On 3/13/23 11:02, Frank Rowand wrote: > On 3/11/23 00:42, David Gow wrote: >> On Sat, 11 Mar 2023 at 07:34, Stephen Boyd <sboyd@xxxxxxxxxx> wrote: >>> >>> Quoting David Gow (2023-03-10 00:09:48) >>>> On Fri, 10 Mar 2023 at 07:19, Stephen Boyd <sboyd@xxxxxxxxxx> wrote: >>>>> >>>>> >>>>> Hmm. I think you're suggesting that the unit test data be loaded >>>>> whenever CONFIG_OF=y and CONFIG_KUNIT=y. Then tests can check for >>>>> CONFIG_OF and skip if it isn't enabled? >>>>> >>>> >>>> More of the opposite: that we should have some way of supporting tests >>>> which might want to use a DTB other than the built-in one. Mostly for >>>> non-UML situations where an actual devicetree is needed to even boot >>>> far enough to get test output (so we wouldn't be able to override it >>>> with a compiled-in test one). >>> >>> Ok, got it. >>> >>>> >>>> I think moving to overlays probably will render this idea obsolete: >>>> but the thought was to give test code a way to check for the required >>>> devicetree nodes at runtime, and skip the test if they weren't found. >>>> That way, the failure mode for trying to boot this on something which >>>> required another device tree for, e.g., serial, would be "these tests >>>> are skipped because the wrong device tree is loaded", not "I get no >>>> output because serial isn't working". >>>> >>>> Again, though, it's only really needed for non-UML, and just loading >>>> overlays as needed should be much more sensible anyway. >>> >>> I still have one niggle here. Loading overlays requires >>> CONFIG_OF_OVERLAY, and the overlay loading API returns -ENOTSUPP when >>> CONFIG_OF_OVERLAY=n. For now I'm checking for the config being enabled >>> in each test, but I'm thinking it may be better to simply call >>> kunit_skip() from the overlay loading function if the config is >>> disabled. This way tests can simply call the overlay loading function >>> and we'll halt the test immediately if the config isn't enabled. >>> >> >> That sounds sensible, though there is a potential pitfall. If >> kunit_skip() is called directly from overlay code, might introduce a >> dependency on kunit.ko from the DT overlay, which we might not want. >> The solution there is either to have a kunit wrapper function (so the >> call is already in kunit.ko), or to have a hook to skip the current >> test (which probably makes sense to do anyway, but I think the wrapper >> is the better option). >> >> >>>> >>>>>> >>>>>> That being said, I do think that there's probably some sense in >>>>>> supporting the compiled-in DTB as well (it's definitely simpler than >>>>>> patching kunit.py to always pass the extra command-line option in, for >>>>>> example). >>>>>> But maybe it'd be nice to have the command-line option override the >>>>>> built-in one if present. >>>>> >>>>> Got it. I need to test loading another DTB on the commandline still, but >>>>> I think this won't be a problem. We'll load the unittest-data DTB even >>>>> with KUnit on UML, so assuming that works on UML right now it should be >>>>> unchanged by this series once I resend. >>>> >>>> Again, moving to overlays should render this mostly obsolete, no? Or >>>> am I misunderstanding how the overlay stuff will work? >>> >>> Right, overlays make it largely a moot issue. The way the OF unit tests >>> work today is by grafting a DTB onto the live tree. I'm reusing that >>> logic to graft a container node target for kunit tests to add their >>> overlays too. It will be clearer once I post v2. >>> >>>> >>>> One possible future advantage of being able to test with custom DTs at >>>> boot time would be for fuzzing (provide random DT properties, see what >>>> happens in the test). We've got some vague plans to support a way of >>>> passing custom data to tests to support this kind of case (though, if >>>> we're using overlays, maybe the test could just patch those if we >>>> wanted to do that). >>> >>> Ah ok. I can see someone making a fuzzer that modifies devicetree >>> properties randomly, e.g. using different strings for clock-names. >>> >>> This reminds me of another issue I ran into. I wanted to test adding the >>> same platform device to the platform bus twice to confirm that the >>> second device can't be added. That prints a warning, which makes >>> kunit.py think that the test has failed because it printed a warning. Is >>> there some way to avoid that? I want something like >>> >>> KUNIT_EXPECT_WARNING(test, <call some function>) >>> >>> so I can test error cases. > > DT unittests already have a similar concept. A test can report that a > kernel warning (or any other specific text) either (1) must occur for the > test to pass or (2) must _not_ occur for the test to pass. The check > for the kernel warning is done by the test output parsing program > scripts/dtc/of_unittest_expect. > > The reporting by a test of an expected error in drivers/of/unittest.c > is done by EXPECT_BEGIN() and EXPECT_END(). These have been in > unittest for a long time. > > The reporting by a test of a not expected to occur error is done > by EXPECT_NOT_BEGIN() and EXPECT_NOT_END(). These are added to > unittest in linux 6.3-rc1. > > I discussed this concept in one of the early TAP / KTAP discussion The link to the early KTAP discussion on this concept is: https://lore.kernel.org/all/d38bf9f9-8a39-87a6-8ce7-d37e4a641675@xxxxxxxxx/T/#u > threads and expect to start a discussion thread on this specific > topic in the KTAP Specification V2 context. I expect the discussion > to result in a different implementation than what DT unittests are > using (bike shedding likely to ensue) but whatever is agreed to > should be easy for DT to switch to. The link to the KTAP Specification Version 2 process and progress is: https://elinux.org/Test_Results_Format_Notes#KTAP_version_2 -Frank > >> >> Hmm... I'd've thought that shouldn't be a problem: kunit.py should >> ignore most messages during a test, unless it can't find a valid >> result line. What does the raw KTAP output look like? (You can get it >> from kunit.py by passing the --raw_output option). >> >> That being said, a KUNIT_EXPECT_LOG_MESSAGE() or similar is something >> we've wanted for a while. I think that the KASAN folks have been >> working on something similar using console tracepoints: >> https://lore.kernel.org/all/ebf96ea600050f00ed567e80505ae8f242633640.1666113393.git.andreyknvl@xxxxxxxxxx/ >> >> Cheers, >> -- David >
