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         if (!list_empty(&dev->devres_head)) {
 345                 dev_crit(dev, "Resources present before probing\n");
 346                 ret = -EBUSY;
 347                 goto done;
 348         }
 349
 350 re_probe:
 351         dev->driver = drv;
 352
 353         /* If using pinctrl, bind pins now before probing */
 354         ret = pinctrl_bind_pins(dev);
 355         if (ret)
 356                 goto pinctrl_bind_failed;
 357
 358         if (driver_sysfs_add(dev)) {
 359                 printk(KERN_ERR "%s: driver_sysfs_add(%s) failed\n",
 360                         __func__, dev_name(dev));
 361                 goto probe_failed;
 362         }
 363
 364         if (dev->pm_domain && dev->pm_domain->activate) {
 365                 ret = dev->pm_domain->activate(dev);
 366                 if (ret)
 367                         goto probe_failed;
 368         }
 369
 370         if (dev->bus->probe) {
 371                 ret = dev->bus->probe(dev);
 372                 if (ret)
 373                         goto probe_failed;
 374         } else if (drv->probe) {
 375                 ret = drv->probe(dev);
 376                 if (ret)
 377                         goto probe_failed;
 378         }
 379
 380         if (test_remove) {
 381                 test_remove = false;
 382
 383                 if (dev->bus->remove)
 384                         dev->bus->remove(dev);
 385                 else if (drv->remove)
 386                         drv->remove(dev);
 387
 388                 devres_release_all(dev);
 389                 driver_sysfs_remove(dev);
 390                 dev->driver = NULL;
 391                 dev_set_drvdata(dev, NULL);
 392                 if (dev->pm_domain && dev->pm_domain->dismiss)
 393                         dev->pm_domain->dismiss(dev);
 394                 pm_runtime_reinit(dev);
 395
 396                 goto re_probe;
 397         }
 398
 399         pinctrl_init_done(dev);
 400
 401         if (dev->pm_domain && dev->pm_domain->sync)
 402                 dev->pm_domain->sync(dev);
 403
 404         driver_bound(dev);
 405         ret = 1;
 406         pr_debug("bus: '%s': %s: bound device %s to driver %s\n",
 407                  drv->bus->name, __func__, dev_name(dev), drv->name);
 408         goto done;
 409
 410 probe_failed:
 411         if (dev->bus)
 412                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 413                                              BUS_NOTIFY_DRIVER_NOT_BOUND, dev);
 414 pinctrl_bind_failed:
 415         devres_release_all(dev);
 416         driver_sysfs_remove(dev);
 417         dev->driver = NULL;
 418         dev_set_drvdata(dev, NULL);
 419         if (dev->pm_domain && dev->pm_domain->dismiss)
 420                 dev->pm_domain->dismiss(dev);
 421         pm_runtime_reinit(dev);
 422
 423         switch (ret) {
 424         case -EPROBE_DEFER:
 425                 /* Driver requested deferred probing */
 426                 dev_dbg(dev, "Driver %s requests probe deferral\n", drv->name);
 427                 driver_deferred_probe_add(dev);
 428                 /* Did a trigger occur while probing? Need to re-trigger if yes */
 429                 if (local_trigger_count != atomic_read(&deferred_trigger_count))
 430                         driver_deferred_probe_trigger();
 431                 break;
 432         case -ENODEV:
 433         case -ENXIO:
 434                 pr_debug("%s: probe of %s rejects match %d\n",
 435                          drv->name, dev_name(dev), ret);
 436                 break;
 437         default:
 438                 /* driver matched but the probe failed */
 439                 printk(KERN_WARNING
 440                        "%s: probe of %s failed with error %d\n",
 441                        drv->name, dev_name(dev), ret);
 442         }
 443         /*
 444          * Ignore errors returned by ->probe so that the next driver can try
 445          * its luck.
 446          */
 447         ret = 0;
 448 done:
 449         atomic_dec(&probe_count);
 450         wake_up_all(&probe_waitqueue);
 451         return ret;
 452 }
 453
 454 /**
 455  * driver_probe_done
 456  * Determine if the probe sequence is finished or not.
 457  *
 458  * Should somehow figure out how to use a semaphore, not an atomic variable...
 459  */
 460 int driver_probe_done(void)
 461 {
 462         pr_debug("%s: probe_count = %d\n", __func__,
 463                  atomic_read(&probe_count));
 464         if (atomic_read(&probe_count))
 465                 return -EBUSY;
 466         return 0;
 467 }
 468
 469 /**
 470  * wait_for_device_probe
 471  * Wait for device probing to be completed.
