netdev - Re: [PATCH ethtool v4 2/6] Add cable test TDR support

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Date:   Sun, 5 Jul 2020 01:58:16 +0200
From:   Michal Kubecek <mkubecek@...e.cz>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     netdev <netdev@...r.kernel.org>, Chris Healy <cphealy@...il.com>
Subject: Re: [PATCH ethtool v4 2/6] Add cable test TDR support

On Wed, Jul 01, 2020 at 03:07:39AM +0200, Andrew Lunn wrote:
> Add support for accessing the cable test time domain reflectromatry
> data. Add a new command --cable-test-tdr, and support for dumping the
> data which is returned.
> 
> Signed-off-by: Andrew Lunn <andrew@...n.ch>
> ---

Looks good to me, only three minor issues:

> --- a/ethtool.c
> +++ b/ethtool.c
> @@ -5487,6 +5487,14 @@ static const struct option args[] = {
>  		.nlfunc	= nl_cable_test,
>  		.help	= "Perform a cable test",
>  	},
> +	{
> +		.opts	= "--cable-test-tdr",
> +		.nlfunc	= nl_cable_test_tdr,
> +		.help	= "Print cable test time domain reflectrometery data",
> +		.xhelp	= "		[ first N ]\n"
> +			  "		[ last N ]\n"
> +			  "		[ step N ]\n"

The "pair" parameter is missing here.

> +	},
>  	{
>  		.opts	= "-h|--help",
>  		.no_dev	= true,
[...]
> diff --git a/netlink/monitor.c b/netlink/monitor.c
> index 1af11ee..280fd0b 100644
> --- a/netlink/monitor.c
> +++ b/netlink/monitor.c
> @@ -63,6 +63,10 @@ static struct {
>  		.cmd	= ETHTOOL_MSG_CABLE_TEST_NTF,
>  		.cb	= cable_test_ntf_cb,
>  	},
> +	{
> +		.cmd	= ETHTOOL_MSG_CABLE_TEST_TDR_NTF,
> +		.cb	= cable_test_tdr_ntf_cb,
> +	},
>  };
>  

Please add also an entry to monitor_opts[] to allow filtering monitor
events.

[...]
> diff --git a/netlink/parser.c b/netlink/parser.c
> index bd3526f..67134f1 100644
> --- a/netlink/parser.c
> +++ b/netlink/parser.c
[...]
> @@ -211,6 +227,32 @@ int nl_parse_direct_u8(struct nl_context *nlctx, uint16_t type,
>  	return (type && ethnla_put_u8(msgbuff, type, val)) ? -EMSGSIZE : 0;
>  }
>  
> +/* Parser handler for float meters and convert it to cm. Generates
> + * NLA_U32 or fills an uint32_t.
> + */
> +int nl_parse_direct_m2cm(struct nl_context *nlctx, uint16_t type,
> +			 const void *data, struct nl_msg_buff *msgbuff,
> +			 void *dest)
> +{
> +	const char *arg = *nlctx->argp;
> +	float meters;
> +	uint32_t cm;
> +	int ret;
> +
> +	nlctx->argp++;
> +	nlctx->argc--;
> +	ret = parse_float(arg, &meters, 0, 150);
> +	if (ret < 0) {
> +		parser_err_invalid_value(nlctx, arg);
> +		return ret;
> +	}
> +
> +	cm = (uint32_t)(meters * 100);

When I tried to test the generated requests, I noticed that e.g. "20.3"
was sent as 2029 rather than 2030. It's unlikely to cause an actual
problem but we should probably use e.g.

	cm = (uint32_t)(meters * 100 + 0.5);

to prevent such rounding errors.

Michal

> +	if (dest)
> +		*(uint32_t *)dest = cm;
> +	return (type && ethnla_put_u32(msgbuff, type, cm)) ? -EMSGSIZE : 0;
> +}
> +
>  /* Parser handler for (tri-state) bool. Expects "name on|off", generates
>   * NLA_U8 which is 1 for "on" and 0 for "off".
>   */