linux/drivers/base/class.c
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   1/*
   2 * class.c - basic device class management
   3 *
   4 * Copyright (c) 2002-3 Patrick Mochel
   5 * Copyright (c) 2002-3 Open Source Development Labs
   6 * Copyright (c) 2003-2004 Greg Kroah-Hartman
   7 * Copyright (c) 2003-2004 IBM Corp.
   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/init.h>
  16#include <linux/string.h>
  17#include <linux/kdev_t.h>
  18#include <linux/err.h>
  19#include <linux/slab.h>
  20#include <linux/genhd.h>
  21#include <linux/mutex.h>
  22#include "base.h"
  23
  24#define to_class_attr(_attr) container_of(_attr, struct class_attribute, attr)
  25
  26static ssize_t class_attr_show(struct kobject *kobj, struct attribute *attr,
  27                               char *buf)
  28{
  29        struct class_attribute *class_attr = to_class_attr(attr);
  30        struct class_private *cp = to_class(kobj);
  31        ssize_t ret = -EIO;
  32
  33        if (class_attr->show)
  34                ret = class_attr->show(cp->class, class_attr, buf);
  35        return ret;
  36}
  37
  38static ssize_t class_attr_store(struct kobject *kobj, struct attribute *attr,
  39                                const char *buf, size_t count)
  40{
  41        struct class_attribute *class_attr = to_class_attr(attr);
  42        struct class_private *cp = to_class(kobj);
  43        ssize_t ret = -EIO;
  44
  45        if (class_attr->store)
  46                ret = class_attr->store(cp->class, class_attr, buf, count);
  47        return ret;
  48}
  49
  50static void class_release(struct kobject *kobj)
  51{
  52        struct class_private *cp = to_class(kobj);
  53        struct class *class = cp->class;
  54
  55        pr_debug("class '%s': release.\n", class->name);
  56
  57        if (class->class_release)
  58                class->class_release(class);
  59        else
  60                pr_debug("class '%s' does not have a release() function, "
  61                         "be careful\n", class->name);
  62
  63        kfree(cp);
  64}
  65
  66static const struct kobj_ns_type_operations *class_child_ns_type(struct kobject *kobj)
  67{
  68        struct class_private *cp = to_class(kobj);
  69        struct class *class = cp->class;
  70
  71        return class->ns_type;
  72}
  73
  74static const struct sysfs_ops class_sysfs_ops = {
  75        .show   = class_attr_show,
  76        .store  = class_attr_store,
  77};
  78
  79static struct kobj_type class_ktype = {
  80        .sysfs_ops      = &class_sysfs_ops,
  81        .release        = class_release,
  82        .child_ns_type  = class_child_ns_type,
  83};
  84
  85/* Hotplug events for classes go to the class class_subsys */
  86static struct kset *class_kset;
  87
  88
  89int class_create_file(struct class *cls, const struct class_attribute *attr)
  90{
  91        int error;
  92        if (cls)
  93                error = sysfs_create_file(&cls->p->class_subsys.kobj,
  94                                          &attr->attr);
  95        else
  96                error = -EINVAL;
  97        return error;
  98}
  99
 100void class_remove_file(struct class *cls, const struct class_attribute *attr)
 101{
 102        if (cls)
 103                sysfs_remove_file(&cls->p->class_subsys.kobj, &attr->attr);
 104}
 105
 106static struct class *class_get(struct class *cls)
 107{
 108        if (cls)
 109                kset_get(&cls->p->class_subsys);
 110        return cls;
 111}
 112
 113static void class_put(struct class *cls)
 114{
 115        if (cls)
 116                kset_put(&cls->p->class_subsys);
 117}
 118
 119static int add_class_attrs(struct class *cls)
 120{
 121        int i;
 122        int error = 0;
 123
