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-map-ops.h>
  23 #include <linux/init.h>
  24 #include <linux/module.h>
  25 #include <linux/kthread.h>
  26 #include <linux/wait.h>
  27 #include <linux/async.h>
  28 #include <linux/pm_runtime.h>
  29 #include <linux/pinctrl/devinfo.h>
  30 #include <linux/slab.h>
  31
  32 #include "base.h"
  33 #include "power/power.h"
  34
  35 /*
  36  * Deferred Probe infrastructure.
  37  *
  38  * Sometimes driver probe order matters, but the kernel doesn't always have
  39  * dependency information which means some drivers will get probed before a
  40  * resource it depends on is available.  For example, an SDHCI driver may
  41  * first need a GPIO line from an i2c GPIO controller before it can be
  42  * initialized.  If a required resource is not available yet, a driver can
  43  * request probing to be deferred by returning -EPROBE_DEFER from its probe hook
  44  *
  45  * Deferred probe maintains two lists of devices, a pending list and an active
  46  * list.  A driver returning -EPROBE_DEFER causes the device to be added to the
  47  * pending list.  A successful driver probe will trigger moving all devices
  48  * from the pending to the active list so that the workqueue will eventually
  49  * retry them.
  50  *
  51  * The deferred_probe_mutex must be held any time the deferred_probe_*_list
  52  * of the (struct device*)->p->deferred_probe pointers are manipulated
  53  */
  54 static DEFINE_MUTEX(deferred_probe_mutex);
  55 static LIST_HEAD(deferred_probe_pending_list);
  56 static LIST_HEAD(deferred_probe_active_list);
  57 static atomic_t deferred_trigger_count = ATOMIC_INIT(0);
  58 static struct dentry *deferred_devices;
  59 static bool initcalls_done;
  60
  61 /* Save the async probe drivers' name from kernel cmdline */
  62 #define ASYNC_DRV_NAMES_MAX_LEN 256
  63 static char async_probe_drv_names[ASYNC_DRV_NAMES_MAX_LEN];
  64
  65 /*
  66  * In some cases, like suspend to RAM or hibernation, It might be reasonable
  67  * to prohibit probing of devices as it could be unsafe.
  68  * Once defer_all_probes is true all drivers probes will be forcibly deferred.
  69  */
  70 static bool defer_all_probes;
  71
  72 /*
  73  * deferred_probe_work_func() - Retry probing devices in the active list.
  74  */
  75 static void deferred_probe_work_func(struct work_struct *work)
  76 {
  77         struct device *dev;
  78         struct device_private *private;
  79         /*
  80          * This block processes every device in the deferred 'active' list.
  81          * Each device is removed from the active list and passed to
  82          * bus_probe_device() to re-attempt the probe.  The loop continues
  83          * until every device in the active list is removed and retried.
  84          *
  85          * Note: Once the device is removed from the list and the mutex is
  86          * released, it is possible for the device get freed by another thread
  87          * and cause a illegal pointer dereference.  This code uses
  88          * get/put_device() to ensure the device structure cannot disappear
  89          * from under our feet.
  90          */
  91         mutex_lock(&deferred_probe_mutex);
  92         while (!list_empty(&deferred_probe_active_list)) {
  93                 private = list_first_entry(&deferred_probe_active_list,
  94                                         typeof(*dev->p), deferred_probe);
  95                 dev = private->device;
  96                 list_del_init(&private->deferred_probe);
  97
  98                 get_device(dev);
  99
 100                 /*
 101                  * Drop the mutex while probing each device; the probe path may
 102                  * manipulate the deferred list
 103                  */
 104                 mutex_unlock(&deferred_probe_mutex);
 105
 106                 /*
 107                  * Force the device to the end of the dpm_list since
 108                  * the PM code assumes that the order we add things to
 109                  * the list is a good order for suspend but deferred
 110                  * probe makes that very unsafe.
 111                  */
 112                 device_pm_move_to_tail(dev);
 113
 114                 dev_dbg(dev, "Retrying from deferred list\n");
 115                 bus_probe_device(dev);
 116                 mutex_lock(&deferred_probe_mutex);
 117
 118                 put_device(dev);
 119         }
 120         mutex_unlock(&deferred_probe_mutex);
 121 }
 122 static DECLARE_WORK(deferred_probe_work, deferred_probe_work_func);
 123
 124 void driver_deferred_probe_add(struct device *dev)
 125 {
 126         mutex_lock(&deferred_probe_mutex);
 127         if (list_empty(&dev->p->deferred_probe)) {
 128                 dev_dbg(dev, "Added to deferred list\n");
 129                 list_add_tail(&dev->p->deferred_probe, &deferred_probe_pending_list);
 130         }
 131         mutex_unlock(&deferred_probe_mutex);
 132 }
 133
 134 void driver_deferred_probe_del(struct device *dev)
 135 {
 136         mutex_lock(&deferred_probe_mutex);
 137         if (!list_empty(&dev->p->deferred_probe)) {
 138                 dev_dbg(dev, "Removed from deferred list\n");
 139                 list_del_init(&dev->p->deferred_probe);
 140                 kfree(dev->p->deferred_probe_reason);
 141                 dev->p->deferred_probe_reason = NULL;
 142         }
 143         mutex_unlock(&deferred_probe_mutex);
 144 }
 145
 146 static bool driver_deferred_probe_enable = false;
 147 /**
 148  * driver_deferred_probe_trigger() - Kick off re-probing deferred devices
 149  *
 150  * This functions moves all devices from the pending list to the active
 151  * list and schedules the deferred probe workqueue to process them.  It
 152  * should be called anytime a driver is successfully bound to a device.
