ioctl_functions.html

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<p>
The header file is set up first 
</p>
<pre class="code c">  <span class="coMULTI">/* file name samp.h for both user and kernel space */</span>                    
  <span class="co2">#include &lt;asm/ioctl.h&gt;                                                   </span>
                                                                           
  <span class="coMULTI">/* magic number for SCMD IOCTL operations */</span>                             
  <span class="co2">#define SCMD_MAGIC 's'                                                   </span>
                                                                           
  <span class="co2">#define SCMD_IOCGETD  _IOR(SCMD_MAGIC, 1 , char *) //get driver data     </span>
  <span class="co2">#define SCMD_IOCSETD  _IOW(SCMD_MAGIC, 2 , char *) //set driver data     </span>
  <span class="co2">#define SCMD_IOCXCHD  _IOWR(SCMD_MAGIC,3 , char *) //exchange driver data</span></pre>
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<h3><a name="ioctl_addition_to_driver" id="ioctl_addition_to_driver">IOCTL Addition to Driver</a></h3>
<div class="level3">

<p>
 Next a section of the driver is added. 
</p>
<pre class="code c">&nbsp;
  <span class="kw4">int</span> scmd_ioctl<span class="br0">&#40;</span><span class="kw4">struct</span> inode* inode , <span class="kw4">struct</span> file* filp ,                 
                                  <span class="kw4">unsigned</span> <span class="kw4">int</span> cmd , <span class="kw4">unsigned</span> <span class="kw4">long</span>  arg <span class="br0">&#41;</span> <span class="br0">&#123;</span>
     <span class="kw4">int</span> ret;                                                              
     <span class="kw4">int</span> count;                                                            
     <span class="kw4">char</span> temp<span class="br0">&#91;</span>SCMD_SIZE<span class="br0">&#93;</span>;                                                 
     scmd_dev_t * dev;                                                     
                                                                           
     count = SCMD_SIZE;                                                    
     dev = <span class="br0">&#40;</span>scmd_dev_t *<span class="br0">&#41;</span> filp-&gt;private_data;                              
                                                                           
     <span class="kw1">switch</span> <span class="br0">&#40;</span>cmd<span class="br0">&#41;</span> <span class="br0">&#123;</span>                                                        
        <span class="kw1">case</span> SCMD_IOCGETD:                                                 
           <span class="kw1">if</span><span class="br0">&#40;</span>copy_to_user<span class="br0">&#40;</span><span class="br0">&#40;</span><span class="kw4">unsigned</span> <span class="kw4">char</span> *<span class="br0">&#41;</span>arg, dev-&gt;data, count<span class="br0">&#41;</span><span class="br0">&#41;</span>        
               <span class="kw1">return</span> -EFAULT;                                             
           <span class="kw1">return</span> <span class="nu0">0</span>;                                                       
                                                                           
        <span class="kw1">case</span> SCMD_IOCSETD:                                                 
           <span class="kw1">if</span> <span class="br0">&#40;</span>copy_from_user<span class="br0">&#40;</span>dev-&gt;data, <span class="br0">&#40;</span><span class="kw4">unsigned</span> <span class="kw4">char</span> *<span class="br0">&#41;</span>arg, count<span class="br0">&#41;</span><span class="br0">&#41;</span>     
               <span class="kw1">return</span> -EFAULT;                                             
           <span class="kw1">return</span> <span class="nu0">0</span>;                                                       
                                                                           
        <span class="kw1">case</span> SCMD_IOCXCHD:                                                 
           memcopy<span class="br0">&#40;</span> <span class="br0">&#40;</span><span class="kw4">unsigned</span> <span class="kw4">char</span> *<span class="br0">&#41;</span>&amp;temp,                                
                        <span class="br0">&#40;</span><span class="kw4">unsigned</span> <span class="kw4">char</span> *<span class="br0">&#41;</span>dev-&gt;data, count<span class="br0">&#41;</span>;                
                                                                           
           <span class="kw1">if</span> <span class="br0">&#40;</span>copy_from_user<span class="br0">&#40;</span><span class="br0">&#40;</span><span class="kw4">unsigned</span> <span class="kw4">char</span> *<span class="br0">&#41;</span>dev-&gt;data,                  
                              <span class="br0">&#40;</span><span class="kw4">unsigned</span> <span class="kw4">char</span> *<span class="br0">&#41;</span>arg, count<span class="br0">&#41;</span><span class="br0">&#41;</span>                
               <span class="kw1">return</span> -EFAULT;                                             
                                                                           
           <span class="kw1">if</span> <span class="br0">&#40;</span>copy_to_user<span class="br0">&#40;</span><span class="br0">&#40;</span><span class="kw4">unsigned</span> <span class="kw4">char</span> *<span class="br0">&#41;</span>arg,                          
                              <span class="br0">&#40;</span><span class="kw4">unsigned</span> <span class="kw4">char</span> *<span class="br0">&#41;</span>&amp;temp, count<span class="br0">&#41;</span><span class="br0">&#41;</span>              
               <span class="kw1">return</span> -EFAULT;                                             
                                                                           
           <span class="kw1">return</span> <span class="nu0">0</span>;                                                       
                                                                           
