linux-kernel - Re: [PATCH 2/2] touchscreen: goodix: define GPIO mapping for GPD P2 Max

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Date:   Fri, 30 Aug 2019 21:16:59 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Peter Cai <peter@...eblog.net>
Cc:     Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Bastien Nocera <hadess@...ess.net>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>, linux-gpio@...r.kernel.org,
        linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-input@...r.kernel.org
Subject: Re: [PATCH 2/2] touchscreen: goodix: define GPIO mapping for GPD P2
 Max

On Fri, Aug 30, 2019 at 11:15:27PM +0800, Peter Cai wrote:
> On Fri, Aug 30, 2019, 7:55 PM Andy Shevchenko <
> andriy.shevchenko@...ux.intel.com> wrote:

> > I guess most of these #ifdef:s makes code less readable for exchange of
> saving
> few bytes in the module footprint.
> 
> Well since they can only be used when ACPI is supported

> (devm_acpi_dev_add_driver_gpios does not exist without ACPI defined, thus
> the last guard must exist),

This is not correct.

> if they were not guarded then we would be left
> with a bunch of unused variables warnings when building without ACPI which
> doesn't seem good.

Good / no-good is only matter of few dozens of bytes here and there to be saved.

> Should we use __maybe_unused here instead of #ifdef guards?

No, it won't make sense, because the structures will be part of
_add_driver_gpio() call, due to which compiler likely can't recognize unused
structures. However, you may try with warnings enabled `make W=1`.

> > Comma at the end?
> 
> I was trying to follow the style of this driver but it doesn't seem to be
> really consistent within itself. Another dmi_system_id definition in the
> same file mixed both styles so I was kind of confused.

I see. So, this is for Dmitry's preferences.

-- 
With Best Regards,
Andy Shevchenko