 153  *
 154  * Note, there is a race condition in multi-threaded probe. In the case where
 155  * more than one device is probing at the same time, it is possible for one
 156  * probe to complete successfully while another is about to defer. If the second
 157  * depends on the first, then it will get put on the pending list after the
 158  * trigger event has already occurred and will be stuck there.
 159  *
 160  * The atomic 'deferred_trigger_count' is used to determine if a successful
 161  * trigger has occurred in the midst of probing a driver. If the trigger count
 162  * changes in the midst of a probe, then deferred processing should be triggered
 163  * again.
 164  */
 165 static void driver_deferred_probe_trigger(void)
 166 {
 167         if (!driver_deferred_probe_enable)
 168                 return;
 169
 170         /*
 171          * A successful probe means that all the devices in the pending list
 172          * should be triggered to be reprobed.  Move all the deferred devices
 173          * into the active list so they can be retried by the workqueue
 174          */
 175         mutex_lock(&deferred_probe_mutex);
 176         atomic_inc(&deferred_trigger_count);
 177         list_splice_tail_init(&deferred_probe_pending_list,
 178                               &deferred_probe_active_list);
 179         mutex_unlock(&deferred_probe_mutex);
 180
 181         /*
 182          * Kick the re-probe thread.  It may already be scheduled, but it is
 183          * safe to kick it again.
 184          */
 185         schedule_work(&deferred_probe_work);
 186 }
 187
 188 /**
 189  * device_block_probing() - Block/defer device's probes
 190  *
 191  *      It will disable probing of devices and defer their probes instead.
 192  */
 193 void device_block_probing(void)
 194 {
 195         defer_all_probes = true;
 196         /* sync with probes to avoid races. */
 197         wait_for_device_probe();
 198 }
 199
 200 /**
 201  * device_unblock_probing() - Unblock/enable device's probes
 202  *
 203  *      It will restore normal behavior and trigger re-probing of deferred
 204  * devices.
 205  */
 206 void device_unblock_probing(void)
 207 {
 208         defer_all_probes = false;
 209         driver_deferred_probe_trigger();
 210 }
 211
 212 /**
 213  * device_set_deferred_probe_reason() - Set defer probe reason message for device
 214  * @dev: the pointer to the struct device
 215  * @vaf: the pointer to va_format structure with message
 216  */
 217 void device_set_deferred_probe_reason(const struct device *dev, struct va_format *vaf)
 218 {
 219         const char *drv = dev_driver_string(dev);
 220
 221         mutex_lock(&deferred_probe_mutex);
 222
 223         kfree(dev->p->deferred_probe_reason);
 224         dev->p->deferred_probe_reason = kasprintf(GFP_KERNEL, "%s: %pV", drv, vaf);
 225
 226         mutex_unlock(&deferred_probe_mutex);
 227 }
 228
 229 /*
 230  * deferred_devs_show() - Show the devices in the deferred probe pending list.
 231  */
 232 static int deferred_devs_show(struct seq_file *s, void *data)
 233 {
 234         struct device_private *curr;
 235
 236         mutex_lock(&deferred_probe_mutex);
 237
 238         list_for_each_entry(curr, &deferred_probe_pending_list, deferred_probe)
 239                 seq_printf(s, "%s\t%s", dev_name(curr->device),
 240                            curr->device->p->deferred_probe_reason ?: "\n");
 241
 242         mutex_unlock(&deferred_probe_mutex);
 243
 244         return 0;
 245 }
 246 DEFINE_SHOW_ATTRIBUTE(deferred_devs);
 247
 248 int driver_deferred_probe_timeout;
 249 EXPORT_SYMBOL_GPL(driver_deferred_probe_timeout);
 250 static DECLARE_WAIT_QUEUE_HEAD(probe_timeout_waitqueue);
 251
 252 static int __init deferred_probe_timeout_setup(char *str)
 253 {
 254         int timeout;
 255
 256         if (!kstrtoint(str, 10, &timeout))
 257                 driver_deferred_probe_timeout = timeout;
 258         return 1;
 259 }
 260 __setup("deferred_probe_timeout=", deferred_probe_timeout_setup);
 261
 262 /**
 263  * driver_deferred_probe_check_state() - Check deferred probe state
 264  * @dev: device to check
 265  *
 266  * Return:
 267  * -ENODEV if initcalls have completed and modules are disabled.
 268  * -ETIMEDOUT if the deferred probe timeout was set and has expired
 269  *  and modules are enabled.
 270  * -EPROBE_DEFER in other cases.
 271  *
 272  * Drivers or subsystems can opt-in to calling this function instead of directly
 273  * returning -EPROBE_DEFER.
 274  */
 275 int driver_deferred_probe_check_state(struct device *dev)
 276 {
 277         if (!IS_ENABLED(CONFIG_MODULES) && initcalls_done) {
 278                 dev_warn(dev, "ignoring dependency for device, assuming no driver\n");
 279                 return -ENODEV;
 280         }
 281
 282         if (!driver_deferred_probe_timeout && initcalls_done) {
 283                 dev_warn(dev, "deferred probe timeout, ignoring dependency\n");
 284                 return -ETIMEDOUT;
 285         }
 286
 287         return -EPROBE_DEFER;
 288 }
 289
 290 static void deferred_probe_timeout_work_func(struct work_struct *work)
 291 {
 292         struct device_private *private, *p;
 293
 294         driver_deferred_probe_timeout = 0;
 295         driver_deferred_probe_trigger();
 296         flush_work(&deferred_probe_work);
 297
 298         list_for_each_entry_safe(private, p, &deferred_probe_pending_list, deferred_probe)
 299                 dev_info(private->device, "deferred probe pending\n");
 300         wake_up_all(&probe_timeout_waitqueue);
 301 }
 302 static DECLARE_DELAYED_WORK(deferred_probe_timeout_work, deferred_probe_timeout_work_func);
 303
 304 /**
 305  * deferred_probe_initcall() - Enable probing of deferred devices
 306  *
 307  * We don't want to get in the way when the bulk of drivers are getting probed.
