Xref: utzoo comp.dcom.modems:1252 comp.sys.att:2224 comp.unix.questions:5201
Path: utzoo!utgpu!water!watmath!clyde!rutgers!princeton!udel!gatech!ncsuvx!lll-winken!lll-crg.llnl.gov!casey
From: casey@lll-crg.llnl.gov (Casey Leedom)
Newsgroups: comp.dcom.modems,comp.sys.att,comp.unix.questions
Subject: Re: dial in / out on same line
Keywords: getty, cu, tip, uucp, dialin, dialout, login
Message-ID: <2953@lll-winken.llnl.gov>
Date: 26 Jan 88 01:43:16 GMT
References: <142@mccc.UUCP> <564@virginia.acc.virginia.edu> <10321@mimsy.UUCP> <148@mccc.UUCP> <10330@mimsy.UUCP>
Sender: usenet@lll-winken.llnl.gov
Reply-To: casey@lll-crg.llnl.gov.UUCP (Casey Leedom)
Organization: Lawrence Livermore National Laboratory
Lines: 28

In article <10330@mimsy.UUCP> chris@mimsy.UUCP (Chris Torek) writes:
>I have written about this before, but let me try for concise[ness]. ...

  The problem with the omitted description is that it's just too
complex.  There's already a perfectly reasonable way of doing what's
necessary and it just isn't being used.  The current mechanism used by
the 4.3BSD drivers to do soft carrier is really for the birds.

  All that really needs to be done [for 4.3BSD] is to declare the flags
parameters in the various driver routines (openi in sys_inode.c calls all
the drivers with the flags word passed in to the original open, but none
of the 4.3BSD tty drivers declares that parameter), and use O_NDELAY to
indicate one doesn't want to wait for carrier instead of the stupid soft
carrier flag arrays currently in use.  The only changes necessary at the
application level would be to have getty, tip, uucp, etc. all open with
O_EXCL and have tip, uucp, etc. also use O_NDELAY.

  These fixes are trivial, straight forward, easy to understand and use,
and are in the original spirit of the open flags parameter.  Anything
else that plays around with the open code is a kludge.  The only other
idea I've heard of any merit is to have a modem server/daemon that can be
contacted for a modem, but that requires the writing of a whole new
program, the design of new paradigms, and probably a significant rewrite
of the application programs needing access to modems.

  Note that the above descriptions all refer explicitly to 4.3BSD but the
concepts should be portable to SYSV.

Casey