PATH ADC Home > Documentation > Hardware > Device Managers and Drivers > PCI Card Services > Designing PCI Cards and Drivers for Power Macintosh Computers

Driver Interfaces

Open Firmware driver code typically supports two interfaces:

a hardware interface, through which the driver controls its associated device
a client interface, through which the driver cooperates with an operating system

Discussion of the hardware interface for Open Firmware driver code is beyond the scope of this book; it is assumed that the relation between a driver and its associated hardware is entirely controlled by the internal design of the PCI expansion card.

This book also does not try to discuss the general client interface for Open Firmware drivers, which is of interest primarily to engineers designing an operating system. For details about the specific client interface between drivers and Mac OS, see Part 3, Native Device Drivers.

The next section discusses how PCI card expansion ROMs export properties to the Open Firmware device tree. This process lets the card's Open Firmware drivers (if any) work with the Power Macintosh firmware during the computer's startup process, before an operating system is present.

IMPORTANT

To participate in the boot process, PCI expansion cards installed in Macintosh computers that support the NewWorld system architecture must include Open Firmware drivers in the PCI card expansion ROM.