 124        if (cls->class_attrs) {
 125                for (i = 0; attr_name(cls->class_attrs[i]); i++) {
 126                        error = class_create_file(cls, &cls->class_attrs[i]);
 127                        if (error)
 128                                goto error;
 129                }
 130        }
 131done:
 132        return error;
 133error:
 134        while (--i >= 0)
 135                class_remove_file(cls, &cls->class_attrs[i]);
 136        goto done;
 137}
 138
 139static void remove_class_attrs(struct class *cls)
 140{
 141        int i;
 142
 143        if (cls->class_attrs) {
 144                for (i = 0; attr_name(cls->class_attrs[i]); i++)
 145                        class_remove_file(cls, &cls->class_attrs[i]);
 146        }
 147}
 148
 149static void klist_class_dev_get(struct klist_node *n)
 150{
 151        struct device *dev = container_of(n, struct device, knode_class);
 152
 153        get_device(dev);
 154}
 155
 156static void klist_class_dev_put(struct klist_node *n)
 157{
 158        struct device *dev = container_of(n, struct device, knode_class);
 159
 160        put_device(dev);
 161}
 162
 163int __class_register(struct class *cls, struct lock_class_key *key)
 164{
 165        struct class_private *cp;
 166        int error;
 167
 168        pr_debug("device class '%s': registering\n", cls->name);
 169
 170        cp = kzalloc(sizeof(*cp), GFP_KERNEL);
 171        if (!cp)
 172                return -ENOMEM;
 173        klist_init(&cp->class_devices, klist_class_dev_get, klist_class_dev_put);
 174        INIT_LIST_HEAD(&cp->class_interfaces);
 175        kset_init(&cp->class_dirs);
 176        __mutex_init(&cp->class_mutex, "struct class mutex", key);
 177        error = kobject_set_name(&cp->class_subsys.kobj, "%s", cls->name);
 178        if (error) {
 179                kfree(cp);
 180                return error;
 181        }
 182
 183        /* set the default /sys/dev directory for devices of this class */
 184        if (!cls->dev_kobj)
 185                cls->dev_kobj = sysfs_dev_char_kobj;
 186
 187#if defined(CONFIG_BLOCK)
 188        /* let the block class directory show up in the root of sysfs */
 189        if (!sysfs_deprecated || cls != &block_class)
 190                cp->class_subsys.kobj.kset = class_kset;
 191#else
 192        cp->class_subsys.kobj.kset = class_kset;
 193#endif
 194        cp->class_subsys.kobj.ktype = &class_ktype;
 195        cp->class = cls;
 196        cls->p = cp;
 197
 198        error = kset_register(&cp->class_subsys);
 199        if (error) {
 200                kfree(cp);
 201                return error;
 202        }
 203        error = add_class_attrs(class_get(cls));
 204        class_put(cls);
 205        return error;
 206}
 207EXPORT_SYMBOL_GPL(__class_register);
 208
 209void class_unregister(struct class *cls)
 210{
 211        pr_debug("device class '%s': unregistering\n", cls->name);
 212        remove_class_attrs(cls);
 213        kset_unregister(&cls->p->class_subsys);
 214}
 215
 216static void class_create_release(struct class *cls)
 217{
 218        pr_debug("%s called for %s\n", __func__, cls->name);
 219        kfree(cls);
 220}
 221
 222/**
 223 * class_create - create a struct class structure
 224 * @owner: pointer to the module that is to "own" this struct class
 225 * @name: pointer to a string for the name of this class.
 226 * @key: the lock_class_key for this class; used by mutex lock debugging
 227 *
 228 * This is used to create a struct class pointer that can then be used
 229 * in calls to device_create().
 230 *
 231 * Returns &struct class pointer on success, or ERR_PTR() on error.
 232 *
 233 * Note, the pointer created here is to be destroyed when finished by
 234 * making a call to class_destroy().
