Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
MIME-Version: 1.0
References: <20220927221206.55930-1-mcanal@igalia.com> <20220927221206.55930-2-mcanal@igalia.com>
 <20220929223333.vh6wy45mfx6kccds@nostramo>
In-Reply-To: <20220929223333.vh6wy45mfx6kccds@nostramo>
From:   David Gow <davidgow@google.com>
Date:   Fri, 30 Sep 2022 14:50:43 +0800
Message-ID: <CABVgOSkx7KYNRKCN5h=37zQGR0qu+BDCb6cQeqbCwX8UxC3knw@mail.gmail.com>
Subject: Re: [PATCH v2 2/2] drm/tests: Split drm_test_dp_mst_sideband_msg_req_decode
 into parameterized tests
To:     =?UTF-8?Q?Micha=C5=82_Winiarski?= <michal.winiarski@intel.com>
Cc:     =?UTF-8?B?TWHDrXJhIENhbmFs?= <mcanal@igalia.com>,
        David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>, Melissa Wen <mwen@igalia.com>,
        =?UTF-8?Q?Andr=C3=A9_Almeida?= <andrealmeid@igalia.com>,
        Javier Martinez Canillas <javierm@redhat.com>,
        Daniel Latypov <dlatypov@google.com>,
        Arthur Grillo <arthur.grillo@usp.br>,
        Isabella Basso <isabbasso@riseup.net>, magalilemes00@gmail.com,
        Tales Aparecida <tales.aparecida@gmail.com>,
        dri-devel@lists.freedesktop.org,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Content-Type: multipart/signed; protocol="application/pkcs7-signature"; micalg=sha-256;
        boundary="00000000000057b24105e9df6aba"
Precedence: bulk

--00000000000057b24105e9df6aba
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable

On Fri, Sep 30, 2022 at 6:33 AM Micha=C5=82 Winiarski
<michal.winiarski@intel.com> wrote:
>
> On Tue, Sep 27, 2022 at 07:12:06PM -0300, Ma=C3=ADra Canal wrote:
> > The drm_test_dp_mst_sideband_msg_req_decode repeats the same test
> > structure with different parameters. This could be better represented
> > by parameterized tests, provided by KUnit.
> >
> > In order to convert the tests to parameterized tests, the test case for
> > the client ID was changed: instead of using get_random_bytes to generat=
e
> > the client ID, the client ID is now hardcoded in the test case.
>
> Generally "random" usage is not incompatible with parameterized tests, we=
 can
> create parameterized tests that use random data.
> The idea is to pass a function that generates the actual param (where we =
have a
> pointer to function as one of the members in "params" struct).
>
> For example, see "random_dp_query_enc_client_id" usage here:
> https://lore.kernel.org/dri-devel/20220117232259.180459-7-michal.winiarsk=
i@intel.com/
>
> In this case, we just compare data going in with data going out (and the =
data
> itself is not transformed in any way), so it doesn't really matter for co=
verage
> and we can hardcode.
>
> -Micha=C5=82

FWIW, while the uses of randomness in DRM tests so far haven't
concerned me much, I think we'll eventually want to have some way of
ensuring the inputs to tests are deterministic.

My thoughts are that (at some point) we'll add a kunit_random()
function or similar, which will use a pseudorandom number generator
which can be set to a deterministic seed before each test case. That
way, there'd be a way to reproduce an error easily if it occurred. (Of
course, there'd be a way of setting different or random seeds to
preserve the extra coverage you'd otherwise get.)

I don't think this is something worth holding up or changing existing
tests at the moment, but having tests behave deterministically is
definitely desirable, so +1 to avoiding get_random_bytes() if it's not
giving you any real benefit.

We've also had a few requests in the past for being able to pass in a
custom set of parameters from userspace, which opens up some other
interesting possibilities, though it's not a priority at the moment.

Cheers,
-- David

--00000000000057b24105e9df6aba
Content-Type: application/pkcs7-signature; name="smime.p7s"
Content-Transfer-Encoding: base64
Content-Disposition: attachment; filename="smime.p7s"
Content-Description: S/MIME Cryptographic Signature
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--00000000000057b24105e9df6aba--