The tty may be closed already when the read/write callbacks are called.
This patch checks that the ttys still exist before waking them up.
Signed-off-by: NOlivier Blin <blino@mandriva.com>
Acked-by: NAlan Cox <alan@redhat.com>
Cc: Jari Tenhunen <jari.tenhunen@iki.fi>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: NJeff Garzik <jgarzik@redhat.com>

This driver is for a number of different Option devices.  Originally
written by Option and Andrew Bird, but cleaned up massivly for
acceptance into mainline by me and others.

Many thanks to the following for their help in cleaning up the driver by
providing feedback and patches to it:
	- Paulius Zaleckas <paulius.zaleckas@teltonika.lt>
	- Oliver Neukum <oliver@neukum.org>
	- Alan Cox <alan@lxorguk.ukuu.org.uk>
	- Javier Marcet <javier@krausbeck.org>

Cc: Andrew Bird <ajb@spheresystems.co.uk>
Cc: Javier Marcet <javier@krausbeck.org>
Cc: Filip Aben <f.aben@option.com>
Cc: Paulius Zaleckas <paulius.zaleckas@teltonika.lt>
Cc: Oliver Neukum <oliver@neukum.org>
Acked-by: NAlan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: NJeff Garzik <jgarzik@redhat.com>