Understanding Linux Network Internals

Registering a PCI NIC Device Driver

PCI devices are uniquely identified by a combination of parameters, including vendor, model, etc. These parameters are stored by the kernel in a data structure of type pci_device_id, defined as follows:

struct pci_device_id {
     unsigned int vendor, device;
     unsigned int subvendor, subdevice;
     unsigned int class, class_mask;
     unsigned long driver_data;
};

Most of the fields are self-explanatory. vendor and device are usually sufficient to identify the device. subvendor and subdevice are rarely needed and are usually set to a wildcard value (PCI_ANY_ID). class and class_mask represent the class the device belongs to; NETWORK is the class that covers the devices we discuss in this chapter. driver_data is not part of the PCI ID; it is a private parameter used by the driver.

Each device driver registers with the kernel a vector of pci_device_id instances that lists the IDs of the devices it can handle.

PCI device drivers register and unregister with the kernel with pci_register_driver and pci_unregister_driver, respectively. These functions are defined in drivers/pci/pci.c. There is also pci_module_init, an alias for pci_register_driver. A few drivers still use pci_module_init, which is the name of the routine the kernel provided in older kernel versions before the introduction of pci_register_driver.

pci_register_driver requires a pci_driver data structure as an argument. Thanks to the pci_driver's id_table vector, the kernel knows what devices the driver can ...