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/debugfs.h>
  20 #include <linux/device.h>
  21 #include <linux/delay.h>
  22 #include <linux/dma-mapping.h>
  23 #include <linux/init.h>
  24 #include <linux/module.h>
  25 #include <linux/kthread.h>
  26 #include <linux/wait.h>
  27 #include <linux/async.h>
  28 #include <linux/pm_runtime.h>
  29 #include <linux/pinctrl/devinfo.h>
  30
  31 #include "base.h"
  32 #include "power/power.h"
  33
  34 /*
  35  * Deferred Probe infrastructure.
  36  *
  37  * Sometimes driver probe order matters, but the kernel doesn't always have
  38  * dependency information which means some drivers will get probed before a
  39  * resource it depends on is available.  For example, an SDHCI driver may
  40  * first need a GPIO line from an i2c GPIO controller before it can be
  41  * initialized.  If a required resource is not available yet, a driver can
  42  * request probing to be deferred by returning -EPROBE_DEFER from its probe hook
  43  *
  44  * Deferred probe maintains two lists of devices, a pending list and an active
  45  * list.  A driver returning -EPROBE_DEFER causes the device to be added to the
  46  * pending list.  A successful driver probe will trigger moving all devices
  47  * from the pending to the active list so that the workqueue will eventually
  48  * retry them.
  49  *
  50  * The deferred_probe_mutex must be held any time the deferred_probe_*_list
  51  * of the (struct device*)->p->deferred_probe pointers are manipulated
  52  */
  53 static DEFINE_MUTEX(deferred_probe_mutex);
  54 static LIST_HEAD(deferred_probe_pending_list);
  55 static LIST_HEAD(deferred_probe_active_list);
  56 static atomic_t deferred_trigger_count = ATOMIC_INIT(0);
  57 static struct dentry *deferred_devices;
  58 static bool initcalls_done;
  59
  60 /* Save the async probe drivers' name from kernel cmdline */
  61 #define ASYNC_DRV_NAMES_MAX_LEN 256
  62 static char async_probe_drv_names[ASYNC_DRV_NAMES_MAX_LEN];
  63
  64 /*
  65  * In some cases, like suspend to RAM or hibernation, It might be reasonable
  66  * to prohibit probing of devices as it could be unsafe.
  67  * Once defer_all_probes is true all drivers probes will be forcibly deferred.
  68  */
  69 static bool defer_all_probes;
  70
  71 /*
  72  * deferred_probe_work_func() - Retry probing devices in the active list.
  73  */
  74 static void deferred_probe_work_func(struct work_struct *work)
  75 {
  76         struct device *dev;
  77         struct device_private *private;
  78         /*
  79          * This block processes every device in the deferred 'active' list.
  80          * Each device is removed from the active list and passed to
  81          * bus_probe_device() to re-attempt the probe.  The loop continues
  82          * until every device in the active list is removed and retried.
  83          *
  84          * Note: Once the device is removed from the list and the mutex is
  85          * released, it is possible for the device get freed by another thread
  86          * and cause a illegal pointer dereference.  This code uses
  87          * get/put_device() to ensure the device structure cannot disappear
  88          * from under our feet.
  89          */
  90         mutex_lock(&deferred_probe_mutex);
  91         while (!list_empty(&deferred_probe_active_list)) {
  92                 private = list_first_entry(&deferred_probe_active_list,
  93                                         typeof(*dev->p), deferred_probe);
  94                 dev = private->device;
  95                 list_del_init(&private->deferred_probe);
  96
  97                 get_device(dev);
  98
  99                 /*
 100                  * Drop the mutex while probing each device; the probe path may
 101                  * manipulate the deferred list
 102                  */
 103                 mutex_unlock(&deferred_probe_mutex);
 104
 105                 /*
 106                  * Force the device to the end of the dpm_list since
 107                  * the PM code assumes that the order we add things to
 108                  * the list is a good order for suspend but deferred
 109                  * probe makes that very unsafe.
 110                  */
 111                 device_pm_move_to_tail(dev);
 112
 113                 dev_dbg(dev, "Retrying from deferred list\n");
 114                 bus_probe_device(dev);
 115                 mutex_lock(&deferred_probe_mutex);
 116
 117                 put_device(dev);
 118         }
 119         mutex_unlock(&deferred_probe_mutex);
 120 }
 121 static DECLARE_WORK(deferred_probe_work, deferred_probe_work_func);
 122
 123 void driver_deferred_probe_add(struct device *dev)
 124 {
 125         mutex_lock(&deferred_probe_mutex);
 126         if (list_empty(&dev->p->deferred_probe)) {
 127                 dev_dbg(dev, "Added to deferred list\n");
 128                 list_add_tail(&dev->p->deferred_probe, &deferred_probe_pending_list);
 129         }
 130         mutex_unlock(&deferred_probe_mutex);
 131 }
 132
 133 void driver_deferred_probe_del(struct device *dev)
 134 {
 135         mutex_lock(&deferred_probe_mutex);
 136         if (!list_empty(&dev->p->deferred_probe)) {
 137                 dev_dbg(dev, "Removed from deferred list\n");
 138                 list_del_init(&dev->p->deferred_probe);
 139         }
 140         mutex_unlock(&deferred_probe_mutex);
 141 }
 142
 143 static bool driver_deferred_probe_enable = false;
 144 /**
 145  * driver_deferred_probe_trigger() - Kick off re-probing deferred devices
 146  *
 147  * This functions moves all devices from the pending list to the active
 148  * list and schedules the deferred probe workqueue to process them.  It
 149  * should be called anytime a driver is successfully bound to a device.
