最近做linux驅動，遇到了個問題，由於linux版本變化太快和資料更新慢，有些函數發生變化，其中udev動態創建設備節點的函數也發生變化
在linux2.6某個版本之後 devfs不復存在，udev成爲devfs的替代，可以用udev在/dev/下動態生成設備文件，其中2.6之後不同版本創建函數也不同，
在linux2.6.13之前的是
class_simple_create 創建 class
class_simple_destroy 銷燬 class
calss_simple_device_add 創建device
calss_simple_device_remove 銷燬device
在linux2.6.13之後的是
class_create 創建 class
class_destroy 銷燬 class
calss_device_create 創建device
calss_device_destroy 銷燬device
在linux2.6.35之中的是
class_create 創建 class
device_create 創建device
class_destroy 銷燬 class
device_destroy 銷燬device
上述這些都是在linux中的device.h中定義的，所以頭文件要包括#include <linux/device.h>
其大致用法如下
struct class *myclass ；
class_create(THIS_MODULE, “my_device_driver”);
device_create(myclass, NULL, MKDEV(major_num, minor_num), NULL, “my_device”);
在linux中的定義如下
Class結構體
在2.6.35內核版本中，struct class定義在頭文件include/linux/device.h中
/*
* device classes
*/
struct class {
const char *name;
struct module *owner;
struct class_attribute *class_attrs;
struct device_attribute *dev_attrs;
struct kobject *dev_kobj;
int (*dev_uevent)(struct device *dev, struct kobj_uevent_env *env);
char *(*devnode)(struct device *dev, mode_t *mode);
void (*class_release)(struct class *class);
void (*dev_release)(struct device *dev);
int (*suspend)(struct device *dev, pm_message_t state);
int (*resume)(struct device *dev);
const struct kobj_ns_type_operations *ns_type;
const void *(*namespace)(struct device *dev);
const struct dev_pm_ops *pm;
struct class_private *p;
};
class_create(…)在/drivers/base/class.c中實現：
/**
* 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.
;*
* This is used to create a struct class pointer that can then be used
* in calls to device_create().
* http://www.jybase.net
* 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);
}
第一個參數指定類的所有者是哪個模塊，第二個參數指定類名。
在class.c中，還定義了class_destroy(…)函數，用於在模塊卸載時刪除類，起到相反的作用。
device_create(…)函數在/drivers/base/core.c中實現：
/**
* device_create - creates a device and registers it with sysfs
* @class: pointer to the struct class that this device should be registered to
* @parent: pointer to the parent struct device of this new device, if any
* @devt: the dev_t for the char device to be added
* @fmt: string for the device's name
*
* This function can be used by char device classes. A struct device
* will be created in sysfs, registered to the specified class.
*
* A "dev" file will be created, showing the dev_t for the device, if
* the dev_t is not 0,0.
* If a pointer to a parent struct device is passed in, the newly created
* struct device will be a child of that device in sysfs.
* The pointer to the struct device will be returned from the call.
* Any further sysfs files that might be required can be created using this
* pointer.
*
* Note: the struct class passed to this function must have previously
* been created with a call to class_create().
*/
struct device *device_create(struct class *class, struct device *parent, dev_t devt, void *drvdata, const char *fmt, ...)
{
va_list vargs;
struct device *dev;
va_start(vargs, fmt);
dev = device_create_vargs(class, parent, devt, drvdata, fmt, vargs);
va_end(vargs);
return dev;
}
第一個參數指定所要創建的設備所從屬的類，第二個參數是這個設備的父設備，如果沒有就指定爲NULL，第三個參數是設備號，第四個參數是設備名稱，第五個參數是從設備號。