title: Read from serial port in a kernel module
body: <p>For my assignment I need to read some strings coming from a serial port.
  This has to be done in a kernel module, so I can't use stdio library.
  I'm trying in this way:</p>
  
  <pre><code>#include &lt;linux/module.h&gt;
  #include &lt;linux/unistd.h&gt;
  #include &lt;asm/io.h&gt;
  #include &lt;asm/fcntl.h&gt;
  #define SERIAL_PORT "/dev/ttyACM0"
  
  void myfun(void){
    int fd = open(SERIAL_PORT,O_RDONLY | O_NOCTTY);
    ..reading...
  </code></pre>
  
  <p>}</p>
  
  <p>but it gives me "implicit declaration of function open"</p>