drivers/base/dd.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * drivers/base/dd.c - The core device/driver interactions.
   4  *
   5  * This file contains the (sometimes tricky) code that controls the
   6  * interactions between devices and drivers, which primarily includes
   7  * driver binding and unbinding.
   8  *
   9  * All of this code used to exist in drivers/base/bus.c, but was
  10  * relocated to here in the name of compartmentalization (since it wasn't
  11  * strictly code just for the 'struct bus_type'.
  12  *
  13  * Copyright (c) 2002-5 Patrick Mochel
  14  * Copyright (c) 2002-3 Open Source Development Labs
  15  * Copyright (c) 2007-2009 Greg Kroah-Hartman <[email protected]>
  16  * Copyright (c) 2007-2009 Novell Inc.
  17  */
  18
  19 #include <linux/debugfs.h>
  20 #include <linux/device.h>
  21 #include <linux/delay.h>
  22 #include <linux/dma-map-ops.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 #include <linux/slab.h>
  31
  32 #include "base.h"
  33 #include "power/power.h"
  34
  35 /*
  36  * Deferred Probe infrastructure.
  37  *
  38  * Sometimes driver probe order matters, but the kernel doesn't always have
  39  * dependency information which means some drivers will get probed before a
  40  * resource it depends on is available.  For example, an SDHCI driver may
  41  * first need a GPIO line from an i2c GPIO controller before it can be
  42  * initialized.  If a required resource is not available yet, a driver can
  43  * request probing to be deferred by returning -EPROBE_DEFER from its probe hook
  44  *
  45  * Deferred probe maintains two lists of devices, a pending list and an active
  46  * list.  A driver returning -EPROBE_DEFER causes the device to be added to the
  47  * pending list.  A successful driver probe will trigger moving all devices
  48  * from the pending to the active list so that the workqueue will eventually
  49  * retry them.
  50  *
  51  * The deferred_probe_mutex must be held any time the deferred_probe_*_list
  52  * of the (struct device*)->p->deferred_probe pointers are manipulated
  53  */
  54 static DEFINE_MUTEX(deferred_probe_mutex);
  55 static LIST_HEAD(deferred_probe_pending_list);
  56 static LIST_HEAD(deferred_probe_active_list);
  57 static atomic_t deferred_trigger_count = ATOMIC_INIT(0);
  58 static struct dentry *deferred_devices;
  59 static bool initcalls_done;
  60
  61 /* Save the async probe drivers' name from kernel cmdline */
  62 #define ASYNC_DRV_NAMES_MAX_LEN 256
  63 static char async_probe_drv_names[ASYNC_DRV_NAMES_MAX_LEN];
  64
  65 /*
  66  * In some cases, like suspend to RAM or hibernation, It might be reasonable
  67  * to prohibit probing of devices as it could be unsafe.
  68  * Once defer_all_probes is true all drivers probes will be forcibly deferred.
  69  */
  70 static bool defer_all_probes;
  71
  72 /*
  73  * deferred_probe_work_func() - Retry probing devices in the active list.
  74  */
  75 static void deferred_probe_work_func(struct work_struct *work)
  76 {
  77         struct device *dev;
  78         struct device_private *private;
  79         /*
  80          * This block processes every device in the deferred 'active' list.
  81          * Each device is removed from the active list and passed to
  82          * bus_probe_device() to re-attempt the probe.  The loop continues
  83          * until every device in the active list is removed and retried.
  84          *
  85          * Note: Once the device is removed from the list and the mutex is
  86          * released, it is possible for the device get freed by another thread
  87          * and cause a illegal pointer dereference.  This code uses
  88          * get/put_device() to ensure the device structure cannot disappear
  89          * from under our feet.
  90          */
  91         mutex_lock(&deferred_probe_mutex);
  92         while (!list_empty(&deferred_probe_active_list)) {
  93                 private = list_first_entry(&deferred_probe_active_list,
  94                                         typeof(*dev->p), deferred_probe);
  95                 dev = private->device;
  96                 list_del_init(&private->deferred_probe);
  97
  98                 get_device(dev);
  99
 100                 /*
 101                  * Drop the mutex while probing each device; the probe path may
 102                  * manipulate the deferred list
 103                  */
 104                 mutex_unlock(&deferred_probe_mutex);
 105
 106                 /*
 107                  * Force the device to the end of the dpm_list since
 108                  * the PM code assumes that the order we add things to
 109                  * the list is a good order for suspend but deferred
 110                  * probe makes that very unsafe.
 111                  */
 112                 device_pm_move_to_tail(dev);
 113
 114                 dev_dbg(dev, "Retrying from deferred list\n");
 115                 bus_probe_device(dev);
 116                 mutex_lock(&deferred_probe_mutex);
 117
 118                 put_device(dev);
 119         }
 120         mutex_unlock(&deferred_probe_mutex);
 121 }
 122 static DECLARE_WORK(deferred_probe_work, deferred_probe_work_func);
 123
 124 void driver_deferred_probe_add(struct device *dev)
 125 {
 126         mutex_lock(&deferred_probe_mutex);
 127         if (list_empty(&dev->p->deferred_probe)) {
 128                 dev_dbg(dev, "Added to deferred list\n");
 129                 list_add_tail(&dev->p->deferred_probe, &deferred_probe_pending_list);
 130         }
 131         mutex_unlock(&deferred_probe_mutex);
 132 }
 133
 134 void driver_deferred_probe_del(struct device *dev)
 135 {
 136         mutex_lock(&deferred_probe_mutex);
 137         if (!list_empty(&dev->p->deferred_probe)) {
 138                 dev_dbg(dev, "Removed from deferred list\n");
 139                 list_del_init(&dev->p->deferred_probe);
 140                 kfree(dev->p->deferred_probe_reason);
 141                 dev->p->deferred_probe_reason = NULL;
 142         }
 143         mutex_unlock(&deferred_probe_mutex);
 144 }
 145
 146 static bool driver_deferred_probe_enable = false;
 147 /**
 148  * driver_deferred_probe_trigger() - Kick off re-probing deferred devices
 149  *
 150  * This functions moves all devices from the pending list to the active
 151  * list and schedules the deferred probe workqueue to process them.  It
 152  * should be called anytime a driver is successfully bound to a device.