 150  *
 151  * Note, there is a race condition in multi-threaded probe. In the case where
 152  * more than one device is probing at the same time, it is possible for one
 153  * probe to complete successfully while another is about to defer. If the second
 154  * depends on the first, then it will get put on the pending list after the
 155  * trigger event has already occurred and will be stuck there.
 156  *
 157  * The atomic 'deferred_trigger_count' is used to determine if a successful
 158  * trigger has occurred in the midst of probing a driver. If the trigger count
 159  * changes in the midst of a probe, then deferred processing should be triggered
 160  * again.
 161  */
 162 static void driver_deferred_probe_trigger(void)
 163 {
 164         if (!driver_deferred_probe_enable)
 165                 return;
 166
 167         driver_deferred_probe_force_trigger();
 168 }
 169
 170 void driver_deferred_probe_force_trigger(void)
 171 {
 172         /*
 173          * A successful probe means that all the devices in the pending list
 174          * should be triggered to be reprobed.  Move all the deferred devices
 175          * into the active list so they can be retried by the workqueue
 176          */
 177         mutex_lock(&deferred_probe_mutex);
 178         atomic_inc(&deferred_trigger_count);
 179         list_splice_tail_init(&deferred_probe_pending_list,
 180                               &deferred_probe_active_list);
 181         mutex_unlock(&deferred_probe_mutex);
 182
 183         /*
 184          * Kick the re-probe thread.  It may already be scheduled, but it is
 185          * safe to kick it again.
 186          */
 187         schedule_work(&deferred_probe_work);
 188 }
 189
 190 /**
 191  * device_block_probing() - Block/defer device's probes
 192  *
 193  *      It will disable probing of devices and defer their probes instead.
 194  */
 195 void device_block_probing(void)
 196 {
 197         defer_all_probes = true;
 198         /* sync with probes to avoid races. */
 199         wait_for_device_probe();
 200 }
 201
 202 /**
 203  * device_unblock_probing() - Unblock/enable device's probes
 204  *
 205  *      It will restore normal behavior and trigger re-probing of deferred
 206  * devices.
 207  */
 208 void device_unblock_probing(void)
 209 {
 210         defer_all_probes = false;
 211         driver_deferred_probe_trigger();
 212 }
 213
 214 /*
 215  * deferred_devs_show() - Show the devices in the deferred probe pending list.
 216  */
 217 static int deferred_devs_show(struct seq_file *s, void *data)
 218 {
 219         struct device_private *curr;
 220
 221         mutex_lock(&deferred_probe_mutex);
 222
 223         list_for_each_entry(curr, &deferred_probe_pending_list, deferred_probe)
 224                 seq_printf(s, "%s\n", dev_name(curr->device));
 225
 226         mutex_unlock(&deferred_probe_mutex);
 227
 228         return 0;
 229 }
 230 DEFINE_SHOW_ATTRIBUTE(deferred_devs);
 231
 232 int driver_deferred_probe_timeout;
 233 EXPORT_SYMBOL_GPL(driver_deferred_probe_timeout);
 234 static DECLARE_WAIT_QUEUE_HEAD(probe_timeout_waitqueue);
 235
 236 static int __init deferred_probe_timeout_setup(char *str)
 237 {
 238         int timeout;
 239
 240         if (!kstrtoint(str, 10, &timeout))
 241                 driver_deferred_probe_timeout = timeout;
 242         return 1;
 243 }
 244 __setup("deferred_probe_timeout=", deferred_probe_timeout_setup);
 245
 246 /**
 247  * driver_deferred_probe_check_state() - Check deferred probe state
 248  * @dev: device to check
 249  *
 250  * Return:
 251  * -ENODEV if initcalls have completed and modules are disabled.
 252  * -ETIMEDOUT if the deferred probe timeout was set and has expired
 253  *  and modules are enabled.
 254  * -EPROBE_DEFER in other cases.
 255  *
 256  * Drivers or subsystems can opt-in to calling this function instead of directly
 257  * returning -EPROBE_DEFER.
 258  */
 259 int driver_deferred_probe_check_state(struct device *dev)
 260 {
 261         if (!IS_ENABLED(CONFIG_MODULES) && initcalls_done) {
 262                 dev_warn(dev, "ignoring dependency for device, assuming no driver\n");
 263                 return -ENODEV;
 264         }
 265
 266         if (!driver_deferred_probe_timeout && initcalls_done) {
 267                 dev_warn(dev, "deferred probe timeout, ignoring dependency\n");
 268                 return -ETIMEDOUT;
 269         }
 270
 271         return -EPROBE_DEFER;
 272 }
 273
 274 static void deferred_probe_timeout_work_func(struct work_struct *work)
 275 {
 276         struct device_private *private, *p;
 277
 278         driver_deferred_probe_timeout = 0;
 279         driver_deferred_probe_trigger();
 280         flush_work(&deferred_probe_work);
 281
 282         list_for_each_entry_safe(private, p, &deferred_probe_pending_list, deferred_probe)
 283                 dev_info(private->device, "deferred probe pending\n");
 284         wake_up(&probe_timeout_waitqueue);
 285 }
 286 static DECLARE_DELAYED_WORK(deferred_probe_timeout_work, deferred_probe_timeout_work_func);
 287
 288 /**
 289  * deferred_probe_initcall() - Enable probing of deferred devices
 290  *
 291  * We don't want to get in the way when the bulk of drivers are getting probed.
