Message-ID: <20220902133828.ufwp6bgzd37yu6bv@nostramo.hardline.pl>
Date:   Fri, 2 Sep 2022 15:38:28 +0200
From:   Michał Winiarski <michal.winiarski@...el.com>
To:     Jani Nikula <jani.nikula@...ux.intel.com>
CC:     Maxime Ripard <maxime@...no.tech>,
        Maíra Canal <mairacanal@...eup.net>,
        Isabella Basso <isabbasso@...eup.net>,
        <magalilemes00@...il.com>, <tales.aparecida@...il.com>,
        <mwen@...lia.com>, <andrealmeid@...eup.net>,
        <siqueirajordao@...eup.net>, Trevor Woerner <twoerner@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...ux.ie>,
        Javier Martinez Canillas <javierm@...hat.com>,
        David Gow <davidgow@...gle.com>, <brendanhiggins@...gle.com>,
        Arthur Grillo <arthur.grillo@....br>,
        José Expósito <jose.exposito89@...il.com>,
        <linux-kernel@...r.kernel.org>, <dri-devel@...ts.freedesktop.org>,
        <kunit-dev@...glegroups.com>
Subject: Re: [PATCH v2 2/2] drm/tests: Change "igt_" prefix to "test_drm_"

On Fri, Sep 02, 2022 at 04:03:20PM +0300, Jani Nikula wrote:
> On Fri, 02 Sep 2022, Maxime Ripard <maxime@...no.tech> wrote:
> > On Fri, Sep 02, 2022 at 11:04:14AM +0300, Jani Nikula wrote:
> >> On Thu, 01 Sep 2022, Maíra Canal <mairacanal@...eup.net> wrote:
> >> > Hi Maxime,
> >> >
> >> > On 9/1/22 09:55, Maxime Ripard wrote:
> >> >> Hi,
> >> >> 
> >> >> On Thu, Sep 01, 2022 at 09:42:10AM -0300, Maíra Canal wrote:
> >> >>> With the introduction of KUnit, IGT is no longer the only option to run
> >> >>> the DRM unit tests, as the tests can be run through kunit-tool or on
> >> >>> real hardware with CONFIG_KUNIT.
> >> >>>
> >> >>> Therefore, remove the "igt_" prefix from the tests and replace it with
> >> >>> the "test_drm_" prefix, making the tests' names independent from the tool
> >> >>> used.
> >> >>>
> >> >>> Signed-off-by: Maíra Canal <mairacanal@...eup.net>
> >> >>>
> >> >>> ---
> >> >>> v1 -> v2: https://lore.kernel.org/dri-devel/20220830211603.191734-1-mairacanal@riseup.net/
> >> >>> - Change "drm_" prefix to "test_drm_", as "drm_" can be a bit confusing (Jani Nikula).
> >> >> 
> >> >> I appreciate it's a bit of a bikeshed but I disagree with this. The
> >> >> majority of the kunit tests already out there start with the framework
> >> >> name, including *all* the examples in the kunit doc. Plus, it's fairly
> >> >> obvious that it's a test, kunit is only about running tests in the first
> >> >> place.
> >> >
> >> > Would it be better to keep it as "drm_"?
> >> 
> >> That's not "keeping". That's renaming igt to drm.
> >
> > Well, there's like half the tests that are prefixed with drm, the other
> > with igt, so it's both really
> >
> >> > Currently, I don't think it is appropriate to hold the "igt_" prefix, as
> >> > the tests are not IGT exclusive, but I don't have a strong opinion on
> >> > using the "drm_" or the "test_drm" prefixes.
> >> 
> >> I repeat my stance that "drm_" alone is confusing.
> >
> > What are you confusing it with?
> >
> >> For the reason alone that it pollutes the code tagging tools, mixing
> >> actual drm_ types and functions with unit test functions.
> >
> > I don't get it, I'm sorry. All these functions are static and not part
> > of any API, so I can't see how it would pollute a code tagging tool. Or
> > at least, not more than any driver does.
> >
> > And we're part of a larger project here, it's about consistency with the
> > rest of the ecosystem.
> 
> Okay, so I'm just going to explain what I mean, but say "whatever" right
> after and move on.
> 
> For example, drm_buddy_test.c includes drm_buddy.h so with the igt_ ->
> drm_ rename none of the test functions may clash with the drm_buddy_
> prefixed existing functions. Ditto for all tests similarly.
> 
> For example drm_buddy_alloc_range() as a name sounds like something that
> allocs a range, not something that tests range allocation. On the other
> hand, you have drm_buddy_alloc_blocks() which is actually a real
> drm_buddy function, not a test. What would you call a test that tests
> that? Here, we end up with names that are all prefixed drm_buddy and you
> won't know what's the actual function and what's the test unless you
> look it up.
> 
> I use code tagging that I can use for finding and completing
> e.g. functions. Currently I have the following completions, for
> igt_buddy_ and drm_buddy_, respectively:
> 
> Possible completions are:
> igt_buddy_alloc_limit 	igt_buddy_alloc_optimistic 	igt_buddy_alloc_pathological
> igt_buddy_alloc_pessimistic 	igt_buddy_alloc_range 	igt_buddy_alloc_smoke
> 
> Possible completions are:
> drm_buddy_alloc_blocks 	drm_buddy_block 	drm_buddy_block_is_allocated 	drm_buddy_block_is_free
> drm_buddy_block_is_split 	drm_buddy_block_offset 	drm_buddy_block_order 	drm_buddy_block_print
> drm_buddy_block_size 	drm_buddy_block_state 	drm_buddy_block_trim 	drm_buddy_fini
> drm_buddy_free_block 	drm_buddy_free_list 	drm_buddy_init 	drm_buddy_init_test
> drm_buddy_module_exit 	drm_buddy_module_init 	drm_buddy_print
> 
> With the patch at hand, they'll all be lumped under drm_buddy_
> completions, and some of them will be actual drm buddy functions and
> some not.
> 
> I just find it a very odd convention to name the tests in a way that's
> indistinguishable from the real things. Even *within* drm_buddy_test.c
> where you read the test code. Because currently you do have calls to
> igt_buddy_ prefixed functions from other igt_buddy_ prefixed functions,
> along with the drm_buddy_ prefixed calls. I think it's just going to be
> a mess.
> 
> /rant
> 
> Whatever. Moving on.

