linux/drivers/base/class.c
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   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 * class.c - basic device class management
   4 *
   5 * Copyright (c) 2002-3 Patrick Mochel
   6 * Copyright (c) 2002-3 Open Source Development Labs
   7 * Copyright (c) 2003-2004 Greg Kroah-Hartman
   8 * Copyright (c) 2003-2004 IBM Corp.
   9 */
  10
  11#include <linux/device/class.h>
  12#include <linux/device.h>
  13#include <linux/module.h>
  14#include <linux/init.h>
  15#include <linux/string.h>
  16#include <linux/kdev_t.h>
  17#include <linux/err.h>
  18#include <linux/slab.h>
  19#include <linux/genhd.h>
  20#include <linux/mutex.h>
  21#include "base.h"
  22
  23#define to_class_attr(_attr) container_of(_attr, struct class_attribute, attr)
  24
  25static ssize_t class_attr_show(struct kobject *kobj, struct attribute *attr,
  26                               char *buf)
  27{
  28        struct class_attribute *class_attr = to_class_attr(attr);
  29        struct subsys_private *cp = to_subsys_private(kobj);
  30        ssize_t ret = -EIO;
  31
  32        if (class_attr->show)
  33                ret = class_attr->show(cp->class, class_attr, buf);
  34        return ret;
  35}
  36
  37static ssize_t class_attr_store(struct kobject *kobj, struct attribute *attr,
  38                                const char *buf, size_t count)
  39{
  40        struct class_attribute *class_attr = to_class_attr(attr);
  41        struct subsys_private *cp = to_subsys_private(kobj);
  42        ssize_t ret = -EIO;
  43
  44        if (class_attr->store)
  45                ret = class_attr->store(cp->class, class_attr, buf, count);
  46        return ret;
  47}
  48
  49static void class_release(struct kobject *kobj)
  50{
  51        struct subsys_private *cp = to_subsys_private(kobj);
  52        struct class *class = cp->class;
  53
  54        pr_debug("class '%s': release.\n", class->name);
  55
  56        if (class->class_release)
  57                class->class_release(class);
  58        else
  59                pr_debug("class '%s' does not have a release() function, "
  60                         "be careful\n", class->name);
  61
  62        kfree(cp);
  63}
  64
  65static const struct kobj_ns_type_operations *class_child_ns_type(struct kobject *kobj)
  66{
  67        struct subsys_private *cp = to_subsys_private(kobj);
  68        struct class *class = cp->class;
  69
  70        return class->ns_type;
  71}
  72
  73static const struct sysfs_ops class_sysfs_ops = {
  74        .show      = class_attr_show,
  75        .store     = class_attr_store,
  76};
  77
  78static struct kobj_type class_ktype = {
  79        .sysfs_ops      = &class_sysfs_ops,
  80        .release        = class_release,
  81        .child_ns_type  = class_child_ns_type,
  82};
  83
  84/* Hotplug events for classes go to the class subsys */
  85static struct kset *class_kset;
  86
  87
  88int class_create_file_ns(struct class *cls, const struct class_attribute *attr,
  89                         const void *ns)
  90{
  91        int error;
  92
  93        if (cls)
  94                error = sysfs_create_file_ns(&cls->p->subsys.kobj,
  95                                             &attr->attr, ns);
  96        else
  97                error = -EINVAL;
  98        return error;
  99}
 100
 101void class_remove_file_ns(struct class *cls, const struct class_attribute *attr,
 102                          const void *ns)
 103{
 104        if (cls)
 105                sysfs_remove_file_ns(&cls->p->subsys.kobj, &attr->attr, ns);
 106}
 107
 108static struct class *class_get(struct class *cls)
 109{
 110        if (cls)
 111                kset_get(&cls->p->subsys);
