linux-kernel - Re: [PATCH v3 05/13] can: netlink: dump bitrate 0 if can

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Date:   Mon, 13 Jun 2022 22:44:12 +0200
From:   Dario Binacchi <dario.binacchi@...rulasolutions.com>
To:     Marc Kleine-Budde <mkl@...gutronix.de>
Cc:     linux-kernel@...r.kernel.org, michael@...rulasolutions.com,
        Amarula patchwork <linux-amarula@...rulasolutions.com>,
        Oliver Hartkopp <socketcan@...tkopp.net>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...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: [PATCH v3 05/13] can: netlink: dump bitrate 0 if
 can_priv::bittiming.bitrate is -1U

On Mon, Jun 13, 2022 at 9:11 AM Marc Kleine-Budde <mkl@...gutronix.de> wrote:
>
> On 12.06.2022 23:39:19, Dario Binacchi wrote:
> > Adding Netlink support to the slcan driver made it necessary to set the
> > bitrate to a fake value (-1U) to prevent open_candev() from failing. In
> > this case the command `ip --details -s -s link show' would print
> > 4294967295 as the bitrate value. The patch change this value in 0.
> >
> > Suggested-by: Marc Kleine-Budde <mkl@...gutronix.de>
> > Signed-off-by: Dario Binacchi <dario.binacchi@...rulasolutions.com>
> > ---
> >
> > (no changes since v1)
> >
> >  drivers/net/can/dev/netlink.c | 12 +++++++++---
> >  1 file changed, 9 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/net/can/dev/netlink.c b/drivers/net/can/dev/netlink.c
> > index 7633d98e3912..788a6752fcc7 100644
> > --- a/drivers/net/can/dev/netlink.c
> > +++ b/drivers/net/can/dev/netlink.c
> > @@ -505,11 +505,16 @@ static int can_fill_info(struct sk_buff *skb, const struct net_device *dev)
> >       struct can_ctrlmode cm = {.flags = priv->ctrlmode};
> >       struct can_berr_counter bec = { };
> >       enum can_state state = priv->state;
> > +     __u32 bitrate = priv->bittiming.bitrate;
> > +     int ret = 0;
> >
> >       if (priv->do_get_state)
> >               priv->do_get_state(dev, &state);
> >
> > -     if ((priv->bittiming.bitrate &&
>
> What about changing this line to:
>
>         if ((priv->bittiming.bitrate && priv->bittiming.bitrate != -1 &&

That you are right. The code becomes much cleaner.

>
> This would make the code a lot cleaner. Can you think of a nice macro
> name for the -1?
>
> 0 could be CAN_BITRATE_UNCONFIGURED or _UNSET. For -1 I cannot find a
> catchy name, something like CAN_BITRATE_CONFIGURED_UNKOWN or
> SET_UNKNOWN.
>

Personally I would use CAN_BITRATE_UNSET (0) and CAN_BITRATE_UNKNOWN (-1).
Let me know what your ultimate preference is.

Thanks and regards,
Dario

> The macros can be added to bittiming.h and be part of this patch. Ofq
> course the above code (and slcan.c) would make use of the macros instead
> of using 0 and -1.
>
> 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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