drivers/base/dd.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * drivers/base/dd.c - The core device/driver interactions.
   4  *
   5  * This file contains the (sometimes tricky) code that controls the
   6  * interactions between devices and drivers, which primarily includes
   7  * driver binding and unbinding.
   8  *
   9  * All of this code used to exist in drivers/base/bus.c, but was
  10  * relocated to here in the name of compartmentalization (since it wasn't
  11  * strictly code just for the 'struct bus_type'.
  12  *
  13  * Copyright (c) 2002-5 Patrick Mochel
  14  * Copyright (c) 2002-3 Open Source Development Labs
  15  * Copyright (c) 2007-2009 Greg Kroah-Hartman <gregkh@suse.de>
  16  * Copyright (c) 2007-2009 Novell Inc.
  17  */
  18
  19 #include <linux/device.h>
  20 #include <linux/delay.h>
  21 #include <linux/dma-mapping.h>
  22 #include <linux/init.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 static bool initcalls_done;
  57
  58 /*
  59  * In some cases, like suspend to RAM or hibernation, It might be reasonable
  60  * to prohibit probing of devices as it could be unsafe.
  61  * Once defer_all_probes is true all drivers probes will be forcibly deferred.
  62  */
  63 static bool defer_all_probes;
  64
  65 /*
  66  * For initcall_debug, show the deferred probes executed in late_initcall
  67  * processing.
  68  */
  69 static void deferred_probe_debug(struct device *dev)
  70 {
  71         ktime_t calltime, delta, rettime;
  72         unsigned long long duration;
  73
  74         printk(KERN_DEBUG "deferred probe %s @ %i\n", dev_name(dev),
  75                task_pid_nr(current));
  76         calltime = ktime_get();
  77         bus_probe_device(dev);
  78         rettime = ktime_get();
  79         delta = ktime_sub(rettime, calltime);
  80         duration = (unsigned long long) ktime_to_ns(delta) >> 10;
  81         printk(KERN_DEBUG "deferred probe %s returned after %lld usecs\n",
  82                dev_name(dev), duration);
  83 }
  84
  85 /*
  86  * deferred_probe_work_func() - Retry probing devices in the active list.
  87  */
  88 static void deferred_probe_work_func(struct work_struct *work)
  89 {
  90         struct device *dev;
  91         struct device_private *private;
  92         /*
  93          * This block processes every device in the deferred 'active' list.
  94          * Each device is removed from the active list and passed to
  95          * bus_probe_device() to re-attempt the probe.  The loop continues
  96          * until every device in the active list is removed and retried.
  97          *
  98          * Note: Once the device is removed from the list and the mutex is
  99          * released, it is possible for the device get freed by another thread
 100          * and cause a illegal pointer dereference.  This code uses
 101          * get/put_device() to ensure the device structure cannot disappear
 102          * from under our feet.
 103          */
 104         mutex_lock(&deferred_probe_mutex);
 105         while (!list_empty(&deferred_probe_active_list)) {
 106                 private = list_first_entry(&deferred_probe_active_list,
 107                                         typeof(*dev->p), deferred_probe);
 108                 dev = private->device;
 109                 list_del_init(&private->deferred_probe);
 110
 111                 get_device(dev);
 112
 113                 /*
 114                  * Drop the mutex while probing each device; the probe path may
 115                  * manipulate the deferred list
 116                  */
 117                 mutex_unlock(&deferred_probe_mutex);
 118
 119                 /*
 120                  * Force the device to the end of the dpm_list since
 121                  * the PM code assumes that the order we add things to
 122                  * the list is a good order for suspend but deferred
 123                  * probe makes that very unsafe.
