drivers/base/bus.c

   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/init.h>
  17 #include <linux/string.h>
  18 #include "base.h"
  19 #include "power/power.h"
  20
  21 #define to_bus_attr(_attr) container_of(_attr, struct bus_attribute, attr)
  22 #define to_bus(obj) container_of(obj, struct bus_type_private, subsys.kobj)
  23
  24 /*
  25  * sysfs bindings for drivers
  26  */
  27
  28 #define to_drv_attr(_attr) container_of(_attr, struct driver_attribute, attr)
  29
  30
  31 static int __must_check bus_rescan_devices_helper(struct device *dev,
  32                                                 void *data);
  33
  34 static struct bus_type *bus_get(struct bus_type *bus)
  35 {
  36         if (bus) {
  37                 kset_get(&bus->p->subsys);
  38                 return bus;
  39         }
  40         return NULL;
  41 }
  42
  43 static void bus_put(struct bus_type *bus)
  44 {
  45         if (bus)
  46                 kset_put(&bus->p->subsys);
  47 }
  48
  49 static ssize_t drv_attr_show(struct kobject *kobj, struct attribute *attr,
  50                              char *buf)
  51 {
  52         struct driver_attribute *drv_attr = to_drv_attr(attr);
  53         struct driver_private *drv_priv = to_driver(kobj);
  54         ssize_t ret = -EIO;
  55
  56         if (drv_attr->show)
  57                 ret = drv_attr->show(drv_priv->driver, buf);
  58         return ret;
  59 }
  60
  61 static ssize_t drv_attr_store(struct kobject *kobj, struct attribute *attr,
  62                               const char *buf, size_t count)
  63 {
  64         struct driver_attribute *drv_attr = to_drv_attr(attr);
  65         struct driver_private *drv_priv = to_driver(kobj);
  66         ssize_t ret = -EIO;
  67
  68         if (drv_attr->store)
  69                 ret = drv_attr->store(drv_priv->driver, buf, count);
  70         return ret;
  71 }
  72
  73 static struct sysfs_ops driver_sysfs_ops = {
  74         .show   = drv_attr_show,
  75         .store  = drv_attr_store,
  76 };
  77
  78 static void driver_release(struct kobject *kobj)
  79 {
  80         struct driver_private *drv_priv = to_driver(kobj);
  81
  82         pr_debug("driver: '%s': %s\n", kobject_name(kobj), __func__);
  83         kfree(drv_priv);
  84 }
  85
  86 static struct kobj_type driver_ktype = {
  87         .sysfs_ops      = &driver_sysfs_ops,
  88         .release        = driver_release,
  89 };
  90
  91 /*
  92  * sysfs bindings for buses
  93  */
  94 static ssize_t bus_attr_show(struct kobject *kobj, struct attribute *attr,
  95                              char *buf)
  96 {
  97         struct bus_attribute *bus_attr = to_bus_attr(attr);
  98         struct bus_type_private *bus_priv = to_bus(kobj);
  99         ssize_t ret = 0;
 100
 101         if (bus_attr->show)
 102                 ret = bus_attr->show(bus_priv->bus, buf);
 103         return ret;
 104 }
 105
 106 static ssize_t bus_attr_store(struct kobject *kobj, struct attribute *attr,
 107                               const char *buf, size_t count)
 108 {
 109         struct bus_attribute *bus_attr = to_bus_attr(attr);
 110         struct bus_type_private *bus_priv = to_bus(kobj);
 111         ssize_t ret = 0;
 112
 113         if (bus_attr->store)
 114                 ret = bus_attr->store(bus_priv->bus, buf, count);
 115         return ret;
 116 }
 117
 118 static struct sysfs_ops bus_sysfs_ops = {
 119         .show   = bus_attr_show,
 120         .store  = bus_attr_store,
 121 };
 122
 123 int bus_create_file(struct bus_type *bus, struct bus_attribute *attr)
 124 {
 125         int error;
 126         if (bus_get(bus)) {
 127                 error = sysfs_create_file(&bus->p->subsys.kobj, &attr->attr);
 128                 bus_put(bus);
 129         } else
 130                 error = -EINVAL;
 131         return error;
 132 }
 133 EXPORT_SYMBOL_GPL(bus_create_file);
 134
 135 void bus_remove_file(struct bus_type *bus, struct bus_attribute *attr)
 136 {
 137         if (bus_get(bus)) {
 138                 sysfs_remove_file(&bus->p->subsys.kobj, &attr->attr);
 139                 bus_put(bus);
 140         }
 141 }
