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
 248         device_pm_check_callbacks(dev);
 249
 250         /*
 251          * Make sure the device is no longer in one of the deferred lists and
 252          * kick off retrying all pending devices
 253          */
 254         driver_deferred_probe_del(dev);
 255         driver_deferred_probe_trigger();
 256
 257         if (dev->bus)
 258                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 259                                              BUS_NOTIFY_BOUND_DRIVER, dev);
 260 }
 261
 262 static int driver_sysfs_add(struct device *dev)
 263 {
 264         int ret;
 265
 266         if (dev->bus)
 267                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 268                                              BUS_NOTIFY_BIND_DRIVER, dev);
 269
 270         ret = sysfs_create_link(&dev->driver->p->kobj, &dev->kobj,
 271                           kobject_name(&dev->kobj));
 272         if (ret == 0) {
 273                 ret = sysfs_create_link(&dev->kobj, &dev->driver->p->kobj,
 274                                         "driver");
 275                 if (ret)
 276                         sysfs_remove_link(&dev->driver->p->kobj,
 277                                         kobject_name(&dev->kobj));
 278         }
 279         return ret;
 280 }
 281
 282 static void driver_sysfs_remove(struct device *dev)
 283 {
 284         struct device_driver *drv = dev->driver;
 285
 286         if (drv) {
 287                 sysfs_remove_link(&drv->p->kobj, kobject_name(&dev->kobj));
 288                 sysfs_remove_link(&dev->kobj, "driver");
 289         }
 290 }
 291
 292 /**
 293  * device_bind_driver - bind a driver to one device.
 294  * @dev: device.
 295  *
 296  * Allow manual attachment of a driver to a device.
 297  * Caller must have already set @dev->driver.
 298  *
 299  * Note that this does not modify the bus reference count
 300  * nor take the bus's rwsem. Please verify those are accounted
 301  * for before calling this. (It is ok to call with no other effort
 302  * from a driver's probe() method.)
 303  *
 304  * This function must be called with the device lock held.
 305  */
 306 int device_bind_driver(struct device *dev)
 307 {
 308         int ret;
 309
 310         ret = driver_sysfs_add(dev);
 311         if (!ret)
 312                 driver_bound(dev);
 313         else if (dev->bus)
 314                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 315                                              BUS_NOTIFY_DRIVER_NOT_BOUND, dev);
 316         return ret;
 317 }
 318 EXPORT_SYMBOL_GPL(device_bind_driver);
 319
 320 static atomic_t probe_count = ATOMIC_INIT(0);
 321 static DECLARE_WAIT_QUEUE_HEAD(probe_waitqueue);
 322
 323 static int really_probe(struct device *dev, struct device_driver *drv)
 324 {
 325         int ret = -EPROBE_DEFER;
 326         int local_trigger_count = atomic_read(&deferred_trigger_count);
 327         bool test_remove = IS_ENABLED(CONFIG_DEBUG_TEST_DRIVER_REMOVE) &&
 328                            !drv->suppress_bind_attrs;
 329
 330         if (defer_all_probes) {
 331                 /*
 332                  * Value of defer_all_probes can be set only by
 333                  * device_defer_all_probes_enable() which, in turn, will call
 334                  * wait_for_device_probe() right after that to avoid any races.