 153  *
 154  * Note, there is a race condition in multi-threaded probe. In the case where
 155  * more than one device is probing at the same time, it is possible for one
 156  * probe to complete successfully while another is about to defer. If the second
 157  * depends on the first, then it will get put on the pending list after the
 158  * trigger event has already occurred and will be stuck there.
 159  *
 160  * The atomic 'deferred_trigger_count' is used to determine if a successful
 161  * trigger has occurred in the midst of probing a driver. If the trigger count
 162  * changes in the midst of a probe, then deferred processing should be triggered
 163  * again.
 164  */
 165 static void driver_deferred_probe_trigger(void)
 166 {
 167         if (!driver_deferred_probe_enable)
 168                 return;
 169
 170         /*
 171          * A successful probe means that all the devices in the pending list
 172          * should be triggered to be reprobed.  Move all the deferred devices
 173          * into the active list so they can be retried by the workqueue
 174          */
 175         mutex_lock(&deferred_probe_mutex);
 176         atomic_inc(&deferred_trigger_count);
 177         list_splice_tail_init(&deferred_probe_pending_list,
 178                               &deferred_probe_active_list);
 179         mutex_unlock(&deferred_probe_mutex);
 180
 181         /*
 182          * Kick the re-probe thread.  It may already be scheduled, but it is
 183          * safe to kick it again.
 184          */
 185         schedule_work(&deferred_probe_work);
 186 }
 187
 188 /**
 189  * device_block_probing() - Block/defer device's probes
 190  *
 191  *      It will disable probing of devices and defer their probes instead.
 192  */
 193 void device_block_probing(void)
 194 {
 195         defer_all_probes = true;
 196         /* sync with probes to avoid races. */
 197         wait_for_device_probe();
 198 }
 199
 200 /**
 201  * device_unblock_probing() - Unblock/enable device's probes
 202  *
 203  *      It will restore normal behavior and trigger re-probing of deferred
 204  * devices.
 205  */
 206 void device_unblock_probing(void)
 207 {
 208         defer_all_probes = false;
 209         driver_deferred_probe_trigger();
 210 }
 211
 212 /**
 213  * device_set_deferred_probe_reason() - Set defer probe reason message for device
 214  * @dev: the pointer to the struct device
 215  * @vaf: the pointer to va_format structure with message
 216  */
 217 void device_set_deferred_probe_reason(const struct device *dev, struct va_format *vaf)
 218 {
 219         const char *drv = dev_driver_string(dev);
 220
 221         mutex_lock(&deferred_probe_mutex);
 222
 223         kfree(dev->p->deferred_probe_reason);
 224         dev->p->deferred_probe_reason = kasprintf(GFP_KERNEL, "%s: %pV", drv, vaf);
 225
 226         mutex_unlock(&deferred_probe_mutex);
 227 }
 228
 229 /*
 230  * deferred_devs_show() - Show the devices in the deferred probe pending list.
 231  */
 232 static int deferred_devs_show(struct seq_file *s, void *data)
 233 {
 234         struct device_private *curr;
 235
 236         mutex_lock(&deferred_probe_mutex);
 237
 238         list_for_each_entry(curr, &deferred_probe_pending_list, deferred_probe)
 239                 seq_printf(s, "%s\t%s", dev_name(curr->device),
 240                            curr->device->p->deferred_probe_reason ?: "\n");
 241
 242         mutex_unlock(&deferred_probe_mutex);
 243
 244         return 0;
 245 }
 246 DEFINE_SHOW_ATTRIBUTE(deferred_devs);
 247
 248 int driver_deferred_probe_timeout;
 249 EXPORT_SYMBOL_GPL(driver_deferred_probe_timeout);
 250 static DECLARE_WAIT_QUEUE_HEAD(probe_timeout_waitqueue);
 251
 252 static int __init deferred_probe_timeout_setup(char *str)
 253 {
 254         int timeout;
 255
 256         if (!kstrtoint(str, 10, &timeout))
 257                 driver_deferred_probe_timeout = timeout;
 258         return 1;
 259 }
 260 __setup("deferred_probe_timeout=", deferred_probe_timeout_setup);
 261
 262 /**
 263  * driver_deferred_probe_check_state() - Check deferred probe state
 264  * @dev: device to check
 265  *
 266  * Return:
 267  * -ENODEV if initcalls have completed and modules are disabled.
 268  * -ETIMEDOUT if the deferred probe timeout was set and has expired
 269  *  and modules are enabled.
 270  * -EPROBE_DEFER in other cases.
 271  *
 272  * Drivers or subsystems can opt-in to calling this function instead of directly
 273  * returning -EPROBE_DEFER.