 142 EXPORT_SYMBOL_GPL(bus_remove_file);
 143
 144 static struct kobj_type bus_ktype = {
 145         .sysfs_ops      = &bus_sysfs_ops,
 146 };
 147
 148 static int bus_uevent_filter(struct kset *kset, struct kobject *kobj)
 149 {
 150         struct kobj_type *ktype = get_ktype(kobj);
 151
 152         if (ktype == &bus_ktype)
 153                 return 1;
 154         return 0;
 155 }
 156
 157 static struct kset_uevent_ops bus_uevent_ops = {
 158         .filter = bus_uevent_filter,
 159 };
 160
 161 static struct kset *bus_kset;
 162
 163
 164 #ifdef CONFIG_HOTPLUG
 165 /* Manually detach a device from its associated driver. */
 166 static ssize_t driver_unbind(struct device_driver *drv,
 167                              const char *buf, size_t count)
 168 {
 169         struct bus_type *bus = bus_get(drv->bus);
 170         struct device *dev;
 171         int err = -ENODEV;
 172
 173         dev = bus_find_device_by_name(bus, NULL, buf);
 174         if (dev && dev->driver == drv) {
 175                 if (dev->parent)        /* Needed for USB */
 176                         down(&dev->parent->sem);
 177                 device_release_driver(dev);
 178                 if (dev->parent)
 179                         up(&dev->parent->sem);
 180                 err = count;
 181         }
 182         put_device(dev);
 183         bus_put(bus);
 184         return err;
 185 }
 186 static DRIVER_ATTR(unbind, S_IWUSR, NULL, driver_unbind);
 187
 188 /*
 189  * Manually attach a device to a driver.
 190  * Note: the driver must want to bind to the device,
 191  * it is not possible to override the driver's id table.
 192  */
 193 static ssize_t driver_bind(struct device_driver *drv,
 194                            const char *buf, size_t count)
 195 {
 196         struct bus_type *bus = bus_get(drv->bus);
 197         struct device *dev;
 198         int err = -ENODEV;
 199
 200         dev = bus_find_device_by_name(bus, NULL, buf);
 201         if (dev && dev->driver == NULL) {
 202                 if (dev->parent)        /* Needed for USB */
 203                         down(&dev->parent->sem);
 204                 down(&dev->sem);
 205                 err = driver_probe_device(drv, dev);
 206                 up(&dev->sem);
 207                 if (dev->parent)
 208                         up(&dev->parent->sem);
 209
 210                 if (err > 0) {
 211                         /* success */
 212                         err = count;
 213                 } else if (err == 0) {
 214                         /* driver didn't accept device */
 215                         err = -ENODEV;
 216                 }
 217         }
 218         put_device(dev);
 219         bus_put(bus);
 220         return err;
 221 }
 222 static DRIVER_ATTR(bind, S_IWUSR, NULL, driver_bind);
 223
 224 static ssize_t show_drivers_autoprobe(struct bus_type *bus, char *buf)
 225 {
 226         return sprintf(buf, "%d\n", bus->p->drivers_autoprobe);
 227 }
 228
 229 static ssize_t store_drivers_autoprobe(struct bus_type *bus,
 230                                        const char *buf, size_t count)
 231 {
 232         if (buf[0] == '0')
 233                 bus->p->drivers_autoprobe = 0;
 234         else
 235                 bus->p->drivers_autoprobe = 1;
 236         return count;
 237 }
 238
 239 static ssize_t store_drivers_probe(struct bus_type *bus,
 240                                    const char *buf, size_t count)
 241 {
 242         struct device *dev;
 243
 244         dev = bus_find_device_by_name(bus, NULL, buf);
 245         if (!dev)
 246                 return -ENODEV;
 247         if (bus_rescan_devices_helper(dev, NULL) != 0)
 248                 return -EINVAL;
 249         return count;
 250 }
 251 #endif
 252
 253 static struct device *next_device(struct klist_iter *i)
 254 {
 255         struct klist_node *n = klist_next(i);
 256         return n ? container_of(n, struct device, knode_bus) : NULL;
 257 }
 258
 259 /**
 260  * bus_for_each_dev - device iterator.
 261  * @bus: bus type.
 262  * @start: device to start iterating from.
 263  * @data: data for the callback.
 264  * @fn: function to be called for each device.
