linux/drivers/base/dd.c
<<
>>
Prefs
   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 */
  51static DEFINE_MUTEX(deferred_probe_mutex);
  52static LIST_HEAD(deferred_probe_pending_list);
  53static LIST_HEAD(deferred_probe_active_list);
  54static struct workqueue_struct *deferred_wq;
  55
  56/**
  57 * deferred_probe_work_func() - Retry probing devices in the active list.
  58 */
  59static 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}
 109static DECLARE_WORK(deferred_probe_work, deferred_probe_work_func);
 110
 111static 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
 121void 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
 131static 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 */
 139static 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 */
 168static 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        /* Sort as many dependencies as possible before exiting initcalls */
 177        flush_workqueue(deferred_wq);
 178        return 0;
 179}
 180late_initcall(deferred_probe_initcall);
 181
 182static void driver_bound(struct device *dev)
 183{
 184        if (klist_node_attached(&dev->p->knode_driver)) {
 185                printk(KERN_WARNING "%s: device %s already bound\n",
 186                        __func__, kobject_name(&dev->kobj));
 187                return;
 188        }
 189
 190        pr_debug("driver: '%s': %s: bound to device '%s'\n", dev_name(dev),
 191                 __func__, dev->driver->name);
 192
 193        klist_add_tail(&dev->p->knode_driver, &dev->driver->p->klist_devices);
 194
 195        /*
 196         * Make sure the device is no longer in one of the deferred lists and
 197         * kick off retrying all pending devices
 198         */
 199        driver_deferred_probe_del(dev);
 200        driver_deferred_probe_trigger();
 201
 202        if (dev->bus)
 203                blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 204                                             BUS_NOTIFY_BOUND_DRIVER, dev);
 205}
 206
 207static int driver_sysfs_add(struct device *dev)
 208{
 209        int ret;
 210
 211        if (dev->bus)
 212                blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 213                                             BUS_NOTIFY_BIND_DRIVER, dev);
 214
 215        ret = sysfs_create_link(&dev->driver->p->kobj, &dev->kobj,
 216                          kobject_name(&dev->kobj));
 217        if (ret == 0) {
 218                ret = sysfs_create_link(&dev->kobj, &dev->driver->p->kobj,
 219                                        "driver");
 220                if (ret)
 221                        sysfs_remove_link(&dev->driver->p->kobj,
 222                                        kobject_name(&dev->kobj));
 223        }
 224        return ret;
 225}
 226
 227static void driver_sysfs_remove(struct device *dev)
 228{
 229        struct device_driver *drv = dev->driver;
 230
 231        if (drv) {
 232                sysfs_remove_link(&drv->p->kobj, kobject_name(&dev->kobj));
 233                sysfs_remove_link(&dev->kobj, "driver");
 234        }
 235}
 236
 237/**
 238 * device_bind_driver - bind a driver to one device.
 239 * @dev: device.
 240 *
 241 * Allow manual attachment of a driver to a device.
 242 * Caller must have already set @dev->driver.
 243 *
 244 * Note that this does not modify the bus reference count
 245 * nor take the bus's rwsem. Please verify those are accounted
 246 * for before calling this. (It is ok to call with no other effort
 247 * from a driver's probe() method.)
 248 *
 249 * This function must be called with the device lock held.
 250 */
 251int device_bind_driver(struct device *dev)
 252{
 253        int ret;
 254
 255        ret = driver_sysfs_add(dev);
 256        if (!ret)
 257                driver_bound(dev);
 258        return ret;
 259}
 260EXPORT_SYMBOL_GPL(device_bind_driver);
 261
 262static atomic_t probe_count = ATOMIC_INIT(0);
 263static DECLARE_WAIT_QUEUE_HEAD(probe_waitqueue);
 264
 265static int really_probe(struct device *dev, struct device_driver *drv)
 266{
 267        int ret = 0;
 268
 269        atomic_inc(&probe_count);
 270        pr_debug("bus: '%s': %s: probing driver %s with device %s\n",
 271                 drv->bus->name, __func__, drv->name, dev_name(dev));
 272        WARN_ON(!list_empty(&dev->devres_head));
 273
 274        dev->driver = drv;
 275
 276        /* If using pinctrl, bind pins now before probing */
 277        ret = pinctrl_bind_pins(dev);
 278        if (ret)
 279                goto probe_failed;
 280
 281        if (driver_sysfs_add(dev)) {
 282                printk(KERN_ERR "%s: driver_sysfs_add(%s) failed\n",
 283                        __func__, dev_name(dev));
 284                goto probe_failed;
 285        }
 286
 287        if (dev->bus->probe) {
 288                ret = dev->bus->probe(dev);
 289                if (ret)
 290                        goto probe_failed;
 291        } else if (drv->probe) {
 292                ret = drv->probe(dev);
 293                if (ret)
 294                        goto probe_failed;
 295        }
 296
 297        driver_bound(dev);
 298        ret = 1;
 299        pr_debug("bus: '%s': %s: bound device %s to driver %s\n",
 300                 drv->bus->name, __func__, dev_name(dev), drv->name);
 301        goto done;
 302
 303probe_failed:
 304        devres_release_all(dev);
 305        driver_sysfs_remove(dev);
 306        dev->driver = NULL;
 307        dev_set_drvdata(dev, NULL);
 308
 309        if (ret == -EPROBE_DEFER) {
 310                /* Driver requested deferred probing */
 311                dev_info(dev, "Driver %s requests probe deferral\n", drv->name);
 312                driver_deferred_probe_add(dev);
 313        } else if (ret != -ENODEV && ret != -ENXIO) {
 314                /* driver matched but the probe failed */
 315                printk(KERN_WARNING
 316                       "%s: probe of %s failed with error %d\n",
 317                       drv->name, dev_name(dev), ret);
 318        } else {
 319                pr_debug("%s: probe of %s rejects match %d\n",
 320                       drv->name, dev_name(dev), ret);
 321        }
 322        /*
 323         * Ignore errors returned by ->probe so that the next driver can try
 324         * its luck.
