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

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Date:   Fri, 05 Jun 2020 13:51:09 +0200
From:   Michael Walle <michael@...le.cc>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
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

Am 2020-06-05 12:48, schrieb Andy Shevchenko:
> 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.

Was that a question for me? TBH thats how other interrupt drivers doing
it for now. And it would be the users who need to be fixed, right? Or
even the platform code? Because it will complain with

[    2.962990] irq: no irq domain found for interrupt-controller@1c !
[    2.975762] gpio-keys buttons0: Found button without gpio or irq
[    2.981872] gpio-keys: probe of buttons0 failed with error -22

>> >> +       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".

ok


-- 
-michael