lpt_port_test Function

The lpt_port_test function is called by lpt_detect to determine whether a printer is present. Here is its function definition:

static int
lpt_port_test(device_t ppbus, u_char data, u_char mask)
{
        int temp, timeout = 10000;

        data &= mask;
      ppb_wdtr(ppbus, data);

        do {
                DELAY(10);
                temp = ppb_rdtr(ppbus) & mask;
        } while (temp != data && --timeout);

      return (temp == data);
}

This function takes an 8-bit value and writes it to the parallel port’s data register. Then it reads from that register and returns whether the value written and read match.