129 lines
4.4 KiB
Plaintext
129 lines
4.4 KiB
Plaintext
// Copyright (c) 2015-2017 Khronos Group. This work is licensed under a
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// Creative Commons Attribution 4.0 International License; see
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// http://creativecommons.org/licenses/by/4.0/
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[appendix]
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[[appendix-vuid]]
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= Valid Usage ID Tags
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Valid usage statements in the published Vulkan Specification must all be
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given _Valid Usage ID_ or _VUID_ tags.
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These tags are asciidoc anchors, intended for use by the validation layer to
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provide unique names for each validation condition, and a way to link from
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validation layer reports into the corresponding parts of the Specification.
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== Format of VUID Tags
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For implicit valid usage statements, the tags are formatted like this:
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[source,asciidoc]
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----
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[[VUID-blockname-paramname-category]]
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----
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_blockname_ is the name of the function or structure for which a valid usage
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statement is being generated.
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_paramname_ is the name of the parameter being validated.
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In some cases, the statement does not validate a single parameter and this
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portion of the tag is absent.
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_category_ is the type of statement being generated.
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There are over one dozen types referring to distinct conditions such as
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valid objects, required bitmasks, required array lengths, constraints on
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parent objects, and so on.
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For explicit valid usage statements, the tags are formatted like this:
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[source,asciidoc]
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----
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[[VUID-blockname-paramname-number]]
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----
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_blockname_ is the name of the function or structure for which a valid usage
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statement is being generated.
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_paramname_ is the name of the parameter being validated.
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In some cases, the statement does not validate a single parameter and this
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portion of the tag is replaced by `-None-`
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_number_ is a unique five digit, zero-filled number used to disambiguate
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similar tag names.
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== Creating VUID Tags
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For implicit valid usage statements generated automatically from `vk.xml`,
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VUID tags are created automatically by the generator scripts.
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For explicit valid usage statements, VUID tags are generated by passing
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appropriate options to the script `doc/specs/vulkan/reflow.py`.
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Since these tags are of use only to the published validation layer, they are
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needed only in the published Specification sources and outputs.
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Therefore, authors of extensions, or other branches adding valid usage
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statements, are not themselves responsible for adding tags in their
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branches.
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The specification editors will take care of this as part of the process of
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publishing updates.
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For reference purposes, this process is described below:
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First, after integrating all new specification language into the internal
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gitlab branch which contains the canonical Specification source, invoke the
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following command in `doc/specs/vulkan`:
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[source,sh]
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----
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python3 reflow.py -overwrite -noflow -tagvu chapters/*.txt chapters/*/*.txt
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----
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This will add VUID tags to all statements in valid usage blocks which don't
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already have them.
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Some diagnostics will be reported, but these are do not in general require
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any action.
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After updating all files, the script will print out a final line like:
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[source,sh]
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----
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WARN: You must now edit the value of reflow.py:startVUID to 1376 so that future runs will not overwrite existing VUID tags
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----
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Second, after verifying the updates are correct using e.g. `git diff`, edit
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`reflow.py` and edit the definition of the variable startVUID as directed:
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[source,python]
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----
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# The value to start tagging VU statements at, unless overridden by -nextvu
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startVUID = 1376
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----
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Commit the updated source files and `reflow.py` together.
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The next time the script is run, VUID tags will be assigned numbers starting
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from the current startVUID value.
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== Updating VUID Tags When Valid Usage Statements Change
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Valid usage statements have corresponding tests in the Vulkan Validation
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Layer.
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The tests must be changed in response to semantic changes in the VU
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statements, whether for bug-fixing, adding extension interactions, or
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otherwise.
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The rule used when updating explicit VU statements is that the merge request
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or pull request responsible for making the change must remove the existing
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VUID tag, so that a new one can be assigned, _except_ in the following
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cases:
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* The changes are non-semantic, such as using consistent phrasing or
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markup.
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* The changes consist of changing `KHX` to `KHR` suffixes when promoting a
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Khronos-defined extension.
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[NOTE]
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.Note
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====
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This section may need further modification in response to guidelines agreed
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to by the Vulkan Working Group.
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====
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