 124                  */
 125                 device_pm_lock();
 126                 device_pm_move_last(dev);
 127                 device_pm_unlock();
 128
 129                 dev_dbg(dev, "Retrying from deferred list\n");
 130                 if (initcall_debug && !initcalls_done)
 131                         deferred_probe_debug(dev);
 132                 else
 133                         bus_probe_device(dev);
 134
 135                 mutex_lock(&deferred_probe_mutex);
 136
 137                 put_device(dev);
 138         }
 139         mutex_unlock(&deferred_probe_mutex);
 140 }
 141 static DECLARE_WORK(deferred_probe_work, deferred_probe_work_func);
 142
 143 static void driver_deferred_probe_add(struct device *dev)
 144 {
 145         mutex_lock(&deferred_probe_mutex);
 146         if (list_empty(&dev->p->deferred_probe)) {
 147                 dev_dbg(dev, "Added to deferred list\n");
 148                 list_add_tail(&dev->p->deferred_probe, &deferred_probe_pending_list);
 149         }
 150         mutex_unlock(&deferred_probe_mutex);
 151 }
 152
 153 void driver_deferred_probe_del(struct device *dev)
 154 {
 155         mutex_lock(&deferred_probe_mutex);
 156         if (!list_empty(&dev->p->deferred_probe)) {
 157                 dev_dbg(dev, "Removed from deferred list\n");
 158                 list_del_init(&dev->p->deferred_probe);
 159         }
 160         mutex_unlock(&deferred_probe_mutex);
 161 }
 162
 163 static bool driver_deferred_probe_enable = false;
 164 /**
 165  * driver_deferred_probe_trigger() - Kick off re-probing deferred devices
 166  *
 167  * This functions moves all devices from the pending list to the active
 168  * list and schedules the deferred probe workqueue to process them.  It
 169  * should be called anytime a driver is successfully bound to a device.
 170  *
 171  * Note, there is a race condition in multi-threaded probe. In the case where
 172  * more than one device is probing at the same time, it is possible for one
 173  * probe to complete successfully while another is about to defer. If the second
 174  * depends on the first, then it will get put on the pending list after the
 175  * trigger event has already occurred and will be stuck there.
 176  *
 177  * The atomic 'deferred_trigger_count' is used to determine if a successful
 178  * trigger has occurred in the midst of probing a driver. If the trigger count
 179  * changes in the midst of a probe, then deferred processing should be triggered
 180  * again.
 181  */
 182 static void driver_deferred_probe_trigger(void)
 183 {
 184         if (!driver_deferred_probe_enable)
 185                 return;
 186
 187         /*
 188          * A successful probe means that all the devices in the pending list
 189          * should be triggered to be reprobed.  Move all the deferred devices
 190          * into the active list so they can be retried by the workqueue
 191          */
 192         mutex_lock(&deferred_probe_mutex);
 193         atomic_inc(&deferred_trigger_count);
 194         list_splice_tail_init(&deferred_probe_pending_list,
 195                               &deferred_probe_active_list);
 196         mutex_unlock(&deferred_probe_mutex);
 197
 198         /*
 199          * Kick the re-probe thread.  It may already be scheduled, but it is
 200          * safe to kick it again.
 201          */
 202         schedule_work(&deferred_probe_work);
 203 }
 204
 205 /**
 206  * device_block_probing() - Block/defere device's probes
 207  *
 208  *      It will disable probing of devices and defer their probes instead.
 209  */
 210 void device_block_probing(void)
 211 {
 212         defer_all_probes = true;
 213         /* sync with probes to avoid races. */
 214         wait_for_device_probe();
 215 }
 216
 217 /**
 218  * device_unblock_probing() - Unblock/enable device's probes
 219  *
 220  *      It will restore normal behavior and trigger re-probing of deferred
 221  * devices.
 222  */
 223 void device_unblock_probing(void)
 224 {
 225         defer_all_probes = false;
 226         driver_deferred_probe_trigger();
 227 }
 228
 229 /**
 230  * deferred_probe_initcall() - Enable probing of deferred devices
 231  *
 232  * We don't want to get in the way when the bulk of drivers are getting probed.
 233  * Instead, this initcall makes sure that deferred probing is delayed until
 234  * late_initcall time.
 235  */
 236 static int deferred_probe_initcall(void)
 237 {
 238         driver_deferred_probe_enable = true;
 239         driver_deferred_probe_trigger();
 240         /* Sort as many dependencies as possible before exiting initcalls */
 241         flush_work(&deferred_probe_work);
 242         initcalls_done = true;
 243         return 0;
 244 }
 245 late_initcall(deferred_probe_initcall);
 246
 247 /**
 248  * device_is_bound() - Check if device is bound to a driver
 249  * @dev: device to check
 250  *
 251  * Returns true if passed device has already finished probing successfully
 252  * against a driver.