 292  * Instead, this initcall makes sure that deferred probing is delayed until
 293  * late_initcall time.
 294  */
 295 static int deferred_probe_initcall(void)
 296 {
 297         deferred_devices = debugfs_create_file("devices_deferred", 0444, NULL,
 298                                                NULL, &deferred_devs_fops);
 299
 300         driver_deferred_probe_enable = true;
 301         driver_deferred_probe_trigger();
 302         /* Sort as many dependencies as possible before exiting initcalls */
 303         flush_work(&deferred_probe_work);
 304         initcalls_done = true;
 305
 306         /*
 307          * Trigger deferred probe again, this time we won't defer anything
 308          * that is optional
 309          */
 310         driver_deferred_probe_trigger();
 311         flush_work(&deferred_probe_work);
 312
 313         if (driver_deferred_probe_timeout > 0) {
 314                 schedule_delayed_work(&deferred_probe_timeout_work,
 315                         driver_deferred_probe_timeout * HZ);
 316         }
 317         return 0;
 318 }
 319 late_initcall(deferred_probe_initcall);
 320
 321 static void __exit deferred_probe_exit(void)
 322 {
 323         debugfs_remove_recursive(deferred_devices);
 324 }
 325 __exitcall(deferred_probe_exit);
 326
 327 /**
 328  * device_is_bound() - Check if device is bound to a driver
 329  * @dev: device to check
 330  *
 331  * Returns true if passed device has already finished probing successfully
 332  * against a driver.
 333  *
 334  * This function must be called with the device lock held.
 335  */
 336 bool device_is_bound(struct device *dev)
 337 {
 338         return dev->p && klist_node_attached(&dev->p->knode_driver);
 339 }
 340
 341 static void driver_bound(struct device *dev)
 342 {
 343         if (device_is_bound(dev)) {
 344                 pr_warn("%s: device %s already bound\n",
 345                         __func__, kobject_name(&dev->kobj));
 346                 return;
 347         }
 348
 349         pr_debug("driver: '%s': %s: bound to device '%s'\n", dev->driver->name,
 350                  __func__, dev_name(dev));
 351
 352         klist_add_tail(&dev->p->knode_driver, &dev->driver->p->klist_devices);
 353         device_links_driver_bound(dev);
 354
 355         device_pm_check_callbacks(dev);
 356
 357         /*
 358          * Make sure the device is no longer in one of the deferred lists and
 359          * kick off retrying all pending devices
 360          */
 361         driver_deferred_probe_del(dev);
 362         driver_deferred_probe_trigger();
 363
 364         if (dev->bus)
 365                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 366                                              BUS_NOTIFY_BOUND_DRIVER, dev);
 367
 368         kobject_uevent(&dev->kobj, KOBJ_BIND);
 369 }
 370
 371 static ssize_t coredump_store(struct device *dev, struct device_attribute *attr,
 372                             const char *buf, size_t count)
 373 {
 374         device_lock(dev);
 375         dev->driver->coredump(dev);
 376         device_unlock(dev);
 377
 378         return count;
 379 }
 380 static DEVICE_ATTR_WO(coredump);
 381
 382 static int driver_sysfs_add(struct device *dev)
 383 {
 384         int ret;
 385
 386         if (dev->bus)
 387                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 388                                              BUS_NOTIFY_BIND_DRIVER, dev);
 389
 390         ret = sysfs_create_link(&dev->driver->p->kobj, &dev->kobj,
 391                                 kobject_name(&dev->kobj));
 392         if (ret)
 393                 goto fail;
 394
 395         ret = sysfs_create_link(&dev->kobj, &dev->driver->p->kobj,
 396                                 "driver");
 397         if (ret)
 398                 goto rm_dev;
 399
 400         if (!IS_ENABLED(CONFIG_DEV_COREDUMP) || !dev->driver->coredump ||
 401             !device_create_file(dev, &dev_attr_coredump))
 402                 return 0;
 403
 404         sysfs_remove_link(&dev->kobj, "driver");
 405
 406 rm_dev:
 407         sysfs_remove_link(&dev->driver->p->kobj,
 408                           kobject_name(&dev->kobj));
 409
 410 fail:
 411         return ret;
 412 }
 413
 414 static void driver_sysfs_remove(struct device *dev)
 415 {
 416         struct device_driver *drv = dev->driver;
 417
 418         if (drv) {
 419                 if (drv->coredump)
 420                         device_remove_file(dev, &dev_attr_coredump);
 421                 sysfs_remove_link(&drv->p->kobj, kobject_name(&dev->kobj));
 422                 sysfs_remove_link(&dev->kobj, "driver");
 423         }
 424 }
 425
 426 /**
 427  * device_bind_driver - bind a driver to one device.
 428  * @dev: device.
 429  *
 430  * Allow manual attachment of a driver to a device.
 431  * Caller must have already set @dev->driver.
 432  *
 433  * Note that this does not modify the bus reference count
 434  * nor take the bus's rwsem. Please verify those are accounted
 435  * for before calling this. (It is ok to call with no other effort
 436  * from a driver's probe() method.)
 437  *
 438  * This function must be called with the device lock held.
