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Date: Fri, 27 Jun 1997 22:32:51 +1000
From: Bruce Evans <bde@zeta.org.au>
Message-Id: <199706271232.WAA25388@godzilla.zeta.org.au>
To: bde@zeta.org.au, mcgovern@spoon.beta.com
Subject: Re: XON/XOFF intrusion
Cc: hackers@freebsd.org
Sender: owner-hackers@freebsd.org
X-Loop: FreeBSD.org
Precedence: bulk

>However, I did note one interesting thing in tty.c (/usr/src/sys/kern), 
>starting on line 318 (version 2.2.1). Its the if statement that decides
>if ttyblock() gets called. I did some reduction of the expression,
>and got (in pseudo-code):
>
>if ( (tp clists > 512) && (!ICANON || tp->t_canq.c_cc != 0) && 
>	(CRTS_IFLOW || IXOFF) && !TS_BLOCK)
>
>I'd buy most of that as being reasonable, except the CRTS_IFLOW portion. Why
>would I want to introduce Xon/Xoff handling if I have CRTS_FLOW? Especially
>when this flag represents half of hardware flow control? I think it should

This is so that ttyblock() gets called to handle all types of flow control.

Bruce