drivers/base/dd.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * drivers/base/dd.c - The core device/driver interactions.
   4  *
   5  * This file contains the (sometimes tricky) code that controls the
   6  * interactions between devices and drivers, which primarily includes
   7  * driver binding and unbinding.
   8  *
   9  * All of this code used to exist in drivers/base/bus.c, but was
  10  * relocated to here in the name of compartmentalization (since it wasn't
  11  * strictly code just for the 'struct bus_type'.
  12  *
  13  * Copyright (c) 2002-5 Patrick Mochel
  14  * Copyright (c) 2002-3 Open Source Development Labs
  15  * Copyright (c) 2007-2009 Greg Kroah-Hartman <gregkh@suse.de>
  16  * Copyright (c) 2007-2009 Novell Inc.
  17  */
  18
  19 #include <linux/debugfs.h>
  20 #include <linux/device.h>
  21 #include <linux/delay.h>
  22 #include <linux/dma-mapping.h>
  23 #include <linux/init.h>
  24 #include <linux/module.h>
  25 #include <linux/kthread.h>
  26 #include <linux/wait.h>
  27 #include <linux/async.h>
  28 #include <linux/pm_runtime.h>
  29 #include <linux/pinctrl/devinfo.h>
  30
  31 #include "base.h"
  32 #include "power/power.h"
  33
  34 /*
  35  * Deferred Probe infrastructure.
  36  *
  37  * Sometimes driver probe order matters, but the kernel doesn't always have
  38  * dependency information which means some drivers will get probed before a
  39  * resource it depends on is available.  For example, an SDHCI driver may
  40  * first need a GPIO line from an i2c GPIO controller before it can be
  41  * initialized.  If a required resource is not available yet, a driver can
  42  * request probing to be deferred by returning -EPROBE_DEFER from its probe hook
  43  *
  44  * Deferred probe maintains two lists of devices, a pending list and an active
  45  * list.  A driver returning -EPROBE_DEFER causes the device to be added to the
  46  * pending list.  A successful driver probe will trigger moving all devices
  47  * from the pending to the active list so that the workqueue will eventually
  48  * retry them.
  49  *
  50  * The deferred_probe_mutex must be held any time the deferred_probe_*_list
  51  * of the (struct device*)->p->deferred_probe pointers are manipulated
  52  */
  53 static DEFINE_MUTEX(deferred_probe_mutex);
  54 static LIST_HEAD(deferred_probe_pending_list);
  55 static LIST_HEAD(deferred_probe_active_list);
  56 static atomic_t deferred_trigger_count = ATOMIC_INIT(0);
  57 static struct dentry *deferred_devices;
  58 static bool initcalls_done;
  59
  60 /* Save the async probe drivers' name from kernel cmdline */
  61 #define ASYNC_DRV_NAMES_MAX_LEN 256
  62 static char async_probe_drv_names[ASYNC_DRV_NAMES_MAX_LEN];
  63
  64 /*
  65  * In some cases, like suspend to RAM or hibernation, It might be reasonable
  66  * to prohibit probing of devices as it could be unsafe.
  67  * Once defer_all_probes is true all drivers probes will be forcibly deferred.
  68  */
  69 static bool defer_all_probes;
  70
  71 /*
  72  * deferred_probe_work_func() - Retry probing devices in the active list.
  73  */
  74 static void deferred_probe_work_func(struct work_struct *work)
  75 {
  76         struct device *dev;
  77         struct device_private *private;
  78         /*
  79          * This block processes every device in the deferred 'active' list.
  80          * Each device is removed from the active list and passed to
  81          * bus_probe_device() to re-attempt the probe.  The loop continues
  82          * until every device in the active list is removed and retried.
  83          *
  84          * Note: Once the device is removed from the list and the mutex is
  85          * released, it is possible for the device get freed by another thread
  86          * and cause a illegal pointer dereference.  This code uses
  87          * get/put_device() to ensure the device structure cannot disappear
  88          * from under our feet.
  89          */
  90         mutex_lock(&deferred_probe_mutex);
  91         while (!list_empty(&deferred_probe_active_list)) {
  92                 private = list_first_entry(&deferred_probe_active_list,
  93                                         typeof(*dev->p), deferred_probe);
  94                 dev = private->device;
  95                 list_del_init(&private->deferred_probe);
  96
  97                 get_device(dev);
  98
  99                 /*
 100                  * Drop the mutex while probing each device; the probe path may
 101                  * manipulate the deferred list
 102                  */
 103                 mutex_unlock(&deferred_probe_mutex);
 104
 105                 /*
 106                  * Force the device to the end of the dpm_list since
 107                  * the PM code assumes that the order we add things to
 108                  * the list is a good order for suspend but deferred
 109                  * probe makes that very unsafe.
 110                  */
 111                 device_pm_move_to_tail(dev);
 112
 113                 dev_dbg(dev, "Retrying from deferred list\n");
 114                 bus_probe_device(dev);
 115                 mutex_lock(&deferred_probe_mutex);
 116
 117                 put_device(dev);
 118         }
 119         mutex_unlock(&deferred_probe_mutex);
 120 }
 121 static DECLARE_WORK(deferred_probe_work, deferred_probe_work_func);
 122
 123 void driver_deferred_probe_add(struct device *dev)
 124 {
 125         mutex_lock(&deferred_probe_mutex);
 126         if (list_empty(&dev->p->deferred_probe)) {
 127                 dev_dbg(dev, "Added to deferred list\n");
 128                 list_add_tail(&dev->p->deferred_probe, &deferred_probe_pending_list);
 129         }
 130         mutex_unlock(&deferred_probe_mutex);
 131 }
 132
 133 void driver_deferred_probe_del(struct device *dev)
 134 {
 135         mutex_lock(&deferred_probe_mutex);
 136         if (!list_empty(&dev->p->deferred_probe)) {
 137                 dev_dbg(dev, "Removed from deferred list\n");
 138                 list_del_init(&dev->p->deferred_probe);
 139         }
 140         mutex_unlock(&deferred_probe_mutex);
 141 }
 142
 143 static bool driver_deferred_probe_enable = false;
 144 /**
 145  * driver_deferred_probe_trigger() - Kick off re-probing deferred devices
 146  *
 147  * This functions moves all devices from the pending list to the active
 148  * list and schedules the deferred probe workqueue to process them.  It
 149  * should be called anytime a driver is successfully bound to a device.
