root/drivers/base/class.c

DEFINITIONS

1. class_attr_show
2. class_attr_store
3. class_release
4. class_child_ns_type
5. class_create_file_ns
6. class_remove_file_ns
7. class_get
8. class_put
9. klist_class_to_dev
10. klist_class_dev_get
11. klist_class_dev_put
12. class_add_groups
13. class_remove_groups
14. __class_register
15. class_unregister
16. class_create_release
17. __class_create
18. class_destroy
19. class_dev_iter_init
20. class_dev_iter_next
21. class_dev_iter_exit
22. class_for_each_device
23. class_find_device
24. class_interface_register
25. class_interface_unregister
26. show_class_attr_string
27. class_compat_register
28. class_compat_unregister
29. class_compat_create_link
30. class_compat_remove_link
31. classes_init

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