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 <[email protected]>
  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         /*
 438          * Ensure devices are listed in devices_kset in correct order
 439          * It's important to move Dev to the end of devices_kset before
 440          * calling .probe, because it could be recursive and parent Dev
 441          * should always go first
 442          */
 443         devices_kset_move_last(dev);
 444
 445         if (dev->bus->probe) {
 446                 ret = dev->bus->probe(dev);
 447                 if (ret)
 448                         goto probe_failed;
 449         } else if (drv->probe) {
 450                 ret = drv->probe(dev);
 451                 if (ret)
 452                         goto probe_failed;
 453         }
 454
 455         if (test_remove) {
 456                 test_remove = false;
 457
 458                 if (dev->bus->remove)
 459                         dev->bus->remove(dev);
 460                 else if (drv->remove)
 461                         drv->remove(dev);
 462
 463                 devres_release_all(dev);
 464                 driver_sysfs_remove(dev);
 465                 dev->driver = NULL;
 466                 dev_set_drvdata(dev, NULL);
 467                 if (dev->pm_domain && dev->pm_domain->dismiss)
 468                         dev->pm_domain->dismiss(dev);
 469                 pm_runtime_reinit(dev);
 470
 471                 goto re_probe;
 472         }
 473
 474         pinctrl_init_done(dev);
 475
 476         if (dev->pm_domain && dev->pm_domain->sync)
 477                 dev->pm_domain->sync(dev);
 478
 479         driver_bound(dev);
 480         ret = 1;
 481         pr_debug("bus: '%s': %s: bound device %s to driver %s\n",
 482                  drv->bus->name, __func__, dev_name(dev), drv->name);
 483         goto done;
 484
 485 probe_failed:
 486         dma_deconfigure(dev);
 487 dma_failed:
 488         if (dev->bus)
 489                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 490                                              BUS_NOTIFY_DRIVER_NOT_BOUND, dev);
 491 pinctrl_bind_failed:
 492         device_links_no_driver(dev);
 493         devres_release_all(dev);
 494         driver_sysfs_remove(dev);
 495         dev->driver = NULL;
 496         dev_set_drvdata(dev, NULL);
 497         if (dev->pm_domain && dev->pm_domain->dismiss)
 498                 dev->pm_domain->dismiss(dev);
 499         pm_runtime_reinit(dev);
 500         dev_pm_set_driver_flags(dev, 0);
 501
 502         switch (ret) {
 503         case -EPROBE_DEFER:
 504                 /* Driver requested deferred probing */
 505                 dev_dbg(dev, "Driver %s requests probe deferral\n", drv->name);
 506                 driver_deferred_probe_add_trigger(dev, local_trigger_count);
 507                 break;
 508         case -ENODEV:
 509         case -ENXIO:
 510                 pr_debug("%s: probe of %s rejects match %d\n",
 511                          drv->name, dev_name(dev), ret);
 512                 break;
 513         default:
 514                 /* driver matched but the probe failed */
 515                 printk(KERN_WARNING
 516                        "%s: probe of %s failed with error %d\n",
 517                        drv->name, dev_name(dev), ret);
 518         }
 519         /*
 520          * Ignore errors returned by ->probe so that the next driver can try
 521          * its luck.
 522          */
 523         ret = 0;
 524 done:
 525         atomic_dec(&probe_count);
 526         wake_up(&probe_waitqueue);
 527         return ret;
 528 }
 529
 530 /**
 531  * driver_probe_done
 532  * Determine if the probe sequence is finished or not.
 533  *
 534  * Should somehow figure out how to use a semaphore, not an atomic variable...
 535  */
 536 int driver_probe_done(void)
 537 {
 538         pr_debug("%s: probe_count = %d\n", __func__,
 539                  atomic_read(&probe_count));
 540         if (atomic_read(&probe_count))
 541                 return -EBUSY;
 542         return 0;
 543 }
 544
 545 /**
 546  * wait_for_device_probe
 547  * Wait for device probing to be completed.
 548  */
 549 void wait_for_device_probe(void)
 550 {
 551         /* wait for the deferred probe workqueue to finish */
 552         flush_work(&deferred_probe_work);
 553
 554         /* wait for the known devices to complete their probing */
 555         wait_event(probe_waitqueue, atomic_read(&probe_count) == 0);
 556         async_synchronize_full();
 557 }
 558 EXPORT_SYMBOL_GPL(wait_for_device_probe);
 559
 560 /**
 561  * driver_probe_device - attempt to bind device & driver together
 562  * @drv: driver to bind a device to
 563  * @dev: device to try to bind to the driver
 564  *
 565  * This function returns -ENODEV if the device is not registered,
 566  * 1 if the device is bound successfully and 0 otherwise.
