drivers/base/dd.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * drivers/base/dd.c - The core device/driver interactions.
   4  *
   5  * This file contains the (sometimes tricky) code that controls the
   6  * interactions between devices and drivers, which primarily includes
   7  * driver binding and unbinding.
   8  *
   9  * All of this code used to exist in drivers/base/bus.c, but was
  10  * relocated to here in the name of compartmentalization (since it wasn't
  11  * strictly code just for the 'struct bus_type'.
  12  *
  13  * Copyright (c) 2002-5 Patrick Mochel
  14  * Copyright (c) 2002-3 Open Source Development Labs
  15  * Copyright (c) 2007-2009 Greg Kroah-Hartman <gregkh@suse.de>
  16  * Copyright (c) 2007-2009 Novell Inc.
  17  */
  18
  19 #include <linux/debugfs.h>
  20 #include <linux/device.h>
  21 #include <linux/delay.h>
  22 #include <linux/dma-mapping.h>
  23 #include <linux/init.h>
  24 #include <linux/module.h>
  25 #include <linux/kthread.h>
  26 #include <linux/wait.h>
  27 #include <linux/async.h>
  28 #include <linux/pm_runtime.h>
  29 #include <linux/pinctrl/devinfo.h>
  30
  31 #include "base.h"
  32 #include "power/power.h"
  33
  34 /*
  35  * Deferred Probe infrastructure.
  36  *
  37  * Sometimes driver probe order matters, but the kernel doesn't always have
  38  * dependency information which means some drivers will get probed before a
  39  * resource it depends on is available.  For example, an SDHCI driver may
  40  * first need a GPIO line from an i2c GPIO controller before it can be
  41  * initialized.  If a required resource is not available yet, a driver can
  42  * request probing to be deferred by returning -EPROBE_DEFER from its probe hook
  43  *
  44  * Deferred probe maintains two lists of devices, a pending list and an active
  45  * list.  A driver returning -EPROBE_DEFER causes the device to be added to the
  46  * pending list.  A successful driver probe will trigger moving all devices
  47  * from the pending to the active list so that the workqueue will eventually
  48  * retry them.
  49  *
  50  * The deferred_probe_mutex must be held any time the deferred_probe_*_list
  51  * of the (struct device*)->p->deferred_probe pointers are manipulated
  52  */
  53 static DEFINE_MUTEX(deferred_probe_mutex);
  54 static LIST_HEAD(deferred_probe_pending_list);
  55 static LIST_HEAD(deferred_probe_active_list);
  56 static atomic_t deferred_trigger_count = ATOMIC_INIT(0);
  57 static struct dentry *deferred_devices;
  58 static bool initcalls_done;
  59
  60 /* Save the async probe drivers' name from kernel cmdline */
  61 #define ASYNC_DRV_NAMES_MAX_LEN 256
  62 static char async_probe_drv_names[ASYNC_DRV_NAMES_MAX_LEN];
  63
  64 /*
  65  * In some cases, like suspend to RAM or hibernation, It might be reasonable
  66  * to prohibit probing of devices as it could be unsafe.
  67  * Once defer_all_probes is true all drivers probes will be forcibly deferred.
  68  */
  69 static bool defer_all_probes;
  70
  71 /*
  72  * deferred_probe_work_func() - Retry probing devices in the active list.
  73  */
  74 static void deferred_probe_work_func(struct work_struct *work)
  75 {
  76         struct device *dev;
  77         struct device_private *private;
  78         /*
  79          * This block processes every device in the deferred 'active' list.
  80          * Each device is removed from the active list and passed to
  81          * bus_probe_device() to re-attempt the probe.  The loop continues
  82          * until every device in the active list is removed and retried.
  83          *
  84          * Note: Once the device is removed from the list and the mutex is
  85          * released, it is possible for the device get freed by another thread
  86          * and cause a illegal pointer dereference.  This code uses
  87          * get/put_device() to ensure the device structure cannot disappear
  88          * from under our feet.
  89          */
  90         mutex_lock(&deferred_probe_mutex);
  91         while (!list_empty(&deferred_probe_active_list)) {
  92                 private = list_first_entry(&deferred_probe_active_list,
  93                                         typeof(*dev->p), deferred_probe);
  94                 dev = private->device;
  95                 list_del_init(&private->deferred_probe);
  96
  97                 get_device(dev);
  98
  99                 /*
 100                  * Drop the mutex while probing each device; the probe path may
 101                  * manipulate the deferred list
 102                  */
 103                 mutex_unlock(&deferred_probe_mutex);
 104
 105                 /*
 106                  * Force the device to the end of the dpm_list since
 107                  * the PM code assumes that the order we add things to
 108                  * the list is a good order for suspend but deferred
 109                  * probe makes that very unsafe.
 110                  */
 111                 device_pm_move_to_tail(dev);
 112
 113                 dev_dbg(dev, "Retrying from deferred list\n");
 114                 bus_probe_device(dev);
 115                 mutex_lock(&deferred_probe_mutex);
 116
 117                 put_device(dev);
 118         }
 119         mutex_unlock(&deferred_probe_mutex);
 120 }
 121 static DECLARE_WORK(deferred_probe_work, deferred_probe_work_func);
 122
 123 void driver_deferred_probe_add(struct device *dev)
 124 {
 125         mutex_lock(&deferred_probe_mutex);
 126         if (list_empty(&dev->p->deferred_probe)) {
 127                 dev_dbg(dev, "Added to deferred list\n");
 128                 list_add_tail(&dev->p->deferred_probe, &deferred_probe_pending_list);
 129         }
 130         mutex_unlock(&deferred_probe_mutex);
 131 }
 132
 133 void driver_deferred_probe_del(struct device *dev)
 134 {
 135         mutex_lock(&deferred_probe_mutex);
 136         if (!list_empty(&dev->p->deferred_probe)) {
 137                 dev_dbg(dev, "Removed from deferred list\n");
 138                 list_del_init(&dev->p->deferred_probe);
 139         }
 140         mutex_unlock(&deferred_probe_mutex);
 141 }
 142
 143 static bool driver_deferred_probe_enable = false;
 144 /**
 145  * driver_deferred_probe_trigger() - Kick off re-probing deferred devices
 146  *
 147  * This functions moves all devices from the pending list to the active
 148  * list and schedules the deferred probe workqueue to process them.  It
 149  * should be called anytime a driver is successfully bound to a device.
