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