90 lines
2.8 KiB
Plaintext
90 lines
2.8 KiB
Plaintext
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Copyright (C) 2018 Intel Corporation
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Author: Sakari Ailus <sakari.ailus@linux.intel.com>
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Referencing hierarchical data nodes
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-----------------------------------
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ACPI in general allows referring to device objects in the tree only.
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Hierarchical data extension nodes may not be referred to directly, hence this
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document defines a scheme to implement such references.
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A reference consist of the device object name followed by one or more
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hierarchical data extension [1] keys. Specifically, the hierarchical data
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extension node which is referred to by the key shall lie directly under the
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parent object i.e. either the device object or another hierarchical data
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extension node.
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The keys in the hierarchical data nodes shall consist of the name of the node,
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"@" character and the number of the node in hexadecimal notation (without pre-
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or postfixes). The same ACPI object shall include the _DSD property extension
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with a property "reg" that shall have the same numerical value as the number of
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the node.
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In case a hierarchical data extensions node has no numerical value, then the
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"reg" property shall be omitted from the ACPI object's _DSD properties and the
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"@" character and the number shall be omitted from the hierarchical data
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extension key.
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Example
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-------
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In the ASL snippet below, the "reference" _DSD property [2] contains a
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device object reference to DEV0 and under that device object, a
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hierarchical data extension key "node@1" referring to the NOD1 object
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and lastly, a hierarchical data extension key "anothernode" referring to
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the ANOD object which is also the final target node of the reference.
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Device (DEV0)
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{
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Name (_DSD, Package () {
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ToUUID("dbb8e3e6-5886-4ba6-8795-1319f52a966b"),
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Package () {
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Package () { "node@0", NOD0 },
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Package () { "node@1", NOD1 },
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}
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})
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Name (NOD0, Package() {
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ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
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Package () {
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Package () { "random-property", 3 },
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}
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})
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Name (NOD1, Package() {
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ToUUID("dbb8e3e6-5886-4ba6-8795-1319f52a966b"),
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Package () {
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Package () { "anothernode", ANOD },
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}
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})
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Name (ANOD, Package() {
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ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
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Package () {
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Package () { "random-property", 0 },
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}
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})
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}
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Device (DEV1)
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{
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Name (_DSD, Package () {
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ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
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Package () {
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Package () { "reference", ^DEV0, "node@1", "anothernode" },
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}
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})
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}
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Please also see a graph example in graph.txt .
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References
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----------
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[1] Hierarchical Data Extension UUID For _DSD.
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<URL:http://www.uefi.org/sites/default/files/resources/_DSD-hierarchical-data-extension-UUID-v1.1.pdf>,
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referenced 2018-07-17.
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[2] Device Properties UUID For _DSD.
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<URL:http://www.uefi.org/sites/default/files/resources/_DSD-device-properties-UUID.pdf>,
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referenced 2016-10-04.
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