linux/drivers/base/bus.c
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   1/*
   2 * bus.c - bus driver management
   3 *
   4 * Copyright (c) 2002-3 Patrick Mochel
   5 * Copyright (c) 2002-3 Open Source Development Labs
   6 * Copyright (c) 2007 Greg Kroah-Hartman <gregkh@suse.de>
   7 * Copyright (c) 2007 Novell Inc.
   8 *
   9 * This file is released under the GPLv2
  10 *
  11 */
  12
  13#include <linux/device.h>
  14#include <linux/module.h>
  15#include <linux/errno.h>
  16#include <linux/slab.h>
  17#include <linux/init.h>
  18#include <linux/string.h>
  19#include <linux/mutex.h>
  20#include "base.h"
  21#include "power/power.h"
  22
  23/* /sys/devices/system */
  24static struct kset *system_kset;
  25
  26#define to_bus_attr(_attr) container_of(_attr, struct bus_attribute, attr)
  27
  28/*
  29 * sysfs bindings for drivers
  30 */
  31
  32#define to_drv_attr(_attr) container_of(_attr, struct driver_attribute, attr)
  33
  34
  35static int __must_check bus_rescan_devices_helper(struct device *dev,
  36                                                void *data);
  37
  38static struct bus_type *bus_get(struct bus_type *bus)
  39{
  40        if (bus) {
  41                kset_get(&bus->p->subsys);
  42                return bus;
  43        }
  44        return NULL;
  45}
  46
  47static void bus_put(struct bus_type *bus)
  48{
  49        if (bus)
  50                kset_put(&bus->p->subsys);
  51}
  52
  53static ssize_t drv_attr_show(struct kobject *kobj, struct attribute *attr,
  54                             char *buf)
  55{
  56        struct driver_attribute *drv_attr = to_drv_attr(attr);
  57        struct driver_private *drv_priv = to_driver(kobj);
  58        ssize_t ret = -EIO;
  59
  60        if (drv_attr->show)
  61                ret = drv_attr->show(drv_priv->driver, buf);
  62        return ret;
  63}
  64
  65static ssize_t drv_attr_store(struct kobject *kobj, struct attribute *attr,
  66                              const char *buf, size_t count)
  67{
  68        struct driver_attribute *drv_attr = to_drv_attr(attr);
  69        struct driver_private *drv_priv = to_driver(kobj);
  70        ssize_t ret = -EIO;
  71
  72        if (drv_attr->store)
  73                ret = drv_attr->store(drv_priv->driver, buf, count);
  74        return ret;
  75}
  76
  77static const struct sysfs_ops driver_sysfs_ops = {
  78        .show   = drv_attr_show,
  79        .store  = drv_attr_store,
  80};
  81
  82static void driver_release(struct kobject *kobj)
  83{
  84        struct driver_private *drv_priv = to_driver(kobj);
  85
  86        pr_debug("driver: '%s': %s\n", kobject_name(kobj), __func__);
  87        kfree(drv_priv);
  88}
  89
  90static struct kobj_type driver_ktype = {
  91        .sysfs_ops      = &driver_sysfs_ops,
  92        .release        = driver_release,
  93};
  94
  95/*
  96 * sysfs bindings for buses
  97 */
  98static ssize_t bus_attr_show(struct kobject *kobj, struct attribute *attr,
  99                             char *buf)
 100{
 101        struct bus_attribute *bus_attr = to_bus_attr(attr);
 102        struct subsys_private *subsys_priv = to_subsys_private(kobj);
 103        ssize_t ret = 0;
 104
 105        if (bus_attr->show)
 106                ret = bus_attr->show(subsys_priv->bus, buf);
 107        return ret;
 108}
 109
 110static ssize_t bus_attr_store(struct kobject *kobj, struct attribute *attr,
 111                              const char *buf, size_t count)
 112{
 113        struct bus_attribute *bus_attr = to_bus_attr(attr);
 114        struct subsys_private *subsys_priv = to_subsys_private(kobj);
 115        ssize_t ret = 0;
 116
 117        if (bus_attr->store)
 118                ret = bus_attr->store(subsys_priv->bus, buf, count);
 119        return ret;
 120}
 121
 122static const struct sysfs_ops bus_sysfs_ops = {
 123        .show   = bus_attr_show,
 124        .store  = bus_attr_store,
 125};
 126
 127int bus_create_file(struct bus_type *bus, struct bus_attribute *attr)
 128{
 129        int error;
 130        if (bus_get(bus)) {
 131                error = sysfs_create_file(&bus->p->subsys.kobj, &attr->attr);
 132                bus_put(bus);
 133        } else
 134                error = -EINVAL;
 135        return error;
 136}
 137EXPORT_SYMBOL_GPL(bus_create_file);
 138
 139void bus_remove_file(struct bus_type *bus, struct bus_attribute *attr)
 140{
 141        if (bus_get(bus)) {
 142                sysfs_remove_file(&bus->p->subsys.kobj, &attr->attr);
 143                bus_put(bus);
 144        }
 145}
 146EXPORT_SYMBOL_GPL(bus_remove_file);
 147
 148static struct kobj_type bus_ktype = {
 149        .sysfs_ops      = &bus_sysfs_ops,
 150};
 151
 152static int bus_uevent_filter(struct kset *kset, struct kobject *kobj)
 153{
 154        struct kobj_type *ktype = get_ktype(kobj);
 155
 156        if (ktype == &bus_ktype)
 157                return 1;
 158        return 0;
 159}
 160
 161static const struct kset_uevent_ops bus_uevent_ops = {
 162        .filter = bus_uevent_filter,
 163};
 164
 165static struct kset *bus_kset;
 166
 167/* Manually detach a device from its associated driver. */
 168static ssize_t driver_unbind(struct device_driver *drv,
 169                             const char *buf, size_t count)
 170{
 171        struct bus_type *bus = bus_get(drv->bus);
 172        struct device *dev;
 173        int err = -ENODEV;
 174
 175        dev = bus_find_device_by_name(bus, NULL, buf);
 176        if (dev && dev->driver == drv) {
 177                if (dev->parent)        /* Needed for USB */
 178                        device_lock(dev->parent);
 179                device_release_driver(dev);
 180                if (dev->parent)
 181                        device_unlock(dev->parent);
 182                err = count;
 183        }
 184        put_device(dev);
 185        bus_put(bus);
 186        return err;
 187}
 188static DRIVER_ATTR(unbind, S_IWUSR, NULL, driver_unbind);
 189
 190/*
 191 * Manually attach a device to a driver.