 265  *
 266  * Iterate over @bus's list of devices, and call @fn for each,
 267  * passing it @data. If @start is not NULL, we use that device to
 268  * begin iterating from.
 269  *
 270  * We check the return of @fn each time. If it returns anything
 271  * other than 0, we break out and return that value.
 272  *
 273  * NOTE: The device that returns a non-zero value is not retained
 274  * in any way, nor is its refcount incremented. If the caller needs
 275  * to retain this data, it should do, and increment the reference
 276  * count in the supplied callback.
 277  */
 278 int bus_for_each_dev(struct bus_type *bus, struct device *start,
 279                      void *data, int (*fn)(struct device *, void *))
 280 {
 281         struct klist_iter i;
 282         struct device *dev;
 283         int error = 0;
 284
 285         if (!bus)
 286                 return -EINVAL;
 287
 288         klist_iter_init_node(&bus->p->klist_devices, &i,
 289                              (start ? &start->knode_bus : NULL));
 290         while ((dev = next_device(&i)) && !error)
 291                 error = fn(dev, data);
 292         klist_iter_exit(&i);
 293         return error;
 294 }
 295 EXPORT_SYMBOL_GPL(bus_for_each_dev);
 296
 297 /**
 298  * bus_find_device - device iterator for locating a particular device.
 299  * @bus: bus type
 300  * @start: Device to begin with
 301  * @data: Data to pass to match function
 302  * @match: Callback function to check device
 303  *
 304  * This is similar to the bus_for_each_dev() function above, but it
 305  * returns a reference to a device that is 'found' for later use, as
 306  * determined by the @match callback.
 307  *
 308  * The callback should return 0 if the device doesn't match and non-zero
 309  * if it does.  If the callback returns non-zero, this function will
 310  * return to the caller and not iterate over any more devices.
 311  */
 312 struct device *bus_find_device(struct bus_type *bus,
 313                                struct device *start, void *data,
 314                                int (*match)(struct device *dev, void *data))
 315 {
 316         struct klist_iter i;
 317         struct device *dev;
 318
 319         if (!bus)
 320                 return NULL;
 321
 322         klist_iter_init_node(&bus->p->klist_devices, &i,
 323                              (start ? &start->knode_bus : NULL));
 324         while ((dev = next_device(&i)))
 325                 if (match(dev, data) && get_device(dev))
 326                         break;
 327         klist_iter_exit(&i);
 328         return dev;
 329 }
 330 EXPORT_SYMBOL_GPL(bus_find_device);
 331
 332 static int match_name(struct device *dev, void *data)
 333 {
 334         const char *name = data;
 335
 336         if (strcmp(name, dev->bus_id) == 0)
 337                 return 1;
 338         return 0;
 339 }
 340
 341 /**
 342  * bus_find_device_by_name - device iterator for locating a particular device of a specific name
 343  * @bus: bus type
 344  * @start: Device to begin with
 345  * @name: name of the device to match
 346  *
 347  * This is similar to the bus_find_device() function above, but it handles
 348  * searching by a name automatically, no need to write another strcmp matching
 349  * function.
 350  */
 351 struct device *bus_find_device_by_name(struct bus_type *bus,
 352                                        struct device *start, const char *name)
 353 {
 354         return bus_find_device(bus, start, (void *)name, match_name);
 355 }
 356 EXPORT_SYMBOL_GPL(bus_find_device_by_name);
 357
 358 static struct device_driver *next_driver(struct klist_iter *i)
 359 {
 360         struct klist_node *n = klist_next(i);
 361         struct driver_private *drv_priv;
 362
 363         if (n) {
 364                 drv_priv = container_of(n, struct driver_private, knode_bus);
 365                 return drv_priv->driver;
 366         }
 367         return NULL;
 368 }
 369
 370 /**
 371  * bus_for_each_drv - driver iterator
 372  * @bus: bus we're dealing with.
 373  * @start: driver to start iterating on.
 374  * @data: data to pass to the callback.
 375  * @fn: function to call for each driver.
 376  *
 377  * This is nearly identical to the device iterator above.
 378  * We iterate over each driver that belongs to @bus, and call
 379  * @fn for each. If @fn returns anything but 0, we break out
 380  * and return it. If @start is not NULL, we use it as the head
 381  * of the list.
 382  *
 383  * NOTE: we don't return the driver that returns a non-zero
 384  * value, nor do we leave the reference count incremented for that
 385  * driver. If the caller needs to know that info, it must set it
 386  * in the callback. It must also be sure to increment the refcount
 387  * so it doesn't disappear before returning to the caller.
