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 subsys_private *cp = to_subsys_private(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 subsys_private *cp = to_subsys_private(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 const void *class_attr_namespace(struct kobject *kobj,
  51                                        const struct attribute *attr)
  52{
  53        struct class_attribute *class_attr = to_class_attr(attr);
  54        struct subsys_private *cp = to_subsys_private(kobj);
  55        const void *ns = NULL;
  56
  57        if (class_attr->namespace)
  58                ns = class_attr->namespace(cp->class, class_attr);
  59        return ns;
  60}
  61
  62static void class_release(struct kobject *kobj)
  63{
  64        struct subsys_private *cp = to_subsys_private(kobj);
  65        struct class *class = cp->class;
  66
  67        pr_debug("class '%s': release.\n", class->name);
  68
  69        if (class->class_release)
  70                class->class_release(class);
  71        else
  72                pr_debug("class '%s' does not have a release() function, "
  73                         "be careful\n", class->name);
  74
  75        kfree(cp);
  76}
  77
  78static const struct kobj_ns_type_operations *class_child_ns_type(struct kobject *kobj)
  79{
  80        struct subsys_private *cp = to_subsys_private(kobj);
  81        struct class *class = cp->class;
  82
  83        return class->ns_type;
  84}
  85
  86static const struct sysfs_ops class_sysfs_ops = {
  87        .show      = class_attr_show,
  88        .store     = class_attr_store,
  89        .namespace = class_attr_namespace,
  90};
  91
  92static struct kobj_type class_ktype = {
  93        .sysfs_ops      = &class_sysfs_ops,
  94        .release        = class_release,
  95        .child_ns_type  = class_child_ns_type,
  96};
  97
  98/* Hotplug events for classes go to the class subsys */
  99static struct kset *class_kset;
 100
 101
 102int class_create_file(struct class *cls, const struct class_attribute *attr)
 103{
 104        int error;
 105        if (cls)
 106                error = sysfs_create_file(&cls->p->subsys.kobj,
 107                                          &attr->attr);
 108        else
 109                error = -EINVAL;
 110        return error;
 111}
 112
 113void class_remove_file(struct class *cls, const struct class_attribute *attr)
 114{
 115        if (cls)
 116                sysfs_remove_file(&cls->p->subsys.kobj, &attr->attr);
 117}
 118
 119static struct class *class_get(struct class *cls)
 120{
 121        if (cls)
 122                kset_get(&cls->p->subsys);
 123        return cls;
 124}
 125
 126static void class_put(struct class *cls)
 127{
 128        if (cls)
 129                kset_put(&cls->p->subsys);
 130}
 131
 132static int add_class_attrs(struct class *cls)
 133{
 134        int i;
 135        int error = 0;
 136
 137        if (cls->class_attrs) {
 138                for (i = 0; attr_name(cls->class_attrs[i]); i++) {
 139                        error = class_create_file(cls, &cls->class_attrs[i]);
 140                        if (error)
 141                                goto error;
 142                }
 143        }
 144done:
 145        return error;
 146error:
 147        while (--i >= 0)
 148                class_remove_file(cls, &cls->class_attrs[i]);
 149        goto done;
 150}
 151
 152static void remove_class_attrs(struct class *cls)
 153{
 154        int i;
 155
 156        if (cls->class_attrs) {
 157                for (i = 0; attr_name(cls->class_attrs[i]); i++)
 158                        class_remove_file(cls, &cls->class_attrs[i]);
 159        }
 160}
 161
 162static void klist_class_dev_get(struct klist_node *n)
 163{
 164        struct device *dev = container_of(n, struct device, knode_class);
 165
 166        get_device(dev);
 167}
 168
 169static void klist_class_dev_put(struct klist_node *n)
 170{
 171        struct device *dev = container_of(n, struct device, knode_class);
 172
 173        put_device(dev);
 174}
 175
 176int __class_register(struct class *cls, struct lock_class_key *key)
 177{
 178        struct subsys_private *cp;
 179        int error;
 180
 181        pr_debug("device class '%s': registering\n", cls->name);
 182
 183        cp = kzalloc(sizeof(*cp), GFP_KERNEL);
 184        if (!cp)
 185                return -ENOMEM;
 186        klist_init(&cp->klist_devices, klist_class_dev_get, klist_class_dev_put);
 187        INIT_LIST_HEAD(&cp->interfaces);
 188        kset_init(&cp->glue_dirs);
 189        __mutex_init(&cp->mutex, "subsys mutex", key);
