netdev - Re: [PATCH v2] net: export device speed and duplex via sysfs

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Date:	Fri, 2 Oct 2009 15:26:12 -0400
From:	Andy Gospodarek <andy@...yhouse.net>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH v2] net: export device speed and duplex via sysfs

On Fri, Oct 02, 2009 at 08:15:08PM +0200, Eric Dumazet wrote:
> Andy Gospodarek a écrit :
> > +static ssize_t show_speed(struct device *dev,
> > +			  struct device_attribute *attr, char *buf)
> > +{
> > +	struct net_device *netdev = to_net_dev(dev);
> > +	int ret = -EINVAL;
> > +
> > +	if (!rtnl_trylock())
> > +		return restart_syscall();
> > +
> > +	if (netif_running(netdev) && netdev->ethtool_ops->get_settings) {
> > +		struct ethtool_cmd cmd = { ETHTOOL_GSET };
> > +
> > +		if (netdev->ethtool_ops->get_settings(netdev, &cmd) < 0)
> 
> 		rtnl lock leak ?
> 
> 
> > +			return -EINVAL;
> > +		ret = sprintf(buf, fmt_dec, cmd.speed);
> > +	}
> > +	rtnl_unlock();
> > +	return ret;
> > +}
> > +
> > +static ssize_t show_duplex(struct device *dev,
> > +			   struct device_attribute *attr, char *buf)
> > +{
> > +	struct net_device *netdev = to_net_dev(dev);
> > +	int ret = -EINVAL;
> > +
> > +	if (!rtnl_trylock())
> > +		return restart_syscall();
> > +
> > +	if (netif_running(netdev) && netdev->ethtool_ops->get_settings) {
> > +		struct ethtool_cmd cmd = { ETHTOOL_GSET };
> > +
> > +		if (netdev->ethtool_ops->get_settings(netdev, &cmd) < 0)
> 
> 		rtnl lock leak ?
> 
> > +			return -EINVAL;
> > +		ret = sprintf(buf, "%s\n", cmd.duplex ? "full" : "half");
> > +	}
> > +	rtnl_unlock();
> > +	return ret;
> > +}
> > +
> 

Thanks for spotting that, Eric.  Here's an updated (and tested patch).
I also switched to using ethtool_cmd_speed to get link speed to get the
'entire' speed.

[PATCH] net: export device speed and duplex via sysfs

This patch exports the link-speed (in Mbps) and duplex of an interface
via sysfs.  This eliminates the need to use ethtool just to check the
link-speed.  Not requiring 'ethtool' and not relying on the SIOCETHTOOL
ioctl should be helpful in an embedded environment where space is at a
premium as well.

NOTE: This patch also intentionally allows non-root users to check the link
speed and duplex -- something not possible with ethtool.

Here's some sample output:

# cat /sys/class/net/eth0/speed 
100
# cat /sys/class/net/eth0/duplex
half
# ethtool eth0
Settings for eth0:
        Supported ports: [ TP ]
        Supported link modes:   10baseT/Half 10baseT/Full 
                                100baseT/Half 100baseT/Full 
                                1000baseT/Half 1000baseT/Full 
        Supports auto-negotiation: Yes
        Advertised link modes:  Not reported
        Advertised auto-negotiation: No
        Speed: 100Mb/s
        Duplex: Half
        Port: Twisted Pair
        PHYAD: 1
        Transceiver: internal
        Auto-negotiation: off
        Supports Wake-on: g
        Wake-on: g
        Current message level: 0x000000ff (255)
        Link detected: yes


---
 net/core/net-sysfs.c |   40 ++++++++++++++++++++++++++++++++++++++++
 1 files changed, 40 insertions(+), 0 deletions(-)

diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
index 3994680..133dbc4 100644
--- a/net/core/net-sysfs.c
+++ b/net/core/net-sysfs.c
@@ -130,6 +130,44 @@ static ssize_t show_carrier(struct device *dev,
 	return -EINVAL;
 }
 
+static ssize_t show_speed(struct device *dev,
+			  struct device_attribute *attr, char *buf)
+{
+	struct net_device *netdev = to_net_dev(dev);
+	int ret = -EINVAL;
+
+	if (!rtnl_trylock())
+		return restart_syscall();
+
+	if (netif_running(netdev) && netdev->ethtool_ops->get_settings) {
+		struct ethtool_cmd cmd = { ETHTOOL_GSET };
+
+		if (!netdev->ethtool_ops->get_settings(netdev, &cmd))
+			ret = sprintf(buf, fmt_dec, ethtool_cmd_speed(&cmd));
+	}
+	rtnl_unlock();
+	return ret;
+}
+
+static ssize_t show_duplex(struct device *dev,
+			   struct device_attribute *attr, char *buf)
+{
+	struct net_device *netdev = to_net_dev(dev);
+	int ret = -EINVAL;
+
+	if (!rtnl_trylock())
+		return restart_syscall();
+
+	if (netif_running(netdev) && netdev->ethtool_ops->get_settings) {
+		struct ethtool_cmd cmd = { ETHTOOL_GSET };
+
+		if (!netdev->ethtool_ops->get_settings(netdev, &cmd))
+			ret = sprintf(buf, "%s\n", cmd.duplex ? "full" : "half");
+	}
+	rtnl_unlock();
+	return ret;
+}
+
 static ssize_t show_dormant(struct device *dev,
 			    struct device_attribute *attr, char *buf)
 {
@@ -259,6 +297,8 @@ static struct device_attribute net_class_attributes[] = {
 	__ATTR(address, S_IRUGO, show_address, NULL),
 	__ATTR(broadcast, S_IRUGO, show_broadcast, NULL),
 	__ATTR(carrier, S_IRUGO, show_carrier, NULL),
+	__ATTR(speed, S_IRUGO, show_speed, NULL),
+	__ATTR(duplex, S_IRUGO, show_duplex, NULL),
 	__ATTR(dormant, S_IRUGO, show_dormant, NULL),
 	__ATTR(operstate, S_IRUGO, show_operstate, NULL),
 	__ATTR(mtu, S_IRUGO | S_IWUSR, show_mtu, store_mtu),
--
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