class_create函數跟蹤：

/* This is a #define to keep the compiler from merging different
?* instances of the __key variable */
#define class_create(owner, name) \
({ \
static struct lock_class_key __key;\
__class_create(owner, name, &__key);\
})

/**
?* class_create - create a struct class structure
?* @owner: pointer to the module that is to "own" this struct class
?* @name: pointer to a string for the name of this class.
?* @key: the lock_class_key for this class; used by mutex lock debugging
?*
?* This is used to create a struct class pointer that can then be used
?* in calls to device_create().
?*
?* Returns &struct class pointer on success, or ERR_PTR() on error.
?*
?* Note, the pointer created here is to be destroyed when finished by
?* making a call to class_destroy().
?*/
struct class *__class_create(struct module *owner, const char *name,
? ? struct lock_class_key *key)
{
struct class *cls;
int retval;


cls = kzalloc(sizeof(*cls), GFP_KERNEL);
if (!cls) {
retval = -ENOMEM;
goto error;
}


cls->name = name;
cls->owner = owner;
cls->class_release = class_create_release;


retval = __class_register(cls, key);
if (retval)
goto error;


return cls;


error:
kfree(cls);
return ERR_PTR(retval);
}
EXPORT_SYMBOL_GPL(__class_create);

static void class_create_release(struct class *cls)
{
pr_debug("%s called for %s\n", __func__, cls->name);
kfree(cls);
}

int __class_register(struct class *cls, struct lock_class_key *key)
{
struct subsys_private *cp;
int error;


pr_debug("device class '%s': registering\n", cls->name);


cp = kzalloc(sizeof(*cp), GFP_KERNEL);
if (!cp)
return -ENOMEM;
klist_init(&cp->klist_devices, klist_class_dev_get, klist_class_dev_put);
INIT_LIST_HEAD(&cp->interfaces);
kset_init(&cp->glue_dirs);
__mutex_init(&cp->mutex, "subsys mutex", key);
error = kobject_set_name(&cp->subsys.kobj, "%s", cls->name);
if (error) {
kfree(cp);
return error;
}


/* set the default /sys/dev directory for devices of this class */
if (!cls->dev_kobj)
cls->dev_kobj = sysfs_dev_char_kobj;


#if defined(CONFIG_BLOCK)
/* let the block class directory show up in the root of sysfs */
if (!sysfs_deprecated || cls != &block_class)
cp->subsys.kobj.kset = class_kset;
#else
cp->subsys.kobj.kset = class_kset;
#endif
cp->subsys.kobj.ktype = &class_ktype;
cp->class = cls;
cls->p = cp;


error = kset_register(&cp->subsys);
if (error) {
kfree(cp);
return error;
}
error = add_class_attrs(class_get(cls));
class_put(cls);
return error;
}
EXPORT_SYMBOL_GPL(__class_register);

先跟蹤3層，不能再多了。

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