 439  */
 440 int device_bind_driver(struct device *dev)
 441 {
 442         int ret;
 443
 444         ret = driver_sysfs_add(dev);
 445         if (!ret)
 446                 driver_bound(dev);
 447         else if (dev->bus)
 448                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 449                                              BUS_NOTIFY_DRIVER_NOT_BOUND, dev);
 450         return ret;
 451 }
 452 EXPORT_SYMBOL_GPL(device_bind_driver);
 453
 454 static atomic_t probe_count = ATOMIC_INIT(0);
 455 static DECLARE_WAIT_QUEUE_HEAD(probe_waitqueue);
 456
 457 static void driver_deferred_probe_add_trigger(struct device *dev,
 458                                               int local_trigger_count)
 459 {
 460         driver_deferred_probe_add(dev);
 461         /* Did a trigger occur while probing? Need to re-trigger if yes */
 462         if (local_trigger_count != atomic_read(&deferred_trigger_count))
 463                 driver_deferred_probe_trigger();
 464 }
 465
 466 static int really_probe(struct device *dev, struct device_driver *drv)
 467 {
 468         int ret = -EPROBE_DEFER;
 469         int local_trigger_count = atomic_read(&deferred_trigger_count);
 470         bool test_remove = IS_ENABLED(CONFIG_DEBUG_TEST_DRIVER_REMOVE) &&
 471                            !drv->suppress_bind_attrs;
 472
 473         if (defer_all_probes) {
 474                 /*
 475                  * Value of defer_all_probes can be set only by
 476                  * device_block_probing() which, in turn, will call
 477                  * wait_for_device_probe() right after that to avoid any races.
 478                  */
 479                 dev_dbg(dev, "Driver %s force probe deferral\n", drv->name);
 480                 driver_deferred_probe_add(dev);
 481                 return ret;
 482         }
 483
 484         ret = device_links_check_suppliers(dev);
 485         if (ret == -EPROBE_DEFER)
 486                 driver_deferred_probe_add_trigger(dev, local_trigger_count);
 487         if (ret)
 488                 return ret;
 489
 490         atomic_inc(&probe_count);
 491         pr_debug("bus: '%s': %s: probing driver %s with device %s\n",
 492                  drv->bus->name, __func__, drv->name, dev_name(dev));
 493         if (!list_empty(&dev->devres_head)) {
 494                 dev_crit(dev, "Resources present before probing\n");
 495                 return -EBUSY;
 496         }
 497
 498 re_probe:
 499         dev->driver = drv;
 500
 501         /* If using pinctrl, bind pins now before probing */
 502         ret = pinctrl_bind_pins(dev);
 503         if (ret)
 504                 goto pinctrl_bind_failed;
 505
 506         if (dev->bus->dma_configure) {
 507                 ret = dev->bus->dma_configure(dev);
 508                 if (ret)
 509                         goto probe_failed;
 510         }
 511
 512         if (driver_sysfs_add(dev)) {
 513                 pr_err("%s: driver_sysfs_add(%s) failed\n",
 514                        __func__, dev_name(dev));
 515                 goto probe_failed;
 516         }
 517
 518         if (dev->pm_domain && dev->pm_domain->activate) {
 519                 ret = dev->pm_domain->activate(dev);
 520                 if (ret)
 521                         goto probe_failed;
 522         }
 523
 524         if (dev->bus->probe) {
 525                 ret = dev->bus->probe(dev);
 526                 if (ret)
 527                         goto probe_failed;
 528         } else if (drv->probe) {
 529                 ret = drv->probe(dev);
 530                 if (ret)
 531                         goto probe_failed;
 532         }
 533
 534         if (device_add_groups(dev, drv->dev_groups)) {
 535                 dev_err(dev, "device_add_groups() failed\n");
 536                 goto dev_groups_failed;
 537         }
 538
 539         if (test_remove) {
 540                 test_remove = false;
 541
 542                 device_remove_groups(dev, drv->dev_groups);
 543
 544                 if (dev->bus->remove)
 545                         dev->bus->remove(dev);
 546                 else if (drv->remove)
 547                         drv->remove(dev);
 548
 549                 devres_release_all(dev);
 550                 driver_sysfs_remove(dev);
 551                 dev->driver = NULL;
 552                 dev_set_drvdata(dev, NULL);
 553                 if (dev->pm_domain && dev->pm_domain->dismiss)
 554                         dev->pm_domain->dismiss(dev);
 555                 pm_runtime_reinit(dev);
 556
 557                 goto re_probe;
 558         }
 559
 560         pinctrl_init_done(dev);
 561
 562         if (dev->pm_domain && dev->pm_domain->sync)
 563                 dev->pm_domain->sync(dev);
 564
 565         driver_bound(dev);
 566         ret = 1;
 567         pr_debug("bus: '%s': %s: bound device %s to driver %s\n",
 568                  drv->bus->name, __func__, dev_name(dev), drv->name);
 569         goto done;
 570
 571 dev_groups_failed:
 572         if (dev->bus->remove)
 573                 dev->bus->remove(dev);
 574         else if (drv->remove)
 575                 drv->remove(dev);
 576 probe_failed:
 577         if (dev->bus)
 578                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 579                                              BUS_NOTIFY_DRIVER_NOT_BOUND, dev);
 580 pinctrl_bind_failed:
 581         device_links_no_driver(dev);
 582         devres_release_all(dev);
 583         arch_teardown_dma_ops(dev);
 584         driver_sysfs_remove(dev);
 585         dev->driver = NULL;
 586         dev_set_drvdata(dev, NULL);
 587         if (dev->pm_domain && dev->pm_domain->dismiss)
 588                 dev->pm_domain->dismiss(dev);
 589         pm_runtime_reinit(dev);
 590         dev_pm_set_driver_flags(dev, 0);
 591
 592         switch (ret) {
 593         case -EPROBE_DEFER:
 594                 /* Driver requested deferred probing */
 595                 dev_dbg(dev, "Driver %s requests probe deferral\n", drv->name);
 596                 driver_deferred_probe_add_trigger(dev, local_trigger_count);
 597                 break;
 598         case -ENODEV:
 599         case -ENXIO:
 600                 pr_debug("%s: probe of %s rejects match %d\n",
 601                          drv->name, dev_name(dev), ret);
 602                 break;
 603         default:
 604                 /* driver matched but the probe failed */
 605                 pr_warn("%s: probe of %s failed with error %d\n",
 606                         drv->name, dev_name(dev), ret);
 607         }
 608         /*
 609          * Ignore errors returned by ->probe so that the next driver can try
 610          * its luck.
