linux-kernel - Should .dtr_rts do tty_port_tty

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Message-ID: <4D8C7253.3040204@suse.cz>
Date:	Fri, 25 Mar 2011 11:45:39 +0100
From:	Jiri Slaby <jslaby@...e.cz>
To:	Greg KH <gregkh@...e.de>
CC:	Alan Cox <alan@...rguk.ukuu.org.uk>, linux-serial@...r.kernel.org,
	LKML <linux-kernel@...r.kernel.org>,
	Jiri Slaby <jirislaby@...il.com>
Subject: Should .dtr_rts do tty_port_tty_get?

Hi,

I'm playing with a serial device and got a nice oops. Maybe after some
weird stty's, I don't know. But it dies in uart_dtr_rts:
        .loc 1 1535 0
        movq    (%rbx), %r13    # port_1(D)->tty, D.26746
...
        .loc 1 1494 0
        testb   $2, 224(%r13)   #, D.26746_10->flags
                    ^^^^^^^^^
                      HERE

Because r13 (port->tty) is NULL. So the question is about the principle.
Should it call tty_port_tty_get or is it a bug in the TTY layer and
uart_dtr_rts should not be called with port->tty == NULL?

I'll attach a patch which does the former as a reply to this message.

BTW only serial_core needs tty in dtr_rts.

thanks,
-- 
js
suse labs
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