 150  *
 151  * Note, there is a race condition in multi-threaded probe. In the case where
 152  * more than one device is probing at the same time, it is possible for one
 153  * probe to complete successfully while another is about to defer. If the second
 154  * depends on the first, then it will get put on the pending list after the
 155  * trigger event has already occurred and will be stuck there.
 156  *
 157  * The atomic 'deferred_trigger_count' is used to determine if a successful
 158  * trigger has occurred in the midst of probing a driver. If the trigger count
 159  * changes in the midst of a probe, then deferred processing should be triggered
 160  * again.
 161  */
 162 static void driver_deferred_probe_trigger(void)
 163 {
 164         if (!driver_deferred_probe_enable)
 165                 return;
 166
 167         driver_deferred_probe_force_trigger();
 168 }
 169
 170 void driver_deferred_probe_force_trigger(void)
 171 {
 172         /*
 173          * A successful probe means that all the devices in the pending list
 174          * should be triggered to be reprobed.  Move all the deferred devices
 175          * into the active list so they can be retried by the workqueue
 176          */
 177         mutex_lock(&deferred_probe_mutex);
 178         atomic_inc(&deferred_trigger_count);
 179         list_splice_tail_init(&deferred_probe_pending_list,
 180                               &deferred_probe_active_list);
 181         mutex_unlock(&deferred_probe_mutex);
 182
 183         /*
 184          * Kick the re-probe thread.  It may already be scheduled, but it is
 185          * safe to kick it again.
 186          */
 187         schedule_work(&deferred_probe_work);
 188 }
 189
 190 /**
 191  * device_block_probing() - Block/defer device's probes
 192  *
 193  *      It will disable probing of devices and defer their probes instead.
 194  */
 195 void device_block_probing(void)
 196 {
 197         defer_all_probes = true;
 198         /* sync with probes to avoid races. */
 199         wait_for_device_probe();
 200 }
 201
 202 /**
 203  * device_unblock_probing() - Unblock/enable device's probes
 204  *
 205  *      It will restore normal behavior and trigger re-probing of deferred
 206  * devices.
 207  */
 208 void device_unblock_probing(void)
 209 {
 210         defer_all_probes = false;
 211         driver_deferred_probe_trigger();
 212 }
 213
 214 /*
 215  * deferred_devs_show() - Show the devices in the deferred probe pending list.
 216  */
 217 static int deferred_devs_show(struct seq_file *s, void *data)
 218 {
 219         struct device_private *curr;
 220
 221         mutex_lock(&deferred_probe_mutex);
 222
 223         list_for_each_entry(curr, &deferred_probe_pending_list, deferred_probe)
 224                 seq_printf(s, "%s\n", dev_name(curr->device));
 225
 226         mutex_unlock(&deferred_probe_mutex);
 227
 228         return 0;
 229 }
 230 DEFINE_SHOW_ATTRIBUTE(deferred_devs);
 231
 232 int driver_deferred_probe_timeout;
 233 EXPORT_SYMBOL_GPL(driver_deferred_probe_timeout);
 234 static DECLARE_WAIT_QUEUE_HEAD(probe_timeout_waitqueue);
 235
 236 static int __init deferred_probe_timeout_setup(char *str)
 237 {
 238         int timeout;
 239
 240         if (!kstrtoint(str, 10, &timeout))
 241                 driver_deferred_probe_timeout = timeout;
 242         return 1;
 243 }
 244 __setup("deferred_probe_timeout=", deferred_probe_timeout_setup);
 245
 246 /**
 247  * driver_deferred_probe_check_state() - Check deferred probe state
 248  * @dev: device to check
 249  *
 250  * Return:
 251  * -ENODEV if initcalls have completed and modules are disabled.
 252  * -ETIMEDOUT if the deferred probe timeout was set and has expired
 253  *  and modules are enabled.
 254  * -EPROBE_DEFER in other cases.
 255  *
 256  * Drivers or subsystems can opt-in to calling this function instead of directly
 257  * returning -EPROBE_DEFER.
 258  */
 259 int driver_deferred_probe_check_state(struct device *dev)
 260 {
 261         if (!IS_ENABLED(CONFIG_MODULES) && initcalls_done) {
 262                 dev_warn(dev, "ignoring dependency for device, assuming no driver\n");
 263                 return -ENODEV;
 264         }
 265
 266         if (!driver_deferred_probe_timeout && initcalls_done) {
 267                 dev_warn(dev, "deferred probe timeout, ignoring dependency\n");
 268                 return -ETIMEDOUT;
 269         }
 270
 271         return -EPROBE_DEFER;
 272 }
 273
 274 static void deferred_probe_timeout_work_func(struct work_struct *work)
 275 {
 276         struct device_private *private, *p;
 277
 278         driver_deferred_probe_timeout = 0;
 279         driver_deferred_probe_trigger();
 280         flush_work(&deferred_probe_work);
 281
 282         list_for_each_entry_safe(private, p, &deferred_probe_pending_list, deferred_probe)
 283                 dev_info(private->device, "deferred probe pending\n");
 284         wake_up(&probe_timeout_waitqueue);
 285 }
 286 static DECLARE_DELAYED_WORK(deferred_probe_timeout_work, deferred_probe_timeout_work_func);
 287
 288 /**
 289  * deferred_probe_initcall() - Enable probing of deferred devices
 290  *
 291  * We don't want to get in the way when the bulk of drivers are getting probed.
