在sys目錄創建接口

在sys目錄創建/sys/zwx_demo/zwx_test_status   接口 

int zwx_test_status = 0;  //文件zwx_test_status的默認值
static struct kobject *zwx_test_kobj;

static ssize_t zwx_test_status_show(struct kobject *kobj, struct kobj_attribute *attr,
        char *buf)
{   
 return sprintf(buf, "%d\n", zwx_test_status);  //讀節點zwx_test_status的值
}

static ssize_t zwx_test_status_store(struct kobject *kobj, struct kobj_attribute *attr,
    const char *buf, size_t count)
{
 char *after;
 unsigned long status = simple_strtoul(buf, &after, 10); 
 zwx_test_status = (int)status;   //寫節點zwx_test_status的值
 
 return count;
}

struct kobj_attribute zwx_test_status_attr = {
  .attr = {"zwx_test_status", 0660},   
    .show = &zwx_test_status_show,     //讀節點zwx_test_status
    .store = &zwx_test_status_store,   //寫節點zwx_test_status
};

static struct attribute * zwx_test_attr[] = {
 &zwx_test_status_attr.attr,    //節點zwx_test_status 的屬性
 
 NULL,
};

static struct attribute_group zwx_test_attr_group = {
 .attrs = zwx_test_attr,      //節點組zwx_test_attr_group，包含zwx_test_attr
};

在代碼實現
  zwx_test_kobj = kobject_create_and_add("zwx_demo", NULL);   //在sys目錄創建zwx_demo目錄
  printk("---zwx--- create zwx_demo node!\n");
  if (zwx_test_kobj)
    rc = sysfs_create_group(zwx_test_kobj, &zwx_test_attr_group); //在sys/zwx_demo/目錄創建zwx_test_status 文件

  
root@android:/sys/zwx_demo # echo 2000 > zwx_test_status                      
root@android:/sys/zwx_demo # cat zwx_test_status                              
2000
root@android:/sys/zwx_demo #