 611          */
 612         ret = 0;
 613 done:
 614         atomic_dec(&probe_count);
 615         wake_up(&probe_waitqueue);
 616         return ret;
 617 }
 618
 619 /*
 620  * For initcall_debug, show the driver probe time.
 621  */
 622 static int really_probe_debug(struct device *dev, struct device_driver *drv)
 623 {
 624         ktime_t calltime, delta, rettime;
 625         int ret;
 626
 627         calltime = ktime_get();
 628         ret = really_probe(dev, drv);
 629         rettime = ktime_get();
 630         delta = ktime_sub(rettime, calltime);
 631         pr_debug("probe of %s returned %d after %lld usecs\n",
 632                  dev_name(dev), ret, (s64) ktime_to_us(delta));
 633         return ret;
 634 }
 635
 636 /**
 637  * driver_probe_done
 638  * Determine if the probe sequence is finished or not.
 639  *
 640  * Should somehow figure out how to use a semaphore, not an atomic variable...
 641  */
 642 int driver_probe_done(void)
 643 {
 644         int local_probe_count = atomic_read(&probe_count);
 645
 646         pr_debug("%s: probe_count = %d\n", __func__, local_probe_count);
 647         if (local_probe_count)
 648                 return -EBUSY;
 649         return 0;
 650 }
 651
 652 /**
 653  * wait_for_device_probe
 654  * Wait for device probing to be completed.
 655  */
 656 void wait_for_device_probe(void)
 657 {
 658         /* wait for probe timeout */
 659         wait_event(probe_timeout_waitqueue, !driver_deferred_probe_timeout);
 660
 661         /* wait for the deferred probe workqueue to finish */
 662         flush_work(&deferred_probe_work);
 663
 664         /* wait for the known devices to complete their probing */
 665         wait_event(probe_waitqueue, atomic_read(&probe_count) == 0);
 666         async_synchronize_full();
 667 }
 668 EXPORT_SYMBOL_GPL(wait_for_device_probe);
 669
 670 /**
 671  * driver_probe_device - attempt to bind device & driver together
 672  * @drv: driver to bind a device to
 673  * @dev: device to try to bind to the driver
 674  *
 675  * This function returns -ENODEV if the device is not registered,
 676  * 1 if the device is bound successfully and 0 otherwise.
 677  *
 678  * This function must be called with @dev lock held.  When called for a
 679  * USB interface, @dev->parent lock must be held as well.
 680  *
 681  * If the device has a parent, runtime-resume the parent before driver probing.
 682  */
 683 int driver_probe_device(struct device_driver *drv, struct device *dev)
 684 {
 685         int ret = 0;
 686
 687         if (!device_is_registered(dev))
 688                 return -ENODEV;
 689
 690         pr_debug("bus: '%s': %s: matched device %s with driver %s\n",
 691                  drv->bus->name, __func__, dev_name(dev), drv->name);
 692
 693         pm_runtime_get_suppliers(dev);
 694         if (dev->parent)
 695                 pm_runtime_get_sync(dev->parent);
 696
 697         pm_runtime_barrier(dev);
 698         if (initcall_debug)
 699                 ret = really_probe_debug(dev, drv);
 700         else
 701                 ret = really_probe(dev, drv);
 702         pm_request_idle(dev);
 703
 704         if (dev->parent)
 705                 pm_runtime_put(dev->parent);
 706
 707         pm_runtime_put_suppliers(dev);
 708         return ret;
 709 }
 710
 711 static inline bool cmdline_requested_async_probing(const char *drv_name)
 712 {
 713         return parse_option_str(async_probe_drv_names, drv_name);
 714 }
 715
 716 /* The option format is "driver_async_probe=drv_name1,drv_name2,..." */
 717 static int __init save_async_options(char *buf)
 718 {
 719         if (strlen(buf) >= ASYNC_DRV_NAMES_MAX_LEN)
 720                 pr_warn("Too long list of driver names for 'driver_async_probe'!\n");
 721
 722         strlcpy(async_probe_drv_names, buf, ASYNC_DRV_NAMES_MAX_LEN);
 723         return 0;
 724 }
 725 __setup("driver_async_probe=", save_async_options);
 726
 727 bool driver_allows_async_probing(struct device_driver *drv)
 728 {
 729         switch (drv->probe_type) {
 730         case PROBE_PREFER_ASYNCHRONOUS:
 731                 return true;
 732
 733         case PROBE_FORCE_SYNCHRONOUS:
 734                 return false;
 735
 736         default:
 737                 if (cmdline_requested_async_probing(drv->name))
 738                         return true;
 739
 740                 if (module_requested_async_probing(drv->owner))
 741                         return true;
 742
 743                 return false;
 744         }
 745 }
 746
 747 struct device_attach_data {
 748         struct device *dev;
 749
 750         /*
 751          * Indicates whether we are are considering asynchronous probing or
 752          * not. Only initial binding after device or driver registration
 753          * (including deferral processing) may be done asynchronously, the
 754          * rest is always synchronous, as we expect it is being done by
 755          * request from userspace.
