Configuration

The ACPI namespace contains a tree of devices attached to the system. ACPI-aware operating systems walk this tree to enumerate devices and gain access to the device's data and control methods. In the ACPI namespace, an ACPI device description consists of a device object node and its children. Common children of device nodes include:

_ADR:

a bus-specific address. For example, this could be a PCI device and function number.

_HID:

the EISA ID of an on-board device. This is used to identify the device.

_UID:

the unit number of an on-board device. This is used to distinguish between same kind of device.

_CRS:

the current resource settings. This method produces a byte stream that is similar to a PnP resource encoding.

_PRS:

the possible resource settings. This method also produces a byte stream similar to a PnP resource encoding.

_SRS:

set resource settings. This method takes a PnP-encoded byte stream and uses it to set the device's configuration.

Note that the operating system accesses device data and methods through the ACPI-CA software layer (described in Section 2.2).