Re: [PARPORT] reverse channel negotiation fails under CPU load

From: Tim Waugh (
Date: Thu Oct 11 2001 - 06:39:53 EDT

  • Next message: Tim Waugh: "Re: [PARPORT] PARPORT"

    On Sun, Sep 23, 2001 at 11:31:51PM -0400, Dmitri Katchalov wrote:

    > I'm writing a usermode driver for my Brother MFC 4600 printer/scanner/fax.
    > The driver periodically polls the device for incoming data packets
    > by switching to IEEE reverse byte mode, reading the data (if any) from
    > the port and then switching back to compat mode.
    > It works OK as long as the computer is idle. As soon as I put any kind of
    > load on a CPU (even running ps on another console)
    > ioctl (parport,PPNEGOT,&IEEE_MODE_BYTE) starts failing with
    > "input/output error".
    > I'm running 2.4.7 kernel on P120 Toshiba laptop.
    > Parport driver correctly auto-detects TRISTATE, ECP, DMA and IRQ settings
    > and otherwise appears to be configured and functioning properly.
    > Any ideas?

    I _guess_ that there is a schedule() in a timing-critical piece of
    code. Is there anything in the output of 'dmesg' to suggest where
    exactly the I/O error is originating, i.e. which event number?


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