 192 * Note: the driver must want to bind to the device,
 193 * it is not possible to override the driver's id table.
 194 */
 195static ssize_t driver_bind(struct device_driver *drv,
 196                           const char *buf, size_t count)
 197{
 198        struct bus_type *bus = bus_get(drv->bus);
 199        struct device *dev;
 200        int err = -ENODEV;
 201
 202        dev = bus_find_device_by_name(bus, NULL, buf);
 203        if (dev && dev->driver == NULL && driver_match_device(drv, dev)) {
 204                if (dev->parent)        /* Needed for USB */
 205                        device_lock(dev->parent);
 206                device_lock(dev);
 207                err = driver_probe_device(drv, dev);
 208                device_unlock(dev);
 209                if (dev->parent)
 210                        device_unlock(dev->parent);
 211
 212                if (err > 0) {
 213                        /* success */
 214                        err = count;
 215                } else if (err == 0) {
 216                        /* driver didn't accept device */
 217                        err = -ENODEV;
 218                }
 219        }
 220        put_device(dev);
 221        bus_put(bus);
 222        return err;
 223}
 224static DRIVER_ATTR(bind, S_IWUSR, NULL, driver_bind);
 225
 226static ssize_t show_drivers_autoprobe(struct bus_type *bus, char *buf)
 227{
 228        return sprintf(buf, "%d\n", bus->p->drivers_autoprobe);
 229}
 230
 231static ssize_t store_drivers_autoprobe(struct bus_type *bus,
 232                                       const char *buf, size_t count)
 233{
 234        if (buf[0] == '0')
 235                bus->p->drivers_autoprobe = 0;
 236        else
 237                bus->p->drivers_autoprobe = 1;
 238        return count;
 239}
 240
 241static ssize_t store_drivers_probe(struct bus_type *bus,
 242                                   const char *buf, size_t count)
 243{
 244        struct device *dev;
 245
 246        dev = bus_find_device_by_name(bus, NULL, buf);
 247        if (!dev)
 248                return -ENODEV;
 249        if (bus_rescan_devices_helper(dev, NULL) != 0)
 250                return -EINVAL;
 251        return count;
 252}
 253
 254static struct device *next_device(struct klist_iter *i)
 255{
 256        struct klist_node *n = klist_next(i);
 257        struct device *dev = NULL;
 258        struct device_private *dev_prv;
 259
 260        if (n) {
 261                dev_prv = to_device_private_bus(n);
 262                dev = dev_prv->device;
 263        }
 264        return dev;
 265}
 266
 267/**
 268 * bus_for_each_dev - device iterator.
 269 * @bus: bus type.
 270 * @start: device to start iterating from.
 271 * @data: data for the callback.
 272 * @fn: function to be called for each device.
 273 *
 274 * Iterate over @bus's list of devices, and call @fn for each,
 275 * passing it @data. If @start is not NULL, we use that device to
 276 * begin iterating from.
 277 *
 278 * We check the return of @fn each time. If it returns anything
 279 * other than 0, we break out and return that value.
 280 *
 281 * NOTE: The device that returns a non-zero value is not retained
 282 * in any way, nor is its refcount incremented. If the caller needs
 283 * to retain this data, it should do so, and increment the reference
 284 * count in the supplied callback.
 285 */
 286int bus_for_each_dev(struct bus_type *bus, struct device *start,
 287                     void *data, int (*fn)(struct device *, void *))
 288{
 289        struct klist_iter i;
 290        struct device *dev;
 291        int error = 0;
 292
 293        if (!bus || !bus->p)
 294                return -EINVAL;
 295
 296        klist_iter_init_node(&bus->p->klist_devices, &i,
 297                             (start ? &start->p->knode_bus : NULL));
 298        while ((dev = next_device(&i)) && !error)
 299                error = fn(dev, data);
 300        klist_iter_exit(&i);
 301        return error;
 302}
 303EXPORT_SYMBOL_GPL(bus_for_each_dev);
 304
 305/**
 306 * bus_find_device - device iterator for locating a particular device.
 307 * @bus: bus type
 308 * @start: Device to begin with
 309 * @data: Data to pass to match function
 310 * @match: Callback function to check device
 311 *
 312 * This is similar to the bus_for_each_dev() function above, but it
 313 * returns a reference to a device that is 'found' for later use, as
 314 * determined by the @match callback.
 315 *
 316 * The callback should return 0 if the device doesn't match and non-zero
 317 * if it does.  If the callback returns non-zero, this function will
 318 * return to the caller and not iterate over any more devices.