 756          */
 757         bool check_async;
 758
 759         /*
 760          * Indicates if we are binding synchronous or asynchronous drivers.
 761          * When asynchronous probing is enabled we'll execute 2 passes
 762          * over drivers: first pass doing synchronous probing and second
 763          * doing asynchronous probing (if synchronous did not succeed -
 764          * most likely because there was no driver requiring synchronous
 765          * probing - and we found asynchronous driver during first pass).
 766          * The 2 passes are done because we can't shoot asynchronous
 767          * probe for given device and driver from bus_for_each_drv() since
 768          * driver pointer is not guaranteed to stay valid once
 769          * bus_for_each_drv() iterates to the next driver on the bus.
 770          */
 771         bool want_async;
 772
 773         /*
 774          * We'll set have_async to 'true' if, while scanning for matching
 775          * driver, we'll encounter one that requests asynchronous probing.
 776          */
 777         bool have_async;
 778 };
 779
 780 static int __device_attach_driver(struct device_driver *drv, void *_data)
 781 {
 782         struct device_attach_data *data = _data;
 783         struct device *dev = data->dev;
 784         bool async_allowed;
 785         int ret;
 786
 787         ret = driver_match_device(drv, dev);
 788         if (ret == 0) {
 789                 /* no match */
 790                 return 0;
 791         } else if (ret == -EPROBE_DEFER) {
 792                 dev_dbg(dev, "Device match requests probe deferral\n");
 793                 driver_deferred_probe_add(dev);
 794         } else if (ret < 0) {
 795                 dev_dbg(dev, "Bus failed to match device: %d\n", ret);
 796                 return ret;
 797         } /* ret > 0 means positive match */
 798
 799         async_allowed = driver_allows_async_probing(drv);
 800
 801         if (async_allowed)
 802                 data->have_async = true;
 803
 804         if (data->check_async && async_allowed != data->want_async)
 805                 return 0;
 806
 807         return driver_probe_device(drv, dev);
 808 }
 809
 810 static void __device_attach_async_helper(void *_dev, async_cookie_t cookie)
 811 {
 812         struct device *dev = _dev;
 813         struct device_attach_data data = {
 814                 .dev            = dev,
 815                 .check_async    = true,
 816                 .want_async     = true,
 817         };
 818
 819         device_lock(dev);
 820
 821         /*
 822          * Check if device has already been removed or claimed. This may
 823          * happen with driver loading, device discovery/registration,
 824          * and deferred probe processing happens all at once with
 825          * multiple threads.
 826          */
 827         if (dev->p->dead || dev->driver)
 828                 goto out_unlock;
 829
 830         if (dev->parent)
 831                 pm_runtime_get_sync(dev->parent);
 832
 833         bus_for_each_drv(dev->bus, NULL, &data, __device_attach_driver);
 834         dev_dbg(dev, "async probe completed\n");
 835
 836         pm_request_idle(dev);
 837
 838         if (dev->parent)
 839                 pm_runtime_put(dev->parent);
 840 out_unlock:
 841         device_unlock(dev);
 842
 843         put_device(dev);
 844 }
 845
 846 static int __device_attach(struct device *dev, bool allow_async)
 847 {
 848         int ret = 0;
 849
 850         device_lock(dev);
 851         if (dev->driver) {
 852                 if (device_is_bound(dev)) {
 853                         ret = 1;
 854                         goto out_unlock;
 855                 }
 856                 ret = device_bind_driver(dev);
 857                 if (ret == 0)
 858                         ret = 1;
 859                 else {
 860                         dev->driver = NULL;
 861                         ret = 0;
 862                 }
 863         } else {
 864                 struct device_attach_data data = {
 865                         .dev = dev,
 866                         .check_async = allow_async,
 867                         .want_async = false,
 868                 };
 869
 870                 if (dev->parent)
 871                         pm_runtime_get_sync(dev->parent);
 872
 873                 ret = bus_for_each_drv(dev->bus, NULL, &data,
 874                                         __device_attach_driver);
 875                 if (!ret && allow_async && data.have_async) {
 876                         /*
 877                          * If we could not find appropriate driver
 878                          * synchronously and we are allowed to do
 879                          * async probes and there are drivers that
 880                          * want to probe asynchronously, we'll
 881                          * try them.
 882                          */
 883                         dev_dbg(dev, "scheduling asynchronous probe\n");
 884                         get_device(dev);
 885                         async_schedule_dev(__device_attach_async_helper, dev);
 886                 } else {
 887                         pm_request_idle(dev);
 888                 }
 889
 890                 if (dev->parent)
 891                         pm_runtime_put(dev->parent);
 892         }
 893 out_unlock:
 894         device_unlock(dev);
 895         return ret;
 896 }
 897
 898 /**
 899  * device_attach - try to attach device to a driver.