 472  */
 473 void wait_for_device_probe(void)
 474 {
 475         /* wait for the deferred probe workqueue to finish */
 476         flush_work(&deferred_probe_work);
 477
 478         /* wait for the known devices to complete their probing */
 479         wait_event(probe_waitqueue, atomic_read(&probe_count) == 0);
 480         async_synchronize_full();
 481 }
 482 EXPORT_SYMBOL_GPL(wait_for_device_probe);
 483
 484 /**
 485  * driver_probe_device - attempt to bind device & driver together
 486  * @drv: driver to bind a device to
 487  * @dev: device to try to bind to the driver
 488  *
 489  * This function returns -ENODEV if the device is not registered,
 490  * 1 if the device is bound successfully and 0 otherwise.
 491  *
 492  * This function must be called with @dev lock held.  When called for a
 493  * USB interface, @dev->parent lock must be held as well.
 494  *
 495  * If the device has a parent, runtime-resume the parent before driver probing.
 496  */
 497 int driver_probe_device(struct device_driver *drv, struct device *dev)
 498 {
 499         int ret = 0;
 500
 501         if (!device_is_registered(dev))
 502                 return -ENODEV;
 503
 504         pr_debug("bus: '%s': %s: matched device %s with driver %s\n",
 505                  drv->bus->name, __func__, dev_name(dev), drv->name);
 506
 507         if (dev->parent)
 508                 pm_runtime_get_sync(dev->parent);
 509
 510         pm_runtime_barrier(dev);
 511         ret = really_probe(dev, drv);
 512         pm_request_idle(dev);
 513
 514         if (dev->parent)
 515                 pm_runtime_put(dev->parent);
 516
 517         return ret;
 518 }
 519
 520 bool driver_allows_async_probing(struct device_driver *drv)
 521 {
 522         switch (drv->probe_type) {
 523         case PROBE_PREFER_ASYNCHRONOUS:
 524                 return true;
 525
 526         case PROBE_FORCE_SYNCHRONOUS:
 527                 return false;
 528
 529         default:
 530                 if (module_requested_async_probing(drv->owner))
 531                         return true;
 532
 533                 return false;
 534         }
 535 }
 536
 537 struct device_attach_data {
 538         struct device *dev;
 539
 540         /*
 541          * Indicates whether we are are considering asynchronous probing or
 542          * not. Only initial binding after device or driver registration
 543          * (including deferral processing) may be done asynchronously, the
 544          * rest is always synchronous, as we expect it is being done by
 545          * request from userspace.
 546          */
 547         bool check_async;
 548
 549         /*
 550          * Indicates if we are binding synchronous or asynchronous drivers.
 551          * When asynchronous probing is enabled we'll execute 2 passes
 552          * over drivers: first pass doing synchronous probing and second
 553          * doing asynchronous probing (if synchronous did not succeed -
 554          * most likely because there was no driver requiring synchronous
 555          * probing - and we found asynchronous driver during first pass).
 556          * The 2 passes are done because we can't shoot asynchronous
 557          * probe for given device and driver from bus_for_each_drv() since
 558          * driver pointer is not guaranteed to stay valid once
 559          * bus_for_each_drv() iterates to the next driver on the bus.
 560          */
 561         bool want_async;
 562
 563         /*
 564          * We'll set have_async to 'true' if, while scanning for matching
 565          * driver, we'll encounter one that requests asynchronous probing.
 566          */
 567         bool have_async;
 568 };
 569
 570 static int __device_attach_driver(struct device_driver *drv, void *_data)
 571 {
 572         struct device_attach_data *data = _data;
 573         struct device *dev = data->dev;
 574         bool async_allowed;
 575         int ret;
 576
 577         /*
 578          * Check if device has already been claimed. This may
 579          * happen with driver loading, device discovery/registration,
 580          * and deferred probe processing happens all at once with
 581          * multiple threads.
 582          */
 583         if (dev->driver)
 584                 return -EBUSY;
 585
 586         ret = driver_match_device(drv, dev);
 587         if (ret == 0) {
 588                 /* no match */
 589                 return 0;
 590         } else if (ret == -EPROBE_DEFER) {
 591                 dev_dbg(dev, "Device match requests probe deferral\n");
 592                 driver_deferred_probe_add(dev);
 593                 /*
 594                  * Device can't match with a driver right now, so don't attempt
 595                  * to match or bind with other drivers on the bus.
