Re: [PARPORT] How do I send an ECP command from a user level driver?

From: Tim Waugh (
Date: Wed Jul 04 2001 - 09:15:36 EDT

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    On Mon, Jul 02, 2001 at 05:05:35PM -0500, David Lambert wrote:

    > How can I detect when the peripheral sends the host a command,
    > rather than data, without monitoring the status lines directly?

    Not easily. :-(

    If you are trying an ECP data read, and the peripheral sends a channel
    byte, the kernel will stop in the middle of the handshake rather than
    accepting the byte.

    However, you don't get to know why is stopped short: it could just as
    easily be a peripheral timeout.

    If you are trying an ECP channel read, it will just read as many bytes
    as you ask for without checking if they really are channel bytes.

    Suggestions for fixing all this are welcome.

    Does anyone actually _use_ peripheral-to-host channel communications
    then? I was under the impression that no-one did since the ECP
    register spec basically doesn't allow you to ("ecpAFifo [...] The
    operation of this register is defined only fror the forward


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