 335                  */
 336                 dev_dbg(dev, "Driver %s force probe deferral\n", drv->name);
 337                 driver_deferred_probe_add(dev);
 338                 return ret;
 339         }
 340
 341         atomic_inc(&probe_count);
 342         pr_debug("bus: '%s': %s: probing driver %s with device %s\n",
 343                  drv->bus->name, __func__, drv->name, dev_name(dev));
 344         WARN_ON(!list_empty(&dev->devres_head));
 345
 346 re_probe:
 347         dev->driver = drv;
 348
 349         /* If using pinctrl, bind pins now before probing */
 350         ret = pinctrl_bind_pins(dev);
 351         if (ret)
 352                 goto pinctrl_bind_failed;
 353
 354         if (driver_sysfs_add(dev)) {
 355                 printk(KERN_ERR "%s: driver_sysfs_add(%s) failed\n",
 356                         __func__, dev_name(dev));
 357                 goto probe_failed;
 358         }
 359
 360         if (dev->pm_domain && dev->pm_domain->activate) {
 361                 ret = dev->pm_domain->activate(dev);
 362                 if (ret)
 363                         goto probe_failed;
 364         }
 365
 366         /*
 367          * Ensure devices are listed in devices_kset in correct order
 368          * It's important to move Dev to the end of devices_kset before
 369          * calling .probe, because it could be recursive and parent Dev
 370          * should always go first
 371          */
 372         devices_kset_move_last(dev);
 373
 374         if (dev->bus->probe) {
 375                 ret = dev->bus->probe(dev);
 376                 if (ret)
 377                         goto probe_failed;
 378         } else if (drv->probe) {
 379                 ret = drv->probe(dev);
 380                 if (ret)
 381                         goto probe_failed;
 382         }
 383
 384         if (test_remove) {
 385                 test_remove = false;
 386
 387                 if (dev->bus->remove)
 388                         dev->bus->remove(dev);
 389                 else if (drv->remove)
 390                         drv->remove(dev);
 391
 392                 devres_release_all(dev);
 393                 driver_sysfs_remove(dev);
 394                 dev->driver = NULL;
 395                 dev_set_drvdata(dev, NULL);
 396                 if (dev->pm_domain && dev->pm_domain->dismiss)
 397                         dev->pm_domain->dismiss(dev);
 398                 pm_runtime_reinit(dev);
 399
 400                 goto re_probe;
 401         }
 402
 403         pinctrl_init_done(dev);
 404
 405         if (dev->pm_domain && dev->pm_domain->sync)
 406                 dev->pm_domain->sync(dev);
 407
 408         driver_bound(dev);
 409         ret = 1;
 410         pr_debug("bus: '%s': %s: bound device %s to driver %s\n",
 411                  drv->bus->name, __func__, dev_name(dev), drv->name);
 412         goto done;
 413
 414 probe_failed:
 415         if (dev->bus)
 416                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 417                                              BUS_NOTIFY_DRIVER_NOT_BOUND, dev);
 418 pinctrl_bind_failed:
 419         devres_release_all(dev);
 420         driver_sysfs_remove(dev);
 421         dev->driver = NULL;
 422         dev_set_drvdata(dev, NULL);
 423         if (dev->pm_domain && dev->pm_domain->dismiss)
 424                 dev->pm_domain->dismiss(dev);
 425         pm_runtime_reinit(dev);
 426
 427         switch (ret) {
 428         case -EPROBE_DEFER:
 429                 /* Driver requested deferred probing */
 430                 dev_dbg(dev, "Driver %s requests probe deferral\n", drv->name);
 431                 driver_deferred_probe_add(dev);
 432                 /* Did a trigger occur while probing? Need to re-trigger if yes */
 433                 if (local_trigger_count != atomic_read(&deferred_trigger_count))
 434                         driver_deferred_probe_trigger();
 435                 break;
 436         case -ENODEV:
 437         case -ENXIO:
 438                 pr_debug("%s: probe of %s rejects match %d\n",
 439                          drv->name, dev_name(dev), ret);
 440                 break;
 441         default:
 442                 /* driver matched but the probe failed */
 443                 printk(KERN_WARNING
 444                        "%s: probe of %s failed with error %d\n",
 445                        drv->name, dev_name(dev), ret);
 446         }
 447         /*
 448          * Ignore errors returned by ->probe so that the next driver can try
 449          * its luck.
 450          */
 451         ret = 0;
 452 done:
 453         atomic_dec(&probe_count);
 454         wake_up(&probe_waitqueue);
 455         return ret;
 456 }
 457
 458 /**
 459  * driver_probe_done
 460  * Determine if the probe sequence is finished or not.
 461  *
 462  * Should somehow figure out how to use a semaphore, not an atomic variable...
 463  */
 464 int driver_probe_done(void)
 465 {
 466         pr_debug("%s: probe_count = %d\n", __func__,
 467                  atomic_read(&probe_count));
 468         if (atomic_read(&probe_count))
 469                 return -EBUSY;
 470         return 0;
 471 }
 472
 473 /**
 474  * wait_for_device_probe
 475  * Wait for device probing to be completed.
