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From: Johan Hovold <johan@kernel.org>
To: Mychaela Falconia <mychaela.falconia@gmail.com>
Cc: Johan Hovold <johan@kernel.org>, linux-usb@vger.kernel.org
Subject: Re: [PATCH 0/3] a family of FTDI-based devices that need ftdi_sio quirks
Date: Tue, 1 Dec 2020 10:00:56 +0100	[thread overview]
Message-ID: <X8YGSJWzOlIFfHjx@localhost> (raw)
In-Reply-To: <CA+uuBqaUqkVQ0JCS-_OMT3tApxswHDFCpXjrPFzftn2VEGAjVg@mail.gmail.com>

On Mon, Nov 30, 2020 at 12:15:51PM -0800, Mychaela Falconia wrote:

> > I'm adding a new tty port flag that can be used to suppress the
> > assertion of DTR/RTS to signal DTE readiness on open named NORDY.
> > Eventually we can expose it through termios to match HUPCL that controls
> > the behaviour on final close. For now I'm only adding a sysfs interface
> > but that also allows control over these signals on first open.
> 
> I don't see how exposing this new flag via termios would be of any use
> (it's a chicken and egg problem: one needs to open the tty device in
> order to do termios ioctls on it, and if that initial open triggers
> DTR/RTS hardware actions, then the end user is still screwed), but
> making this flag accessible for setting and clearing via sysfs is a
> good idea.

Yeah, as I mentioned in the other thread a termios flag would not be
sufficient for your use case, but there could be other applications that
are more tolerant but still want control after first open.

I believe this is also the way Win32, which you referred to earlier,
works.

Johan

      reply	other threads:[~2020-12-01  9:28 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-16  1:56 [PATCH 0/3] a family of FTDI-based devices that need ftdi_sio quirks Mychaela N. Falconia
2020-09-29 10:13 ` Johan Hovold
2020-09-29 19:40   ` Mychaela Falconia
2020-10-05 10:57     ` Johan Hovold
2020-10-05 20:02       ` Mychaela Falconia
2020-10-27 20:18         ` Mychaela Falconia
2020-10-28  7:17           ` Johan Hovold
2020-11-30 15:13         ` Johan Hovold
2020-11-30 20:15           ` Mychaela Falconia
2020-12-01  9:00             ` Johan Hovold [this message]

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