drivers/base/dd.c

   1 /*
   2  * drivers/base/dd.c - The core device/driver interactions.
   3  *
   4  * This file contains the (sometimes tricky) code that controls the
   5  * interactions between devices and drivers, which primarily includes
   6  * driver binding and unbinding.
   7  *
   8  * All of this code used to exist in drivers/base/bus.c, but was
   9  * relocated to here in the name of compartmentalization (since it wasn't
  10  * strictly code just for the 'struct bus_type'.
  11  *
  12  * Copyright (c) 2002-5 Patrick Mochel
  13  * Copyright (c) 2002-3 Open Source Development Labs
  14  * Copyright (c) 2007-2009 Greg Kroah-Hartman <gregkh@suse.de>
  15  * Copyright (c) 2007-2009 Novell Inc.
  16  *
  17  * This file is released under the GPLv2
  18  */
  19
  20 #include <linux/device.h>
  21 #include <linux/delay.h>
  22 #include <linux/module.h>
  23 #include <linux/kthread.h>
  24 #include <linux/wait.h>
  25 #include <linux/async.h>
  26 #include <linux/pm_runtime.h>
  27 #include <linux/pinctrl/devinfo.h>
  28
  29 #include "base.h"
  30 #include "power/power.h"
  31
  32 /*
  33  * Deferred Probe infrastructure.
  34  *
  35  * Sometimes driver probe order matters, but the kernel doesn't always have
  36  * dependency information which means some drivers will get probed before a
  37  * resource it depends on is available.  For example, an SDHCI driver may
  38  * first need a GPIO line from an i2c GPIO controller before it can be
  39  * initialized.  If a required resource is not available yet, a driver can
  40  * request probing to be deferred by returning -EPROBE_DEFER from its probe hook
  41  *
  42  * Deferred probe maintains two lists of devices, a pending list and an active
  43  * list.  A driver returning -EPROBE_DEFER causes the device to be added to the
  44  * pending list.  A successful driver probe will trigger moving all devices
  45  * from the pending to the active list so that the workqueue will eventually
  46  * retry them.
  47  *
  48  * The deferred_probe_mutex must be held any time the deferred_probe_*_list
  49  * of the (struct device*)->p->deferred_probe pointers are manipulated
  50  */
  51 static DEFINE_MUTEX(deferred_probe_mutex);
  52 static LIST_HEAD(deferred_probe_pending_list);
  53 static LIST_HEAD(deferred_probe_active_list);
  54 static struct workqueue_struct *deferred_wq;
  55 static atomic_t deferred_trigger_count = ATOMIC_INIT(0);
  56
  57 /*
  58  * deferred_probe_work_func() - Retry probing devices in the active list.
  59  */
  60 static void deferred_probe_work_func(struct work_struct *work)
  61 {
  62         struct device *dev;
  63         struct device_private *private;
  64         /*
  65          * This block processes every device in the deferred 'active' list.
  66          * Each device is removed from the active list and passed to
  67          * bus_probe_device() to re-attempt the probe.  The loop continues
  68          * until every device in the active list is removed and retried.
  69          *
  70          * Note: Once the device is removed from the list and the mutex is
  71          * released, it is possible for the device get freed by another thread
  72          * and cause a illegal pointer dereference.  This code uses
  73          * get/put_device() to ensure the device structure cannot disappear
  74          * from under our feet.
  75          */
  76         mutex_lock(&deferred_probe_mutex);
  77         while (!list_empty(&deferred_probe_active_list)) {
  78                 private = list_first_entry(&deferred_probe_active_list,
  79                                         typeof(*dev->p), deferred_probe);
  80                 dev = private->device;
  81                 list_del_init(&private->deferred_probe);
  82
  83                 get_device(dev);
  84
  85                 /*
  86                  * Drop the mutex while probing each device; the probe path may
  87                  * manipulate the deferred list
  88                  */
  89                 mutex_unlock(&deferred_probe_mutex);
  90
  91                 /*
  92                  * Force the device to the end of the dpm_list since
  93                  * the PM code assumes that the order we add things to
  94                  * the list is a good order for suspend but deferred
  95                  * probe makes that very unsafe.
