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         /*
 168          * A successful probe means that all the devices in the pending list
 169          * should be triggered to be reprobed.  Move all the deferred devices
 170          * into the active list so they can be retried by the workqueue
 171          */
 172         mutex_lock(&deferred_probe_mutex);
 173         atomic_inc(&deferred_trigger_count);
 174         list_splice_tail_init(&deferred_probe_pending_list,
 175                               &deferred_probe_active_list);
 176         mutex_unlock(&deferred_probe_mutex);
 177
 178         /*
 179          * Kick the re-probe thread.  It may already be scheduled, but it is
 180          * safe to kick it again.
 181          */
 182         schedule_work(&deferred_probe_work);
 183 }
 184
 185 /**
 186  * device_block_probing() - Block/defer device's probes
 187  *
 188  *      It will disable probing of devices and defer their probes instead.
 189  */
 190 void device_block_probing(void)
 191 {
 192         defer_all_probes = true;
 193         /* sync with probes to avoid races. */
 194         wait_for_device_probe();
 195 }
 196
 197 /**
 198  * device_unblock_probing() - Unblock/enable device's probes
 199  *
 200  *      It will restore normal behavior and trigger re-probing of deferred
 201  * devices.
 202  */
 203 void device_unblock_probing(void)
 204 {
 205         defer_all_probes = false;
 206         driver_deferred_probe_trigger();
 207 }
 208
 209 /*
 210  * deferred_devs_show() - Show the devices in the deferred probe pending list.
 211  */
 212 static int deferred_devs_show(struct seq_file *s, void *data)
 213 {
 214         struct device_private *curr;
 215
 216         mutex_lock(&deferred_probe_mutex);
 217
 218         list_for_each_entry(curr, &deferred_probe_pending_list, deferred_probe)
 219                 seq_printf(s, "%s\n", dev_name(curr->device));
 220
 221         mutex_unlock(&deferred_probe_mutex);
 222
 223         return 0;
 224 }
 225 DEFINE_SHOW_ATTRIBUTE(deferred_devs);
 226
 227 #ifdef CONFIG_MODULES
 228 /*
 229  * In the case of modules, set the default probe timeout to
 230  * 30 seconds to give userland some time to load needed modules
 231  */
 232 int driver_deferred_probe_timeout = 30;
 233 #else
 234 /* In the case of !modules, no probe timeout needed */
 235 int driver_deferred_probe_timeout = -1;
 236 #endif
 237 EXPORT_SYMBOL_GPL(driver_deferred_probe_timeout);
 238
 239 static int __init deferred_probe_timeout_setup(char *str)
 240 {
 241         int timeout;
 242
 243         if (!kstrtoint(str, 10, &timeout))
 244                 driver_deferred_probe_timeout = timeout;
 245         return 1;
 246 }
 247 __setup("deferred_probe_timeout=", deferred_probe_timeout_setup);
 248
 249 /**
 250  * driver_deferred_probe_check_state() - Check deferred probe state
 251  * @dev: device to check
 252  *
 253  * Return:
 254  * -ENODEV if initcalls have completed and modules are disabled.
 255  * -ETIMEDOUT if the deferred probe timeout was set and has expired
 256  *  and modules are enabled.
 257  * -EPROBE_DEFER in other cases.
 258  *
 259  * Drivers or subsystems can opt-in to calling this function instead of directly
 260  * returning -EPROBE_DEFER.
 261  */
 262 int driver_deferred_probe_check_state(struct device *dev)
 263 {
 264         if (!IS_ENABLED(CONFIG_MODULES) && initcalls_done) {
 265                 dev_warn(dev, "ignoring dependency for device, assuming no driver");
 266                 return -ENODEV;
 267         }
 268
 269         if (!driver_deferred_probe_timeout) {
 270                 dev_WARN(dev, "deferred probe timeout, ignoring dependency");
 271                 return -ETIMEDOUT;
 272         }
 273
 274         return -EPROBE_DEFER;
 275 }
 276
 277 static void deferred_probe_timeout_work_func(struct work_struct *work)
 278 {
 279         struct device_private *private, *p;
 280
 281         driver_deferred_probe_timeout = 0;
 282         driver_deferred_probe_trigger();
 283         flush_work(&deferred_probe_work);
 284
 285         list_for_each_entry_safe(private, p, &deferred_probe_pending_list, deferred_probe)
 286                 dev_info(private->device, "deferred probe pending");
 287 }
 288 static DECLARE_DELAYED_WORK(deferred_probe_timeout_work, deferred_probe_timeout_work_func);
 289
 290 /**
 291  * deferred_probe_initcall() - Enable probing of deferred devices
 292  *
 293  * We don't want to get in the way when the bulk of drivers are getting probed.
