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         /* Sort as many dependencies as possible before exiting initcalls */
 164         flush_workqueue(deferred_wq);
 165         return 0;
 166 }
 167 late_initcall(deferred_probe_initcall);
 168
 169 static void driver_bound(struct device *dev)
 170 {
 171         if (klist_node_attached(&dev->p->knode_driver)) {
 172                 printk(KERN_WARNING "%s: device %s already bound\n",
 173                         __func__, kobject_name(&dev->kobj));
 174                 return;
 175         }
 176
 177         pr_debug("driver: '%s': %s: bound to device '%s'\n", dev_name(dev),
 178                  __func__, dev->driver->name);
 179
 180         klist_add_tail(&dev->p->knode_driver, &dev->driver->p->klist_devices);
 181
 182         /*
 183          * Make sure the device is no longer in one of the deferred lists and
 184          * kick off retrying all pending devices
 185          */
 186         driver_deferred_probe_del(dev);
 187         driver_deferred_probe_trigger();
 188
 189         if (dev->bus)
 190                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 191                                              BUS_NOTIFY_BOUND_DRIVER, dev);
 192 }
 193
 194 static int driver_sysfs_add(struct device *dev)
 195 {
 196         int ret;
 197
 198         if (dev->bus)
 199                 blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 200                                              BUS_NOTIFY_BIND_DRIVER, dev);
 201
 202         ret = sysfs_create_link(&dev->driver->p->kobj, &dev->kobj,
 203                           kobject_name(&dev->kobj));
 204         if (ret == 0) {
 205                 ret = sysfs_create_link(&dev->kobj, &dev->driver->p->kobj,
 206                                         "driver");
 207                 if (ret)
 208                         sysfs_remove_link(&dev->driver->p->kobj,
 209                                         kobject_name(&dev->kobj));
 210         }
 211         return ret;
 212 }
 213
 214 static void driver_sysfs_remove(struct device *dev)
 215 {
 216         struct device_driver *drv = dev->driver;
 217
 218         if (drv) {
 219                 sysfs_remove_link(&drv->p->kobj, kobject_name(&dev->kobj));
 220                 sysfs_remove_link(&dev->kobj, "driver");
 221         }
 222 }
 223
 224 /**
 225  * device_bind_driver - bind a driver to one device.
 226  * @dev: device.
 227  *
 228  * Allow manual attachment of a driver to a device.
 229  * Caller must have already set @dev->driver.
 230  *
 231  * Note that this does not modify the bus reference count
 232  * nor take the bus's rwsem. Please verify those are accounted
 233  * for before calling this. (It is ok to call with no other effort
 234  * from a driver's probe() method.)
 235  *
 236  * This function must be called with the device lock held.
 237  */
 238 int device_bind_driver(struct device *dev)
 239 {
 240         int ret;
 241
 242         ret = driver_sysfs_add(dev);
 243         if (!ret)
 244                 driver_bound(dev);
 245         return ret;
 246 }
 247 EXPORT_SYMBOL_GPL(device_bind_driver);
 248
 249 static atomic_t probe_count = ATOMIC_INIT(0);
 250 static DECLARE_WAIT_QUEUE_HEAD(probe_waitqueue);
 251
 252 static int really_probe(struct device *dev, struct device_driver *drv)
 253 {
 254         int ret = 0;
 255
 256         atomic_inc(&probe_count);
 257         pr_debug("bus: '%s': %s: probing driver %s with device %s\n",
 258                  drv->bus->name, __func__, drv->name, dev_name(dev));
 259         WARN_ON(!list_empty(&dev->devres_head));
 260
 261         dev->driver = drv;
 262         if (driver_sysfs_add(dev)) {
 263                 printk(KERN_ERR "%s: driver_sysfs_add(%s) failed\n",
 264                         __func__, dev_name(dev));
 265                 goto probe_failed;
 266         }
 267
 268         if (dev->bus->probe) {
 269                 ret = dev->bus->probe(dev);
 270                 if (ret)
 271                         goto probe_failed;
 272         } else if (drv->probe) {
 273                 ret = drv->probe(dev);
 274                 if (ret)
 275                         goto probe_failed;
 276         }
 277
 278         driver_bound(dev);
 279         ret = 1;
 280         pr_debug("bus: '%s': %s: bound device %s to driver %s\n",
 281                  drv->bus->name, __func__, dev_name(dev), drv->name);
 282         goto done;
 283
 284 probe_failed:
 285         devres_release_all(dev);
 286         driver_sysfs_remove(dev);
 287         dev->driver = NULL;
 288
 289         if (ret == -EPROBE_DEFER) {
 290                 /* Driver requested deferred probing */
 291                 dev_info(dev, "Driver %s requests probe deferral\n", drv->name);
 292                 driver_deferred_probe_add(dev);
 293         } else if (ret != -ENODEV && ret != -ENXIO) {
 294                 /* driver matched but the probe failed */
 295                 printk(KERN_WARNING
 296                        "%s: probe of %s failed with error %d\n",
 297                        drv->name, dev_name(dev), ret);
 298         } else {
 299                 pr_debug("%s: probe of %s rejects match %d\n",
 300                        drv->name, dev_name(dev), ret);
 301         }
 302         /*
 303          * Ignore errors returned by ->probe so that the next driver can try
 304          * its luck.
