_DSD (Device Specific Data) Implementation Guide
October 2016
Revision 1.1
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1................... Introduction
1.2 Conventions used in this
document
2................... General Recommendations
2.2 General _DSD Definition Template
3................... Well Known _DSD UUIDs and Data Structure Formats 3.1 Device Properties UUID
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Description |
Revision Date |
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First revision |
July 16, 2014 |
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New Section 3.2 Hierarchical Properties Extension UUID |
August 8, 2015 |
§ Document Number: XXXXXX
This document gives recommendations on the use of the _DSD (Device Specific Data) ACPI device configuration object. It is intended for firmware and software engineers implementing _DSD or designing software that will use information supplied by it.
The _DSD, as defined by the ACPI Specification, returns a Package the first and every odd element of which is a Universal Unique Identifier (UUID) and every even element of which is a Package (Data Structure), where each of the UUIDs determines the format of the Data Structure immediately following it. The well-known UUIDs to use in the _DSD output and the Data Structure formats associated with them are also specified in this document.
1.
Introduction
This document gives recommendations on the use of the _DSD (Device Specific Data) ACPI device configuration object. It is intended for firmware and software engineers implementing _DSD or designing software that will use information supplied by it.
The _DSD, as defined by the ACPI Specification, returns a Package the first and every odd element of which is a Universal Unique Identifier (UUID) and every even element of which is a Package (Data Structure), where each of the UUIDs determines the format of the Data Structure immediately following it. The well-known UUIDs to use in the _DSD output and the Data Structure formats associated with them are also specified in this document.
1.
Terms
The following terms are used throughout this document to describe varying aspects of input localization:
ACPI
Device Device ID GUID
UUID
Advanced Configuration and Power Interface specification. Hardware component or set of interrelated hardware registers. Plug and Play ID or ACPI ID of a device.
Globally Unique Identifier. A 128-bit value used to uniquely name entities. A unique GUID can be generated by an individual without the help of a centralized authority. This allows the generation of names that will never conflict, even among multiple, unrelated parties.
Universal Unique Identifier, GUID.
2.
Conventions
used in this document
1.2.1 Typographic conventions
This document uses the typographic and illustrative conventions described below:
Plain text The normal text typeface is used for the vast majority of the descriptive text in a specification.
BOLD Monospace Computer code, example code
segments, and all prototype code segments use a BOLD Monospace typeface with
a dark red color. These code listings normally appear in one or more separate
paragraphs, though words or segments can also be embedded in a normal text
paragraph.
2.1
_DSD and _DSM
Although in principle _DSM (Device Specific Method) may be used to implement the functionality provided by _DSD, it is not recommended to do so. Since _DSD is better suited for providing device configuration data, it should be used for this purpose
2.
General
Recommendations
1.
_DSD
and _DSM
Although in principle _DSM (Device Specific Method) may be used to implement the functionality provided by _DSD, it is not recommended to do so. Since _DSD is better suited for providing device configuration data, it should be used for this purpose where applicable. However, there are situations in which using _DSM instead of it needs to be considered. Generally, all situations in which it would be necessary to implement _DSD as a method for technical reasons fall into this category, but in particular _DSD should not write into device registers in addition to returning the data. In addition to that, _DSD must return the same data every time it is evaluated, so if that cannot be guaranteed, _DSM has to be used instead of it.
2.
General
_DSD Definition Template
Wherever possible, it is recommended to implement _DSD as a Name, as opposed to a Method, so as to avoid programmatic errors and computational overhead associated with the execution of AML code. In that case the definition of _DSD should follow the common template below.
Name (_DSD, Package () { ToUUID("UUID1"),
Package () {
...
}, ToUUID("UUID2"),
Package
() {
...
},
... ToUUID("UUIDn"),
Package
() {
...
}
})
3.
Well
Known _DSD UUIDs and Data Structure Formats
1.
Device
Properties UUID
http://www.uefi.org/sites/default/files/resources/_DSD-device-properties-UUID.pdf
2.
Hierarchical
Properties Extension UUID
http://www.uefi.org/sites/default/files/resources/_DSD-hierarchical-data-extension-UUID-v1.1.pdf