 150  *
 151  * Note, there is a race condition in multi-threaded probe. In the case where
 152  * more than one device is probing at the same time, it is possible for one
 153  * probe to complete successfully while another is about to defer. If the second
 154  * depends on the first, then it will get put on the pending list after the
 155  * trigger event has already occurred and will be stuck there.
 156  *
 157  * The atomic 'deferred_trigger_count' is used to determine if a successful
 158  * trigger has occurred in the midst of probing a driver. If the trigger count
 159  * changes in the midst of a probe, then deferred processing should be triggered
 160  * again.
 161  */
 162 static void driver_deferred_probe_trigger(void)
 163 {
 164         if (!driver_deferred_probe_enable)
 165                 return;
 166
 167         /*
 168          * A successful probe means that all the devices in the pending list
 169          * should be triggered to be reprobed.  Move all the deferred devices
 170          * into the active list so they can be retried by the workqueue
 171          */
 172         mutex_lock(&deferred_probe_mutex);
 173         atomic_inc(&deferred_trigger_count);
 174         list_splice_tail_init(&deferred_probe_pending_list,
 175                               &deferred_probe_active_list);
 176         mutex_unlock(&deferred_probe_mutex);
 177
 178         /*
 179          * Kick the re-probe thread.  It may already be scheduled, but it is
 180          * safe to kick it again.
 181          */
 182         schedule_work(&deferred_probe_work);
 183 }
 184
 185 /**
 186  * device_block_probing() - Block/defer device's probes
 187  *
 188  *      It will disable probing of devices and defer their probes instead.
 189  */
 190 void device_block_probing(void)
 191 {
 192         defer_all_probes = true;
 193         /* sync with probes to avoid races. */
 194         wait_for_device_probe();
 195 }
 196
 197 /**
 198  * device_unblock_probing() - Unblock/enable device's probes
 199  *
 200  *      It will restore normal behavior and trigger re-probing of deferred
 201  * devices.
 202  */
 203 void device_unblock_probing(void)
 204 {
 205         defer_all_probes = false;
 206         driver_deferred_probe_trigger();
 207 }
 208
 209 /*
 210  * deferred_devs_show() - Show the devices in the deferred probe pending list.
 211  */
 212 static int deferred_devs_show(struct seq_file *s, void *data)
 213 {
 214         struct device_private *curr;
 215
 216         mutex_lock(&deferred_probe_mutex);
 217
 218         list_for_each_entry(curr, &deferred_probe_pending_list, deferred_probe)
 219                 seq_printf(s, "%s\n", dev_name(curr->device));
 220
 221         mutex_unlock(&deferred_probe_mutex);
 222
 223         return 0;
 224 }
 225 DEFINE_SHOW_ATTRIBUTE(deferred_devs);
 226
 227 static int deferred_probe_timeout = -1;
 228 static int __init deferred_probe_timeout_setup(char *str)
 229 {
 230         int timeout;
 231
 232         if (!kstrtoint(str, 10, &timeout))
 233                 deferred_probe_timeout = timeout;
 234         return 1;
 235 }
 236 __setup("deferred_probe_timeout=", deferred_probe_timeout_setup);
 237
 238 static int __driver_deferred_probe_check_state(struct device *dev)
 239 {
 240         if (!initcalls_done)
 241                 return -EPROBE_DEFER;
 242
 243         if (!deferred_probe_timeout) {
 244                 dev_WARN(dev, "deferred probe timeout, ignoring dependency");
 245                 return -ETIMEDOUT;
 246         }
 247
 248         return 0;
 249 }
 250
 251 /**
 252  * driver_deferred_probe_check_state() - Check deferred probe state
 253  * @dev: device to check
 254  *
 255  * Returns -ENODEV if init is done and all built-in drivers have had a chance
 256  * to probe (i.e. initcalls are done), -ETIMEDOUT if deferred probe debug
 257  * timeout has expired, or -EPROBE_DEFER if none of those conditions are met.
 258  *
 259  * Drivers or subsystems can opt-in to calling this function instead of directly
 260  * returning -EPROBE_DEFER.
 261  */
 262 int driver_deferred_probe_check_state(struct device *dev)
 263 {
 264         int ret;
 265
 266         ret = __driver_deferred_probe_check_state(dev);
 267         if (ret < 0)
 268                 return ret;
 269
 270         dev_warn(dev, "ignoring dependency for device, assuming no driver");
 271
 272         return -ENODEV;
 273 }
 274
 275 /**
 276  * driver_deferred_probe_check_state_continue() - check deferred probe state
 277  * @dev: device to check
 278  *
 279  * Returns -ETIMEDOUT if deferred probe debug timeout has expired, or
 280  * -EPROBE_DEFER otherwise.
 281  *
 282  * Drivers or subsystems can opt-in to calling this function instead of
 283  * directly returning -EPROBE_DEFER.
