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Diffstat (limited to 'Documentation/firmware-guide/acpi/dsd/data-node-references.rst')
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1 files changed, 21 insertions, 20 deletions
diff --git a/Documentation/firmware-guide/acpi/dsd/data-node-references.rst b/Documentation/firmware-guide/acpi/dsd/data-node-references.rst index 9b17dc77d18c..ccb4b153e6f2 100644 --- a/Documentation/firmware-guide/acpi/dsd/data-node-references.rst +++ b/Documentation/firmware-guide/acpi/dsd/data-node-references.rst @@ -5,18 +5,21 @@ Referencing hierarchical data nodes =================================== -:Copyright: |copy| 2018 Intel Corporation +:Copyright: |copy| 2018, 2021 Intel Corporation :Author: Sakari Ailus <sakari.ailus@linux.intel.com> ACPI in general allows referring to device objects in the tree only. Hierarchical data extension nodes may not be referred to directly, hence this document defines a scheme to implement such references. -A reference consist of the device object name followed by one or more -hierarchical data extension [1] keys. Specifically, the hierarchical data -extension node which is referred to by the key shall lie directly under the -parent object i.e. either the device object or another hierarchical data -extension node. +A reference to a _DSD hierarchical data node is a string consisting of a +device object reference followed by a dot (".") and a relative path to a data +node object. Do not use non-string references as this will produce a copy of +the hierarchical data node, not a reference! + +The hierarchical data extension node which is referred to shall be located +directly under its parent object i.e. either the device object or another +hierarchical data extension node [dsd-guide]. The keys in the hierarchical data nodes shall consist of the name of the node, "@" character and the number of the node in hexadecimal notation (without pre- @@ -33,11 +36,9 @@ extension key. Example ======= -In the ASL snippet below, the "reference" _DSD property [2] contains a -device object reference to DEV0 and under that device object, a -hierarchical data extension key "node@1" referring to the NOD1 object -and lastly, a hierarchical data extension key "anothernode" referring to -the ANOD object which is also the final target node of the reference. +In the ASL snippet below, the "reference" _DSD property contains a string +reference to a hierarchical data extension node ANOD under DEV0 under the parent +of DEV1. ANOD is also the final target node of the reference. :: Device (DEV0) @@ -52,12 +53,14 @@ the ANOD object which is also the final target node of the reference. Name (NOD0, Package() { ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"), Package () { + Package () { "reg", 0 }, Package () { "random-property", 3 }, } }) Name (NOD1, Package() { ToUUID("dbb8e3e6-5886-4ba6-8795-1319f52a966b"), Package () { + Package () { "reg", 1 }, Package () { "anothernode", "ANOD" }, } }) @@ -74,20 +77,18 @@ the ANOD object which is also the final target node of the reference. Name (_DSD, Package () { ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"), Package () { - Package () { "reference", ^DEV0, "node@1", "anothernode" }, + Package () { "reference", "^DEV0.ANOD" } + }, } }) } -Please also see a graph example in :doc:`graph`. +Please also see a graph example in +Documentation/firmware-guide/acpi/dsd/graph.rst. References ========== -[1] Hierarchical Data Extension UUID For _DSD. -<https://www.uefi.org/sites/default/files/resources/_DSD-hierarchical-data-extension-UUID-v1.1.pdf>, -referenced 2018-07-17. - -[2] Device Properties UUID For _DSD. -<https://www.uefi.org/sites/default/files/resources/_DSD-device-properties-UUID.pdf>, -referenced 2016-10-04. +[dsd-guide] DSD Guide. + https://github.com/UEFI/DSD-Guide/blob/main/dsd-guide.adoc, referenced + 2021-11-30. |