Setting termios VMIN > 0 and VTIME > 0 on non blocking file

[Åke Rehnman]

Hello all,

opening a file (serial port) with O_NONBLOCK and subsequently setting 
termios VMIN and VTIME > 0 makes read() never ever return any data 
(returns EAGAIN indefinitely).

Don't ask my why one would want to do something like this but apparently 
the "screen" program think this is a good way of doing things...

Nevertheless not returning any data ever seems wrong.

Any insight on how it is supposed to work is welcome.