 190        error = kobject_set_name(&cp->subsys.kobj, "%s", cls->name);
 191        if (error) {
 192                kfree(cp);
 193                return error;
 194        }
 195
 196        /* set the default /sys/dev directory for devices of this class */
 197        if (!cls->dev_kobj)
 198                cls->dev_kobj = sysfs_dev_char_kobj;
 199
 200#if defined(CONFIG_BLOCK)
 201        /* let the block class directory show up in the root of sysfs */
 202        if (!sysfs_deprecated || cls != &block_class)
 203                cp->subsys.kobj.kset = class_kset;
 204#else
 205        cp->subsys.kobj.kset = class_kset;
 206#endif
 207        cp->subsys.kobj.ktype = &class_ktype;
 208        cp->class = cls;
 209        cls->p = cp;
 210
 211        error = kset_register(&cp->subsys);
 212        if (error) {
 213                kfree(cp);
 214                return error;
 215        }
 216        error = add_class_attrs(class_get(cls));
 217        class_put(cls);
 218        return error;
 219}
 220EXPORT_SYMBOL_GPL(__class_register);
 221
 222void class_unregister(struct class *cls)
 223{
 224        pr_debug("device class '%s': unregistering\n", cls->name);
 225        remove_class_attrs(cls);
 226        kset_unregister(&cls->p->subsys);
 227}
 228
 229static void class_create_release(struct class *cls)
 230{
 231        pr_debug("%s called for %s\n", __func__, cls->name);
 232        kfree(cls);
 233}
 234
 235/**
 236 * class_create - create a struct class structure
 237 * @owner: pointer to the module that is to "own" this struct class
 238 * @name: pointer to a string for the name of this class.
 239 * @key: the lock_class_key for this class; used by mutex lock debugging
 240 *
 241 * This is used to create a struct class pointer that can then be used
 242 * in calls to device_create().
 243 *
 244 * Returns &struct class pointer on success, or ERR_PTR() on error.
 245 *
 246 * Note, the pointer created here is to be destroyed when finished by
 247 * making a call to class_destroy().
 248 */
 249struct class *__class_create(struct module *owner, const char *name,
 250                             struct lock_class_key *key)
 251{
 252        struct class *cls;
 253        int retval;
 254
 255        cls = kzalloc(sizeof(*cls), GFP_KERNEL);
 256        if (!cls) {
 257                retval = -ENOMEM;
 258                goto error;
 259        }
 260
 261        cls->name = name;
 262        cls->owner = owner;
 263        cls->class_release = class_create_release;
 264
 265        retval = __class_register(cls, key);
 266        if (retval)
 267                goto error;
 268
 269        return cls;
 270
 271error:
 272        kfree(cls);
 273        return ERR_PTR(retval);
 274}
 275EXPORT_SYMBOL_GPL(__class_create);
 276
 277/**
 278 * class_destroy - destroys a struct class structure
 279 * @cls: pointer to the struct class that is to be destroyed
 280 *
 281 * Note, the pointer to be destroyed must have been created with a call
 282 * to class_create().
 283 */
 284void class_destroy(struct class *cls)
 285{
 286        if ((cls == NULL) || (IS_ERR(cls)))
 287                return;
 288
 289        class_unregister(cls);
 290}
 291
 292/**
 293 * class_dev_iter_init - initialize class device iterator
 294 * @iter: class iterator to initialize
 295 * @class: the class we wanna iterate over
 296 * @start: the device to start iterating from, if any
 297 * @type: device_type of the devices to iterate over, NULL for all
 298 *
 299 * Initialize class iterator @iter such that it iterates over devices
 300 * of @class.  If @start is set, the list iteration will start there,
 301 * otherwise if it is NULL, the iteration starts at the beginning of
 302 * the list.
 303 */
 304void class_dev_iter_init(struct class_dev_iter *iter, struct class *class,
 305                         struct device *start, const struct device_type *type)
 306{
 307        struct klist_node *start_knode = NULL;
 308
 309        if (start)
 310                start_knode = &start->knode_class;
 311        klist_iter_init_node(&class->p->klist_devices, &iter->ki, start_knode);
 312        iter->type = type;
 313}
 314EXPORT_SYMBOL_GPL(class_dev_iter_init);
 315
 316/**
 317 * class_dev_iter_next - iterate to the next device
 318 * @iter: class iterator to proceed
 319 *
 320 * Proceed @iter to the next device and return it.  Returns NULL if
 321 * iteration is complete.
 322 *
 323 * The returned device is referenced and won't be released till
 324 * iterator is proceed to the next device or exited.  The caller is
 325 * free to do whatever it wants to do with the device including
 326 * calling back into class code.