 253  *
 254  * This function must be called with the device lock held.
 255  */
 256 bool device_is_bound(struct device *dev)
 257 {
 258         return dev->p && klist_node_attached(&dev->p->knode_driver);
 259 }
 260
 261 static void driver_bound(struct device *dev)
 262 {
 263         if (device_is_bound(dev)) {
 264                 printk(KERN_WARNING "%s: device %s already bound\n",
 265                         __func__, kobject_name(&dev->kobj));
 266                 return;
 267         }
 268
 269         pr_debug("driver: '%s': %s: bound to device '%s'\n", dev->driver->name,
 270                  __func__, dev_name(dev));
 271
 272         klist_add_tail(&dev->p->knode_driver, &dev->driver->p->klist_devices);
 273         device_links_driver_bound(dev);
 274
 275         device_pm_check_callbacks(dev);
 276
 277         /*
 278          * Make sure the device is no longer in one of the deferred lists and
 279          * kick off retrying all pending devices
 280          */
 281         driver_deferred_probe_del(dev);
 282         driver_deferred_probe_trigger();
 283
 284         if (dev->bus)
 285                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 286                                              BUS_NOTIFY_BOUND_DRIVER, dev);
 287
 288         kobject_uevent(&dev->kobj, KOBJ_BIND);
 289 }
 290
 291 static ssize_t coredump_store(struct device *dev, struct device_attribute *attr,
 292                             const char *buf, size_t count)
 293 {
 294         device_lock(dev);
 295         if (dev->driver->coredump)
 296                 dev->driver->coredump(dev);
 297         device_unlock(dev);
 298
 299         return count;
 300 }
 301 static DEVICE_ATTR_WO(coredump);
 302
 303 static int driver_sysfs_add(struct device *dev)
 304 {
 305         int ret;
 306
 307         if (dev->bus)
 308                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 309                                              BUS_NOTIFY_BIND_DRIVER, dev);
 310
 311         ret = sysfs_create_link(&dev->driver->p->kobj, &dev->kobj,
 312                                 kobject_name(&dev->kobj));
 313         if (ret)
 314                 goto fail;
 315
 316         ret = sysfs_create_link(&dev->kobj, &dev->driver->p->kobj,
 317                                 "driver");
 318         if (ret)
 319                 goto rm_dev;
 320
 321         if (!IS_ENABLED(CONFIG_DEV_COREDUMP) || !dev->driver->coredump ||
 322             !device_create_file(dev, &dev_attr_coredump))
 323                 return 0;
 324
 325         sysfs_remove_link(&dev->kobj, "driver");
 326
 327 rm_dev:
 328         sysfs_remove_link(&dev->driver->p->kobj,
 329                           kobject_name(&dev->kobj));
 330
 331 fail:
 332         return ret;
 333 }
 334
 335 static void driver_sysfs_remove(struct device *dev)
 336 {
 337         struct device_driver *drv = dev->driver;
 338
 339         if (drv) {
 340                 if (drv->coredump)
 341                         device_remove_file(dev, &dev_attr_coredump);
 342                 sysfs_remove_link(&drv->p->kobj, kobject_name(&dev->kobj));
 343                 sysfs_remove_link(&dev->kobj, "driver");
 344         }
 345 }
 346
 347 /**
 348  * device_bind_driver - bind a driver to one device.
 349  * @dev: device.
 350  *
 351  * Allow manual attachment of a driver to a device.
 352  * Caller must have already set @dev->driver.
 353  *
 354  * Note that this does not modify the bus reference count
 355  * nor take the bus's rwsem. Please verify those are accounted
 356  * for before calling this. (It is ok to call with no other effort
 357  * from a driver's probe() method.)
 358  *
 359  * This function must be called with the device lock held.
