Linux Device Drivers, Second Edition

The net_device Structure in Detail

The net_device structure is at the very core of the network driver layer and deserves a complete description. At a first reading, however, you can skip this section, because you don’t need a thorough understanding of the structure to get started. This list describes all the fields, but more to provide a reference than to be memorized. The rest of this chapter briefly describes each field as soon as it is used in the sample code, so you don’t need to keep referring back to this section.

struct net_device can be conceptually divided into two parts: visible and invisible. The visible part of the structure is made up of the fields that can be explicitly assigned in static net_device structures. All structures in drivers/net/Space.c are initialized in this way, without using the tagged syntax for structure initialization. The remaining fields are used internally by the network code and usually are not initialized at compilation time, not even by tagged initialization. Some of the fields are accessed by drivers (for example, the ones that are assigned at initialization time), while some shouldn’t be touched.

The Visible Head

The first part of struct net_device is composed of the following fields, in this order:

char name[IFNAMSIZ];

The name of the device. If the name contains a %d format string, the first available device name with the given base is used; assigned numbers start at zero.

unsigned long rmem_end; , unsigned long rmem_start; ,