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