 294  * Instead, this initcall makes sure that deferred probing is delayed until
 295  * late_initcall time.
 296  */
 297 static int deferred_probe_initcall(void)
 298 {
 299         deferred_devices = debugfs_create_file("devices_deferred", 0444, NULL,
 300                                                NULL, &deferred_devs_fops);
 301
 302         driver_deferred_probe_enable = true;
 303         driver_deferred_probe_trigger();
 304         /* Sort as many dependencies as possible before exiting initcalls */
 305         flush_work(&deferred_probe_work);
 306         initcalls_done = true;
 307
 308         /*
 309          * Trigger deferred probe again, this time we won't defer anything
 310          * that is optional
 311          */
 312         driver_deferred_probe_trigger();
 313         flush_work(&deferred_probe_work);
 314
 315         if (driver_deferred_probe_timeout > 0) {
 316                 schedule_delayed_work(&deferred_probe_timeout_work,
 317                         driver_deferred_probe_timeout * HZ);
 318         }
 319         return 0;
 320 }
 321 late_initcall(deferred_probe_initcall);
 322
 323 static void __exit deferred_probe_exit(void)
 324 {
 325         debugfs_remove_recursive(deferred_devices);
 326 }
 327 __exitcall(deferred_probe_exit);
 328
 329 /**
 330  * device_is_bound() - Check if device is bound to a driver
 331  * @dev: device to check
 332  *
 333  * Returns true if passed device has already finished probing successfully
 334  * against a driver.
 335  *
 336  * This function must be called with the device lock held.
 337  */
 338 bool device_is_bound(struct device *dev)
 339 {
 340         return dev->p && klist_node_attached(&dev->p->knode_driver);
 341 }
 342
 343 static void driver_bound(struct device *dev)
 344 {
 345         if (device_is_bound(dev)) {
 346                 printk(KERN_WARNING "%s: device %s already bound\n",
 347                         __func__, kobject_name(&dev->kobj));
 348                 return;
 349         }
 350
 351         pr_debug("driver: '%s': %s: bound to device '%s'\n", dev->driver->name,
 352                  __func__, dev_name(dev));
 353
 354         klist_add_tail(&dev->p->knode_driver, &dev->driver->p->klist_devices);
 355         device_links_driver_bound(dev);
 356
 357         device_pm_check_callbacks(dev);
 358
 359         /*
 360          * Make sure the device is no longer in one of the deferred lists and
 361          * kick off retrying all pending devices
 362          */
 363         driver_deferred_probe_del(dev);
 364         driver_deferred_probe_trigger();
 365
 366         if (dev->bus)
 367                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 368                                              BUS_NOTIFY_BOUND_DRIVER, dev);
 369
 370         kobject_uevent(&dev->kobj, KOBJ_BIND);
 371 }
 372
 373 static ssize_t coredump_store(struct device *dev, struct device_attribute *attr,
 374                             const char *buf, size_t count)
 375 {
 376         device_lock(dev);
 377         dev->driver->coredump(dev);
 378         device_unlock(dev);
 379
 380         return count;
 381 }
 382 static DEVICE_ATTR_WO(coredump);
 383
 384 static int driver_sysfs_add(struct device *dev)
 385 {
 386         int ret;
 387
 388         if (dev->bus)
 389                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 390                                              BUS_NOTIFY_BIND_DRIVER, dev);
 391
 392         ret = sysfs_create_link(&dev->driver->p->kobj, &dev->kobj,
 393                                 kobject_name(&dev->kobj));
 394         if (ret)
 395                 goto fail;
 396
 397         ret = sysfs_create_link(&dev->kobj, &dev->driver->p->kobj,
 398                                 "driver");
 399         if (ret)
 400                 goto rm_dev;
 401
 402         if (!IS_ENABLED(CONFIG_DEV_COREDUMP) || !dev->driver->coredump ||
 403             !device_create_file(dev, &dev_attr_coredump))
 404                 return 0;
 405
 406         sysfs_remove_link(&dev->kobj, "driver");
 407
 408 rm_dev:
 409         sysfs_remove_link(&dev->driver->p->kobj,
 410                           kobject_name(&dev->kobj));
 411
 412 fail:
 413         return ret;
 414 }
 415
 416 static void driver_sysfs_remove(struct device *dev)
 417 {
 418         struct device_driver *drv = dev->driver;
 419
 420         if (drv) {
 421                 if (drv->coredump)
 422                         device_remove_file(dev, &dev_attr_coredump);
 423                 sysfs_remove_link(&drv->p->kobj, kobject_name(&dev->kobj));
 424                 sysfs_remove_link(&dev->kobj, "driver");
 425         }
 426 }
 427
 428 /**
 429  * device_bind_driver - bind a driver to one device.
