css selector for getting disabled input field

<input type="text" name="username" value="admin" >
<style type="text/css">
  input[name=username] {
    disabled: true; /* Does not work */
  }
</style>

<input type="text" name="username" value="admin" >

<style type="text/css">
input[name=username] {
    pointer-events: none;
 }
</style>