Linux Device Drivers

The device Structure in Detail

The device structure is at the very core of network drivers 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 rather 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 device can be conceptually divided into two parts: ``visible'' and ``invisible.'' The visible part of the structure is made up of the fields that are explicitly assigned in static device structures, like the two items appearing in snull and shown above. The remaining fields are used internally. Some are accessed by drivers (for example, the ones that are assigned at initialization time), while some shouldn’t be touched. This section is complete up to kernel version 2.0.30.

The Visible Head

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

char *name;

The name of the device. If the first character of the name is zero (the NUL character) or a blank, register_netdev assigns it the name eth n, with a suitable numeric n.

unsigned long rmem_end; , unsigned long rmem_start; , unsigned long mem_end; , unsigned long mem_start;

These fields hold the beginning and ending addresses of the shared memory used by the device. If the device has ...