 388  */
 389 int bus_for_each_drv(struct bus_type *bus, struct device_driver *start,
 390                      void *data, int (*fn)(struct device_driver *, void *))
 391 {
 392         struct klist_iter i;
 393         struct device_driver *drv;
 394         int error = 0;
 395
 396         if (!bus)
 397                 return -EINVAL;
 398
 399         klist_iter_init_node(&bus->p->klist_drivers, &i,
 400                              start ? &start->p->knode_bus : NULL);
 401         while ((drv = next_driver(&i)) && !error)
 402                 error = fn(drv, data);
 403         klist_iter_exit(&i);
 404         return error;
 405 }
 406 EXPORT_SYMBOL_GPL(bus_for_each_drv);
 407
 408 static int device_add_attrs(struct bus_type *bus, struct device *dev)
 409 {
 410         int error = 0;
 411         int i;
 412
 413         if (!bus->dev_attrs)
 414                 return 0;
 415
 416         for (i = 0; attr_name(bus->dev_attrs[i]); i++) {
 417                 error = device_create_file(dev, &bus->dev_attrs[i]);
 418                 if (error) {
 419                         while (--i >= 0)
 420                                 device_remove_file(dev, &bus->dev_attrs[i]);
 421                         break;
 422                 }
 423         }
 424         return error;
 425 }
 426
 427 static void device_remove_attrs(struct bus_type *bus, struct device *dev)
 428 {
 429         int i;
 430
 431         if (bus->dev_attrs) {
 432                 for (i = 0; attr_name(bus->dev_attrs[i]); i++)
 433                         device_remove_file(dev, &bus->dev_attrs[i]);
 434         }
 435 }
 436
 437 #ifdef CONFIG_SYSFS_DEPRECATED
 438 static int make_deprecated_bus_links(struct device *dev)
 439 {
 440         return sysfs_create_link(&dev->kobj,
 441                                  &dev->bus->p->subsys.kobj, "bus");
 442 }
 443
 444 static void remove_deprecated_bus_links(struct device *dev)
 445 {
 446         sysfs_remove_link(&dev->kobj, "bus");
 447 }
 448 #else
 449 static inline int make_deprecated_bus_links(struct device *dev) { return 0; }
 450 static inline void remove_deprecated_bus_links(struct device *dev) { }
 451 #endif
 452
 453 /**
 454  * bus_add_device - add device to bus
 455  * @dev: device being added
 456  *
 457  * - Add the device to its bus's list of devices.
 458  * - Create link to device's bus.
 459  */
 460 int bus_add_device(struct device *dev)
 461 {
 462         struct bus_type *bus = bus_get(dev->bus);
 463         int error = 0;
 464
 465         if (bus) {
 466                 pr_debug("bus: '%s': add device %s\n", bus->name, dev->bus_id);
 467                 error = device_add_attrs(bus, dev);
 468                 if (error)
 469                         goto out_put;
 470                 error = sysfs_create_link(&bus->p->devices_kset->kobj,
 471                                                 &dev->kobj, dev->bus_id);
 472                 if (error)
 473                         goto out_id;
 474                 error = sysfs_create_link(&dev->kobj,
 475                                 &dev->bus->p->subsys.kobj, "subsystem");
 476                 if (error)
 477                         goto out_subsys;
 478                 error = make_deprecated_bus_links(dev);
 479                 if (error)
 480                         goto out_deprecated;
 481         }
 482         return 0;
 483
 484 out_deprecated:
 485         sysfs_remove_link(&dev->kobj, "subsystem");
 486 out_subsys:
 487         sysfs_remove_link(&bus->p->devices_kset->kobj, dev->bus_id);
 488 out_id:
 489         device_remove_attrs(bus, dev);
 490 out_put:
 491         bus_put(dev->bus);
 492         return error;
 493 }
 494
 495 /**
 496  * bus_attach_device - add device to bus
 497  * @dev: device tried to attach to a driver
 498  *
 499  * - Add device to bus's list of devices.
 500  * - Try to attach to driver.
