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

From: Tim Waugh (
Date: Wed Aug 22 2001 - 18:09:07 EDT

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    On Wed, Aug 22, 2001 at 04:06:31PM -0400, Dave Strauss wrote:

    > There are a couple of interesting things about these results. First,
    > most of the performance gain comes from turning on DMA support on the
    > host and not from using ECP mode.

    We don't do RLE. That's probably why. If we did RLE then the ECP
    result would stand a chance of being faster than DMAing in 'printer

    > Second, cutting down on the number
    > of negotiations into and out of ECP mode (going from config 1 to
    > config 2) is worth an extra 50 KB/sec or so, at least in this mix of
    > hosts and printers.

    Up the LP_BUFFER_SIZE. It's that much slower because we're capping
    the amount transferred per write to one page. (Duh!) I can't remember
    exactly why we did that (maybe just arbitrary), but it's obviously
    hurting here.

    > This second result implies that if we want to get any benefit from ECP
    > mode in the lp driver we need to cut down the number of negotiations
    > into and out of ECP mode. The only real way to do this (that I can
    > see) is to do what I did in config 2 -- put the port into ECP mode
    > when lp is opened, and leave it there until lp is closed. However
    > this can cause problems with other drivers which expect the port to be
    > in kept in compatibility mode.

    Going for this approach can work. If lp declares a 'kick' function at
    registration time, it can get told to let go of the port.

    > On a semi-related note, the "probe" code in the parport driver
    > cannot read the IEEE1284 ID from Printer A, even though Windows
    > boxes have no problem with it. Has any work been done on this code
    > lately?

    No, I don't think so. What does deviceid make of it?


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