 292  * Instead, this initcall makes sure that deferred probing is delayed until
 293  * late_initcall time.
 294  */
 295 static int deferred_probe_initcall(void)
 296 {
 297         deferred_devices = debugfs_create_file("devices_deferred", 0444, NULL,
 298                                                NULL, &deferred_devs_fops);
 299
 300         driver_deferred_probe_enable = true;
 301         driver_deferred_probe_trigger();
 302         /* Sort as many dependencies as possible before exiting initcalls */
 303         flush_work(&deferred_probe_work);
 304         initcalls_done = true;
 305
 306         /*
 307          * Trigger deferred probe again, this time we won't defer anything
 308          * that is optional
 309          */
 310         driver_deferred_probe_trigger();
 311         flush_work(&deferred_probe_work);
 312
 313         if (driver_deferred_probe_timeout > 0) {
 314                 schedule_delayed_work(&deferred_probe_timeout_work,
 315                         driver_deferred_probe_timeout * HZ);
 316         }
 317         return 0;
 318 }
 319 late_initcall(deferred_probe_initcall);
 320
 321 static void __exit deferred_probe_exit(void)
 322 {
 323         debugfs_remove_recursive(deferred_devices);
 324 }
 325 __exitcall(deferred_probe_exit);
 326
 327 /**
 328  * device_is_bound() - Check if device is bound to a driver
 329  * @dev: device to check
 330  *
 331  * Returns true if passed device has already finished probing successfully
 332  * against a driver.
 333  *
 334  * This function must be called with the device lock held.
 335  */
 336 bool device_is_bound(struct device *dev)
 337 {
 338         return dev->p && klist_node_attached(&dev->p->knode_driver);
 339 }
 340
 341 static void driver_bound(struct device *dev)
 342 {
 343         if (device_is_bound(dev)) {
 344                 pr_warn("%s: device %s already bound\n",
 345                         __func__, kobject_name(&dev->kobj));
 346                 return;
 347         }
 348
 349         pr_debug("driver: '%s': %s: bound to device '%s'\n", dev->driver->name,
 350                  __func__, dev_name(dev));
 351
 352         klist_add_tail(&dev->p->knode_driver, &dev->driver->p->klist_devices);
 353         device_links_driver_bound(dev);
 354
 355         device_pm_check_callbacks(dev);
 356
 357         /*
 358          * Make sure the device is no longer in one of the deferred lists and
 359          * kick off retrying all pending devices
 360          */
 361         driver_deferred_probe_del(dev);
 362         driver_deferred_probe_trigger();
 363
 364         if (dev->bus)
 365                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 366                                              BUS_NOTIFY_BOUND_DRIVER, dev);
 367
 368         kobject_uevent(&dev->kobj, KOBJ_BIND);
 369 }
 370
 371 static ssize_t coredump_store(struct device *dev, struct device_attribute *attr,
 372                             const char *buf, size_t count)
 373 {
 374         device_lock(dev);
 375         dev->driver->coredump(dev);
 376         device_unlock(dev);
 377
 378         return count;
 379 }
 380 static DEVICE_ATTR_WO(coredump);
 381
 382 static int driver_sysfs_add(struct device *dev)
 383 {
 384         int ret;
 385
 386         if (dev->bus)
 387                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 388                                              BUS_NOTIFY_BIND_DRIVER, dev);
 389
 390         ret = sysfs_create_link(&dev->driver->p->kobj, &dev->kobj,
 391                                 kobject_name(&dev->kobj));
 392         if (ret)
 393                 goto fail;
 394
 395         ret = sysfs_create_link(&dev->kobj, &dev->driver->p->kobj,
 396                                 "driver");
 397         if (ret)
 398                 goto rm_dev;
 399
 400         if (!IS_ENABLED(CONFIG_DEV_COREDUMP) || !dev->driver->coredump ||
 401             !device_create_file(dev, &dev_attr_coredump))
 402                 return 0;
 403
 404         sysfs_remove_link(&dev->kobj, "driver");
 405
 406 rm_dev:
 407         sysfs_remove_link(&dev->driver->p->kobj,
 408                           kobject_name(&dev->kobj));
 409
 410 fail:
 411         return ret;
 412 }
 413
 414 static void driver_sysfs_remove(struct device *dev)
 415 {
 416         struct device_driver *drv = dev->driver;
 417
 418         if (drv) {
 419                 if (drv->coredump)
 420                         device_remove_file(dev, &dev_attr_coredump);
 421                 sysfs_remove_link(&drv->p->kobj, kobject_name(&dev->kobj));
 422                 sysfs_remove_link(&dev->kobj, "driver");
 423         }
 424 }
 425
 426 /**
 427  * device_bind_driver - bind a driver to one device.
 428  * @dev: device.
 429  *
 430  * Allow manual attachment of a driver to a device.
 431  * Caller must have already set @dev->driver.
 432  *
 433  * Note that this does not modify the bus reference count.
 434  * Please verify that is accounted for before calling this.
 435  * (It is ok to call with no other effort from a driver's probe() method.)
 436  *
 437  * This function must be called with the device lock held.
