linux-kernel - Re: [PATCH v6] can, tty: can327 CAN/ldisc driver for ELM327 based OBD-II adapters

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Date:   Fri, 13 May 2022 21:14:53 +0900
From:   Vincent Mailhol <vincent.mailhol@...il.com>
To:     Marc Kleine-Budde <mkl@...gutronix.de>
Cc:     Max Staudt <max@...as.org>,
        Wolfgang Grandegger <wg@...ndegger.com>,
        linux-can@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Oliver Neukum <oneukum@...e.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6] can, tty: can327 CAN/ldisc driver for ELM327 based
 OBD-II adapters

On Fri 13 May 2022 at 20:52, Marc Kleine-Budde <mkl@...gutronix.de> wrote:
> On 13.05.2022 11:38:31, Vincent Mailhol wrote:
> > > +
> > > +       /* We shouldn't get here after a hardware fault:
> > > +        * can_bus_off() calls netif_carrier_off()
> > > +        */
> > > +       WARN_ON_ONCE(elm->uart_side_failure);
> > > +
> > > +       if (!elm->tty ||
> > > +           elm->uart_side_failure ||
> > > +           elm->can.ctrlmode & CAN_CTRLMODE_LISTENONLY) {
> >
> > Can the xmit function get called when CAN_CTRLMODE_LISTENONLY is on?
>
> I think yes. You can skip the whole CAN stack by injecting CAN frames in
> the kernel via the packet socket. Maybe we should add a check to
> can_dropped_invalid_skb().

Ack. Most of the drivers do not check for it (my doesn't). So better
to put it in can_dropped_invalid_skb().
I can do the patch for this.

And also noted for your previous comment on lockdep_assert_held().
@Max: please ignore this particular remark.