dev: device to try to bind to the driver
 528  *
 529  * This function returns -ENODEV if the device is not registered,
 530  * 1 if the device is bound successfully and 0 otherwise.
 531  *
 532  * This function must be called with @dev lock held.  When called for a
 533  * USB interface, @dev->parent lock must be held as well.
 534  *
 535  * If the device has a parent, runtime-resume the parent before driver probing.
 536  */
 537 int driver_probe_device(struct device_driver *drv, struct device *dev)
 538 {
 539         int ret = 0;
 540
 541         if (!device_is_registered(dev))
 542                 return -ENODEV;
 543
 544         pr_debug("bus: '%s': %s: matched device %s with driver %s\n",
 545                  drv->bus->name, __func__, dev_name(dev), drv->name);
 546
 547         pm_runtime_get_suppliers(dev);
 548         if (dev->parent)
 549                 pm_runtime_get_sync(dev->parent);
 550
 551         pm_runtime_barrier(dev);
 552         ret = really_probe(dev, drv);
 553         pm_request_idle(dev);
 554
 555         if (dev->parent)
 556                 pm_runtime_put(dev->parent);
 557
 558         pm_runtime_put_suppliers(dev);
 559         return ret;
 560 }
 561
 562 bool driver_allows_async_probing(struct device_driver *drv)
 563 {
 564         switch (drv->probe_type) {
 565         case PROBE_PREFER_ASYNCHRONOUS:
 566                 return true;
 567
 568         case PROBE_FORCE_SYNCHRONOUS:
 569                 return false;
 570
 571         default:
 572                 if (module_requested_async_probing(drv->owner))
 573                         return true;
 574
 575                 return false;
 576         }
 577 }
 578
 579 struct device_attach_data {
 580         struct device *dev;
 581
 582         /*
 583          * Indicates whether we are are considering asynchronous probing or
 584          * not. Only initial binding after device or driver registration
 585          * (including deferral processing) may be done asynchronously, the
 586          * rest is always synchronous, as we expect it is being done by
 587          * request from userspace.
 588          */
 589         bool check_async;
 590
 591         /*
 592          * Indicates if we are binding synchronous or asynchronous drivers.
 593          * When asynchronous probing is enabled we'll execute 2 passes
 594          * over drivers: first pass doing synchronous probing and second
 595          * doing asynchronous probing (if synchronous did not succeed -
 596          * most likely because there was no driver requiring synchronous
 597          * probing - and we found asynchronous driver during first pass).
 598          * The 2 passes are done because we can't shoot asynchronous
 599          * probe for given device and driver from bus_for_each_drv() since
 600          * driver pointer is not guaranteed to stay valid once
 601          * bus_for_each_drv() iterates to the next driver on the bus.
 602          */
 603         bool want_async;
 604
 605         /*
 606          * We'll set have_async to 'true' if, while scanning for matching
 607          * driver, we'll encounter one that requests asynchronous probing.
 608          */
 609         bool have_async;
 610 };
 611
 612 static int __device_attach_driver(struct device_driver *drv, void *_data)
 613 {
 614         struct device_attach_data *data = _data;
 615         struct device *dev = data->dev;
 616         bool async_allowed;
 617         int ret;
 618
 619         /*
 620          * Check if device has already been claimed. This may
 621          * happen with driver loading, device discovery/registration,
 622          * and deferred probe processing happens all at once with
 623          * multiple threads.
 624          */
 625         if (dev->driver)
 626                 return -EBUSY;
 627
 628         ret = driver_match_device(drv, dev);
 629         if (ret == 0) {
 630                 /* no match */
 631                 return 0;
 632         } else if (ret == -EPROBE_DEFER) {
 633                 dev_dbg(dev, "Device match requests probe deferral\n");
 634                 driver_deferred_probe_add(dev);
 635                 /*
 636                  * Device can't match with a driver right now, so don't attempt
 637                  * to match or bind with other drivers on the bus.
