(+CC Rae, for attributes/fields)
On Sun, 2 Jul 2023 at 15:23, Mauro Carvalho Chehab mchehab@kernel.org wrote:
Hi Jon, Shuah & others,
I'd like to discuss with you with regards to test documentation.
I had some preliminary discussions with people interested on improving tests during EOSS last week in Prague, as we're working to improve media test coverage as well. During such discussions, I talked with developers from several companies that have been collaboration and/or using Kernel CI. I also talked with Nikolai from Red Hat, who gave a presentation about Kernel CI, which points that one of the areas to be improved there is documentation.
So, it seems it is worth having some discussions about how to improve Kernel test documentation.
Awesome: it'd definitely be nice to have some better documentation for specific tests. While the documentation for test systems as a whole seems okay (though could always do with improvement), I agree that documentation for individual test suites seems to mostly be either nonexistent, or exists only as unstructured text somewhere in the subsystem docs (or worse, a random wiki).
I've left a few first impressions / notes below:
While kernel_doc does a pretty decent job documenting functions and data structures, for tests, the most important things to be documented are:
a. what the tests do; b. what functionalities they are testing.This is a lot more important than documenting functions - and the used data structures on tests are typically the ones that are part of the driver's kAPI or uAPI, so they should be documented somewhere else.
Usually, (b) is not so simple, as, at least for complex hardware, the tested features are grouped on an hierarchical way, like:
1. hardware 1.1 DMA engine 1.2 output ports ... 2. firmware 2.1 firmware load 2.2 firmware DMA actions ... 3. kernel features 3.1 memory allocation 3.2 mmap 3.3 bind/unbind ...CI engines running the test sets usually want to produce a report that will be providing pass rates for the tested features and functionalites that are available at the driver's and their respective hardware and firmware.
I've doing some work at the tool we use to test DRM code [1] in order to have a decent documentation of the tests we have hosted there, focusing mostly on tests for i915 and Xe Intel drivers, also covering documentation for DRM core tests - while providing support for other vendors to also improve their test documentation for IGT - IGT GPU tools and tests.
The documentation tool I developed is generic enough to be used for other test sets and I believe it could be useful as well to document Kselftest and KUnit.
The core of the tool (at test_list.py) is a Python class, with some callers (igt_doc.py, xls_to_doc.py, doc_to_xls.py), being extensible enough to also have other callers to integrate with external tools. We are developing internally one to integrate with our internal Grafana reports to report the pass rate per documented feature, in an hierarchical way.
A lot of tests/test frameworks already have some sort of hierarchy: I suspect there'll be some cases where it makes sense to either duplicate that, or deviate from it, but it'd be nice to reuse it where it makes sense.
I imagine this gets more interesting as we have tests which span different frameworks, or if we have tests which need to show up multiple times.
Something similar to:
1. hardware pass rate: 98% (98 tests passed of 100) 1.1 DMA engine pass rate: 80% (8 tests passed of 10) 1.2 output ports pass rate: 100% (10 tests passed of 10) ...It is based on the concept that test documentation should be placed as close as possible to the actual code implementing the test sets. It was also be developed in a way that the documentation grouping is flexible. The code was written from the scratch in Python and was implemented inside a class that can also be re-used to do do other nice things, like importing/exporting test documentation to spreadsheets and integration with other tools (like Grafana).
The actual documentation tags look like this:
/** * TEST: Check if new IGT test documentation logic functionality is working * Category: Software build block * Sub-category: documentation * Functionality: test documentation * Issue: none * Description: Complete description of this test * * SUBTEST: foo * Description: do foo things * description continuing on another line * * SUBTEST: bar * Description: do bar things * description continuing on another line * Functionality: bar test doc */
How would these test/subtest names fit with, e.g., KUnit test/suite names? Would we want to require them to be the same, in which case can we parse them from the actual test declarations? Or would tests end up with multiple names?
And it has support for wildcards.
There, "TEST" is associated to the contents of the file, while "SUBTEST" refers to each specific subtest inside it. The valid fields are imported from JSON config files, and can be placed into an hierarchical way, in order to produce an hierarchical documentation. Fields defined at the "TEST" level are imported on "SUBTEST", but can be overriden.
If we assume that for KUnit, TEST == suite and SUBTEST == test, we hit the small issue that there can be multiple test suites per file. Ideally, we'd support a more arbitrary hierarchy here.
The JSON config file looks like this: https://gitlab.freedesktop.org/drm/igt-gpu-tools/-/blob/158feaa20fa2b9424ee5...
We're looking into having support for some level of test metadata in both KTAPv2[1] and KUnit[2], which might be an interesting point of comparison. (Things like inheritence work similarly.)
The advantages of having some of these fields being stored as a part of the test itself include having more self-descriptive results (being more readable without the source code / docs open) and the ability to filter test runs based on these fields.
I'd be really interested in working out what sorts of fields/attributes would be useful, too. I'm sure there'd be a lot of "general" ones, which it'd be nice to keep consistent across different subsystems. Though per-subsystem attributes are also really interesting: it'd be great if we could easily have tooling filter tests by "needs this GPU" or similar.
The output is in ReST, which can be generated in hierarchical or per-file way. The hierarchical output looks like this:
$ ./scripts/igt_doc.py --config tests/xe/xe_test_config.json --file fubar_tests.c =============================== Implemented Tests for Xe Driver =============================== Category: Software build block ============================== Sub-category: documentation --------------------------- Functionality: bar test doc ^^^^^^^^^^^^^^^^^^^^^^^^^^^ ``igt@fubar_tests@bar`` :Description: do bar things description continuing on another line :Issue: none Functionality: test documentation ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ``igt@fubar_tests@foo`` :Description: do foo things description continuing on another line :Issue: none(if --file is not used, it will use all C files specified at the configuration)
The tool already skips tags like the ones used by kernel-doc[1], so one could have both function documentation and per-test documentation on the same file, if needed.
While such tool was conceived to be part of IGT, it doesn't have anything specific for it [2], and I do believe it would be a great contribution to the Kernel to have such tool upstreamed, and integrated as a Sphinx extension.
If we decide to go ahead adding it, I can work on a patchset to apply it to the Kernel, modifying the scripts to better fit at the Kernel needs and start with some documentation examples for i915, DRM core and upcoming Xe KUnit tests.
Comments?
I like the idea overall, but do feel it'd be nice to integrate enough with the various test systems to avoid any rough edges where things like test layout crash, or we end up with too much duplication of features. That being said, I'd rather have a bit of redundancy and a few mismatches if it keeps this simple and more easily used with arbitrary test systems.
Regards, Mauro
[1] It should be trivial to patch kernel-doc for it to skip TEST and SUBTEST tags if we decide to integrate it to the kernel.
[2] except that tests there are named after IGT, as <igt <test>@<subtest>@<dynamic_subtest>, but a change to a Kernel-specific namespace would be trivial
[1]: https://lore.kernel.org/all/20230420205734.1288498-1-rmoar@google.com/ [2]: https://lore.kernel.org/linux-kselftest/20230610005149.1145665-1-rmoar@googl...