 284  *
 285  * This is similar to driver_deferred_probe_check_state(), but it allows the
 286  * subsystem to keep deferring probe after built-in drivers have had a chance
 287  * to probe. One scenario where that is useful is if built-in drivers rely on
 288  * resources that are provided by modular drivers.
 289  */
 290 int driver_deferred_probe_check_state_continue(struct device *dev)
 291 {
 292         int ret;
 293
 294         ret = __driver_deferred_probe_check_state(dev);
 295         if (ret < 0)
 296                 return ret;
 297
 298         return -EPROBE_DEFER;
 299 }
 300
 301 static void deferred_probe_timeout_work_func(struct work_struct *work)
 302 {
 303         struct device_private *private, *p;
 304
 305         deferred_probe_timeout = 0;
 306         driver_deferred_probe_trigger();
 307         flush_work(&deferred_probe_work);
 308
 309         list_for_each_entry_safe(private, p, &deferred_probe_pending_list, deferred_probe)
 310                 dev_info(private->device, "deferred probe pending");
 311 }
 312 static DECLARE_DELAYED_WORK(deferred_probe_timeout_work, deferred_probe_timeout_work_func);
 313
 314 /**
 315  * deferred_probe_initcall() - Enable probing of deferred devices
 316  *
 317  * We don't want to get in the way when the bulk of drivers are getting probed.
 318  * Instead, this initcall makes sure that deferred probing is delayed until
 319  * late_initcall time.
 320  */
 321 static int deferred_probe_initcall(void)
 322 {
 323         deferred_devices = debugfs_create_file("devices_deferred", 0444, NULL,
 324                                                NULL, &deferred_devs_fops);
 325
 326         driver_deferred_probe_enable = true;
 327         driver_deferred_probe_trigger();
 328         /* Sort as many dependencies as possible before exiting initcalls */
 329         flush_work(&deferred_probe_work);
 330         initcalls_done = true;
 331
 332         /*
 333          * Trigger deferred probe again, this time we won't defer anything
 334          * that is optional
 335          */
 336         driver_deferred_probe_trigger();
 337         flush_work(&deferred_probe_work);
 338
 339         if (deferred_probe_timeout > 0) {
 340                 schedule_delayed_work(&deferred_probe_timeout_work,
 341                         deferred_probe_timeout * HZ);
 342         }
 343         return 0;
 344 }
 345 late_initcall(deferred_probe_initcall);
 346
 347 static void __exit deferred_probe_exit(void)
 348 {
 349         debugfs_remove_recursive(deferred_devices);
 350 }
 351 __exitcall(deferred_probe_exit);
 352
 353 /**
 354  * device_is_bound() - Check if device is bound to a driver
 355  * @dev: device to check
 356  *
 357  * Returns true if passed device has already finished probing successfully
 358  * against a driver.
 359  *
 360  * This function must be called with the device lock held.
 361  */
 362 bool device_is_bound(struct device *dev)
 363 {
 364         return dev->p && klist_node_attached(&dev->p->knode_driver);
 365 }
 366
 367 static void driver_bound(struct device *dev)
 368 {
 369         if (device_is_bound(dev)) {
 370                 printk(KERN_WARNING "%s: device %s already bound\n",
 371                         __func__, kobject_name(&dev->kobj));
 372                 return;
 373         }
 374
 375         pr_debug("driver: '%s': %s: bound to device '%s'\n", dev->driver->name,
 376                  __func__, dev_name(dev));
 377
 378         klist_add_tail(&dev->p->knode_driver, &dev->driver->p->klist_devices);
 379         device_links_driver_bound(dev);
 380
 381         device_pm_check_callbacks(dev);
 382
 383         /*
 384          * Make sure the device is no longer in one of the deferred lists and
 385          * kick off retrying all pending devices
 386          */
 387         driver_deferred_probe_del(dev);
 388         driver_deferred_probe_trigger();
 389
 390         if (dev->bus)
 391                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 392                                              BUS_NOTIFY_BOUND_DRIVER, dev);
 393
 394         kobject_uevent(&dev->kobj, KOBJ_BIND);
 395 }
 396
 397 static ssize_t coredump_store(struct device *dev, struct device_attribute *attr,
 398                             const char *buf, size_t count)
 399 {
 400         device_lock(dev);
 401         dev->driver->coredump(dev);
 402         device_unlock(dev);
 403
 404         return count;
 405 }
 406 static DEVICE_ATTR_WO(coredump);
 407
 408 static int driver_sysfs_add(struct device *dev)
 409 {
 410         int ret;
 411
 412         if (dev->bus)
 413                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 414                                              BUS_NOTIFY_BIND_DRIVER, dev);
 415
 416         ret = sysfs_create_link(&dev->driver->p->kobj, &dev->kobj,
 417                                 kobject_name(&dev->kobj));
 418         if (ret)
 419                 goto fail;
 420
 421         ret = sysfs_create_link(&dev->kobj, &dev->driver->p->kobj,
 422                                 "driver");
 423         if (ret)
 424                 goto rm_dev;
 425
 426         if (!IS_ENABLED(CONFIG_DEV_COREDUMP) || !dev->driver->coredump ||
 427             !device_create_file(dev, &dev_attr_coredump))
 428                 return 0;
 429
 430         sysfs_remove_link(&dev->kobj, "driver");
 431
 432 rm_dev:
 433         sysfs_remove_link(&dev->driver->p->kobj,
 434                           kobject_name(&dev->kobj));
 435
 436 fail:
 437         return ret;
 438 }
 439
 440 static void driver_sysfs_remove(struct device *dev)
 441 {
 442         struct device_driver *drv = dev->driver;
 443
 444         if (drv) {
 445                 if (drv->coredump)
 446                         device_remove_file(dev, &dev_attr_coredump);
 447                 sysfs_remove_link(&drv->p->kobj, kobject_name(&dev->kobj));
 448                 sysfs_remove_link(&dev->kobj, "driver");
 449         }
 450 }
 451
 452 /**
 453  * device_bind_driver - bind a driver to one device.