 638                  */
 639                 return ret;
 640         } else if (ret < 0) {
 641                 dev_dbg(dev, "Bus failed to match device: %d", ret);
 642                 return ret;
 643         } /* ret > 0 means positive match */
 644
 645         async_allowed = driver_allows_async_probing(drv);
 646
 647         if (async_allowed)
 648                 data->have_async = true;
 649
 650         if (data->check_async && async_allowed != data->want_async)
 651                 return 0;
 652
 653         return driver_probe_device(drv, dev);
 654 }
 655
 656 static void __device_attach_async_helper(void *_dev, async_cookie_t cookie)
 657 {
 658         struct device *dev = _dev;
 659         struct device_attach_data data = {
 660                 .dev            = dev,
 661                 .check_async    = true,
 662                 .want_async     = true,
 663         };
 664
 665         device_lock(dev);
 666
 667         if (dev->parent)
 668                 pm_runtime_get_sync(dev->parent);
 669
 670         bus_for_each_drv(dev->bus, NULL, &data, __device_attach_driver);
 671         dev_dbg(dev, "async probe completed\n");
 672
 673         pm_request_idle(dev);
 674
 675         if (dev->parent)
 676                 pm_runtime_put(dev->parent);
 677
 678         device_unlock(dev);
 679
 680         put_device(dev);
 681 }
 682
 683 static int __device_attach(struct device *dev, bool allow_async)
 684 {
 685         int ret = 0;
 686
 687         device_lock(dev);
 688         if (dev->driver) {
 689                 if (device_is_bound(dev)) {
 690                         ret = 1;
 691                         goto out_unlock;
 692                 }
 693                 ret = device_bind_driver(dev);
 694                 if (ret == 0)
 695                         ret = 1;
 696                 else {
 697                         dev->driver = NULL;
 698                         ret = 0;
 699                 }
 700         } else {
 701                 struct device_attach_data data = {
 702                         .dev = dev,
 703                         .check_async = allow_async,
 704                         .want_async = false,
 705                 };
 706
 707                 if (dev->parent)
 708                         pm_runtime_get_sync(dev->parent);
 709
 710                 ret = bus_for_each_drv(dev->bus, NULL, &data,
 711                                         __device_attach_driver);
 712                 if (!ret && allow_async && data.have_async) {
 713                         /*
 714                          * If we could not find appropriate driver
 715                          * synchronously and we are allowed to do
 716                          * async probes and there are drivers that
 717                          * want to probe asynchronously, we'll
 718                          * try them.
 719                          */
 720                         dev_dbg(dev, "scheduling asynchronous probe\n");
 721                         get_device(dev);
 722                         async_schedule(__device_attach_async_helper, dev);
 723                 } else {
 724                         pm_request_idle(dev);
 725                 }
 726
 727                 if (dev->parent)
 728                         pm_runtime_put(dev->parent);
 729         }
 730 out_unlock:
 731         device_unlock(dev);
 732         return ret;
 733 }
 734
 735 /**
 736  * device_attach - try to attach device to a driver.
 737  * @dev: device.
 738  *
 739  * Walk the list of drivers that the bus has and call
 740  * driver_probe_device() for each pair. If a compatible
 741  * pair is found, break out and return.
 742  *
 743  * Returns 1 if the device was bound to a driver;
 744  * 0 if no matching driver was found;
 745  * -ENODEV if the device is not registered.
 746  *
 747  * When called for a USB interface, @dev->parent lock must be held.
 748  */
 749 int device_attach(struct device *dev)
 750 {
 751         return __device_attach(dev, false);
 752 }
 753 EXPORT_SYMBOL_GPL(device_attach);
 754
 755 void device_initial_probe(struct device *dev)
 756 {
 757         __device_attach(dev, true);
 758 }
 759
 760 static int __driver_attach(struct device *dev, void *data)
 761 {
 762         struct device_driver *drv = data;
 763         int ret;
 764
 765         /*
 766          * Lock device and try to bind to it. We drop the error
 767          * here and always return 0, because we need to keep trying
 768          * to bind to devices and some drivers will return an error
 769          * simply if it didn't support the device.
 770          *
 771          * driver_probe_device() will spit a warning if there
 772          * is an error.
 773          */
 774
 775         ret = driver_match_device(drv, dev);
 776         if (ret == 0) {
 777                 /* no match */
 778                 return 0;
 779         } else if (ret == -EPROBE_DEFER) {
 780                 dev_dbg(dev, "Device match requests probe deferral\n");
 781                 driver_deferred_probe_add(dev);
 782                 /*
 783                  * Driver could not match with device, but may match with
 784                  * another device on the bus.
 785                  */
 786                 return 0;
 787         } else if (ret < 0) {
 788                 dev_dbg(dev, "Bus failed to match device: %d\n", ret);
 789                 /*
 790                  * Driver could not match with device, but may match with
 791                  * another device on the bus.
 792                  */
 793                 return 0;
 794         } /* ret > 0 means positive match */
 795
 796         if (dev->parent)        /* Needed for USB */
 797                 device_lock(dev->parent);
 798         device_lock(dev);
 799         if (!dev->driver)
 800                 driver_probe_device(drv, dev);
 801         device_unlock(dev);
 802         if (dev->parent)
 803                 device_unlock(dev->parent);
 804
 805         return 0;
 806 }
 807
 808 /**
 809  * driver_attach - try to bind driver to devices.
 810  * @drv: driver.
 811  *
 812  * Walk the list of devices that the bus has on it and try to
 813  * match the driver with each one.  If driver_probe_device()
 814  * returns 0 and the @dev->driver is set, we've found a
 815  * compatible pair.