  96                  */
  97                 device_pm_lock();
  98                 device_pm_move_last(dev);
  99                 device_pm_unlock();
 100
 101                 dev_dbg(dev, "Retrying from deferred list\n");
 102                 bus_probe_device(dev);
 103
 104                 mutex_lock(&deferred_probe_mutex);
 105
 106                 put_device(dev);
 107         }
 108         mutex_unlock(&deferred_probe_mutex);
 109 }
 110 static DECLARE_WORK(deferred_probe_work, deferred_probe_work_func);
 111
 112 static void driver_deferred_probe_add(struct device *dev)
 113 {
 114         mutex_lock(&deferred_probe_mutex);
 115         if (list_empty(&dev->p->deferred_probe)) {
 116                 dev_dbg(dev, "Added to deferred list\n");
 117                 list_add_tail(&dev->p->deferred_probe, &deferred_probe_pending_list);
 118         }
 119         mutex_unlock(&deferred_probe_mutex);
 120 }
 121
 122 void driver_deferred_probe_del(struct device *dev)
 123 {
 124         mutex_lock(&deferred_probe_mutex);
 125         if (!list_empty(&dev->p->deferred_probe)) {
 126                 dev_dbg(dev, "Removed from deferred list\n");
 127                 list_del_init(&dev->p->deferred_probe);
 128         }
 129         mutex_unlock(&deferred_probe_mutex);
 130 }
 131
 132 static bool driver_deferred_probe_enable = false;
 133 /**
 134  * driver_deferred_probe_trigger() - Kick off re-probing deferred devices
 135  *
 136  * This functions moves all devices from the pending list to the active
 137  * list and schedules the deferred probe workqueue to process them.  It
 138  * should be called anytime a driver is successfully bound to a device.
 139  *
 140  * Note, there is a race condition in multi-threaded probe. In the case where
 141  * more than one device is probing at the same time, it is possible for one
 142  * probe to complete successfully while another is about to defer. If the second
 143  * depends on the first, then it will get put on the pending list after the
 144  * trigger event has already occured and will be stuck there.
 145  *
 146  * The atomic 'deferred_trigger_count' is used to determine if a successful
 147  * trigger has occurred in the midst of probing a driver. If the trigger count
 148  * changes in the midst of a probe, then deferred processing should be triggered
 149  * again.
 150  */
 151 static void driver_deferred_probe_trigger(void)
 152 {
 153         if (!driver_deferred_probe_enable)
 154                 return;
 155
 156         /*
 157          * A successful probe means that all the devices in the pending list
 158          * should be triggered to be reprobed.  Move all the deferred devices
 159          * into the active list so they can be retried by the workqueue
 160          */
 161         mutex_lock(&deferred_probe_mutex);
 162         atomic_inc(&deferred_trigger_count);
 163         list_splice_tail_init(&deferred_probe_pending_list,
 164                               &deferred_probe_active_list);
 165         mutex_unlock(&deferred_probe_mutex);
 166
 167         /*
 168          * Kick the re-probe thread.  It may already be scheduled, but it is
 169          * safe to kick it again.
 170          */
 171         queue_work(deferred_wq, &deferred_probe_work);
 172 }
 173
 174 /**
 175  * deferred_probe_initcall() - Enable probing of deferred devices
 176  *
 177  * We don't want to get in the way when the bulk of drivers are getting probed.
 178  * Instead, this initcall makes sure that deferred probing is delayed until
 179  * late_initcall time.
 180  */
 181 static int deferred_probe_initcall(void)
 182 {
 183         deferred_wq = create_singlethread_workqueue("deferwq");
 184         if (WARN_ON(!deferred_wq))
 185                 return -ENOMEM;
 186
 187         driver_deferred_probe_enable = true;
 188         driver_deferred_probe_trigger();
 189         /* Sort as many dependencies as possible before exiting initcalls */
 190         flush_workqueue(deferred_wq);
 191         return 0;
 192 }
 193 late_initcall(deferred_probe_initcall);
 194
 195 static void driver_bound(struct device *dev)
 196 {
 197         if (klist_node_attached(&dev->p->knode_driver)) {
 198                 printk(KERN_WARNING "%s: device %s already bound\n",
 199                         __func__, kobject_name(&dev->kobj));
 200                 return;
 201         }
 202
 203         pr_debug("driver: '%s': %s: bound to device '%s'\n", dev->driver->name,
 204                  __func__, dev_name(dev));
 205
 206         klist_add_tail(&dev->p->knode_driver, &dev->driver->p->klist_devices);
 207
 208         /*
 209          * Make sure the device is no longer in one of the deferred lists and
 210          * kick off retrying all pending devices
 211          */
 212         driver_deferred_probe_del(dev);
 213         driver_deferred_probe_trigger();
 214
 215         if (dev->bus)
 216                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 217                                              BUS_NOTIFY_BOUND_DRIVER, dev);
 218 }
 219
 220 static int driver_sysfs_add(struct device *dev)
 221 {
 222         int ret;
 223
 224         if (dev->bus)
 225                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 226                                              BUS_NOTIFY_BIND_DRIVER, dev);
 227
 228         ret = sysfs_create_link(&dev->driver->p->kobj, &dev->kobj,
 229                           kobject_name(&dev->kobj));
 230         if (ret == 0) {
 231                 ret = sysfs_create_link(&dev->kobj, &dev->driver->p->kobj,
 232                                         "driver");
 233                 if (ret)
 234                         sysfs_remove_link(&dev->driver->p->kobj,
 235                                         kobject_name(&dev->kobj));
 236         }
 237         return ret;
 238 }
 239
 240 static void driver_sysfs_remove(struct device *dev)
 241 {
 242         struct device_driver *drv = dev->driver;
 243
 244         if (drv) {
 245                 sysfs_remove_link(&drv->p->kobj, kobject_name(&dev->kobj));
 246                 sysfs_remove_link(&dev->kobj, "driver");
 247         }
 248 }
 249
 250 /**
 251  * device_bind_driver - bind a driver to one device.
