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         /* Sort as many dependencies as possible before exiting initcalls */
 176         flush_workqueue(deferred_wq);
 177         return 0;
 178 }
 179 late_initcall(deferred_probe_initcall);
 180
 181 static void driver_bound(struct device *dev)
 182 {
 183         if (klist_node_attached(&dev->p->knode_driver)) {
 184                 printk(KERN_WARNING "%s: device %s already bound\n",
 185                         __func__, kobject_name(&dev->kobj));
 186                 return;
 187         }
 188
 189         pr_debug("driver: '%s': %s: bound to device '%s'\n", dev_name(dev),
 190                  __func__, dev->driver->name);
 191
 192         klist_add_tail(&dev->p->knode_driver, &dev->driver->p->klist_devices);
 193
 194         /*
 195          * Make sure the device is no longer in one of the deferred lists and
 196          * kick off retrying all pending devices
 197          */
 198         driver_deferred_probe_del(dev);
 199         driver_deferred_probe_trigger();
 200
 201         if (dev->bus)
 202                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 203                                              BUS_NOTIFY_BOUND_DRIVER, dev);
 204 }
 205
 206 static int driver_sysfs_add(struct device *dev)
 207 {
 208         int ret;
 209
 210         if (dev->bus)
 211                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 212                                              BUS_NOTIFY_BIND_DRIVER, dev);
 213
 214         ret = sysfs_create_link(&dev->driver->p->kobj, &dev->kobj,
 215                           kobject_name(&dev->kobj));
 216         if (ret == 0) {
 217                 ret = sysfs_create_link(&dev->kobj, &dev->driver->p->kobj,
 218                                         "driver");
 219                 if (ret)
 220                         sysfs_remove_link(&dev->driver->p->kobj,
 221                                         kobject_name(&dev->kobj));
 222         }
 223         return ret;
 224 }
 225
 226 static void driver_sysfs_remove(struct device *dev)
 227 {
 228         struct device_driver *drv = dev->driver;
 229
 230         if (drv) {
 231                 sysfs_remove_link(&drv->p->kobj, kobject_name(&dev->kobj));
 232                 sysfs_remove_link(&dev->kobj, "driver");
 233         }
 234 }
 235
 236 /**
 237  * device_bind_driver - bind a driver to one device.
 238  * @dev: device.
 239  *
 240  * Allow manual attachment of a driver to a device.
 241  * Caller must have already set @dev->driver.
 242  *
 243  * Note that this does not modify the bus reference count
 244  * nor take the bus's rwsem. Please verify those are accounted
 245  * for before calling this. (It is ok to call with no other effort
 246  * from a driver's probe() method.)
 247  *
 248  * This function must be called with the device lock held.
 249  */
 250 int device_bind_driver(struct device *dev)
 251 {
 252         int ret;
 253
 254         ret = driver_sysfs_add(dev);
 255         if (!ret)
 256                 driver_bound(dev);
 257         return ret;
 258 }
 259 EXPORT_SYMBOL_GPL(device_bind_driver);
 260
 261 static atomic_t probe_count = ATOMIC_INIT(0);
 262 static DECLARE_WAIT_QUEUE_HEAD(probe_waitqueue);
 263
 264 static int really_probe(struct device *dev, struct device_driver *drv)
 265 {
 266         int ret = 0;
 267
 268         atomic_inc(&probe_count);
 269         pr_debug("bus: '%s': %s: probing driver %s with device %s\n",
 270                  drv->bus->name, __func__, drv->name, dev_name(dev));
 271         WARN_ON(!list_empty(&dev->devres_head));
 272
 273         dev->driver = drv;
 274         if (driver_sysfs_add(dev)) {
 275                 printk(KERN_ERR "%s: driver_sysfs_add(%s) failed\n",
 276                         __func__, dev_name(dev));
 277                 goto probe_failed;
 278         }
 279
 280         if (dev->bus->probe) {
 281                 ret = dev->bus->probe(dev);
 282                 if (ret)
 283                         goto probe_failed;
 284         } else if (drv->probe) {
 285                 ret = drv->probe(dev);
 286                 if (ret)
 287                         goto probe_failed;
 288         }
 289
 290         driver_bound(dev);
 291         ret = 1;
 292         pr_debug("bus: '%s': %s: bound device %s to driver %s\n",
 293                  drv->bus->name, __func__, dev_name(dev), drv->name);
 294         goto done;
 295
 296 probe_failed:
 297         devres_release_all(dev);
 298         driver_sysfs_remove(dev);
 299         dev->driver = NULL;
 300         dev_set_drvdata(dev, NULL);
 301
 302         if (ret == -EPROBE_DEFER) {
 303                 /* Driver requested deferred probing */
 304                 dev_info(dev, "Driver %s requests probe deferral\n", drv->name);
 305                 driver_deferred_probe_add(dev);
 306         } else if (ret != -ENODEV && ret != -ENXIO) {
 307                 /* driver matched but the probe failed */
 308                 printk(KERN_WARNING
 309                        "%s: probe of %s failed with error %d\n",
 310                        drv->name, dev_name(dev), ret);
 311         } else {
 312                 pr_debug("%s: probe of %s rejects match %d\n",
 313                        drv->name, dev_name(dev), ret);
 314         }
 315         /*
 316          * Ignore errors returned by ->probe so that the next driver can try
 317          * its luck.