 430  * @dev: device.
 431  *
 432  * Allow manual attachment of a driver to a device.
 433  * Caller must have already set @dev->driver.
 434  *
 435  * Note that this does not modify the bus reference count
 436  * nor take the bus's rwsem. Please verify those are accounted
 437  * for before calling this. (It is ok to call with no other effort
 438  * from a driver's probe() method.)
 439  *
 440  * This function must be called with the device lock held.
 441  */
 442 int device_bind_driver(struct device *dev)
 443 {
 444         int ret;
 445
 446         ret = driver_sysfs_add(dev);
 447         if (!ret)
 448                 driver_bound(dev);
 449         else if (dev->bus)
 450                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 451                                              BUS_NOTIFY_DRIVER_NOT_BOUND, dev);
 452         return ret;
 453 }
 454 EXPORT_SYMBOL_GPL(device_bind_driver);
 455
 456 static atomic_t probe_count = ATOMIC_INIT(0);
 457 static DECLARE_WAIT_QUEUE_HEAD(probe_waitqueue);
 458
 459 static void driver_deferred_probe_add_trigger(struct device *dev,
 460                                               int local_trigger_count)
 461 {
 462         driver_deferred_probe_add(dev);
 463         /* Did a trigger occur while probing? Need to re-trigger if yes */
 464         if (local_trigger_count != atomic_read(&deferred_trigger_count))
 465                 driver_deferred_probe_trigger();
 466 }
 467
 468 static int really_probe(struct device *dev, struct device_driver *drv)
 469 {
 470         int ret = -EPROBE_DEFER;
 471         int local_trigger_count = atomic_read(&deferred_trigger_count);
 472         bool test_remove = IS_ENABLED(CONFIG_DEBUG_TEST_DRIVER_REMOVE) &&
 473                            !drv->suppress_bind_attrs;
 474
 475         if (defer_all_probes) {
 476                 /*
 477                  * Value of defer_all_probes can be set only by
 478                  * device_block_probing() which, in turn, will call
 479                  * wait_for_device_probe() right after that to avoid any races.
 480                  */
 481                 dev_dbg(dev, "Driver %s force probe deferral\n", drv->name);
 482                 driver_deferred_probe_add(dev);
 483                 return ret;
 484         }
 485
 486         ret = device_links_check_suppliers(dev);
 487         if (ret == -EPROBE_DEFER)
 488                 driver_deferred_probe_add_trigger(dev, local_trigger_count);
 489         if (ret)
 490                 return ret;
 491
 492         atomic_inc(&probe_count);
 493         pr_debug("bus: '%s': %s: probing driver %s with device %s\n",
 494                  drv->bus->name, __func__, drv->name, dev_name(dev));
 495         if (!list_empty(&dev->devres_head)) {
 496                 dev_crit(dev, "Resources present before probing\n");
 497                 return -EBUSY;
 498         }
 499
 500 re_probe:
 501         dev->driver = drv;
 502
 503         /* If using pinctrl, bind pins now before probing */
 504         ret = pinctrl_bind_pins(dev);
 505         if (ret)
 506                 goto pinctrl_bind_failed;
 507
 508         if (dev->bus->dma_configure) {
 509                 ret = dev->bus->dma_configure(dev);
 510                 if (ret)
 511                         goto probe_failed;
 512         }
 513
 514         if (driver_sysfs_add(dev)) {
 515                 printk(KERN_ERR "%s: driver_sysfs_add(%s) failed\n",
 516                         __func__, dev_name(dev));
 517                 goto probe_failed;
 518         }
 519
 520         if (dev->pm_domain && dev->pm_domain->activate) {
 521                 ret = dev->pm_domain->activate(dev);
 522                 if (ret)
 523                         goto probe_failed;
 524         }
 525
 526         if (dev->bus->probe) {
 527                 ret = dev->bus->probe(dev);
 528                 if (ret)
 529                         goto probe_failed;
 530         } else if (drv->probe) {
 531                 ret = drv->probe(dev);