 816  */
 817 int driver_attach(struct device_driver *drv)
 818 {
 819         return bus_for_each_dev(drv->bus, NULL, drv, __driver_attach);
 820 }
 821 EXPORT_SYMBOL_GPL(driver_attach);
 822
 823 /*
 824  * __device_release_driver() must be called with @dev lock held.
 825  * When called for a USB interface, @dev->parent lock must be held as well.
 826  */
 827 static void __device_release_driver(struct device *dev, struct device *parent)
 828 {
 829         struct device_driver *drv;
 830
 831         drv = dev->driver;
 832         if (drv) {
 833                 pm_runtime_get_sync(dev);
 834
 835                 while (device_links_busy(dev)) {
 836                         device_unlock(dev);
 837                         if (parent)
 838                                 device_unlock(parent);
 839
 840                         device_links_unbind_consumers(dev);
 841                         if (parent)
 842                                 device_lock(parent);
 843
 844                         device_lock(dev);
 845                         /*
 846                          * A concurrent invocation of the same function might
 847                          * have released the driver successfully while this one
 848                          * was waiting, so check for that.
 849                          */
 850                         if (dev->driver != drv) {
 851                                 pm_runtime_put(dev);
 852                                 return;
 853                         }
 854                 }
 855
 856                 pm_runtime_clean_up_links(dev);
 857
 858                 driver_sysfs_remove(dev);
 859
 860                 if (dev->bus)
 861                         blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 862                                                      BUS_NOTIFY_UNBIND_DRIVER,
 863                                                      dev);
 864
 865                 pm_runtime_put_sync(dev);
 866
 867                 if (dev->bus && dev->bus->remove)
 868                         dev->bus->remove(dev);
 869                 else if (drv->remove)
 870                         drv->remove(dev);
 871
 872                 device_links_driver_cleanup(dev);
 873
 874                 devres_release_all(dev);
 875                 dma_deconfigure(dev);
 876                 dev->driver = NULL;
 877                 dev_set_drvdata(dev, NULL);
 878                 if (dev->pm_domain && dev->pm_domain->dismiss)
 879                         dev->pm_domain->dismiss(dev);
 880                 pm_runtime_reinit(dev);
 881
 882                 klist_remove(&dev->p->knode_driver);
 883                 device_pm_check_callbacks(dev);
 884                 if (dev->bus)
 885                         blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 886                                                      BUS_NOTIFY_UNBOUND_DRIVER,
 887                                                      dev);
 888
 889                 kobject_uevent(&dev->kobj, KOBJ_UNBIND);
 890         }
 891 }
 892
 893 void device_release_driver_internal(struct device *dev,
 894                                     struct device_driver *drv,
 895                                     struct device *parent)
 896 {
 897         if (parent)
 898                 device_lock(parent);
 899
 900         device_lock(dev);
 901         if (!drv || drv == dev->driver)
 902                 __device_release_driver(dev, parent);
 903
 904         device_unlock(dev);
 905         if (parent)
 906                 device_unlock(parent);
 907 }
 908
 909 /**
 910  * device_release_driver - manually detach device from driver.
 911  * @dev: device.
 912  *
 913  * Manually detach device from driver.
 914  * When called for a USB interface, @dev->parent lock must be held.
 915  *
 916  * If this function is to be called with @dev->parent lock held, ensure that
 917  * the device's consumers are unbound in advance or that their locks can be
 918  * acquired under the @dev->parent lock.
 919  */
 920 void device_release_driver(struct device *dev)
 921 {
 922         /*
 923          * If anyone calls device_release_driver() recursively from
 924          * within their ->remove callback for the same device, they
 925          * will deadlock right here.
 926          */
 927         device_release_driver_internal(dev, NULL, NULL);
 928 }
 929 EXPORT_SYMBOL_GPL(device_release_driver);
 930
 931 /**
 932  * driver_detach - detach driver from all devices it controls.
 933  * @drv: driver.
 934  */
 935 void driver_detach(struct device_driver *drv)
 936 {
 937         struct device_private *dev_prv;
 938         struct device *dev;
 939
 940         if (driver_allows_async_probing(drv))
 941                 async_synchronize_full();
 942
 943         for (;;) {
 944                 spin_lock(&drv->p->klist_devices.k_lock);
 945                 if (list_empty(&drv->p->klist_devices.k_list)) {
 946                         spin_unlock(&drv->p->klist_devices.k_lock);
 947                         break;
 948                 }
 949                 dev_prv = list_entry(drv->p->klist_devices.k_list.prev,
 950                                      struct device_private,
 951                                      knode_driver.n_node);
 952                 dev = dev_prv->device;
 953                 get_device(dev);
 954                 spin_unlock(&drv->p->klist_devices.k_lock);
 955                 device_release_driver_internal(dev, drv, dev->parent);
 956                 put_device(dev);
 957         }
 958 }