Linux Device Drivers

Chapter 15. Overview of Peripheral Buses

While 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, I’m going to 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, and the one that is best supported by the kernel.

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. I’m not going to cover it all here; in this section I’m 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 9.2.2 in Chapter 9, can be used with PCI devices, but the specification offers an alternative to probing.

The PCI architecture was designed as a replacement for the ISA standard, with three main goals: to get better performance when transferring data between the computer and its peripherals, to be as platform-independent as possible, and to simplify adding and removing peripherals to ...