Parity on 4.x BSD UNIX ports

[Chris Torek]

In article <12952 at brl-adm.ARPA> cpw%sneezy at lanl.gov (C. Philip Wood) writes:
>... It appears that there are only two choices [for] output, odd or
>even parity. ... our site has chosen to require its hosts to not
>generate parity. ... there are some vendor terminals and emulators
>which ... have an extended character set ... [and print odd graphics
>when receiving characters with parity bits]

>2. What can be done short of a kernel change to provide a solution?

Very little.  You can run in `raw' mode, but that is entirely
unsatisfactory, or in `litout mode', which is somewhat less so.  If you
have 4.3BSD you can run in `litin + litout' mode and write a user level
program to mangle, er, manage, parity over pty lines, and use that to
work around the problem, but this is ugly and slow.

>3. If there is no easy solution.  Should UNIX be modified so
>   that it will not (optionally) generate parity on output?

The 4BSD drivers should be thrown out entirely (`thrown aside with
great force' :-) ).  Berkeley CSRG are working on a POSIX-like tty
interface, which will no doubt fix all this, but that is not likely to
emerge for some time.  Sun may provide something useful soon, what with
their AT&T deal.  Some vendors (e.g., Pyramid) provide a SysV interface
(Pyramid's scheme is convoluted but useable), which can (or should be
able to) do what you need.

In short, it can be done, but it may not be easy.  If you need an
immediate solution, hack the kernel, but be prepared to deal with
the resulting mess.
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7163)
Domain:	chris at mimsy.umd.edu	Path:	uunet!mimsy!chris