 438  */
 439 int device_bind_driver(struct device *dev)
 440 {
 441         int ret;
 442
 443         ret = driver_sysfs_add(dev);
 444         if (!ret)
 445                 driver_bound(dev);
 446         else if (dev->bus)
 447                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 448                                              BUS_NOTIFY_DRIVER_NOT_BOUND, dev);
 449         return ret;
 450 }
 451 EXPORT_SYMBOL_GPL(device_bind_driver);
 452
 453 static atomic_t probe_count = ATOMIC_INIT(0);
 454 static DECLARE_WAIT_QUEUE_HEAD(probe_waitqueue);
 455
 456 static void driver_deferred_probe_add_trigger(struct device *dev,
 457                                               int local_trigger_count)
 458 {
 459         driver_deferred_probe_add(dev);
 460         /* Did a trigger occur while probing? Need to re-trigger if yes */
 461         if (local_trigger_count != atomic_read(&deferred_trigger_count))
 462                 driver_deferred_probe_trigger();
 463 }
 464
 465 static ssize_t state_synced_show(struct device *dev,
 466                                  struct device_attribute *attr, char *buf)
 467 {
 468         bool val;
 469
 470         device_lock(dev);
 471         val = dev->state_synced;
 472         device_unlock(dev);
 473         return sprintf(buf, "%u\n", val);
 474 }
 475 static DEVICE_ATTR_RO(state_synced);
 476
 477 static int really_probe(struct device *dev, struct device_driver *drv)
 478 {
 479         int ret = -EPROBE_DEFER;
 480         int local_trigger_count = atomic_read(&deferred_trigger_count);
 481         bool test_remove = IS_ENABLED(CONFIG_DEBUG_TEST_DRIVER_REMOVE) &&
 482                            !drv->suppress_bind_attrs;
 483
 484         if (defer_all_probes) {
 485                 /*
 486                  * Value of defer_all_probes can be set only by
 487                  * device_block_probing() which, in turn, will call
 488                  * wait_for_device_probe() right after that to avoid any races.
 489                  */
 490                 dev_dbg(dev, "Driver %s force probe deferral\n", drv->name);
 491                 driver_deferred_probe_add(dev);
 492                 return ret;
 493         }
 494
 495         ret = device_links_check_suppliers(dev);
 496         if (ret == -EPROBE_DEFER)
 497                 driver_deferred_probe_add_trigger(dev, local_trigger_count);
 498         if (ret)
 499                 return ret;
 500
 501         atomic_inc(&probe_count);
 502         pr_debug("bus: '%s': %s: probing driver %s with device %s\n",
 503                  drv->bus->name, __func__, drv->name, dev_name(dev));
 504         if (!list_empty(&dev->devres_head)) {
 505                 dev_crit(dev, "Resources present before probing\n");
 506                 return -EBUSY;
 507         }
 508
 509 re_probe:
 510         dev->driver = drv;
 511
 512         /* If using pinctrl, bind pins now before probing */
 513         ret = pinctrl_bind_pins(dev);
 514         if (ret)
 515                 goto pinctrl_bind_failed;
 516
 517         if (dev->bus->dma_configure) {
 518                 ret = dev->bus->dma_configure(dev);
 519                 if (ret)
 520                         goto probe_failed;
 521         }
 522
 523         if (driver_sysfs_add(dev)) {
 524                 pr_err("%s: driver_sysfs_add(%s) failed\n",
 525                        __func__, dev_name(dev));
 526                 goto probe_failed;
 527         }
 528
 529         if (dev->pm_domain && dev->pm_domain->activate) {
 530                 ret = dev->pm_domain->activate(dev);
 531                 if (ret)
 532                         goto probe_failed;
 533         }
 534
 535         if (dev->bus->probe) {
 536                 ret = dev->bus->probe(dev);
 537                 if (ret)
 538                         goto probe_failed;
 539         } else if (drv->probe) {
 540                 ret = drv->probe(dev);
 541                 if (ret)
 542                         goto probe_failed;
 543         }
 544
 545         if (device_add_groups(dev, drv->dev_groups)) {
 546                 dev_err(dev, "device_add_groups() failed\n");
 547                 goto dev_groups_failed;
 548         }
 549
 550         if (dev_has_sync_state(dev) &&
 551             device_create_file(dev, &dev_attr_state_synced)) {
 552                 dev_err(dev, "state_synced sysfs add failed\n");
 553                 goto dev_sysfs_state_synced_failed;
 554         }
 555
 556         if (test_remove) {
 557                 test_remove = false;
 558
 559                 device_remove_file(dev, &dev_attr_state_synced);
 560                 device_remove_groups(dev, drv->dev_groups);
 561
 562                 if (dev->bus->remove)
 563                         dev->bus->remove(dev);
 564                 else if (drv->remove)
 565                         drv->remove(dev);
 566
 567                 devres_release_all(dev);
 568                 driver_sysfs_remove(dev);
 569                 dev->driver = NULL;
 570                 dev_set_drvdata(dev, NULL);
 571                 if (dev->pm_domain && dev->pm_domain->dismiss)
 572                         dev->pm_domain->dismiss(dev);
 573                 pm_runtime_reinit(dev);
 574
 575                 goto re_probe;
 576         }
 577
 578         pinctrl_init_done(dev);
 579
 580         if (dev->pm_domain && dev->pm_domain->sync)
 581                 dev->pm_domain->sync(dev);
 582
 583         driver_bound(dev);
 584         ret = 1;
 585         pr_debug("bus: '%s': %s: bound device %s to driver %s\n",
 586                  drv->bus->name, __func__, dev_name(dev), drv->name);
 587         goto done;
 588
 589 dev_sysfs_state_synced_failed:
 590         device_remove_groups(dev, drv->dev_groups);
 591 dev_groups_failed:
 592         if (dev->bus->remove)
 593                 dev->bus->remove(dev);
 594         else if (drv->remove)
 595                 drv->remove(dev);
 596 probe_failed:
 597         if (dev->bus)
 598                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 599                                              BUS_NOTIFY_DRIVER_NOT_BOUND, dev);
 600 pinctrl_bind_failed:
 601         device_links_no_driver(dev);
