Networking and Ethernet devices

USB Ethernet adaptors

USB Ethernet adaptors are commonly available, and provide a simple way to add Ethernet to an STMicroelectronics system. There are two main chip sets used; based on either an ASIX^® chip or a Pegasus chip. Of these two, the ASIX is more common and offers better performance as it is USB2; Pegasus is the older USB1.

Support for USB Ethernet adaptors must be configured in the same way as keyboard support (see Kernel configuration). Bring up the Linux Kernel Configuration screen and enter:

Device Drivers ---> USB Support ---> USB Network Adapters ---> ASIX AX88172 Based USB 2.0 Ethernet Devices

or

Device Drivers ---> USB Support ---> USB Network Adapters ---> USB Pegasus/Pegasus-II based ethernet device support

This sets either CONFIG_USB_AX8817X or CONFIG_USB_PEGASUS.

When the USB adaptor is plugged in, a message similar to this should appear:

eth1: register usbnet at usb-STB7100_ehci_bus-1.3, ASIX AX8817x USB 2.0 Ethernet

The network can be configured as any other network using ifconfig.

Using a USB Ethernet adaptor with an NFS root file system

It is possible to use USB Ethernet to access a root file system over NFS. However it takes a few seconds for the USB subsystem to identify the ethernet adaptor and make it ready for use. This happens asynchronously to the main kernel booting, so the kernel may try to configure the Ethernet device before the USB subsystem is ready. The solution to this is to pass a kernel command line option ipconfdelay=<sec>, where <sec> is the number of seconds to delay before attempting to configure the Ethernet adaptor.