 274  */
 275 int driver_deferred_probe_check_state(struct device *dev)
 276 {
 277         if (!IS_ENABLED(CONFIG_MODULES) && initcalls_done) {
 278                 dev_warn(dev, "ignoring dependency for device, assuming no driver\n");
 279                 return -ENODEV;
 280         }
 281
 282         if (!driver_deferred_probe_timeout && initcalls_done) {
 283                 dev_warn(dev, "deferred probe timeout, ignoring dependency\n");
 284                 return -ETIMEDOUT;
 285         }
 286
 287         return -EPROBE_DEFER;
 288 }
 289
 290 static void deferred_probe_timeout_work_func(struct work_struct *work)
 291 {
 292         struct device_private *private, *p;
 293
 294         driver_deferred_probe_timeout = 0;
 295         driver_deferred_probe_trigger();
 296         flush_work(&deferred_probe_work);
 297
 298         list_for_each_entry_safe(private, p, &deferred_probe_pending_list, deferred_probe)
 299                 dev_info(private->device, "deferred probe pending\n");
 300         wake_up_all(&probe_timeout_waitqueue);
 301 }
 302 static DECLARE_DELAYED_WORK(deferred_probe_timeout_work, deferred_probe_timeout_work_func);
 303
 304 /**
 305  * deferred_probe_initcall() - Enable probing of deferred devices
 306  *
 307  * We don't want to get in the way when the bulk of drivers are getting probed.
 308  * Instead, this initcall makes sure that deferred probing is delayed until
 309  * late_initcall time.
 310  */
 311 static int deferred_probe_initcall(void)
 312 {
 313         deferred_devices = debugfs_create_file("devices_deferred", 0444, NULL,
 314                                                NULL, &deferred_devs_fops);
 315
 316         driver_deferred_probe_enable = true;
 317         driver_deferred_probe_trigger();
 318         /* Sort as many dependencies as possible before exiting initcalls */
 319         flush_work(&deferred_probe_work);
 320         initcalls_done = true;
 321
 322         /*
 323          * Trigger deferred probe again, this time we won't defer anything
 324          * that is optional
 325          */
 326         driver_deferred_probe_trigger();
 327         flush_work(&deferred_probe_work);
 328
 329         if (driver_deferred_probe_timeout > 0) {
 330                 schedule_delayed_work(&deferred_probe_timeout_work,
 331                         driver_deferred_probe_timeout * HZ);
 332         }
 333         return 0;
 334 }
 335 late_initcall(deferred_probe_initcall);
 336
 337 static void __exit deferred_probe_exit(void)
 338 {
 339         debugfs_remove_recursive(deferred_devices);
 340 }
 341 __exitcall(deferred_probe_exit);
 342
 343 /**
 344  * device_is_bound() - Check if device is bound to a driver
 345  * @dev: device to check
 346  *
 347  * Returns true if passed device has already finished probing successfully
 348  * against a driver.
 349  *
 350  * This function must be called with the device lock held.
 351  */
 352 bool device_is_bound(struct device *dev)
 353 {
 354         return dev->p && klist_node_attached(&dev->p->knode_driver);
 355 }
 356
 357 static void driver_bound(struct device *dev)
 358 {
 359         if (device_is_bound(dev)) {
 360                 pr_warn("%s: device %s already bound\n",
 361                         __func__, kobject_name(&dev->kobj));
 362                 return;
 363         }
 364
 365         pr_debug("driver: '%s': %s: bound to device '%s'\n", dev->driver->name,
 366                  __func__, dev_name(dev));
 367
 368         klist_add_tail(&dev->p->knode_driver, &dev->driver->p->klist_devices);
 369         device_links_driver_bound(dev);
 370
 371         device_pm_check_callbacks(dev);
 372
 373         /*
 374          * Make sure the device is no longer in one of the deferred lists and
 375          * kick off retrying all pending devices
 376          */
 377         driver_deferred_probe_del(dev);
 378         driver_deferred_probe_trigger();
 379
 380         if (dev->bus)
 381                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 382                                              BUS_NOTIFY_BOUND_DRIVER, dev);
 383
 384         kobject_uevent(&dev->kobj, KOBJ_BIND);
 385 }
 386
 387 static ssize_t coredump_store(struct device *dev, struct device_attribute *attr,
 388                             const char *buf, size_t count)
 389 {
 390         device_lock(dev);
 391         dev->driver->coredump(dev);
 392         device_unlock(dev);
 393
 394         return count;
 395 }
 396 static DEVICE_ATTR_WO(coredump);
 397
 398 static int driver_sysfs_add(struct device *dev)
 399 {
 400         int ret;
 401
 402         if (dev->bus)
 403                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 404                                              BUS_NOTIFY_BIND_DRIVER, dev);
 405
 406         ret = sysfs_create_link(&dev->driver->p->kobj, &dev->kobj,
 407                                 kobject_name(&dev->kobj));
 408         if (ret)
 409                 goto fail;
 410
 411         ret = sysfs_create_link(&dev->kobj, &dev->driver->p->kobj,
 412                                 "driver");
 413         if (ret)
 414                 goto rm_dev;
 415
 416         if (!IS_ENABLED(CONFIG_DEV_COREDUMP) || !dev->driver->coredump ||
 417             !device_create_file(dev, &dev_attr_coredump))
 418                 return 0;
 419
 420         sysfs_remove_link(&dev->kobj, "driver");
 421
 422 rm_dev:
 423         sysfs_remove_link(&dev->driver->p->kobj,
 424                           kobject_name(&dev->kobj));
 425
 426 fail:
 427         return ret;
 428 }
 429
 430 static void driver_sysfs_remove(struct device *dev)
 431 {
 432         struct device_driver *drv = dev->driver;
 433
 434         if (drv) {
 435                 if (drv->coredump)
 436                         device_remove_file(dev, &dev_attr_coredump);
 437                 sysfs_remove_link(&drv->p->kobj, kobject_name(&dev->kobj));
 438                 sysfs_remove_link(&dev->kobj, "driver");
 439         }
 440 }
 441
 442 /**
 443  * device_bind_driver - bind a driver to one device.