 319 */
 320struct device *bus_find_device(struct bus_type *bus,
 321                               struct device *start, void *data,
 322                               int (*match)(struct device *dev, void *data))
 323{
 324        struct klist_iter i;
 325        struct device *dev;
 326
 327        if (!bus || !bus->p)
 328                return NULL;
 329
 330        klist_iter_init_node(&bus->p->klist_devices, &i,
 331                             (start ? &start->p->knode_bus : NULL));
 332        while ((dev = next_device(&i)))
 333                if (match(dev, data) && get_device(dev))
 334                        break;
 335        klist_iter_exit(&i);
 336        return dev;
 337}
 338EXPORT_SYMBOL_GPL(bus_find_device);
 339
 340static int match_name(struct device *dev, void *data)
 341{
 342        const char *name = data;
 343
 344        return sysfs_streq(name, dev_name(dev));
 345}
 346
 347/**
 348 * bus_find_device_by_name - device iterator for locating a particular device of a specific name
 349 * @bus: bus type
 350 * @start: Device to begin with
 351 * @name: name of the device to match
 352 *
 353 * This is similar to the bus_find_device() function above, but it handles
 354 * searching by a name automatically, no need to write another strcmp matching
 355 * function.
 356 */
 357struct device *bus_find_device_by_name(struct bus_type *bus,
 358                                       struct device *start, const char *name)
 359{
 360        return bus_find_device(bus, start, (void *)name, match_name);
 361}
 362EXPORT_SYMBOL_GPL(bus_find_device_by_name);
 363
 364/**
 365 * subsys_find_device_by_id - find a device with a specific enumeration number
 366 * @subsys: subsystem
 367 * @id: index 'id' in struct device
 368 * @hint: device to check first
 369 *
 370 * Check the hint's next object and if it is a match return it directly,
 371 * otherwise, fall back to a full list search. Either way a reference for
 372 * the returned object is taken.
 373 */
 374struct device *subsys_find_device_by_id(struct bus_type *subsys, unsigned int id,
 375                                        struct device *hint)
 376{
 377        struct klist_iter i;
 378        struct device *dev;
 379
 380        if (!subsys)
 381                return NULL;
 382
 383        if (hint) {
 384                klist_iter_init_node(&subsys->p->klist_devices, &i, &hint->p->knode_bus);
 385                dev = next_device(&i);
 386                if (dev && dev->id == id && get_device(dev)) {
 387                        klist_iter_exit(&i);
 388                        return dev;
 389                }
 390                klist_iter_exit(&i);
 391        }
 392
 393        klist_iter_init_node(&subsys->p->klist_devices, &i, NULL);
 394        while ((dev = next_device(&i))) {
 395                if (dev->id == id && get_device(dev)) {
 396                        klist_iter_exit(&i);
 397                        return dev;
 398                }
 399        }
 400        klist_iter_exit(&i);
 401        return NULL;
 402}
 403EXPORT_SYMBOL_GPL(subsys_find_device_by_id);
 404
 405static struct device_driver *next_driver(struct klist_iter *i)
 406{
 407        struct klist_node *n = klist_next(i);
 408        struct driver_private *drv_priv;
 409
 410        if (n) {
 411                drv_priv = container_of(n, struct driver_private, knode_bus);
 412                return drv_priv->driver;
 413        }
 414        return NULL;
 415}
 416
 417/**
 418 * bus_for_each_drv - driver iterator
 419 * @bus: bus we're dealing with.
 420 * @start: driver to start iterating on.
 421 * @data: data to pass to the callback.
 422 * @fn: function to call for each driver.
 423 *
 424 * This is nearly identical to the device iterator above.
 425 * We iterate over each driver that belongs to @bus, and call
 426 * @fn for each. If @fn returns anything but 0, we break out
 427 * and return it. If @start is not NULL, we use it as the head
 428 * of the list.
 429 *
 430 * NOTE: we don't return the driver that returns a non-zero
 431 * value, nor do we leave the reference count incremented for that
 432 * driver. If the caller needs to know that info, it must set it
 433 * in the callback. It must also be sure to increment the refcount
 434 * so it doesn't disappear before returning to the caller.
 435 */
 436int bus_for_each_drv(struct bus_type *bus, struct device_driver *start,
 437                     void *data, int (*fn)(struct device_driver *, void *))
 438{
 439        struct klist_iter i;
 440        struct device_driver *drv;
 441        int error = 0;
 442
 443        if (!bus)
 444                return -EINVAL;
 445
 446        klist_iter_init_node(&bus->p->klist_drivers, &i,
 447                             start ? &start->p->knode_bus : NULL);
 448        while ((drv = next_driver(&i)) && !error)
 449                error = fn(drv, data);
 450        klist_iter_exit(&i);
 451        return error;
 452}
 453EXPORT_SYMBOL_GPL(bus_for_each_drv);
 454
 455static int device_add_attrs(struct bus_type *bus, struct device *dev)
 456{
 457        int error = 0;
 458        int i;
 459
 460        if (!bus->dev_attrs)
 461                return 0;
 462
 463        for (i = 0; attr_name(bus->dev_attrs[i]); i++) {
 464                error = device_create_file(dev, &bus->dev_attrs[i]);
 465                if (error) {
 466                        while (--i >= 0)
 467                                device_remove_file(dev, &bus->dev_attrs[i]);
 468                        break;
 469                }
 470        }
 471        return error;
 472}
 473
 474static void device_remove_attrs(struct bus_type *bus, struct device *dev)
 475{
 476        int i;
 477
 478        if (bus->dev_attrs) {
 479                for (i = 0; attr_name(bus->dev_attrs[i]); i++)
 480                        device_remove_file(dev, &bus->dev_attrs[i]);
 481        }
 482}
 483
 484/**
 485 * bus_add_device - add device to bus
 486 * @dev: device being added
 487 *
 488 * - Add device's bus attributes.
 489 * - Create links to device's bus.
 490 * - Add the device to its bus's list of devices.
