Advanced Configuration and Power Interface Specification

Device Configuration
6.2.5 _DSD (Device Specific Data)
This optional object is used to provide device drivers (via OSPM) with additional device properties
and information. _DSD returns a variable-length package containing a list of Device Data Descriptor
structures each consisting of a Universal Unique Identifier (UUID) and a package (Data Structure).
The UUID is all that is needed to define the Data Structure. The UUID itself may place a restriction
based on _HID or the optional _CID, _CLS, _HRV, _SUB objects, or _HID and one of those
optional objects. However, it also may not place such a restriction.
New UUIDs may be created by OEMs and IHVs or other interface or device governing bodies (e.g.
the PCI SIG or the UEFI Forum), as long as the UUID is different from other published UUIDs.
The list of well-known UUIDs allocated for _DSD and the definition of data formats associated with
them is available in the following auxiliary document hosted by the UEFI Forum: http://
www.uefi.org/acpi.
Arguments:
None
Return Value:
A variable-length Package containing a list of Device Data Descriptor structures as described
below.
Return Value Information
Package ()
{
Device Data Descriptor 0
...
Device Data Descriptor n
}
Each Device Data Descriptor structure consists of two elements, as follows:
UUID
Data Structure
// Buffer (16 bytes)
// Package (depending on UUID)
UUID is a Universal Unique Identifier (16 bytes) that uniquely determines the format of Data
Structure.
Data Structure is a set of device specific data items the format of which is uniquely determined by
the UUID and the meaning of which is uniquely determined by the UUID possibly in combination
with a PNP or ACPI device ID.
Multiple Device Data Descriptor structures with the same UUID are not permitted.
_DSD must return the same data each time it is evaluated. Firmware should not expect it to be
evaluated every time (in case it is implemented as a method).
Examples:
Note: The UUID used in the following examples is assumed to define the data format for Data Structure
as a list of packages of length 2 (Properties) whose first element (Key) must be a String and the
second element is a Value associated with that key. The set of valid Keys and the format and
Version 6.0 299