 501  */
 502 void bus_attach_device(struct device *dev)
 503 {
 504         struct bus_type *bus = dev->bus;
 505         int ret = 0;
 506
 507         if (bus) {
 508                 if (bus->p->drivers_autoprobe)
 509                         ret = device_attach(dev);
 510                 WARN_ON(ret < 0);
 511                 if (ret >= 0)
 512                         klist_add_tail(&dev->knode_bus, &bus->p->klist_devices);
 513         }
 514 }
 515
 516 /**
 517  * bus_remove_device - remove device from bus
 518  * @dev: device to be removed
 519  *
 520  * - Remove symlink from bus's directory.
 521  * - Delete device from bus's list.
 522  * - Detach from its driver.
 523  * - Drop reference taken in bus_add_device().
 524  */
 525 void bus_remove_device(struct device *dev)
 526 {
 527         if (dev->bus) {
 528                 sysfs_remove_link(&dev->kobj, "subsystem");
 529                 remove_deprecated_bus_links(dev);
 530                 sysfs_remove_link(&dev->bus->p->devices_kset->kobj,
 531                                   dev->bus_id);
 532                 device_remove_attrs(dev->bus, dev);
 533                 if (klist_node_attached(&dev->knode_bus))
 534                         klist_del(&dev->knode_bus);
 535
 536                 pr_debug("bus: '%s': remove device %s\n",
 537                          dev->bus->name, dev->bus_id);
 538                 device_release_driver(dev);
 539                 bus_put(dev->bus);
 540         }
 541 }
 542
 543 static int driver_add_attrs(struct bus_type *bus, struct device_driver *drv)
 544 {
 545         int error = 0;
 546         int i;
 547
 548         if (bus->drv_attrs) {
 549                 for (i = 0; attr_name(bus->drv_attrs[i]); i++) {
 550                         error = driver_create_file(drv, &bus->drv_attrs[i]);
 551                         if (error)
 552                                 goto err;
 553                 }
 554         }
 555 done:
 556         return error;
 557 err:
 558         while (--i >= 0)
 559                 driver_remove_file(drv, &bus->drv_attrs[i]);
 560         goto done;
 561 }
 562
 563 static void driver_remove_attrs(struct bus_type *bus,
 564                                 struct device_driver *drv)
 565 {
 566         int i;
 567
 568         if (bus->drv_attrs) {
 569                 for (i = 0; attr_name(bus->drv_attrs[i]); i++)
 570                         driver_remove_file(drv, &bus->drv_attrs[i]);
 571         }
 572 }
 573
 574 #ifdef CONFIG_HOTPLUG
 575 /*
 576  * Thanks to drivers making their tables __devinit, we can't allow manual
 577  * bind and unbind from userspace unless CONFIG_HOTPLUG is enabled.
 578  */
 579 static int __must_check add_bind_files(struct device_driver *drv)
 580 {
 581         int ret;
 582
 583         ret = driver_create_file(drv, &driver_attr_unbind);
 584         if (ret == 0) {
 585                 ret = driver_create_file(drv, &driver_attr_bind);
 586                 if (ret)
 587                         driver_remove_file(drv, &driver_attr_unbind);
 588         }
 589         return ret;
 590 }
 591
 592 static void remove_bind_files(struct device_driver *drv)
 593 {
 594         driver_remove_file(drv, &driver_attr_bind);
 595         driver_remove_file(drv, &driver_attr_unbind);
 596 }
 597
 598 static BUS_ATTR(drivers_probe, S_IWUSR, NULL, store_drivers_probe);
 599 static BUS_ATTR(drivers_autoprobe, S_IWUSR | S_IRUGO,
 600                 show_drivers_autoprobe, store_drivers_autoprobe);
 601
 602 static int add_probe_files(struct bus_type *bus)
 603 {
 604         int retval;
 605
 606         retval = bus_create_file(bus, &bus_attr_drivers_probe);
 607         if (retval)
 608                 goto out;
 609
 610         retval = bus_create_file(bus, &bus_attr_drivers_autoprobe);
 611         if (retval)
 612                 bus_remove_file(bus, &bus_attr_drivers_probe);
 613 out:
 614         return retval;
 615 }
 616
 617 static void remove_probe_files(struct bus_type *bus)
 618 {
 619         bus_remove_file(bus, &bus_attr_drivers_autoprobe);
 620         bus_remove_file(bus, &bus_attr_drivers_probe);
 621 }
 622 #else
 623 static inline int add_bind_files(struct device_driver *drv) { return 0; }
 624 static inline void remove_bind_files(struct device_driver *drv) {}
 625 static inline int add_probe_files(struct bus_type *bus) { return 0; }
 626 static inline void remove_probe_files(struct bus_type *bus) {}
 627 #endif
 628
 629 static ssize_t driver_uevent_store(struct device_driver *drv,
 630                                    const char *buf, size_t count)
 631 {
 632         enum kobject_action action;
 633
 634         if (kobject_action_type(buf, count, &action) == 0)
 635                 kobject_uevent(&drv->p->kobj, action);
 636         return count;
 637 }
 638 static DRIVER_ATTR(uevent, S_IWUSR, NULL, driver_uevent_store);
 639
 640 /**
 641  * bus_add_driver - Add a driver to the bus.