 491 */
 492int bus_add_device(struct device *dev)
 493{
 494        struct bus_type *bus = bus_get(dev->bus);
 495        int error = 0;
 496
 497        if (bus) {
 498                pr_debug("bus: '%s': add device %s\n", bus->name, dev_name(dev));
 499                error = device_add_attrs(bus, dev);
 500                if (error)
 501                        goto out_put;
 502                error = sysfs_create_link(&bus->p->devices_kset->kobj,
 503                                                &dev->kobj, dev_name(dev));
 504                if (error)
 505                        goto out_id;
 506                error = sysfs_create_link(&dev->kobj,
 507                                &dev->bus->p->subsys.kobj, "subsystem");
 508                if (error)
 509                        goto out_subsys;
 510                klist_add_tail(&dev->p->knode_bus, &bus->p->klist_devices);
 511        }
 512        return 0;
 513
 514out_subsys:
 515        sysfs_remove_link(&bus->p->devices_kset->kobj, dev_name(dev));
 516out_id:
 517        device_remove_attrs(bus, dev);
 518out_put:
 519        bus_put(dev->bus);
 520        return error;
 521}
 522
 523/**
 524 * bus_probe_device - probe drivers for a new device
 525 * @dev: device to probe
 526 *
 527 * - Automatically probe for a driver if the bus allows it.
 528 */
 529void bus_probe_device(struct device *dev)
 530{
 531        struct bus_type *bus = dev->bus;
 532        struct subsys_interface *sif;
 533        int ret;
 534
 535        if (!bus)
 536                return;
 537
 538        if (bus->p->drivers_autoprobe) {
 539                ret = device_attach(dev);
 540                WARN_ON(ret < 0);
 541        }
 542
 543        mutex_lock(&bus->p->mutex);
 544        list_for_each_entry(sif, &bus->p->interfaces, node)
 545                if (sif->add_dev)
 546                        sif->add_dev(dev, sif);
 547        mutex_unlock(&bus->p->mutex);
 548}
 549
 550/**
 551 * bus_remove_device - remove device from bus
 552 * @dev: device to be removed
 553 *
 554 * - Remove device from all interfaces.
 555 * - Remove symlink from bus' directory.
 556 * - Delete device from bus's list.
 557 * - Detach from its driver.
 558 * - Drop reference taken in bus_add_device().
 559 */
 560void bus_remove_device(struct device *dev)
 561{
 562        struct bus_type *bus = dev->bus;
 563        struct subsys_interface *sif;
 564
 565        if (!bus)
 566                return;
 567
 568        mutex_lock(&bus->p->mutex);
 569        list_for_each_entry(sif, &bus->p->interfaces, node)
 570                if (sif->remove_dev)
 571                        sif->remove_dev(dev, sif);
 572        mutex_unlock(&bus->p->mutex);
 573
 574        sysfs_remove_link(&dev->kobj, "subsystem");
 575        sysfs_remove_link(&dev->bus->p->devices_kset->kobj,
 576                          dev_name(dev));
 577        device_remove_attrs(dev->bus, dev);
 578        if (klist_node_attached(&dev->p->knode_bus))
 579                klist_del(&dev->p->knode_bus);
 580
 581        pr_debug("bus: '%s': remove device %s\n",
 582                 dev->bus->name, dev_name(dev));
 583        device_release_driver(dev);
 584        bus_put(dev->bus);
 585}
 586
 587static int driver_add_attrs(struct bus_type *bus, struct device_driver *drv)
 588{
 589        int error = 0;
 590        int i;
 591
 592        if (bus->drv_attrs) {
 593                for (i = 0; attr_name(bus->drv_attrs[i]); i++) {
 594                        error = driver_create_file(drv, &bus->drv_attrs[i]);
 595                        if (error)
 596                                goto err;
 597                }
 598        }
 599done:
 600        return error;
 601err:
 602        while (--i >= 0)
 603                driver_remove_file(drv, &bus->drv_attrs[i]);
 604        goto done;
 605}
 606
 607static void driver_remove_attrs(struct bus_type *bus,
 608                                struct device_driver *drv)
 609{
 610        int i;
 611
 612        if (bus->drv_attrs) {
 613                for (i = 0; attr_name(bus->drv_attrs[i]); i++)
 614                        driver_remove_file(drv, &bus->drv_attrs[i]);
 615        }
 616}
 617
 618static int __must_check add_bind_files(struct device_driver *drv)
 619{
 620        int ret;
 621
 622        ret = driver_create_file(drv, &driver_attr_unbind);
 623        if (ret == 0) {
 624                ret = driver_create_file(drv, &driver_attr_bind);
 625                if (ret)
 626                        driver_remove_file(drv, &driver_attr_unbind);
 627        }
 628        return ret;
 629}
 630
 631static void remove_bind_files(struct device_driver *drv)
 632{
 633        driver_remove_file(drv, &driver_attr_bind);
 634        driver_remove_file(drv, &driver_attr_unbind);
 635}
 636
 637static BUS_ATTR(drivers_probe, S_IWUSR, NULL, store_drivers_probe);
 638static BUS_ATTR(drivers_autoprobe, S_IWUSR | S_IRUGO,
 639                show_drivers_autoprobe, store_drivers_autoprobe);
 640
 641static int add_probe_files(struct bus_type *bus)
 642{
 643        int retval;
 644
 645        retval = bus_create_file(bus, &bus_attr_drivers_probe);
 646        if (retval)
 647                goto out;
 648
 649        retval = bus_create_file(bus, &bus_attr_drivers_autoprobe);
 650        if (retval)
 651                bus_remove_file(bus, &bus_attr_drivers_probe);
 652out:
 653        return retval;
 654}
 655
 656static void remove_probe_files(struct bus_type *bus)
 657{
 658        bus_remove_file(bus, &bus_attr_drivers_autoprobe);
 659        bus_remove_file(bus, &bus_attr_drivers_probe);
 660}
 661
 662static ssize_t driver_uevent_store(struct device_driver *drv,
 663                                   const char *buf, size_t count)
 664{
 665        enum kobject_action action;
 666
 667        if (kobject_action_type(buf, count, &action) == 0)
 668                kobject_uevent(&drv->p->kobj, action);
 669        return count;
 670}
 671static DRIVER_ATTR(uevent, S_IWUSR, NULL, driver_uevent_store);
 672
 673/**
 674 * bus_add_driver - Add a driver to the bus.
