Plug and Play BIOS Specification

Plug and Play BIOS Specification 1.0A Page 23
4.0 Configuration Support ________________________
A Plug and Play system BIOS, in addition to providing a conflict free bootstrap process, also provides
services to the operating system to assist with resource management during runtime. These services focus
on extending Plug and Play support to non-Plug and Play systemboard devices and dynamic event
notification.
4.1 System Device Configuration List
The system device configuration list consists of nodes or data structures that identify the embedded
devices that are on the system. The embedded devices consist of systemboard components that provide the
base functionality for the system. This includes devices such as the Programmable Interrupt Controller
(PIC), the DMA Controller, System Timer, Keyboard Controller, Integrated Video Controller, Floppy
Controller, etc. The system device configuration list only provides information about the systemboard
devices and does not include nodes for devices plugged into an expansion bus. The system device
configuration list does not identify the peripherals that are attached to the embedded systemboard devices.
For instance, the system configuration list will identify an integrated fixed disk controller but will not
provide nodes for any fixed disk drives that might be attached to the controller. It is assumed that
peripherals will be identified by other software. The system BIOS provides an interface for system
software to access the information in the system configuration list through the BIOS functions that are
defined later in this document. The System Device Node data structure provides configuration
information about a single systemboard device. The information returned for each systemboard
component reported through the Plug and Play BIOS interface will follow the data structure format
specified for the System Device Node. The next subsection describes the System Device Node data
structure.
4.2 System Device Node Definition
The System Device Node is the structure that represents a single embedded systemboard device. The
elements that make up this structure provide information that describe the device and the system resources
that have been allocated to the device. This includes reporting the system resources that have typically
been reserved for standard PC compatible systemboard devices, such as I/O port addresses from 00h to
FFh. The information for alternative or possible resource configuration settings can be provided in the
System Device Node; however, it is not required. The various possible resource settings can also be
provided in a configuration file or an image of the configuration file, in ROM, supplied by the system
vendor. This configuration file would contain the necessary configuration information not contained in
the System Device Node, and can provide more information to the user about the specific devices. If the
configuration information is contained in both the System Device Node and in a configuration file, then
the system resources possibilities for the device that are specified in the configuration file should take
precedence over the information contained in the system device node. The following data structure
defines the required elements for the base System Device Node. Please refer to the Plug and Play ISA
Specification version 1.0A (Section 4.6) for the maximum resources that a device node can use.