 308  * Instead, this initcall makes sure that deferred probing is delayed until
 309  * late_initcall time.
 310  */
 311 static int deferred_probe_initcall(void)
 312 {
 313         deferred_devices = debugfs_create_file("devices_deferred", 0444, NULL,
 314                                                NULL, &deferred_devs_fops);
 315
 316         driver_deferred_probe_enable = true;
 317         driver_deferred_probe_trigger();
 318         /* Sort as many dependencies as possible before exiting initcalls */
 319         flush_work(&deferred_probe_work);
 320         initcalls_done = true;
 321
 322         /*
 323          * Trigger deferred probe again, this time we won't defer anything
 324          * that is optional
 325          */
 326         driver_deferred_probe_trigger();
 327         flush_work(&deferred_probe_work);
 328
 329         if (driver_deferred_probe_timeout > 0) {
 330                 schedule_delayed_work(&deferred_probe_timeout_work,
 331                         driver_deferred_probe_timeout * HZ);
 332         }
 333         return 0;
 334 }
 335 late_initcall(deferred_probe_initcall);
 336
 337 static void __exit deferred_probe_exit(void)
 338 {
 339         debugfs_remove_recursive(deferred_devices);
 340 }
 341 __exitcall(deferred_probe_exit);
 342
 343 /**
 344  * device_is_bound() - Check if device is bound to a driver
 345  * @dev: device to check
 346  *
 347  * Returns true if passed device has already finished probing successfully
 348  * against a driver.
 349  *
 350  * This function must be called with the device lock held.
 351  */
 352 bool device_is_bound(struct device *dev)
 353 {
 354         return dev->p && klist_node_attached(&dev->p->knode_driver);
 355 }
 356
 357 static void driver_bound(struct device *dev)
 358 {
 359         if (device_is_bound(dev)) {
 360                 pr_warn("%s: device %s already bound\n",
 361                         __func__, kobject_name(&dev->kobj));
 362                 return;
 363         }
 364
 365         pr_debug("driver: '%s': %s: bound to device '%s'\n", dev->driver->name,
 366                  __func__, dev_name(dev));
 367
 368         klist_add_tail(&dev->p->knode_driver, &dev->driver->p->klist_devices);
 369         device_links_driver_bound(dev);
 370
 371         device_pm_check_callbacks(dev);
 372
 373         /*
 374          * Reorder successfully probed devices to the end of the device list.
 375          * This ensures that suspend/resume order matches probe order, which
 376          * is usually what drivers rely on.
 377          */
 378         device_pm_move_to_tail(dev);
 379
 380         /*
 381          * Make sure the device is no longer in one of the deferred lists and
 382          * kick off retrying all pending devices
 383          */
 384         driver_deferred_probe_del(dev);
 385         driver_deferred_probe_trigger();
 386
 387         if (dev->bus)
 388                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 389                                              BUS_NOTIFY_BOUND_DRIVER, dev);
 390
 391         kobject_uevent(&dev->kobj, KOBJ_BIND);
 392 }
 393
 394 static ssize_t coredump_store(struct device *dev, struct device_attribute *attr,
 395                             const char *buf, size_t count)
 396 {
 397         device_lock(dev);
 398         dev->driver->coredump(dev);
 399         device_unlock(dev);
 400
 401         return count;
 402 }
 403 static DEVICE_ATTR_WO(coredump);
 404
 405 static int driver_sysfs_add(struct device *dev)
 406 {
 407         int ret;
 408
 409         if (dev->bus)
 410                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 411                                              BUS_NOTIFY_BIND_DRIVER, dev);
 412
 413         ret = sysfs_create_link(&dev->driver->p->kobj, &dev->kobj,
 414                                 kobject_name(&dev->kobj));
 415         if (ret)
 416                 goto fail;
 417
 418         ret = sysfs_create_link(&dev->kobj, &dev->driver->p->kobj,
 419                                 "driver");
 420         if (ret)
 421                 goto rm_dev;
 422
 423         if (!IS_ENABLED(CONFIG_DEV_COREDUMP) || !dev->driver->coredump ||
 424             !device_create_file(dev, &dev_attr_coredump))
 425                 return 0;
 426
 427         sysfs_remove_link(&dev->kobj, "driver");
 428
 429 rm_dev:
 430         sysfs_remove_link(&dev->driver->p->kobj,
 431                           kobject_name(&dev->kobj));
 432
 433 fail:
 434         return ret;
 435 }
 436
 437 static void driver_sysfs_remove(struct device *dev)
 438 {
 439         struct device_driver *drv = dev->driver;
 440
 441         if (drv) {
 442                 if (drv->coredump)
 443                         device_remove_file(dev, &dev_attr_coredump);
 444                 sysfs_remove_link(&drv->p->kobj, kobject_name(&dev->kobj));
 445                 sysfs_remove_link(&dev->kobj, "driver");
 446         }
 447 }
 448
 449 /**
 450  * device_bind_driver - bind a driver to one device.
 451  * @dev: device.
 452  *
 453  * Allow manual attachment of a driver to a device.
 454  * Caller must have already set @dev->driver.
 455  *
 456  * Note that this does not modify the bus reference count.
