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实验三 设备驱动程序
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<font color="#3D5063"> 题目：掌握增加设备驱动程序的方法。通过模块方法，增加一个新的设备驱动程序，其功能可以简单。要求实现字符设备的驱动。</font></span></p>
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设计分析：题目要求实现虚拟字符设备的驱动程序，其功能可以简单一些，能进行读写操作。按照典型的驱动程序，大体上可分为几个部分，可分别进行填充，得到简单的设备驱动。</font></span></p>
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<font size="2" color="#3D5063"> (1)</font></span><span style="font-family:
宋体"><font size="2" color="#3D5063">注册设备：在<span lang="EN-US">init_module()</span>中调用<span lang="EN-US">register_chrdev()</span>函数来注册设备，并返回主设备号。</font></span></p>
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<font size="2" color="#3D5063"> (2)</font></span><span style="font-family:宋体"><font size="2" color="#3D5063">定义功能函数：其中包括打开函数<span lang="EN-US">(open_test)</span>与释放函数<span lang="EN-US">(release_test)</span>；读操作函数<span lang="EN-US">(read_test)</span>与写操作函数<span lang="EN-US">(write_test)</span>。</font></span></p>
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<font size="2" color="#3D5063"> (3)</font></span><span style="font-family:宋体"><font size="2" color="#3D5063">卸载设备：在<span lang="EN-US">cleanup_module()</span>中调用<span lang="EN-US">unregister_chrdev()</span>函数来卸载设备。</font></span></p>
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<font size="2" color="#3D5063"> </font></span></p>
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<font size="2" color="#3D5063">test.c</font></span><span style="font-family:宋体"><font size="2" color="#3D5063">是由上得到的驱动程序，其内容如下：</font></span></p>
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<font size="2" color="#3D5063"> </font></span></p>
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<font size="2" color="#3D5063">#define __NO_VERSION__</font></span></p>
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<font size="2" color="#3D5063"> </font></span></p>
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<font size="2" color="#3D5063">#include <linux/module.h></font></span></p>
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<font size="2" color="#3D5063">#include <linux/config.h></font></span></p>
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<font size="2" color="#3D5063">#include <linux/version.h></font></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-family:宋体">
<font size="2" color="#3D5063"> </font></span></p>
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<font size="2" color="#3D5063">#include <asm/uaccess.h></font></span></p>
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<font size="2" color="#3D5063">#include <asm/segment.h></font></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-family:宋体">
<font size="2" color="#3D5063"> </font></span></p>
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<font size="2" color="#3D5063">#include <linux/types.h></font></span></p>
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<font size="2" color="#3D5063">#include <linux/fs.h></font></span></p>
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<font size="2" color="#3D5063">#include <linux/mm.h></font></span></p>
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<font size="2" color="#3D5063">#include <linux/errno.h></font></span></p>
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<font size="2" color="#3D5063"> </font></span></p>
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<font size="2" color="#3D5063">unsigned int test_major = 0;/*</font></span><span style="font-family:宋体"><font size="2" color="#3D5063">主设备号</font><span lang="EN-US"><font size="2" color="#3D5063">*/</font></span></span></p>
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<font size="2" color="#3D5063">char mybuf[10];</font></span></p>
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<font size="2" color="#3D5063"> </font></span></p>
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<font size="2" color="#3D5063">/*</font></span><span style="font-family:宋体"><font size="2" color="#3D5063">将内核空间的<span lang="EN-US">mybuf</span>中的字符串赋给用户空间的<span lang="EN-US">buf</span>区</font><span lang="EN-US"><font size="2" color="#3D5063">*/</font></span></span></p>
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<font size="2" color="#3D5063">static ssize_t read_test(struct file *file,char *buf,size_t
count,loff_t *f_pos){ </font></span></p>
<p class="MsoNormal" style="text-indent: 21.0pt">
<span lang="EN-US" style="font-family:宋体"><font size="2" color="#3D5063">int
length=strlen(mybuf);</font></span></p>
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<span lang="EN-US" style="font-family:宋体"><font size="2" color="#3D5063"> </font></span></p>
