2012年上学期嵌入式系统设计课程大作业

2012 年上学期嵌入式系统设计课程大作业 1 叙述下列相关名词的含义 ARM xscale PXA255 RISC 体系结构 2 画出嵌入式硬件系统组成的模块结构图 3 叙述基于 linux 的嵌入式平台的搭建过程 4 如下为 xscale 处理器的内核框图 简述内核框图中每个模块的名称及指标 5 下述英文为 BTB 模块功能的详细介绍 阅读后说明该模块的作用 6 下面是 linux 下的一个简单的设备驱动程序 写出 linux 设备驱动常用的数 据结构 同时阅读下面代码 请给出测试程序中的每条语句加以注释 The BTB stores the history of branches that have executed along with their targets Figure 5 1 shows an entry in the BTB where the tag is the instruction address of a previously executed branch and the data contains the target address of the previously executed branch along with two bits of history information The BTB takes the current instruction address and checks to see if this address is a branch that was previously seen It uses bits 8 2 of the current address to select the tag from the BTB and then compares this tag to bits 31 9 1 of the current instruction address If the current instruction address matches the tag in the BTB and the history bits indicate that this branch is usually taken in the past the BTB uses the data target address as the next instruction address to send to the instruction cache 设备驱动程序 Keypad c 的源代码 include include include include include include include include include include include define LEDnKEY MAJOR 251 define KEYPAD NAME X Hyper250 Keypad define KEYPAD VERSION Version 0 1 define EXT KEY CS EXT PORT2 define EXT LED CS EXT PORT3 define LED SHOW 10 EXT KEY CS 为向外部LED进行数值设定 它定义在其它头文件里 void led off on int i EXT LED CS 0 xff for i 0 i 8 i EXT LED CS 1 i 点亮相应LED灯 udelay 30000 EXT LED CS 0 xff 应用程序用open来打开设备文件 实际上调用驱动的lednkey open 函数 int lednkey open struct inode inode struct file filp 打开设备文件 MOD INC USE COUNT 内核提供的一个宏 检查使用驱动程序的用户数 return 0 success int lednkey release struct inode inode struct file filp 释放设备文件 led off on MOD DEC USE COUNT return 0 ssize t lednkey read struct file filp char Putbuf size t length loff t f pos 按键读取函数 unsigned short BottonStatus unsigned char Bottontmp 0 int i BottonStatus EXT KEY CS 按键状态 for i 0 i i copy to user Putbuf 将数据从内核态拷贝到用户态 这是 由定义在里的特殊函数实现在不同的空间传输任意字节的数据 return length ssize t lednkey write struct file filp const char Getbuf size t length loff t f pos int num unsigned char UsrWantLed copy from user 将数据从用户态拷贝到核心态 num UsrWantLed 确定哪一位要进行设定 EXT LED CS 1 num 1 点亮相应LED灯 return 0 int lednkey ioctl struct inode inode struct file filp unsigned int cmd unsigned long arg lednkey ioctl 接口函数 主要用于获取或者改变正在运行的设备参数 switch cmd case LED SHOW 如果要点亮LED灯 if arg led off on break return 0 以下这些驱动函数是与用户的应用程序里对设备文件操作的函数相对应的 struct file operations lednkey fops open lednkey open read lednkey read write lednkey write ioctl lednkey ioctl release lednkey release static int init xhyper250 keypad init void 初始化设备函数 在函数名之前加上这 个属性之后 系统会在初始化完成之后丢弃初始化函数 收回它所占用的内存 以减小内核所 占用的内存空间 它只对内建的驱动起作用 int result result register chrdev LEDnKEY MAJOR lednkey 向操作系统 注册一个主号为251 设备名为 lednkey 并传递设备驱动程序的指针为lednkey fops 全局 变量 其中register chrdev 是内核提供的函数 作用是完成注册新的字符设备 printf s s initialized n KEYPAD NAME KEYPAD VERSION led off on return 0 static void exit xhyper250 keypad exit void 向操作系统卸载设备函数 unregister chrdev LEDnKEY MAJOR lednkey led off on module init xhyper250 keypad init 显式声明初始化设备函数 module exit xhyper250 keypad exit 显式声明卸载设备函数 通过上述两个声明内核知道驱动程序的进入点 测试文件的源代码如下 include include include include include include define LED SHOW 10 int fd static char dev name dev keypad int main int argc char argv int data 0 pre data fd open dev name O RDWR if fd 0 printf s file open failed n dev name exit 1 printf nkeypad App press the push button see show led