title: How to get lid state using linux kernel module?
body: <p>I can read the status of my laptop lid by reading <code>/proc/acpi/button/lid/LID0/state</code> file. Now I want to read it from kernel module. </p>
  
  <p>I found the source file <code>drivers/acpi/button.c</code> in kernel source. But still I didn't understand how to use it. It exporting <code>acpi_lid_notifier_register, acpi_lid_notifier_unregiste</code> and <code>acpi_lid_open</code> functions.</p>
  
  <p>How to write a module for lid state?</p>