 444  * @dev: device.
 445  *
 446  * Allow manual attachment of a driver to a device.
 447  * Caller must have already set @dev->driver.
 448  *
 449  * Note that this does not modify the bus reference count.
 450  * Please verify that is accounted for before calling this.
 451  * (It is ok to call with no other effort from a driver's probe() method.)
 452  *
 453  * This function must be called with the device lock held.
 454  */
 455 int device_bind_driver(struct device *dev)
 456 {
 457         int ret;
 458
 459         ret = driver_sysfs_add(dev);
 460         if (!ret)
 461                 driver_bound(dev);
 462         else if (dev->bus)
 463                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 464                                              BUS_NOTIFY_DRIVER_NOT_BOUND, dev);
 465         return ret;
 466 }
 467 EXPORT_SYMBOL_GPL(device_bind_driver);
 468
 469 static atomic_t probe_count = ATOMIC_INIT(0);
 470 static DECLARE_WAIT_QUEUE_HEAD(probe_waitqueue);
 471
 472 static void driver_deferred_probe_add_trigger(struct device *dev,
 473                                               int local_trigger_count)
 474 {
 475         driver_deferred_probe_add(dev);
 476         /* Did a trigger occur while probing? Need to re-trigger if yes */
 477         if (local_trigger_count != atomic_read(&deferred_trigger_count))
 478                 driver_deferred_probe_trigger();
 479 }
 480
 481 static ssize_t state_synced_show(struct device *dev,
 482                                  struct device_attribute *attr, char *buf)
 483 {
 484         bool val;
 485
 486         device_lock(dev);
 487         val = dev->state_synced;
 488         device_unlock(dev);
 489
 490         return sysfs_emit(buf, "%u\n", val);
 491 }
 492 static DEVICE_ATTR_RO(state_synced);
 493
 494 static int really_probe(struct device *dev, struct device_driver *drv)
 495 {
 496         int ret = -EPROBE_DEFER;
 497         int local_trigger_count = atomic_read(&deferred_trigger_count);
 498         bool test_remove = IS_ENABLED(CONFIG_DEBUG_TEST_DRIVER_REMOVE) &&
 499                            !drv->suppress_bind_attrs;
 500
 501         if (defer_all_probes) {
 502                 /*
 503                  * Value of defer_all_probes can be set only by
 504                  * device_block_probing() which, in turn, will call
 505                  * wait_for_device_probe() right after that to avoid any races.
 506                  */
 507                 dev_dbg(dev, "Driver %s force probe deferral\n", drv->name);
 508                 driver_deferred_probe_add(dev);
 509                 return ret;
 510         }
 511
 512         ret = device_links_check_suppliers(dev);
 513         if (ret == -EPROBE_DEFER)
 514                 driver_deferred_probe_add_trigger(dev, local_trigger_count);
 515         if (ret)
 516                 return ret;
 517
 518         atomic_inc(&probe_count);
 519         pr_debug("bus: '%s': %s: probing driver %s with device %s\n",
 520                  drv->bus->name, __func__, drv->name, dev_name(dev));
 521         if (!list_empty(&dev->devres_head)) {
 522                 dev_crit(dev, "Resources present before probing\n");
 523                 ret = -EBUSY;
 524                 goto done;
 525         }
 526
 527 re_probe:
 528         dev->driver = drv;
 529
 530         /* If using pinctrl, bind pins now before probing */
 531         ret = pinctrl_bind_pins(dev);
 532         if (ret)
 533                 goto pinctrl_bind_failed;
 534
 535         if (dev->bus->dma_configure) {
 536                 ret = dev->bus->dma_configure(dev);
 537                 if (ret)
 538                         goto probe_failed;
 539         }
 540
 541         if (driver_sysfs_add(dev)) {
 542                 pr_err("%s: driver_sysfs_add(%s) failed\n",
 543                        __func__, dev_name(dev));
 544                 goto probe_failed;
 545         }
 546
 547         if (dev->pm_domain && dev->pm_domain->activate) {
 548                 ret = dev->pm_domain->activate(dev);
 549                 if (ret)
 550                         goto probe_failed;
 551         }
 552
 553         if (dev->bus->probe) {
 554                 ret = dev->bus->probe(dev);
 555                 if (ret)
 556                         goto probe_failed;
 557         } else if (drv->probe) {
 558                 ret = drv->probe(dev);
 559                 if (ret)
 560                         goto probe_failed;
 561         }
 562
 563         if (device_add_groups(dev, drv->dev_groups)) {
 564                 dev_err(dev, "device_add_groups() failed\n");
 565                 goto dev_groups_failed;
 566         }
 567
 568         if (dev_has_sync_state(dev) &&
 569             device_create_file(dev, &dev_attr_state_synced)) {
 570                 dev_err(dev, "state_synced sysfs add failed\n");
 571                 goto dev_sysfs_state_synced_failed;
 572         }
 573
 574         if (test_remove) {
 575                 test_remove = false;
 576
 577                 device_remove_file(dev, &dev_attr_state_synced);
 578                 device_remove_groups(dev, drv->dev_groups);
 579
 580                 if (dev->bus->remove)
 581                         dev->bus->remove(dev);
 582                 else if (drv->remove)
 583                         drv->remove(dev);
 584
 585                 devres_release_all(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
 593                 goto re_probe;
 594         }
 595
 596         pinctrl_init_done(dev);
 597
 598         if (dev->pm_domain && dev->pm_domain->sync)
 599                 dev->pm_domain->sync(dev);
 600
 601         driver_bound(dev);
 602         ret = 1;
 603         pr_debug("bus: '%s': %s: bound device %s to driver %s\n",
 604                  drv->bus->name, __func__, dev_name(dev), drv->name);
 605         goto done;
 606
 607 dev_sysfs_state_synced_failed:
 608         device_remove_groups(dev, drv->dev_groups);
 609 dev_groups_failed:
 610         if (dev->bus->remove)
 611                 dev->bus->remove(dev);
 612         else if (drv->remove)
 613                 drv->remove(dev);
 614 probe_failed:
 615         if (dev->bus)
 616                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 617                                              BUS_NOTIFY_DRIVER_NOT_BOUND, dev);