 642  * @drv: driver.
 643  */
 644 int bus_add_driver(struct device_driver *drv)
 645 {
 646         struct bus_type *bus;
 647         struct driver_private *priv;
 648         int error = 0;
 649
 650         bus = bus_get(drv->bus);
 651         if (!bus)
 652                 return -EINVAL;
 653
 654         pr_debug("bus: '%s': add driver %s\n", bus->name, drv->name);
 655
 656         priv = kzalloc(sizeof(*priv), GFP_KERNEL);
 657         if (!priv) {
 658                 error = -ENOMEM;
 659                 goto out_put_bus;
 660         }
 661         klist_init(&priv->klist_devices, NULL, NULL);
 662         priv->driver = drv;
 663         drv->p = priv;
 664         priv->kobj.kset = bus->p->drivers_kset;
 665         error = kobject_init_and_add(&priv->kobj, &driver_ktype, NULL,
 666                                      "%s", drv->name);
 667         if (error)
 668                 goto out_unregister;
 669
 670         if (drv->bus->p->drivers_autoprobe) {
 671                 error = driver_attach(drv);
 672                 if (error)
 673                         goto out_unregister;
 674         }
 675         klist_add_tail(&priv->knode_bus, &bus->p->klist_drivers);
 676         module_add_driver(drv->owner, drv);
 677
 678         error = driver_create_file(drv, &driver_attr_uevent);
 679         if (error) {
 680                 printk(KERN_ERR "%s: uevent attr (%s) failed\n",
 681                         __func__, drv->name);
 682         }
 683         error = driver_add_attrs(bus, drv);
 684         if (error) {
 685                 /* How the hell do we get out of this pickle? Give up */
 686                 printk(KERN_ERR "%s: driver_add_attrs(%s) failed\n",
 687                         __func__, drv->name);
 688         }
 689         error = add_bind_files(drv);
 690         if (error) {
 691                 /* Ditto */
 692                 printk(KERN_ERR "%s: add_bind_files(%s) failed\n",
 693                         __func__, drv->name);
 694         }
 695
 696         kobject_uevent(&priv->kobj, KOBJ_ADD);
 697         return error;
 698 out_unregister:
 699         kobject_put(&priv->kobj);
 700 out_put_bus:
 701         bus_put(bus);
 702         return error;
 703 }
 704
 705 /**
 706  * bus_remove_driver - delete driver from bus's knowledge.
 707  * @drv: driver.
 708  *
 709  * Detach the driver from the devices it controls, and remove
 710  * it from its bus's list of drivers. Finally, we drop the reference
 711  * to the bus we took in bus_add_driver().
 712  */
 713 void bus_remove_driver(struct device_driver *drv)
 714 {
 715         if (!drv->bus)
 716                 return;
 717
 718         remove_bind_files(drv);
 719         driver_remove_attrs(drv->bus, drv);
 720         driver_remove_file(drv, &driver_attr_uevent);
 721         klist_remove(&drv->p->knode_bus);
 722         pr_debug("bus: '%s': remove driver %s\n", drv->bus->name, drv->name);
 723         driver_detach(drv);
 724         module_remove_driver(drv);
 725         kobject_put(&drv->p->kobj);
 726         bus_put(drv->bus);
 727 }
 728
 729 /* Helper for bus_rescan_devices's iter */
 730 static int __must_check bus_rescan_devices_helper(struct device *dev,
 731                                                   void *data)
 732 {
 733         int ret = 0;
 734
 735         if (!dev->driver) {
 736                 if (dev->parent)        /* Needed for USB */
 737                         down(&dev->parent->sem);
 738                 ret = device_attach(dev);
 739                 if (dev->parent)
 740                         up(&dev->parent->sem);
 741         }
 742         return ret < 0 ? ret : 0;
 743 }
 744
 745 /**
 746  * bus_rescan_devices - rescan devices on the bus for possible drivers
 747  * @bus: the bus to scan.