 360  */
 361 int device_bind_driver(struct device *dev)
 362 {
 363         int ret;
 364
 365         ret = driver_sysfs_add(dev);
 366         if (!ret)
 367                 driver_bound(dev);
 368         else if (dev->bus)
 369                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 370                                              BUS_NOTIFY_DRIVER_NOT_BOUND, dev);
 371         return ret;
 372 }
 373 EXPORT_SYMBOL_GPL(device_bind_driver);
 374
 375 static atomic_t probe_count = ATOMIC_INIT(0);
 376 static DECLARE_WAIT_QUEUE_HEAD(probe_waitqueue);
 377
 378 static void driver_deferred_probe_add_trigger(struct device *dev,
 379                                               int local_trigger_count)
 380 {
 381         driver_deferred_probe_add(dev);
 382         /* Did a trigger occur while probing? Need to re-trigger if yes */
 383         if (local_trigger_count != atomic_read(&deferred_trigger_count))
 384                 driver_deferred_probe_trigger();
 385 }
 386
 387 static int really_probe(struct device *dev, struct device_driver *drv)
 388 {
 389         int ret = -EPROBE_DEFER;
 390         int local_trigger_count = atomic_read(&deferred_trigger_count);
 391         bool test_remove = IS_ENABLED(CONFIG_DEBUG_TEST_DRIVER_REMOVE) &&
 392                            !drv->suppress_bind_attrs;
 393
 394         if (defer_all_probes) {
 395                 /*
 396                  * Value of defer_all_probes can be set only by
 397                  * device_defer_all_probes_enable() which, in turn, will call
 398                  * wait_for_device_probe() right after that to avoid any races.
 399                  */
 400                 dev_dbg(dev, "Driver %s force probe deferral\n", drv->name);
 401                 driver_deferred_probe_add(dev);
 402                 return ret;
 403         }
 404
 405         ret = device_links_check_suppliers(dev);
 406         if (ret == -EPROBE_DEFER)
 407                 driver_deferred_probe_add_trigger(dev, local_trigger_count);
 408         if (ret)
 409                 return ret;
 410
 411         atomic_inc(&probe_count);
 412         pr_debug("bus: '%s': %s: probing driver %s with device %s\n",
 413                  drv->bus->name, __func__, drv->name, dev_name(dev));
 414         WARN_ON(!list_empty(&dev->devres_head));
 415
 416 re_probe:
 417         dev->driver = drv;
 418
 419         /* If using pinctrl, bind pins now before probing */
 420         ret = pinctrl_bind_pins(dev);
 421         if (ret)
 422                 goto pinctrl_bind_failed;
 423
 424         ret = dma_configure(dev);
 425         if (ret)
 426                 goto dma_failed;
 427
 428         if (driver_sysfs_add(dev)) {
 429                 printk(KERN_ERR "%s: driver_sysfs_add(%s) failed\n",
 430                         __func__, dev_name(dev));
 431                 goto probe_failed;
 432         }
 433
 434         if (dev->pm_domain && dev->pm_domain->activate) {
 435                 ret = dev->pm_domain->activate(dev);
 436                 if (ret)
 437                         goto probe_failed;
 438         }
 439
 440         /*
 441          * Ensure devices are listed in devices_kset in correct order
 442          * It's important to move Dev to the end of devices_kset before
 443          * calling .probe, because it could be recursive and parent Dev
 444          * should always go first
 445          */
 446         devices_kset_move_last(dev);
 447
 448         if (dev->bus->probe) {
 449                 ret = dev->bus->probe(dev);
 450                 if (ret)
 451                         goto probe_failed;
 452         } else if (drv->probe) {
 453                 ret = drv->probe(dev);
 454                 if (ret)
 455                         goto probe_failed;
 456         }
 457
 458         if (test_remove) {
 459                 test_remove = false;
 460
 461                 if (dev->bus->remove)
 462                         dev->bus->remove(dev);
 463                 else if (drv->remove)
 464                         drv->remove(dev);
 465
 466                 devres_release_all(dev);
 467                 driver_sysfs_remove(dev);
 468                 dev->driver = NULL;
 469                 dev_set_drvdata(dev, NULL);
 470                 if (dev->pm_domain && dev->pm_domain->dismiss)
 471                         dev->pm_domain->dismiss(dev);
 472                 pm_runtime_reinit(dev);
 473
 474                 goto re_probe;
 475         }
 476
 477         pinctrl_init_done(dev);
 478
 479         if (dev->pm_domain && dev->pm_domain->sync)
 480                 dev->pm_domain->sync(dev);
 481
 482         driver_bound(dev);
 483         ret = 1;
 484         pr_debug("bus: '%s': %s: bound device %s to driver %s\n",
 485                  drv->bus->name, __func__, dev_name(dev), drv->name);
 486         goto done;
 487
 488 probe_failed:
 489         dma_deconfigure(dev);
