drivers/base/class.c

   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
  25 static 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
  37 static 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
  49 static 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
  65 static 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
  73 static const struct sysfs_ops class_sysfs_ops = {
  74         .show      = class_attr_show,
  75         .store     = class_attr_store,
  76 };
  77
  78 static 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 */
  85 static struct kset *class_kset;
  86
  87
  88 int 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
 101 void 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
 108 static struct class *class_get(struct class *cls)
 109 {
 110         if (cls)
 111                 kset_get(&cls->p->subsys);
 112         return cls;
 113 }
 114
 115 static void class_put(struct class *cls)
 116 {
 117         if (cls)
 118                 kset_put(&cls->p->subsys);
 119 }
 120
 121 static 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
 127 static 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
 134 static 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
 141 static 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
 147 static 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
 153 int __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 }
 197 EXPORT_SYMBOL_GPL(__class_register);
 198
 199 void 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
 206 static 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  */
 226 struct 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
 248 error:
 249         kfree(cls);
 250         return ERR_PTR(retval);
 251 }
 252 EXPORT_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  */
 261 void 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  */
 281 void 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 }
 291 EXPORT_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  */
 305 struct 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 }
 319 EXPORT_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  */
 328 void class_dev_iter_exit(struct class_dev_iter *iter)
 329 {
 330         klist_iter_exit(&iter->ki);
 331 }
 332 EXPORT_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  */
 352 int 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 }
 377 EXPORT_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  */
 399 struct 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 }
 425 EXPORT_SYMBOL_GPL(class_find_device);
 426
 427 int 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
 453 void 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
 475 ssize_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
 484 EXPORT_SYMBOL_GPL(show_class_attr_string);
 485
 486 struct 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  */
 497 struct 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 }
 511 EXPORT_SYMBOL_GPL(class_compat_register);
 512
 513 /**
 514  * class_compat_unregister - unregister a compatibility class
 515  * @cls: the class to unregister
 516  */
 517 void class_compat_unregister(struct class_compat *cls)
 518 {
 519         kobject_put(cls->kobj);
 520         kfree(cls);
 521 }
 522 EXPORT_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  */
 531 int 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 }
 554 EXPORT_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  */
 564 void 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 }
 571 EXPORT_SYMBOL_GPL(class_compat_remove_link);
 572
 573 int __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
 581 EXPORT_SYMBOL_GPL(class_create_file_ns);
 582 EXPORT_SYMBOL_GPL(class_remove_file_ns);
 583 EXPORT_SYMBOL_GPL(class_unregister);
 584 EXPORT_SYMBOL_GPL(class_destroy);
 585
 586 EXPORT_SYMBOL_GPL(class_interface_register);
 587 EXPORT_SYMBOL_GPL(class_interface_unregister);