Re: [PARPORT] new ppdev operations

From: Tim Waugh (
Date: Tue Jun 19 2001 - 12:49:37 EDT

  • Next message: Uwe Bonnes: "Re: [PARPORT] new ppdev operations"

    On Tue, Jun 19, 2001 at 06:40:47PM +0200, Uwe Bonnes wrote:

    > isn't ppdev also good for any emulation (wine,dosemu), where the
    > emulated program does direct port access e.g. with inb() and
    > outb(). The emulated programm might also want to access the fifo
    > addresses...

    That's not what ppdev is for. It isn't 'access to a PC-style parallel
    port', but 'access to an IEEE 1284 parallel port of some sort', with
    an interface that is supposed to make it fast for actually using
    PC-style ports since they're so common. For emulation, you need to
    actually do the emulation and pretend that you're a parallel port.

    Dream up a set of hardware modes that you can provide assistance with
    (or better yet, ask ppdev). Then trap the I/O and handle it. For SPP
    registers, easy: ioctl ppdev.

    For EPP register accesses, you need to ioctl ppdev into EPP mode (if
    necessary), and read() or write() the appropriate amount. [Yes, this
    is another valid reason that you might not know how much data to
    expect, and I was wrong the other day when I said that you should
    always know.]

    For ECR accesses, you need to be smarter. If you are going to offer
    an ECR, your 'FIFO' can be just a buffer that periodically write()s
    out to ppdev, or in input mode read()s with a short timeout.

    The easiest thing to do, of course, is to only offer emulated SPP


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