netdev - [RFC] managing PHY carrier from user space

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Message-ID: <2fcf4c20a9adf410db98706f6f2508e46aade2c1.camel@infinera.com>
Date:   Tue, 11 Sep 2018 16:41:48 +0000
From:   Joakim Tjernlund <Joakim.Tjernlund@...inera.com>
To:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "f.fainelli@...il.com" <f.fainelli@...il.com>,
        "andrew@...n.ch" <andrew@...n.ch>
Subject: [RFC] managing PHY carrier from user space

I am looking for a way to induce carrier state from user space, primarily
for Fixed PHYs as these are always up. ifplugd/dhcp etc. does not behave properly
if the link is up when it really isn't.

I came up with a new 'phy_carrier' attribute in /sys/class/net/eth0/phydev
where I can induce carrier state:

diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
index a1e7ea4d4b16..f82beeabdd75 100644
--- a/drivers/net/phy/phy_device.c
+++ b/drivers/net/phy/phy_device.c
@@ -612,10 +612,39 @@ phy_has_fixups_show(struct device *dev, struct device_attribute *attr,
 }
 static DEVICE_ATTR_RO(phy_has_fixups);
 
+static ssize_t
+phy_carrier_show(struct device *dev, struct device_attribute *attr,
+                char *buf)
+{
+       struct phy_device *phydev = to_phy_device(dev);
+       struct net_device *netdev = phydev->attached_dev;
+
+       return sprintf(buf, "%d\n", netif_carrier_ok(netdev));
+}
+
+static ssize_t phy_carrier_store(struct device *dev, struct device_attribute *attr,
+                                const char *buf, size_t len)
+{
+       struct phy_device *phydev = to_phy_device(dev);
+       struct net_device *netdev = phydev->attached_dev;
+       bool enable;
+
+       if (strtobool(buf, &enable))
+               return -EINVAL;
+
+       if (enable)
+               netif_carrier_on(netdev);
+       else
+               netif_carrier_off(netdev);
+       return len;
+}
+static DEVICE_ATTR_RW(phy_carrier);
+
 static struct attribute *phy_dev_attrs[] = {
        &dev_attr_phy_id.attr,
        &dev_attr_phy_interface.attr,
        &dev_attr_phy_has_fixups.attr,
+       &dev_attr_phy_carrier.attr,
        NULL,
 };
 ATTRIBUTE_GROUPS(phy_dev);

I would like to know if this acceptable for linux proper or if there is
a better way to do this?

 Jocke