 602         devres_release_all(dev);
 603         arch_teardown_dma_ops(dev);
 604         driver_sysfs_remove(dev);
 605         dev->driver = NULL;
 606         dev_set_drvdata(dev, NULL);
 607         if (dev->pm_domain && dev->pm_domain->dismiss)
 608                 dev->pm_domain->dismiss(dev);
 609         pm_runtime_reinit(dev);
 610         dev_pm_set_driver_flags(dev, 0);
 611
 612         switch (ret) {
 613         case -EPROBE_DEFER:
 614                 /* Driver requested deferred probing */
 615                 dev_dbg(dev, "Driver %s requests probe deferral\n", drv->name);
 616                 driver_deferred_probe_add_trigger(dev, local_trigger_count);
 617                 break;
 618         case -ENODEV:
 619         case -ENXIO:
 620                 pr_debug("%s: probe of %s rejects match %d\n",
 621                          drv->name, dev_name(dev), ret);
 622                 break;
 623         default:
 624                 /* driver matched but the probe failed */
 625                 pr_warn("%s: probe of %s failed with error %d\n",
 626                         drv->name, dev_name(dev), ret);
 627         }
 628         /*
 629          * Ignore errors returned by ->probe so that the next driver can try
 630          * its luck.
 631          */
 632         ret = 0;
 633 done:
 634         atomic_dec(&probe_count);
 635         wake_up(&probe_waitqueue);
 636         return ret;
 637 }
 638
 639 /*
 640  * For initcall_debug, show the driver probe time.
 641  */
 642 static int really_probe_debug(struct device *dev, struct device_driver *drv)
 643 {
 644         ktime_t calltime, delta, rettime;
 645         int ret;
 646
 647         calltime = ktime_get();
 648         ret = really_probe(dev, drv);
 649         rettime = ktime_get();
 650         delta = ktime_sub(rettime, calltime);
 651         pr_debug("probe of %s returned %d after %lld usecs\n",
 652                  dev_name(dev), ret, (s64) ktime_to_us(delta));
 653         return ret;
 654 }
 655
 656 /**
 657  * driver_probe_done
 658  * Determine if the probe sequence is finished or not.
 659  *
 660  * Should somehow figure out how to use a semaphore, not an atomic variable...
 661  */
 662 int driver_probe_done(void)
 663 {
 664         int local_probe_count = atomic_read(&probe_count);
 665
 666         pr_debug("%s: probe_count = %d\n", __func__, local_probe_count);
 667         if (local_probe_count)
 668                 return -EBUSY;
 669         return 0;
 670 }
 671
 672 /**
 673  * wait_for_device_probe
 674  * Wait for device probing to be completed.
 675  */
 676 void wait_for_device_probe(void)
 677 {
 678         /* wait for probe timeout */
 679         wait_event(probe_timeout_waitqueue, !driver_deferred_probe_timeout);
 680
 681         /* wait for the deferred probe workqueue to finish */
 682         flush_work(&deferred_probe_work);
 683
 684         /* wait for the known devices to complete their probing */
 685         wait_event(probe_waitqueue, atomic_read(&probe_count) == 0);
 686         async_synchronize_full();
 687 }
 688 EXPORT_SYMBOL_GPL(wait_for_device_probe);
 689
 690 /**
 691  * driver_probe_device - attempt to bind device & driver together
 692  * @drv: driver to bind a device to
 693  * @dev: device to try to bind to the driver
 694  *
 695  * This function returns -ENODEV if the device is not registered,
 696  * 1 if the device is bound successfully and 0 otherwise.
 697  *
 698  * This function must be called with @dev lock held.  When called for a
 699  * USB interface, @dev->parent lock must be held as well.
 700  *
 701  * If the device has a parent, runtime-resume the parent before driver probing.
 702  */
 703 int driver_probe_device(struct device_driver *drv, struct device *dev)
 704 {
 705         int ret = 0;
 706
 707         if (!device_is_registered(dev))
 708                 return -ENODEV;
 709
 710         pr_debug("bus: '%s': %s: matched device %s with driver %s\n",
 711                  drv->bus->name, __func__, dev_name(dev), drv->name);
 712
 713         pm_runtime_get_suppliers(dev);
 714         if (dev->parent)
 715                 pm_runtime_get_sync(dev->parent);
 716
 717         pm_runtime_barrier(dev);
 718         if (initcall_debug)
 719                 ret = really_probe_debug(dev, drv);
 720         else
 721                 ret = really_probe(dev, drv);
 722         pm_request_idle(dev);
 723
 724         if (dev->parent)
 725                 pm_runtime_put(dev->parent);
 726
 727         pm_runtime_put_suppliers(dev);
 728         return ret;
 729 }
 730
 731 static inline bool cmdline_requested_async_probing(const char *drv_name)
 732 {
 733         return parse_option_str(async_probe_drv_names, drv_name);
 734 }
 735
 736 /* The option format is "driver_async_probe=drv_name1,drv_name2,..." */
 737 static int __init save_async_options(char *buf)
 738 {
 739         if (strlen(buf) >= ASYNC_DRV_NAMES_MAX_LEN)
 740                 pr_warn("Too long list of driver names for 'driver_async_probe'!\n");
 741
 742         strlcpy(async_probe_drv_names, buf, ASYNC_DRV_NAMES_MAX_LEN);
 743         return 0;
 744 }
 745 __setup("driver_async_probe=", save_async_options);
 746
 747 bool driver_allows_async_probing(struct device_driver *drv)
 748 {
 749         switch (drv->probe_type) {
 750         case PROBE_PREFER_ASYNCHRONOUS:
 751                 return true;
 752
 753         case PROBE_FORCE_SYNCHRONOUS:
 754                 return false;
 755
 756         default:
 757                 if (cmdline_requested_async_probing(drv->name))
 758                         return true;
 759
 760                 if (module_requested_async_probing(drv->owner))
 761                         return true;
 762
 763                 return false;
 764         }
 765 }
 766
 767 struct device_attach_data {
 768         struct device *dev;
 769
 770         /*
 771          * Indicates whether we are are considering asynchronous probing or
 772          * not. Only initial binding after device or driver registration
 773          * (including deferral processing) may be done asynchronously, the
 774          * rest is always synchronous, as we expect it is being done by
 775          * request from userspace.
