Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.35 as permitted sender) client-ip=23.128.96.35;
From:   Javier Martinez Canillas <javierm@redhat.com>
To:     Geert Uytterhoeven <geert@linux-m68k.org>,
        Maxime Ripard <mripard@kernel.org>
Cc:     Thomas Zimmermann <tzimmermann@suse.de>,
        linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org
Subject: Re: [PATCH] drm/ssd130x: Drop _helper prefix from struct
 drm_*_helper_funcs callbacks
In-Reply-To: <CAMuHMdUGVgj6V+N865QZaAusqD7O2f1askE544Z4MF0h4zBERg@mail.gmail.com>
References: <20230914195138.1518065-1-javierm@redhat.com>
 <f5620d32-2705-498b-a65c-7dc663340a6d@suse.de>
 <87wmwo3q50.fsf@minerva.mail-host-address-is-not-set>
 <552hpgr7qzbjxuyei3n5m7rsn7ekwbdgzv25oe5vy6qb35gf23@q4etussk5jwl>
 <CAMuHMdUGVgj6V+N865QZaAusqD7O2f1askE544Z4MF0h4zBERg@mail.gmail.com>
Date:   Thu, 21 Sep 2023 10:23:42 +0200
Message-ID: <878r90kk8h.fsf@minerva.mail-host-address-is-not-set>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: quoted-printable
Precedence: bulk

Geert Uytterhoeven <geert@linux-m68k.org> writes:

Hello Geert and Maxime,

> Hi Maxime,
>
> On Thu, Sep 21, 2023 at 9:44=E2=80=AFAM Maxime Ripard <mripard@kernel.org=
> wrote:
>> On Mon, Sep 18, 2023 at 09:19:07AM +0200, Javier Martinez Canillas wrote:
>> > Thomas Zimmermann <tzimmermann@suse.de> writes:
>> > > Am 14.09.23 um 21:51 schrieb Javier Martinez Canillas:
>> > >> The driver uses a naming convention where functions for struct drm_=
*_funcs
>> > >> callbacks are named ssd130x_$object_$operation, while the callbacks=
 for
>> > >> struct drm_*_helper_funcs are named ssd130x_$object_helper_$operati=
on.
>> > >>
>> > >> The idea is that this helper_ prefix in the function names denote t=
hat are
>> > >> for struct drm_*_helper_funcs callbacks. This convention was copied=
 from
>> > >> other drivers, when ssd130x was written but Maxime pointed out that=
 is the
>> > >> exception rather than the norm.
>> > >
>> > > I guess you found this in my code. I want to point out that I use the
>> > > _helper infix to signal that these are callback for
>> > > drm_primary_plane_helper_funcs and *not* drm_primary_plane_funcs. The
>> > > naming is intentional.
>> >
>> > Yes, that's what tried to say in the commit message and indeed I got t=
he
>> > convention from drivers in drivers/gpu/drm/tiny. In fact I believe the=
se
>> > function names are since first iteration of the driver, when was meant=
 to
>> > be a tiny driver.
>> >
>> > According to Maxime it's the exception rather than the rule and sugges=
ted
>> > to change it, I don't really have a strong opinion on either naming TB=
H.
>>
>> Maybe that's just me, but the helper in the name indeed throws me off. I=
n my
>> mind, it's supposed to be used only for helpers, not functions implement=
ing the
>> helpers hooks.

I agree with your definition of helpers. But more importantly for me is
what you mentioned, that most DRM drivers aren't using this convention
of concatenating  the driver name + struct type name + callback name.

>
> With several callbacks using the same (field) name, it is very helpful
> to name the actual implementation by combining the struct type name
> and the field name.  Anything else confuses the casual reader.

Both options have cons and pros (e.g: quickly figuring out to what struct
callback is associated as you said), but the reason I posted this patch is
to attempt making the driver more consistent with the rest of the drivers.

> Perhaps the real question is whether the structures should have "helper"
> in their name in the first place?
>

Indeed. I never fully understood why the DRM/KMS objects callbacks are
split in drm_$object_funcs and drm_$object_helper_funcs structs. AFAIU
is because the former is the minimum required and the latter is to add
additional custom behavior ?

I read this section of the documentation but still isn't clear to me:

https://dri.freedesktop.org/docs/drm/gpu/drm-kms-helpers.html

> Just my 2=E2=82=ACc as a DRM novice...
>

--=20
Best regards,

Javier Martinez Canillas
Core Platforms
Red Hat