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

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Message-ID: <20220613071058.h6bmy6emswh76q5s@pengutronix.de>
Date:   Mon, 13 Jun 2022 09:10:58 +0200
From:   Marc Kleine-Budde <mkl@...gutronix.de>
To:     Dario Binacchi <dario.binacchi@...rulasolutions.com>
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 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 &&

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.

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 |

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