Date:   Tue, 18 Feb 2020 22:28:32 +0000
From:   "Bird, Tim" <Tim.Bird@...y.com>
To:     Brendan Higgins <brendanhiggins@...gle.com>
CC:     Frank Rowand <frowand.list@...il.com>,
        Alan Maguire <alan.maguire@...cle.com>,
        Greg KH <gregkh@...uxfoundation.org>, shuah <shuah@...nel.org>,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@...r.kernel.org>,
        KUnit Development <kunit-dev@...glegroups.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        Jonathan Corbet <corbet@....net>,
        David Gow <davidgow@...gle.com>
Subject: RE: [PATCH v3 kunit-next 1/2] kunit: add debugfs
 /sys/kernel/debug/kunit/<suite>/results display



> -----Original Message-----
> From: Brendan Higgins
> 
> On Tue, Feb 18, 2020 at 12:49 PM Bird, Tim <Tim.Bird@...y.com> wrote:
> >
> > > -----Original Message-----
> > > From:  Brendan Higgins
> > >
> > > On Wed, Feb 12, 2020 at 7:25 PM Frank Rowand <frowand.list@...il.com> wrote:
> > > >
> > > > On 2/7/20 10:58 AM, Alan Maguire wrote:
> >
> > ...
> >
> > > > > diff --git a/lib/kunit/test.c b/lib/kunit/test.c
> > > > > index 9242f93..aec607f 100644
> > > > > --- a/lib/kunit/test.c
> > > > > +++ b/lib/kunit/test.c
> > > > > @@ -10,6 +10,7 @@
> > > > >  #include <linux/kernel.h>
> > > > >  #include <linux/sched/debug.h>
> > > > >
> > > > > +#include "debugfs.h"
> > > > >  #include "string-stream.h"
> > > > >  #include "try-catch-impl.h"
> > > > >
> > > > > @@ -28,73 +29,91 @@ static void kunit_print_tap_version(void)
> > > > >       }
> > > > >  }
> > > > >
> > > > > -static size_t kunit_test_cases_len(struct kunit_case *test_cases)
> > > > > +size_t kunit_suite_num_test_cases(struct kunit_suite *suite)
> > > > >  {
> > > > >       struct kunit_case *test_case;
> > > > >       size_t len = 0;
> > > > >
> > > > > -     for (test_case = test_cases; test_case->run_case; test_case++)
> > > > > +     kunit_suite_for_each_test_case(suite, test_case)
> > > > >               len++;
> > > > >
> > > > >       return len;
> > > > >  }
> > > > > +EXPORT_SYMBOL_GPL(kunit_suite_num_test_cases);
> > > > >
> > > > >  static void kunit_print_subtest_start(struct kunit_suite *suite)
> > > > >  {
> > > > >       kunit_print_tap_version();
> > > > > -     pr_info("\t# Subtest: %s\n", suite->name);
> > > > > -     pr_info("\t1..%zd\n", kunit_test_cases_len(suite->test_cases));
> > > > > +     kunit_log(KERN_INFO, suite, "# Subtest: %s", suite->name);
> > > > > +     kunit_log(KERN_INFO, suite, "1..%zd",
> > > > > +               kunit_suite_num_test_cases(suite));
> > > >
> > > > The subtest 'is a TAP stream indented 4 spaces'.  (So the old code was
> > > > also incorrect since it indented with a tab.)
> > >
> > > Whoops.
> > >
> > > I agree that fixing tabs to spaces is probably the easiest thing to do
> > > here; nevertheless, I think this might be a good time to talk about
> > > other deviations from the spec and what to do about it. This might
> > > also be a good time to bring up Tim's comment at LPC last year about
> > > forking TAP. Arguably I already have given that TAP14 is still under
> > > review and is consequently subject to change.
> > >
> > > Additionally, the way I report expectation/assertion failures are my
> > > own extension to the TAP spec. I did this because at the time I wasn't
> > > ready to open the can of worms that was adding a YAML serializer to
> > > the Linux kernel; I mentioned adding a YAML serializer at LPC and
> > > people didn't seem super thrilled with the idea.
> >
> > I'm not sure I follow.  Are you talking about writing YAML or interpreting
> > YAML.  You don't need a serializer to write YAML.  It can be done
> > with straight text output.  I guess it depends on the scope of what you
> > envision.  Even if you want to do more than trivial structured output,
> > I don't think you'll need a full serializer.  (IOW, I think you could sneak
> > something in and just call it a test output formatter.  Just don't call it YAML
> > and most people won't notice. :-)
> 
> Yeah, for the first one or two things just printing things out
> directly is probably fine, and yes, I could have just snuck it in, but
> at the time it wasn't a hindrance for me to ask what people wanted: I
> had already worked around it.
> 
> In any case, I was just explaining part of why I did expectations and
> assertion failures the way that I did.
> 
> > >
> > > Further both the TAP implementation here as well as what is in
> > > kselftest have arbitrary kernel output mixed in with TAP output, which
> > > seems to be a further deviation from the spec.
> > Well that's a different kettle of worms, and really argues for staying
> > with something that is strictly line-based.
> >
> > >
> > > In an effort to do this, and so that at the very least I could
> > > document what I have done here, I have been looking into getting a
> > > copy of TAP into the kernel. Unfortunately, TAP appears to have some
> > > licensing issues. TAP says that it can be used/modified "under the
> > > same terms as Perl itself" and then provides a dead link. I filed a
> > > pull request to update the licence to the Perl Artistic Licence 1.0
> > > since I believe that is what they are referencing; however, I have not
> > > heard back from them yet.
> >
> > When you say "getting a copy of TAP into the kernel", I presume you mean
> > an existing implementation to produce TAP output?  Or are you talking about
> > a TAP interpreter?  I'm not sure the former needs to use an existing implementation.
> 
> Sorry, that wasn't clear. I meant: get a copy of the TAP spec itself
> into the kernel documentation. KUnit already has an implementation.
Ah. OK.  Thanks.

> 
> > I previously volunteered (in Lisbon) to write up the TAP deviations,
> > and never got around to it.   Sorry about that. I can try to work on it now if
> > people are still interested.
> 
> I think that would be useful. I would do it, but, as I mentioned,
> there are licensing issues with the TAP spec. I am trying to resolve
> those issues, and am currently waiting to hear back from somebody from
> TAP.

If that drags on at all, I'd be happy to write up some docs from scratch.
Since we have deviations from TAP, and I was supposed to write up those
deviations anyway, it might be worthwhile to combine those two actions.
Also, a good chunk of the spec examples are spent on the YAML stuff,
which we currently don't support.

We can reference the official spec of course.  I think I suggested we probably
need to fork it and define our own KTAP anyway (with an eye towards staying
compatible with external parsers).

It *is* a bit weird that their licensing is unclear.  I get the feeling, though, that
the project is very much on people's backburner.  (Mine included, unfortunately.)
 -- Tim

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