Re: [PARPORT] I/O ports and the parallel interface

From: Tim Waugh (
Date: Wed Jan 29 2003 - 18:30:50 EST

  • Next message: Jeff Silverman: "Re: [PARPORT] Parport as a serial port?"

    On Wed, Jan 29, 2003 at 11:27:36PM +0000, Joe Lang wrote:

    > Really?
    > How does one use /dev/ports?

    Read the documentation (I actually wrote some).

    > What if there are 2 or more parallel adaptors?

    /dev/parport0, /dev/parport1, etc.

    > > The kernel figures this out by guessing, largely.
    > Guessing?
    > You are kidding...right?

    Not really. Take a look at the code. It guesses an address, and then
    pokes it to see if it behaves like a parallel port. It's quite easy
    to guess the addresses: by far the most common are 0x278, 0x378 and
    0x3bc. For PCI cards of course it's a lot easier.

    > How much other guessing is done in Linux?

    Most ISA devices have to be probed like that.


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