 457  * Please verify that is accounted for before calling this.
 458  * (It is ok to call with no other effort from a driver's probe() method.)
 459  *
 460  * This function must be called with the device lock held.
 461  */
 462 int device_bind_driver(struct device *dev)
 463 {
 464         int ret;
 465
 466         ret = driver_sysfs_add(dev);
 467         if (!ret)
 468                 driver_bound(dev);
 469         else if (dev->bus)
 470                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 471                                              BUS_NOTIFY_DRIVER_NOT_BOUND, dev);
 472         return ret;
 473 }
 474 EXPORT_SYMBOL_GPL(device_bind_driver);
 475
 476 static atomic_t probe_count = ATOMIC_INIT(0);
 477 static DECLARE_WAIT_QUEUE_HEAD(probe_waitqueue);
 478
 479 static void driver_deferred_probe_add_trigger(struct device *dev,
 480                                               int local_trigger_count)
 481 {
 482         driver_deferred_probe_add(dev);
 483         /* Did a trigger occur while probing? Need to re-trigger if yes */
 484         if (local_trigger_count != atomic_read(&deferred_trigger_count))
 485                 driver_deferred_probe_trigger();
 486 }
 487
 488 static ssize_t state_synced_show(struct device *dev,
 489                                  struct device_attribute *attr, char *buf)
 490 {
 491         bool val;
 492
 493         device_lock(dev);
 494         val = dev->state_synced;
 495         device_unlock(dev);
 496
 497         return sysfs_emit(buf, "%u\n", val);
 498 }
 499 static DEVICE_ATTR_RO(state_synced);
 500
 501 static int really_probe(struct device *dev, struct device_driver *drv)
 502 {
 503         int ret = -EPROBE_DEFER;
 504         int local_trigger_count = atomic_read(&deferred_trigger_count);
 505         bool test_remove = IS_ENABLED(CONFIG_DEBUG_TEST_DRIVER_REMOVE) &&
 506                            !drv->suppress_bind_attrs;
 507
 508         if (defer_all_probes) {
 509                 /*
 510                  * Value of defer_all_probes can be set only by
 511                  * device_block_probing() which, in turn, will call
 512                  * wait_for_device_probe() right after that to avoid any races.
 513                  */
 514                 dev_dbg(dev, "Driver %s force probe deferral\n", drv->name);
 515                 driver_deferred_probe_add(dev);
 516                 return ret;
 517         }
 518
 519         ret = device_links_check_suppliers(dev);
 520         if (ret == -EPROBE_DEFER)
 521                 driver_deferred_probe_add_trigger(dev, local_trigger_count);
 522         if (ret)
 523                 return ret;
 524
 525         atomic_inc(&probe_count);
 526         pr_debug("bus: '%s': %s: probing driver %s with device %s\n",
 527                  drv->bus->name, __func__, drv->name, dev_name(dev));
 528         if (!list_empty(&dev->devres_head)) {
 529                 dev_crit(dev, "Resources present before probing\n");
 530                 ret = -EBUSY;
 531                 goto done;
 532         }
 533
 534 re_probe:
 535         dev->driver = drv;
 536
 537         /* If using pinctrl, bind pins now before probing */
 538         ret = pinctrl_bind_pins(dev);
 539         if (ret)
 540                 goto pinctrl_bind_failed;
 541
 542         if (dev->bus->dma_configure) {
 543                 ret = dev->bus->dma_configure(dev);
 544                 if (ret)
 545                         goto probe_failed;
 546         }
 547
 548         if (driver_sysfs_add(dev)) {
 549                 pr_err("%s: driver_sysfs_add(%s) failed\n",
 550                        __func__, dev_name(dev));
 551                 goto probe_failed;
 552         }
 553
 554         if (dev->pm_domain && dev->pm_domain->activate) {
 555                 ret = dev->pm_domain->activate(dev);
 556                 if (ret)
 557                         goto probe_failed;
 558         }
 559
 560         if (dev->bus->probe) {
 561                 ret = dev->bus->probe(dev);
 562                 if (ret)
 563                         goto probe_failed;
 564         } else if (drv->probe) {
 565                 ret = drv->probe(dev);
 566                 if (ret)
 567                         goto probe_failed;
 568         }
 569
 570         if (device_add_groups(dev, drv->dev_groups)) {
 571                 dev_err(dev, "device_add_groups() failed\n");
 572                 goto dev_groups_failed;
 573         }
 574
 575         if (dev_has_sync_state(dev) &&
 576             device_create_file(dev, &dev_attr_state_synced)) {
 577                 dev_err(dev, "state_synced sysfs add failed\n");
 578                 goto dev_sysfs_state_synced_failed;
 579         }
 580
 581         if (test_remove) {
 582                 test_remove = false;
 583
 584                 device_remove_file(dev, &dev_attr_state_synced);
 585                 device_remove_groups(dev, drv->dev_groups);
 586
 587                 if (dev->bus->remove)
 588                         dev->bus->remove(dev);
