linux-kernel - Re: [RFC PATCH 1/1] drm/format-helper: Add KUnit tests for drm_fb_xrgb8888_to

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Date:   Tue, 31 May 2022 20:44:54 +0200
From:   José Expósito <jose.exposito89@...il.com>
To:     Daniel Latypov <dlatypov@...gle.com>
Cc:     Maxime Ripard <maxime@...no.tech>, kunit-dev@...glegroups.com,
        javierm@...hat.com, tzimmermann@...e.de,
        maarten.lankhorst@...ux.intel.com, airlied@...ux.ie,
        daniel@...ll.ch, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 1/1] drm/format-helper: Add KUnit tests for
 drm_fb_xrgb8888_to_rgb332()

Hi Daniel,

Thanks for looking into the patch and for your comments.

On Mon, May 30, 2022 at 03:57:56PM -0700, Daniel Latypov wrote:
> A few initial notes:
> a) normally, `select`ing other kconfigs is discouraged. It's not
> explicitly called out in
> https://www.kernel.org/doc/html/latest/dev-tools/kunit/style.html#test-kconfig-entries
> but this was the conclusion after  some debate on the mailing lists
> earlier.
>
> b) I see `dst` is allocated with kzalloc but not freed. Should we use
> `kunit_kzalloc()` instead so it does get automatically freed?

Ooops yes, it was in my "I'll handle that once it works" list, but I
forgot to fix it, thanks for pointing it out
 
> > > > ---
> > > >  drivers/gpu/drm/Kconfig                  |  12 ++
> > > >  drivers/gpu/drm/Makefile                 |   3 +
> > > >  drivers/gpu/drm/drm_format_helper_test.c | 166 +++++++++++++++++++++++
> > > >  3 files changed, 181 insertions(+)
> > > >  create mode 100644 drivers/gpu/drm/drm_format_helper_test.c
> > > >
> > > > diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
> > > > index e88c497fa010..d92be6faef15 100644
> > > > --- a/drivers/gpu/drm/Kconfig
> > > > +++ b/drivers/gpu/drm/Kconfig
> > > > @@ -76,6 +76,18 @@ config DRM_KMS_HELPER
> > > >     help
> > > >       CRTC helpers for KMS drivers.
> > > >
> > > > +config DRM_FORMAR_HELPER_TEST
> > > > +   bool "drm_format_helper tests" if !KUNIT_ALL_TESTS
> > > > +   depends on DRM && KUNIT=y
> > > > +   select DRM_KMS_HELPER
> 
> From above, a)
> Specifically here, it'd be encouraged to instead do
>   depends on DRM && KUNIT=y && DRM_KMS_HELPER

My first attempt was to go with:

	depends on KUNIT=y && DRM && DRM_KMS_HELPER

However, when I try to run the tests I get this error:

	$ ./tools/testing/kunit/kunit.py run --kunitconfig=drivers/gpu/drm --arch=x86_64
	Regenerating .config ...
	Populating config with:
	$ make ARCH=x86_64 olddefconfig O=.kunit
	ERROR:root:Not all Kconfig options selected in kunitconfig were in the generated .config.
	This is probably due to unsatisfied dependencies.
	Missing: CONFIG_DRM_KMS_HELPER=y, CONFIG_DRM_FORMAR_HELPER_TEST=y

I wasn't able to figure out why that was happening, so I decided to use
"select", which seems to solve the problem.

Do you know why this could be happening?

> Ideally, using a .kunitconfig file would make it so having to select
> DRM_KMS_HELPER manually isn't that annoying.
> 
> > > AFAIK, kunit test cases are supposed to have a .kunitconfig too to
> > > enable the kunit tests easily.
> > >
> > > Maxime
> >
> > A .kuniconfig example is present in the cover letter. My understanding
> > from the docs:
> >
> > https://docs.kernel.org/dev-tools/kunit/run_wrapper.html#create-a-kunitconfig-file
> 
> The bit of the documentation you're looking for is
> https://www.kernel.org/doc/html/latest/dev-tools/kunit/running_tips.html#defining-a-set-of-tests
> You can create a drivers/gpu/drm/.kunitconfig file and run with
> $ ./tools/testing/kunit/kunit.py run --kunitconfig=drivers/gpu/drm --arch=x86_86
> 
> The contents of that file would be just like
>   CONFIG_KUNIT=y
>   CONFIG_DRM=y
>   CONFIG_DRM_KMS_HELPER=y  # if no `select`
>   CONFIG_DRM_FORMAR_HELPER_TEST=y

Noted, thanks a lot, I'll include it in the final version of the patch.

By the way, I also included it in an unrelated patch, just in case you
are wondering why I emailed you a random patch:
https://lore.kernel.org/linux-input/20220531181246.190729-1-jose.exposito89@gmail.com/T/

Thanks a lot for your help,
José Expósito

> Re "kunit test cases are supposed to have a .kunitconfig too"
> As I noted in the docs:
>   This is a relatively new feature (5.12+) so we don’t have any
> conventions yet about on what files should be checked in versus just
> kept around locally. It’s up to you and your maintainer to decide if a
> config is useful enough to submit (and therefore have to maintain).
> 
> So it's up to whatever people think works best/is worth it.
> I think in this case, it makes sense to add the file.
> 
> > Is that, like the .config file, the .kunitconfig file is not meant to
> > be included in git, but I'm sure someone else will clarify this point.
> 
> That bit of the docs needs to be rewritten.
> You're recommended to check in a drivers/gpu/drm/.kunitconfig file into git.
> 
> Context: `kunit.py` used to use the "<root>/.kunitconfig" file.
> Anytime you wanted to run more tests, you'd append to that file.
> So we agreed that no one should check in that file specifically.
> 
> Now kunit.py
> * uses "<build-dir>/.kunitconfig", by default: ".kunit/.kunitconfig"
> * has the --kunitconfig flag so you can use different files
> so it's no longer as relevant.
> 
> Hope that helps,
> Daniel