 567  *
 568  * This function must be called with @dev lock held.  When called for a
 569  * USB interface, @dev->parent lock must be held as well.
 570  *
 571  * If the device has a parent, runtime-resume the parent before driver probing.
 572  */
 573 int driver_probe_device(struct device_driver *drv, struct device *dev)
 574 {
 575         int ret = 0;
 576
 577         if (!device_is_registered(dev))
 578                 return -ENODEV;
 579
 580         pr_debug("bus: '%s': %s: matched device %s with driver %s\n",
 581                  drv->bus->name, __func__, dev_name(dev), drv->name);
 582
 583         pm_runtime_resume_suppliers(dev);
 584         if (dev->parent)
 585                 pm_runtime_get_sync(dev->parent);
 586
 587         pm_runtime_barrier(dev);
 588         ret = really_probe(dev, drv);
 589         pm_request_idle(dev);
 590
 591         if (dev->parent)
 592                 pm_runtime_put(dev->parent);
 593
 594         return ret;
 595 }
 596
 597 bool driver_allows_async_probing(struct device_driver *drv)
 598 {
 599         switch (drv->probe_type) {
 600         case PROBE_PREFER_ASYNCHRONOUS:
 601                 return true;
 602
 603         case PROBE_FORCE_SYNCHRONOUS:
 604                 return false;
 605
 606         default:
 607                 if (module_requested_async_probing(drv->owner))
 608                         return true;
 609
 610                 return false;
 611         }
 612 }
 613
 614 struct device_attach_data {
 615         struct device *dev;
 616
 617         /*
 618          * Indicates whether we are are considering asynchronous probing or
 619          * not. Only initial binding after device or driver registration
 620          * (including deferral processing) may be done asynchronously, the
 621          * rest is always synchronous, as we expect it is being done by
 622          * request from userspace.
 623          */
 624         bool check_async;
 625
 626         /*
 627          * Indicates if we are binding synchronous or asynchronous drivers.
 628          * When asynchronous probing is enabled we'll execute 2 passes
 629          * over drivers: first pass doing synchronous probing and second
 630          * doing asynchronous probing (if synchronous did not succeed -
 631          * most likely because there was no driver requiring synchronous
 632          * probing - and we found asynchronous driver during first pass).
 633          * The 2 passes are done because we can't shoot asynchronous
 634          * probe for given device and driver from bus_for_each_drv() since
 635          * driver pointer is not guaranteed to stay valid once
 636          * bus_for_each_drv() iterates to the next driver on the bus.
 637          */
 638         bool want_async;
 639
 640         /*
 641          * We'll set have_async to 'true' if, while scanning for matching
 642          * driver, we'll encounter one that requests asynchronous probing.
 643          */
 644         bool have_async;
 645 };
 646
 647 static int __device_attach_driver(struct device_driver *drv, void *_data)
 648 {
 649         struct device_attach_data *data = _data;
 650         struct device *dev = data->dev;
 651         bool async_allowed;
 652         int ret;
 653
 654         /*
 655          * Check if device has already been claimed. This may
 656          * happen with driver loading, device discovery/registration,
 657          * and deferred probe processing happens all at once with
 658          * multiple threads.
 659          */
 660         if (dev->driver)
 661                 return -EBUSY;
 662
 663         ret = driver_match_device(drv, dev);
 664         if (ret == 0) {
 665                 /* no match */
 666                 return 0;
 667         } else if (ret == -EPROBE_DEFER) {
 668                 dev_dbg(dev, "Device match requests probe deferral\n");
 669                 driver_deferred_probe_add(dev);
 670         } else if (ret < 0) {
 671                 dev_dbg(dev, "Bus failed to match device: %d", ret);
 672                 return ret;
 673         } /* ret > 0 means positive match */
 674
 675         async_allowed = driver_allows_async_probing(drv);
 676
 677         if (async_allowed)
 678                 data->have_async = true;
 679
 680         if (data->check_async && async_allowed != data->want_async)
 681                 return 0;
 682
 683         return driver_probe_device(drv, dev);
 684 }
 685
 686 static void __device_attach_async_helper(void *_dev, async_cookie_t cookie)
 687 {
 688         struct device *dev = _dev;
 689         struct device_attach_data data = {
 690                 .dev            = dev,
 691                 .check_async    = true,
 692                 .want_async     = true,
 693         };
 694
 695         device_lock(dev);
 696
 697         if (dev->parent)
 698                 pm_runtime_get_sync(dev->parent);
 699
 700         bus_for_each_drv(dev->bus, NULL, &data, __device_attach_driver);
 701         dev_dbg(dev, "async probe completed\n");
 702
 703         pm_request_idle(dev);
