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