 305          */
 306         ret = 0;
 307 done:
 308         atomic_dec(&probe_count);
 309         wake_up(&probe_waitqueue);
 310         return ret;
 311 }
 312
 313 /**
 314  * driver_probe_done
 315  * Determine if the probe sequence is finished or not.
 316  *
 317  * Should somehow figure out how to use a semaphore, not an atomic variable...
 318  */
 319 int driver_probe_done(void)
 320 {
 321         pr_debug("%s: probe_count = %d\n", __func__,
 322                  atomic_read(&probe_count));
 323         if (atomic_read(&probe_count))
 324                 return -EBUSY;
 325         return 0;
 326 }
 327
 328 /**
 329  * wait_for_device_probe
 330  * Wait for device probing to be completed.
 331  */
 332 void wait_for_device_probe(void)
 333 {
 334         /* wait for the known devices to complete their probing */
 335         wait_event(probe_waitqueue, atomic_read(&probe_count) == 0);
 336         async_synchronize_full();
 337 }
 338 EXPORT_SYMBOL_GPL(wait_for_device_probe);
 339
 340 /**
 341  * driver_probe_device - attempt to bind device & driver together
 342  * @drv: driver to bind a device to
 343  * @dev: device to try to bind to the driver
 344  *
 345  * This function returns -ENODEV if the device is not registered,
 346  * 1 if the device is bound successfully and 0 otherwise.
 347  *
 348  * This function must be called with @dev lock held.  When called for a
 349  * USB interface, @dev->parent lock must be held as well.
 350  */
 351 int driver_probe_device(struct device_driver *drv, struct device *dev)
 352 {
 353         int ret = 0;
 354
 355         if (!device_is_registered(dev))
 356                 return -ENODEV;
 357
 358         pr_debug("bus: '%s': %s: matched device %s with driver %s\n",
 359                  drv->bus->name, __func__, dev_name(dev), drv->name);
 360
 361         pm_runtime_get_noresume(dev);
 362         pm_runtime_barrier(dev);
 363         ret = really_probe(dev, drv);
 364         pm_runtime_put_sync(dev);
 365
 366         return ret;
 367 }
 368
 369 static int __device_attach(struct device_driver *drv, void *data)
 370 {
 371         struct device *dev = data;
 372
 373         if (!driver_match_device(drv, dev))
 374                 return 0;
 375
 376         return driver_probe_device(drv, dev);
 377 }
 378
 379 /**
 380  * device_attach - try to attach device to a driver.
 381  * @dev: device.
 382  *
 383  * Walk the list of drivers that the bus has and call
 384  * driver_probe_device() for each pair. If a compatible
 385  * pair is found, break out and return.
 386  *
 387  * Returns 1 if the device was bound to a driver;
 388  * 0 if no matching driver was found;
 389  * -ENODEV if the device is not registered.
 390  *
 391  * When called for a USB interface, @dev->parent lock must be held.
 392  */
 393 int device_attach(struct device *dev)
 394 {
 395         int ret = 0;
 396
 397         device_lock(dev);
 398         if (dev->driver) {
 399                 if (klist_node_attached(&dev->p->knode_driver)) {
 400                         ret = 1;
 401                         goto out_unlock;
 402                 }
 403                 ret = device_bind_driver(dev);
 404                 if (ret == 0)
 405                         ret = 1;
 406                 else {
 407                         dev->driver = NULL;
 408                         ret = 0;
 409                 }
 410         } else {
 411                 pm_runtime_get_noresume(dev);
 412                 ret = bus_for_each_drv(dev->bus, NULL, dev, __device_attach);
 413                 pm_runtime_put_sync(dev);
 414         }
 415 out_unlock:
 416         device_unlock(dev);
 417         return ret;
 418 }
 419 EXPORT_SYMBOL_GPL(device_attach);
 420
 421 static int __driver_attach(struct device *dev, void *data)
 422 {
 423         struct device_driver *drv = data;
 424
 425         /*
 426          * Lock device and try to bind to it. We drop the error
 427          * here and always return 0, because we need to keep trying
 428          * to bind to devices and some drivers will return an error
 429          * simply if it didn't support the device.
 430          *
 431          * driver_probe_device() will spit a warning if there
 432          * is an error.