 235 */
 236struct class *__class_create(struct module *owner, const char *name,
 237                             struct lock_class_key *key)
 238{
 239        struct class *cls;
 240        int retval;
 241
 242        cls = kzalloc(sizeof(*cls), GFP_KERNEL);
 243        if (!cls) {
 244                retval = -ENOMEM;
 245                goto error;
 246        }
 247
 248        cls->name = name;
 249        cls->owner = owner;
 250        cls->class_release = class_create_release;
 251
 252        retval = __class_register(cls, key);
 253        if (retval)
 254                goto error;
 255
 256        return cls;
 257
 258error:
 259        kfree(cls);
 260        return ERR_PTR(retval);
 261}
 262EXPORT_SYMBOL_GPL(__class_create);
 263
 264/**
 265 * class_destroy - destroys a struct class structure
 266 * @cls: pointer to the struct class that is to be destroyed
 267 *
 268 * Note, the pointer to be destroyed must have been created with a call
 269 * to class_create().
 270 */
 271void class_destroy(struct class *cls)
 272{
 273        if ((cls == NULL) || (IS_ERR(cls)))
 274                return;
 275
 276        class_unregister(cls);
 277}
 278
 279/**
 280 * class_dev_iter_init - initialize class device iterator
 281 * @iter: class iterator to initialize
 282 * @class: the class we wanna iterate over
 283 * @start: the device to start iterating from, if any
 284 * @type: device_type of the devices to iterate over, NULL for all
 285 *
 286 * Initialize class iterator @iter such that it iterates over devices
 287 * of @class.  If @start is set, the list iteration will start there,
 288 * otherwise if it is NULL, the iteration starts at the beginning of
 289 * the list.
 290 */
 291void class_dev_iter_init(struct class_dev_iter *iter, struct class *class,
 292                         struct device *start, const struct device_type *type)
 293{
 294        struct klist_node *start_knode = NULL;
 295
 296        if (start)
 297                start_knode = &start->knode_class;
 298        klist_iter_init_node(&class->p->class_devices, &iter->ki, start_knode);
 299        iter->type = type;
 300}
 301EXPORT_SYMBOL_GPL(class_dev_iter_init);
 302
 303/**
 304 * class_dev_iter_next - iterate to the next device
 305 * @iter: class iterator to proceed
 306 *
 307 * Proceed @iter to the next device and return it.  Returns NULL if
 308 * iteration is complete.
 309 *
 310 * The returned device is referenced and won't be released till
 311 * iterator is proceed to the next device or exited.  The caller is
 312 * free to do whatever it wants to do with the device including
 313 * calling back into class code.
 314 */
 315struct device *class_dev_iter_next(struct class_dev_iter *iter)
 316{
 317        struct klist_node *knode;
 318        struct device *dev;
 319
 320        while (1) {
 321                knode = klist_next(&iter->ki);
 322                if (!knode)
 323                        return NULL;
 324                dev = container_of(knode, struct device, knode_class);
 325                if (!iter->type || iter->type == dev->type)
 326                        return dev;
 327        }
 328}
 329EXPORT_SYMBOL_GPL(class_dev_iter_next);
 330
 331/**
 332 * class_dev_iter_exit - finish iteration
 333 * @iter: class iterator to finish
 334 *
 335 * Finish an iteration.  Always call this function after iteration is
 336 * complete whether the iteration ran till the end or not.
 337 */
 338void class_dev_iter_exit(struct class_dev_iter *iter)
 339{
 340        klist_iter_exit(&iter->ki);
 341}
 342EXPORT_SYMBOL_GPL(class_dev_iter_exit);
 343
 344/**
 345 * class_for_each_device - device iterator
 346 * @class: the class we're iterating
 347 * @start: the device to start with in the list, if any.
 348 * @data: data for the callback
 349 * @fn: function to be called for each device
 350 *
 351 * Iterate over @class's list of devices, and call @fn for each,
 352 * passing it @data.  If @start is set, the list iteration will start
 353 * there, otherwise if it is NULL, the iteration starts at the
 354 * beginning of the list.
 355 *
 356 * We check the return of @fn each time. If it returns anything
 357 * other than 0, we break out and return that value.
 358 *
 359 * @fn is allowed to do anything including calling back into class
 360 * code.  There's no locking restriction.