 596                  */
 597                 return ret;
 598         } else if (ret < 0) {
 599                 dev_dbg(dev, "Bus failed to match device: %d", ret);
 600                 return ret;
 601         } /* ret > 0 means positive match */
 602
 603         async_allowed = driver_allows_async_probing(drv);
 604
 605         if (async_allowed)
 606                 data->have_async = true;
 607
 608         if (data->check_async && async_allowed != data->want_async)
 609                 return 0;
 610
 611         return driver_probe_device(drv, dev);
 612 }
 613
 614 static void __device_attach_async_helper(void *_dev, async_cookie_t cookie)
 615 {
 616         struct device *dev = _dev;
 617         struct device_attach_data data = {
 618                 .dev            = dev,
 619                 .check_async    = true,
 620                 .want_async     = true,
 621         };
 622
 623         device_lock(dev);
 624
 625         if (dev->parent)
 626                 pm_runtime_get_sync(dev->parent);
 627
 628         bus_for_each_drv(dev->bus, NULL, &data, __device_attach_driver);
 629         dev_dbg(dev, "async probe completed\n");
 630
 631         pm_request_idle(dev);
 632
 633         if (dev->parent)
 634                 pm_runtime_put(dev->parent);
 635
 636         device_unlock(dev);
 637
 638         put_device(dev);
 639 }
 640
 641 static int __device_attach(struct device *dev, bool allow_async)
 642 {
 643         int ret = 0;
 644
 645         device_lock(dev);
 646         if (dev->driver) {
 647                 if (device_is_bound(dev)) {
 648                         ret = 1;
 649                         goto out_unlock;
 650                 }
 651                 ret = device_bind_driver(dev);
 652                 if (ret == 0)
 653                         ret = 1;
 654                 else {
 655                         dev->driver = NULL;
 656                         ret = 0;
 657                 }
 658         } else {
 659                 struct device_attach_data data = {
 660                         .dev = dev,
 661                         .check_async = allow_async,
 662                         .want_async = false,
 663                 };
 664
 665                 if (dev->parent)
 666                         pm_runtime_get_sync(dev->parent);
 667
 668                 ret = bus_for_each_drv(dev->bus, NULL, &data,
 669                                         __device_attach_driver);
 670                 if (!ret && allow_async && data.have_async) {
 671                         /*
 672                          * If we could not find appropriate driver
 673                          * synchronously and we are allowed to do
 674                          * async probes and there are drivers that
 675                          * want to probe asynchronously, we'll
 676                          * try them.
 677                          */
 678                         dev_dbg(dev, "scheduling asynchronous probe\n");
 679                         get_device(dev);
 680                         async_schedule(__device_attach_async_helper, dev);
 681                 } else {
 682                         pm_request_idle(dev);
 683                 }
 684
 685                 if (dev->parent)
 686                         pm_runtime_put(dev->parent);
 687         }
 688 out_unlock:
 689         device_unlock(dev);
 690         return ret;
 691 }
 692
 693 /**
 694  * device_attach - try to attach device to a driver.
 695  * @dev: device.
 696  *
 697  * Walk the list of drivers that the bus has and call
 698  * driver_probe_device() for each pair. If a compatible
 699  * pair is found, break out and return.
 700  *
 701  * Returns 1 if the device was bound to a driver;
 702  * 0 if no matching driver was found;
 703  * -ENODEV if the device is not registered.
 704  *
 705  * When called for a USB interface, @dev->parent lock must be held.
 706  */
 707 int device_attach(struct device *dev)
 708 {
 709         return __device_attach(dev, false);
 710 }
 711 EXPORT_SYMBOL_GPL(device_attach);
 712
 713 void device_initial_probe(struct device *dev)
 714 {
 715         __device_attach(dev, true);
 716 }
 717
 718 static int __driver_attach(struct device *dev, void *data)
 719 {
 720         struct device_driver *drv = data;
 721         int ret;
 722
 723         /*
 724          * Lock device and try to bind to it. We drop the error
 725          * here and always return 0, because we need to keep trying
 726          * to bind to devices and some drivers will return an error
 727          * simply if it didn't support the device.
 728          *
 729          * driver_probe_device() will spit a warning if there
 730          * is an error.
 731          */
 732
 733         ret = driver_match_device(drv, dev);
 734         if (ret == 0) {
 735                 /* no match */
 736                 return 0;
 737         } else if (ret == -EPROBE_DEFER) {
 738                 dev_dbg(dev, "Device match requests probe deferral\n");
 739                 driver_deferred_probe_add(dev);
 740                 /*
 741                  * Driver could not match with device, but may match with
 742                  * another device on the bus.
