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