 112        return cls;
 113}
 114
 115static void class_put(struct class *cls)
 116{
 117        if (cls)
 118                kset_put(&cls->p->subsys);
 119}
 120
 121static struct device *klist_class_to_dev(struct klist_node *n)
 122{
 123        struct device_private *p = to_device_private_class(n);
 124        return p->device;
 125}
 126
 127static void klist_class_dev_get(struct klist_node *n)
 128{
 129        struct device *dev = klist_class_to_dev(n);
 130
 131        get_device(dev);
 132}
 133
 134static void klist_class_dev_put(struct klist_node *n)
 135{
 136        struct device *dev = klist_class_to_dev(n);
 137
 138        put_device(dev);
 139}
 140
 141static int class_add_groups(struct class *cls,
 142                            const struct attribute_group **groups)
 143{
 144        return sysfs_create_groups(&cls->p->subsys.kobj, groups);
 145}
 146
 147static void class_remove_groups(struct class *cls,
 148                                const struct attribute_group **groups)
 149{
 150        return sysfs_remove_groups(&cls->p->subsys.kobj, groups);
 151}
 152
 153int __class_register(struct class *cls, struct lock_class_key *key)
 154{
 155        struct subsys_private *cp;
 156        int error;
 157
 158        pr_debug("device class '%s': registering\n", cls->name);
 159
 160        cp = kzalloc(sizeof(*cp), GFP_KERNEL);
 161        if (!cp)
 162                return -ENOMEM;
 163        klist_init(&cp->klist_devices, klist_class_dev_get, klist_class_dev_put);
 164        INIT_LIST_HEAD(&cp->interfaces);
 165        kset_init(&cp->glue_dirs);
 166        __mutex_init(&cp->mutex, "subsys mutex", key);
 167        error = kobject_set_name(&cp->subsys.kobj, "%s", cls->name);
 168        if (error) {
 169                kfree(cp);
 170                return error;
 171        }
 172
 173        /* set the default /sys/dev directory for devices of this class */
 174        if (!cls->dev_kobj)
 175                cls->dev_kobj = sysfs_dev_char_kobj;
 176
 177#if defined(CONFIG_BLOCK)
 178        /* let the block class directory show up in the root of sysfs */
 179        if (!sysfs_deprecated || cls != &block_class)
 180                cp->subsys.kobj.kset = class_kset;
 181#else
 182        cp->subsys.kobj.kset = class_kset;
 183#endif
 184        cp->subsys.kobj.ktype = &class_ktype;
 185        cp->class = cls;
 186        cls->p = cp;
 187
 188        error = kset_register(&cp->subsys);
 189        if (error) {
 190                kfree(cp);
 191                return error;
 192        }
 193        error = class_add_groups(class_get(cls), cls->class_groups);
 194        class_put(cls);
 195        return error;
 196}
 197EXPORT_SYMBOL_GPL(__class_register);
 198
 199void class_unregister(struct class *cls)
 200{
 201        pr_debug("device class '%s': unregistering\n", cls->name);
 202        class_remove_groups(cls, cls->class_groups);
 203        kset_unregister(&cls->p->subsys);
 204}
 205
 206static void class_create_release(struct class *cls)
 207{
 208        pr_debug("%s called for %s\n", __func__, cls->name);
 209        kfree(cls);
 210}
 211
 212/**
 213 * class_create - create a struct class structure
 214 * @owner: pointer to the module that is to "own" this struct class
 215 * @name: pointer to a string for the name of this class.
 216 * @key: the lock_class_key for this class; used by mutex lock debugging
 217 *
 218 * This is used to create a struct class pointer that can then be used
 219 * in calls to device_create().
 220 *
 221 * Returns &struct class pointer on success, or ERR_PTR() on error.
 222 *
 223 * Note, the pointer created here is to be destroyed when finished by
 224 * making a call to class_destroy().
