Linux驱动之设备模型(7)

Linux驱动之设备模型(7)

  (2013-02-21 11:15:33)

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标签：  linux   设备模型

分类： 设备模型

原文地址：   http://blog.youkuaiyun.com/hsly_support/article/details/7366602

8．类

8.1  class

l  Class是对设备按照功能进行的分类，这样做是为了给用户空间提供一个比较友好的界面。Class也是一个kset，对应于/sys/class下的一个目录

int  __init  classes_init(void)

{

        

         class_kset =kset_create_and_add("class", NULL, NULL);

         if (!class_kset)

                   return -ENOMEM;

         return 0;

}

 

l  在设备模型中类由class结构表示

struct class {

         const char                  *name;         

         struct module           *owner;

 

         struct class_attribute               *class_attrs;

         struct device_attribute            *dev_attrs; 

         struct bin_attribute                   *dev_bin_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); 

 

                  

         const struct dev_pm_ops *pm;

 

        

         struct subsys_private *p;

};

 

8.2    Class属性

l  Class属性用class_attribute来表示

struct  class_attribute {

         struct attribute attr;

         ssize_t (*show)(struct class *class,struct class_attribute *attr,

                            char *buf);

         ssize_t (*store)(struct class *class,struct class_attribute *attr,

                            const char *buf,size_t count);

};                                    

CLASS_ATTR(_name,_mode, _show, _store)

l  属性操作

int   __must_checkclass_create_file(struct class *class,

                                                 const struct class_attribute *attr);

void  class_remove_file(struct class *class,

                                  const struct class_attribute *attr);

 

8.3    Class基本操作

l  class注册和注销

    int  class_register(struct class *class);

    void  class_unregister(struct class *class);

 

l  class创建和销毁

    struct   class *  class_create(struct module *owner, const char *name)

    void  class_destroy(struct class *cls);

        

l  向类添加设备和删除设备

struct device  * device_create(struct class *class, struct device *parent,

                                 dev_t devt, void *drvdata, const char*fmt, ...)

         void  device_destroy(struct class *class, dev_t devt)

         devt：设备号

 

8.4  实例解析

 

#include

#include

#include

#include

 

static char  * Version = "revision 1.0,scclass";

 

 

struct  class  * scclass;

EXPORT_SYMBOL_GPL(scclass);

 

 

static  ssize_t  class_show_version(structclass *class,

                                     structclass_attribute *attr, char *buf)

{

         return  sprintf(buf, "%s\n", Version);

}

CLASS_ATTR(version, 0666,class_show_version, NULL);

 

static  int  __init  scclass_init(void)

{

         int  err;

 

        

         scclass= class_create(THIS_MODULE, "scclass");

         err= PTR_ERR(scclass);

         if(IS_ERR(scclass))

                   return  err;

        

         err= class_create_file(scclass, &class_attr_version);

         if(err)

                   goto  err_class_create;

 

         printk("class  create\n");

         return  0;

 

err_class_create:

         class_destroy(scclass);

         return  err;

}

 

static  void  __exit  scclass_exit(void)

{

         class_remove_file(scclass,&class_attr_version);

         class_destroy(scclass);

         printk("class  destory\n");

}

 

module_init(scclass_init);

module_exit(scclass_exit);

 

MODULE_LICENSE("GPL");

MODULE_AUTHOR("CJOK");

 

上面代码只是创建一个类，我们还需要向类里添加设备，修改设备代码：

 

//@@ -8,6 +8,7 @@


 extern   struct  bus_type   scbus_type ;
 extern  struct   device   scbus;
+extern  struct  class  * scclass;


 static char * Version = "revision 1.0, scdevice";


//@@ -45,6 +46,8 @@
    ret = device_create_file(&scdevice, &dev_attr_version);
    if (ret)
        goto err_create;
+   
+   device_create(scclass, NULL, 0, 0, "scdevice0");


    printk("Create a scdevice");
    return 0;
//@@ -56,6 +59,7 @@


 static void __exit scdevice_exit(void)
 {
+   device_destroy(scclass, 0);
    device_remove_file(&scdevice, &dev_attr_version);

 

灰色为添加的代码

 

试验结果：