 490 dma_failed:
 491         if (dev->bus)
 492                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 493                                              BUS_NOTIFY_DRIVER_NOT_BOUND, dev);
 494 pinctrl_bind_failed:
 495         device_links_no_driver(dev);
 496         devres_release_all(dev);
 497         driver_sysfs_remove(dev);
 498         dev->driver = NULL;
 499         dev_set_drvdata(dev, NULL);
 500         if (dev->pm_domain && dev->pm_domain->dismiss)
 501                 dev->pm_domain->dismiss(dev);
 502         pm_runtime_reinit(dev);
 503         dev_pm_set_driver_flags(dev, 0);
 504
 505         switch (ret) {
 506         case -EPROBE_DEFER:
 507                 /* Driver requested deferred probing */
 508                 dev_dbg(dev, "Driver %s requests probe deferral\n", drv->name);
 509                 driver_deferred_probe_add_trigger(dev, local_trigger_count);
 510                 break;
 511         case -ENODEV:
 512         case -ENXIO:
 513                 pr_debug("%s: probe of %s rejects match %d\n",
 514                          drv->name, dev_name(dev), ret);
 515                 break;
 516         default:
 517                 /* driver matched but the probe failed */
 518                 printk(KERN_WARNING
 519                        "%s: probe of %s failed with error %d\n",
 520                        drv->name, dev_name(dev), ret);
 521         }
 522         /*
 523          * Ignore errors returned by ->probe so that the next driver can try
 524          * its luck.
 525          */
 526         ret = 0;
 527 done:
 528         atomic_dec(&probe_count);
 529         wake_up(&probe_waitqueue);
 530         return ret;
 531 }
 532
 533 /**
 534  * driver_probe_done
 535  * Determine if the probe sequence is finished or not.
 536  *
 537  * Should somehow figure out how to use a semaphore, not an atomic variable...
 538  */
 539 int driver_probe_done(void)
 540 {
 541         pr_debug("%s: probe_count = %d\n", __func__,
 542                  atomic_read(&probe_count));
 543         if (atomic_read(&probe_count))
 544                 return -EBUSY;
 545         return 0;
 546 }
 547
 548 /**
 549  * wait_for_device_probe
 550  * Wait for device probing to be completed.
 551  */
 552 void wait_for_device_probe(void)
 553 {
 554         /* wait for the deferred probe workqueue to finish */
 555         flush_work(&deferred_probe_work);
 556
 557         /* wait for the known devices to complete their probing */
 558         wait_event(probe_waitqueue, atomic_read(&probe_count) == 0);
 559         async_synchronize_full();
 560 }
 561 EXPORT_SYMBOL_GPL(wait_for_device_probe);
 562
 563 /**
 564  * driver_probe_device - attempt to bind device & driver together
 565  * @drv: driver to bind a device to
 566  * @dev: device to try to bind to the driver
 567  *
 568  * This function returns -ENODEV if the device is not registered,
 569  * 1 if the device is bound successfully and 0 otherwise.
 570  *
 571  * This function must be called with @dev lock held.  When called for a
 572  * USB interface, @dev->parent lock must be held as well.
 573  *
 574  * If the device has a parent, runtime-resume the parent before driver probing.
 575  */
 576 int driver_probe_device(struct device_driver *drv, struct device *dev)
 577 {
 578         int ret = 0;
 579
 580         if (!device_is_registered(dev))
 581                 return -ENODEV;
 582
 583         pr_debug("bus: '%s': %s: matched device %s with driver %s\n",
 584                  drv->bus->name, __func__, dev_name(dev), drv->name);
 585
 586         pm_runtime_get_suppliers(dev);
 587         if (dev->parent)
 588                 pm_runtime_get_sync(dev->parent);
 589
 590         pm_runtime_barrier(dev);
 591         ret = really_probe(dev, drv);
 592         pm_request_idle(dev);
 593
 594         if (dev->parent)
 595                 pm_runtime_put(dev->parent);
 596
 597         pm_runtime_put_suppliers(dev);
 598         return ret;
 599 }
 600
 601 bool driver_allows_async_probing(struct device_driver *drv)
 602 {
 603         switch (drv->probe_type) {
 604         case PROBE_PREFER_ASYNCHRONOUS:
 605                 return true;
 606
 607         case PROBE_FORCE_SYNCHRONOUS:
 608                 return false;
 609
 610         default:
 611                 if (module_requested_async_probing(drv->owner))
 612                         return true;
 613
 614                 return false;
 615         }
 616 }
 617
 618 struct device_attach_data {
 619         struct device *dev;
 620
 621         /*
 622          * Indicates whether we are are considering asynchronous probing or
 623          * not. Only initial binding after device or driver registration
 624          * (including deferral processing) may be done asynchronously, the
 625          * rest is always synchronous, as we expect it is being done by
 626          * request from userspace.