 225 */
 226struct class *__class_create(struct module *owner, const char *name,
 227                             struct lock_class_key *key)
 228{
 229        struct class *cls;
 230        int retval;
 231
 232        cls = kzalloc(sizeof(*cls), GFP_KERNEL);
 233        if (!cls) {
 234                retval = -ENOMEM;
 235                goto error;
 236        }
 237
 238        cls->name = name;
 239        cls->owner = owner;
 240        cls->class_release = class_create_release;
 241
 242        retval = __class_register(cls, key);
 243        if (retval)
 244                goto error;
 245
 246        return cls;
 247
 248error:
 249        kfree(cls);
 250        return ERR_PTR(retval);
 251}
 252EXPORT_SYMBOL_GPL(__class_create);
 253
 254/**
 255 * class_destroy - destroys a struct class structure
 256 * @cls: pointer to the struct class that is to be destroyed
 257 *
 258 * Note, the pointer to be destroyed must have been created with a call
 259 * to class_create().
 260 */
 261void class_destroy(struct class *cls)
 262{
 263        if ((cls == NULL) || (IS_ERR(cls)))
 264                return;
 265
 266        class_unregister(cls);
 267}
 268
 269/**
 270 * class_dev_iter_init - initialize class device iterator
 271 * @iter: class iterator to initialize
 272 * @class: the class we wanna iterate over
 273 * @start: the device to start iterating from, if any
 274 * @type: device_type of the devices to iterate over, NULL for all
 275 *
 276 * Initialize class iterator @iter such that it iterates over devices
 277 * of @class.  If @start is set, the list iteration will start there,
 278 * otherwise if it is NULL, the iteration starts at the beginning of
 279 * the list.
 280 */
 281void class_dev_iter_init(struct class_dev_iter *iter, struct class *class,
 282                         struct device *start, const struct device_type *type)
 283{
 284        struct klist_node *start_knode = NULL;
 285
 286        if (start)
 287                start_knode = &start->p->knode_class;
 288        klist_iter_init_node(&class->p->klist_devices, &iter->ki, start_knode);
 289        iter->type = type;
 290}
 291EXPORT_SYMBOL_GPL(class_dev_iter_init);
 292
 293/**
 294 * class_dev_iter_next - iterate to the next device
 295 * @iter: class iterator to proceed
 296 *
 297 * Proceed @iter to the next device and return it.  Returns NULL if
 298 * iteration is complete.
 299 *
 300 * The returned device is referenced and won't be released till
 301 * iterator is proceed to the next device or exited.  The caller is
 302 * free to do whatever it wants to do with the device including
 303 * calling back into class code.
 304 */
 305struct device *class_dev_iter_next(struct class_dev_iter *iter)
 306{
 307        struct klist_node *knode;
 308        struct device *dev;
 309
 310        while (1) {
 311                knode = klist_next(&iter->ki);
 312                if (!knode)
 313                        return NULL;
 314                dev = klist_class_to_dev(knode);
 315                if (!iter->type || iter->type == dev->type)
 316                        return dev;
 317        }
 318}
 319EXPORT_SYMBOL_GPL(class_dev_iter_next);
 320
 321/**
 322 * class_dev_iter_exit - finish iteration
 323 * @iter: class iterator to finish
 324 *
 325 * Finish an iteration.  Always call this function after iteration is
 326 * complete whether the iteration ran till the end or not.
 327 */
 328void class_dev_iter_exit(struct class_dev_iter *iter)
 329{
 330        klist_iter_exit(&iter->ki);
 331}
 332EXPORT_SYMBOL_GPL(class_dev_iter_exit);
 333
 334/**
 335 * class_for_each_device - device iterator
 336 * @class: the class we're iterating
 337 * @start: the device to start with in the list, if any.
 338 * @data: data for the callback
 339 * @fn: function to be called for each device
 340 *
 341 * Iterate over @class's list of devices, and call @fn for each,
 342 * passing it @data.  If @start is set, the list iteration will start
 343 * there, otherwise if it is NULL, the iteration starts at the
 344 * beginning of the list.
 345 *
 346 * We check the return of @fn each time. If it returns anything
 347 * other than 0, we break out and return that value.
 348 *
 349 * @fn is allowed to do anything including calling back into class
 350 * code.  There's no locking restriction.