 476  */
 477 void wait_for_device_probe(void)
 478 {
 479         /* wait for the deferred probe workqueue to finish */
 480         flush_work(&deferred_probe_work);
 481
 482         /* wait for the known devices to complete their probing */
 483         wait_event(probe_waitqueue, atomic_read(&probe_count) == 0);
 484         async_synchronize_full();
 485 }
 486 EXPORT_SYMBOL_GPL(wait_for_device_probe);
 487
 488 /**
 489  * driver_probe_device - attempt to bind device & driver together
 490  * @drv: driver to bind a device to
 491  * @dev: device to try to bind to the driver
 492  *
 493  * This function returns -ENODEV if the device is not registered,
 494  * 1 if the device is bound successfully and 0 otherwise.
 495  *
 496  * This function must be called with @dev lock held.  When called for a
 497  * USB interface, @dev->parent lock must be held as well.
 498  *
 499  * If the device has a parent, runtime-resume the parent before driver probing.
 500  */
 501 int driver_probe_device(struct device_driver *drv, struct device *dev)
 502 {
 503         int ret = 0;
 504
 505         if (!device_is_registered(dev))
 506                 return -ENODEV;
 507
 508         pr_debug("bus: '%s': %s: matched device %s with driver %s\n",
 509                  drv->bus->name, __func__, dev_name(dev), drv->name);
 510
 511         if (dev->parent)
 512                 pm_runtime_get_sync(dev->parent);
 513
 514         pm_runtime_barrier(dev);
 515         ret = really_probe(dev, drv);
 516         pm_request_idle(dev);
 517
 518         if (dev->parent)
 519                 pm_runtime_put(dev->parent);
 520
 521         return ret;
 522 }
 523
 524 bool driver_allows_async_probing(struct device_driver *drv)
 525 {
 526         switch (drv->probe_type) {
 527         case PROBE_PREFER_ASYNCHRONOUS:
 528                 return true;
 529
 530         case PROBE_FORCE_SYNCHRONOUS:
 531                 return false;
 532
 533         default:
 534                 if (module_requested_async_probing(drv->owner))
 535                         return true;
 536
 537                 return false;
 538         }
 539 }
 540
 541 struct device_attach_data {
 542         struct device *dev;
 543
 544         /*
 545          * Indicates whether we are are considering asynchronous probing or
 546          * not. Only initial binding after device or driver registration
 547          * (including deferral processing) may be done asynchronously, the
 548          * rest is always synchronous, as we expect it is being done by
 549          * request from userspace.
 550          */
 551         bool check_async;
 552
 553         /*
 554          * Indicates if we are binding synchronous or asynchronous drivers.
 555          * When asynchronous probing is enabled we'll execute 2 passes
 556          * over drivers: first pass doing synchronous probing and second
 557          * doing asynchronous probing (if synchronous did not succeed -
 558          * most likely because there was no driver requiring synchronous
 559          * probing - and we found asynchronous driver during first pass).
 560          * The 2 passes are done because we can't shoot asynchronous
 561          * probe for given device and driver from bus_for_each_drv() since
 562          * driver pointer is not guaranteed to stay valid once
 563          * bus_for_each_drv() iterates to the next driver on the bus.
 564          */
 565         bool want_async;
 566
 567         /*
 568          * We'll set have_async to 'true' if, while scanning for matching
 569          * driver, we'll encounter one that requests asynchronous probing.
 570          */
 571         bool have_async;
 572 };
 573
 574 static int __device_attach_driver(struct device_driver *drv, void *_data)
 575 {
 576         struct device_attach_data *data = _data;
 577         struct device *dev = data->dev;
 578         bool async_allowed;
 579         int ret;
 580
 581         /*
 582          * Check if device has already been claimed. This may
 583          * happen with driver loading, device discovery/registration,
 584          * and deferred probe processing happens all at once with
 585          * multiple threads.