 704
 705         if (dev->parent)
 706                 pm_runtime_put(dev->parent);
 707
 708         device_unlock(dev);
 709
 710         put_device(dev);
 711 }
 712
 713 static int __device_attach(struct device *dev, bool allow_async)
 714 {
 715         int ret = 0;
 716
 717         device_lock(dev);
 718         if (dev->driver) {
 719                 if (device_is_bound(dev)) {
 720                         ret = 1;
 721                         goto out_unlock;
 722                 }
 723                 ret = device_bind_driver(dev);
 724                 if (ret == 0)
 725                         ret = 1;
 726                 else {
 727                         dev->driver = NULL;
 728                         ret = 0;
 729                 }
 730         } else {
 731                 struct device_attach_data data = {
 732                         .dev = dev,
 733                         .check_async = allow_async,
 734                         .want_async = false,
 735                 };
 736
 737                 if (dev->parent)
 738                         pm_runtime_get_sync(dev->parent);
 739
 740                 ret = bus_for_each_drv(dev->bus, NULL, &data,
 741                                         __device_attach_driver);
 742                 if (!ret && allow_async && data.have_async) {
 743                         /*
 744                          * If we could not find appropriate driver
 745                          * synchronously and we are allowed to do
 746                          * async probes and there are drivers that
 747                          * want to probe asynchronously, we'll
 748                          * try them.
 749                          */
 750                         dev_dbg(dev, "scheduling asynchronous probe\n");
 751                         get_device(dev);
 752                         async_schedule(__device_attach_async_helper, dev);
 753                 } else {
 754                         pm_request_idle(dev);
 755                 }
 756
 757                 if (dev->parent)
 758                         pm_runtime_put(dev->parent);
 759         }
 760 out_unlock:
 761         device_unlock(dev);
 762         return ret;
 763 }
 764
 765 /**
 766  * device_attach - try to attach device to a driver.
 767  * @dev: device.
 768  *
 769  * Walk the list of drivers that the bus has and call
 770  * driver_probe_device() for each pair. If a compatible
 771  * pair is found, break out and return.
 772  *
 773  * Returns 1 if the device was bound to a driver;
 774  * 0 if no matching driver was found;
 775  * -ENODEV if the device is not registered.
 776  *
 777  * When called for a USB interface, @dev->parent lock must be held.
 778  */
 779 int device_attach(struct device *dev)
 780 {
 781         return __device_attach(dev, false);
 782 }
 783 EXPORT_SYMBOL_GPL(device_attach);
 784
 785 void device_initial_probe(struct device *dev)
 786 {
 787         __device_attach(dev, true);
 788 }
 789
 790 static int __driver_attach(struct device *dev, void *data)
 791 {
 792         struct device_driver *drv = data;
 793         int ret;
 794
 795         /*
 796          * Lock device and try to bind to it. We drop the error
 797          * here and always return 0, because we need to keep trying
 798          * to bind to devices and some drivers will return an error
 799          * simply if it didn't support the device.
 800          *
 801          * driver_probe_device() will spit a warning if there
 802          * is an error.
 803          */
 804
 805         ret = driver_match_device(drv, dev);
 806         if (ret == 0) {
 807                 /* no match */
 808                 return 0;
 809         } else if (ret == -EPROBE_DEFER) {
 810                 dev_dbg(dev, "Device match requests probe deferral\n");
 811                 driver_deferred_probe_add(dev);
 812         } else if (ret < 0) {
 813                 dev_dbg(dev, "Bus failed to match device: %d", ret);
 814                 return ret;
 815         } /* ret > 0 means positive match */
 816
 817         if (dev->parent && dev->bus->need_parent_lock)
 818                 device_lock(dev->parent);
 819         device_lock(dev);
 820         if (!dev->driver)
 821                 driver_probe_device(drv, dev);
 822         device_unlock(dev);
 823         if (dev->parent && dev->bus->need_parent_lock)
 824                 device_unlock(dev->parent);
 825
 826         return 0;
 827 }
 828
 829 /**
 830  * driver_attach - try to bind driver to devices.
 831  * @drv: driver.
 832  *
 833  * Walk the list of devices that the bus has on it and try to
 834  * match the driver with each one.  If driver_probe_device()
 835  * returns 0 and the @dev->driver is set, we've found a
 836  * compatible pair.
 837  */
 838 int driver_attach(struct device_driver *drv)
 839 {
 840         return bus_for_each_dev(drv->bus, NULL, drv, __driver_attach);
 841 }
 842 EXPORT_SYMBOL_GPL(driver_attach);
 843
 844 /*
 845  * __device_release_driver() must be called with @dev lock held.