 454  * @dev: device.
 455  *
 456  * Allow manual attachment of a driver to a device.
 457  * Caller must have already set @dev->driver.
 458  *
 459  * Note that this does not modify the bus reference count
 460  * nor take the bus's rwsem. Please verify those are accounted
 461  * for before calling this. (It is ok to call with no other effort
 462  * from a driver's probe() method.)
 463  *
 464  * This function must be called with the device lock held.
 465  */
 466 int device_bind_driver(struct device *dev)
 467 {
 468         int ret;
 469
 470         ret = driver_sysfs_add(dev);
 471         if (!ret)
 472                 driver_bound(dev);
 473         else if (dev->bus)
 474                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 475                                              BUS_NOTIFY_DRIVER_NOT_BOUND, dev);
 476         return ret;
 477 }
 478 EXPORT_SYMBOL_GPL(device_bind_driver);
 479
 480 static atomic_t probe_count = ATOMIC_INIT(0);
 481 static DECLARE_WAIT_QUEUE_HEAD(probe_waitqueue);
 482
 483 static void driver_deferred_probe_add_trigger(struct device *dev,
 484                                               int local_trigger_count)
 485 {
 486         driver_deferred_probe_add(dev);
 487         /* Did a trigger occur while probing? Need to re-trigger if yes */
 488         if (local_trigger_count != atomic_read(&deferred_trigger_count))
 489                 driver_deferred_probe_trigger();
 490 }
 491
 492 static int really_probe(struct device *dev, struct device_driver *drv)
 493 {
 494         int ret = -EPROBE_DEFER;
 495         int local_trigger_count = atomic_read(&deferred_trigger_count);
 496         bool test_remove = IS_ENABLED(CONFIG_DEBUG_TEST_DRIVER_REMOVE) &&
 497                            !drv->suppress_bind_attrs;
 498
 499         if (defer_all_probes) {
 500                 /*
 501                  * Value of defer_all_probes can be set only by
 502                  * device_block_probing() which, in turn, will call
 503                  * wait_for_device_probe() right after that to avoid any races.
 504                  */
 505                 dev_dbg(dev, "Driver %s force probe deferral\n", drv->name);
 506                 driver_deferred_probe_add(dev);
 507                 return ret;
 508         }
 509
 510         ret = device_links_check_suppliers(dev);
 511         if (ret == -EPROBE_DEFER)
 512                 driver_deferred_probe_add_trigger(dev, local_trigger_count);
 513         if (ret)
 514                 return ret;
 515
 516         atomic_inc(&probe_count);
 517         pr_debug("bus: '%s': %s: probing driver %s with device %s\n",
 518                  drv->bus->name, __func__, drv->name, dev_name(dev));
 519         if (!list_empty(&dev->devres_head)) {
 520                 dev_crit(dev, "Resources present before probing\n");
 521                 return -EBUSY;
 522         }
 523
 524 re_probe:
 525         dev->driver = drv;
 526
 527         /* If using pinctrl, bind pins now before probing */
 528         ret = pinctrl_bind_pins(dev);
 529         if (ret)
 530                 goto pinctrl_bind_failed;
 531
 532         if (dev->bus->dma_configure) {
 533                 ret = dev->bus->dma_configure(dev);
 534                 if (ret)
 535                         goto probe_failed;
 536         }
 537
 538         if (driver_sysfs_add(dev)) {
 539                 printk(KERN_ERR "%s: driver_sysfs_add(%s) failed\n",
 540                         __func__, dev_name(dev));
 541                 goto probe_failed;
 542         }
 543
 544         if (dev->pm_domain && dev->pm_domain->activate) {
 545                 ret = dev->pm_domain->activate(dev);
 546                 if (ret)
 547                         goto probe_failed;
 548         }
 549
 550         if (dev->bus->probe) {
 551                 ret = dev->bus->probe(dev);
 552                 if (ret)
 553                         goto probe_failed;
 554         } else if (drv->probe) {
 555                 ret = drv->probe(dev);
 556                 if (ret)
 557                         goto probe_failed;
 558         }
 559
 560         if (device_add_groups(dev, drv->dev_groups)) {
 561                 dev_err(dev, "device_add_groups() failed\n");
 562                 goto dev_groups_failed;
 563         }
 564
 565         if (test_remove) {
 566                 test_remove = false;
 567
 568                 device_remove_groups(dev, drv->dev_groups);
 569
 570                 if (dev->bus->remove)
 571                         dev->bus->remove(dev);
 572                 else if (drv->remove)
 573                         drv->remove(dev);
 574
 575                 devres_release_all(dev);
 576                 driver_sysfs_remove(dev);
 577                 dev->driver = NULL;
 578                 dev_set_drvdata(dev, NULL);
 579                 if (dev->pm_domain && dev->pm_domain->dismiss)
 580                         dev->pm_domain->dismiss(dev);
 581                 pm_runtime_reinit(dev);
 582
 583                 goto re_probe;
 584         }
 585
 586         pinctrl_init_done(dev);
 587
 588         if (dev->pm_domain && dev->pm_domain->sync)
 589                 dev->pm_domain->sync(dev);
 590
 591         driver_bound(dev);
 592         ret = 1;
 593         pr_debug("bus: '%s': %s: bound device %s to driver %s\n",
 594                  drv->bus->name, __func__, dev_name(dev), drv->name);
 595         goto done;
 596
 597 dev_groups_failed:
 598         if (dev->bus->remove)
 599                 dev->bus->remove(dev);
 600         else if (drv->remove)
 601                 drv->remove(dev);
 602 probe_failed:
 603         if (dev->bus)
 604                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 605                                              BUS_NOTIFY_DRIVER_NOT_BOUND, dev);
 606 pinctrl_bind_failed:
 607         device_links_no_driver(dev);
 608         devres_release_all(dev);
 609         arch_teardown_dma_ops(dev);
 610         driver_sysfs_remove(dev);
 611         dev->driver = NULL;