 627          */
 628         bool check_async;
 629
 630         /*
 631          * Indicates if we are binding synchronous or asynchronous drivers.
 632          * When asynchronous probing is enabled we'll execute 2 passes
 633          * over drivers: first pass doing synchronous probing and second
 634          * doing asynchronous probing (if synchronous did not succeed -
 635          * most likely because there was no driver requiring synchronous
 636          * probing - and we found asynchronous driver during first pass).
 637          * The 2 passes are done because we can't shoot asynchronous
 638          * probe for given device and driver from bus_for_each_drv() since
 639          * driver pointer is not guaranteed to stay valid once
 640          * bus_for_each_drv() iterates to the next driver on the bus.
 641          */
 642         bool want_async;
 643
 644         /*
 645          * We'll set have_async to 'true' if, while scanning for matching
 646          * driver, we'll encounter one that requests asynchronous probing.
 647          */
 648         bool have_async;
 649 };
 650
 651 static int __device_attach_driver(struct device_driver *drv, void *_data)
 652 {
 653         struct device_attach_data *data = _data;
 654         struct device *dev = data->dev;
 655         bool async_allowed;
 656         int ret;
 657
 658         /*
 659          * Check if device has already been claimed. This may
 660          * happen with driver loading, device discovery/registration,
 661          * and deferred probe processing happens all at once with
 662          * multiple threads.
 663          */
 664         if (dev->driver)
 665                 return -EBUSY;
 666
 667         ret = driver_match_device(drv, dev);
 668         if (ret == 0) {
 669                 /* no match */
 670                 return 0;
 671         } else if (ret == -EPROBE_DEFER) {
 672                 dev_dbg(dev, "Device match requests probe deferral\n");
 673                 driver_deferred_probe_add(dev);
 674         } else if (ret < 0) {
 675                 dev_dbg(dev, "Bus failed to match device: %d", ret);
 676                 return ret;
 677         } /* ret > 0 means positive match */
 678
 679         async_allowed = driver_allows_async_probing(drv);
 680
 681         if (async_allowed)
 682                 data->have_async = true;
 683
 684         if (data->check_async && async_allowed != data->want_async)
 685                 return 0;
 686
 687         return driver_probe_device(drv, dev);
 688 }
 689
 690 static void __device_attach_async_helper(void *_dev, async_cookie_t cookie)
 691 {
 692         struct device *dev = _dev;
 693         struct device_attach_data data = {
 694                 .dev            = dev,
 695                 .check_async    = true,
 696                 .want_async     = true,
 697         };
 698
 699         device_lock(dev);
 700
 701         if (dev->parent)
 702                 pm_runtime_get_sync(dev->parent);
 703
 704         bus_for_each_drv(dev->bus, NULL, &data, __device_attach_driver);
 705         dev_dbg(dev, "async probe completed\n");
 706
 707         pm_request_idle(dev);
 708
 709         if (dev->parent)
 710                 pm_runtime_put(dev->parent);
 711
 712         device_unlock(dev);
 713
 714         put_device(dev);
 715 }
 716
 717 static int __device_attach(struct device *dev, bool allow_async)
 718 {
 719         int ret = 0;
 720
 721         device_lock(dev);
 722         if (dev->driver) {
 723                 if (device_is_bound(dev)) {
 724                         ret = 1;
 725                         goto out_unlock;
 726                 }
 727                 ret = device_bind_driver(dev);
 728                 if (ret == 0)
 729                         ret = 1;
 730                 else {
 731                         dev->driver = NULL;
 732                         ret = 0;
 733                 }
 734         } else {
 735                 struct device_attach_data data = {
 736                         .dev = dev,
 737                         .check_async = allow_async,
 738                         .want_async = false,
 739                 };
 740
 741                 if (dev->parent)
 742                         pm_runtime_get_sync(dev->parent);
 743
 744                 ret = bus_for_each_drv(dev->bus, NULL, &data,
 745                                         __device_attach_driver);
 746                 if (!ret && allow_async && data.have_async) {
 747                         /*
 748                          * If we could not find appropriate driver
 749                          * synchronously and we are allowed to do
 750                          * async probes and there are drivers that
 751                          * want to probe asynchronously, we'll
 752                          * try them.
