scsi_dpc_cookie
status_t (*alloc_dpc)(scsi_dpc_cookie *dpc);
status_t (*free_dpc)(scsi_dpc_cookie dpc);
status_t (*schedule_dpc)(scsi_bus cookie, scsi_dpc_cookie dpc, /*int flags,*/
scsi_dpc_cookie fBusDPC;
scsi_dpc_cookie fEventDPC;