From mboxrd@z Thu Jan  1 00:00:00 1970
From: Grant Edwards <grant.b.edwards@gmail.com>
Subject: Re: tcflow(TCOON/TCOOFF) vs. received XON/XOFF characters
Date: Thu, 17 Jul 2014 14:03:17 +0000 (UTC)
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On 2014-07-17, Peter Hurley <peter@hurleysoftware.com> wrote:

> tcflow(TCOxxx) flow control is independent of IXON flow control.
> The union of both flow states determines if the tty can output;
>
>                       IXON = true        IXON = false
>                    START       STOP
> tcflow(TCOON)      on         off          on
> tcflow(TCOOFF)     off        off          off

Thanks, that's pretty much what I had decided based on tests and
browsing the source code.

Just to confirm:

  tcflow(TCION/TCIOFF): overrides the "input" side of xon/xoff flow
                        control and forces the sending of XON/XOFF.

  tcflow(TCOON/TCOOFF): does not have anything to do with the "output"
                        side of xon/xoff flow control, but controls
                        something completely orthogonal.

That rather counter-intuitive (not that counter-intuitive is exactly a
novel thing when it comes to Unix serial ports).
                        
That rasies this question: what does an application use to control the
"output" side of xon/xoff flow control?  There is a Windows API for
doing that, and I get asked how to do it in Linux.  I always tell them
they can't.

-- 
Grant Edwards               grant.b.edwards        Yow! Oh, I get it!!
                                  at               "The BEACH goes on", huh,
                              gmail.com            SONNY??