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From: mjacob@wonky.Eng.Sun.COM (Matt Jacob)
Newsgroups: comp.periphs.scsi
Subject: Re: What's a poor target to do?
Keywords: message out, parity error
Message-ID: <138463@sun.Eng.Sun.COM>
Date: 6 Jul 90 09:55:30 GMT
References: <363@zds-ux.UUCP>
Sender: news@sun.Eng.Sun.COM
Organization: Sun Microsystems, Mt. View, Ca.
Lines: 37

In article <363@zds-ux.UUCP> bjstaff@zds-ux.UUCP (Brad Staff) writes:
>Imagine for a moment, if you will, the following:
>1.  The target signals a 'data in' phase.
>2.  The initiator detects a parity error in the data, and asserts ATN.
>3.  The target notices that ATN is asserted, and signals a 'message out' phase.
>4.  The initiator sends an 'initiator detected error' message.
>5.  The target detects a parity error in the message.
>
>What's the poor target to do?  I can't find anything in the SCSI-1 spec that
>addresses this situation.  Perhaps the SCSI-2 spec does address this situation?

Well, I don't have my scsi-2 spec in front of me, but here is a segment
from a host adapter driver that gives a clue:

        /*
         * If we finish sending a message out, and we are
         * still in message out phase, then the target has
         * detected one or more parity errors in the message
         * we just sent and it is asking us to resend the
         * previous message.
         */

        if ((esp->e_intr & ESP_INT_BUS) && phase == ESP_PHASE_MSG_OUT) {
                /*
                 * As per SCSI-2 specification, if the message to
                 * be re-sent is greater than one byte, then we
                 * have to set ATN*.
                 */
                if (esp->e_omsglen > 1) {
                        ep->esp_cmd = CMD_SET_ATN;
                }
                esplog(esp, LOG_ERR,
                    "SCSI bus MESSAGE OUT phase parity error");
                sp->cmd_pkt.pkt_statistics |= STAT_PERR;
                New_state(esp, ACTS_MSG_OUT);
                return (ACTION_PHASEMANAGE);
        }