Advanced Configuration and Power Interface Specification

ACPI Source Language (ASL)Reference
19.6.29 DerefOf (Dereference an Object Reference)
Syntax
DerefOf (Source) => Object
Arguments
Returns the object referred by the Source object reference.
Description
If the Source evaluates to an object reference, the actual contents of the object referred to are
returned. If the Source evaluates to a string, the string is evaluated as an ASL name (relative to the
current scope) and the contents of that object are returned. If the object specified by Source does not
exist then a fatal error is generated. If the object specified is a reference generated by the Index()
operator and refers to an uninitialized package element, then a fatal error is generated.
Note: (Compatibility Note) The use of a String with DerefOf was first introduced in ACPI 2.0.
19.6.30 Device (Declare Device Package)
Syntax
Device (DeviceName) {ObjectList}
Arguments
Creates a Device object of name DeviceName, which represents a processor, a bus or a device, or
any other similar hardware. Device opens a name scope.
Description
A Device Package is one of the basic ways the Differentiated Definition Block describes the
hardware devices in the system to the operating software. Each Device Package is defined
somewhere in the hierarchical namespace corresponding to that device’s location in the system.
Within the namespace of the device are other names that provide information and control of the
device, along with any sub-devices that in turn describe sub-devices, and so on.
For any device, the BIOS provides only information that is added to the device in a non-hardware
standard manner. This type of value-added function is expressible in the ACPI Definition Block
such that operating software can use the function.
The BIOS supplies Device Objects only for devices that are obtaining some system-added function
outside the device’s normal capabilities and for any Device Object required to fill in the tree for such
a device. For example, if the system includes a PCI device (integrated or otherwise) with no
additional functions such as power management, the BIOS would not report such a device; however,
if the system included an integrated ISA device below the integrated PCI device (device is an ISA
bridge), then the system would include a Device Package for the ISA device with the minimum
feature being added being the ISA device’s ID and configuration information and the parent PCI
device, because it is required to get the ISA Device Package placement in the namespace correct.
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