 361 */
 362int class_for_each_device(struct class *class, struct device *start,
 363                          void *data, int (*fn)(struct device *, void *))
 364{
 365        struct class_dev_iter iter;
 366        struct device *dev;
 367        int error = 0;
 368
 369        if (!class)
 370                return -EINVAL;
 371        if (!class->p) {
 372                WARN(1, "%s called for class '%s' before it was initialized",
 373                     __func__, class->name);
 374                return -EINVAL;
 375        }
 376
 377        class_dev_iter_init(&iter, class, start, NULL);
 378        while ((dev = class_dev_iter_next(&iter))) {
 379                error = fn(dev, data);
 380                if (error)
 381                        break;
 382        }
 383        class_dev_iter_exit(&iter);
 384
 385        return error;
 386}
 387EXPORT_SYMBOL_GPL(class_for_each_device);
 388
 389/**
 390 * class_find_device - device iterator for locating a particular device
 391 * @class: the class we're iterating
 392 * @start: Device to begin with
 393 * @data: data for the match function
 394 * @match: function to check device
 395 *
 396 * This is similar to the class_for_each_dev() function above, but it
 397 * returns a reference to a device that is 'found' for later use, as
 398 * determined by the @match callback.
 399 *
 400 * The callback should return 0 if the device doesn't match and non-zero
 401 * if it does.  If the callback returns non-zero, this function will
 402 * return to the caller and not iterate over any more devices.
 403 *
 404 * Note, you will need to drop the reference with put_device() after use.
 405 *
 406 * @fn is allowed to do anything including calling back into class
 407 * code.  There's no locking restriction.
 408 */
 409struct device *class_find_device(struct class *class, struct device *start,
 410                                 void *data,
 411                                 int (*match)(struct device *, void *))
 412{
 413        struct class_dev_iter iter;
 414        struct device *dev;
 415
 416        if (!class)
 417                return NULL;
 418        if (!class->p) {
 419                WARN(1, "%s called for class '%s' before it was initialized",
 420                     __func__, class->name);
 421                return NULL;
 422        }
 423
 424        class_dev_iter_init(&iter, class, start, NULL);
 425        while ((dev = class_dev_iter_next(&iter))) {
 426                if (match(dev, data)) {
 427                        get_device(dev);
 428                        break;
 429                }
 430        }
 431        class_dev_iter_exit(&iter);
 432
 433        return dev;
 434}
 435EXPORT_SYMBOL_GPL(class_find_device);
 436
 437int class_interface_register(struct class_interface *class_intf)
 438{
 439        struct class *parent;
 440        struct class_dev_iter iter;
 441        struct device *dev;
 442
 443        if (!class_intf || !class_intf->class)
 444                return -ENODEV;
 445
 446        parent = class_get(class_intf->class);
 447        if (!parent)
 448                return -EINVAL;
 449
 450        mutex_lock(&parent->p->class_mutex);
 451        list_add_tail(&class_intf->node, &parent->p->class_interfaces);
 452        if (class_intf->add_dev) {
 453                class_dev_iter_init(&iter, parent, NULL, NULL);
 454                while ((dev = class_dev_iter_next(&iter)))
 455                        class_intf->add_dev(dev, class_intf);
 456                class_dev_iter_exit(&iter);
 457        }
 458        mutex_unlock(&parent->p->class_mutex);
 459
 460        return 0;
 461}
 462
 463void class_interface_unregister(struct class_interface *class_intf)
 464{
 465        struct class *parent = class_intf->class;
 466        struct class_dev_iter iter;
 467        struct device *dev;
 468
 469        if (!parent)
 470                return;
 471
 472        mutex_lock(&parent->p->class_mutex);
 473        list_del_init(&class_intf->node);
 474        if (class_intf->remove_dev) {
 475                class_dev_iter_init(&iter, parent, NULL, NULL);
 476                while ((dev = class_dev_iter_next(&iter)))
 477                        class_intf->remove_dev(dev, class_intf);
 478                class_dev_iter_exit(&iter);
 479        }
 480        mutex_unlock(&parent->p->class_mutex);
 481
 482        class_put(parent);
 483}
 484
 485ssize_t show_class_attr_string(struct class *class, struct class_attribute *attr,
 486                                char *buf)
 487{
 488        struct class_attribute_string *cs;
 489        cs = container_of(attr, struct class_attribute_string, attr);
 490        return snprintf(buf, PAGE_SIZE, "%s\n", cs->str);
 491}
 492
 493EXPORT_SYMBOL_GPL(show_class_attr_string);
 494
 495struct class_compat {
 496        struct kobject *kobj;
 497};
 498
 499/**
 500 * class_compat_register - register a compatibility class
 501 * @name: the name of the class
 502 *
 503 * Compatibility class are meant as a temporary user-space compatibility
 504 * workaround when converting a family of class devices to a bus devices.
