NAME
        TD_SEEK/ETD_SEEK -- control positioning of the drive heads.

   FUNCTION
        These commands are currently provided for internal diagnostics,
        disk repair, and head cleaning only.

        TD_SEEK and ETD_SEEK move the drive heads to the track specified. The
        io_Offset field should be set to the (byte) offset to which the seek is
        to occur. TD_SEEK and ETD_SEEK do not verify their position until the
        next read. That is, they only move the heads; they do not actually read
        any data.

   IO REQUEST INPUT
        io_Device       preset by the call to opendevice()
        io_Unit         preset by the call to opendevice()
        io_Command      TD_SEEK or ETD_SEEK
        io_Flags        0 or IOF_QUICK
        io_Offset       byte offset from the start of the disk describing
                        where to move the head to.
        iotd_Count      (ETD_SEEK only) maximum allowable change counter
                        value.

   IO REQUEST RESULT
        io_Error - 0 for success, or an error code as defined in
                   <devices/trackdisk.h>