 252  * @dev: device.
 253  *
 254  * Allow manual attachment of a driver to a device.
 255  * Caller must have already set @dev->driver.
 256  *
 257  * Note that this does not modify the bus reference count
 258  * nor take the bus's rwsem. Please verify those are accounted
 259  * for before calling this. (It is ok to call with no other effort
 260  * from a driver's probe() method.)
 261  *
 262  * This function must be called with the device lock held.
 263  */
 264 int device_bind_driver(struct device *dev)
 265 {
 266         int ret;
 267
 268         ret = driver_sysfs_add(dev);
 269         if (!ret)
 270                 driver_bound(dev);
 271         return ret;
 272 }
 273 EXPORT_SYMBOL_GPL(device_bind_driver);
 274
 275 static atomic_t probe_count = ATOMIC_INIT(0);
 276 static DECLARE_WAIT_QUEUE_HEAD(probe_waitqueue);
 277
 278 static int really_probe(struct device *dev, struct device_driver *drv)
 279 {
 280         int ret = 0;
 281         int local_trigger_count = atomic_read(&deferred_trigger_count);
 282
 283         atomic_inc(&probe_count);
 284         pr_debug("bus: '%s': %s: probing driver %s with device %s\n",
 285                  drv->bus->name, __func__, drv->name, dev_name(dev));
 286         WARN_ON(!list_empty(&dev->devres_head));
 287
 288         dev->driver = drv;
 289
 290         /* If using pinctrl, bind pins now before probing */
 291         ret = pinctrl_bind_pins(dev);
 292         if (ret)
 293                 goto probe_failed;
 294
 295         if (driver_sysfs_add(dev)) {
 296                 printk(KERN_ERR "%s: driver_sysfs_add(%s) failed\n",
 297                         __func__, dev_name(dev));
 298                 goto probe_failed;
 299         }
 300
 301         if (dev->pm_domain && dev->pm_domain->activate) {
 302                 ret = dev->pm_domain->activate(dev);
 303                 if (ret)
 304                         goto probe_failed;
 305         }
 306
 307         if (dev->bus->probe) {
 308                 ret = dev->bus->probe(dev);
 309                 if (ret)
 310                         goto probe_failed;
 311         } else if (drv->probe) {
 312                 ret = drv->probe(dev);
 313                 if (ret)
 314                         goto probe_failed;
 315         }
 316
 317         if (dev->pm_domain && dev->pm_domain->sync)
 318                 dev->pm_domain->sync(dev);
 319
 320         driver_bound(dev);
 321         ret = 1;
 322         pr_debug("bus: '%s': %s: bound device %s to driver %s\n",
 323                  drv->bus->name, __func__, dev_name(dev), drv->name);
 324         goto done;
 325
 326 probe_failed:
 327         devres_release_all(dev);
 328         driver_sysfs_remove(dev);
 329         dev->driver = NULL;
 330         dev_set_drvdata(dev, NULL);
 331         if (dev->pm_domain && dev->pm_domain->dismiss)
 332                 dev->pm_domain->dismiss(dev);
 333
 334         switch (ret) {
 335         case -EPROBE_DEFER:
 336                 /* Driver requested deferred probing */
 337                 dev_dbg(dev, "Driver %s requests probe deferral\n", drv->name);
 338                 driver_deferred_probe_add(dev);
 339                 /* Did a trigger occur while probing? Need to re-trigger if yes */
 340                 if (local_trigger_count != atomic_read(&deferred_trigger_count))
 341                         driver_deferred_probe_trigger();
 342                 break;
 343         case -ENODEV:
 344         case -ENXIO:
 345                 pr_debug("%s: probe of %s rejects match %d\n",
 346                          drv->name, dev_name(dev), ret);
 347                 break;
 348         default:
 349                 /* driver matched but the probe failed */
 350                 printk(KERN_WARNING
 351                        "%s: probe of %s failed with error %d\n",
 352                        drv->name, dev_name(dev), ret);
 353         }
 354         /*
 355          * Ignore errors returned by ->probe so that the next driver can try
 356          * its luck.
