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

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Date:	Mon, 2 Jun 2014 17:01:50 +0200
From:	Veaceslav Falico <vfalico@...hat.com>
To:	Jiri Pirko <jiri@...nulli.us>
Cc:	Michal Privoznik <mprivozn@...hat.com>, davem@...emloft.net,
	gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org
Subject: Re: [PATCH] net-sysfs: Report link speed as signed integer

On Mon, Jun 02, 2014 at 04:35:57PM +0200, Jiri Pirko wrote:
>Mon, Jun 02, 2014 at 04:25:15PM CEST, mprivozn@...hat.com 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@...hat.com>
>>---
>> 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.

>
>> 	}
>> 	rtnl_unlock();
>> 	return ret;
>>--
>>2.0.0
>>
>--
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