linux-kernel - Re: [PATCH v4 02/11] mfd: Add support for Kontron sl28cpld management controller

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Date:   Fri, 5 Jun 2020 13:48:27 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Michael Walle <michael@...le.cc>
Cc:     "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-hwmon@...r.kernel.org, linux-pwm@...r.kernel.org,
        linux-watchdog@...r.kernel.org,
        linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Rob Herring <robh+dt@...nel.org>,
        Jean Delvare <jdelvare@...e.com>,
        Guenter Roeck <linux@...ck-us.net>,
        Lee Jones <lee.jones@...aro.org>,
        Thierry Reding <thierry.reding@...il.com>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>,
        Wim Van Sebroeck <wim@...ux-watchdog.org>,
        Shawn Guo <shawnguo@...nel.org>, Li Yang <leoyang.li@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jason Cooper <jason@...edaemon.net>,
        Marc Zyngier <maz@...nel.org>, Mark Brown <broonie@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Subject: Re: [PATCH v4 02/11] mfd: Add support for Kontron sl28cpld management controller

On Fri, Jun 5, 2020 at 1:09 PM Michael Walle <michael@...le.cc> wrote:
> Am 2020-06-05 10:01, schrieb Andy Shevchenko:
> > On Fri, Jun 5, 2020 at 12:16 AM Michael Walle <michael@...le.cc> wrote:

...

> >> +       bool "Kontron sl28 core driver"
> >> +       depends on I2C=y
> >
> > Why not module?
>
> There are users of the interupt lines provided by the interrupt
> controller.
> For example, the gpio-button driver. If this is compiled into the kernel
> (which it is by default in the arm64 defconfig), probing will fail
> because
> the interrupt is not found. Is there a better way for that? I guess the
> same
> is true for the GPIO driver.

And GPIO nicely handles this via deferred probe mechanism. Why it
can't be used here?
So, we really need to have a strong argument to limit module nowadays
to be only builtin.

...

> >> +       depends on OF
> >
> > I didn't find an evidence this is needed.

> >> +#include <linux/of_platform.h>
> >
> > No evidence of user of this.
> > I think you meant mod_devicetable.h.
>
> devm_of_platform_populate(), so I need CONFIG_OF, too right?

Ah, this explains header, thanks!
But it doesn't explain depends OF.

So, perhaps,

depends OF || COMPILE_TEST will be more informative, i.e.
tells "okay, this driver can be compiled w/o OF, but won't be functional".

-- 
With Best Regards,
Andy Shevchenko