 505 */
 506struct class_compat *class_compat_register(const char *name)
 507{
 508        struct class_compat *cls;
 509
 510        cls = kmalloc(sizeof(struct class_compat), GFP_KERNEL);
 511        if (!cls)
 512                return NULL;
 513        cls->kobj = kobject_create_and_add(name, &class_kset->kobj);
 514        if (!cls->kobj) {
 515                kfree(cls);
 516                return NULL;
 517        }
 518        return cls;
 519}
 520EXPORT_SYMBOL_GPL(class_compat_register);
 521
 522/**
 523 * class_compat_unregister - unregister a compatibility class
 524 * @cls: the class to unregister
 525 */
 526void class_compat_unregister(struct class_compat *cls)
 527{
 528        kobject_put(cls->kobj);
 529        kfree(cls);
 530}
 531EXPORT_SYMBOL_GPL(class_compat_unregister);
 532
 533/**
 534 * class_compat_create_link - create a compatibility class device link to
 535 *                            a bus device
 536 * @cls: the compatibility class
 537 * @dev: the target bus device
 538 * @device_link: an optional device to which a "device" link should be created
 539 */
 540int class_compat_create_link(struct class_compat *cls, struct device *dev,
 541                             struct device *device_link)
 542{
 543        int error;
 544
 545        error = sysfs_create_link(cls->kobj, &dev->kobj, dev_name(dev));
 546        if (error)
 547                return error;
 548
 549        /*
 550         * Optionally add a "device" link (typically to the parent), as a
 551         * class device would have one and we want to provide as much
 552         * backwards compatibility as possible.
 553         */
 554        if (device_link) {
 555                error = sysfs_create_link(&dev->kobj, &device_link->kobj,
 556                                          "device");
 557                if (error)
 558                        sysfs_remove_link(cls->kobj, dev_name(dev));
 559        }
 560
 561        return error;
 562}
 563EXPORT_SYMBOL_GPL(class_compat_create_link);
 564
 565/**
 566 * class_compat_remove_link - remove a compatibility class device link to
 567 *                            a bus device
 568 * @cls: the compatibility class
 569 * @dev: the target bus device
 570 * @device_link: an optional device to which a "device" link was previously
 571 *               created
 572 */
 573void class_compat_remove_link(struct class_compat *cls, struct device *dev,
 574                              struct device *device_link)
 575{
 576        if (device_link)
 577                sysfs_remove_link(&dev->kobj, "device");
 578        sysfs_remove_link(cls->kobj, dev_name(dev));
 579}
 580EXPORT_SYMBOL_GPL(class_compat_remove_link);
 581
 582int __init classes_init(void)
 583{
 584        class_kset = kset_create_and_add("class", NULL, NULL);
 585        if (!class_kset)
 586                return -ENOMEM;
 587        return 0;
 588}
 589
 590EXPORT_SYMBOL_GPL(class_create_file);
 591EXPORT_SYMBOL_GPL(class_remove_file);
 592EXPORT_SYMBOL_GPL(class_unregister);
 593EXPORT_SYMBOL_GPL(class_destroy);
 594
 595EXPORT_SYMBOL_GPL(class_interface_register);
 596EXPORT_SYMBOL_GPL(class_interface_unregister);
 597