 675 * @drv: driver.
 676 */
 677int bus_add_driver(struct device_driver *drv)
 678{
 679        struct bus_type *bus;
 680        struct driver_private *priv;
 681        int error = 0;
 682
 683        bus = bus_get(drv->bus);
 684        if (!bus)
 685                return -EINVAL;
 686
 687        pr_debug("bus: '%s': add driver %s\n", bus->name, drv->name);
 688
 689        priv = kzalloc(sizeof(*priv), GFP_KERNEL);
 690        if (!priv) {
 691                error = -ENOMEM;
 692                goto out_put_bus;
 693        }
 694        klist_init(&priv->klist_devices, NULL, NULL);
 695        priv->driver = drv;
 696        drv->p = priv;
 697        priv->kobj.kset = bus->p->drivers_kset;
 698        error = kobject_init_and_add(&priv->kobj, &driver_ktype, NULL,
 699                                     "%s", drv->name);
 700        if (error)
 701                goto out_unregister;
 702
 703        klist_add_tail(&priv->knode_bus, &bus->p->klist_drivers);
 704        if (drv->bus->p->drivers_autoprobe) {
 705                error = driver_attach(drv);
 706                if (error)
 707                        goto out_unregister;
 708        }
 709        module_add_driver(drv->owner, drv);
 710
 711        error = driver_create_file(drv, &driver_attr_uevent);
 712        if (error) {
 713                printk(KERN_ERR "%s: uevent attr (%s) failed\n",
 714                        __func__, drv->name);
 715        }
 716        error = driver_add_attrs(bus, drv);
 717        if (error) {
 718                /* How the hell do we get out of this pickle? Give up */
 719                printk(KERN_ERR "%s: driver_add_attrs(%s) failed\n",
 720                        __func__, drv->name);
 721        }
 722
 723        if (!drv->suppress_bind_attrs) {
 724                error = add_bind_files(drv);
 725                if (error) {
 726                        /* Ditto */
 727                        printk(KERN_ERR "%s: add_bind_files(%s) failed\n",
 728                                __func__, drv->name);
 729                }
 730        }
 731
 732        return 0;
 733
 734out_unregister:
 735        kobject_put(&priv->kobj);
 736        kfree(drv->p);
 737        drv->p = NULL;
 738out_put_bus:
 739        bus_put(bus);
 740        return error;
 741}
 742
 743/**
 744 * bus_remove_driver - delete driver from bus's knowledge.
 745 * @drv: driver.
 746 *
 747 * Detach the driver from the devices it controls, and remove
 748 * it from its bus's list of drivers. Finally, we drop the reference
 749 * to the bus we took in bus_add_driver().
 750 */
 751void bus_remove_driver(struct device_driver *drv)
 752{
 753        if (!drv->bus)
 754                return;
 755
 756        if (!drv->suppress_bind_attrs)
 757                remove_bind_files(drv);
 758        driver_remove_attrs(drv->bus, drv);
 759        driver_remove_file(drv, &driver_attr_uevent);
 760        klist_remove(&drv->p->knode_bus);
 761        pr_debug("bus: '%s': remove driver %s\n", drv->bus->name, drv->name);
 762        driver_detach(drv);
 763        module_remove_driver(drv);
 764        kobject_put(&drv->p->kobj);
 765        bus_put(drv->bus);
 766}
 767
 768/* Helper for bus_rescan_devices's iter */
 769static int __must_check bus_rescan_devices_helper(struct device *dev,
 770                                                  void *data)
 771{
 772        int ret = 0;
 773
 774        if (!dev->driver) {
 775                if (dev->parent)        /* Needed for USB */
 776                        device_lock(dev->parent);
 777                ret = device_attach(dev);
 778                if (dev->parent)
 779                        device_unlock(dev->parent);
 780        }
 781        return ret < 0 ? ret : 0;
 782}
 783
 784/**
 785 * bus_rescan_devices - rescan devices on the bus for possible drivers
 786 * @bus: the bus to scan.
 787 *
 788 * This function will look for devices on the bus with no driver
 789 * attached and rescan it against existing drivers to see if it matches
 790 * any by calling device_attach() for the unbound devices.
 791 */
 792int bus_rescan_devices(struct bus_type *bus)
 793{
 794        return bus_for_each_dev(bus, NULL, NULL, bus_rescan_devices_helper);
 795}
 796EXPORT_SYMBOL_GPL(bus_rescan_devices);
 797
 798/**
 799 * device_reprobe - remove driver for a device and probe for a new driver
 800 * @dev: the device to reprobe
 801 *
 802 * This function detaches the attached driver (if any) for the given
 803 * device and restarts the driver probing process.  It is intended
 804 * to use if probing criteria changed during a devices lifetime and
 805 * driver attachment should change accordingly.
 806 */
 807int device_reprobe(struct device *dev)
 808{
 809        if (dev->driver) {
 810                if (dev->parent)        /* Needed for USB */
 811                        device_lock(dev->parent);
 812                device_release_driver(dev);
 813                if (dev->parent)
 814                        device_unlock(dev->parent);
 815        }
 816        return bus_rescan_devices_helper(dev, NULL);
 817}
 818EXPORT_SYMBOL_GPL(device_reprobe);
 819
 820/**
 821 * find_bus - locate bus by name.
 822 * @name: name of bus.
 823 *
 824 * Call kset_find_obj() to iterate over list of buses to
 825 * find a bus by name. Return bus if found.
 826 *
 827 * Note that kset_find_obj increments bus' reference count.
