linux-kernel - Re: question on tty open and close

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Message-Id: <1175093681.5815.145.camel@violet>
Date:	Wed, 28 Mar 2007 16:54:41 +0200
From:	Marcel Holtmann <marcel@...tmann.org>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
Cc:	Paul Fulghum <paulkf@...rogate.com>,
	Stuart MacDonald <stuartm@...necttech.com>,
	"'Oliver Neukum'" <oliver@...kum.org>, linux-kernel@...r.kernel.org
Subject: Re: question on tty open and close

Hi Alan,

> > As long as the new behavior continues to call
> > driver->close() if driver->open() succeeds
> > then I see no problem.
> 
> It breaks if any existing driver is doing no cleanup in ->open() when it
> fails but relying upon ->close() being called. That is what needs
> auditing first of all.

I know at least that the Bluetooth TTY emulation (RFCOMM) will break
since I have a big fat warning in my code:

        /* We don't leak this refcount. For reasons which are not entirely
           clear, the TTY layer will call our ->close() method even if the
           open fails. We decrease the refcount there, and decreasing it
           here too would cause breakage. */
        dev = rfcomm_dev_get(id);
        if (!dev)
                return -ENODEV;

Regards

Marcel


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