diff --git a/Linux/KernelDriver/Misc/demo_misc.c b/Linux/KernelDriver/Misc/demo_misc.c
index 57be1c6..f59bc11 100644
--- a/Linux/KernelDriver/Misc/demo_misc.c
+++ b/Linux/KernelDriver/Misc/demo_misc.c
@@ -2,10 +2,25 @@
  * @file    demo_misc.c
  * @author  Rick Chan (cy187lion@sina.com)
  * @brief   Linux misc driver demo.
- * @version 0.1
- * @date    2019-10-15
+            在 Linux 驱动中，会把一些无法归类的设备定义为混杂设备，它们是拥
+            有着共同的特性的简单字符设备。它们的特点是共享统一的主设备号 10，
+            但每个设备可以选择一个单独的次设备号。
+
+            通常情况下，一个字符设备都不得不在初始化的过程中进行下面的步骤：
+
+            1.通过alloc_chrdev_region()分配主/次设备号
+            2.使用cdev_init()和cdev_add()来以一个字符设备注册自己
+
+            而一个misc驱动，则可以只用一个调用misc_register()来完成这所有
+            的步骤。
+
+            所有的 miscdevice 设备形成一个链表，对设备访问时，内核根据次设
+            备号查找对应的 miscdevice 设备，然后调用其 file_operations 
+            中注册的文件操作方法进行操作。
+ * @version 0.1.1
+ * @date    2020-04-27
  * 
- * @copyright Copyright (c) 2019
+ * @copyright Copyright (c) 2020
  * 
  */
 #include <linux/kernel.h>
@@ -17,12 +32,14 @@
 MODULE_AUTHOR("Rick Chan");
 MODULE_LICENSE("GPL");
 
-#define IOCTL_IOC_SIZE 8
-#define IOCTL_IOC   _IOC(_IOC_READ|_IOC_WRITE, 0, 0, IOCTL_IOC_SIZE)
-#define IOCTL_IO    _IO(0, 1)
-#define IOCTL_IOR   _IOR(0, 2, uint16_t)
-#define IOCTL_IOW   _IOW(0, 3, int32_t)
-#define IOCTL_IOWR  _IOWR(0, 4, uint32_t)
+#define DEMO_MAGIC     'R'
+#define DEMO_IOC_SIZE   8
+#define DEMO_CTL_IOC   _IOC(_IOC_READ|_IOC_WRITE, DEMO_MAGIC, 0, DEMO_IOC_SIZE)
+#define DEMO_CTL_IO    _IO(DEMO_MAGIC, 1)
+#define DEMO_CTL_IOR   _IOR(DEMO_MAGIC, 2, uint16_t)
+#define DEMO_CTL_IOW   _IOW(DEMO_MAGIC, 3, int32_t)
+#define DEMO_CTL_IOWR  _IOWR(DEMO_MAGIC, 4, uint32_t)
+#define DEMO_CTL_MAX    5
 
 static int demo_open(struct inode *inode, struct file* filp)
 {
@@ -53,30 +70,48 @@ static ssize_t demo_write(struct file *filp, const char __user *buffer, size_t c
 
 static long demo_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 {
+    static int err = 0;
+
+    // 检测 cmd 合法性.
+    if(DEMO_MAGIC!=_IOC_TYPE(cmd)) 
+        return -EINVAL;
+    if(DEMO_CTL_MAX<_IOC_NR(cmd)) 
+        return -EINVAL;
+
+    // 根据命令类型, 检测参数空间是否可以访问.
+    if(_IOC_DIR(cmd)&_IOC_READ)
+        err = !access_ok(VERIFY_WRITE, (void *)arg, _IOC_SIZE(cmd));
+    else if(_IOC_DIR(cmd)&_IOC_WRITE)
+        err = !access_ok(VERIFY_READ, (void *)arg, _IOC_SIZE(cmd));
+
+    if (err) 
+        return -EFAULT;
+
+    // 根据命令, 来选择执行哪个分支.
     switch(cmd)
     {
-    case IOCTL_IOC:
-    {
-        uint8_t tmp[IOCTL_IOC_SIZE];
+    case DEMO_CTL_IOC:
+       {
+        uint8_t tmp[DEMO_IOC_SIZE];
         copy_from_user(&tmp, (void*)arg, _IOC_SIZE(cmd));
         copy_to_user((void*)arg, &tmp, _IOC_SIZE(cmd));
     }
         break;
-    case IOCTL_IO:
+    case DEMO_CTL_IO:
         break;
-    case IOCTL_IOR:
+    case DEMO_CTL_IOR:
     {
         uint16_t tmp = 0x55AA;
         copy_to_user((void*)arg, &tmp, _IOC_SIZE(cmd));
     }
         break;
-    case IOCTL_IOW:
+    case DEMO_CTL_IOW:
     {
         int32_t tmp = 0;
         copy_from_user(&tmp, (void*)arg, _IOC_SIZE(cmd));
     }
         break;
-    case IOCTL_IOWR:
+    case DEMO_CTL_IOWR:
     {
         uint32_t tmp = 0;
         copy_from_user(&tmp, (void*)arg, _IOC_SIZE(cmd));
@@ -113,14 +148,14 @@ static struct miscdevice demo_dev = {
 
 static int __init demo_init(void)
 {
-    misc_register(&demo_dev);
+    misc_register(&demo_dev);   // 注册混杂设备驱动.
     return 0;
 }
 
 static void __exit demo_exit(void)
 {
-    misc_deregister(&demo_dev);
+    misc_deregister(&demo_dev); // 撤销混杂设备驱动.
 }
 
 module_init(demo_init);
-module_exit(demo_exit);
\ No newline at end of file
+module_exit(demo_exit);