 589                 else if (drv->remove)
 590                         drv->remove(dev);
 591
 592                 devres_release_all(dev);
 593                 driver_sysfs_remove(dev);
 594                 dev->driver = NULL;
 595                 dev_set_drvdata(dev, NULL);
 596                 if (dev->pm_domain && dev->pm_domain->dismiss)
 597                         dev->pm_domain->dismiss(dev);
 598                 pm_runtime_reinit(dev);
 599
 600                 goto re_probe;
 601         }
 602
 603         pinctrl_init_done(dev);
 604
 605         if (dev->pm_domain && dev->pm_domain->sync)
 606                 dev->pm_domain->sync(dev);
 607
 608         driver_bound(dev);
 609         ret = 1;
 610         pr_debug("bus: '%s': %s: bound device %s to driver %s\n",
 611                  drv->bus->name, __func__, dev_name(dev), drv->name);
 612         goto done;
 613
 614 dev_sysfs_state_synced_failed:
 615         device_remove_groups(dev, drv->dev_groups);
 616 dev_groups_failed:
 617         if (dev->bus->remove)
 618                 dev->bus->remove(dev);
 619         else if (drv->remove)
 620                 drv->remove(dev);
 621 probe_failed:
 622         if (dev->bus)
 623                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 624                                              BUS_NOTIFY_DRIVER_NOT_BOUND, dev);
 625 pinctrl_bind_failed:
 626         device_links_no_driver(dev);
 627         devres_release_all(dev);
 628         arch_teardown_dma_ops(dev);
 629         driver_sysfs_remove(dev);
 630         dev->driver = NULL;
 631         dev_set_drvdata(dev, NULL);
 632         if (dev->pm_domain && dev->pm_domain->dismiss)
 633                 dev->pm_domain->dismiss(dev);
 634         pm_runtime_reinit(dev);
 635         dev_pm_set_driver_flags(dev, 0);
 636
 637         switch (ret) {
 638         case -EPROBE_DEFER:
 639                 /* Driver requested deferred probing */
 640                 dev_dbg(dev, "Driver %s requests probe deferral\n", drv->name);
 641                 driver_deferred_probe_add_trigger(dev, local_trigger_count);
 642                 break;
 643         case -ENODEV:
 644         case -ENXIO:
 645                 pr_debug("%s: probe of %s rejects match %d\n",
 646                          drv->name, dev_name(dev), ret);
 647                 break;
 648         default:
 649                 /* driver matched but the probe failed */
 650                 pr_warn("%s: probe of %s failed with error %d\n",
 651                         drv->name, dev_name(dev), ret);
 652         }
 653         /*
 654          * Ignore errors returned by ->probe so that the next driver can try
 655          * its luck.
 656          */
 657         ret = 0;
 658 done:
 659         atomic_dec(&probe_count);
 660         wake_up_all(&probe_waitqueue);
 661         return ret;
 662 }
 663
 664 /*
 665  * For initcall_debug, show the driver probe time.
 666  */
 667 static int really_probe_debug(struct device *dev, struct device_driver *drv)
 668 {
 669         ktime_t calltime, rettime;
 670         int ret;
 671
 672         calltime = ktime_get();
 673         ret = really_probe(dev, drv);
 674         rettime = ktime_get();
 675         pr_debug("probe of %s returned %d after %lld usecs\n",
 676                  dev_name(dev), ret, ktime_us_delta(rettime, calltime));
 677         return ret;
 678 }
 679
 680 /**
 681  * driver_probe_done
 682  * Determine if the probe sequence is finished or not.
 683  *
 684  * Should somehow figure out how to use a semaphore, not an atomic variable...
 685  */
 686 int driver_probe_done(void)
 687 {
 688         int local_probe_count = atomic_read(&probe_count);
 689
 690         pr_debug("%s: probe_count = %d\n", __func__, local_probe_count);
 691         if (local_probe_count)
 692                 return -EBUSY;
 693         return 0;
 694 }
 695
 696 /**
 697  * wait_for_device_probe
 698  * Wait for device probing to be completed.
 699  */
 700 void wait_for_device_probe(void)
 701 {
 702         /* wait for probe timeout */
 703         wait_event(probe_timeout_waitqueue, !driver_deferred_probe_timeout);
 704
 705         /* wait for the deferred probe workqueue to finish */
 706         flush_work(&deferred_probe_work);
 707
 708         /* wait for the known devices to complete their probing */
 709         wait_event(probe_waitqueue, atomic_read(&probe_count) == 0);
 710         async_synchronize_full();
 711 }
 712 EXPORT_SYMBOL_GPL(wait_for_device_probe);
 713
 714 /**
 715  * driver_probe_device - attempt to bind device & driver together
 716  * @drv: driver to bind a device to
 717  * @dev: device to try to bind to the driver
 718  *
 719  * This function returns -ENODEV if the device is not registered,
 720  * 1 if the device is bound successfully and 0 otherwise.
 721  *
 722  * This function must be called with @dev lock held.  When called for a
 723  * USB interface, @dev->parent lock must be held as well.
 724  *
 725  * If the device has a parent, runtime-resume the parent before driver probing.
