Serial i386 - high priority IRQ & disable FIFO

[Pedro Zorzenon Neto <pzn@terra.com.br>]

Please CC your reply to me, I'm not a subscriber of this list.

Hi all,

  I need to use a special device conected to the other end in a hardware installed this way:
  PC - modem - telephoneline - modem - device.

  So.. what is the problem?
  The device sends "messages" to the PC of 1 to 4 bytes. and the PC answer these messages as a slave.

  This messages must be answered by the PC aplication as soon as possible, so I used irqtune to give the highest priority to the serial port.
  Sometimes (about once each 50 messages) that fails (takes about 8 seconds to aplication receive the message) and I think that it could be the PC UART FIFO.
  Do you have any hint about disabling the FIFO? Is there any FIFO size parameter that specifies how many bytes should FIFO have before IRQ is set?

  I already monitored the serial wires at the pc port and the delay is inside the PC. The PC UART is 16550A. This PC has woody distribution installed.

    Thanks in advance,
    Pedro