How to automatically start a USB ethernet interface with smsc95xx driver

Question

I'm using a custom board with a LAN9514 and the smsc95xx driver, but cannot get the ethernet interface to come up automatically at boot time. Once the system starts, I can use "ifconfig eth1 up" to bring it up, but I want it started automatically.

Here is my /etc/network/interfaces:

auto lo
iface lo inet loopback

auto eth0
iface eth0 inet static
address 192.168.1.1
netmask 255.255.255.0

allow-hotplug eth1
iface eth1 inet static
address 192.168.2.1
netmask 255.255.255.0

I've also tried "auto eth1" to no avail.

Shortly after boot completes I see these messages on the console:

usb 1-1.1: new high-speed USB device number 3 using ci_hdrc
smsc95xx v1.0.6
smsc95xx 1-1.1:1.0 eth1: register 'smsc95xx' at usb-ci_hdrc.0-1.1, smsc95xx USB 2.0 Ethernet, b2:6c:a9:0e:67:34
macb e000b000.ethernet eth0: link up (1000/Full)
IPv6: ADDRCONF(NETDEV_CHANGE): eth0: link becomes ready

The /etc/init.d script to start networking uses "/sbin/ifup -a" to enable startup of automatic interfaces (ifup is handled BusyBox in my system).

I can bring the interface up automatically by spawning a command with a delay in an init.d script: "sleep 5 && ifconfig eth1 up &", but that feels like a kludge because I don't know how long it can take for the USB ethernet device to be instantiated.

Running ifconfig shows interfaces lo and eth0, but not eth1 until I manually start it. What am I missing to have eth1 start automatically?

Answer 1

If you use udevd, you can use it to bring up the interface as soon is it is available. Busybox also contains an udev implementation.

Answer 2

It looks like eth0 comes up after ifup -a has already been run, because apparently it takes some time to initialize it.

So try adding allow-hotplug eth0 before auto eth0, that should tell ifup/ifdown to also enable the interface after ifup -a has already been run, when the kernel generates an event once it becomes ready.