 753                          */
 754                         dev_dbg(dev, "scheduling asynchronous probe\n");
 755                         get_device(dev);
 756                         async_schedule(__device_attach_async_helper, dev);
 757                 } else {
 758                         pm_request_idle(dev);
 759                 }
 760
 761                 if (dev->parent)
 762                         pm_runtime_put(dev->parent);
 763         }
 764 out_unlock:
 765         device_unlock(dev);
 766         return ret;
 767 }
 768
 769 /**
 770  * device_attach - try to attach device to a driver.
 771  * @dev: device.
 772  *
 773  * Walk the list of drivers that the bus has and call
 774  * driver_probe_device() for each pair. If a compatible
 775  * pair is found, break out and return.
 776  *
 777  * Returns 1 if the device was bound to a driver;
 778  * 0 if no matching driver was found;
 779  * -ENODEV if the device is not registered.
 780  *
 781  * When called for a USB interface, @dev->parent lock must be held.
 782  */
 783 int device_attach(struct device *dev)
 784 {
 785         return __device_attach(dev, false);
 786 }
 787 EXPORT_SYMBOL_GPL(device_attach);
 788
 789 void device_initial_probe(struct device *dev)
 790 {
 791         __device_attach(dev, true);
 792 }
 793
 794 static int __driver_attach(struct device *dev, void *data)
 795 {
 796         struct device_driver *drv = data;
 797         int ret;
 798
 799         /*
 800          * Lock device and try to bind to it. We drop the error
 801          * here and always return 0, because we need to keep trying
 802          * to bind to devices and some drivers will return an error
 803          * simply if it didn't support the device.
 804          *
 805          * driver_probe_device() will spit a warning if there
 806          * is an error.
 807          */
 808
 809         ret = driver_match_device(drv, dev);
 810         if (ret == 0) {
 811                 /* no match */
 812                 return 0;
 813         } else if (ret == -EPROBE_DEFER) {
 814                 dev_dbg(dev, "Device match requests probe deferral\n");
 815                 driver_deferred_probe_add(dev);
 816         } else if (ret < 0) {
 817                 dev_dbg(dev, "Bus failed to match device: %d", ret);
 818                 return ret;
 819         } /* ret > 0 means positive match */
 820
 821         if (dev->parent)        /* Needed for USB */
 822                 device_lock(dev->parent);
 823         device_lock(dev);
 824         if (!dev->driver)
 825                 driver_probe_device(drv, dev);
 826         device_unlock(dev);
 827         if (dev->parent)
 828                 device_unlock(dev->parent);
 829
 830         return 0;
 831 }
 832
 833 /**
 834  * driver_attach - try to bind driver to devices.
 835  * @drv: driver.
 836  *
 837  * Walk the list of devices that the bus has on it and try to
 838  * match the driver with each one.  If driver_probe_device()
 839  * returns 0 and the @dev->driver is set, we've found a
 840  * compatible pair.
 841  */
 842 int driver_attach(struct device_driver *drv)
 843 {
 844         return bus_for_each_dev(drv->bus, NULL, drv, __driver_attach);
 845 }
 846 EXPORT_SYMBOL_GPL(driver_attach);
 847
 848 /*
 849  * __device_release_driver() must be called with @dev lock held.
 850  * When called for a USB interface, @dev->parent lock must be held as well.