 618 pinctrl_bind_failed:
 619         device_links_no_driver(dev);
 620         devres_release_all(dev);
 621         arch_teardown_dma_ops(dev);
 622         driver_sysfs_remove(dev);
 623         dev->driver = NULL;
 624         dev_set_drvdata(dev, NULL);
 625         if (dev->pm_domain && dev->pm_domain->dismiss)
 626                 dev->pm_domain->dismiss(dev);
 627         pm_runtime_reinit(dev);
 628         dev_pm_set_driver_flags(dev, 0);
 629
 630         switch (ret) {
 631         case -EPROBE_DEFER:
 632                 /* Driver requested deferred probing */
 633                 dev_dbg(dev, "Driver %s requests probe deferral\n", drv->name);
 634                 driver_deferred_probe_add_trigger(dev, local_trigger_count);
 635                 break;
 636         case -ENODEV:
 637         case -ENXIO:
 638                 pr_debug("%s: probe of %s rejects match %d\n",
 639                          drv->name, dev_name(dev), ret);
 640                 break;
 641         default:
 642                 /* driver matched but the probe failed */
 643                 pr_warn("%s: probe of %s failed with error %d\n",
 644                         drv->name, dev_name(dev), ret);
 645         }
 646         /*
 647          * Ignore errors returned by ->probe so that the next driver can try
 648          * its luck.
 649          */
 650         ret = 0;
 651 done:
 652         atomic_dec(&probe_count);
 653         wake_up_all(&probe_waitqueue);
 654         return ret;
 655 }
 656
 657 /*
 658  * For initcall_debug, show the driver probe time.
 659  */
 660 static int really_probe_debug(struct device *dev, struct device_driver *drv)
 661 {
 662         ktime_t calltime, rettime;
 663         int ret;
 664
 665         calltime = ktime_get();
 666         ret = really_probe(dev, drv);
 667         rettime = ktime_get();
 668         pr_debug("probe of %s returned %d after %lld usecs\n",
 669                  dev_name(dev), ret, ktime_us_delta(rettime, calltime));
 670         return ret;
 671 }
 672
 673 /**
 674  * driver_probe_done
 675  * Determine if the probe sequence is finished or not.
 676  *
 677  * Should somehow figure out how to use a semaphore, not an atomic variable...
 678  */
 679 int driver_probe_done(void)
 680 {
 681         int local_probe_count = atomic_read(&probe_count);
 682
 683         pr_debug("%s: probe_count = %d\n", __func__, local_probe_count);
 684         if (local_probe_count)
 685                 return -EBUSY;
 686         return 0;
 687 }
 688
 689 /**
 690  * wait_for_device_probe
 691  * Wait for device probing to be completed.
 692  */
 693 void wait_for_device_probe(void)
 694 {
 695         /* wait for probe timeout */
 696         wait_event(probe_timeout_waitqueue, !driver_deferred_probe_timeout);
 697
 698         /* wait for the deferred probe workqueue to finish */
 699         flush_work(&deferred_probe_work);
 700
 701         /* wait for the known devices to complete their probing */
 702         wait_event(probe_waitqueue, atomic_read(&probe_count) == 0);
 703         async_synchronize_full();
 704 }
 705 EXPORT_SYMBOL_GPL(wait_for_device_probe);
 706
 707 /**
 708  * driver_probe_device - attempt to bind device & driver together
 709  * @drv: driver to bind a device to
 710  * @dev: device to try to bind to the driver
 711  *
 712  * This function returns -ENODEV if the device is not registered,
 713  * 1 if the device is bound successfully and 0 otherwise.
 714  *
 715  * This function must be called with @dev lock held.  When called for a
 716  * USB interface, @dev->parent lock must be held as well.
 717  *
 718  * If the device has a parent, runtime-resume the parent before driver probing.
 719  */
 720 int driver_probe_device(struct device_driver *drv, struct device *dev)
 721 {
 722         int ret = 0;
 723
 724         if (!device_is_registered(dev))
 725                 return -ENODEV;
 726
 727         pr_debug("bus: '%s': %s: matched device %s with driver %s\n",
 728                  drv->bus->name, __func__, dev_name(dev), drv->name);
 729
 730         pm_runtime_get_suppliers(dev);
 731         if (dev->parent)
 732                 pm_runtime_get_sync(dev->parent);
 733
 734         pm_runtime_barrier(dev);
 735         if (initcall_debug)
 736                 ret = really_probe_debug(dev, drv);
 737         else
 738                 ret = really_probe(dev, drv);
 739         pm_request_idle(dev);
 740
 741         if (dev->parent)
 742                 pm_runtime_put(dev->parent);
 743
 744         pm_runtime_put_suppliers(dev);
 745         return ret;
 746 }
 747
 748 static inline bool cmdline_requested_async_probing(const char *drv_name)
 749 {
 750         return parse_option_str(async_probe_drv_names, drv_name);
 751 }
 752
 753 /* The option format is "driver_async_probe=drv_name1,drv_name2,..." */
 754 static int __init save_async_options(char *buf)
 755 {
 756         if (strlen(buf) >= ASYNC_DRV_NAMES_MAX_LEN)
 757                 pr_warn("Too long list of driver names for 'driver_async_probe'!\n");
 758
 759         strlcpy(async_probe_drv_names, buf, ASYNC_DRV_NAMES_MAX_LEN);
 760         return 0;
 761 }
 762 __setup("driver_async_probe=", save_async_options);
 763
 764 bool driver_allows_async_probing(struct device_driver *drv)
 765 {
 766         switch (drv->probe_type) {
 767         case PROBE_PREFER_ASYNCHRONOUS:
 768                 return true;
 769
 770         case PROBE_FORCE_SYNCHRONOUS:
 771                 return false;
 772
 773         default:
 774                 if (cmdline_requested_async_probing(drv->name))
 775                         return true;
 776
 777                 if (module_requested_async_probing(drv->owner))
 778                         return true;
 779
 780                 return false;
 781         }
 782 }
 783
 784 struct device_attach_data {
 785         struct device *dev;
 786
 787         /*
 788          * Indicates whether we are are considering asynchronous probing or
 789          * not. Only initial binding after device or driver registration
 790          * (including deferral processing) may be done asynchronously, the
 791          * rest is always synchronous, as we expect it is being done by
 792          * request from userspace.