 612         dev_set_drvdata(dev, NULL);
 613         if (dev->pm_domain && dev->pm_domain->dismiss)
 614                 dev->pm_domain->dismiss(dev);
 615         pm_runtime_reinit(dev);
 616         dev_pm_set_driver_flags(dev, 0);
 617
 618         switch (ret) {
 619         case -EPROBE_DEFER:
 620                 /* Driver requested deferred probing */
 621                 dev_dbg(dev, "Driver %s requests probe deferral\n", drv->name);
 622                 driver_deferred_probe_add_trigger(dev, local_trigger_count);
 623                 break;
 624         case -ENODEV:
 625         case -ENXIO:
 626                 pr_debug("%s: probe of %s rejects match %d\n",
 627                          drv->name, dev_name(dev), ret);
 628                 break;
 629         default:
 630                 /* driver matched but the probe failed */
 631                 printk(KERN_WARNING
 632                        "%s: probe of %s failed with error %d\n",
 633                        drv->name, dev_name(dev), ret);
 634         }
 635         /*
 636          * Ignore errors returned by ->probe so that the next driver can try
 637          * its luck.
 638          */
 639         ret = 0;
 640 done:
 641         atomic_dec(&probe_count);
 642         wake_up(&probe_waitqueue);
 643         return ret;
 644 }
 645
 646 /*
 647  * For initcall_debug, show the driver probe time.
 648  */
 649 static int really_probe_debug(struct device *dev, struct device_driver *drv)
 650 {
 651         ktime_t calltime, delta, rettime;
 652         int ret;
 653
 654         calltime = ktime_get();
 655         ret = really_probe(dev, drv);
 656         rettime = ktime_get();
 657         delta = ktime_sub(rettime, calltime);
 658         printk(KERN_DEBUG "probe of %s returned %d after %lld usecs\n",
 659                dev_name(dev), ret, (s64) ktime_to_us(delta));
 660         return ret;
 661 }
 662
 663 /**
 664  * driver_probe_done
 665  * Determine if the probe sequence is finished or not.
 666  *
 667  * Should somehow figure out how to use a semaphore, not an atomic variable...
 668  */
 669 int driver_probe_done(void)
 670 {
 671         pr_debug("%s: probe_count = %d\n", __func__,
 672                  atomic_read(&probe_count));
 673         if (atomic_read(&probe_count))
 674                 return -EBUSY;
 675         return 0;
 676 }
 677
 678 /**
 679  * wait_for_device_probe
 680  * Wait for device probing to be completed.
 681  */
 682 void wait_for_device_probe(void)
 683 {
 684         /* wait for the deferred probe workqueue to finish */
 685         flush_work(&deferred_probe_work);
 686
 687         /* wait for the known devices to complete their probing */
 688         wait_event(probe_waitqueue, atomic_read(&probe_count) == 0);
 689         async_synchronize_full();
 690 }
 691 EXPORT_SYMBOL_GPL(wait_for_device_probe);
 692
 693 /**
 694  * driver_probe_device - attempt to bind device & driver together
 695  * @drv: driver to bind a device to
 696  * @dev: device to try to bind to the driver
 697  *
 698  * This function returns -ENODEV if the device is not registered,
 699  * 1 if the device is bound successfully and 0 otherwise.
 700  *
 701  * This function must be called with @dev lock held.  When called for a
 702  * USB interface, @dev->parent lock must be held as well.
 703  *
 704  * If the device has a parent, runtime-resume the parent before driver probing.
 705  */
 706 int driver_probe_device(struct device_driver *drv, struct device *dev)
 707 {
 708         int ret = 0;
 709
 710         if (!device_is_registered(dev))
 711                 return -ENODEV;
 712
 713         pr_debug("bus: '%s': %s: matched device %s with driver %s\n",
 714                  drv->bus->name, __func__, dev_name(dev), drv->name);
 715
 716         pm_runtime_get_suppliers(dev);
 717         if (dev->parent)
 718                 pm_runtime_get_sync(dev->parent);
 719
 720         pm_runtime_barrier(dev);
 721         if (initcall_debug)
 722                 ret = really_probe_debug(dev, drv);
 723         else
 724                 ret = really_probe(dev, drv);
 725         pm_request_idle(dev);
 726
 727         if (dev->parent)
 728                 pm_runtime_put(dev->parent);
 729
 730         pm_runtime_put_suppliers(dev);
 731         return ret;
 732 }
 733
 734 static inline bool cmdline_requested_async_probing(const char *drv_name)
 735 {
 736         return parse_option_str(async_probe_drv_names, drv_name);
 737 }
 738
 739 /* The option format is "driver_async_probe=drv_name1,drv_name2,..." */
 740 static int __init save_async_options(char *buf)
 741 {
 742         if (strlen(buf) >= ASYNC_DRV_NAMES_MAX_LEN)
 743                 printk(KERN_WARNING
 744                         "Too long list of driver names for 'driver_async_probe'!\n");
 745
 746         strlcpy(async_probe_drv_names, buf, ASYNC_DRV_NAMES_MAX_LEN);
 747         return 0;
 748 }
 749 __setup("driver_async_probe=", save_async_options);
 750
 751 bool driver_allows_async_probing(struct device_driver *drv)
 752 {
 753         switch (drv->probe_type) {
 754         case PROBE_PREFER_ASYNCHRONOUS:
 755                 return true;
 756
 757         case PROBE_FORCE_SYNCHRONOUS:
 758                 return false;
 759
 760         default:
 761                 if (cmdline_requested_async_probing(drv->name))
 762                         return true;
 763
 764                 if (module_requested_async_probing(drv->owner))
 765                         return true;
 766
 767                 return false;
 768         }
 769 }
 770
 771 struct device_attach_data {
 772         struct device *dev;
 773
 774         /*
 775          * Indicates whether we are are considering asynchronous probing or
 776          * not. Only initial binding after device or driver registration
 777          * (including deferral processing) may be done asynchronously, the
 778          * rest is always synchronous, as we expect it is being done by
 779          * request from userspace.
 780          */
 781         bool check_async;
 782
 783         /*
 784          * Indicates if we are binding synchronous or asynchronous drivers.
 785          * When asynchronous probing is enabled we'll execute 2 passes
 786          * over drivers: first pass doing synchronous probing and second
 787          * doing asynchronous probing (if synchronous did not succeed -
 788          * most likely because there was no driver requiring synchronous
 789          * probing - and we found asynchronous driver during first pass).
 790          * The 2 passes are done because we can't shoot asynchronous
 791          * probe for given device and driver from bus_for_each_drv() since
 792          * driver pointer is not guaranteed to stay valid once
 793          * bus_for_each_drv() iterates to the next driver on the bus.
 794          */
 795         bool want_async;
 796
 797         /*
 798          * We'll set have_async to 'true' if, while scanning for matching
 799          * driver, we'll encounter one that requests asynchronous probing.
 800          */
 801         bool have_async;
 802 };
 803
 804 static int __device_attach_driver(struct device_driver *drv, void *_data)
 805 {
 806         struct device_attach_data *data = _data;
 807         struct device *dev = data->dev;
 808         bool async_allowed;
 809         int ret;
 810
 811         ret = driver_match_device(drv, dev);
 812         if (ret == 0) {
 813                 /* no match */
 814                 return 0;
 815         } else if (ret == -EPROBE_DEFER) {
 816                 dev_dbg(dev, "Device match requests probe deferral\n");
 817                 driver_deferred_probe_add(dev);
 818         } else if (ret < 0) {
 819                 dev_dbg(dev, "Bus failed to match device: %d", ret);
 820                 return ret;
 821         } /* ret > 0 means positive match */
 822
 823         async_allowed = driver_allows_async_probing(drv);
 824
 825         if (async_allowed)
 826                 data->have_async = true;
 827
 828         if (data->check_async && async_allowed != data->want_async)
 829                 return 0;
 830
 831         return driver_probe_device(drv, dev);
 832 }
 833
 834 static void __device_attach_async_helper(void *_dev, async_cookie_t cookie)
 835 {
 836         struct device *dev = _dev;
 837         struct device_attach_data data = {
 838                 .dev            = dev,
 839                 .check_async    = true,
 840                 .want_async     = true,
 841         };
 842
 843         device_lock(dev);
 844
 845         /*
 846          * Check if device has already been removed or claimed. This may
 847          * happen with driver loading, device discovery/registration,
 848          * and deferred probe processing happens all at once with
 849          * multiple threads.
 850          */
 851         if (dev->p->dead || dev->driver)
 852                 goto out_unlock;
 853
 854         if (dev->parent)
 855                 pm_runtime_get_sync(dev->parent);
 856
 857         bus_for_each_drv(dev->bus, NULL, &data, __device_attach_driver);
 858         dev_dbg(dev, "async probe completed\n");
 859
 860         pm_request_idle(dev);
 861
 862         if (dev->parent)
 863                 pm_runtime_put(dev->parent);
 864 out_unlock:
 865         device_unlock(dev);
 866
 867         put_device(dev);
 868 }
 869
 870 static int __device_attach(struct device *dev, bool allow_async)
 871 {
 872         int ret = 0;
 873
 874         device_lock(dev);
 875         if (dev->driver) {
 876                 if (device_is_bound(dev)) {
 877                         ret = 1;
 878                         goto out_unlock;
 879                 }
 880                 ret = device_bind_driver(dev);
 881                 if (ret == 0)
 882                         ret = 1;
 883                 else {
 884                         dev->driver = NULL;
 885                         ret = 0;
 886                 }
 887         } else {
 888                 struct device_attach_data data = {
 889                         .dev = dev,
 890                         .check_async = allow_async,
 891                         .want_async = false,
 892                 };
 893
 894                 if (dev->parent)
 895                         pm_runtime_get_sync(dev->parent);
 896
 897                 ret = bus_for_each_drv(dev->bus, NULL, &data,
 898                                         __device_attach_driver);
 899                 if (!ret && allow_async && data.have_async) {
 900                         /*
 901                          * If we could not find appropriate driver
 902                          * synchronously and we are allowed to do
 903                          * async probes and there are drivers that
 904                          * want to probe asynchronously, we'll
 905                          * try them.
 906                          */
 907                         dev_dbg(dev, "scheduling asynchronous probe\n");
 908                         get_device(dev);
 909                         async_schedule_dev(__device_attach_async_helper, dev);
 910                 } else {
 911                         pm_request_idle(dev);
 912                 }
 913
 914                 if (dev->parent)
 915                         pm_runtime_put(dev->parent);
 916         }
 917 out_unlock:
 918         device_unlock(dev);
 919         return ret;
 920 }
 921
 922 /**
 923  * device_attach - try to attach device to a driver.
 924  * @dev: device.
 925  *
 926  * Walk the list of drivers that the bus has and call
 927  * driver_probe_device() for each pair. If a compatible
 928  * pair is found, break out and return.
 929  *
 930  * Returns 1 if the device was bound to a driver;
 931  * 0 if no matching driver was found;
 932  * -ENODEV if the device is not registered.
 933  *
 934  * When called for a USB interface, @dev->parent lock must be held.
 935  */
 936 int device_attach(struct device *dev)
 937 {
 938         return __device_attach(dev, false);
 939 }
 940 EXPORT_SYMBOL_GPL(device_attach);
 941
 942 void device_initial_probe(struct device *dev)
 943 {
 944         __device_attach(dev, true);
 945 }
 946
 947 /*
 948  * __device_driver_lock - acquire locks needed to manipulate dev->drv
 949  * @dev: Device we will update driver info for
 950  * @parent: Parent device. Needed if the bus requires parent lock
 951  *
 952  * This function will take the required locks for manipulating dev->drv.
 953  * Normally this will just be the @dev lock, but when called for a USB
 954  * interface, @parent lock will be held as well.
 955  */
 956 static void __device_driver_lock(struct device *dev, struct device *parent)
 957 {
 958         if (parent && dev->bus->need_parent_lock)
 959                 device_lock(parent);
 960         device_lock(dev);
 961 }
 962
 963 /*
 964  * __device_driver_unlock - release locks needed to manipulate dev->drv
 965  * @dev: Device we will update driver info for
 966  * @parent: Parent device. Needed if the bus requires parent lock
 967  *
 968  * This function will release the required locks for manipulating dev->drv.
 969  * Normally this will just be the the @dev lock, but when called for a
 970  * USB interface, @parent lock will be released as well.
 971  */
 972 static void __device_driver_unlock(struct device *dev, struct device *parent)
 973 {
 974         device_unlock(dev);
 975         if (parent && dev->bus->need_parent_lock)
 976                 device_unlock(parent);
 977 }
 978
 979 /**
 980  * device_driver_attach - attach a specific driver to a specific device
 981  * @drv: Driver to attach
 982  * @dev: Device to attach it to
 983  *
 984  * Manually attach driver to a device. Will acquire both @dev lock and
 985  * @dev->parent lock if needed.
 986  */
 987 int device_driver_attach(struct device_driver *drv, struct device *dev)
 988 {
 989         int ret = 0;
 990
 991         __device_driver_lock(dev, dev->parent);
 992
 993         /*
 994          * If device has been removed or someone has already successfully
 995          * bound a driver before us just skip the driver probe call.
 996          */
 997         if (!dev->p->dead && !dev->driver)
 998                 ret = driver_probe_device(drv, dev);
 999
1000         __device_driver_unlock(dev, dev->parent);
1001
1002         return ret;
1003 }
1004
1005 static void __driver_attach_async_helper(void *_dev, async_cookie_t cookie)
1006 {
1007         struct device *dev = _dev;
1008         struct device_driver *drv;
1009         int ret = 0;
1010
1011         __device_driver_lock(dev, dev->parent);
1012
1013         drv = dev->p->async_driver;
1014
1015         /*
1016          * If device has been removed or someone has already successfully
1017          * bound a driver before us just skip the driver probe call.
1018          */
1019         if (!dev->p->dead && !dev->driver)
1020                 ret = driver_probe_device(drv, dev);
1021
1022         __device_driver_unlock(dev, dev->parent);
1023
1024         dev_dbg(dev, "driver %s async attach completed: %d\n", drv->name, ret);
1025
1026         put_device(dev);
1027 }
1028
1029 static int __driver_attach(struct device *dev, void *data)
1030 {
1031         struct device_driver *drv = data;
1032         int ret;
1033
1034         /*
1035          * Lock device and try to bind to it. We drop the error
1036          * here and always return 0, because we need to keep trying
1037          * to bind to devices and some drivers will return an error
1038          * simply if it didn't support the device.
1039          *
1040          * driver_probe_device() will spit a warning if there
1041          * is an error.
1042          */
1043
1044         ret = driver_match_device(drv, dev);
1045         if (ret == 0) {
1046                 /* no match */
1047                 return 0;
1048         } else if (ret == -EPROBE_DEFER) {
1049                 dev_dbg(dev, "Device match requests probe deferral\n");
1050                 driver_deferred_probe_add(dev);
1051         } else if (ret < 0) {
1052                 dev_dbg(dev, "Bus failed to match device: %d", ret);
1053                 return ret;
1054         } /* ret > 0 means positive match */
1055
1056         if (driver_allows_async_probing(drv)) {
1057                 /*
1058                  * Instead of probing the device synchronously we will
1059                  * probe it asynchronously to allow for more parallelism.
1060                  *
1061                  * We only take the device lock here in order to guarantee
1062                  * that the dev->driver and async_driver fields are protected
1063                  */
1064                 dev_dbg(dev, "probing driver %s asynchronously\n", drv->name);
1065                 device_lock(dev);
1066                 if (!dev->driver) {
1067                         get_device(dev);
1068                         dev->p->async_driver = drv;
1069                         async_schedule_dev(__driver_attach_async_helper, dev);
1070                 }
1071                 device_unlock(dev);
1072                 return 0;
1073         }
1074
1075         device_driver_attach(drv, dev);
1076
1077         return 0;
1078 }
1079
1080 /**
1081  * driver_attach - try to bind driver to devices.
