Root/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
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                 const void *data,
424                 int (*match)(struct device *, const 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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