 793          */
 794         bool check_async;
 795
 796         /*
 797          * Indicates if we are binding synchronous or asynchronous drivers.
 798          * When asynchronous probing is enabled we'll execute 2 passes
 799          * over drivers: first pass doing synchronous probing and second
 800          * doing asynchronous probing (if synchronous did not succeed -
 801          * most likely because there was no driver requiring synchronous
 802          * probing - and we found asynchronous driver during first pass).
 803          * The 2 passes are done because we can't shoot asynchronous
 804          * probe for given device and driver from bus_for_each_drv() since
 805          * driver pointer is not guaranteed to stay valid once
 806          * bus_for_each_drv() iterates to the next driver on the bus.
 807          */
 808         bool want_async;
 809
 810         /*
 811          * We'll set have_async to 'true' if, while scanning for matching
 812          * driver, we'll encounter one that requests asynchronous probing.
 813          */
 814         bool have_async;
 815 };
 816
 817 static int __device_attach_driver(struct device_driver *drv, void *_data)
 818 {
 819         struct device_attach_data *data = _data;
 820         struct device *dev = data->dev;
 821         bool async_allowed;
 822         int ret;
 823
 824         ret = driver_match_device(drv, dev);
 825         if (ret == 0) {
 826                 /* no match */
 827                 return 0;
 828         } else if (ret == -EPROBE_DEFER) {
 829                 dev_dbg(dev, "Device match requests probe deferral\n");
 830                 driver_deferred_probe_add(dev);
 831         } else if (ret < 0) {
 832                 dev_dbg(dev, "Bus failed to match device: %d\n", ret);
 833                 return ret;
 834         } /* ret > 0 means positive match */
 835
 836         async_allowed = driver_allows_async_probing(drv);
 837
 838         if (async_allowed)
 839                 data->have_async = true;
 840
 841         if (data->check_async && async_allowed != data->want_async)
 842                 return 0;
 843
 844         return driver_probe_device(drv, dev);
 845 }
 846
 847 static void __device_attach_async_helper(void *_dev, async_cookie_t cookie)
 848 {
 849         struct device *dev = _dev;
 850         struct device_attach_data data = {
 851                 .dev            = dev,
 852                 .check_async    = true,
 853                 .want_async     = true,
 854         };
 855
 856         device_lock(dev);
 857
 858         /*
 859          * Check if device has already been removed or claimed. This may
 860          * happen with driver loading, device discovery/registration,
 861          * and deferred probe processing happens all at once with
 862          * multiple threads.
 863          */
 864         if (dev->p->dead || dev->driver)
 865                 goto out_unlock;
 866
 867         if (dev->parent)
 868                 pm_runtime_get_sync(dev->parent);
 869
 870         bus_for_each_drv(dev->bus, NULL, &data, __device_attach_driver);
 871         dev_dbg(dev, "async probe completed\n");
 872
 873         pm_request_idle(dev);
 874
 875         if (dev->parent)
 876                 pm_runtime_put(dev->parent);
 877 out_unlock:
 878         device_unlock(dev);
 879
 880         put_device(dev);
 881 }
 882
 883 static int __device_attach(struct device *dev, bool allow_async)
 884 {
 885         int ret = 0;
 886
 887         device_lock(dev);
 888         if (dev->p->dead) {
 889                 goto out_unlock;
 890         } else if (dev->driver) {
 891                 if (device_is_bound(dev)) {
 892                         ret = 1;
 893                         goto out_unlock;
 894                 }
 895                 ret = device_bind_driver(dev);
 896                 if (ret == 0)
 897                         ret = 1;
 898                 else {
 899                         dev->driver = NULL;
 900                         ret = 0;
 901                 }
 902         } else {
 903                 struct device_attach_data data = {
 904                         .dev = dev,
 905                         .check_async = allow_async,
 906                         .want_async = false,
 907                 };
 908
 909                 if (dev->parent)
 910                         pm_runtime_get_sync(dev->parent);
 911
 912                 ret = bus_for_each_drv(dev->bus, NULL, &data,
 913                                         __device_attach_driver);
 914                 if (!ret && allow_async && data.have_async) {
 915                         /*
 916                          * If we could not find appropriate driver
 917                          * synchronously and we are allowed to do
 918                          * async probes and there are drivers that
 919                          * want to probe asynchronously, we'll
 920                          * try them.