 325         */
 326        ret = 0;
 327done:
 328        atomic_dec(&probe_count);
 329        wake_up(&probe_waitqueue);
 330        return ret;
 331}
 332
 333/**
 334 * driver_probe_done
 335 * Determine if the probe sequence is finished or not.
 336 *
 337 * Should somehow figure out how to use a semaphore, not an atomic variable...
 338 */
 339int driver_probe_done(void)
 340{
 341        pr_debug("%s: probe_count = %d\n", __func__,
 342                 atomic_read(&probe_count));
 343        if (atomic_read(&probe_count))
 344                return -EBUSY;
 345        return 0;
 346}
 347
 348/**
 349 * wait_for_device_probe
 350 * Wait for device probing to be completed.
 351 */
 352void wait_for_device_probe(void)
 353{
 354        /* wait for the known devices to complete their probing */
 355        wait_event(probe_waitqueue, atomic_read(&probe_count) == 0);
 356        async_synchronize_full();
 357}
 358EXPORT_SYMBOL_GPL(wait_for_device_probe);
 359
 360/**
 361 * driver_probe_device - attempt to bind device & driver together
 362 * @drv: driver to bind a device to
 363 * @dev: device to try to bind to the driver
 364 *
 365 * This function returns -ENODEV if the device is not registered,
 366 * 1 if the device is bound successfully and 0 otherwise.
 367 *
 368 * This function must be called with @dev lock held.  When called for a
 369 * USB interface, @dev->parent lock must be held as well.
 370 */
 371int driver_probe_device(struct device_driver *drv, struct device *dev)
 372{
 373        int ret = 0;
 374
 375        if (!device_is_registered(dev))
 376                return -ENODEV;
 377
 378        pr_debug("bus: '%s': %s: matched device %s with driver %s\n",
 379                 drv->bus->name, __func__, dev_name(dev), drv->name);
 380
 381        pm_runtime_barrier(dev);
 382        ret = really_probe(dev, drv);
 383        pm_request_idle(dev);
 384
 385        return ret;
 386}
 387
 388static int __device_attach(struct device_driver *drv, void *data)
 389{
 390        struct device *dev = data;
 391
 392        if (!driver_match_device(drv, dev))
 393                return 0;
 394
 395        return driver_probe_device(drv, dev);
 396}
 397
 398/**
 399 * device_attach - try to attach device to a driver.
 400 * @dev: device.
 401 *
 402 * Walk the list of drivers that the bus has and call
 403 * driver_probe_device() for each pair. If a compatible
 404 * pair is found, break out and return.
 405 *
 406 * Returns 1 if the device was bound to a driver;
 407 * 0 if no matching driver was found;
 408 * -ENODEV if the device is not registered.
 409 *
 410 * When called for a USB interface, @dev->parent lock must be held.
 411 */
 412int device_attach(struct device *dev)
 413{
 414        int ret = 0;
 415
 416        device_lock(dev);
 417        if (dev->driver) {
 418                if (klist_node_attached(&dev->p->knode_driver)) {
 419                        ret = 1;
 420                        goto out_unlock;
 421                }
 422                ret = device_bind_driver(dev);
 423                if (ret == 0)
 424                        ret = 1;
 425                else {
 426                        dev->driver = NULL;
 427                        ret = 0;
 428                }
 429        } else {
 430                ret = bus_for_each_drv(dev->bus, NULL, dev, __device_attach);
 431                pm_request_idle(dev);
 432        }
 433out_unlock:
 434        device_unlock(dev);
 435        return ret;
 436}
 437EXPORT_SYMBOL_GPL(device_attach);
 438
 439static int __driver_attach(struct device *dev, void *data)
 440{
 441        struct device_driver *drv = data;
 442
 443        /*
 444         * Lock device and try to bind to it. We drop the error
 445         * here and always return 0, because we need to keep trying
 446         * to bind to devices and some drivers will return an error
 447         * simply if it didn't support the device.