 776          */
 777         bool check_async;
 778
 779         /*
 780          * Indicates if we are binding synchronous or asynchronous drivers.
 781          * When asynchronous probing is enabled we'll execute 2 passes
 782          * over drivers: first pass doing synchronous probing and second
 783          * doing asynchronous probing (if synchronous did not succeed -
 784          * most likely because there was no driver requiring synchronous
 785          * probing - and we found asynchronous driver during first pass).
 786          * The 2 passes are done because we can't shoot asynchronous
 787          * probe for given device and driver from bus_for_each_drv() since
 788          * driver pointer is not guaranteed to stay valid once
 789          * bus_for_each_drv() iterates to the next driver on the bus.
 790          */
 791         bool want_async;
 792
 793         /*
 794          * We'll set have_async to 'true' if, while scanning for matching
 795          * driver, we'll encounter one that requests asynchronous probing.
 796          */
 797         bool have_async;
 798 };
 799
 800 static int __device_attach_driver(struct device_driver *drv, void *_data)
 801 {
 802         struct device_attach_data *data = _data;
 803         struct device *dev = data->dev;
 804         bool async_allowed;
 805         int ret;
 806
 807         ret = driver_match_device(drv, dev);
 808         if (ret == 0) {
 809                 /* no match */
 810                 return 0;
 811         } else if (ret == -EPROBE_DEFER) {
 812                 dev_dbg(dev, "Device match requests probe deferral\n");
 813                 driver_deferred_probe_add(dev);
 814         } else if (ret < 0) {
 815                 dev_dbg(dev, "Bus failed to match device: %d\n", ret);
 816                 return ret;
 817         } /* ret > 0 means positive match */
 818
 819         async_allowed = driver_allows_async_probing(drv);
 820
 821         if (async_allowed)
 822                 data->have_async = true;
 823
 824         if (data->check_async && async_allowed != data->want_async)
 825                 return 0;
 826
 827         return driver_probe_device(drv, dev);
 828 }
 829
 830 static void __device_attach_async_helper(void *_dev, async_cookie_t cookie)
 831 {
 832         struct device *dev = _dev;
 833         struct device_attach_data data = {
 834                 .dev            = dev,
 835                 .check_async    = true,
 836                 .want_async     = true,
 837         };
 838
 839         device_lock(dev);
 840
 841         /*
 842          * Check if device has already been removed or claimed. This may
 843          * happen with driver loading, device discovery/registration,
 844          * and deferred probe processing happens all at once with
 845          * multiple threads.
 846          */
 847         if (dev->p->dead || dev->driver)
 848                 goto out_unlock;
 849
 850         if (dev->parent)
 851                 pm_runtime_get_sync(dev->parent);
 852
 853         bus_for_each_drv(dev->bus, NULL, &data, __device_attach_driver);
 854         dev_dbg(dev, "async probe completed\n");
 855
 856         pm_request_idle(dev);
 857
 858         if (dev->parent)
 859                 pm_runtime_put(dev->parent);
 860 out_unlock:
 861         device_unlock(dev);
 862
 863         put_device(dev);
 864 }
 865
 866 static int __device_attach(struct device *dev, bool allow_async)
 867 {
 868         int ret = 0;
 869
 870         device_lock(dev);
 871         if (dev->driver) {
 872                 if (device_is_bound(dev)) {
 873                         ret = 1;
 874                         goto out_unlock;
 875                 }
 876                 ret = device_bind_driver(dev);
 877                 if (ret == 0)
 878                         ret = 1;
 879                 else {
 880                         dev->driver = NULL;
 881                         ret = 0;
 882                 }
 883         } else {
 884                 struct device_attach_data data = {
 885                         .dev = dev,
 886                         .check_async = allow_async,
 887                         .want_async = false,
 888                 };
 889
 890                 if (dev->parent)
 891                         pm_runtime_get_sync(dev->parent);
 892
 893                 ret = bus_for_each_drv(dev->bus, NULL, &data,
 894                                         __device_attach_driver);
 895                 if (!ret && allow_async && data.have_async) {
 896                         /*
 897                          * If we could not find appropriate driver
 898                          * synchronously and we are allowed to do
 899                          * async probes and there are drivers that
 900                          * want to probe asynchronously, we'll
 901                          * try them.
