linux-kernel - Re: [PATCH v2] gpio: mockup: Allow probing from device tree

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Message-ID: <20201029075427.t2hwvusjqx27pf6l@axis.com>
Date:   Thu, 29 Oct 2020 08:54:28 +0100
From:   Vincent Whitchurch <vincent.whitchurch@...s.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
CC:     Bartosz Golaszewski <brgl@...ev.pl>,
        Bamvor Jian Zhang <bamv2005@...il.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        kernel <kernel@...s.com>,
        devicetree <devicetree@...r.kernel.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] gpio: mockup: Allow probing from device tree

On Wed, Oct 28, 2020 at 09:25:32PM +0100, Andy Shevchenko wrote:
> On Wed, Oct 28, 2020 at 8:41 PM Bartosz Golaszewski <brgl@...ev.pl> wrote:
> > On Tue, Oct 27, 2020 at 2:54 PM Vincent Whitchurch
> > > +#ifdef CONFIG_OF
> > > +static const struct of_device_id gpio_mockup_of_match[] = {
> > > +       { .compatible = "gpio-mockup", },
> > > +       {},
> > > +};
> > > +MODULE_DEVICE_TABLE(of, gpio_mockup_of_match);
> > > +#endif
> >
> > You don't need this ifdef - of_match_ptr() will evaluate to NULL if
> > CONFIG_OF is disabled and the compiler will optimize this struct out.
> 
> It's not so. If you drop ugly ifdeffery (and I vote for that, see also
> above) the of_match_ptr() must be dropped as well.  Otherwise the
> compiler will issue the warning. So it is either all or none.

Yes, you're right.  I actually tested a !OF build before but it turns
out that the warning is disabled by default and only enabled with W=1.
I'll fix this and change the header in the next version.  Thank you.