 921                          */
 922                         dev_dbg(dev, "scheduling asynchronous probe\n");
 923                         get_device(dev);
 924                         async_schedule_dev(__device_attach_async_helper, dev);
 925                 } else {
 926                         pm_request_idle(dev);
 927                 }
 928
 929                 if (dev->parent)
 930                         pm_runtime_put(dev->parent);
 931         }
 932 out_unlock:
 933         device_unlock(dev);
 934         return ret;
 935 }
 936
 937 /**
 938  * device_attach - try to attach device to a driver.
 939  * @dev: device.
 940  *
 941  * Walk the list of drivers that the bus has and call
 942  * driver_probe_device() for each pair. If a compatible
 943  * pair is found, break out and return.
 944  *
 945  * Returns 1 if the device was bound to a driver;
 946  * 0 if no matching driver was found;
 947  * -ENODEV if the device is not registered.
 948  *
 949  * When called for a USB interface, @dev->parent lock must be held.
 950  */
 951 int device_attach(struct device *dev)
 952 {
 953         return __device_attach(dev, false);
 954 }
 955 EXPORT_SYMBOL_GPL(device_attach);
 956
 957 void device_initial_probe(struct device *dev)
 958 {
 959         __device_attach(dev, true);
 960 }
 961
 962 /*
 963  * __device_driver_lock - acquire locks needed to manipulate dev->drv
 964  * @dev: Device we will update driver info for
 965  * @parent: Parent device. Needed if the bus requires parent lock
 966  *
 967  * This function will take the required locks for manipulating dev->drv.
 968  * Normally this will just be the @dev lock, but when called for a USB
 969  * interface, @parent lock will be held as well.
 970  */
 971 static void __device_driver_lock(struct device *dev, struct device *parent)
 972 {
 973         if (parent && dev->bus->need_parent_lock)
 974                 device_lock(parent);
 975         device_lock(dev);
 976 }
 977
 978 /*
 979  * __device_driver_unlock - release locks needed to manipulate dev->drv
 980  * @dev: Device we will update driver info for
 981  * @parent: Parent device. Needed if the bus requires parent lock
 982  *
 983  * This function will release the required locks for manipulating dev->drv.
 984  * Normally this will just be the the @dev lock, but when called for a
 985  * USB interface, @parent lock will be released as well.
 986  */
 987 static void __device_driver_unlock(struct device *dev, struct device *parent)
 988 {
 989         device_unlock(dev);
 990         if (parent && dev->bus->need_parent_lock)
 991                 device_unlock(parent);
 992 }
 993
 994 /**
 995  * device_driver_attach - attach a specific driver to a specific device
 996  * @drv: Driver to attach
 997  * @dev: Device to attach it to
 998  *
 999  * Manually attach driver to a device. Will acquire both @dev lock and
1000  * @dev->parent lock if needed.
1001  */
1002 int device_driver_attach(struct device_driver *drv, struct device *dev)
1003 {
1004         int ret = 0;
1005
1006         __device_driver_lock(dev, dev->parent);
1007
1008         /*
1009          * If device has been removed or someone has already successfully
1010          * bound a driver before us just skip the driver probe call.
1011          */
1012         if (!dev->p->dead && !dev->driver)
1013                 ret = driver_probe_device(drv, dev);
1014
1015         __device_driver_unlock(dev, dev->parent);
1016
1017         return ret;
1018 }
1019
1020 static void __driver_attach_async_helper(void *_dev, async_cookie_t cookie)
1021 {
1022         struct device *dev = _dev;
1023         struct device_driver *drv;
1024         int ret = 0;
1025
1026         __device_driver_lock(dev, dev->parent);
1027
1028         drv = dev->p->async_driver;
1029
1030         /*
1031          * If device has been removed or someone has already successfully
1032          * bound a driver before us just skip the driver probe call.
1033          */
1034         if (!dev->p->dead && !dev->driver)
1035                 ret = driver_probe_device(drv, dev);
1036
1037         __device_driver_unlock(dev, dev->parent);
1038
1039         dev_dbg(dev, "driver %s async attach completed: %d\n", drv->name, ret);
1040
1041         put_device(dev);
1042 }
1043
1044 static int __driver_attach(struct device *dev, void *data)
1045 {
1046         struct device_driver *drv = data;
1047         int ret;
1048
1049         /*
1050          * Lock device and try to bind to it. We drop the error
1051          * here and always return 0, because we need to keep trying
1052          * to bind to devices and some drivers will return an error
1053          * simply if it didn't support the device.
1054          *
1055          * driver_probe_device() will spit a warning if there
1056          * is an error.
1057          */
1058
1059         ret = driver_match_device(drv, dev);
1060         if (ret == 0) {
1061                 /* no match */
1062                 return 0;
1063         } else if (ret == -EPROBE_DEFER) {
1064                 dev_dbg(dev, "Device match requests probe deferral\n");
1065                 driver_deferred_probe_add(dev);
1066         } else if (ret < 0) {
1067                 dev_dbg(dev, "Bus failed to match device: %d\n", ret);
1068                 return ret;
1069         } /* ret > 0 means positive match */
1070
1071         if (driver_allows_async_probing(drv)) {
1072                 /*
1073                  * Instead of probing the device synchronously we will
1074                  * probe it asynchronously to allow for more parallelism.
1075                  *
1076                  * We only take the device lock here in order to guarantee
1077                  * that the dev->driver and async_driver fields are protected
1078                  */
1079                 dev_dbg(dev, "probing driver %s asynchronously\n", drv->name);
1080                 device_lock(dev);
1081                 if (!dev->driver) {
1082                         get_device(dev);
1083                         dev->p->async_driver = drv;
1084                         async_schedule_dev(__driver_attach_async_helper, dev);
1085                 }
1086                 device_unlock(dev);
1087                 return 0;
1088         }
1089
1090         device_driver_attach(drv, dev);
1091
1092         return 0;
1093 }
1094
1095 /**
1096  * driver_attach - try to bind driver to devices.
