Both should be cdevs, not files, so they do not go through the normal filesystem I/O pathway in the kernel and should support select()/poll().  ("ls -l", the first character should be "c" instead of "-" indicating character-mode device nodes.)  If ghc is not detecting that, then *that* is indeed an I/O manager issue.  More generally, anything which is not a regular file according to stat() (in practice this means block devices, character devices, and fifos; directories, sockets, doors, Xenix name files, and other exotics in the filesystem namespace are not generally accessible via standard I/O routines and should probably be failed on open --- in fact, you may have a kernel bug if the system does not fail them on open) should go through the I/O manager.