 828 */
 829#if 0
 830struct bus_type *find_bus(char *name)
 831{
 832        struct kobject *k = kset_find_obj(bus_kset, name);
 833        return k ? to_bus(k) : NULL;
 834}
 835#endif  /*  0  */
 836
 837
 838/**
 839 * bus_add_attrs - Add default attributes for this bus.
 840 * @bus: Bus that has just been registered.
 841 */
 842
 843static int bus_add_attrs(struct bus_type *bus)
 844{
 845        int error = 0;
 846        int i;
 847
 848        if (bus->bus_attrs) {
 849                for (i = 0; attr_name(bus->bus_attrs[i]); i++) {
 850                        error = bus_create_file(bus, &bus->bus_attrs[i]);
 851                        if (error)
 852                                goto err;
 853                }
 854        }
 855done:
 856        return error;
 857err:
 858        while (--i >= 0)
 859                bus_remove_file(bus, &bus->bus_attrs[i]);
 860        goto done;
 861}
 862
 863static void bus_remove_attrs(struct bus_type *bus)
 864{
 865        int i;
 866
 867        if (bus->bus_attrs) {
 868                for (i = 0; attr_name(bus->bus_attrs[i]); i++)
 869                        bus_remove_file(bus, &bus->bus_attrs[i]);
 870        }
 871}
 872
 873static void klist_devices_get(struct klist_node *n)
 874{
 875        struct device_private *dev_prv = to_device_private_bus(n);
 876        struct device *dev = dev_prv->device;
 877
 878        get_device(dev);
 879}
 880
 881static void klist_devices_put(struct klist_node *n)
 882{
 883        struct device_private *dev_prv = to_device_private_bus(n);
 884        struct device *dev = dev_prv->device;
 885
 886        put_device(dev);
 887}
 888
 889static ssize_t bus_uevent_store(struct bus_type *bus,
 890                                const char *buf, size_t count)
 891{
 892        enum kobject_action action;
 893
 894        if (kobject_action_type(buf, count, &action) == 0)
 895                kobject_uevent(&bus->p->subsys.kobj, action);
 896        return count;
 897}
 898static BUS_ATTR(uevent, S_IWUSR, NULL, bus_uevent_store);
 899
 900/**
 901 * bus_register - register a driver-core subsystem
 902 * @bus: bus to register
 903 *
 904 * Once we have that, we register the bus with the kobject
 905 * infrastructure, then register the children subsystems it has:
 906 * the devices and drivers that belong to the subsystem.
 907 */
 908int bus_register(struct bus_type *bus)
 909{
 910        int retval;
 911        struct subsys_private *priv;
 912        struct lock_class_key *key = &bus->lock_key;
 913
 914        priv = kzalloc(sizeof(struct subsys_private), GFP_KERNEL);
 915        if (!priv)
 916                return -ENOMEM;
 917
 918        priv->bus = bus;
 919        bus->p = priv;
 920
 921        BLOCKING_INIT_NOTIFIER_HEAD(&priv->bus_notifier);
 922
 923        retval = kobject_set_name(&priv->subsys.kobj, "%s", bus->name);
 924        if (retval)
 925                goto out;
 926
 927        priv->subsys.kobj.kset = bus_kset;
 928        priv->subsys.kobj.ktype = &bus_ktype;
 929        priv->drivers_autoprobe = 1;
 930
 931        retval = kset_register(&priv->subsys);
 932        if (retval)
 933                goto out;
 934
 935        retval = bus_create_file(bus, &bus_attr_uevent);
 936        if (retval)
 937                goto bus_uevent_fail;
 938
 939        priv->devices_kset = kset_create_and_add("devices", NULL,
 940                                                 &priv->subsys.kobj);
 941        if (!priv->devices_kset) {
 942                retval = -ENOMEM;
 943                goto bus_devices_fail;
 944        }
 945
 946        priv->drivers_kset = kset_create_and_add("drivers", NULL,
 947                                                 &priv->subsys.kobj);
 948        if (!priv->drivers_kset) {
 949                retval = -ENOMEM;
 950                goto bus_drivers_fail;
 951        }
 952
 953        INIT_LIST_HEAD(&priv->interfaces);
 954        __mutex_init(&priv->mutex, "subsys mutex", key);
 955        klist_init(&priv->klist_devices, klist_devices_get, klist_devices_put);
 956        klist_init(&priv->klist_drivers, NULL, NULL);
 957
 958        retval = add_probe_files(bus);
 959        if (retval)
 960                goto bus_probe_files_fail;
 961
 962        retval = bus_add_attrs(bus);
 963        if (retval)
 964                goto bus_attrs_fail;
 965
 966        pr_debug("bus: '%s': registered\n", bus->name);
 967        return 0;
 968
 969bus_attrs_fail:
 970        remove_probe_files(bus);
 971bus_probe_files_fail:
 972        kset_unregister(bus->p->drivers_kset);
 973bus_drivers_fail:
 974        kset_unregister(bus->p->devices_kset);
 975bus_devices_fail:
 976        bus_remove_file(bus, &bus_attr_uevent);
 977bus_uevent_fail:
 978        kset_unregister(&bus->p->subsys);
 979out:
 980        kfree(bus->p);
 981        bus->p = NULL;
 982        return retval;
 983}
 984EXPORT_SYMBOL_GPL(bus_register);
 985
 986/**
 987 * bus_unregister - remove a bus from the system
 988 * @bus: bus.
 989 *
 990 * Unregister the child subsystems and the bus itself.