 726  */
 727 static int driver_probe_device(struct device_driver *drv, struct device *dev)
 728 {
 729         int ret = 0;
 730
 731         if (!device_is_registered(dev))
 732                 return -ENODEV;
 733
 734         pr_debug("bus: '%s': %s: matched device %s with driver %s\n",
 735                  drv->bus->name, __func__, dev_name(dev), drv->name);
 736
 737         pm_runtime_get_suppliers(dev);
 738         if (dev->parent)
 739                 pm_runtime_get_sync(dev->parent);
 740
 741         pm_runtime_barrier(dev);
 742         if (initcall_debug)
 743                 ret = really_probe_debug(dev, drv);
 744         else
 745                 ret = really_probe(dev, drv);
 746         pm_request_idle(dev);
 747
 748         if (dev->parent)
 749                 pm_runtime_put(dev->parent);
 750
 751         pm_runtime_put_suppliers(dev);
 752         return ret;
 753 }
 754
 755 static inline bool cmdline_requested_async_probing(const char *drv_name)
 756 {
 757         return parse_option_str(async_probe_drv_names, drv_name);
 758 }
 759
 760 /* The option format is "driver_async_probe=drv_name1,drv_name2,..." */
 761 static int __init save_async_options(char *buf)
 762 {
 763         if (strlen(buf) >= ASYNC_DRV_NAMES_MAX_LEN)
 764                 pr_warn("Too long list of driver names for 'driver_async_probe'!\n");
 765
 766         strlcpy(async_probe_drv_names, buf, ASYNC_DRV_NAMES_MAX_LEN);
 767         return 0;
 768 }
 769 __setup("driver_async_probe=", save_async_options);
 770
 771 bool driver_allows_async_probing(struct device_driver *drv)
 772 {
 773         switch (drv->probe_type) {
 774         case PROBE_PREFER_ASYNCHRONOUS:
 775                 return true;
 776
 777         case PROBE_FORCE_SYNCHRONOUS:
 778                 return false;
 779
 780         default:
 781                 if (cmdline_requested_async_probing(drv->name))
 782                         return true;
 783
 784                 if (module_requested_async_probing(drv->owner))
 785                         return true;
 786
 787                 return false;
 788         }
 789 }
 790
 791 struct device_attach_data {
 792         struct device *dev;
 793
 794         /*
 795          * Indicates whether we are are considering asynchronous probing or
 796          * not. Only initial binding after device or driver registration
 797          * (including deferral processing) may be done asynchronously, the
 798          * rest is always synchronous, as we expect it is being done by
 799          * request from userspace.
 800          */
 801         bool check_async;
 802
 803         /*
 804          * Indicates if we are binding synchronous or asynchronous drivers.
 805          * When asynchronous probing is enabled we'll execute 2 passes
 806          * over drivers: first pass doing synchronous probing and second
 807          * doing asynchronous probing (if synchronous did not succeed -
 808          * most likely because there was no driver requiring synchronous
 809          * probing - and we found asynchronous driver during first pass).
 810          * The 2 passes are done because we can't shoot asynchronous
 811          * probe for given device and driver from bus_for_each_drv() since
 812          * driver pointer is not guaranteed to stay valid once
 813          * bus_for_each_drv() iterates to the next driver on the bus.
 814          */
 815         bool want_async;
 816
 817         /*
 818          * We'll set have_async to 'true' if, while scanning for matching
 819          * driver, we'll encounter one that requests asynchronous probing.
 820          */
 821         bool have_async;
 822 };
 823
 824 static int __device_attach_driver(struct device_driver *drv, void *_data)
 825 {
 826         struct device_attach_data *data = _data;
 827         struct device *dev = data->dev;
 828         bool async_allowed;
 829         int ret;
 830
 831         ret = driver_match_device(drv, dev);
 832         if (ret == 0) {
 833                 /* no match */
 834                 return 0;
 835         } else if (ret == -EPROBE_DEFER) {
 836                 dev_dbg(dev, "Device match requests probe deferral\n");
 837                 driver_deferred_probe_add(dev);
 838         } else if (ret < 0) {
 839                 dev_dbg(dev, "Bus failed to match device: %d\n", ret);
 840                 return ret;
 841         } /* ret > 0 means positive match */
 842
 843         async_allowed = driver_allows_async_probing(drv);
 844
 845         if (async_allowed)
 846                 data->have_async = true;
 847
 848         if (data->check_async && async_allowed != data->want_async)
 849                 return 0;
 850
 851         return driver_probe_device(drv, dev);
 852 }
 853
 854 static void __device_attach_async_helper(void *_dev, async_cookie_t cookie)
 855 {
 856         struct device *dev = _dev;
 857         struct device_attach_data data = {
 858                 .dev            = dev,
 859                 .check_async    = true,
 860                 .want_async     = true,
 861         };
 862
 863         device_lock(dev);
 864
 865         /*
 866          * Check if device has already been removed or claimed. This may
 867          * happen with driver loading, device discovery/registration,
 868          * and deferred probe processing happens all at once with
 869          * multiple threads.
 870          */
 871         if (dev->p->dead || dev->driver)
 872                 goto out_unlock;
 873
 874         if (dev->parent)
 875                 pm_runtime_get_sync(dev->parent);
 876
 877         bus_for_each_drv(dev->bus, NULL, &data, __device_attach_driver);
 878         dev_dbg(dev, "async probe completed\n");
 879
 880         pm_request_idle(dev);
 881
 882         if (dev->parent)
 883                 pm_runtime_put(dev->parent);
 884 out_unlock:
 885         device_unlock(dev);
 886
 887         put_device(dev);
 888 }
 889
 890 static int __device_attach(struct device *dev, bool allow_async)
 891 {
 892         int ret = 0;
 893
 894         device_lock(dev);
 895         if (dev->p->dead) {
 896                 goto out_unlock;
 897         } else if (dev->driver) {
 898                 if (device_is_bound(dev)) {
 899                         ret = 1;
 900                         goto out_unlock;
 901                 }
 902                 ret = device_bind_driver(dev);
 903                 if (ret == 0)
 904                         ret = 1;
 905                 else {
 906                         dev->driver = NULL;
 907                         ret = 0;
 908                 }
 909         } else {
 910                 struct device_attach_data data = {
 911                         .dev = dev,
 912                         .check_async = allow_async,
 913                         .want_async = false,
 914                 };
 915
 916                 if (dev->parent)
 917                         pm_runtime_get_sync(dev->parent);
 918
 919                 ret = bus_for_each_drv(dev->bus, NULL, &data,
 920                                         __device_attach_driver);
 921                 if (!ret && allow_async && data.have_async) {
 922                         /*
 923                          * If we could not find appropriate driver
 924                          * synchronously and we are allowed to do
 925                          * async probes and there are drivers that
 926                          * want to probe asynchronously, we'll
 927                          * try them.
