Three primary steps are required to open the SCSI device: * Create a message port using CreatePort(). Reply messages from the device must be directed to a message port. * Create an I/O request structure of type IOStdReq. The IOStdReq structure is created by the CreateExtIO() function. CreateExtIO will initialize your IOStdReq to point to your reply port. * Open the SCSI device. Call OpenDevice() passing it the I/O request and the SCSI unit encoded in the unit field. SCSI unit encoding consists of three decimal digits which refer to the SCSI Target ID (bus address) in the 1s digit, the SCSI logical unit (LUN) in the 10s digit, and the controller board in the 100s digit. For example: SCSI unit Meaning --------- ------- 6 drive at address 6 12 LUN 1 on multiple drive controller at address 2 104 second controller board, address 4 88 not valid: both logical units and addresses range from 0-7 The Commodore 2090/2090A unit numbers are encoded differently. The SCSI logical unit (LUN) is in the 100s digit, and the SCSI Target ID is a permuted 1s digit: Target ID 0-6 maps to unit 3-9 (7 is reserved for the controller). 2090/A unit Meaning ---------- ------- 3 drive at address 0 109 drive at address 6, logical unit 1 1 not valid: this is not a SCSI unit.Perhaps it's an ST506 unit. Some controller boards generate a unique name for the second controller board, instead of implementing the 100s digit (e.g., the 2090A's iddisk.device). struct MsgPort *SCSIMP; /* Message port pointer */ struct IOStdReq *SCSIIO; /* IORequest pointer */ /* Create message port */ if (!(SCSIMP = CreatePort(NULL,NULL))) cleanexit("Can't create message port\n",RETURN_FAIL); /* Create IORequest */ if (!(SCSIIO = CreateExtIO(SCSIMP,sizeof(struct IOStdReq)))) cleanexit("Can't create IORequest\n",RETURN_FAIL); /* Open the SCSI device */ if (error = OpenDevice("scsi.device",6L,SCSIIO,0L)) cleanexit("Can't open scsi.device\n",RETURN_FAIL); In the code above, the SCSI unit at address 6 of logical unit 0 of board 0 is opened.
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