linux-kernel - Re: [RFC PATCH 5/5] can: slcan: send the listen-only command to the adapter

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Date:   Thu, 21 Jul 2022 10:17:15 +0200
From:   Dario Binacchi <dario.binacchi@...rulasolutions.com>
To:     Marc Kleine-Budde <mkl@...gutronix.de>
Cc:     linux-kernel@...r.kernel.org,
        Jeroen Hofstee <jhofstee@...tronenergy.com>,
        michael@...rulasolutions.com,
        Amarula patchwork <linux-amarula@...rulasolutions.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jakub Kicinski <kuba@...nel.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Vincent Mailhol <mailhol.vincent@...adoo.fr>,
        Wolfgang Grandegger <wg@...ndegger.com>,
        linux-can@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [RFC PATCH 5/5] can: slcan: send the listen-only command to the adapter

Hello Marc,

On Mon, Jul 18, 2022 at 12:22 PM Marc Kleine-Budde <mkl@...gutronix.de> wrote:
>
> The subject can be enhanced, as the listen-only command ist not send
> unconditionally. What about: "add support for listen-only mode"?

I like it.

>
> On 16.07.2022 19:00:07, Dario Binacchi wrote:
> > In case the bitrate has been set via ip tool, this patch changes the
> > driver to send the listen-only ("L\r") command to the adapter.
>
> ...but only of CAN_CTRLMODE_LISTENONLY is requested.
>
> What about:
>
> For non-legacy, i.e. ip based configuration, add support for listen-only
> mode. If listen-only is requested send a listen-only ("L\r") command
> instead of an open ("O\r") command to the adapter..

I agree with you. It's definitely clearer.

Thanks and regards,
Dario
>
> >
> > Signed-off-by: Dario Binacchi <dario.binacchi@...rulasolutions.com>
> >
> > ---
> >
> >  drivers/net/can/slcan/slcan-core.c | 20 ++++++++++++++++----
> >  1 file changed, 16 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/net/can/slcan/slcan-core.c b/drivers/net/can/slcan/slcan-core.c
> > index 7a1540507ecd..d97dfeccbf9c 100644
> > --- a/drivers/net/can/slcan/slcan-core.c
> > +++ b/drivers/net/can/slcan/slcan-core.c
> > @@ -711,10 +711,21 @@ static int slcan_netdev_open(struct net_device *dev)
> >                       }
> >               }
> >
> > -             err = slcan_transmit_cmd(sl, "O\r");
> > -             if (err) {
> > -                     netdev_err(dev, "failed to send open command 'O\\r'\n");
> > -                     goto cmd_transmit_failed;
> > +             /* listen-only command overrides open command */
>
> I think this comment can be removed.
>
> > +             if (sl->can.ctrlmode & CAN_CTRLMODE_LISTENONLY) {
> > +                     err = slcan_transmit_cmd(sl, "L\r");
> > +                     if (err) {
> > +                             netdev_err(dev,
> > +                                        "failed to send listen-only command 'L\\r'\n");
> > +                             goto cmd_transmit_failed;
> > +                     }
> > +             } else {
> > +                     err = slcan_transmit_cmd(sl, "O\r");
> > +                     if (err) {
> > +                             netdev_err(dev,
> > +                                        "failed to send open command 'O\\r'\n");
> > +                             goto cmd_transmit_failed;
> > +                     }
> >               }
> >       }
> >
> > @@ -801,6 +812,7 @@ static int slcan_open(struct tty_struct *tty)
> >       /* Configure CAN metadata */
> >       sl->can.bitrate_const = slcan_bitrate_const;
> >       sl->can.bitrate_const_cnt = ARRAY_SIZE(slcan_bitrate_const);
> > +     sl->can.ctrlmode_supported = CAN_CTRLMODE_LISTENONLY;
> >
> >       /* Configure netdev interface */
> >       sl->dev = dev;
>
> Marc
>
> --
> Pengutronix e.K.                 | Marc Kleine-Budde           |
> Embedded Linux                   | https://www.pengutronix.de  |
> Vertretung West/Dortmund         | Phone: +49-231-2826-924     |
> Amtsgericht Hildesheim, HRA 2686 | Fax:   +49-5121-206917-5555 |



-- 

Dario Binacchi

Embedded Linux Developer

dario.binacchi@...rulasolutions.com

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