 327 */
 328struct device *class_dev_iter_next(struct class_dev_iter *iter)
 329{
 330        struct klist_node *knode;
 331        struct device *dev;
 332
 333        while (1) {
 334                knode = klist_next(&iter->ki);
 335                if (!knode)
 336                        return NULL;
 337                dev = container_of(knode, struct device, knode_class);
 338                if (!iter->type || iter->type == dev->type)
 339                        return dev;
 340        }
 341}
 342EXPORT_SYMBOL_GPL(class_dev_iter_next);
 343
 344/**
 345 * class_dev_iter_exit - finish iteration
 346 * @iter: class iterator to finish
 347 *
 348 * Finish an iteration.  Always call this function after iteration is
 349 * complete whether the iteration ran till the end or not.
 350 */
 351void class_dev_iter_exit(struct class_dev_iter *iter)
 352{
 353        klist_iter_exit(&iter->ki);
 354}
 355EXPORT_SYMBOL_GPL(class_dev_iter_exit);
 356
 357/**
 358 * class_for_each_device - device iterator
 359 * @class: the class we're iterating
 360 * @start: the device to start with in the list, if any.
 361 * @data: data for the callback
 362 * @fn: function to be called for each device
 363 *
 364 * Iterate over @class's list of devices, and call @fn for each,
 365 * passing it @data.  If @start is set, the list iteration will start
 366 * there, otherwise if it is NULL, the iteration starts at the
 367 * beginning of the list.
 368 *
 369 * We check the return of @fn each time. If it returns anything
 370 * other than 0, we break out and return that value.
 371 *
 372 * @fn is allowed to do anything including calling back into class
 373 * code.  There's no locking restriction.
 374 */
 375int class_for_each_device(struct class *class, struct device *start,
 376                          void *data, int (*fn)(struct device *, void *))
 377{
 378        struct class_dev_iter iter;
 379        struct device *dev;
 380        int error = 0;
 381
 382        if (!class)
 383                return -EINVAL;
 384        if (!class->p) {
 385                WARN(1, "%s called for class '%s' before it was initialized",
 386                     __func__, class->name);
 387                return -EINVAL;
 388        }
 389
 390        class_dev_iter_init(&iter, class, start, NULL);
 391        while ((dev = class_dev_iter_next(&iter))) {
 392                error = fn(dev, data);
 393                if (error)
 394                        break;
 395        }
 396        class_dev_iter_exit(&iter);
 397
 398        return error;
 399}
 400EXPORT_SYMBOL_GPL(class_for_each_device);
 401
 402/**
 403 * class_find_device - device iterator for locating a particular device
 404 * @class: the class we're iterating
 405 * @start: Device to begin with
 406 * @data: data for the match function
 407 * @match: function to check device
 408 *
 409 * This is similar to the class_for_each_dev() function above, but it
 410 * returns a reference to a device that is 'found' for later use, as
 411 * determined by the @match callback.
 412 *
 413 * The callback should return 0 if the device doesn't match and non-zero
 414 * if it does.  If the callback returns non-zero, this function will
 415 * return to the caller and not iterate over any more devices.
 416 *
 417 * Note, you will need to drop the reference with put_device() after use.
 418 *
 419 * @fn is allowed to do anything including calling back into class
 420 * code.  There's no locking restriction.
 421 */
 422struct device *class_find_device(struct class *class, struct device *start,
 423                                 void *data,
 424                                 int (*match)(struct device *, void *))
 425{
 426        struct class_dev_iter iter;
 427        struct device *dev;
 428
 429        if (!class)
 430                return NULL;
 431        if (!class->p) {
 432                WARN(1, "%s called for class '%s' before it was initialized",
 433                     __func__, class->name);
 434                return NULL;
 435        }
 436
 437        class_dev_iter_init(&iter, class, start, NULL);
 438        while ((dev = class_dev_iter_next(&iter))) {
 439                if (match(dev, data)) {
 440                        get_device(dev);
 441                        break;
 442                }
 443        }
 444        class_dev_iter_exit(&iter);
 445
 446        return dev;
 447}
 448EXPORT_SYMBOL_GPL(class_find_device);
 449
 450int class_interface_register(struct class_interface *class_intf)
 451{
 452        struct class *parent;
 453        struct class_dev_iter iter;
 454        struct device *dev;
 455
 456        if (!class_intf || !class_intf->class)
 457                return -ENODEV;
 458
 459        parent = class_get(class_intf->class);
 460        if (!parent)
 461                return -EINVAL;
 462
 463        mutex_lock(&parent->p->mutex);
 464        list_add_tail(&class_intf->node, &parent->p->interfaces);
 465        if (class_intf->add_dev) {