 448         *
 449         * driver_probe_device() will spit a warning if there
 450         * is an error.
 451         */
 452
 453        if (!driver_match_device(drv, dev))
 454                return 0;
 455
 456        if (dev->parent)        /* Needed for USB */
 457                device_lock(dev->parent);
 458        device_lock(dev);
 459        if (!dev->driver)
 460                driver_probe_device(drv, dev);
 461        device_unlock(dev);
 462        if (dev->parent)
 463                device_unlock(dev->parent);
 464
 465        return 0;
 466}
 467
 468/**
 469 * driver_attach - try to bind driver to devices.
 470 * @drv: driver.
 471 *
 472 * Walk the list of devices that the bus has on it and try to
 473 * match the driver with each one.  If driver_probe_device()
 474 * returns 0 and the @dev->driver is set, we've found a
 475 * compatible pair.
 476 */
 477int driver_attach(struct device_driver *drv)
 478{
 479        return bus_for_each_dev(drv->bus, NULL, drv, __driver_attach);
 480}
 481EXPORT_SYMBOL_GPL(driver_attach);
 482
 483/*
 484 * __device_release_driver() must be called with @dev lock held.
 485 * When called for a USB interface, @dev->parent lock must be held as well.
 486 */
 487static void __device_release_driver(struct device *dev)
 488{
 489        struct device_driver *drv;
 490
 491        drv = dev->driver;
 492        if (drv) {
 493                pm_runtime_get_sync(dev);
 494
 495                driver_sysfs_remove(dev);
 496
 497                if (dev->bus)
 498                        blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 499                                                     BUS_NOTIFY_UNBIND_DRIVER,
 500                                                     dev);
 501
 502                pm_runtime_put(dev);
 503
 504                if (dev->bus && dev->bus->remove)
 505                        dev->bus->remove(dev);
 506                else if (drv->remove)
 507                        drv->remove(dev);
 508                devres_release_all(dev);
 509                dev->driver = NULL;
 510                dev_set_drvdata(dev, NULL);
 511                klist_remove(&dev->p->knode_driver);
 512                if (dev->bus)
 513                        blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 514                                                     BUS_NOTIFY_UNBOUND_DRIVER,
 515                                                     dev);
 516
 517        }
 518}
 519
 520/**
 521 * device_release_driver - manually detach device from driver.
 522 * @dev: device.
 523 *
 524 * Manually detach device from driver.
 525 * When called for a USB interface, @dev->parent lock must be held.
 526 */
 527void device_release_driver(struct device *dev)
 528{
 529        /*
 530         * If anyone calls device_release_driver() recursively from
 531         * within their ->remove callback for the same device, they
 532         * will deadlock right here.
 533         */
 534        device_lock(dev);
 535        __device_release_driver(dev);
 536        device_unlock(dev);
 537}
 538EXPORT_SYMBOL_GPL(device_release_driver);
 539
 540/**
 541 * driver_detach - detach driver from all devices it controls.
 542 * @drv: driver.
 543 */
 544void driver_detach(struct device_driver *drv)
 545{
 546        struct device_private *dev_prv;
 547        struct device *dev;
 548
 549        for (;;) {
 550                spin_lock(&drv->p->klist_devices.k_lock);
 551                if (list_empty(&drv->p->klist_devices.k_list)) {
 552                        spin_unlock(&drv->p->klist_devices.k_lock);
 553                        break;
 554                }
 555                dev_prv = list_entry(drv->p->klist_devices.k_list.prev,
 556                                     struct device_private,
 557                                     knode_driver.n_node);
 558                dev = dev_prv->device;
 559                get_device(dev);
 560                spin_unlock(&drv->p->klist_devices.k_lock);
 561
 562                if (dev->parent)        /* Needed for USB */
 563                        device_lock(dev->parent);
 564                device_lock(dev);
 565                if (dev->driver == drv)
 566                        __device_release_driver(dev);
 567                device_unlock(dev);
 568                if (dev->parent)
 569                        device_unlock(dev->parent);
 570                put_device(dev);
 571        }
 572}
 573
 574/*
 575 * These exports can't be _GPL due to .h files using this within them, and it
 576 * might break something that was previously working...
 577 */
 578void *dev_get_drvdata(const struct device *dev)
 579{
 580        if (dev && dev->p)
 581                return dev->p->driver_data;
 582        return NULL;
 583}
 584EXPORT_SYMBOL(dev_get_drvdata);
 585
 586int dev_set_drvdata(struct device *dev, void *data)
 587{
 588        int error;
 589
 590        if (!dev->p) {
 591                error = device_private_init(dev);
 592                if (error)
 593                        return error;
 594        }
 595        dev->p->driver_data = data;
 596        return 0;
 597}
 598EXPORT_SYMBOL(dev_set_drvdata);
 599
lxr.linux.no kindly hosted by Redpill Linpro AS, provider of Linux consulting and operations services since 1995.