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