 991 * Finally, we call bus_put() to release the refcount
 992 */
 993void bus_unregister(struct bus_type *bus)
 994{
 995        pr_debug("bus: '%s': unregistering\n", bus->name);
 996        if (bus->dev_root)
 997                device_unregister(bus->dev_root);
 998        bus_remove_attrs(bus);
 999        remove_probe_files(bus);
1000        kset_unregister(bus->p->drivers_kset);
1001        kset_unregister(bus->p->devices_kset);
1002        bus_remove_file(bus, &bus_attr_uevent);
1003        kset_unregister(&bus->p->subsys);
1004        kfree(bus->p);
1005        bus->p = NULL;
1006}
1007EXPORT_SYMBOL_GPL(bus_unregister);
1008
1009int bus_register_notifier(struct bus_type *bus, struct notifier_block *nb)
1010{
1011        return blocking_notifier_chain_register(&bus->p->bus_notifier, nb);
1012}
1013EXPORT_SYMBOL_GPL(bus_register_notifier);
1014
1015int bus_unregister_notifier(struct bus_type *bus, struct notifier_block *nb)
1016{
1017        return blocking_notifier_chain_unregister(&bus->p->bus_notifier, nb);
1018}
1019EXPORT_SYMBOL_GPL(bus_unregister_notifier);
1020
1021struct kset *bus_get_kset(struct bus_type *bus)
1022{
1023        return &bus->p->subsys;
1024}
1025EXPORT_SYMBOL_GPL(bus_get_kset);
1026
1027struct klist *bus_get_device_klist(struct bus_type *bus)
1028{
1029        return &bus->p->klist_devices;
1030}
1031EXPORT_SYMBOL_GPL(bus_get_device_klist);
1032
1033/*
1034 * Yes, this forcibly breaks the klist abstraction temporarily.  It
1035 * just wants to sort the klist, not change reference counts and
1036 * take/drop locks rapidly in the process.  It does all this while
1037 * holding the lock for the list, so objects can't otherwise be
1038 * added/removed while we're swizzling.
1039 */
1040static void device_insertion_sort_klist(struct device *a, struct list_head *list,
1041                                        int (*compare)(const struct device *a,
1042                                                        const struct device *b))
1043{
1044        struct list_head *pos;
1045        struct klist_node *n;
1046        struct device_private *dev_prv;
1047        struct device *b;
1048
1049        list_for_each(pos, list) {
1050                n = container_of(pos, struct klist_node, n_node);
1051                dev_prv = to_device_private_bus(n);
1052                b = dev_prv->device;
1053                if (compare(a, b) <= 0) {
1054                        list_move_tail(&a->p->knode_bus.n_node,
1055                                       &b->p->knode_bus.n_node);
1056                        return;
1057                }
1058        }
1059        list_move_tail(&a->p->knode_bus.n_node, list);
1060}
1061
1062void bus_sort_breadthfirst(struct bus_type *bus,
1063                           int (*compare)(const struct device *a,
1064                                          const struct device *b))
1065{
1066        LIST_HEAD(sorted_devices);
1067        struct list_head *pos, *tmp;
1068        struct klist_node *n;
1069        struct device_private *dev_prv;
1070        struct device *dev;
1071        struct klist *device_klist;
1072
1073        device_klist = bus_get_device_klist(bus);
1074
1075        spin_lock(&device_klist->k_lock);
1076        list_for_each_safe(pos, tmp, &device_klist->k_list) {
1077                n = container_of(pos, struct klist_node, n_node);
1078                dev_prv = to_device_private_bus(n);
1079                dev = dev_prv->device;
1080                device_insertion_sort_klist(dev, &sorted_devices, compare);
1081        }
1082        list_splice(&sorted_devices, &device_klist->k_list);
1083        spin_unlock(&device_klist->k_lock);
1084}
1085EXPORT_SYMBOL_GPL(bus_sort_breadthfirst);
1086
1087/**
1088 * subsys_dev_iter_init - initialize subsys device iterator
1089 * @iter: subsys iterator to initialize
1090 * @subsys: the subsys we wanna iterate over
1091 * @start: the device to start iterating from, if any
1092 * @type: device_type of the devices to iterate over, NULL for all
1093 *
1094 * Initialize subsys iterator @iter such that it iterates over devices
1095 * of @subsys.  If @start is set, the list iteration will start there,
1096 * otherwise if it is NULL, the iteration starts at the beginning of
1097 * the list.
1098 */
1099void subsys_dev_iter_init(struct subsys_dev_iter *iter, struct bus_type *subsys,
1100                          struct device *start, const struct device_type *type)
1101{
1102        struct klist_node *start_knode = NULL;
1103
1104        if (start)
1105                start_knode = &start->p->knode_bus;
1106        klist_iter_init_node(&subsys->p->klist_devices, &iter->ki, start_knode);
1107        iter->type = type;
1108}
1109EXPORT_SYMBOL_GPL(subsys_dev_iter_init);
1110
1111/**
1112 * subsys_dev_iter_next - iterate to the next device
1113 * @iter: subsys iterator to proceed
1114 *
1115 * Proceed @iter to the next device and return it.  Returns NULL if
1116 * iteration is complete.
1117 *
1118 * The returned device is referenced and won't be released till
1119 * iterator is proceed to the next device or exited.  The caller is
1120 * free to do whatever it wants to do with the device including
1121 * calling back into subsys code.
1122 */
1123struct device *subsys_dev_iter_next(struct subsys_dev_iter *iter)
1124{
1125        struct klist_node *knode;
1126        struct device *dev;
1127
1128        for (;;) {
1129                knode = klist_next(&iter->ki);
1130                if (!knode)
1131                        return NULL;
1132                dev = container_of(knode, struct device_private, knode_bus)->device;
1133                if (!iter->type || iter->type == dev->type)
1134                        return dev;
1135        }
1136}
1137EXPORT_SYMBOL_GPL(subsys_dev_iter_next);
1138
1139/**
1140 * subsys_dev_iter_exit - finish iteration
1141 * @iter: subsys iterator to finish
1142 *
1143 * Finish an iteration.  Always call this function after iteration is
1144 * complete whether the iteration ran till the end or not.
