Re: [PARPORT] EPP timeout problem

From: Tom Perkins (
Date: Sun Feb 10 2002 - 10:18:25 EST

  • Next message: Max Vorobiev: "Re: [PARPORT] EPP timeout problem"

    Please state the linux version in use. Also add "verbose_probing=1" to
    the modprobe options for "parport_pc" and include the log records
    generated in your report.

    There is a small code difference between ECP+EPP and EPP modes in
    2.4.14. The ECP+EPP code performs a set direction before calling the EPP

    For ex:

    static size_t parport_pc_ecpepp_read_data (struct parport *port, void *buf,
                                               size_t length, int flags)
            size_t got;

            frob_econtrol (port, 0xe0, ECR_EPP << 5);
    parport_pc_data_reverse (port);
    parport_pc_write_control (port, 0x4);
            got = parport_pc_epp_read_data (port, buf, length, flags);
            frob_econtrol (port, 0xe0, ECR_PS2 << 5);

            return got;

    BTW, I have a datasheet for a chipset that claims this is illegal (ie,
    I'd expect ECP+EPP mode to fail while EPP mode works for this chipset,
    the opposite of what you're seeing). The problems of trying to support
    the quirks of ALL chipsets.

    If you're adventurous try finding the minium set of differences that
    will make your device work in EPP (only mode) and let us know.


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