Understanding Linux Network Internals

Device Initialization

In the section "When a Device Is Registered," we saw what needs to be initialized for the kernel to communicate to the NIC. In the rest of this chapter we will look at higher-level initialization tasks.

The net_device structure is pretty big. Its fields are initialized in chunks by different routines, each one responsible for a different subset of fields.^[†] In particular:

Device drivers

Parameters such as IRQ, I/O memory, and I/O port, whose values depend on the hardware configuration, are taken care of by the device driver. See Chapter 5.

Device type

The initialization of fields common to all the devices of a device type family is taken care by the xxx _setup routines. For example, Ethernet devices use ether_setup. See the section "Device Type Initialization: xxx_setup Functions."

Features

Mandatory and optional features also need to be initialized. For example, the queuing discipline (i.e., QoS) is initialized in register_netdevice, as described in the section "register_netdevice Function." Other features can be initialized when the associated modules are notified about the registration of the new device (see the section "Device Registration Status Notification").

The device type initialization is done as part of the device driver initialization (that is, xxx _setup is called by xxx _probe) so that the driver has a chance to overwrite the default device type's initializations. See the section "Optional Initializations and Special Cases" for an example.

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