Advanced Configuration and Power Interface Specification

Advanced Configuration and Power Interface Specification
resource template buffer. The predefined descriptor field names may be appended to this name to
access individual fields within the descriptor via the Buffer Field operators.
Description
The ExtendedSpace macro evaluates to a buffer which contains a 64-bit Address Space resource
descriptor, which describes a range of addresses. The format of the 64-bit AddressSpace descriptor
can be found in “Extended Address Space Descriptor” (page 361). The macro is designed to be used
inside of a ResourceTemplate (page 882).
19.6.44 External (Declare External Objects)
Syntax
External (ObjectName, ObjectType, ReturnType, ParameterTypes)
Arguments
ObjectName is a NameString.
ObjectType is an optional ObjectTypeKeyword (e.g. IntObj, PkgObj, etc.). If not specified,
“UnknownObj” type is assumed.
ReturnType is optional. If the specified ObjectType is MethodObj, then this specifies the type or
types of object returned by the method. If the method does not return an object, then nothing is
specified or UnknownObj is specified. To specify a single return type, simply use the
ObjectTypeKeyword. To specify multiple possible return types, enclose the comma-separated
ObjectTypeKeywords with braces. For example: {IntObj, BuffObj}.
ParameterTypes is optional. If the specified ObjectType is MethodObj, this specifies both the
number and type of the method parameters. It is a comma-separated, variable-length list of the
expected object type or types for each of the method parameters, enclosed in braces. For each
parameter, the parameter type consists of either an ObjectTypeKeyword or a comma-separated sublist
of ObjectTypeKeywords enclosed in braces. There can be no more than seven parameters in
total.Description
The External directive informs the ASL compiler that the object is declared external to this table so
that no errors will be generated for an undeclared object. The ASL compiler will create the external
object at the specified place in the namespace (if a full path of the object is specified), or the object
will be created at the current scope of the External term.
For external control methods, the ASL compiler can emit an External AML opcode that contains the
name of the method and the number of required arguments. This information may be used by AML
disassemblers to properly disassemble the AML to the correct ASL code.
External is especially useful for use in secondary SSDTs, when the required scopes and objects are
declared in the main DSDT.
Example
This example shows the use of External in conjunction with Scope within an SSDT:
836 April, 2015 Version 6.0