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

From: Dave Strauss (
Date: Mon Aug 27 2001 - 14:17:31 EDT

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    On Mon, 27 Aug 2001 18:51:59 +0100, Philip Blundell <> wrote:
    > >Doesn't that imply, though, that we should dump the software-ECP code?
    > >Is that what we want to do?
    > No, I don't think so. PARPORT_MODE_ECP is supposed to mean "hardware
    > acceleration for ECP is available". There isn't currently a specific
    > capability bit to mean "software emulation of ECP is available", though in
    > practice PARPORT_MODE_PCSPP probably means about that.
    > p.

    OK, now I'm confused. parport_pc on my machine is correctly setting
    the PARPORT_MODE_ECP bit in port->modes because the hardware supports
    ECP mode. However, unless I build parport_pc with
    CONFIG_PARPORT_PC_FIFO and unless the parport_pc options are set
    properly (i.e. unless parport_pc is configured to use DMA) the data
    transfers don't work properly -- I get garbage data. I would like
    this not to happen, so either I need some fixes to the software-ECP
    code (Tim alluded to some changes to this code earlier) or parport_pc
    should disallow ECP mode if it's not configured to use DMA. I think
    you mean we should do the former, in which case other than the bug
    fixes for software-ECP parport_pc doesn't require any changes. Is
    that correct? I should still, of course, change lp.c to look at
    the mode bits before attempting to use ECP mode.

    -- Dave Strauss

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