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Date:   Thu, 6 May 2021 08:50:35 -0700
From:   Stephen Hemminger <stephen@networkplumber.org>
To:     Vincent Mailhol <mailhol.vincent@wanadoo.fr>
Cc:     Marc Kleine-Budde <mkl@pengutronix.de>, linux-can@vger.kernel.org,
        Oliver Hartkopp <socketcan@hartkopp.net>,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH v1 1/1] iplink_can: add new CAN FD bittiming
 parameters: Transmitter Delay Compensation (TDC)
Message-ID: <20210506085035.2fc33bf3@hermes.local>
In-Reply-To: <20210506112007.1666738-2-mailhol.vincent@wanadoo.fr>
References: <20210506112007.1666738-1-mailhol.vincent@wanadoo.fr>
        <20210506112007.1666738-2-mailhol.vincent@wanadoo.fr>
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On Thu,  6 May 2021 20:20:07 +0900
Vincent Mailhol <mailhol.vincent@wanadoo.fr> wrote:

> +	if (tb[IFLA_CAN_TDC_TDCV] && tb[IFLA_CAN_TDC_TDCO] &&
> +	    tb[IFLA_CAN_TDC_TDCF]) {
> +		__u32 *tdcv = RTA_DATA(tb[IFLA_CAN_TDC_TDCV]);
> +		__u32 *tdco = RTA_DATA(tb[IFLA_CAN_TDC_TDCO]);
> +		__u32 *tdcf = RTA_DATA(tb[IFLA_CAN_TDC_TDCF]);
> +
> +		if (is_json_context()) {
> +			open_json_object("tdc");
> +			print_int(PRINT_JSON, "tdcv", NULL, *tdcv);
> +			print_int(PRINT_JSON, "tdco", NULL, *tdco);
> +			print_int(PRINT_JSON, "tdcf", NULL, *tdcf);
> +			close_json_object();
> +		} else {
> +			fprintf(f, "\n	  tdcv %d tdco %d tdcf %d",
> +				*tdcv, *tdco, *tdcf);
> +		}
> +	}
> +

The most common pattern in iproute2 is to let json/non-json be decided
inside the print routine.  I search for all instances of fprintf as
indication of broken code. Also these are not signed values so please
print unsigned.  The code should use print_nl() to handle the single line
case. Also, there is helper to handle 

Something like:
              __u32 tdc = rte_getattr_u32(tb[IFLA_CAN_TDC_TDCV]);

		open_json_object("tdc");
		print_nl();
		print_u32(PRINT_ANY, "tdcv", "    tdcv %u", tdcv);
...