[dpdk-dev] Questions about rte_eth_link_speed_to_str API

[Stephen Hemminger]

On Tue, 14 Sep 2021 11:25:44 +0800
"Min Hu (Connor)" <humin29 at huawei.com> wrote:

> Thanks Thomas,
> 	I am not sure if we need to  print combined slaves speed.
> 	How about others' opinion ? @all
> 
> 	BTW, If yes, one possible option may be like that:
> +const char *
> +rte_eth_link_speed_to_str(uint32_t link_speed)
> +{
> +	char name[16];
> +
> +	if (link_speed == ETH_SPEED_NUM_NONE)
> +		return "None";
> +	if (link_speed == ETH_SPEED_NUM_NONE)
> +		return "Unknown";
> +	if (link_speed < ETH_SPEED_NUM_1G) {
> +		snprintf(name, sizeof(name), "%u Mbps", link_speed);
> +	} else {
> +		snprintf(name, sizeof(name), "%u Mbps",
> +			link_speed / ETH_SPEED_NUM_1G);
> +	}
> +
> +	return name;
> +}
> 
> But the float value is difficult to handle, like 2.5 Gbps for show. Any 
> advices?
> 
> 在 2021/9/13 18:26, Thomas Monjalon 写道:
> > 13/09/2021 10:45, Min Hu (Connor):  
> >> Hi all,
> >> 	I have questions about rte_eth_link_speed_to_str API.
> >> 	The API converts link speed to string for display, But it only
> >> supports the following speeds, like that:
> >> 	case ETH_SPEED_NUM_NONE: return "None";
> >> 	case ETH_SPEED_NUM_10M:  return "10 Mbps";
> >> 	case ETH_SPEED_NUM_100M: return "100 Mbps";
> >> 	case ETH_SPEED_NUM_1G:   return "1 Gbps";
> >> 	case ETH_SPEED_NUM_2_5G: return "2.5 Gbps";
> >> 	case ETH_SPEED_NUM_5G:   return "5 Gbps";
> >> 	case ETH_SPEED_NUM_10G:  return "10 Gbps";
> >> 	case ETH_SPEED_NUM_20G:  return "20 Gbps";
> >> 	case ETH_SPEED_NUM_25G:  return "25 Gbps";
> >> 	case ETH_SPEED_NUM_40G:  return "40 Gbps";
> >> 	case ETH_SPEED_NUM_50G:  return "50 Gbps";
> >> 	case ETH_SPEED_NUM_56G:  return "56 Gbps";
> >> 	case ETH_SPEED_NUM_100G: return "100 Gbps";
> >> 	case ETH_SPEED_NUM_200G: return "200 Gbps";
> >> 	case ETH_SPEED_NUM_UNKNOWN: return "Unknown";
> >> 	default: return "Invalid";
> >>
> >> 	In some cases, like bonding, for example, three slaves which
> >> 	link speed are 10Gbps, so link speed of bonding port will be
> >> 	30Gbps, but it shows "Invalid".
> >>
> >> 	Is this reasonable？ any comments will be welcome.  
> > 
> > Is it meaningful to print combined slaves speed?
> > If yes, we can do better then this fixed switch/case logic,
> > it shouldn't be too hard given it is a standard uint32_t value.
> > 
> > 
> > .
> >   

Since all the values are encoded numerically do some math.
This is what iproute2 has evolved to doing..


int print_color_rate(bool use_iec, enum output_type type, enum color_attr color,
                     const char *key, const char *fmt, unsigned long long rate)
{
        unsigned long kilo = use_iec ? 1024 : 1000;
        const char *str = use_iec ? "i" : "";
        static char *units[5] = {"", "K", "M", "G", "T"};
        char *buf;
        int rc;
        int i;

        if (_IS_JSON_CONTEXT(type))
                return print_color_lluint(type, color, key, "%llu", rate);

        rate <<= 3; /* bytes/sec -> bits/sec */

        for (i = 0; i < ARRAY_SIZE(units) - 1; i++)  {
                if (rate < kilo)
                        break;
                if (((rate % kilo) != 0) && rate < 1000*kilo)
                        break;
                rate /= kilo;
        }

        rc = asprintf(&buf, "%.0f%s%sbit", (double)rate, units[i],
                      i > 0 ? str : "");
        if (rc < 0)
                return -1;

        rc = print_color_string(type, color, key, fmt, buf);
        free(buf);
}