linux-kernel - Re: [PATCH]TTY: Fix tty can't be restarted by TCXONC ioctl request

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Message-ID: <20130508171247.GA6925@udknight>
Date:	Thu, 9 May 2013 01:12:48 +0800
From:	Wang YanQing <udknight@...il.com>
To:	Peter Hurley <peter@...leysoftware.com>
Cc:	Greg KH <gregkh@...uxfoundation.org>, jslaby@...e.cz,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH]TTY: Fix tty can't be restarted by TCXONC ioctl request

On Wed, May 08, 2013 at 11:18:07AM -0400, Peter Hurley wrote:
> On 05/08/2013 09:16 AM, Wang YanQing wrote:
> > On Tue, May 07, 2013 at 07:02:00PM -0700, Greg KH wrote:
> >> What about Peter's comments on this patch?
> >>
> > Peter's comments will import policy,
> >
> > I means we should let userspace to decide whether
> > and when to restart tty with the mechanism of TCXONC
> > instead of restart tty accidental when make n_tty_set_termios
> > call.
> 
> There would be no accidental restart. Userspace is specifically
> disabling user-controlled output flow control by clearing
> IXON in termios. Userspace is _expecting_ a 'started' tty.
> 
> If you insist that this must be controllable from userspace,
> then that is already possible:
> 
> 	tcflow(fd, TCOOFF);
> 	tcflow(fd, TCOON);

Indeed you can't do what you said with TCOOFF and TCOON
if you read the codes, that's what this patch fix.

Thanks.
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