The SCSI device operates like other Amiga devices.  To use it, you must
first open the SCSI device, then send I/O requests to it, and then close
it when finished.  See the "introduction to amiga system devices"
chapter for general information on device usage.

The power of the SCSI device comes from its special facility for passing
SCSI and SCSI-2 command blocks to any SCSI unit on the bus.  This facility
is commonly called SCSI-direct and it allows the Amiga to perform SCSI
functions that are "non-standard" in terms of the normal Amiga I/O model.

To send SCSI-direct or other commands to the SCSI device, an extended I/O
request structure named IOStdReq is used.

   struct IOStdReq
   {
       struct  Message io_Message;
       struct  Device  *io_Device;/* device node pointer  */
       struct  Unit    *io_Unit;  /* unit (driver private)*/
       UWORD   io_Command;        /* device command */
       UBYTE   io_Flags;
       BYTE    io_Error;          /* error or warning num */
       ULONG   io_Actual;         /* actual number of bytes transferred */
       ULONG   io_Length;         /* requested number bytes transferred*/
       APTR    io_Data;           /* points to data area */
       ULONG   io_Offset;         /* offset for block structured devices */
   };

See the include file exec/io.h for the complete structure definition.

 opening the scsi device 
 closing the scsi device