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Linux/drivers/base/class.c

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

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