1145 */
1146void subsys_dev_iter_exit(struct subsys_dev_iter *iter)
1147{
1148        klist_iter_exit(&iter->ki);
1149}
1150EXPORT_SYMBOL_GPL(subsys_dev_iter_exit);
1151
1152int subsys_interface_register(struct subsys_interface *sif)
1153{
1154        struct bus_type *subsys;
1155        struct subsys_dev_iter iter;
1156        struct device *dev;
1157
1158        if (!sif || !sif->subsys)
1159                return -ENODEV;
1160
1161        subsys = bus_get(sif->subsys);
1162        if (!subsys)
1163                return -EINVAL;
1164
1165        mutex_lock(&subsys->p->mutex);
1166        list_add_tail(&sif->node, &subsys->p->interfaces);
1167        if (sif->add_dev) {
1168                subsys_dev_iter_init(&iter, subsys, NULL, NULL);
1169                while ((dev = subsys_dev_iter_next(&iter)))
1170                        sif->add_dev(dev, sif);
1171                subsys_dev_iter_exit(&iter);
1172        }
1173        mutex_unlock(&subsys->p->mutex);
1174
1175        return 0;
1176}
1177EXPORT_SYMBOL_GPL(subsys_interface_register);
1178
1179void subsys_interface_unregister(struct subsys_interface *sif)
1180{
1181        struct bus_type *subsys;
1182        struct subsys_dev_iter iter;
1183        struct device *dev;
1184
1185        if (!sif || !sif->subsys)
1186                return;
1187
1188        subsys = sif->subsys;
1189
1190        mutex_lock(&subsys->p->mutex);
1191        list_del_init(&sif->node);
1192        if (sif->remove_dev) {
1193                subsys_dev_iter_init(&iter, subsys, NULL, NULL);
1194                while ((dev = subsys_dev_iter_next(&iter)))
1195                        sif->remove_dev(dev, sif);
1196                subsys_dev_iter_exit(&iter);
1197        }
1198        mutex_unlock(&subsys->p->mutex);
1199
1200        bus_put(subsys);
1201}
1202EXPORT_SYMBOL_GPL(subsys_interface_unregister);
1203
1204static void system_root_device_release(struct device *dev)
1205{
1206        kfree(dev);
1207}
1208
1209static int subsys_register(struct bus_type *subsys,
1210                           const struct attribute_group **groups,
1211                           struct kobject *parent_of_root)
1212{
1213        struct device *dev;
1214        int err;
1215
1216        err = bus_register(subsys);
1217        if (err < 0)
1218                return err;
1219
1220        dev = kzalloc(sizeof(struct device), GFP_KERNEL);
1221        if (!dev) {
1222                err = -ENOMEM;
1223                goto err_dev;
1224        }
1225
1226        err = dev_set_name(dev, "%s", subsys->name);
1227        if (err < 0)
1228                goto err_name;
1229
1230        dev->kobj.parent = parent_of_root;
1231        dev->groups = groups;
1232        dev->release = system_root_device_release;
1233
1234        err = device_register(dev);
1235        if (err < 0)
1236                goto err_dev_reg;
1237
1238        subsys->dev_root = dev;
1239        return 0;
1240
1241err_dev_reg:
1242        put_device(dev);
1243        dev = NULL;
1244err_name:
1245        kfree(dev);
1246err_dev:
1247        bus_unregister(subsys);
1248        return err;
1249}
1250
1251/**
1252 * subsys_system_register - register a subsystem at /sys/devices/system/
1253 * @subsys: system subsystem
1254 * @groups: default attributes for the root device
1255 *
1256 * All 'system' subsystems have a /sys/devices/system/<name> root device
1257 * with the name of the subsystem. The root device can carry subsystem-
1258 * wide attributes. All registered devices are below this single root
1259 * device and are named after the subsystem with a simple enumeration
1260 * number appended. The registered devices are not explicitely named;
1261 * only 'id' in the device needs to be set.
1262 *
1263 * Do not use this interface for anything new, it exists for compatibility
1264 * with bad ideas only. New subsystems should use plain subsystems; and
1265 * add the subsystem-wide attributes should be added to the subsystem
1266 * directory itself and not some create fake root-device placed in
1267 * /sys/devices/system/<name>.
1268 */
1269int subsys_system_register(struct bus_type *subsys,
1270                           const struct attribute_group **groups)
1271{
1272        return subsys_register(subsys, groups, &system_kset->kobj);
1273}
1274EXPORT_SYMBOL_GPL(subsys_system_register);
1275
1276/**
1277 * subsys_virtual_register - register a subsystem at /sys/devices/virtual/
1278 * @subsys: virtual subsystem
1279 * @groups: default attributes for the root device
1280 *
1281 * All 'virtual' subsystems have a /sys/devices/system/<name> root device
1282 * with the name of the subystem.  The root device can carry subsystem-wide
1283 * attributes.  All registered devices are below this single root device.
1284 * There's no restriction on device naming.  This is for kernel software
1285 * constructs which need sysfs interface.
1286 */
1287int subsys_virtual_register(struct bus_type *subsys,
1288                            const struct attribute_group **groups)
1289{
1290        struct kobject *virtual_dir;
1291
1292        virtual_dir = virtual_device_parent(NULL);
1293        if (!virtual_dir)
1294                return -ENOMEM;
1295
1296        return subsys_register(subsys, groups, virtual_dir);
1297}
1298EXPORT_SYMBOL_GPL(subsys_virtual_register);
1299
1300int __init buses_init(void)
1301{
1302        bus_kset = kset_create_and_add("bus", &bus_uevent_ops, NULL);
1303        if (!bus_kset)
1304                return -ENOMEM;
1305
1306        system_kset = kset_create_and_add("system", NULL, &devices_kset->kobj);
1307        if (!system_kset)
1308                return -ENOMEM;
1309
1310        return 0;
1311}
1312
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