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