 433          */
 434
 435         if (!driver_match_device(drv, dev))
 436                 return 0;
 437
 438         if (dev->parent)        /* Needed for USB */
 439                 device_lock(dev->parent);
 440         device_lock(dev);
 441         if (!dev->driver)
 442                 driver_probe_device(drv, dev);
 443         device_unlock(dev);
 444         if (dev->parent)
 445                 device_unlock(dev->parent);
 446
 447         return 0;
 448 }
 449
 450 /**
 451  * driver_attach - try to bind driver to devices.
 452  * @drv: driver.
 453  *
 454  * Walk the list of devices that the bus has on it and try to
 455  * match the driver with each one.  If driver_probe_device()
 456  * returns 0 and the @dev->driver is set, we've found a
 457  * compatible pair.
 458  */
 459 int driver_attach(struct device_driver *drv)
 460 {
 461         return bus_for_each_dev(drv->bus, NULL, drv, __driver_attach);
 462 }
 463 EXPORT_SYMBOL_GPL(driver_attach);
 464
 465 /*
 466  * __device_release_driver() must be called with @dev lock held.
 467  * When called for a USB interface, @dev->parent lock must be held as well.
 468  */
 469 static void __device_release_driver(struct device *dev)
 470 {
 471         struct device_driver *drv;
 472
 473         drv = dev->driver;
 474         if (drv) {
 475                 pm_runtime_get_sync(dev);
 476
 477                 driver_sysfs_remove(dev);
 478
 479                 if (dev->bus)
 480                         blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 481                                                      BUS_NOTIFY_UNBIND_DRIVER,
 482                                                      dev);
 483
 484                 pm_runtime_put_sync(dev);
 485
 486                 if (dev->bus && dev->bus->remove)
 487                         dev->bus->remove(dev);
 488                 else if (drv->remove)
 489                         drv->remove(dev);
 490                 devres_release_all(dev);
 491                 dev->driver = NULL;
 492                 klist_remove(&dev->p->knode_driver);
 493                 if (dev->bus)
 494                         blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 495                                                      BUS_NOTIFY_UNBOUND_DRIVER,
 496                                                      dev);
 497
 498         }
 499 }
 500
 501 /**
 502  * device_release_driver - manually detach device from driver.
 503  * @dev: device.
 504  *
 505  * Manually detach device from driver.
 506  * When called for a USB interface, @dev->parent lock must be held.
 507  */
 508 void device_release_driver(struct device *dev)
 509 {
 510         /*
 511          * If anyone calls device_release_driver() recursively from
 512          * within their ->remove callback for the same device, they
 513          * will deadlock right here.
 514          */
 515         device_lock(dev);
 516         __device_release_driver(dev);
 517         device_unlock(dev);
 518 }
 519 EXPORT_SYMBOL_GPL(device_release_driver);
 520
 521 /**
 522  * driver_detach - detach driver from all devices it controls.
 523  * @drv: driver.
 524  */
 525 void driver_detach(struct device_driver *drv)
 526 {
 527         struct device_private *dev_prv;
 528         struct device *dev;
 529
 530         for (;;) {
 531                 spin_lock(&drv->p->klist_devices.k_lock);
 532                 if (list_empty(&drv->p->klist_devices.k_list)) {
 533                         spin_unlock(&drv->p->klist_devices.k_lock);
 534                         break;
 535                 }
 536                 dev_prv = list_entry(drv->p->klist_devices.k_list.prev,
 537                                      struct device_private,
 538                                      knode_driver.n_node);
 539                 dev = dev_prv->device;
 540                 get_device(dev);
 541                 spin_unlock(&drv->p->klist_devices.k_lock);
 542
 543                 if (dev->parent)        /* Needed for USB */
 544                         device_lock(dev->parent);
 545                 device_lock(dev);
 546                 if (dev->driver == drv)
 547                         __device_release_driver(dev);
 548                 device_unlock(dev);
 549                 if (dev->parent)
 550                         device_unlock(dev->parent);
 551                 put_device(dev);
 552         }
 553 }
 554
 555 /*
 556  * These exports can't be _GPL due to .h files using this within them, and it
 557  * might break something that was previously working...
 558  */
 559 void *dev_get_drvdata(const struct device *dev)
 560 {
 561         if (dev && dev->p)
 562                 return dev->p->driver_data;
 563         return NULL;
 564 }
 565 EXPORT_SYMBOL(dev_get_drvdata);
 566
 567 int dev_set_drvdata(struct device *dev, void *data)
 568 {
 569         int error;
 570
 571         if (!dev->p) {
 572                 error = device_private_init(dev);
 573                 if (error)
 574                         return error;
 575         }
 576         dev->p->driver_data = data;
 577         return 0;
 578 }
 579 EXPORT_SYMBOL(dev_set_drvdata);