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<span lang="EN-US" style="font-family:宋体"><font size="2" color="#3D5063">if (verify_area(VERIFY_WRITE,buf,count)
== -EFAULT )</font></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-family:宋体">
<font size="2" color="#3D5063"> return -EFAULT;</font></span></p>
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<span lang="EN-US" style="font-family:宋体"><font size="2" color="#3D5063">
if(count>9)count=9;</font></span></p>
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<font size="2" color="#3D5063"> count=length-*fpos;</font></span></p>
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<font size="2" color="#3D5063"> if(copy_to_user(buf,mybuf,count))</font></span></p>
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<font size="2" color="#3D5063"> return -EFAULT;</font></span></p>
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<font size="2" color="#3D5063"> *f_pos+=count;</font></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-family:宋体">
<font size="2" color="#3D5063"> return count;</font></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-family:宋体">
<font size="2" color="#3D5063">}</font></span></p>
<p class="MsoNormal"> </p>
<p class="MsoNormal"><span lang="EN-US" style="font-family:宋体">
<font size="2" color="#3D5063">/*</font></span><span style="font-family:宋体"><font size="2" color="#3D5063">将用户空间的<span lang="EN-US">buf</span>字符串赋给内核空间的<span lang="EN-US">mybuf[]</span>数组中</font><span lang="EN-US"><font size="2" color="#3D5063">*/</font></span></span></p>
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<font size="2" color="#3D5063">static ssize_t write_test(struct file *file,
const char *buf, size_t count, loff_t *f_pos){</font></span></p>
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<span lang="EN-US" style="font-family:宋体"><font size="2" color="#3D5063">int
num;</font></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-family:宋体">
<font size="2" color="#3D5063"> num=count<10?count:10;</font></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-family:宋体">
<font size="2" color="#3D5063"> if(copy_from_user(mybuf,buf,num))</font></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-family:宋体">
<font size="2" color="#3D5063"> return -EFAULT;</font></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-family:宋体">
<font size="2" color="#3D5063"> return num;</font></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-family:宋体">
<font size="2" color="#3D5063">}</font></span></p>
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<font size="2" color="#3D5063">/*</font></span><span style="font-family:宋体"><font size="2" color="#3D5063">打开设备函数，将用户数增一</font><span lang="EN-US"><font size="2" color="#3D5063">*/</font></span></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-family:宋体">
<font size="2" color="#3D5063">static int open_test(struct inode *inode,struct
file *file ){</font></span></p>
<p class="MsoNormal" style="text-indent: 21.0pt">
<span lang="EN-US" style="font-family:宋体"><font size="2" color="#3D5063">
MOD_INC_USE_COUNT;</font></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-family:宋体">
<font size="2" color="#3D5063"> return 0;</font></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-family:宋体">
<font size="2" color="#3D5063">}</font></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-family:宋体">
<font size="2" color="#3D5063">/*</font></span><span style="font-family:宋体"><font size="2" color="#3D5063">关闭设备函数，将用户数减一</font><span lang="EN-US"><font size="2" color="#3D5063">*/</font></span></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-family:宋体">
<font size="2" color="#3D5063">static int release_test(struct inode *inode,struct
file *file ){</font></span></p>
<p class="MsoNormal" style="text-indent: 21.0pt">
<span lang="EN-US" style="font-family:宋体"><font size="2" color="#3D5063">
MOD_DEC_USE_COUNT;</font></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-family:宋体">
<font size="2" color="#3D5063"> return 0;</font></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-family:宋体">
<font size="2" color="#3D5063">}</font></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-family:宋体">
<font size="2" color="#3D5063">/*</font></span><span style="font-family:宋体"><font size="2" color="#3D5063">定义设备函数接口</font><span lang="EN-US"><font size="2" color="#3D5063">*/</font></span></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-family:宋体">
<font size="2" color="#3D5063">struct file_operations test_fops = {</font></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-family:宋体">
<font size="2" color="#3D5063"> read:read_test,</font></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-family:宋体">
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