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From:   Geert Uytterhoeven <geert@linux-m68k.org>
Date:   Thu, 21 Sep 2023 10:46:05 +0200
Message-ID: <CAMuHMdV9Q=F6D=FgBYazjxGL8HY1cRLJUxdfdvr8=6fwgn+EHQ@mail.gmail.com>
Subject: Re: [PATCH] drm/ssd130x: Drop _helper prefix from struct
 drm_*_helper_funcs callbacks
To:     Maxime Ripard <mripard@kernel.org>
Cc:     Javier Martinez Canillas <javierm@redhat.com>,
        Thomas Zimmermann <tzimmermann@suse.de>,
        linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org
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Hi Maxime,

On Thu, Sep 21, 2023 at 10:12 AM Maxime Ripard <mripard@kernel.org> wrote:
> On Thu, Sep 21, 2023 at 09:57:22AM +0200, Geert Uytterhoeven wrote:
> > On Thu, Sep 21, 2023 at 9:44 AM 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_$object_helper_$operation.
> > > > >>
> > > > >> The idea is that this helper_ prefix in the function names denote that 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 the
> > > > convention from drivers in drivers/gpu/drm/tiny. In fact I believe these
> > > > 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 suggested
> > > > to change it, I don't really have a strong opinion on either naming TBH.
> > >
> > > Maybe that's just me, but the helper in the name indeed throws me off. In my
> > > mind, it's supposed to be used only for helpers, not functions implementing the
> > > helpers hooks.
> >
> > 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.
>
> I can't think of any (at least for a given object). Which one do you have in
> mind?

E.g. atomic_check():

    drm_crtc_helper_funcs.atomic_check()
    drm_encoder_helper_funcs.atomic_check()
    drm_connector_helper_funcs.atomic_check()
    drm_plane_helper_funcs.atomic_check()

Interestingly, drm_mode_config_helper_funcs does not have an
atomic_check() callback, but drm_mode_config_funcs has.

> > Anything else confuses the casual reader. Perhaps the real question is whether
> > the structures should have "helper" in their name in the first place?
>
> Those structures are meant for functions used by the helpers, they are not
> helper functions.

That might be how they started, but to me it looks like all these helpers
are no longer helpers, but part of the core...

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds