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