 743                  */
 744                 return 0;
 745         } else if (ret < 0) {
 746                 dev_dbg(dev, "Bus failed to match device: %d", ret);
 747                 return ret;
 748         } /* ret > 0 means positive match */
 749
 750         if (dev->parent)        /* Needed for USB */
 751                 device_lock(dev->parent);
 752         device_lock(dev);
 753         if (!dev->driver)
 754                 driver_probe_device(drv, dev);
 755         device_unlock(dev);
 756         if (dev->parent)
 757                 device_unlock(dev->parent);
 758
 759         return 0;
 760 }
 761
 762 /**
 763  * driver_attach - try to bind driver to devices.
 764  * @drv: driver.
 765  *
 766  * Walk the list of devices that the bus has on it and try to
 767  * match the driver with each one.  If driver_probe_device()
 768  * returns 0 and the @dev->driver is set, we've found a
 769  * compatible pair.
 770  */
 771 int driver_attach(struct device_driver *drv)
 772 {
 773         return bus_for_each_dev(drv->bus, NULL, drv, __driver_attach);
 774 }
 775 EXPORT_SYMBOL_GPL(driver_attach);
 776
 777 /*
 778  * __device_release_driver() must be called with @dev lock held.
 779  * When called for a USB interface, @dev->parent lock must be held as well.
 780  */
 781 static void __device_release_driver(struct device *dev)
 782 {
 783         struct device_driver *drv;
 784
 785         drv = dev->driver;
 786         if (drv) {
 787                 if (driver_allows_async_probing(drv))
 788                         async_synchronize_full();
 789
 790                 pm_runtime_get_sync(dev);
 791
 792                 driver_sysfs_remove(dev);
 793
 794                 if (dev->bus)
 795                         blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 796                                                      BUS_NOTIFY_UNBIND_DRIVER,
 797                                                      dev);
 798
 799                 pm_runtime_put_sync(dev);
 800
 801                 if (dev->bus && dev->bus->remove)
 802                         dev->bus->remove(dev);
 803                 else if (drv->remove)
 804                         drv->remove(dev);
 805                 devres_release_all(dev);
 806                 dev->driver = NULL;
 807                 dev_set_drvdata(dev, NULL);
 808                 if (dev->pm_domain && dev->pm_domain->dismiss)
 809                         dev->pm_domain->dismiss(dev);
 810                 pm_runtime_reinit(dev);
 811
 812                 klist_remove(&dev->p->knode_driver);
 813                 device_pm_check_callbacks(dev);
 814                 if (dev->bus)
 815                         blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 816                                                      BUS_NOTIFY_UNBOUND_DRIVER,
 817                                                      dev);
 818         }
 819 }
 820
 821 /**
 822  * device_release_driver - manually detach device from driver.
 823  * @dev: device.
 824  *
 825  * Manually detach device from driver.
 826  * When called for a USB interface, @dev->parent lock must be held.
 827  */
 828 void device_release_driver(struct device *dev)
 829 {
 830         /*
 831          * If anyone calls device_release_driver() recursively from
 832          * within their ->remove callback for the same device, they
 833          * will deadlock right here.
 834          */
 835         device_lock(dev);
 836         __device_release_driver(dev);
 837         device_unlock(dev);
 838 }
 839 EXPORT_SYMBOL_GPL(device_release_driver);
 840
 841 /**
 842  * driver_detach - detach driver from all devices it controls.
 843  * @drv: driver.
 844  */
 845 void driver_detach(struct device_driver *drv)
 846 {
 847         struct device_private *dev_prv;
 848         struct device *dev;
 849
 850         for (;;) {
 851                 spin_lock(&drv->p->klist_devices.k_lock);
 852                 if (list_empty(&drv->p->klist_devices.k_list)) {
 853                         spin_unlock(&drv->p->klist_devices.k_lock);
 854                         break;
 855                 }
 856                 dev_prv = list_entry(drv->p->klist_devices.k_list.prev,
 857                                      struct device_private,
 858                                      knode_driver.n_node);
 859                 dev = dev_prv->device;
 860                 get_device(dev);
 861                 spin_unlock(&drv->p->klist_devices.k_lock);
 862
 863                 if (dev->parent)        /* Needed for USB */
 864                         device_lock(dev->parent);
 865                 device_lock(dev);
 866                 if (dev->driver == drv)
 867                         __device_release_driver(dev);
 868                 device_unlock(dev);
 869                 if (dev->parent)
 870                         device_unlock(dev->parent);
 871                 put_device(dev);
 872         }
 873 }