Xref: utzoo comp.sys.att:4159 unix-pc.general:1321
Path: utzoo!utgpu!water!watmath!uunet!lll-winken!lll-tis!helios.ee.lbl.gov!pasteur!ames!mailrus!uwmcsd1!nic.MR.NET!umn-cs!umn-d-ub!rhealey
From: rhealey@umn-d-ub.D.UMN.EDU (Rob Healey)
Newsgroups: comp.sys.att,unix-pc.general
Subject: Re: non-blocking tty
Keywords: unix-pc tty000 no-cd
Message-ID: <477@umn-d-ub.D.UMN.EDU>
Date: 2 Sep 88 23:33:36 GMT
References: <168@denwa.UUCP>
Reply-To: rhealey@ub.d.umn.edu (Rob Healey)
Distribution: na
Organization: University of Minnesota, Duluth
Lines: 14

In article <168@denwa.UUCP> jimmy@denwa.UUCP (Jim Gottlieb) writes:
>Recently, someone suggested that by doing a 'mknod ttyd0 c 0 128' you
>would create a descriptor for the same line as tty000, except that it
>would not be necessary to hold CD high to communicate with the port.
	
	I can not tell a lie, I said this. I'm running 3.5, maybe that
	makes a difference? I'm pretty sure it ignored CD because a
	request on tty000 would block but ttyd0 didn't. Maybe it was
	something that made it look like ttyd0 was ignoring the CD
	line. On some BSD systems setting the high bit of the minor
	device number means a non-blocking open on the line is possible.
	Since the OS does have a few BSD 4.1 quirks I thought the assumption
	on ttyd0 was reasonable.

			-Rob