20145202、20145225、20145234 《信息安全系统设计基础》实验四实时系统的移植

实验步骤：

1.配置环境

2.阅读和理解代码

#define DEVICE_NAME  "demo"
static ssize_t demo_write(struct file *filp,const char * buffer, size_t count)
{ 
    char drv_buf[];
    copy_from_user(drv_buf , buffer, count);
    …
}
static ssize_t demo_read(struct file *filp,char *buffer,size_t count,loff_t *ppos)
{
char drv_buf[];
copy_to_user(buffer, drv_buf,count);
….
}
static int demo_ioctl(struct inode *inode, struct file *file,unsigned int cmd, unsigned long arg)
{
}
static int demo_open(struct inode *inode, struct file *file)
{
}
static int demo_release(struct inode *inode, struct file *filp)
{
    MOD_DEC_USE_COUNT;
    DPRINTK("device release\n");
    return 0;
}
static struct file_operations demo_fops = {
    owner:  THIS_MODULE,
    write:demo_write, 
    read: demo_read, 
    ioctl: demo_ioctl,
    open: demo_open,
    release:demo_release,
};
#ifdef CONFIG_DEVFS_FS
static devfs_handle_t devfs_demo_dir, devfs_demoraw;
#endif
static int __init demo_init(void)
{
    int result;
    #ifdef CONFIG_DEVFS_FS
    devfs_demo_dir = devfs_mk_dir(NULL, "demo", NULL);
    devfs_demoraw = devfs_register(devfs_demo_dir, "0", DEVFS_FL_DEFAULT,
    demo_Major, demo_MINOR, S_IFCHR | S_IRUSR | S_IWUSR,&demo_fops, NULL);
    ＃else
    SET_MODULE_OWNER(&demo_fops);
    result = register_chrdev(demo_Major, "scullc", &demo_fops);
    if (result < 0) return result;
    if (demo_Major == 0) demo_Major = result; /* dynamic */
    #endif
    printk(DEVICE_NAME " initialized\n");
    return 0;
}
static void __exit demo_exit(void)
{
    unregister_chrdev(demo_major, "demo");
    kfree(demo_devices);
    printk(DEVICE_NAME " unloaded\n");
}
module_init(demo_init);
module_exit(demo_exit);