        <span class="kw1">default</span>:                                                           
           <span class="kw1">return</span> -ENOTTY;                                                 
  <span class="coMULTI">/*         return -EINVAL; another return option */</span>                      
     <span class="br0">&#125;</span>                                                                     
  <span class="br0">&#125;</span>       
&nbsp;
&nbsp;</pre>
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<h3><a name="ioctl_fops_table" id="ioctl_fops_table">IOCTL Fops Table</a></h3>
<div class="level3">

<p>
 The fops table needs to be set up in the driver init function 
</p>
<pre class="code c">&nbsp;
    scmd_driver_fops.<span class="me1">write</span> = scmd_write;               
    <span class="co1">// set up the ioctl function                       </span>
    scmd_driver_fops.<span class="me1">ioctl</span> = scmd_ioctl;               
                                                       
    printk<span class="br0">&#40;</span><span class="st0">" scmd_ioctl module set up ret = %d<span class="es0">\n</span>"</span>,ret<span class="br0">&#41;</span>;</pre>
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<h3><a name="user_code" id="user_code">User code</a></h3>
<div class="level3">

<p>
 A typical user code file
</p>
<pre class="code c">  <span class="co1">// test_ioctl.c simple test for ioctl             </span>
  <span class="co1">// cc -O2 -o test_ioctl test_ioctl.c              </span>
  <span class="co2">#include &lt;stdio.h&gt;                                </span>
  <span class="co2">#include &lt;fcntl.h&gt;                                </span>
  <span class="co2">#include &lt;unistd.h&gt;                               </span>
  <span class="co2">#include &quot;scmd_ioctl.h&quot;                           </span>
  <span class="co2">#define SCMD_DEVICE &quot;/dev/scmd&quot;                   </span>
                                                    
  <span class="kw4">int</span> main <span class="br0">&#40;</span><span class="br0">&#41;</span> <span class="br0">&#123;</span>                                     
    <span class="kw4">int</span> fd;                                         
    <span class="kw4">int</span> ret;                                        
    <span class="kw4">int</span> i;                                          
    <span class="kw4">char</span> scmd_data<span class="br0">&#91;</span>SCMD_SIZE<span class="br0">&#93;</span>;                      
                                                    
    fd = open<span class="br0">&#40;</span>SCMD_DEVICE,O_RDWR<span class="br0">&#41;</span>;                  
    <span class="kw1">if</span> <span class="br0">&#40;</span> fd &lt; <span class="nu0">0</span> <span class="br0">&#41;</span> <span class="br0">&#123;</span>                                 
      <a href="http://www.opengroup.org/onlinepubs/009695399/functions/printf.html"><span class="kw3">printf</span></a><span class="br0">&#40;</span><span class="st0">" failed to open %s <span class="es0">\n</span>"</span>,SCMD_DEVICE<span class="br0">&#41;</span>;  
      exit <span class="br0">&#40;</span><span class="nu0">1</span><span class="br0">&#41;</span>;                                     
    <span class="br0">&#125;</span>                                               
    ret = ioctl<span class="br0">&#40;</span>fd,SCMD_IOCGETD,&amp;scmd_data<span class="br0">&#41;</span>;        
    <span class="kw1">if</span> <span class="br0">&#40;</span> ret &lt; <span class="nu0">0</span> <span class="br0">&#41;</span> <span class="br0">&#123;</span>                                
      <a href="http://www.opengroup.org/onlinepubs/009695399/functions/printf.html"><span class="kw3">printf</span></a><span class="br0">&#40;</span><span class="st0">" failed to GETD on %s<span class="es0">\n</span>"</span>,SCMD_DEVICE<span class="br0">&#41;</span>;
      exit<span class="br0">&#40;</span><span class="nu0">1</span><span class="br0">&#41;</span>;                                      
    <span class="br0">&#125;</span>                                               
    <a href="http://www.opengroup.org/onlinepubs/009695399/functions/printf.html"><span class="kw3">printf</span></a><span class="br0">&#40;</span><span class="st0">"initial data ...<span class="es0">\n</span>"</span><span class="br0">&#41;</span>;                   
    <span class="kw1">for</span> <span class="br0">&#40;</span>i = <span class="nu0">0</span> ; i &lt; <span class="nu0">8</span> ; i++ <span class="br0">&#41;</span> <span class="br0">&#123;</span>                    
      <a href="http://www.opengroup.org/onlinepubs/009695399/functions/printf.html"><span class="kw3">printf</span></a><span class="br0">&#40;</span><span class="st0">"data[%d] %x     data[%d] %x<span class="es0">\n</span>"</span>,       
             i,scmd_data<span class="br0">&#91;</span>i<span class="br0">&#93;</span>,                        
             i<span class="nu0">+8</span>,scmd_data<span class="br0">&#91;</span>i<span class="nu0">+8</span><span class="br0">&#93;</span><span class="br0">&#41;</span>;                   
    <span class="br0">&#125;</span>                                               
    close<span class="br0">&#40;</span>fd<span class="br0">&#41;</span>;                                      
    <span class="kw1">return</span> <span class="nu0">0</span>;                                       
  <span class="br0">&#125;</span>                                                 
                                                    
&nbsp;</pre>
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