 532                 if (ret)
 533                         goto probe_failed;
 534         }
 535
 536         if (device_add_groups(dev, drv->dev_groups)) {
 537                 dev_err(dev, "device_add_groups() failed\n");
 538                 goto dev_groups_failed;
 539         }
 540
 541         if (test_remove) {
 542                 test_remove = false;
 543
 544                 device_remove_groups(dev, drv->dev_groups);
 545
 546                 if (dev->bus->remove)
 547                         dev->bus->remove(dev);
 548                 else if (drv->remove)
 549                         drv->remove(dev);
 550
 551                 devres_release_all(dev);
 552                 driver_sysfs_remove(dev);
 553                 dev->driver = NULL;
 554                 dev_set_drvdata(dev, NULL);
 555                 if (dev->pm_domain && dev->pm_domain->dismiss)
 556                         dev->pm_domain->dismiss(dev);
 557                 pm_runtime_reinit(dev);
 558
 559                 goto re_probe;
 560         }
 561
 562         pinctrl_init_done(dev);
 563
 564         if (dev->pm_domain && dev->pm_domain->sync)
 565                 dev->pm_domain->sync(dev);
 566
 567         driver_bound(dev);
 568         ret = 1;
 569         pr_debug("bus: '%s': %s: bound device %s to driver %s\n",
 570                  drv->bus->name, __func__, dev_name(dev), drv->name);
 571         goto done;
 572
 573 dev_groups_failed:
 574         if (dev->bus->remove)
 575                 dev->bus->remove(dev);
 576         else if (drv->remove)
 577                 drv->remove(dev);
 578 probe_failed:
 579         if (dev->bus)
 580                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 581                                              BUS_NOTIFY_DRIVER_NOT_BOUND, dev);
 582 pinctrl_bind_failed:
 583         device_links_no_driver(dev);
 584         devres_release_all(dev);
 585         arch_teardown_dma_ops(dev);
 586         driver_sysfs_remove(dev);
 587         dev->driver = NULL;
 588         dev_set_drvdata(dev, NULL);
 589         if (dev->pm_domain && dev->pm_domain->dismiss)
 590                 dev->pm_domain->dismiss(dev);
 591         pm_runtime_reinit(dev);
 592         dev_pm_set_driver_flags(dev, 0);
 593
 594         switch (ret) {
 595         case -EPROBE_DEFER:
 596                 /* Driver requested deferred probing */
 597                 dev_dbg(dev, "Driver %s requests probe deferral\n", drv->name);
 598                 driver_deferred_probe_add_trigger(dev, local_trigger_count);
 599                 break;
 600         case -ENODEV:
 601         case -ENXIO:
 602                 pr_debug("%s: probe of %s rejects match %d\n",
 603                          drv->name, dev_name(dev), ret);
 604                 break;
 605         default:
 606                 /* driver matched but the probe failed */
 607                 printk(KERN_WARNING
 608                        "%s: probe of %s failed with error %d\n",
 609                        drv->name, dev_name(dev), ret);
 610         }
 611         /*
 612          * Ignore errors returned by ->probe so that the next driver can try
 613          * its luck.
 614          */
 615         ret = 0;
 616 done:
 617         atomic_dec(&probe_count);
 618         wake_up(&probe_waitqueue);
 619         return ret;
 620 }
 621
 622 /*
 623  * For initcall_debug, show the driver probe time.
 624  */
 625 static int really_probe_debug(struct device *dev, struct device_driver *drv)
 626 {
 627         ktime_t calltime, delta, rettime;
 628         int ret;
 629
 630         calltime = ktime_get();
 631         ret = really_probe(dev, drv);
 632         rettime = ktime_get();
 633         delta = ktime_sub(rettime, calltime);
 634         printk(KERN_DEBUG "probe of %s returned %d after %lld usecs\n",
 635                dev_name(dev), ret, (s64) ktime_to_us(delta));
 636         return ret;
 637 }
 638
 639 /**
 640  * driver_probe_done
 641  * Determine if the probe sequence is finished or not.