 928                          */
 929                         dev_dbg(dev, "scheduling asynchronous probe\n");
 930                         get_device(dev);
 931                         async_schedule_dev(__device_attach_async_helper, dev);
 932                 } else {
 933                         pm_request_idle(dev);
 934                 }
 935
 936                 if (dev->parent)
 937                         pm_runtime_put(dev->parent);
 938         }
 939 out_unlock:
 940         device_unlock(dev);
 941         return ret;
 942 }
 943
 944 /**
 945  * device_attach - try to attach device to a driver.
 946  * @dev: device.
 947  *
 948  * Walk the list of drivers that the bus has and call
 949  * driver_probe_device() for each pair. If a compatible
 950  * pair is found, break out and return.
 951  *
 952  * Returns 1 if the device was bound to a driver;
 953  * 0 if no matching driver was found;
 954  * -ENODEV if the device is not registered.
 955  *
 956  * When called for a USB interface, @dev->parent lock must be held.
 957  */
 958 int device_attach(struct device *dev)
 959 {
 960         return __device_attach(dev, false);
 961 }
 962 EXPORT_SYMBOL_GPL(device_attach);
 963
 964 void device_initial_probe(struct device *dev)
 965 {
 966         __device_attach(dev, true);
 967 }
 968
 969 /*
 970  * __device_driver_lock - acquire locks needed to manipulate dev->drv
 971  * @dev: Device we will update driver info for
 972  * @parent: Parent device. Needed if the bus requires parent lock
 973  *
 974  * This function will take the required locks for manipulating dev->drv.
 975  * Normally this will just be the @dev lock, but when called for a USB
 976  * interface, @parent lock will be held as well.
 977  */
 978 static void __device_driver_lock(struct device *dev, struct device *parent)
 979 {
 980         if (parent && dev->bus->need_parent_lock)
 981                 device_lock(parent);
 982         device_lock(dev);
 983 }
 984
 985 /*
 986  * __device_driver_unlock - release locks needed to manipulate dev->drv
 987  * @dev: Device we will update driver info for
 988  * @parent: Parent device. Needed if the bus requires parent lock
 989  *
 990  * This function will release the required locks for manipulating dev->drv.
 991  * Normally this will just be the the @dev lock, but when called for a
 992  * USB interface, @parent lock will be released as well.
 993  */
 994 static void __device_driver_unlock(struct device *dev, struct device *parent)
 995 {
 996         device_unlock(dev);
 997         if (parent && dev->bus->need_parent_lock)
 998                 device_unlock(parent);
 999 }
1000
1001 /**
1002  * device_driver_attach - attach a specific driver to a specific device
1003  * @drv: Driver to attach
1004  * @dev: Device to attach it to
1005  *
1006  * Manually attach driver to a device. Will acquire both @dev lock and
1007  * @dev->parent lock if needed.
1008  */
1009 int device_driver_attach(struct device_driver *drv, struct device *dev)
1010 {
1011         int ret = 0;
1012
1013         __device_driver_lock(dev, dev->parent);
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         return ret;
1025 }
1026
1027 static void __driver_attach_async_helper(void *_dev, async_cookie_t cookie)
1028 {
1029         struct device *dev = _dev;
1030         struct device_driver *drv;
1031         int ret = 0;
1032
1033         __device_driver_lock(dev, dev->parent);
1034
1035         drv = dev->p->async_driver;
1036
1037         /*
1038          * If device has been removed or someone has already successfully
1039          * bound a driver before us just skip the driver probe call.
1040          */
1041         if (!dev->p->dead && !dev->driver)
1042                 ret = driver_probe_device(drv, dev);
1043
1044         __device_driver_unlock(dev, dev->parent);
1045
1046         dev_dbg(dev, "driver %s async attach completed: %d\n", drv->name, ret);
1047
1048         put_device(dev);
1049 }
1050
1051 static int __driver_attach(struct device *dev, void *data)
1052 {
1053         struct device_driver *drv = data;
1054         int ret;
1055
1056         /*
1057          * Lock device and try to bind to it. We drop the error
1058          * here and always return 0, because we need to keep trying
1059          * to bind to devices and some drivers will return an error
1060          * simply if it didn't support the device.
1061          *
1062          * driver_probe_device() will spit a warning if there
1063          * is an error.
1064          */
1065
1066         ret = driver_match_device(drv, dev);
1067         if (ret == 0) {
1068                 /* no match */
1069                 return 0;
1070         } else if (ret == -EPROBE_DEFER) {
1071                 dev_dbg(dev, "Device match requests probe deferral\n");
1072                 driver_deferred_probe_add(dev);
1073         } else if (ret < 0) {
1074                 dev_dbg(dev, "Bus failed to match device: %d\n", ret);
1075                 return ret;
1076         } /* ret > 0 means positive match */
1077
1078         if (driver_allows_async_probing(drv)) {
1079                 /*
1080                  * Instead of probing the device synchronously we will
1081                  * probe it asynchronously to allow for more parallelism.
1082                  *
1083                  * We only take the device lock here in order to guarantee
1084                  * that the dev->driver and async_driver fields are protected
1085                  */
1086                 dev_dbg(dev, "probing driver %s asynchronously\n", drv->name);
1087                 device_lock(dev);
1088                 if (!dev->driver) {
1089                         get_device(dev);
1090                         dev->p->async_driver = drv;
1091                         async_schedule_dev(__driver_attach_async_helper, dev);
1092                 }
1093                 device_unlock(dev);
1094                 return 0;
1095         }
1096
1097         device_driver_attach(drv, dev);
1098
1099         return 0;
1100 }
1101
1102 /**
1103  * driver_attach - try to bind driver to devices.
