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

2014-06-02 8:01 GMT-07:00 Veaceslav Falico [off-list ref]:

On Mon, Jun 02, 2014 at 04:35:57PM +0200, Jiri Pirko wrote:

quoted

Mon, Jun 02, 2014 at 04:25:15PM CEST, mprivozn@redhat.com wrote:

quoted

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 <redacted>
---
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?

My first thoughts were exactly this. There is SPEED_UNKOWN (along with
_10, _100, _1000 etc.) that's -1, and quite a few drivers use it/set it.

I wonder, though, if we should document it or just output "Unknown" instead
of -1.

I would document the special "Unkown" value in
Documentation/ABI/testing/sysfs-class-net and update speed_show() to
handle it. -1 is confusing for anyone to realize what this means.

quoted

quoted

        }
        rtnl_unlock();
        return ret;
--
2.0.0

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-- 
Florian