 642  *
 643  * Should somehow figure out how to use a semaphore, not an atomic variable...
 644  */
 645 int driver_probe_done(void)
 646 {
 647         int local_probe_count = atomic_read(&probe_count);
 648
 649         pr_debug("%s: probe_count = %d\n", __func__, local_probe_count);
 650         if (local_probe_count)
 651                 return -EBUSY;
 652         return 0;
 653 }
 654
 655 /**
 656  * wait_for_device_probe
 657  * Wait for device probing to be completed.
 658  */
 659 void wait_for_device_probe(void)
 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                 printk(KERN_WARNING
 721                         "Too long list of driver names for 'driver_async_probe'!\n");
 722
 723         strlcpy(async_probe_drv_names, buf, ASYNC_DRV_NAMES_MAX_LEN);
 724         return 0;
 725 }
 726 __setup("driver_async_probe=", save_async_options);
 727
 728 bool driver_allows_async_probing(struct device_driver *drv)
 729 {
 730         switch (drv->probe_type) {
 731         case PROBE_PREFER_ASYNCHRONOUS:
 732                 return true;
 733
 734         case PROBE_FORCE_SYNCHRONOUS:
 735                 return false;
 736
 737         default:
 738                 if (cmdline_requested_async_probing(drv->name))
 739                         return true;
 740
 741                 if (module_requested_async_probing(drv->owner))
 742                         return true;
 743
 744                 return false;
 745         }
 746 }
 747
 748 struct device_attach_data {
 749         struct device *dev;
 750
 751         /*
 752          * Indicates whether we are are considering asynchronous probing or
 753          * not. Only initial binding after device or driver registration
 754          * (including deferral processing) may be done asynchronously, the
 755          * rest is always synchronous, as we expect it is being done by
 756          * request from userspace.
 757          */
 758         bool check_async;
 759
 760         /*
 761          * Indicates if we are binding synchronous or asynchronous drivers.
 762          * When asynchronous probing is enabled we'll execute 2 passes
 763          * over drivers: first pass doing synchronous probing and second
 764          * doing asynchronous probing (if synchronous did not succeed -
 765          * most likely because there was no driver requiring synchronous
 766          * probing - and we found asynchronous driver during first pass).
 767          * The 2 passes are done because we can't shoot asynchronous
 768          * probe for given device and driver from bus_for_each_drv() since
 769          * driver pointer is not guaranteed to stay valid once
 770          * bus_for_each_drv() iterates to the next driver on the bus.
 771          */
 772         bool want_async;
 773
 774         /*
 775          * We'll set have_async to 'true' if, while scanning for matching
 776          * driver, we'll encounter one that requests asynchronous probing.
 777          */
 778         bool have_async;
 779 };
 780
 781 static int __device_attach_driver(struct device_driver *drv, void *_data)
 782 {
 783         struct device_attach_data *data = _data;
 784         struct device *dev = data->dev;
 785         bool async_allowed;
 786         int ret;
 787
 788         ret = driver_match_device(drv, dev);
 789         if (ret == 0) {
 790                 /* no match */
 791                 return 0;
 792         } else if (ret == -EPROBE_DEFER) {
 793                 dev_dbg(dev, "Device match requests probe deferral\n");
 794                 driver_deferred_probe_add(dev);
 795         } else if (ret < 0) {
 796                 dev_dbg(dev, "Bus failed to match device: %d", ret);
 797                 return ret;
 798         } /* ret > 0 means positive match */
 799
 800         async_allowed = driver_allows_async_probing(drv);
 801
 802         if (async_allowed)
 803                 data->have_async = true;
 804
 805         if (data->check_async && async_allowed != data->want_async)
 806                 return 0;
 807
 808         return driver_probe_device(drv, dev);
 809 }
 810
 811 static void __device_attach_async_helper(void *_dev, async_cookie_t cookie)
 812 {
 813         struct device *dev = _dev;
 814         struct device_attach_data data = {
 815                 .dev            = dev,
 816                 .check_async    = true,
 817                 .want_async     = true,
 818         };
 819
 820         device_lock(dev);
 821
 822         /*
 823          * Check if device has already been removed or claimed. This may
 824          * happen with driver loading, device discovery/registration,
 825          * and deferred probe processing happens all at once with
 826          * multiple threads.
