Re: [PATCH] net-sysfs: Report link speed as signed integer

[Michal Privoznik]

On 02.06.2014 16:35, Jiri Pirko wrote:
> Mon, Jun 02, 2014 at 04:25:15PM CEST, mprivozn@xxxxxxxxxx wrote:
> > The link speed is available at /sys/class/net/$nic/speed.
> > However, the speed is printed in unsigned integer format. This
> > makes userspace applications read an incorrect value (which
> > moreover changes through several architectures) while in fact
> > '-1' should be reported.
> >
> > Before the change:
> >   # cat /sys/class/net/eth0/speed
> >   4294967295
> >
> > After the change:
> >   # cat /sys/class/net/eth0/speed
> >   -1
> >
> > Signed-off-by: Michal Privoznik <mprivozn@xxxxxxxxxx>
> > ---
> > net/core/net-sysfs.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
> > index 1cac29e..99afdea 100644
> > --- a/net/core/net-sysfs.c
> > +++ b/net/core/net-sysfs.c
> > @@ -173,7 +173,7 @@ static ssize_t speed_show(struct device *dev,
> > 	if (netif_running(netdev)) {
> > 		struct ethtool_cmd cmd;
> > 		if (!__ethtool_get_settings(netdev, &cmd))
> > -			ret = sprintf(buf, fmt_udec, ethtool_cmd_speed(&cmd));
> > +			ret = sprintf(buf, fmt_dec, ethtool_cmd_speed(&cmd));
>
> I wonder why this should be signed. What -1 means? What driver reports
> this?

This is e1000e. It seems like a default value. From e1000_get_settings() 
in drivers/net/ethernet/intel/e1000e/ethtool.c:

    speed = -1;
    ecmd->duplex = -1;

    if (netif_running(netdev)) {
        if (netif_carrier_ok(netdev)) {
            speed = adapter->link_speed;
            ecmd->duplex = adapter->link_duplex - 1;
        }
    } else if (!pm_runtime_suspended(netdev->dev.parent)) {
	...
    }

    ethtool_cmd_speed_set(ecmd, speed);

If I unplug the cord, NIC is nor running nor runtime suspended.

Michal
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