 902                          */
 903                         dev_dbg(dev, "scheduling asynchronous probe\n");
 904                         get_device(dev);
 905                         async_schedule_dev(__device_attach_async_helper, dev);
 906                 } else {
 907                         pm_request_idle(dev);
 908                 }
 909
 910                 if (dev->parent)
 911                         pm_runtime_put(dev->parent);
 912         }
 913 out_unlock:
 914         device_unlock(dev);
 915         return ret;
 916 }
 917
 918 /**
 919  * device_attach - try to attach device to a driver.
 920  * @dev: device.
 921  *
 922  * Walk the list of drivers that the bus has and call
 923  * driver_probe_device() for each pair. If a compatible
 924  * pair is found, break out and return.
 925  *
 926  * Returns 1 if the device was bound to a driver;
 927  * 0 if no matching driver was found;
 928  * -ENODEV if the device is not registered.
 929  *
 930  * When called for a USB interface, @dev->parent lock must be held.
 931  */
 932 int device_attach(struct device *dev)
 933 {
 934         return __device_attach(dev, false);
 935 }
 936 EXPORT_SYMBOL_GPL(device_attach);
 937
 938 void device_initial_probe(struct device *dev)
 939 {
 940         __device_attach(dev, true);
 941 }
 942
 943 /*
 944  * __device_driver_lock - acquire locks needed to manipulate dev->drv
 945  * @dev: Device we will update driver info for
 946  * @parent: Parent device. Needed if the bus requires parent lock
 947  *
 948  * This function will take the required locks for manipulating dev->drv.
 949  * Normally this will just be the @dev lock, but when called for a USB
 950  * interface, @parent lock will be held as well.
 951  */
 952 static void __device_driver_lock(struct device *dev, struct device *parent)
 953 {
 954         if (parent && dev->bus->need_parent_lock)
 955                 device_lock(parent);
 956         device_lock(dev);
 957 }
 958
 959 /*
 960  * __device_driver_unlock - release locks needed to manipulate dev->drv
 961  * @dev: Device we will update driver info for
 962  * @parent: Parent device. Needed if the bus requires parent lock
 963  *
 964  * This function will release the required locks for manipulating dev->drv.
 965  * Normally this will just be the the @dev lock, but when called for a
 966  * USB interface, @parent lock will be released as well.
 967  */
 968 static void __device_driver_unlock(struct device *dev, struct device *parent)
 969 {
 970         device_unlock(dev);
 971         if (parent && dev->bus->need_parent_lock)
 972                 device_unlock(parent);
 973 }
 974
 975 /**
 976  * device_driver_attach - attach a specific driver to a specific device
 977  * @drv: Driver to attach
 978  * @dev: Device to attach it to
 979  *
 980  * Manually attach driver to a device. Will acquire both @dev lock and
 981  * @dev->parent lock if needed.
 982  */
 983 int device_driver_attach(struct device_driver *drv, struct device *dev)
 984 {
 985         int ret = 0;
 986
 987         __device_driver_lock(dev, dev->parent);
 988
 989         /*
 990          * If device has been removed or someone has already successfully
 991          * bound a driver before us just skip the driver probe call.
 992          */
 993         if (!dev->p->dead && !dev->driver)
 994                 ret = driver_probe_device(drv, dev);
 995
 996         __device_driver_unlock(dev, dev->parent);
 997
 998         return ret;
 999 }
1000
1001 static void __driver_attach_async_helper(void *_dev, async_cookie_t cookie)
1002 {
1003         struct device *dev = _dev;
1004         struct device_driver *drv;
1005         int ret = 0;
1006
1007         __device_driver_lock(dev, dev->parent);
1008
1009         drv = dev->p->async_driver;
1010
1011         /*
1012          * If device has been removed or someone has already successfully
1013          * bound a driver before us just skip the driver probe call.
1014          */
1015         if (!dev->p->dead && !dev->driver)
1016                 ret = driver_probe_device(drv, dev);
1017
1018         __device_driver_unlock(dev, dev->parent);
1019
1020         dev_dbg(dev, "driver %s async attach completed: %d\n", drv->name, ret);
1021
1022         put_device(dev);
1023 }
1024
1025 static int __driver_attach(struct device *dev, void *data)
1026 {
1027         struct device_driver *drv = data;
1028         int ret;
1029
1030         /*
1031          * Lock device and try to bind to it. We drop the error
1032          * here and always return 0, because we need to keep trying
1033          * to bind to devices and some drivers will return an error
1034          * simply if it didn't support the device.
1035          *
1036          * driver_probe_device() will spit a warning if there
1037          * is an error.
1038          */
1039
1040         ret = driver_match_device(drv, dev);
1041         if (ret == 0) {
1042                 /* no match */
1043                 return 0;
1044         } else if (ret == -EPROBE_DEFER) {
1045                 dev_dbg(dev, "Device match requests probe deferral\n");
1046                 driver_deferred_probe_add(dev);
1047         } else if (ret < 0) {
1048                 dev_dbg(dev, "Bus failed to match device: %d\n", ret);
1049                 return ret;
1050         } /* ret > 0 means positive match */
1051
1052         if (driver_allows_async_probing(drv)) {
1053                 /*
1054                  * Instead of probing the device synchronously we will
1055                  * probe it asynchronously to allow for more parallelism.
1056                  *
1057                  * We only take the device lock here in order to guarantee
1058                  * that the dev->driver and async_driver fields are protected
1059                  */
1060                 dev_dbg(dev, "probing driver %s asynchronously\n", drv->name);
1061                 device_lock(dev);
1062                 if (!dev->driver) {
1063                         get_device(dev);
1064                         dev->p->async_driver = drv;
1065                         async_schedule_dev(__driver_attach_async_helper, dev);
1066                 }
1067                 device_unlock(dev);
1068                 return 0;
1069         }
1070
1071         device_driver_attach(drv, dev);
1072
1073         return 0;
1074 }
1075
1076 /**
1077  * driver_attach - try to bind driver to devices.
