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SubjectRe: [PATCH] add sysfs attribute 'carrier' for net devices
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On Mon, 2004-09-27 at 00:51 +0200, Jesper Juhl wrote:
> Hi,
>
> Here's a patch that adds a new sysfs attribute for net devices. The new
> attribute 'carrier' exposes the result of netif_carrier_ok() so that when
> a network device has carrier the attribute value is 1 and when there is no
> carrier the attribute value is 0.
> Very rellevant attribute for network devices in my oppinion, and sysfs is
> the logical place for it.
>
> I've tested this only on my own machine, but I get the expected results:
>
> With network cable plugged into eth0 :
>
> juhl@dragon:~$ cat /sys/class/net/eth0/carrier
> 1
> juhl@dragon:~$
>
> With network cable unplugged :
>
> juhl@dragon:~$ cat /sys/class/net/eth0/carrier
> 0
> juhl@dragon:~$
>
> Please review and consider applying.
>
> Signed-off-by: Jesper Juhl <juhl-lkml@dif.dk>
>
> diff -u linux-2.6.9-rc2-bk5-orig/net/core/net-sysfs.c linux-2.6.9-rc2-bk5/net/core/net-sysfs.c
> --- linux-2.6.9-rc2-bk5-orig/net/core/net-sysfs.c 2004-09-14 23:19:53.000000000 +0200
> +++ linux-2.6.9-rc2-bk5/net/core/net-sysfs.c 2004-09-27 00:24:01.000000000 +0200
> @@ -126,8 +126,21 @@
> return -EINVAL;
> }
>
> +static ssize_t show_carrier(struct class_device *dev, char *buf)
> +{
> + struct net_device *net = to_net_dev(dev);
> + if (netif_running(net)) {
> + if (netif_carrier_ok(net))
> + return snprintf(buf, 3, "%d\n", 1);
> + else
> + return snprintf(buf, 3, "%d\n", 0);

Using snprintf in this way is kind of silly. since buffer is PAGESIZE.
The most concise format of this would be:
return sprintf(buf, dec_fmt, !!netif_carrier_ok(dev));




> + }
> + return -EINVAL;
> +}
> +
> static CLASS_DEVICE_ATTR(address, S_IRUGO, show_address, NULL);
> static CLASS_DEVICE_ATTR(broadcast, S_IRUGO, show_broadcast, NULL);
> +static CLASS_DEVICE_ATTR(carrier, S_IRUGO, show_carrier, NULL);
>
> /* read-write attributes */
> NETDEVICE_SHOW(mtu, fmt_dec);
> @@ -186,6 +199,7 @@
> &class_device_attr_type,
> &class_device_attr_address,
> &class_device_attr_broadcast,
> + &class_device_attr_carrier,
> NULL
> };
>

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