 900  * @dev: device.
 901  *
 902  * Walk the list of drivers that the bus has and call
 903  * driver_probe_device() for each pair. If a compatible
 904  * pair is found, break out and return.
 905  *
 906  * Returns 1 if the device was bound to a driver;
 907  * 0 if no matching driver was found;
 908  * -ENODEV if the device is not registered.
 909  *
 910  * When called for a USB interface, @dev->parent lock must be held.
 911  */
 912 int device_attach(struct device *dev)
 913 {
 914         return __device_attach(dev, false);
 915 }
 916 EXPORT_SYMBOL_GPL(device_attach);
 917
 918 void device_initial_probe(struct device *dev)
 919 {
 920         __device_attach(dev, true);
 921 }
 922
 923 /*
 924  * __device_driver_lock - acquire locks needed to manipulate dev->drv
 925  * @dev: Device we will update driver info for
 926  * @parent: Parent device. Needed if the bus requires parent lock
 927  *
 928  * This function will take the required locks for manipulating dev->drv.
 929  * Normally this will just be the @dev lock, but when called for a USB
 930  * interface, @parent lock will be held as well.
 931  */
 932 static void __device_driver_lock(struct device *dev, struct device *parent)
 933 {
 934         if (parent && dev->bus->need_parent_lock)
 935                 device_lock(parent);
 936         device_lock(dev);
 937 }
 938
 939 /*
 940  * __device_driver_unlock - release locks needed to manipulate dev->drv
 941  * @dev: Device we will update driver info for
 942  * @parent: Parent device. Needed if the bus requires parent lock
 943  *
 944  * This function will release the required locks for manipulating dev->drv.
 945  * Normally this will just be the the @dev lock, but when called for a
 946  * USB interface, @parent lock will be released as well.
 947  */
 948 static void __device_driver_unlock(struct device *dev, struct device *parent)
 949 {
 950         device_unlock(dev);
 951         if (parent && dev->bus->need_parent_lock)
 952                 device_unlock(parent);
 953 }
 954
 955 /**
 956  * device_driver_attach - attach a specific driver to a specific device
 957  * @drv: Driver to attach
 958  * @dev: Device to attach it to
 959  *
 960  * Manually attach driver to a device. Will acquire both @dev lock and
 961  * @dev->parent lock if needed.
 962  */
 963 int device_driver_attach(struct device_driver *drv, struct device *dev)
 964 {
 965         int ret = 0;
 966
 967         __device_driver_lock(dev, dev->parent);
 968
 969         /*
 970          * If device has been removed or someone has already successfully
 971          * bound a driver before us just skip the driver probe call.
 972          */
 973         if (!dev->p->dead && !dev->driver)
 974                 ret = driver_probe_device(drv, dev);
 975
 976         __device_driver_unlock(dev, dev->parent);
 977
 978         return ret;
 979 }
 980
 981 static void __driver_attach_async_helper(void *_dev, async_cookie_t cookie)
 982 {
 983         struct device *dev = _dev;
 984         struct device_driver *drv;
 985         int ret = 0;
 986
 987         __device_driver_lock(dev, dev->parent);
 988
 989         drv = dev->p->async_driver;
 990
 991         /*
 992          * If device has been removed or someone has already successfully
 993          * bound a driver before us just skip the driver probe call.
 994          */
 995         if (!dev->p->dead && !dev->driver)
 996                 ret = driver_probe_device(drv, dev);
 997
 998         __device_driver_unlock(dev, dev->parent);
 999
1000         dev_dbg(dev, "driver %s async attach completed: %d\n", drv->name, ret);
1001
1002         put_device(dev);
1003 }
1004
1005 static int __driver_attach(struct device *dev, void *data)
1006 {
1007         struct device_driver *drv = data;
1008         int ret;
1009
1010         /*
1011          * Lock device and try to bind to it. We drop the error
1012          * here and always return 0, because we need to keep trying
1013          * to bind to devices and some drivers will return an error
1014          * simply if it didn't support the device.
1015          *
1016          * driver_probe_device() will spit a warning if there
1017          * is an error.
1018          */
1019
1020         ret = driver_match_device(drv, dev);
1021         if (ret == 0) {
1022                 /* no match */
1023                 return 0;
1024         } else if (ret == -EPROBE_DEFER) {
1025                 dev_dbg(dev, "Device match requests probe deferral\n");
1026                 driver_deferred_probe_add(dev);
1027         } else if (ret < 0) {
1028                 dev_dbg(dev, "Bus failed to match device: %d\n", ret);
1029                 return ret;
1030         } /* ret > 0 means positive match */
1031
1032         if (driver_allows_async_probing(drv)) {
1033                 /*
1034                  * Instead of probing the device synchronously we will
1035                  * probe it asynchronously to allow for more parallelism.
1036                  *
1037                  * We only take the device lock here in order to guarantee
1038                  * that the dev->driver and async_driver fields are protected
1039                  */
1040                 dev_dbg(dev, "probing driver %s asynchronously\n", drv->name);
1041                 device_lock(dev);
1042                 if (!dev->driver) {
1043                         get_device(dev);
1044                         dev->p->async_driver = drv;
1045                         async_schedule_dev(__driver_attach_async_helper, dev);
1046                 }
1047                 device_unlock(dev);
1048                 return 0;
1049         }
1050
1051         device_driver_attach(drv, dev);
1052
1053         return 0;
1054 }
1055
1056 /**
1057  * driver_attach - try to bind driver to devices.