 357          */
 358         ret = 0;
 359 done:
 360         atomic_dec(&probe_count);
 361         wake_up(&probe_waitqueue);
 362         return ret;
 363 }
 364
 365 /**
 366  * driver_probe_done
 367  * Determine if the probe sequence is finished or not.
 368  *
 369  * Should somehow figure out how to use a semaphore, not an atomic variable...
 370  */
 371 int driver_probe_done(void)
 372 {
 373         pr_debug("%s: probe_count = %d\n", __func__,
 374                  atomic_read(&probe_count));
 375         if (atomic_read(&probe_count))
 376                 return -EBUSY;
 377         return 0;
 378 }
 379
 380 /**
 381  * wait_for_device_probe
 382  * Wait for device probing to be completed.
 383  */
 384 void wait_for_device_probe(void)
 385 {
 386         /* wait for the known devices to complete their probing */
 387         wait_event(probe_waitqueue, atomic_read(&probe_count) == 0);
 388         async_synchronize_full();
 389 }
 390 EXPORT_SYMBOL_GPL(wait_for_device_probe);
 391
 392 /**
 393  * driver_probe_device - attempt to bind device & driver together
 394  * @drv: driver to bind a device to
 395  * @dev: device to try to bind to the driver
 396  *
 397  * This function returns -ENODEV if the device is not registered,
 398  * 1 if the device is bound successfully and 0 otherwise.
 399  *
 400  * This function must be called with @dev lock held.  When called for a
 401  * USB interface, @dev->parent lock must be held as well.
 402  */
 403 int driver_probe_device(struct device_driver *drv, struct device *dev)
 404 {
 405         int ret = 0;
 406
 407         if (!device_is_registered(dev))
 408                 return -ENODEV;
 409
 410         pr_debug("bus: '%s': %s: matched device %s with driver %s\n",
 411                  drv->bus->name, __func__, dev_name(dev), drv->name);
 412
 413         pm_runtime_barrier(dev);
 414         ret = really_probe(dev, drv);
 415         pm_request_idle(dev);
 416
 417         return ret;
 418 }
 419
 420 static int __device_attach(struct device_driver *drv, void *data)
 421 {
 422         struct device *dev = data;
 423
 424         if (!driver_match_device(drv, dev))
 425                 return 0;
 426
 427         return driver_probe_device(drv, dev);
 428 }
 429
 430 /**
 431  * device_attach - try to attach device to a driver.
 432  * @dev: device.
 433  *
 434  * Walk the list of drivers that the bus has and call
 435  * driver_probe_device() for each pair. If a compatible
 436  * pair is found, break out and return.
 437  *
 438  * Returns 1 if the device was bound to a driver;
 439  * 0 if no matching driver was found;
 440  * -ENODEV if the device is not registered.
 441  *
 442  * When called for a USB interface, @dev->parent lock must be held.
 443  */
 444 int device_attach(struct device *dev)
 445 {
 446         int ret = 0;
 447
 448         device_lock(dev);
 449         if (dev->driver) {
 450                 if (klist_node_attached(&dev->p->knode_driver)) {
 451                         ret = 1;
 452                         goto out_unlock;
 453                 }
 454                 ret = device_bind_driver(dev);
 455                 if (ret == 0)
 456                         ret = 1;
 457                 else {
 458                         dev->driver = NULL;
 459                         ret = 0;
 460                 }
 461         } else {
 462                 ret = bus_for_each_drv(dev->bus, NULL, dev, __device_attach);
 463                 pm_request_idle(dev);
 464         }
 465 out_unlock:
 466         device_unlock(dev);
 467         return ret;
 468 }
 469 EXPORT_SYMBOL_GPL(device_attach);
 470
 471 static int __driver_attach(struct device *dev, void *data)
 472 {
 473         struct device_driver *drv = data;
 474
 475         /*
 476          * Lock device and try to bind to it. We drop the error
 477          * here and always return 0, because we need to keep trying
 478          * to bind to devices and some drivers will return an error
 479          * simply if it didn't support the device.