1097  * @drv: driver.
1098  *
1099  * Walk the list of devices that the bus has on it and try to
1100  * match the driver with each one.  If driver_probe_device()
1101  * returns 0 and the @dev->driver is set, we've found a
1102  * compatible pair.
1103  */
1104 int driver_attach(struct device_driver *drv)
1105 {
1106         return bus_for_each_dev(drv->bus, NULL, drv, __driver_attach);
1107 }
1108 EXPORT_SYMBOL_GPL(driver_attach);
1109
1110 /*
1111  * __device_release_driver() must be called with @dev lock held.
1112  * When called for a USB interface, @dev->parent lock must be held as well.
1113  */
1114 static void __device_release_driver(struct device *dev, struct device *parent)
1115 {
1116         struct device_driver *drv;
1117
1118         drv = dev->driver;
1119         if (drv) {
1120                 while (device_links_busy(dev)) {
1121                         __device_driver_unlock(dev, parent);
1122
1123                         device_links_unbind_consumers(dev);
1124
1125                         __device_driver_lock(dev, parent);
1126                         /*
1127                          * A concurrent invocation of the same function might
1128                          * have released the driver successfully while this one
1129                          * was waiting, so check for that.
1130                          */
1131                         if (dev->driver != drv)
1132                                 return;
1133                 }
1134
1135                 pm_runtime_get_sync(dev);
1136                 pm_runtime_clean_up_links(dev);
1137
1138                 driver_sysfs_remove(dev);
1139
1140                 if (dev->bus)
1141                         blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
1142                                                      BUS_NOTIFY_UNBIND_DRIVER,
1143                                                      dev);
1144
1145                 pm_runtime_put_sync(dev);
1146
1147                 device_remove_file(dev, &dev_attr_state_synced);
1148                 device_remove_groups(dev, drv->dev_groups);
1149
1150                 if (dev->bus && dev->bus->remove)
1151                         dev->bus->remove(dev);
1152                 else if (drv->remove)
1153                         drv->remove(dev);
1154
1155                 device_links_driver_cleanup(dev);
1156
1157                 devres_release_all(dev);
1158                 arch_teardown_dma_ops(dev);
1159                 dev->driver = NULL;
1160                 dev_set_drvdata(dev, NULL);
1161                 if (dev->pm_domain && dev->pm_domain->dismiss)
1162                         dev->pm_domain->dismiss(dev);
1163                 pm_runtime_reinit(dev);
1164                 dev_pm_set_driver_flags(dev, 0);
1165
1166                 klist_remove(&dev->p->knode_driver);
1167                 device_pm_check_callbacks(dev);
1168                 if (dev->bus)
1169                         blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
1170                                                      BUS_NOTIFY_UNBOUND_DRIVER,
1171                                                      dev);
1172
1173                 kobject_uevent(&dev->kobj, KOBJ_UNBIND);
1174         }
1175 }
1176
1177 void device_release_driver_internal(struct device *dev,
1178                                     struct device_driver *drv,
1179                                     struct device *parent)
1180 {
1181         __device_driver_lock(dev, parent);
1182
1183         if (!drv || drv == dev->driver)
1184                 __device_release_driver(dev, parent);
1185
1186         __device_driver_unlock(dev, parent);
1187 }
1188
1189 /**
1190  * device_release_driver - manually detach device from driver.
1191  * @dev: device.
1192  *
1193  * Manually detach device from driver.
1194  * When called for a USB interface, @dev->parent lock must be held.
1195  *
1196  * If this function is to be called with @dev->parent lock held, ensure that
1197  * the device's consumers are unbound in advance or that their locks can be
1198  * acquired under the @dev->parent lock.
1199  */
1200 void device_release_driver(struct device *dev)
1201 {
1202         /*
1203          * If anyone calls device_release_driver() recursively from
1204          * within their ->remove callback for the same device, they
1205          * will deadlock right here.
1206          */
1207         device_release_driver_internal(dev, NULL, NULL);
1208 }
1209 EXPORT_SYMBOL_GPL(device_release_driver);
1210
1211 /**
1212  * device_driver_detach - detach driver from a specific device
1213  * @dev: device to detach driver from
1214  *
1215  * Detach driver from device. Will acquire both @dev lock and @dev->parent
1216  * lock if needed.
1217  */
1218 void device_driver_detach(struct device *dev)
1219 {
1220         device_release_driver_internal(dev, NULL, dev->parent);
1221 }
1222
1223 /**
1224  * driver_detach - detach driver from all devices it controls.
1225  * @drv: driver.
1226  */
1227 void driver_detach(struct device_driver *drv)
1228 {
1229         struct device_private *dev_prv;
1230         struct device *dev;
1231
1232         if (driver_allows_async_probing(drv))
1233                 async_synchronize_full();
1234
1235         for (;;) {
1236                 spin_lock(&drv->p->klist_devices.k_lock);
1237                 if (list_empty(&drv->p->klist_devices.k_list)) {
1238                         spin_unlock(&drv->p->klist_devices.k_lock);
1239                         break;
1240                 }
1241                 dev_prv = list_last_entry(&drv->p->klist_devices.k_list,
1242                                      struct device_private,
1243                                      knode_driver.n_node);
1244                 dev = dev_prv->device;
1245                 get_device(dev);
1246                 spin_unlock(&drv->p->klist_devices.k_lock);
1247                 device_release_driver_internal(dev, drv, dev->parent);
1248                 put_device(dev);
1249         }
1250 }