 586          */
 587         if (dev->driver)
 588                 return -EBUSY;
 589
 590         ret = driver_match_device(drv, dev);
 591         if (ret == 0) {
 592                 /* no match */
 593                 return 0;
 594         } else if (ret == -EPROBE_DEFER) {
 595                 dev_dbg(dev, "Device match requests probe deferral\n");
 596                 driver_deferred_probe_add(dev);
 597         } else if (ret < 0) {
 598                 dev_dbg(dev, "Bus failed to match device: %d", ret);
 599                 return ret;
 600         } /* ret > 0 means positive match */
 601
 602         async_allowed = driver_allows_async_probing(drv);
 603
 604         if (async_allowed)
 605                 data->have_async = true;
 606
 607         if (data->check_async && async_allowed != data->want_async)
 608                 return 0;
 609
 610         return driver_probe_device(drv, dev);
 611 }
 612
 613 static void __device_attach_async_helper(void *_dev, async_cookie_t cookie)
 614 {
 615         struct device *dev = _dev;
 616         struct device_attach_data data = {
 617                 .dev            = dev,
 618                 .check_async    = true,
 619                 .want_async     = true,
 620         };
 621
 622         device_lock(dev);
 623
 624         if (dev->parent)
 625                 pm_runtime_get_sync(dev->parent);
 626
 627         bus_for_each_drv(dev->bus, NULL, &data, __device_attach_driver);
 628         dev_dbg(dev, "async probe completed\n");
 629
 630         pm_request_idle(dev);
 631
 632         if (dev->parent)
 633                 pm_runtime_put(dev->parent);
 634
 635         device_unlock(dev);
 636
 637         put_device(dev);
 638 }
 639
 640 static int __device_attach(struct device *dev, bool allow_async)
 641 {
 642         int ret = 0;
 643
 644         device_lock(dev);
 645         if (dev->driver) {
 646                 if (device_is_bound(dev)) {
 647                         ret = 1;
 648                         goto out_unlock;
 649                 }
 650                 ret = device_bind_driver(dev);
 651                 if (ret == 0)
 652                         ret = 1;
 653                 else {
 654                         dev->driver = NULL;
 655                         ret = 0;
 656                 }
 657         } else {
 658                 struct device_attach_data data = {
 659                         .dev = dev,
 660                         .check_async = allow_async,
 661                         .want_async = false,
 662                 };
 663
 664                 if (dev->parent)
 665                         pm_runtime_get_sync(dev->parent);
 666
 667                 ret = bus_for_each_drv(dev->bus, NULL, &data,
 668                                         __device_attach_driver);
 669                 if (!ret && allow_async && data.have_async) {
 670                         /*
 671                          * If we could not find appropriate driver
 672                          * synchronously and we are allowed to do
 673                          * async probes and there are drivers that
 674                          * want to probe asynchronously, we'll
 675                          * try them.
 676                          */
 677                         dev_dbg(dev, "scheduling asynchronous probe\n");
 678                         get_device(dev);
 679                         async_schedule(__device_attach_async_helper, dev);
 680                 } else {
 681                         pm_request_idle(dev);
 682                 }
 683
 684                 if (dev->parent)
 685                         pm_runtime_put(dev->parent);
 686         }
 687 out_unlock:
 688         device_unlock(dev);
 689         return ret;
 690 }
 691
 692 /**
 693  * device_attach - try to attach device to a driver.
 694  * @dev: device.
 695  *
 696  * Walk the list of drivers that the bus has and call
 697  * driver_probe_device() for each pair. If a compatible
 698  * pair is found, break out and return.
 699  *
 700  * Returns 1 if the device was bound to a driver;
 701  * 0 if no matching driver was found;
 702  * -ENODEV if the device is not registered.
 703  *
 704  * When called for a USB interface, @dev->parent lock must be held.
 705  */
 706 int device_attach(struct device *dev)
 707 {
 708         return __device_attach(dev, false);
 709 }
 710 EXPORT_SYMBOL_GPL(device_attach);
 711
 712 void device_initial_probe(struct device *dev)
 713 {
 714         __device_attach(dev, true);
 715 }
 716
 717 static int __driver_attach(struct device *dev, void *data)
 718 {
 719         struct device_driver *drv = data;
 720         int ret;
 721
 722         /*
 723          * Lock device and try to bind to it. We drop the error
 724          * here and always return 0, because we need to keep trying
 725          * to bind to devices and some drivers will return an error
 726          * simply if it didn't support the device.
 727          *
 728          * driver_probe_device() will spit a warning if there
 729          * is an error.
 730          */
 731
 732         ret = driver_match_device(drv, dev);
 733         if (ret == 0) {
 734                 /* no match */
 735                 return 0;
 736         } else if (ret == -EPROBE_DEFER) {
 737                 dev_dbg(dev, "Device match requests probe deferral\n");
 738                 driver_deferred_probe_add(dev);
 739         } else if (ret < 0) {
 740                 dev_dbg(dev, "Bus failed to match device: %d", ret);
 741                 return ret;
 742         } /* ret > 0 means positive match */
 743
 744         if (dev->parent)        /* Needed for USB */
 745                 device_lock(dev->parent);
 746         device_lock(dev);
 747         if (!dev->driver)
 748                 driver_probe_device(drv, dev);
 749         device_unlock(dev);
 750         if (dev->parent)
 751                 device_unlock(dev->parent);
 752
 753         return 0;
 754 }
 755
 756 /**
 757  * driver_attach - try to bind driver to devices.
