The file driver is a test tool. It can log recieved data to a disk file, and optionally also send data from another file.
The device argument is a file where the logged data will be saved. The saved data is printable, line like
       space 50000
       pulse 850
       space 400
  i. e., like presented by mode2(1).
  The driver supports the set-infile driver option, which can be
  set using lircd -A/--driver-option option. The infile is in the same
  format as the logged data.
  The driver also supports the send-space option. This is used to
  send spaces longer than what can be represented with normal data, typical
  a gap. 
Upon a request to send a LIRC_EOF pulse the driver will terminate the running process using SIGUSR1.