1058  * @drv: driver.
1059  *
1060  * Walk the list of devices that the bus has on it and try to
1061  * match the driver with each one.  If driver_probe_device()
1062  * returns 0 and the @dev->driver is set, we've found a
1063  * compatible pair.
1064  */
1065 int driver_attach(struct device_driver *drv)
1066 {
1067         return bus_for_each_dev(drv->bus, NULL, drv, __driver_attach);
1068 }
1069 EXPORT_SYMBOL_GPL(driver_attach);
1070
1071 /*
1072  * __device_release_driver() must be called with @dev lock held.
1073  * When called for a USB interface, @dev->parent lock must be held as well.
1074  */
1075 static void __device_release_driver(struct device *dev, struct device *parent)
1076 {
1077         struct device_driver *drv;
1078
1079         drv = dev->driver;
1080         if (drv) {
1081                 while (device_links_busy(dev)) {
1082                         __device_driver_unlock(dev, parent);
1083
1084                         device_links_unbind_consumers(dev);
1085
1086                         __device_driver_lock(dev, parent);
1087                         /*
1088                          * A concurrent invocation of the same function might
1089                          * have released the driver successfully while this one
1090                          * was waiting, so check for that.
1091                          */
1092                         if (dev->driver != drv)
1093                                 return;
1094                 }
1095
1096                 pm_runtime_get_sync(dev);
1097                 pm_runtime_clean_up_links(dev);
1098
1099                 driver_sysfs_remove(dev);
1100
1101                 if (dev->bus)
1102                         blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
1103                                                      BUS_NOTIFY_UNBIND_DRIVER,
1104                                                      dev);
1105
1106                 pm_runtime_put_sync(dev);
1107
1108                 device_remove_groups(dev, drv->dev_groups);
1109
1110                 if (dev->bus && dev->bus->remove)
1111                         dev->bus->remove(dev);
1112                 else if (drv->remove)
1113                         drv->remove(dev);
1114
1115                 device_links_driver_cleanup(dev);
1116
1117                 devres_release_all(dev);
1118                 arch_teardown_dma_ops(dev);
1119                 dev->driver = NULL;
1120                 dev_set_drvdata(dev, NULL);
1121                 if (dev->pm_domain && dev->pm_domain->dismiss)
1122                         dev->pm_domain->dismiss(dev);
1123                 pm_runtime_reinit(dev);
1124                 dev_pm_set_driver_flags(dev, 0);
1125
1126                 klist_remove(&dev->p->knode_driver);
1127                 device_pm_check_callbacks(dev);
1128                 if (dev->bus)
1129                         blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
1130                                                      BUS_NOTIFY_UNBOUND_DRIVER,
1131                                                      dev);
1132
1133                 kobject_uevent(&dev->kobj, KOBJ_UNBIND);
1134         }
1135 }
1136
1137 void device_release_driver_internal(struct device *dev,
1138                                     struct device_driver *drv,
1139                                     struct device *parent)
1140 {
1141         __device_driver_lock(dev, parent);
1142
1143         if (!drv || drv == dev->driver)
1144                 __device_release_driver(dev, parent);
1145
1146         __device_driver_unlock(dev, parent);
1147 }
1148
1149 /**
1150  * device_release_driver - manually detach device from driver.
1151  * @dev: device.
1152  *
1153  * Manually detach device from driver.
1154  * When called for a USB interface, @dev->parent lock must be held.
1155  *
1156  * If this function is to be called with @dev->parent lock held, ensure that
1157  * the device's consumers are unbound in advance or that their locks can be
1158  * acquired under the @dev->parent lock.
1159  */
1160 void device_release_driver(struct device *dev)
1161 {
1162         /*
1163          * If anyone calls device_release_driver() recursively from
1164          * within their ->remove callback for the same device, they
1165          * will deadlock right here.
1166          */
1167         device_release_driver_internal(dev, NULL, NULL);
1168 }
1169 EXPORT_SYMBOL_GPL(device_release_driver);
1170
1171 /**
1172  * device_driver_detach - detach driver from a specific device
1173  * @dev: device to detach driver from
1174  *
1175  * Detach driver from device. Will acquire both @dev lock and @dev->parent
1176  * lock if needed.
1177  */
1178 void device_driver_detach(struct device *dev)
1179 {
1180         device_release_driver_internal(dev, NULL, dev->parent);
1181 }
1182
1183 /**
1184  * driver_detach - detach driver from all devices it controls.
1185  * @drv: driver.
1186  */
1187 void driver_detach(struct device_driver *drv)
1188 {
1189         struct device_private *dev_prv;
1190         struct device *dev;
1191
1192         if (driver_allows_async_probing(drv))
1193                 async_synchronize_full();
1194
1195         for (;;) {
1196                 spin_lock(&drv->p->klist_devices.k_lock);
1197                 if (list_empty(&drv->p->klist_devices.k_list)) {
1198                         spin_unlock(&drv->p->klist_devices.k_lock);
1199                         break;
1200                 }
1201                 dev_prv = list_last_entry(&drv->p->klist_devices.k_list,
1202                                      struct device_private,
1203                                      knode_driver.n_node);
1204                 dev = dev_prv->device;
1205                 get_device(dev);
1206                 spin_unlock(&drv->p->klist_devices.k_lock);
1207                 device_release_driver_internal(dev, drv, dev->parent);
1208                 put_device(dev);
1209         }
1210 }