 466                class_dev_iter_init(&iter, parent, NULL, NULL);
 467                while ((dev = class_dev_iter_next(&iter)))
 468                        class_intf->add_dev(dev, class_intf);
 469                class_dev_iter_exit(&iter);
 470        }
 471        mutex_unlock(&parent->p->mutex);
 472
 473        return 0;
 474}
 475
 476void class_interface_unregister(struct class_interface *class_intf)
 477{
 478        struct class *parent = class_intf->class;
 479        struct class_dev_iter iter;
 480        struct device *dev;
 481
 482        if (!parent)
 483                return;
 484
 485        mutex_lock(&parent->p->mutex);
 486        list_del_init(&class_intf->node);
 487        if (class_intf->remove_dev) {
 488                class_dev_iter_init(&iter, parent, NULL, NULL);
 489                while ((dev = class_dev_iter_next(&iter)))
 490                        class_intf->remove_dev(dev, class_intf);
 491                class_dev_iter_exit(&iter);
 492        }
 493        mutex_unlock(&parent->p->mutex);
 494
 495        class_put(parent);
 496}
 497
 498ssize_t show_class_attr_string(struct class *class,
 499                               struct class_attribute *attr, char *buf)
 500{
 501        struct class_attribute_string *cs;
 502        cs = container_of(attr, struct class_attribute_string, attr);
 503        return snprintf(buf, PAGE_SIZE, "%s\n", cs->str);
 504}
 505
 506EXPORT_SYMBOL_GPL(show_class_attr_string);
 507
 508struct class_compat {
 509        struct kobject *kobj;
 510};
 511
 512/**
 513 * class_compat_register - register a compatibility class
 514 * @name: the name of the class
 515 *
 516 * Compatibility class are meant as a temporary user-space compatibility
 517 * workaround when converting a family of class devices to a bus devices.
 518 */
 519struct class_compat *class_compat_register(const char *name)
 520{
 521        struct class_compat *cls;
 522
 523        cls = kmalloc(sizeof(struct class_compat), GFP_KERNEL);
 524        if (!cls)
 525                return NULL;
 526        cls->kobj = kobject_create_and_add(name, &class_kset->kobj);
 527        if (!cls->kobj) {
 528                kfree(cls);
 529                return NULL;
 530        }
 531        return cls;
 532}
 533EXPORT_SYMBOL_GPL(class_compat_register);
 534
 535/**
 536 * class_compat_unregister - unregister a compatibility class
 537 * @cls: the class to unregister
 538 */
 539void class_compat_unregister(struct class_compat *cls)
 540{
 541        kobject_put(cls->kobj);
 542        kfree(cls);
 543}
 544EXPORT_SYMBOL_GPL(class_compat_unregister);
 545
 546/**
 547 * class_compat_create_link - create a compatibility class device link to
 548 *                            a bus device
 549 * @cls: the compatibility class
 550 * @dev: the target bus device
 551 * @device_link: an optional device to which a "device" link should be created
 552 */
 553int class_compat_create_link(struct class_compat *cls, struct device *dev,
 554                             struct device *device_link)
 555{
 556        int error;
 557
 558        error = sysfs_create_link(cls->kobj, &dev->kobj, dev_name(dev));
 559        if (error)
 560                return error;
 561
 562        /*
 563         * Optionally add a "device" link (typically to the parent), as a
 564         * class device would have one and we want to provide as much
 565         * backwards compatibility as possible.
 566         */
 567        if (device_link) {
 568                error = sysfs_create_link(&dev->kobj, &device_link->kobj,
 569                                          "device");
 570                if (error)
 571                        sysfs_remove_link(cls->kobj, dev_name(dev));
 572        }
 573
 574        return error;
 575}
 576EXPORT_SYMBOL_GPL(class_compat_create_link);
 577
 578/**
 579 * class_compat_remove_link - remove a compatibility class device link to
 580 *                            a bus device
 581 * @cls: the compatibility class
 582 * @dev: the target bus device
 583 * @device_link: an optional device to which a "device" link was previously
 584 *               created
 585 */
 586void class_compat_remove_link(struct class_compat *cls, struct device *dev,
 587                              struct device *device_link)
 588{
 589        if (device_link)
 590                sysfs_remove_link(&dev->kobj, "device");
 591        sysfs_remove_link(cls->kobj, dev_name(dev));
 592}
 593EXPORT_SYMBOL_GPL(class_compat_remove_link);
 594
 595int __init classes_init(void)
 596{
 597        class_kset = kset_create_and_add("class", NULL, NULL);
 598        if (!class_kset)
 599                return -ENOMEM;
 600        return 0;
 601}
 602
 603EXPORT_SYMBOL_GPL(class_create_file);
 604EXPORT_SYMBOL_GPL(class_remove_file);
 605EXPORT_SYMBOL_GPL(class_unregister);
 606EXPORT_SYMBOL_GPL(class_destroy);
 607
 608EXPORT_SYMBOL_GPL(class_interface_register);
 609EXPORT_SYMBOL_GPL(class_interface_unregister);
 610
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