Matador
Well-known member
Andy Peters said:Can you do direct parallel-port access with a modern version of Linux?
-a
Not really: nothing like what could be done with OUTB in DOS days.
Most of the 'parallel port' cards are just bit-banged interfaces sitting behind PCIe bridge chips like those from PLX Tech. Programming them involves a complicated interrupt model and you can't guarantee latencies (don't ask me how I learned this). In addition, most force you to go through an extensive FIFO (as they are assuming you'll want to burst many megabytes of data at maximum speed), so the programming model looks something like a) send a short packet, b) ask the PCIe chip to flush it's FIFO, c) spin waiting for that to happen (or register a callback for when it's done), d) weep into your coffee mug.