Re: [PARPORT] ECP mode transfers in 2.4.x kernels

From: Dave Strauss (
Date: Mon Aug 27 2001 - 13:38:08 EDT

  • Next message: Dave Strauss: "Re: [PARPORT] ECP mode transfers in 2.4.x kernels"

    On Mon, 27 Aug 2001 18:28:19 +0100, Philip Blundell <> wrote:
    > >In the long run I think you're right, but I was trying to deal with
    > >the fact that the parport ECP mode doesn't work unless DMA is used.
    > Can you be more specific about what goes wrong with it? In theory
    > it should be possible to negotiate into (and use!) ECP mode on any
    > port -- if hardware assistance isn't available, parport will
    > perform ECP protocol in software. From the lp point of view using
    > software-ECP is probably a bad thing for performance, but it should
    > still work the same and I think we should retain the ability for
    > drivers to do this if they want to, say if some particular
    > peripheral functionality is only available in ECP mode.

    The problem I was having with software-ECP was that I was getting
    garbage data at the printer. I never figured out if it was missing,
    extra, or just garbled data because the problem went away once
    I compiled with FIFO/DMA support.

    > Having thought about it some more, I'm now convinced that
    > parport_pc should only set bits in port->modes when a particular
    > mode is both supported by the underlying hardware and available in
    > this configuration. It sounds like there might still be other
    > bugs, but that should be enough to make your particular problem go
    > away. Could you produce a patch to do that, plus a modified
    > version of your lp.c change?
    > p.

    Yes, I can do that.

    -- Dave Strauss

    -- To unsubscribe, send mail to: --
    -- with the single word "unsubscribe" in the body of the message. --

    This archive was generated by hypermail 2b29 : Mon Aug 27 2001 - 13:38:53 EDT