1078  * @drv: driver.
1079  *
1080  * Walk the list of devices that the bus has on it and try to
1081  * match the driver with each one.  If driver_probe_device()
1082  * returns 0 and the @dev->driver is set, we've found a
1083  * compatible pair.
1084  */
1085 int driver_attach(struct device_driver *drv)
1086 {
1087         return bus_for_each_dev(drv->bus, NULL, drv, __driver_attach);
1088 }
1089 EXPORT_SYMBOL_GPL(driver_attach);
1090
1091 /*
1092  * __device_release_driver() must be called with @dev lock held.
1093  * When called for a USB interface, @dev->parent lock must be held as well.
1094  */
1095 static void __device_release_driver(struct device *dev, struct device *parent)
1096 {
1097         struct device_driver *drv;
1098
1099         drv = dev->driver;
1100         if (drv) {
1101                 while (device_links_busy(dev)) {
1102                         __device_driver_unlock(dev, parent);
1103
1104                         device_links_unbind_consumers(dev);
1105
1106                         __device_driver_lock(dev, parent);
1107                         /*
1108                          * A concurrent invocation of the same function might
1109                          * have released the driver successfully while this one
1110                          * was waiting, so check for that.
1111                          */
1112                         if (dev->driver != drv)
1113                                 return;
1114                 }
1115
1116                 pm_runtime_get_sync(dev);
1117                 pm_runtime_clean_up_links(dev);
1118
1119                 driver_sysfs_remove(dev);
1120
1121                 if (dev->bus)
1122                         blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
1123                                                      BUS_NOTIFY_UNBIND_DRIVER,
1124                                                      dev);
1125
1126                 pm_runtime_put_sync(dev);
1127
1128                 device_remove_file(dev, &dev_attr_state_synced);
1129                 device_remove_groups(dev, drv->dev_groups);
1130
1131                 if (dev->bus && dev->bus->remove)
1132                         dev->bus->remove(dev);
1133                 else if (drv->remove)
1134                         drv->remove(dev);
1135
1136                 device_links_driver_cleanup(dev);
1137
1138                 devres_release_all(dev);
1139                 arch_teardown_dma_ops(dev);
1140                 dev->driver = NULL;
1141                 dev_set_drvdata(dev, NULL);
1142                 if (dev->pm_domain && dev->pm_domain->dismiss)
1143                         dev->pm_domain->dismiss(dev);
1144                 pm_runtime_reinit(dev);
1145                 dev_pm_set_driver_flags(dev, 0);
1146
1147                 klist_remove(&dev->p->knode_driver);
1148                 device_pm_check_callbacks(dev);
1149                 if (dev->bus)
1150                         blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
1151                                                      BUS_NOTIFY_UNBOUND_DRIVER,
1152                                                      dev);
1153
1154                 kobject_uevent(&dev->kobj, KOBJ_UNBIND);
1155         }
1156 }
1157
1158 void device_release_driver_internal(struct device *dev,
1159                                     struct device_driver *drv,
1160                                     struct device *parent)
1161 {
1162         __device_driver_lock(dev, parent);
1163
1164         if (!drv || drv == dev->driver)
1165                 __device_release_driver(dev, parent);
1166
1167         __device_driver_unlock(dev, parent);
1168 }
1169
1170 /**
1171  * device_release_driver - manually detach device from driver.
1172  * @dev: device.
1173  *
1174  * Manually detach device from driver.
1175  * When called for a USB interface, @dev->parent lock must be held.
1176  *
1177  * If this function is to be called with @dev->parent lock held, ensure that
1178  * the device's consumers are unbound in advance or that their locks can be
1179  * acquired under the @dev->parent lock.
1180  */
1181 void device_release_driver(struct device *dev)
1182 {
1183         /*
1184          * If anyone calls device_release_driver() recursively from
1185          * within their ->remove callback for the same device, they
1186          * will deadlock right here.
1187          */
1188         device_release_driver_internal(dev, NULL, NULL);
1189 }
1190 EXPORT_SYMBOL_GPL(device_release_driver);
1191
1192 /**
1193  * device_driver_detach - detach driver from a specific device
1194  * @dev: device to detach driver from
1195  *
1196  * Detach driver from device. Will acquire both @dev lock and @dev->parent
1197  * lock if needed.
1198  */
1199 void device_driver_detach(struct device *dev)
1200 {
1201         device_release_driver_internal(dev, NULL, dev->parent);
1202 }
1203
1204 /**
1205  * driver_detach - detach driver from all devices it controls.
1206  * @drv: driver.
1207  */
1208 void driver_detach(struct device_driver *drv)
1209 {
1210         struct device_private *dev_prv;
1211         struct device *dev;
1212
1213         if (driver_allows_async_probing(drv))
1214                 async_synchronize_full();
1215
1216         for (;;) {
1217                 spin_lock(&drv->p->klist_devices.k_lock);
1218                 if (list_empty(&drv->p->klist_devices.k_list)) {
1219                         spin_unlock(&drv->p->klist_devices.k_lock);
1220                         break;
1221                 }
1222                 dev_prv = list_last_entry(&drv->p->klist_devices.k_list,
1223                                      struct device_private,
1224                                      knode_driver.n_node);
1225                 dev = dev_prv->device;
1226                 get_device(dev);
1227                 spin_unlock(&drv->p->klist_devices.k_lock);
1228                 device_release_driver_internal(dev, drv, dev->parent);
1229                 put_device(dev);
1230         }
1231 }