Linux驅動之裝置模型(7)

8．類

8.1  class

l  Class是對裝置按照功能進行的分類，這樣做是為了給使用者空間提供一個比較友好的界面。Class也是一個kset，對應于/sys/class下的一個目錄

int __initclasses_init(void)

{

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

         if (!class_kset)

                   return -ENOMEM;

         return 0;

}

l  在裝置模型中類由class結構表示

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屬性

l  Class屬性用class_attribute來表示

structclass_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  屬性操作

int __must_checkclass_create_file(struct class *class,

                                                 const struct class_attribute *attr);

voidclass_remove_file(struct class *class,

                                  const struct class_attribute *attr);

8.3    Class基本操作

l  class注冊和登出

intclass_register(struct class *class);

voidclass_unregister(struct class *class);

l  class建立和銷毀

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

voidclass_destroy(struct class *cls);

l  向類添加裝置和删除裝置

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

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

         voiddevice_destroy(struct class *class, dev_t devt)

         devt：裝置号

8.4  執行個體解析

#include <linux/init.h>

#include <linux/module.h>

#include <linux/kernel.h>

#include <linux/device.h>

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)

{

         returnsprintf(buf, "%s\n", Version);

}

CLASS_ATTR(version, 0666,class_show_version, NULL);

static int __init scclass_init(void)

{

         interr;

         scclass= class_create(THIS_MODULE, "scclass");

         err= PTR_ERR(scclass);

         if(IS_ERR(scclass))

                   returnerr;

         err= class_create_file(scclass, &class_attr_version);

         if(err)

                   gotoerr_class_create;

         printk("classcreate\n");

         return0;

err_class_create:

         class_destroy(scclass);

         returnerr;

}

static void __exit scclass_exit(void)

{

         class_remove_file(scclass,&class_attr_version);

         class_destroy(scclass);

         printk("classdestory\n");

}

module_init(scclass_init);

module_exit(scclass_exit);

MODULE_LICENSE("GPL");

MODULE_AUTHOR("CJOK<[email protected]>");

上面代碼隻是建立一個類，我們還需要向類裡添加裝置，修改裝置代碼：

@@ -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);

灰色為添加的代碼

試驗結果：