/BAKFID=backlink-file-id Use this qualifier to look for a file
    with a specific backlink. Only the first part of the file id
    must be specified, that is, if the File id is (x,y,z) one must
    specify'x' as the file-id. Use this qualifier to get files from a
    specific directory. If /BAKFID=0 is used, DFU returns files not
    belonging to a directory (often temporary files).