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authorChangbin Du2019-04-25 01:52:49 +0800
committerRafael J. Wysocki2019-04-25 23:07:19 +0200
commit538f6f76b9ca5cbcd521db80e137d1c43e55556b (patch)
treeaafb3c8d62d5bd428027ab076e317c6c649ec952 /Documentation/acpi
parent97a63dd43477a93fa0fc53ff082af8d64ff618e1 (diff)
Documentation: ACPI: move DSD-properties-rules.txt to firmware-guide/acpi and covert to reST
This converts the plain text documentation to reStructuredText format and adds it to Sphinx TOC tree. No essential content change. Signed-off-by: Changbin Du <changbin.du@gmail.com> Reviewed-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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diff --git a/Documentation/acpi/DSD-properties-rules.txt b/Documentation/acpi/DSD-properties-rules.txt
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-_DSD Device Properties Usage Rules
-----------------------------------
-
-Properties, Property Sets and Property Subsets
-----------------------------------------------
-
-The _DSD (Device Specific Data) configuration object, introduced in ACPI 5.1,
-allows any type of device configuration data to be provided via the ACPI
-namespace. In principle, the format of the data may be arbitrary, but it has to
-be identified by a UUID which must be recognized by the driver processing the
-_DSD output. However, there are generic UUIDs defined for _DSD recognized by
-the ACPI subsystem in the Linux kernel which automatically processes the data
-packages associated with them and makes those data available to device drivers
-as "device properties".
-
-A device property is a data item consisting of a string key and a value (of a
-specific type) associated with it.
-
-In the ACPI _DSD context it is an element of the sub-package following the
-generic Device Properties UUID in the _DSD return package as specified in the
-Device Properties UUID definition document [1].
-
-It also may be regarded as the definition of a key and the associated data type
-that can be returned by _DSD in the Device Properties UUID sub-package for a
-given device.
-
-A property set is a collection of properties applicable to a hardware entity
-like a device. In the ACPI _DSD context it is the set of all properties that
-can be returned in the Device Properties UUID sub-package for the device in
-question.
-
-Property subsets are nested collections of properties. Each of them is
-associated with an additional key (name) allowing the subset to be referred
-to as a whole (and to be treated as a separate entity). The canonical
-representation of property subsets is via the mechanism specified in the
-Hierarchical Properties Extension UUID definition document [2].
-
-Property sets may be hierarchical. That is, a property set may contain
-multiple property subsets that each may contain property subsets of its
-own and so on.
-
-General Validity Rule for Property Sets
----------------------------------------
-
-Valid property sets must follow the guidance given by the Device Properties UUID
-definition document [1].
-
-_DSD properties are intended to be used in addition to, and not instead of, the
-existing mechanisms defined by the ACPI specification. Therefore, as a rule,
-they should only be used if the ACPI specification does not make direct
-provisions for handling the underlying use case. It generally is invalid to
-return property sets which do not follow that rule from _DSD in data packages
-associated with the Device Properties UUID.
-
-Additional Considerations
--------------------------
-
-There are cases in which, even if the general rule given above is followed in
-principle, the property set may still not be regarded as a valid one.
-
-For example, that applies to device properties which may cause kernel code
-(either a device driver or a library/subsystem) to access hardware in a way
-possibly leading to a conflict with AML methods in the ACPI namespace. In
-particular, that may happen if the kernel code uses device properties to
-manipulate hardware normally controlled by ACPI methods related to power
-management, like _PSx and _DSW (for device objects) or _ON and _OFF (for power
-resource objects), or by ACPI device disabling/enabling methods, like _DIS and
-_SRS.
-
-In all cases in which kernel code may do something that will confuse AML as a
-result of using device properties, the device properties in question are not
-suitable for the ACPI environment and consequently they cannot belong to a valid
-property set.
-
-Property Sets and Device Tree Bindings
---------------------------------------
-
-It often is useful to make _DSD return property sets that follow Device Tree
-bindings.
-
-In those cases, however, the above validity considerations must be taken into
-account in the first place and returning invalid property sets from _DSD must be
-avoided. For this reason, it may not be possible to make _DSD return a property
-set following the given DT binding literally and completely. Still, for the
-sake of code re-use, it may make sense to provide as much of the configuration
-data as possible in the form of device properties and complement that with an
-ACPI-specific mechanism suitable for the use case at hand.
-
-In any case, property sets following DT bindings literally should not be
-expected to automatically work in the ACPI environment regardless of their
-contents.
-
-References
-----------
-
-[1] http://www.uefi.org/sites/default/files/resources/_DSD-device-properties-UUID.pdf
-[2] http://www.uefi.org/sites/default/files/resources/_DSD-hierarchical-data-extension-UUID-v1.1.pdf