1104  * @drv: driver.
1105  *
1106  * Walk the list of devices that the bus has on it and try to
1107  * match the driver with each one.  If driver_probe_device()
1108  * returns 0 and the @dev->driver is set, we've found a
1109  * compatible pair.
1110  */
1111 int driver_attach(struct device_driver *drv)
1112 {
1113         return bus_for_each_dev(drv->bus, NULL, drv, __driver_attach);
1114 }
1115 EXPORT_SYMBOL_GPL(driver_attach);
1116
1117 /*
1118  * __device_release_driver() must be called with @dev lock held.
1119  * When called for a USB interface, @dev->parent lock must be held as well.
1120  */
1121 static void __device_release_driver(struct device *dev, struct device *parent)
1122 {
1123         struct device_driver *drv;
1124
1125         drv = dev->driver;
1126         if (drv) {
1127                 pm_runtime_get_sync(dev);
1128
1129                 while (device_links_busy(dev)) {
1130                         __device_driver_unlock(dev, parent);
1131
1132                         device_links_unbind_consumers(dev);
1133
1134                         __device_driver_lock(dev, parent);
1135                         /*
1136                          * A concurrent invocation of the same function might
1137                          * have released the driver successfully while this one
1138                          * was waiting, so check for that.
1139                          */
1140                         if (dev->driver != drv) {
1141                                 pm_runtime_put(dev);
1142                                 return;
1143                         }
1144                 }
1145
1146                 driver_sysfs_remove(dev);
1147
1148                 if (dev->bus)
1149                         blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
1150                                                      BUS_NOTIFY_UNBIND_DRIVER,
1151                                                      dev);
1152
1153                 pm_runtime_put_sync(dev);
1154
1155                 device_remove_file(dev, &dev_attr_state_synced);
1156                 device_remove_groups(dev, drv->dev_groups);
1157
1158                 if (dev->bus && dev->bus->remove)
1159                         dev->bus->remove(dev);
1160                 else if (drv->remove)
1161                         drv->remove(dev);
1162
1163                 device_links_driver_cleanup(dev);
1164
1165                 devres_release_all(dev);
1166                 arch_teardown_dma_ops(dev);
1167                 dev->driver = NULL;
1168                 dev_set_drvdata(dev, NULL);
1169                 if (dev->pm_domain && dev->pm_domain->dismiss)
1170                         dev->pm_domain->dismiss(dev);
1171                 pm_runtime_reinit(dev);
1172                 dev_pm_set_driver_flags(dev, 0);
1173
1174                 klist_remove(&dev->p->knode_driver);
1175                 device_pm_check_callbacks(dev);
1176                 if (dev->bus)
1177                         blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
1178                                                      BUS_NOTIFY_UNBOUND_DRIVER,
1179                                                      dev);
1180
1181                 kobject_uevent(&dev->kobj, KOBJ_UNBIND);
1182         }
1183 }
1184
1185 void device_release_driver_internal(struct device *dev,
1186                                     struct device_driver *drv,
1187                                     struct device *parent)
1188 {
1189         __device_driver_lock(dev, parent);
1190
1191         if (!drv || drv == dev->driver)
1192                 __device_release_driver(dev, parent);
1193
1194         __device_driver_unlock(dev, parent);
1195 }
1196
1197 /**
1198  * device_release_driver - manually detach device from driver.
1199  * @dev: device.
1200  *
1201  * Manually detach device from driver.
1202  * When called for a USB interface, @dev->parent lock must be held.
1203  *
1204  * If this function is to be called with @dev->parent lock held, ensure that
1205  * the device's consumers are unbound in advance or that their locks can be
1206  * acquired under the @dev->parent lock.
1207  */
1208 void device_release_driver(struct device *dev)
1209 {
1210         /*
1211          * If anyone calls device_release_driver() recursively from
1212          * within their ->remove callback for the same device, they
1213          * will deadlock right here.
1214          */
1215         device_release_driver_internal(dev, NULL, NULL);
1216 }
1217 EXPORT_SYMBOL_GPL(device_release_driver);
1218
1219 /**
1220  * device_driver_detach - detach driver from a specific device
1221  * @dev: device to detach driver from
1222  *
1223  * Detach driver from device. Will acquire both @dev lock and @dev->parent
1224  * lock if needed.
1225  */
1226 void device_driver_detach(struct device *dev)
1227 {
1228         device_release_driver_internal(dev, NULL, dev->parent);
1229 }
1230
1231 /**
1232  * driver_detach - detach driver from all devices it controls.
1233  * @drv: driver.
1234  */
1235 void driver_detach(struct device_driver *drv)
1236 {
1237         struct device_private *dev_prv;
1238         struct device *dev;
1239
1240         if (driver_allows_async_probing(drv))
1241                 async_synchronize_full();
1242
1243         for (;;) {
1244                 spin_lock(&drv->p->klist_devices.k_lock);
1245                 if (list_empty(&drv->p->klist_devices.k_list)) {
1246                         spin_unlock(&drv->p->klist_devices.k_lock);
1247                         break;
1248                 }
1249                 dev_prv = list_last_entry(&drv->p->klist_devices.k_list,
1250                                      struct device_private,
1251                                      knode_driver.n_node);
1252                 dev = dev_prv->device;
1253                 get_device(dev);
1254                 spin_unlock(&drv->p->klist_devices.k_lock);
1255                 device_release_driver_internal(dev, drv, dev->parent);
1256                 put_device(dev);
1257         }
1258 }