 851  */
 852 static void __device_release_driver(struct device *dev, struct device *parent)
 853 {
 854         struct device_driver *drv;
 855
 856         drv = dev->driver;
 857         if (drv) {
 858                 if (driver_allows_async_probing(drv))
 859                         async_synchronize_full();
 860
 861                 while (device_links_busy(dev)) {
 862                         device_unlock(dev);
 863                         if (parent)
 864                                 device_unlock(parent);
 865
 866                         device_links_unbind_consumers(dev);
 867                         if (parent)
 868                                 device_lock(parent);
 869
 870                         device_lock(dev);
 871                         /*
 872                          * A concurrent invocation of the same function might
 873                          * have released the driver successfully while this one
 874                          * was waiting, so check for that.
 875                          */
 876                         if (dev->driver != drv)
 877                                 return;
 878                 }
 879
 880                 pm_runtime_get_sync(dev);
 881                 pm_runtime_clean_up_links(dev);
 882
 883                 driver_sysfs_remove(dev);
 884
 885                 if (dev->bus)
 886                         blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 887                                                      BUS_NOTIFY_UNBIND_DRIVER,
 888                                                      dev);
 889
 890                 pm_runtime_put_sync(dev);
 891
 892                 if (dev->bus && dev->bus->remove)
 893                         dev->bus->remove(dev);
 894                 else if (drv->remove)
 895                         drv->remove(dev);
 896
 897                 device_links_driver_cleanup(dev);
 898                 dma_deconfigure(dev);
 899
 900                 devres_release_all(dev);
 901                 dev->driver = NULL;
 902                 dev_set_drvdata(dev, NULL);
 903                 if (dev->pm_domain && dev->pm_domain->dismiss)
 904                         dev->pm_domain->dismiss(dev);
 905                 pm_runtime_reinit(dev);
 906                 dev_pm_set_driver_flags(dev, 0);
 907
 908                 klist_remove(&dev->p->knode_driver);
 909                 device_pm_check_callbacks(dev);
 910                 if (dev->bus)
 911                         blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 912                                                      BUS_NOTIFY_UNBOUND_DRIVER,
 913                                                      dev);
 914
 915                 kobject_uevent(&dev->kobj, KOBJ_UNBIND);
 916         }
 917 }
 918
 919 void device_release_driver_internal(struct device *dev,
 920                                     struct device_driver *drv,
 921                                     struct device *parent)
 922 {
 923         if (parent)
 924                 device_lock(parent);
 925
 926         device_lock(dev);
 927         if (!drv || drv == dev->driver)
 928                 __device_release_driver(dev, parent);
 929
 930         device_unlock(dev);
 931         if (parent)
 932                 device_unlock(parent);
 933 }
 934
 935 /**
 936  * device_release_driver - manually detach device from driver.
 937  * @dev: device.
 938  *
 939  * Manually detach device from driver.
 940  * When called for a USB interface, @dev->parent lock must be held.
 941  *
 942  * If this function is to be called with @dev->parent lock held, ensure that
 943  * the device's consumers are unbound in advance or that their locks can be
 944  * acquired under the @dev->parent lock.
 945  */
 946 void device_release_driver(struct device *dev)
 947 {
 948         /*
 949          * If anyone calls device_release_driver() recursively from
 950          * within their ->remove callback for the same device, they
 951          * will deadlock right here.
 952          */
 953         device_release_driver_internal(dev, NULL, NULL);
 954 }
 955 EXPORT_SYMBOL_GPL(device_release_driver);
 956
 957 /**
 958  * driver_detach - detach driver from all devices it controls.
 959  * @drv: driver.
 960  */
 961 void driver_detach(struct device_driver *drv)
 962 {
 963         struct device_private *dev_prv;
 964         struct device *dev;
 965
 966         for (;;) {
 967                 spin_lock(&drv->p->klist_devices.k_lock);
 968                 if (list_empty(&drv->p->klist_devices.k_list)) {
 969                         spin_unlock(&drv->p->klist_devices.k_lock);
 970                         break;
 971                 }
 972                 dev_prv = list_entry(drv->p->klist_devices.k_list.prev,
 973                                      struct device_private,
 974                                      knode_driver.n_node);
 975                 dev = dev_prv->device;
 976                 get_device(dev);
 977                 spin_unlock(&drv->p->klist_devices.k_lock);
 978                 device_release_driver_internal(dev, drv, dev->parent);
 979                 put_device(dev);
 980         }
 981 }