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        /* Sort as many dependencies as possible before exiting initcalls */
 176        flush_workqueue(deferred_wq);
 177        return 0;
 178}
 179late_initcall(deferred_probe_initcall);
 180
 181static 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
 206static 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
 226static 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 */
 250int 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}
 259EXPORT_SYMBOL_GPL(device_bind_driver);
 260
 261static atomic_t probe_count = ATOMIC_INIT(0);
 262static DECLARE_WAIT_QUEUE_HEAD(probe_waitqueue);
 263
 264static 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
 296probe_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;
 320done:
 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 */
 332int 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 */
 345void 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}
 351EXPORT_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 */
 364int 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
 381static 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 */
 405int 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        }
 426out_unlock:
 427        device_unlock(dev);
 428        return ret;
 429}
 430EXPORT_SYMBOL_GPL(device_attach);
 431
 432static 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 */
 470int driver_attach(struct device_driver *drv)
 471{
 472        return bus_for_each_dev(drv->bus, NULL, drv, __driver_attach);
 473}
 474EXPORT_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 */
 480static 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 */
 520void 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}
 531EXPORT_SYMBOL_GPL(device_release_driver);
 532
 533/**
 534 * driver_detach - detach driver from all devices it controls.
 535 * @drv: driver.
 536 */
 537void 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 */
 571void *dev_get_drvdata(const struct device *dev)
 572{
 573        if (dev && dev->p)
 574                return dev->p->driver_data;
 575        return NULL;
 576}
 577EXPORT_SYMBOL(dev_get_drvdata);
 578
 579int 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}
 591EXPORT_SYMBOL(dev_set_drvdata);
 592
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