 758  * @drv: driver.
 759  *
 760  * Walk the list of devices that the bus has on it and try to
 761  * match the driver with each one.  If driver_probe_device()
 762  * returns 0 and the @dev->driver is set, we've found a
 763  * compatible pair.
 764  */
 765 int driver_attach(struct device_driver *drv)
 766 {
 767         return bus_for_each_dev(drv->bus, NULL, drv, __driver_attach);
 768 }
 769 EXPORT_SYMBOL_GPL(driver_attach);
 770
 771 /*
 772  * __device_release_driver() must be called with @dev lock held.
 773  * When called for a USB interface, @dev->parent lock must be held as well.
 774  */
 775 static void __device_release_driver(struct device *dev)
 776 {
 777         struct device_driver *drv;
 778
 779         drv = dev->driver;
 780         if (drv) {
 781                 if (driver_allows_async_probing(drv))
 782                         async_synchronize_full();
 783
 784                 pm_runtime_get_sync(dev);
 785
 786                 driver_sysfs_remove(dev);
 787
 788                 if (dev->bus)
 789                         blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 790                                                      BUS_NOTIFY_UNBIND_DRIVER,
 791                                                      dev);
 792
 793                 pm_runtime_put_sync(dev);
 794
 795                 if (dev->bus && dev->bus->remove)
 796                         dev->bus->remove(dev);
 797                 else if (drv->remove)
 798                         drv->remove(dev);
 799                 devres_release_all(dev);
 800                 dev->driver = NULL;
 801                 dev_set_drvdata(dev, NULL);
 802                 if (dev->pm_domain && dev->pm_domain->dismiss)
 803                         dev->pm_domain->dismiss(dev);
 804                 pm_runtime_reinit(dev);
 805
 806                 klist_remove(&dev->p->knode_driver);
 807                 device_pm_check_callbacks(dev);
 808                 if (dev->bus)
 809                         blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 810                                                      BUS_NOTIFY_UNBOUND_DRIVER,
 811                                                      dev);
 812         }
 813 }
 814
 815 /**
 816  * device_release_driver - manually detach device from driver.
 817  * @dev: device.
 818  *
 819  * Manually detach device from driver.
 820  * When called for a USB interface, @dev->parent lock must be held.
 821  */
 822 void device_release_driver(struct device *dev)
 823 {
 824         /*
 825          * If anyone calls device_release_driver() recursively from
 826          * within their ->remove callback for the same device, they
 827          * will deadlock right here.
 828          */
 829         device_lock(dev);
 830         __device_release_driver(dev);
 831         device_unlock(dev);
 832 }
 833 EXPORT_SYMBOL_GPL(device_release_driver);
 834
 835 /**
 836  * driver_detach - detach driver from all devices it controls.
 837  * @drv: driver.
 838  */
 839 void driver_detach(struct device_driver *drv)
 840 {
 841         struct device_private *dev_prv;
 842         struct device *dev;
 843
 844         for (;;) {
 845                 spin_lock(&drv->p->klist_devices.k_lock);
 846                 if (list_empty(&drv->p->klist_devices.k_list)) {
 847                         spin_unlock(&drv->p->klist_devices.k_lock);
 848                         break;
 849                 }
 850                 dev_prv = list_entry(drv->p->klist_devices.k_list.prev,
 851                                      struct device_private,
 852                                      knode_driver.n_node);
 853                 dev = dev_prv->device;
 854                 get_device(dev);
 855                 spin_unlock(&drv->p->klist_devices.k_lock);
 856
 857                 if (dev->parent)        /* Needed for USB */
 858                         device_lock(dev->parent);
 859                 device_lock(dev);
 860                 if (dev->driver == drv)
 861                         __device_release_driver(dev);
 862                 device_unlock(dev);
 863                 if (dev->parent)
 864                         device_unlock(dev->parent);
 865                 put_device(dev);
 866         }
 867 }