Linux Device Drivers, Second Edition

Chapter 15. Overview of Peripheral Buses

Whereas Chapter 8 introduced the lowest levels of hardware control, this chapter provides an overview of the higher-level bus architectures. A bus is made up of both an electrical interface and a programming interface. In this chapter, we deal with the programming interface.

This chapter covers a number of bus architectures. However, the primary focus is on the kernel functions that access PCI peripherals, because these days the PCI bus is the most commonly used peripheral bus on desktops and bigger computers, and the one that is best supported by the kernel. ISA is still common for electronic hobbyists and is described later, although it is pretty much a bare-metal kind of bus and there isn’t much to say in addition to what is covered in Chapter 8 and Chapter 9.

The PCI Interface

Although many computer users think of PCI (Peripheral Component Interconnect) as a way of laying out electrical wires, it is actually a complete set of specifications defining how different parts of a computer should interact.

The PCI specification covers most issues related to computer interfaces. We are not going to cover it all here; in this section we are mainly concerned with how a PCI driver can find its hardware and gain access to it. The probing techniques discussed in Section 2.6 in Chapter 2, and Section 9.3.2 in Chapter 9 can be used with PCI devices, but the specification offers a preferable alternative to probing.

The PCI architecture was designed ...