 748  *
 749  * This function will look for devices on the bus with no driver
 750  * attached and rescan it against existing drivers to see if it matches
 751  * any by calling device_attach() for the unbound devices.
 752  */
 753 int bus_rescan_devices(struct bus_type *bus)
 754 {
 755         return bus_for_each_dev(bus, NULL, NULL, bus_rescan_devices_helper);
 756 }
 757 EXPORT_SYMBOL_GPL(bus_rescan_devices);
 758
 759 /**
 760  * device_reprobe - remove driver for a device and probe for a new driver
 761  * @dev: the device to reprobe
 762  *
 763  * This function detaches the attached driver (if any) for the given
 764  * device and restarts the driver probing process.  It is intended
 765  * to use if probing criteria changed during a devices lifetime and
 766  * driver attachment should change accordingly.
 767  */
 768 int device_reprobe(struct device *dev)
 769 {
 770         if (dev->driver) {
 771                 if (dev->parent)        /* Needed for USB */
 772                         down(&dev->parent->sem);
 773                 device_release_driver(dev);
 774                 if (dev->parent)
 775                         up(&dev->parent->sem);
 776         }
 777         return bus_rescan_devices_helper(dev, NULL);
 778 }
 779 EXPORT_SYMBOL_GPL(device_reprobe);
 780
 781 /**
 782  * find_bus - locate bus by name.
 783  * @name: name of bus.
 784  *
 785  * Call kset_find_obj() to iterate over list of buses to
 786  * find a bus by name. Return bus if found.
 787  *
 788  * Note that kset_find_obj increments bus' reference count.
 789  */
 790 #if 0
 791 struct bus_type *find_bus(char *name)
 792 {
 793         struct kobject *k = kset_find_obj(bus_kset, name);
 794         return k ? to_bus(k) : NULL;
 795 }
 796 #endif  /*  0  */
 797
 798
 799 /**
 800  * bus_add_attrs - Add default attributes for this bus.
 801  * @bus: Bus that has just been registered.
 802  */
 803
 804 static int bus_add_attrs(struct bus_type *bus)
 805 {
 806         int error = 0;
 807         int i;
 808
 809         if (bus->bus_attrs) {
 810                 for (i = 0; attr_name(bus->bus_attrs[i]); i++) {
 811                         error = bus_create_file(bus, &bus->bus_attrs[i]);
 812                         if (error)
 813                                 goto err;
 814                 }
 815         }
 816 done:
 817         return error;
 818 err:
 819         while (--i >= 0)
 820                 bus_remove_file(bus, &bus->bus_attrs[i]);
 821         goto done;
 822 }
 823
 824 static void bus_remove_attrs(struct bus_type *bus)
 825 {
 826         int i;
 827
 828         if (bus->bus_attrs) {
 829                 for (i = 0; attr_name(bus->bus_attrs[i]); i++)
 830                         bus_remove_file(bus, &bus->bus_attrs[i]);
 831         }
 832 }
 833
 834 static void klist_devices_get(struct klist_node *n)
 835 {
 836         struct device *dev = container_of(n, struct device, knode_bus);
 837
 838         get_device(dev);
 839 }
 840
 841 static void klist_devices_put(struct klist_node *n)
 842 {
 843         struct device *dev = container_of(n, struct device, knode_bus);
 844
 845         put_device(dev);
 846 }
 847
 848 static ssize_t bus_uevent_store(struct bus_type *bus,
 849                                 const char *buf, size_t count)
 850 {
 851         enum kobject_action action;
 852
 853         if (kobject_action_type(buf, count, &action) == 0)
 854                 kobject_uevent(&bus->p->subsys.kobj, action);
 855         return count;
 856 }
 857 static BUS_ATTR(uevent, S_IWUSR, NULL, bus_uevent_store);
 858
 859 /**
 860  * bus_register - register a bus with the system.
 861  * @bus: bus.
 862  *
 863  * Once we have that, we registered the bus with the kobject
 864  * infrastructure, then register the children subsystems it has:
 865  * the devices and drivers that belong to the bus.