 351 */
 352int class_for_each_device(struct class *class, struct device *start,
 353                          void *data, int (*fn)(struct device *, void *))
 354{
 355        struct class_dev_iter iter;
 356        struct device *dev;
 357        int error = 0;
 358
 359        if (!class)
 360                return -EINVAL;
 361        if (!class->p) {
 362                WARN(1, "%s called for class '%s' before it was initialized",
 363                     __func__, class->name);
 364                return -EINVAL;
 365        }
 366
 367        class_dev_iter_init(&iter, class, start, NULL);
 368        while ((dev = class_dev_iter_next(&iter))) {
 369                error = fn(dev, data);
 370                if (error)
 371                        break;
 372        }
 373        class_dev_iter_exit(&iter);
 374
 375        return error;
 376}
 377EXPORT_SYMBOL_GPL(class_for_each_device);
 378
 379/**
 380 * class_find_device - device iterator for locating a particular device
 381 * @class: the class we're iterating
 382 * @start: Device to begin with
 383 * @data: data for the match function
 384 * @match: function to check device
 385 *
 386 * This is similar to the class_for_each_dev() function above, but it
 387 * returns a reference to a device that is 'found' for later use, as
 388 * determined by the @match callback.
 389 *
 390 * The callback should return 0 if the device doesn't match and non-zero
 391 * if it does.  If the callback returns non-zero, this function will
 392 * return to the caller and not iterate over any more devices.
 393 *
 394 * Note, you will need to drop the reference with put_device() after use.
 395 *
 396 * @match is allowed to do anything including calling back into class
 397 * code.  There's no locking restriction.
 398 */
 399struct device *class_find_device(struct class *class, struct device *start,
 400                                 const void *data,
 401                                 int (*match)(struct device *, const void *))
 402{
 403        struct class_dev_iter iter;
 404        struct device *dev;
 405
 406        if (!class)
 407                return NULL;
 408        if (!class->p) {
 409                WARN(1, "%s called for class '%s' before it was initialized",
 410                     __func__, class->name);
 411                return NULL;
 412        }
 413
 414        class_dev_iter_init(&iter, class, start, NULL);
 415        while ((dev = class_dev_iter_next(&iter))) {
 416                if (match(dev, data)) {
 417                        get_device(dev);
 418                        break;
 419                }
 420        }
 421        class_dev_iter_exit(&iter);
 422
 423        return dev;
 424}
 425EXPORT_SYMBOL_GPL(class_find_device);
 426
 427int class_interface_register(struct class_interface *class_intf)
 428{
 429        struct class *parent;
 430        struct class_dev_iter iter;
 431        struct device *dev;
 432
 433        if (!class_intf || !class_intf->class)
 434                return -ENODEV;
 435
 436        parent = class_get(class_intf->class);
 437        if (!parent)
 438                return -EINVAL;
 439
 440        mutex_lock(&parent->p->mutex);
 441        list_add_tail(&class_intf->node, &parent->p->interfaces);
 442        if (class_intf->add_dev) {
 443                class_dev_iter_init(&iter, parent, NULL, NULL);
 444                while ((dev = class_dev_iter_next(&iter)))
 445                        class_intf->add_dev(dev, class_intf);
 446                class_dev_iter_exit(&iter);
 447        }
 448        mutex_unlock(&parent->p->mutex);
 449
 450        return 0;
 451}
 452
 453void class_interface_unregister(struct class_interface *class_intf)
 454{
 455        struct class *parent = class_intf->class;
 456        struct class_dev_iter iter;
 457        struct device *dev;
 458
 459        if (!parent)
 460                return;
 461
 462        mutex_lock(&parent->p->mutex);
 463        list_del_init(&class_intf->node);
 464        if (class_intf->remove_dev) {
 465                class_dev_iter_init(&iter, parent, NULL, NULL);
 466                while ((dev = class_dev_iter_next(&iter)))
 467                        class_intf->remove_dev(dev, class_intf);
 468                class_dev_iter_exit(&iter);
 469        }
 470        mutex_unlock(&parent->p->mutex);
 471
 472        class_put(parent);
 473}
 474
 475ssize_t show_class_attr_string(struct class *class,
 476                               struct class_attribute *attr, char *buf)
 477{
 478        struct class_attribute_string *cs;
 479
 480        cs = container_of(attr, struct class_attribute_string, attr);
 481        return snprintf(buf, PAGE_SIZE, "%s\n", cs->str);
 482}
 483
 484EXPORT_SYMBOL_GPL(show_class_attr_string);
 485
 486struct class_compat {
 487        struct kobject *kobj;
 488};
 489
 490/**
 491 * class_compat_register - register a compatibility class
 492 * @name: the name of the class
 493 *
 494 * Compatibility class are meant as a temporary user-space compatibility
 495 * workaround when converting a family of class devices to a bus devices.