1082  * @drv: driver.
1083  *
1084  * Walk the list of devices that the bus has on it and try to
1085  * match the driver with each one.  If driver_probe_device()
1086  * returns 0 and the @dev->driver is set, we've found a
1087  * compatible pair.
1088  */
1089 int driver_attach(struct device_driver *drv)
1090 {
1091         return bus_for_each_dev(drv->bus, NULL, drv, __driver_attach);
1092 }
1093 EXPORT_SYMBOL_GPL(driver_attach);
1094
1095 /*
1096  * __device_release_driver() must be called with @dev lock held.
1097  * When called for a USB interface, @dev->parent lock must be held as well.
1098  */
1099 static void __device_release_driver(struct device *dev, struct device *parent)
1100 {
1101         struct device_driver *drv;
1102
1103         drv = dev->driver;
1104         if (drv) {
1105                 while (device_links_busy(dev)) {
1106                         __device_driver_unlock(dev, parent);
1107
1108                         device_links_unbind_consumers(dev);
1109
1110                         __device_driver_lock(dev, parent);
1111                         /*
1112                          * A concurrent invocation of the same function might
1113                          * have released the driver successfully while this one
1114                          * was waiting, so check for that.
1115                          */
1116                         if (dev->driver != drv)
1117                                 return;
1118                 }
1119
1120                 pm_runtime_get_sync(dev);
1121                 pm_runtime_clean_up_links(dev);
1122
1123                 driver_sysfs_remove(dev);
1124
1125                 if (dev->bus)
1126                         blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
1127                                                      BUS_NOTIFY_UNBIND_DRIVER,
1128                                                      dev);
1129
1130                 pm_runtime_put_sync(dev);
1131
1132                 device_remove_groups(dev, drv->dev_groups);
1133
1134                 if (dev->bus && dev->bus->remove)
1135                         dev->bus->remove(dev);
1136                 else if (drv->remove)
1137                         drv->remove(dev);
1138
1139                 device_links_driver_cleanup(dev);
1140
1141                 devres_release_all(dev);
1142                 arch_teardown_dma_ops(dev);
1143                 dev->driver = NULL;
1144                 dev_set_drvdata(dev, NULL);
1145                 if (dev->pm_domain && dev->pm_domain->dismiss)
1146                         dev->pm_domain->dismiss(dev);
1147                 pm_runtime_reinit(dev);
1148                 dev_pm_set_driver_flags(dev, 0);
1149
1150                 klist_remove(&dev->p->knode_driver);
1151                 device_pm_check_callbacks(dev);
1152                 if (dev->bus)
1153                         blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
1154                                                      BUS_NOTIFY_UNBOUND_DRIVER,
1155                                                      dev);
1156
1157                 kobject_uevent(&dev->kobj, KOBJ_UNBIND);
1158         }
1159 }
1160
1161 void device_release_driver_internal(struct device *dev,
1162                                     struct device_driver *drv,
1163                                     struct device *parent)
1164 {
1165         __device_driver_lock(dev, parent);
1166
1167         if (!drv || drv == dev->driver)
1168                 __device_release_driver(dev, parent);
1169
1170         __device_driver_unlock(dev, parent);
1171 }
1172
1173 /**
1174  * device_release_driver - manually detach device from driver.
1175  * @dev: device.
1176  *
1177  * Manually detach device from driver.
1178  * When called for a USB interface, @dev->parent lock must be held.
1179  *
1180  * If this function is to be called with @dev->parent lock held, ensure that
1181  * the device's consumers are unbound in advance or that their locks can be
1182  * acquired under the @dev->parent lock.
1183  */
1184 void device_release_driver(struct device *dev)
1185 {
1186         /*
1187          * If anyone calls device_release_driver() recursively from
1188          * within their ->remove callback for the same device, they
1189          * will deadlock right here.
1190          */
1191         device_release_driver_internal(dev, NULL, NULL);
1192 }
1193 EXPORT_SYMBOL_GPL(device_release_driver);
1194
1195 /**
1196  * device_driver_detach - detach driver from a specific device
1197  * @dev: device to detach driver from
1198  *
1199  * Detach driver from device. Will acquire both @dev lock and @dev->parent
1200  * lock if needed.
1201  */
1202 void device_driver_detach(struct device *dev)
1203 {
1204         device_release_driver_internal(dev, NULL, dev->parent);
1205 }
1206
1207 /**
1208  * driver_detach - detach driver from all devices it controls.
1209  * @drv: driver.
1210  */
1211 void driver_detach(struct device_driver *drv)
1212 {
1213         struct device_private *dev_prv;
1214         struct device *dev;
1215
1216         if (driver_allows_async_probing(drv))
1217                 async_synchronize_full();
1218
1219         for (;;) {
1220                 spin_lock(&drv->p->klist_devices.k_lock);
1221                 if (list_empty(&drv->p->klist_devices.k_list)) {
1222                         spin_unlock(&drv->p->klist_devices.k_lock);
1223                         break;
1224                 }
1225                 dev_prv = list_entry(drv->p->klist_devices.k_list.prev,
1226                                      struct device_private,
1227                                      knode_driver.n_node);
1228                 dev = dev_prv->device;
1229                 get_device(dev);
1230                 spin_unlock(&drv->p->klist_devices.k_lock);
1231                 device_release_driver_internal(dev, drv, dev->parent);
1232                 put_device(dev);
1233         }
1234 }