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