Linux驱动中自动创建节点

自学驱动以来,一直都是在加载模块后采用手动创建节点,虽然这个过程比较简单,毕竟还是有点麻烦,尤其是在调试模块的时候。
#insmod module_name.ko
#mknod /dev/module_name c MAJOR MINOR
#
在2.4里设备文件采用的是devfs,在2.6里已经用udev取代devfs,为解决上面那样手动创建节点的麻烦,我们可以在程序里加上创建节点这项,如下:
以字符设备char_dev为例,在驱动初始化的代码里调用class_create为该设备创建一个class,再为每个设备调用 class_device_create创建对应的设备,这样的module被加载时,undev daemon就会自动在/dev下创建char_dev设备文件。大概方法如下:
struct class *myclass = class_create(THIS_MODULE, “char_dev”);
class_device_create(myclass, NULL, MKDEV(major_num, 0), NULL, “char_dev”);

当然,在exit函数中要把创建的class移除:
class_destory(&xxx_dev->cdev);
class_device_desotry(my_class,MKDEV(major_num,0));

下面介绍下函数class_creat和class_device_creat的原型:
class_create()
-------------------------------------------------
linux-2.6.22/include/linux/device.h
struct class *class_create(struct module *owner, const char *name)
    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.
在/sys/class/下创建类目录


class_device_create()
-------------------------------------------------
linux-2.6.22/include/linux/device.h
struct class_device *class_device_creat
(struct class        *cls,
                                         struct class_device *parent,
                                         dev_t               devt,
                                         struct device       *device,
                                         const char          *fmt, ...)

    class_device_create - creates a class device and registers it with sysfs
    @cls: pointer to the struct class that this device should be registered to.
    @parent: pointer to the parent struct class_device of this new device, if any.
    @devt: the dev_t for the char device to be added.
    @device: a pointer to a struct device that is assiociated with this class device.
    @fmt: string for the class device's name
void class_destroy(struct class *cls);/*销毁/sys/class下的类   */
void class_device_destroy(struct class *cls, dev_t devt);   /*销毁 一个类设备*/
参数含义同上
补充:
在Linux2.6中,针对上面的这个问题不同的版本有些修改,使用前要先查看下/.../include/linux/device.h里的函数声明,如我用的是Linux2.6.29,里面就没有 class_device_create函数,而直接使用device_create就可以了,而在之前的版本如Linux2.6.15,里面就要用class_device_create函数

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转载自blog.csdn.net/zwz_home/article/details/7712086
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