KUnit docs [1] state:
https://docs.kernel.org/dev-tools/kunit/style.html#test-cases
"As tests are themselves functions, their names cannot conflict with other
C identifiers in the kernel. This may require some creative naming."
And give examples of names. But this should be local to individual test suite -
as long as the test is readable, and the name describes what it is testing, we
should be fine. We don't even need to pass drm_* prefix, as this convention is
expected for test suites, not test cases [2].

Having said that - I do believe that igt_* prefix don't belong here (which is
why I'm progressively trying to get rid of in the patches that refactor some of
the tests).
I agree with Jani - can we take it on a case-by-case basis?
If the test name is too similar to the function that it is testing, we could go
with one of the following (taking igt_buddy_alloc_limit as example):
drm_buddy_test_alloc_limit
test_drm_buddy_alloc_limit
buddy_test_alloc_limit
test_buddy_alloc_limit

And either of those is fine in my opinion (I'd personally go with
test_buddy_alloc_limit in this case).
We don't really need a DRM-wide (or worse, kernel wide) convention for test case
names (it's only really needed for test suites).

[1] https://docs.kernel.org/dev-tools/kunit/style.html#test-cases
[2] https://docs.kernel.org/dev-tools/kunit/style.html#suites

-Michał

> 
> 
> BR,
> Jani.
> 
> 
> -- 
> Jani Nikula, Intel Open Source Graphics Center

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