linux/drivers/base/dd.c
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   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 */
  50static DEFINE_MUTEX(deferred_probe_mutex);
  51static LIST_HEAD(deferred_probe_pending_list);
  52static LIST_HEAD(deferred_probe_active_list);
  53static struct workqueue_struct *deferred_wq;
  54
  55/**
  56 * deferred_probe_work_func() - Retry probing devices in the active list.
  57 */
  58static 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}
 108static DECLARE_WORK(deferred_probe_work, deferred_probe_work_func);
 109
 110static 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
 120void 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
 130static 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 */
 138static 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 */
 167static 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}
 177late_initcall(deferred_probe_initcall);
 178
 179static 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
 204static 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
 224static 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 */
 248int 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}
 257EXPORT_SYMBOL_GPL(device_bind_driver);
 258
 259static atomic_t probe_count = ATOMIC_INIT(0);
 260static DECLARE_WAIT_QUEUE_HEAD(probe_waitqueue);
 261
 262static 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
 294probe_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;
 318done:
 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 */
 330int 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 */
 343void 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}
 349EXPORT_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 */
 362int 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
 379static 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 */
 403int 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        }
 424out_unlock:
 425        device_unlock(dev);
 426        return ret;
 427}
 428EXPORT_SYMBOL_GPL(device_attach);
 429
 430static 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 */
 468int driver_attach(struct device_driver *drv)
 469{
 470        return bus_for_each_dev(drv->bus, NULL, drv, __driver_attach);
 471}
 472EXPORT_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 */
 478static 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 */
 518void 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}
 529EXPORT_SYMBOL_GPL(device_release_driver);
 530
 531/**
 532 * driver_detach - detach driver from all devices it controls.
 533 * @drv: driver.
 534 */
 535void 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 */
 569void *dev_get_drvdata(const struct device *dev)
 570{
 571        if (dev && dev->p)
 572                return dev->p->driver_data;
 573        return NULL;
 574}
 575EXPORT_SYMBOL(dev_get_drvdata);
 576
 577int 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}
 589EXPORT_SYMBOL(dev_set_drvdata);
 590
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