linux-kernel - Re: [PATCH] drm/tegra: vic: fix unused-function warnings

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Date:   Wed, 6 Apr 2022 17:51:59 +0200
From:   Arnd Bergmann <arnd@...nel.org>
To:     Thierry Reding <thierry.reding@...il.com>
Cc:     David Airlie <airlied@...ux.ie>, Daniel Vetter <daniel@...ll.ch>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Dmitry Osipenko <digetx@...il.com>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Arnd Bergmann <arnd@...db.de>,
        Mikko Perttunen <mperttunen@...dia.com>,
        Robin Murphy <robin.murphy@....com>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        "open list:TEGRA ARCHITECTURE SUPPORT" <linux-tegra@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drm/tegra: vic: fix unused-function warnings

On Wed, Apr 6, 2022 at 3:21 PM Thierry Reding <thierry.reding@...il.com> wrote:
> On Wed, Mar 16, 2022 at 07:36:47PM +0100, Arnd Bergmann wrote:
> >  static const struct dev_pm_ops vic_pm_ops = {
> > -     SET_RUNTIME_PM_OPS(vic_runtime_suspend, vic_runtime_resume, NULL)
> > -     SET_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend,
> > -                             pm_runtime_force_resume)
> > +     RUNTIME_PM_OPS(vic_runtime_suspend, vic_runtime_resume, NULL)
> > +     SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend, pm_runtime_force_resume)
> >  };
> >
> >  struct platform_driver tegra_vic_driver = {
>
> Hi Arnd,
>
> is this a replacement for __maybe_unused annotations that we would
> typically use to address these? Is the ternary operator in PTR_IF enough
> to eliminate the warning? Does that work the same way for structure
> definitions as it does for conditionals where we use IS_ENABLED() to use
> the compiler's DCE for improved coverage?

Yes to all three.

> It looks like it, but just making sure because there's another patch
> that fixes this warning by adding __maybe_unused.

I sent a lot of patches in the past to add __maybe_unused, but this was
mainly because we could never come up with a good replacement.
Paul Cercueil has finally come up with a good solution, so this is how
we should do it from now on.

        Arnd