 866  */
 867 int bus_register(struct bus_type *bus)
 868 {
 869         int retval;
 870         struct bus_type_private *priv;
 871
 872         priv = kzalloc(sizeof(struct bus_type_private), GFP_KERNEL);
 873         if (!priv)
 874                 return -ENOMEM;
 875
 876         priv->bus = bus;
 877         bus->p = priv;
 878
 879         BLOCKING_INIT_NOTIFIER_HEAD(&priv->bus_notifier);
 880
 881         retval = kobject_set_name(&priv->subsys.kobj, "%s", bus->name);
 882         if (retval)
 883                 goto out;
 884
 885         priv->subsys.kobj.kset = bus_kset;
 886         priv->subsys.kobj.ktype = &bus_ktype;
 887         priv->drivers_autoprobe = 1;
 888
 889         retval = kset_register(&priv->subsys);
 890         if (retval)
 891                 goto out;
 892
 893         retval = bus_create_file(bus, &bus_attr_uevent);
 894         if (retval)
 895                 goto bus_uevent_fail;
 896
 897         priv->devices_kset = kset_create_and_add("devices", NULL,
 898                                                  &priv->subsys.kobj);
 899         if (!priv->devices_kset) {
 900                 retval = -ENOMEM;
 901                 goto bus_devices_fail;
 902         }
 903
 904         priv->drivers_kset = kset_create_and_add("drivers", NULL,
 905                                                  &priv->subsys.kobj);
 906         if (!priv->drivers_kset) {
 907                 retval = -ENOMEM;
 908                 goto bus_drivers_fail;
 909         }
 910
 911         klist_init(&priv->klist_devices, klist_devices_get, klist_devices_put);
 912         klist_init(&priv->klist_drivers, NULL, NULL);
 913
 914         retval = add_probe_files(bus);
 915         if (retval)
 916                 goto bus_probe_files_fail;
 917
 918         retval = bus_add_attrs(bus);
 919         if (retval)
 920                 goto bus_attrs_fail;
 921
 922         pr_debug("bus: '%s': registered\n", bus->name);
 923         return 0;
 924
 925 bus_attrs_fail:
 926         remove_probe_files(bus);
 927 bus_probe_files_fail:
 928         kset_unregister(bus->p->drivers_kset);
 929 bus_drivers_fail:
 930         kset_unregister(bus->p->devices_kset);
 931 bus_devices_fail:
 932         bus_remove_file(bus, &bus_attr_uevent);
 933 bus_uevent_fail:
 934         kset_unregister(&bus->p->subsys);
 935         kfree(bus->p);
 936 out:
 937         return retval;
 938 }
 939 EXPORT_SYMBOL_GPL(bus_register);
 940
 941 /**
 942  * bus_unregister - remove a bus from the system
 943  * @bus: bus.
 944  *
 945  * Unregister the child subsystems and the bus itself.
 946  * Finally, we call bus_put() to release the refcount
 947  */
 948 void bus_unregister(struct bus_type *bus)
 949 {
 950         pr_debug("bus: '%s': unregistering\n", bus->name);
 951         bus_remove_attrs(bus);
 952         remove_probe_files(bus);
 953         kset_unregister(bus->p->drivers_kset);
 954         kset_unregister(bus->p->devices_kset);
 955         bus_remove_file(bus, &bus_attr_uevent);
 956         kset_unregister(&bus->p->subsys);
 957         kfree(bus->p);
 958 }
 959 EXPORT_SYMBOL_GPL(bus_unregister);
 960
 961 int bus_register_notifier(struct bus_type *bus, struct notifier_block *nb)
 962 {
 963         return blocking_notifier_chain_register(&bus->p->bus_notifier, nb);
 964 }
 965 EXPORT_SYMBOL_GPL(bus_register_notifier);
 966
 967 int bus_unregister_notifier(struct bus_type *bus, struct notifier_block *nb)
 968 {
 969         return blocking_notifier_chain_unregister(&bus->p->bus_notifier, nb);
 970 }
 971 EXPORT_SYMBOL_GPL(bus_unregister_notifier);
 972
 973 struct kset *bus_get_kset(struct bus_type *bus)
 974 {
 975         return &bus->p->subsys;
 976 }
 977 EXPORT_SYMBOL_GPL(bus_get_kset);
 978
 979 struct klist *bus_get_device_klist(struct bus_type *bus)
 980 {
 981         return &bus->p->klist_devices;
 982 }
 983 EXPORT_SYMBOL_GPL(bus_get_device_klist);
 984
 985 int __init buses_init(void)
 986 {
 987         bus_kset = kset_create_and_add("bus", &bus_uevent_ops, NULL);
 988         if (!bus_kset)
 989                 return -ENOMEM;
 990         return 0;
 991 }