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Date: Sun, 25 Mar 2012 19:31:14 +0100
From: Al Viro <viro@ZenIV.linux.org.uk>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Richard Weinberger <richard@nod.at>, Jiri Slaby <jslaby@suse.cz>,
        linux-kernel@vger.kernel.org, gregkh@linuxfoundation.org,
        Jiri Slaby <jirislaby@gmail.com>
Subject: Re: TTY: tty_port questions
Message-ID: <20120325183114.GM6589@ZenIV.linux.org.uk>
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How is tty_port supposed to work wrt hotplug?  I.e. are those guys (OK,
the structures they are embedded into) supposed to live as long as
tty_driver lives?  AFAICS, for serial we have an extra layer atop of
those guys (uart_port) and that's where removals seem to act, but there
seems to be more to it...

Suppose we handle uml reconfig requests as port removal + port addition;
what's needed to make sure that port is out of use and we can play with
it without stepping on anyone's toes?  Something along the lines of what
uart_remove_one_port() is doing?  I.e. tty_unregister_device() + tty_vhangup()?
But serial_core seems to be open-coding tty_port_open() for some reason
and _there_ we have port->count updates under port->mutex, so the
situation might be different...

Is there any FMtoR/thread/search terms that would give the description of
the situation?