STREAMS tty drivers for SysV

[Vernon Schryver]

In article <KLEMETS.89Jun8171157 at tum.sics.se>, klemets at sics.se (Anders Klemets) writes:
> ...
> On SUN 4.0 the ttys are STREAM devices, but definitely not on this
> System V box.
> Does anybody know if the ttys are STREAM devices on the Interactive
> Systems 386/IX OS? ...

It is impossible to put a SVID-compliant tty under the SVR3.[012] stream head
as it comes on the 3B2 source tapes.  There is no provision for VTIM/VMIN in
the SVR3 streams head, and you cannot do it below the head in SVR3 streams.
Also, the SVR3 stream head believes a non-blocking read returns EAGAIN like
BSD ttys and other, reasonable SV devices, instead of 0 like SVID tty's.

Sun may have an advantage or two.  Did they put a BSD "new tty" style driver
under their streams, instead of something current-SVID-compliant?  They might
reasonably expect someone to listen to their requests to change the next
version of the SVID.  They may also have modified the stream head.

I can authoritatively state that at least one SVR3 vendor is shipping a
SVID-compliant streams tty driver, based on an extended streams head.  You
also need streams character drivers for the bottom, and some kind of line
discipline module.  The one I did is not small, even if the stack is 12x
faster than what it replaced.  It would be impossible to correctly emulate
each and every bug (oops, I mean feature) of the ancient tty driver without
source.


Vernon Schryver
vjs at calcite.uucp