 827          */
 828         if (dev->p->dead || dev->driver)
 829                 goto out_unlock;
 830
 831         if (dev->parent)
 832                 pm_runtime_get_sync(dev->parent);
 833
 834         bus_for_each_drv(dev->bus, NULL, &data, __device_attach_driver);
 835         dev_dbg(dev, "async probe completed\n");
 836
 837         pm_request_idle(dev);
 838
 839         if (dev->parent)
 840                 pm_runtime_put(dev->parent);
 841 out_unlock:
 842         device_unlock(dev);
 843
 844         put_device(dev);
 845 }
 846
 847 static int __device_attach(struct device *dev, bool allow_async)
 848 {
 849         int ret = 0;
 850
 851         device_lock(dev);
 852         if (dev->driver) {
 853                 if (device_is_bound(dev)) {
 854                         ret = 1;
 855                         goto out_unlock;
 856                 }
 857                 ret = device_bind_driver(dev);
 858                 if (ret == 0)
 859                         ret = 1;
 860                 else {
 861                         dev->driver = NULL;
 862                         ret = 0;
 863                 }
 864         } else {
 865                 struct device_attach_data data = {
 866                         .dev = dev,
 867                         .check_async = allow_async,
 868                         .want_async = false,
 869                 };
 870
 871                 if (dev->parent)
 872                         pm_runtime_get_sync(dev->parent);
 873
 874                 ret = bus_for_each_drv(dev->bus, NULL, &data,
 875                                         __device_attach_driver);
 876                 if (!ret && allow_async && data.have_async) {
 877                         /*
 878                          * If we could not find appropriate driver
 879                          * synchronously and we are allowed to do
 880                          * async probes and there are drivers that
 881                          * want to probe asynchronously, we'll
 882                          * try them.
 883                          */
 884                         dev_dbg(dev, "scheduling asynchronous probe\n");
 885                         get_device(dev);
 886                         async_schedule_dev(__device_attach_async_helper, dev);
 887                 } else {
 888                         pm_request_idle(dev);
 889                 }
 890
 891                 if (dev->parent)
 892                         pm_runtime_put(dev->parent);
 893         }
 894 out_unlock:
 895         device_unlock(dev);
 896         return ret;
 897 }
 898
 899 /**
 900  * device_attach - try to attach device to a driver.
 901  * @dev: device.
 902  *
 903  * Walk the list of drivers that the bus has and call
 904  * driver_probe_device() for each pair. If a compatible
 905  * pair is found, break out and return.
 906  *
 907  * Returns 1 if the device was bound to a driver;
 908  * 0 if no matching driver was found;
 909  * -ENODEV if the device is not registered.
 910  *
 911  * When called for a USB interface, @dev->parent lock must be held.
 912  */
 913 int device_attach(struct device *dev)
 914 {
 915         return __device_attach(dev, false);
 916 }
 917 EXPORT_SYMBOL_GPL(device_attach);
 918
 919 void device_initial_probe(struct device *dev)
 920 {
 921         __device_attach(dev, true);
 922 }
 923
 924 /*
 925  * __device_driver_lock - acquire locks needed to manipulate dev->drv
 926  * @dev: Device we will update driver info for
 927  * @parent: Parent device. Needed if the bus requires parent lock
 928  *
 929  * This function will take the required locks for manipulating dev->drv.
 930  * Normally this will just be the @dev lock, but when called for a USB
 931  * interface, @parent lock will be held as well.
 932  */
 933 static void __device_driver_lock(struct device *dev, struct device *parent)
 934 {
 935         if (parent && dev->bus->need_parent_lock)
 936                 device_lock(parent);
 937         device_lock(dev);
 938 }
 939
 940 /*
 941  * __device_driver_unlock - release locks needed to manipulate dev->drv
 942  * @dev: Device we will update driver info for
 943  * @parent: Parent device. Needed if the bus requires parent lock
 944  *
 945  * This function will release the required locks for manipulating dev->drv.
 946  * Normally this will just be the the @dev lock, but when called for a
 947  * USB interface, @parent lock will be released as well.
 948  */
 949 static void __device_driver_unlock(struct device *dev, struct device *parent)
 950 {
 951         device_unlock(dev);
 952         if (parent && dev->bus->need_parent_lock)
 953                 device_unlock(parent);
 954 }
 955
 956 /**
 957  * device_driver_attach - attach a specific driver to a specific device
 958  * @drv: Driver to attach
 959  * @dev: Device to attach it to
 960  *
 961  * Manually attach driver to a device. Will acquire both @dev lock and
 962  * @dev->parent lock if needed.
