diff options
| -rw-r--r-- | Documentation/acpi/dsd/data-node-references.txt | 69 |
1 files changed, 69 insertions, 0 deletions
diff --git a/Documentation/acpi/dsd/data-node-references.txt b/Documentation/acpi/dsd/data-node-references.txt new file mode 100644 index 000000000000..00c3b5fe1f2e --- /dev/null +++ b/Documentation/acpi/dsd/data-node-references.txt @@ -0,0 +1,69 @@ +Copyright (C) 2018 Intel Corporation +Author: Sakari Ailus <sakari.ailus@linux.intel.com> + + +Referencing hierarchical data nodes +----------------------------------- + +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. + +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" referring to the NODE object and + lastly, a hierarchical data extension key "anothernode" referring to the + ANOD object which is also the final target of the reference. + + Device (DEV0) + { + Name (_DSD, Package () { + ToUUID("dbb8e3e6-5886-4ba6-8795-1319f52a966b"), + Package () { + Package () { "node", NODE }, + } + }) + Name (NODE, Package() { + ToUUID("dbb8e3e6-5886-4ba6-8795-1319f52a966b"), + Package () { + Package () { "anothernode", ANOD }, + } + }) + Name (ANOD, Package() { + ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"), + Package () { + Package () { "random-property", 0 }, + } + }) + } + + Device (DEV1) + { + Name (_DSD, Package () { + ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"), + Package () { + Package () { "reference", ^DEV0, "node", "anothernode" }, + } + }) + } + + +References +---------- + +[1] Hierarchical Data Extension UUID For _DSD. + <URL:http://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. + <URL:http://www.uefi.org/sites/default/files/resources/_DSD-device-properties-UUID.pdf>, + referenced 2016-10-04. |