 846  * When called for a USB interface, @dev->parent lock must be held as well.
 847  */
 848 static void __device_release_driver(struct device *dev, struct device *parent)
 849 {
 850         struct device_driver *drv;
 851
 852         drv = dev->driver;
 853         if (drv) {
 854                 if (driver_allows_async_probing(drv))
 855                         async_synchronize_full();
 856
 857                 while (device_links_busy(dev)) {
 858                         device_unlock(dev);
 859                         if (parent)
 860                                 device_unlock(parent);
 861
 862                         device_links_unbind_consumers(dev);
 863                         if (parent)
 864                                 device_lock(parent);
 865
 866                         device_lock(dev);
 867                         /*
 868                          * A concurrent invocation of the same function might
 869                          * have released the driver successfully while this one
 870                          * was waiting, so check for that.
 871                          */
 872                         if (dev->driver != drv)
 873                                 return;
 874                 }
 875
 876                 pm_runtime_get_sync(dev);
 877                 pm_runtime_clean_up_links(dev);
 878
 879                 driver_sysfs_remove(dev);
 880
 881                 if (dev->bus)
 882                         blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 883                                                      BUS_NOTIFY_UNBIND_DRIVER,
 884                                                      dev);
 885
 886                 pm_runtime_put_sync(dev);
 887
 888                 if (dev->bus && dev->bus->remove)
 889                         dev->bus->remove(dev);
 890                 else if (drv->remove)
 891                         drv->remove(dev);
 892
 893                 device_links_driver_cleanup(dev);
 894                 dma_deconfigure(dev);
 895
 896                 devres_release_all(dev);
 897                 dev->driver = NULL;
 898                 dev_set_drvdata(dev, NULL);
 899                 if (dev->pm_domain && dev->pm_domain->dismiss)
 900                         dev->pm_domain->dismiss(dev);
 901                 pm_runtime_reinit(dev);
 902                 dev_pm_set_driver_flags(dev, 0);
 903
 904                 klist_remove(&dev->p->knode_driver);
 905                 device_pm_check_callbacks(dev);
 906                 if (dev->bus)
 907                         blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 908                                                      BUS_NOTIFY_UNBOUND_DRIVER,
 909                                                      dev);
 910
 911                 kobject_uevent(&dev->kobj, KOBJ_UNBIND);
 912         }
 913 }
 914
 915 void device_release_driver_internal(struct device *dev,
 916                                     struct device_driver *drv,
 917                                     struct device *parent)
 918 {
 919         if (parent && dev->bus->need_parent_lock)
 920                 device_lock(parent);
 921
 922         device_lock(dev);
 923         if (!drv || drv == dev->driver)
 924                 __device_release_driver(dev, parent);
 925
 926         device_unlock(dev);
 927         if (parent && dev->bus->need_parent_lock)
 928                 device_unlock(parent);
 929 }
 930
 931 /**
 932  * device_release_driver - manually detach device from driver.
 933  * @dev: device.
 934  *
 935  * Manually detach device from driver.
 936  * When called for a USB interface, @dev->parent lock must be held.
 937  *
 938  * If this function is to be called with @dev->parent lock held, ensure that
 939  * the device's consumers are unbound in advance or that their locks can be
 940  * acquired under the @dev->parent lock.
 941  */
 942 void device_release_driver(struct device *dev)
 943 {
 944         /*
 945          * If anyone calls device_release_driver() recursively from
 946          * within their ->remove callback for the same device, they
 947          * will deadlock right here.
 948          */
 949         device_release_driver_internal(dev, NULL, NULL);
 950 }
 951 EXPORT_SYMBOL_GPL(device_release_driver);
 952
 953 /**
 954  * driver_detach - detach driver from all devices it controls.
 955  * @drv: driver.
 956  */
 957 void driver_detach(struct device_driver *drv)
 958 {
 959         struct device_private *dev_prv;
 960         struct device *dev;
 961
 962         for (;;) {
 963                 spin_lock(&drv->p->klist_devices.k_lock);
 964                 if (list_empty(&drv->p->klist_devices.k_list)) {
 965                         spin_unlock(&drv->p->klist_devices.k_lock);
 966                         break;
 967                 }
 968                 dev_prv = list_entry(drv->p->klist_devices.k_list.prev,
 969                                      struct device_private,
 970                                      knode_driver.n_node);
 971                 dev = dev_prv->device;
 972                 get_device(dev);
 973                 spin_unlock(&drv->p->klist_devices.k_lock);
 974                 device_release_driver_internal(dev, drv, dev->parent);
 975                 put_device(dev);
 976         }
 977 }