8.13. SG_GET_REQUEST_TABLE

        req_state
            0 -> request not in use
            1 -> request has been sent, but is not finished (i.e. it is
                 between stages 1 and 2 in the "theory of operation")
            2 -> request is ready to be read() (i.e. it is between stages
                 2 and 3 in the "theory of operation")
        orphan
            0 -> normal request
            1 -> request sent by SG_IO ioctl() which has been interrupted
                 by a signal
        sg_io_owned
            0 -> request sent by a write()
            1 -> request sent by a SG_IO ioctl()
        problem
            0 -> no problem (or 1 == req_state)
            1 -> req_state is 2 and either masked_status, host_status or
                 driver_status is non-zero
        duration
            [if 1 == req_state] time since request was sent (in millisecs)
            [if 2 == req_state] duration of request (in millisecs). Clock
                 is stopped when stage 2 in "theory of operation" is
                 reached
        pack_id
        usr_ptr
            these are user provided values in the sg_io_hdr_t (or
            struct sg_header) that sent the request