 318          */
 319         ret = 0;
 320 done:
 321         atomic_dec(&probe_count);
 322         wake_up(&probe_waitqueue);
 323         return ret;
 324 }
 325
 326 /**
 327  * driver_probe_done
 328  * Determine if the probe sequence is finished or not.
 329  *
 330  * Should somehow figure out how to use a semaphore, not an atomic variable...
 331  */
 332 int driver_probe_done(void)
 333 {
 334         pr_debug("%s: probe_count = %d\n", __func__,
 335                  atomic_read(&probe_count));
 336         if (atomic_read(&probe_count))
 337                 return -EBUSY;
 338         return 0;
 339 }
 340
 341 /**
 342  * wait_for_device_probe
 343  * Wait for device probing to be completed.
 344  */
 345 void wait_for_device_probe(void)
 346 {
 347         /* wait for the known devices to complete their probing */
 348         wait_event(probe_waitqueue, atomic_read(&probe_count) == 0);
 349         async_synchronize_full();
 350 }
 351 EXPORT_SYMBOL_GPL(wait_for_device_probe);
 352
 353 /**
 354  * driver_probe_device - attempt to bind device & driver together
 355  * @drv: driver to bind a device to
 356  * @dev: device to try to bind to the driver
 357  *
 358  * This function returns -ENODEV if the device is not registered,
 359  * 1 if the device is bound successfully and 0 otherwise.
 360  *
 361  * This function must be called with @dev lock held.  When called for a
 362  * USB interface, @dev->parent lock must be held as well.
 363  */
 364 int driver_probe_device(struct device_driver *drv, struct device *dev)
 365 {
 366         int ret = 0;
 367
 368         if (!device_is_registered(dev))
 369                 return -ENODEV;
 370
 371         pr_debug("bus: '%s': %s: matched device %s with driver %s\n",
 372                  drv->bus->name, __func__, dev_name(dev), drv->name);
 373
 374         pm_runtime_barrier(dev);
 375         ret = really_probe(dev, drv);
 376         pm_runtime_idle(dev);
 377
 378         return ret;
 379 }
 380
 381 static int __device_attach(struct device_driver *drv, void *data)
 382 {
 383         struct device *dev = data;
 384
 385         if (!driver_match_device(drv, dev))
 386                 return 0;
 387
 388         return driver_probe_device(drv, dev);
 389 }
 390
 391 /**
 392  * device_attach - try to attach device to a driver.
 393  * @dev: device.
 394  *
 395  * Walk the list of drivers that the bus has and call
 396  * driver_probe_device() for each pair. If a compatible
 397  * pair is found, break out and return.
 398  *
 399  * Returns 1 if the device was bound to a driver;
 400  * 0 if no matching driver was found;
 401  * -ENODEV if the device is not registered.
 402  *
 403  * When called for a USB interface, @dev->parent lock must be held.
 404  */
 405 int device_attach(struct device *dev)
 406 {
 407         int ret = 0;
 408
 409         device_lock(dev);
 410         if (dev->driver) {
 411                 if (klist_node_attached(&dev->p->knode_driver)) {
 412                         ret = 1;
 413                         goto out_unlock;
 414                 }
 415                 ret = device_bind_driver(dev);
 416                 if (ret == 0)
 417                         ret = 1;
 418                 else {
 419                         dev->driver = NULL;
 420                         ret = 0;
 421                 }
 422         } else {
 423                 ret = bus_for_each_drv(dev->bus, NULL, dev, __device_attach);
 424                 pm_runtime_idle(dev);
 425         }
 426 out_unlock:
 427         device_unlock(dev);
 428         return ret;
 429 }
 430 EXPORT_SYMBOL_GPL(device_attach);
 431
 432 static int __driver_attach(struct device *dev, void *data)
 433 {
 434         struct device_driver *drv = data;
 435
 436         /*
 437          * Lock device and try to bind to it. We drop the error
 438          * here and always return 0, because we need to keep trying
 439          * to bind to devices and some drivers will return an error
 440          * simply if it didn't support the device.
 441          *
 442          * driver_probe_device() will spit a warning if there
 443          * is an error.