 963  */
 964 int device_driver_attach(struct device_driver *drv, struct device *dev)
 965 {
 966         int ret = 0;
 967
 968         __device_driver_lock(dev, dev->parent);
 969
 970         /*
 971          * If device has been removed or someone has already successfully
 972          * bound a driver before us just skip the driver probe call.
 973          */
 974         if (!dev->p->dead && !dev->driver)
 975                 ret = driver_probe_device(drv, dev);
 976
 977         __device_driver_unlock(dev, dev->parent);
 978
 979         return ret;
 980 }
 981
 982 static void __driver_attach_async_helper(void *_dev, async_cookie_t cookie)
 983 {
 984         struct device *dev = _dev;
 985         struct device_driver *drv;
 986         int ret = 0;
 987
 988         __device_driver_lock(dev, dev->parent);
 989
 990         drv = dev->p->async_driver;
 991
 992         /*
 993          * If device has been removed or someone has already successfully
 994          * bound a driver before us just skip the driver probe call.
 995          */
 996         if (!dev->p->dead && !dev->driver)
 997                 ret = driver_probe_device(drv, dev);
 998
 999         __device_driver_unlock(dev, dev->parent);
1000
1001         dev_dbg(dev, "driver %s async attach completed: %d\n", drv->name, ret);
1002
1003         put_device(dev);
1004 }
1005
1006 static int __driver_attach(struct device *dev, void *data)
1007 {
1008         struct device_driver *drv = data;
1009         int ret;
1010
1011         /*
1012          * Lock device and try to bind to it. We drop the error
1013          * here and always return 0, because we need to keep trying
1014          * to bind to devices and some drivers will return an error
1015          * simply if it didn't support the device.
1016          *
1017          * driver_probe_device() will spit a warning if there
1018          * is an error.
1019          */
1020
1021         ret = driver_match_device(drv, dev);
1022         if (ret == 0) {
1023                 /* no match */
1024                 return 0;
1025         } else if (ret == -EPROBE_DEFER) {
1026                 dev_dbg(dev, "Device match requests probe deferral\n");
1027                 driver_deferred_probe_add(dev);
1028         } else if (ret < 0) {
1029                 dev_dbg(dev, "Bus failed to match device: %d", ret);
1030                 return ret;
1031         } /* ret > 0 means positive match */
1032
1033         if (driver_allows_async_probing(drv)) {
1034                 /*
1035                  * Instead of probing the device synchronously we will
1036                  * probe it asynchronously to allow for more parallelism.
1037                  *
1038                  * We only take the device lock here in order to guarantee
1039                  * that the dev->driver and async_driver fields are protected
1040                  */
1041                 dev_dbg(dev, "probing driver %s asynchronously\n", drv->name);
1042                 device_lock(dev);
1043                 if (!dev->driver) {
1044                         get_device(dev);
1045                         dev->p->async_driver = drv;
1046                         async_schedule_dev(__driver_attach_async_helper, dev);
1047                 }
1048                 device_unlock(dev);
1049                 return 0;
1050         }
1051
1052         device_driver_attach(drv, dev);
1053
1054         return 0;
1055 }
1056
1057 /**
1058  * driver_attach - try to bind driver to devices.
1059  * @drv: driver.
1060  *
1061  * Walk the list of devices that the bus has on it and try to
1062  * match the driver with each one.  If driver_probe_device()
1063  * returns 0 and the @dev->driver is set, we've found a
1064  * compatible pair.
1065  */
1066 int driver_attach(struct device_driver *drv)
1067 {
1068         return bus_for_each_dev(drv->bus, NULL, drv, __driver_attach);
1069 }
1070 EXPORT_SYMBOL_GPL(driver_attach);
1071
1072 /*
1073  * __device_release_driver() must be called with @dev lock held.
1074  * When called for a USB interface, @dev->parent lock must be held as well.
1075  */
1076 static void __device_release_driver(struct device *dev, struct device *parent)
1077 {
1078         struct device_driver *drv;
1079
1080         drv = dev->driver;
1081         if (drv) {
1082                 while (device_links_busy(dev)) {
1083                         __device_driver_unlock(dev, parent);
1084
1085                         device_links_unbind_consumers(dev);
1086
1087                         __device_driver_lock(dev, parent);
1088                         /*
1089                          * A concurrent invocation of the same function might
1090                          * have released the driver successfully while this one
1091                          * was waiting, so check for that.