 480          *
 481          * driver_probe_device() will spit a warning if there
 482          * is an error.
 483          */
 484
 485         if (!driver_match_device(drv, dev))
 486                 return 0;
 487
 488         if (dev->parent)        /* Needed for USB */
 489                 device_lock(dev->parent);
 490         device_lock(dev);
 491         if (!dev->driver)
 492                 driver_probe_device(drv, dev);
 493         device_unlock(dev);
 494         if (dev->parent)
 495                 device_unlock(dev->parent);
 496
 497         return 0;
 498 }
 499
 500 /**
 501  * driver_attach - try to bind driver to devices.
 502  * @drv: driver.
 503  *
 504  * Walk the list of devices that the bus has on it and try to
 505  * match the driver with each one.  If driver_probe_device()
 506  * returns 0 and the @dev->driver is set, we've found a
 507  * compatible pair.
 508  */
 509 int driver_attach(struct device_driver *drv)
 510 {
 511         return bus_for_each_dev(drv->bus, NULL, drv, __driver_attach);
 512 }
 513 EXPORT_SYMBOL_GPL(driver_attach);
 514
 515 /*
 516  * __device_release_driver() must be called with @dev lock held.
 517  * When called for a USB interface, @dev->parent lock must be held as well.
 518  */
 519 static void __device_release_driver(struct device *dev)
 520 {
 521         struct device_driver *drv;
 522
 523         drv = dev->driver;
 524         if (drv) {
 525                 pm_runtime_get_sync(dev);
 526
 527                 driver_sysfs_remove(dev);
 528
 529                 if (dev->bus)
 530                         blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 531                                                      BUS_NOTIFY_UNBIND_DRIVER,
 532                                                      dev);
 533
 534                 pm_runtime_put_sync(dev);
 535
 536                 if (dev->bus && dev->bus->remove)
 537                         dev->bus->remove(dev);
 538                 else if (drv->remove)
 539                         drv->remove(dev);
 540                 devres_release_all(dev);
 541                 dev->driver = NULL;
 542                 dev_set_drvdata(dev, NULL);
 543                 if (dev->pm_domain && dev->pm_domain->dismiss)
 544                         dev->pm_domain->dismiss(dev);
 545
 546                 klist_remove(&dev->p->knode_driver);
 547                 if (dev->bus)
 548                         blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 549                                                      BUS_NOTIFY_UNBOUND_DRIVER,
 550                                                      dev);
 551
 552         }
 553 }
 554
 555 /**
 556  * device_release_driver - manually detach device from driver.
 557  * @dev: device.
 558  *
 559  * Manually detach device from driver.
 560  * When called for a USB interface, @dev->parent lock must be held.
 561  */
 562 void device_release_driver(struct device *dev)
 563 {
 564         /*
 565          * If anyone calls device_release_driver() recursively from
 566          * within their ->remove callback for the same device, they
 567          * will deadlock right here.
 568          */
 569         device_lock(dev);
 570         __device_release_driver(dev);
 571         device_unlock(dev);
 572 }
 573 EXPORT_SYMBOL_GPL(device_release_driver);
 574
 575 /**
 576  * driver_detach - detach driver from all devices it controls.
 577  * @drv: driver.
 578  */
 579 void driver_detach(struct device_driver *drv)
 580 {
 581         struct device_private *dev_prv;
 582         struct device *dev;
 583
 584         for (;;) {
 585                 spin_lock(&drv->p->klist_devices.k_lock);
 586                 if (list_empty(&drv->p->klist_devices.k_list)) {
 587                         spin_unlock(&drv->p->klist_devices.k_lock);
 588                         break;
 589                 }
 590                 dev_prv = list_entry(drv->p->klist_devices.k_list.prev,
 591                                      struct device_private,
 592                                      knode_driver.n_node);
 593                 dev = dev_prv->device;
 594                 get_device(dev);
 595                 spin_unlock(&drv->p->klist_devices.k_lock);
 596
 597                 if (dev->parent)        /* Needed for USB */
 598                         device_lock(dev->parent);
 599                 device_lock(dev);
 600                 if (dev->driver == drv)
 601                         __device_release_driver(dev);
 602                 device_unlock(dev);
 603                 if (dev->parent)
 604                         device_unlock(dev->parent);
 605                 put_device(dev);
 606         }
 607 }