 444          */
 445
 446         if (!driver_match_device(drv, dev))
 447                 return 0;
 448
 449         if (dev->parent)        /* Needed for USB */
 450                 device_lock(dev->parent);
 451         device_lock(dev);
 452         if (!dev->driver)
 453                 driver_probe_device(drv, dev);
 454         device_unlock(dev);
 455         if (dev->parent)
 456                 device_unlock(dev->parent);
 457
 458         return 0;
 459 }
 460
 461 /**
 462  * driver_attach - try to bind driver to devices.
 463  * @drv: driver.
 464  *
 465  * Walk the list of devices that the bus has on it and try to
 466  * match the driver with each one.  If driver_probe_device()
 467  * returns 0 and the @dev->driver is set, we've found a
 468  * compatible pair.
 469  */
 470 int driver_attach(struct device_driver *drv)
 471 {
 472         return bus_for_each_dev(drv->bus, NULL, drv, __driver_attach);
 473 }
 474 EXPORT_SYMBOL_GPL(driver_attach);
 475
 476 /*
 477  * __device_release_driver() must be called with @dev lock held.
 478  * When called for a USB interface, @dev->parent lock must be held as well.
 479  */
 480 static void __device_release_driver(struct device *dev)
 481 {
 482         struct device_driver *drv;
 483
 484         drv = dev->driver;
 485         if (drv) {
 486                 pm_runtime_get_sync(dev);
 487
 488                 driver_sysfs_remove(dev);
 489
 490                 if (dev->bus)
 491                         blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 492                                                      BUS_NOTIFY_UNBIND_DRIVER,
 493                                                      dev);
 494
 495                 pm_runtime_put_sync(dev);
 496
 497                 if (dev->bus && dev->bus->remove)
 498                         dev->bus->remove(dev);
 499                 else if (drv->remove)
 500                         drv->remove(dev);
 501                 devres_release_all(dev);
 502                 dev->driver = NULL;
 503                 dev_set_drvdata(dev, NULL);
 504                 klist_remove(&dev->p->knode_driver);
 505                 if (dev->bus)
 506                         blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 507                                                      BUS_NOTIFY_UNBOUND_DRIVER,
 508                                                      dev);
 509
 510         }
 511 }
 512
 513 /**
 514  * device_release_driver - manually detach device from driver.
 515  * @dev: device.
 516  *
 517  * Manually detach device from driver.
 518  * When called for a USB interface, @dev->parent lock must be held.
 519  */
 520 void device_release_driver(struct device *dev)
 521 {
 522         /*
 523          * If anyone calls device_release_driver() recursively from
 524          * within their ->remove callback for the same device, they
 525          * will deadlock right here.
 526          */
 527         device_lock(dev);
 528         __device_release_driver(dev);
 529         device_unlock(dev);
 530 }
 531 EXPORT_SYMBOL_GPL(device_release_driver);
 532
 533 /**
 534  * driver_detach - detach driver from all devices it controls.
 535  * @drv: driver.
 536  */
 537 void driver_detach(struct device_driver *drv)
 538 {
 539         struct device_private *dev_prv;
 540         struct device *dev;
 541
 542         for (;;) {
 543                 spin_lock(&drv->p->klist_devices.k_lock);
 544                 if (list_empty(&drv->p->klist_devices.k_list)) {
 545                         spin_unlock(&drv->p->klist_devices.k_lock);
 546                         break;
 547                 }
 548                 dev_prv = list_entry(drv->p->klist_devices.k_list.prev,
 549                                      struct device_private,
 550                                      knode_driver.n_node);
 551                 dev = dev_prv->device;
 552                 get_device(dev);
 553                 spin_unlock(&drv->p->klist_devices.k_lock);
 554
 555                 if (dev->parent)        /* Needed for USB */
 556                         device_lock(dev->parent);
 557                 device_lock(dev);
 558                 if (dev->driver == drv)
 559                         __device_release_driver(dev);
 560                 device_unlock(dev);
 561                 if (dev->parent)
 562                         device_unlock(dev->parent);
 563                 put_device(dev);
 564         }
 565 }
 566
 567 /*
 568  * These exports can't be _GPL due to .h files using this within them, and it
 569  * might break something that was previously working...
 570  */
 571 void *dev_get_drvdata(const struct device *dev)
 572 {
 573         if (dev && dev->p)
 574                 return dev->p->driver_data;
 575         return NULL;
 576 }
 577 EXPORT_SYMBOL(dev_get_drvdata);
 578
 579 int dev_set_drvdata(struct device *dev, void *data)
 580 {
 581         int error;
 582
 583         if (!dev->p) {
 584                 error = device_private_init(dev);
 585                 if (error)
 586                         return error;
 587         }
 588         dev->p->driver_data = data;
 589         return 0;
 590 }
 591 EXPORT_SYMBOL(dev_set_drvdata);