 496 */
 497struct class_compat *class_compat_register(const char *name)
 498{
 499        struct class_compat *cls;
 500
 501        cls = kmalloc(sizeof(struct class_compat), GFP_KERNEL);
 502        if (!cls)
 503                return NULL;
 504        cls->kobj = kobject_create_and_add(name, &class_kset->kobj);
 505        if (!cls->kobj) {
 506                kfree(cls);
 507                return NULL;
 508        }
 509        return cls;
 510}
 511EXPORT_SYMBOL_GPL(class_compat_register);
 512
 513/**
 514 * class_compat_unregister - unregister a compatibility class
 515 * @cls: the class to unregister
 516 */
 517void class_compat_unregister(struct class_compat *cls)
 518{
 519        kobject_put(cls->kobj);
 520        kfree(cls);
 521}
 522EXPORT_SYMBOL_GPL(class_compat_unregister);
 523
 524/**
 525 * class_compat_create_link - create a compatibility class device link to
 526 *                            a bus device
 527 * @cls: the compatibility class
 528 * @dev: the target bus device
 529 * @device_link: an optional device to which a "device" link should be created
 530 */
 531int class_compat_create_link(struct class_compat *cls, struct device *dev,
 532                             struct device *device_link)
 533{
 534        int error;
 535
 536        error = sysfs_create_link(cls->kobj, &dev->kobj, dev_name(dev));
 537        if (error)
 538                return error;
 539
 540        /*
 541         * Optionally add a "device" link (typically to the parent), as a
 542         * class device would have one and we want to provide as much
 543         * backwards compatibility as possible.
 544         */
 545        if (device_link) {
 546                error = sysfs_create_link(&dev->kobj, &device_link->kobj,
 547                                          "device");
 548                if (error)
 549                        sysfs_remove_link(cls->kobj, dev_name(dev));
 550        }
 551
 552        return error;
 553}
 554EXPORT_SYMBOL_GPL(class_compat_create_link);
 555
 556/**
 557 * class_compat_remove_link - remove a compatibility class device link to
 558 *                            a bus device
 559 * @cls: the compatibility class
 560 * @dev: the target bus device
 561 * @device_link: an optional device to which a "device" link was previously
 562 *               created
 563 */
 564void class_compat_remove_link(struct class_compat *cls, struct device *dev,
 565                              struct device *device_link)
 566{
 567        if (device_link)
 568                sysfs_remove_link(&dev->kobj, "device");
 569        sysfs_remove_link(cls->kobj, dev_name(dev));
 570}
 571EXPORT_SYMBOL_GPL(class_compat_remove_link);
 572
 573int __init classes_init(void)
 574{
 575        class_kset = kset_create_and_add("class", NULL, NULL);
 576        if (!class_kset)
 577                return -ENOMEM;
 578        return 0;
 579}
 580
 581EXPORT_SYMBOL_GPL(class_create_file_ns);
 582EXPORT_SYMBOL_GPL(class_remove_file_ns);
 583EXPORT_SYMBOL_GPL(class_unregister);
 584EXPORT_SYMBOL_GPL(class_destroy);
 585
 586EXPORT_SYMBOL_GPL(class_interface_register);
 587EXPORT_SYMBOL_GPL(class_interface_unregister);
 588