1092                          */
1093                         if (dev->driver != drv)
1094                                 return;
1095                 }
1096
1097                 pm_runtime_get_sync(dev);
1098                 pm_runtime_clean_up_links(dev);
1099
1100                 driver_sysfs_remove(dev);
1101
1102                 if (dev->bus)
1103                         blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
1104                                                      BUS_NOTIFY_UNBIND_DRIVER,
1105                                                      dev);
1106
1107                 pm_runtime_put_sync(dev);
1108
1109                 device_remove_groups(dev, drv->dev_groups);
1110
1111                 if (dev->bus && dev->bus->remove)
1112                         dev->bus->remove(dev);
1113                 else if (drv->remove)
1114                         drv->remove(dev);
1115
1116                 device_links_driver_cleanup(dev);
1117
1118                 devres_release_all(dev);
1119                 arch_teardown_dma_ops(dev);
1120                 dev->driver = NULL;
1121                 dev_set_drvdata(dev, NULL);
1122                 if (dev->pm_domain && dev->pm_domain->dismiss)
1123                         dev->pm_domain->dismiss(dev);
1124                 pm_runtime_reinit(dev);
1125                 dev_pm_set_driver_flags(dev, 0);
1126
1127                 klist_remove(&dev->p->knode_driver);
1128                 device_pm_check_callbacks(dev);
1129                 if (dev->bus)
1130                         blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
1131                                                      BUS_NOTIFY_UNBOUND_DRIVER,
1132                                                      dev);
1133
1134                 kobject_uevent(&dev->kobj, KOBJ_UNBIND);
1135         }
1136 }
1137
1138 void device_release_driver_internal(struct device *dev,
1139                                     struct device_driver *drv,
1140                                     struct device *parent)
1141 {
1142         __device_driver_lock(dev, parent);
1143
1144         if (!drv || drv == dev->driver)
1145                 __device_release_driver(dev, parent);
1146
1147         __device_driver_unlock(dev, parent);
1148 }
1149
1150 /**
1151  * device_release_driver - manually detach device from driver.
1152  * @dev: device.
1153  *
1154  * Manually detach device from driver.
1155  * When called for a USB interface, @dev->parent lock must be held.
1156  *
1157  * If this function is to be called with @dev->parent lock held, ensure that
1158  * the device's consumers are unbound in advance or that their locks can be
1159  * acquired under the @dev->parent lock.
1160  */
1161 void device_release_driver(struct device *dev)
1162 {
1163         /*
1164          * If anyone calls device_release_driver() recursively from
1165          * within their ->remove callback for the same device, they
1166          * will deadlock right here.
1167          */
1168         device_release_driver_internal(dev, NULL, NULL);
1169 }
1170 EXPORT_SYMBOL_GPL(device_release_driver);
1171
1172 /**
1173  * device_driver_detach - detach driver from a specific device
1174  * @dev: device to detach driver from
1175  *
1176  * Detach driver from device. Will acquire both @dev lock and @dev->parent
1177  * lock if needed.
1178  */
1179 void device_driver_detach(struct device *dev)
1180 {
1181         device_release_driver_internal(dev, NULL, dev->parent);
1182 }
1183
1184 /**
1185  * driver_detach - detach driver from all devices it controls.
1186  * @drv: driver.
1187  */
1188 void driver_detach(struct device_driver *drv)
1189 {
1190         struct device_private *dev_prv;
1191         struct device *dev;
1192
1193         if (driver_allows_async_probing(drv))
1194                 async_synchronize_full();
1195
1196         for (;;) {
1197                 spin_lock(&drv->p->klist_devices.k_lock);
1198                 if (list_empty(&drv->p->klist_devices.k_list)) {
1199                         spin_unlock(&drv->p->klist_devices.k_lock);
1200                         break;
1201                 }
1202                 dev_prv = list_last_entry(&drv->p->klist_devices.k_list,
1203                                      struct device_private,
1204                                      knode_driver.n_node);
1205                 dev = dev_prv->device;
1206                 get_device(dev);
1207                 spin_unlock(&drv->p->klist_devices.k_lock);
1208                 device_release_driver_internal(dev, drv, dev->parent);
1209                 put_device(dev);
1210         }
1211 }