linux-kernel - Re: [PATCH 1/2] hwmon: gpio-fan: mark OF related data as maybe unused

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Date:   Sun, 12 Mar 2023 20:32:58 +0100
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     Jean Delvare <jdelvare@...e.com>,
        Eric Tremblay <etremblay@...tech-controls.com>,
        linux-hwmon@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] hwmon: gpio-fan: mark OF related data as maybe unused

On 12/03/2023 19:48, Guenter Roeck wrote:
> On 3/12/23 11:08, Krzysztof Kozlowski wrote:
>> On 12/03/2023 19:06, Guenter Roeck wrote:
>>> On Sat, Mar 11, 2023 at 12:16:09PM +0100, Krzysztof Kozlowski wrote:
>>>> The driver can be compile tested with !CONFIG_OF making certain data
>>>> unused:
>>>>
>>>>    drivers/hwmon/gpio-fan.c:484:34: error: ‘of_gpio_fan_match’ defined but not used [-Werror=unused-const-variable=]
>>>>
>>>
>>> How do you trigger that ? The driver depends on OF_GPIO which
>>> in turn depends on OF. Arguably that means that of_match_ptr()
>>> doesnot really make sense, but still I don't see how you can
>>> trigger the above error message.
>>
>> I can drop of_match_ptr, it's indeed in many cases not needed.
>>
>> I just build x86_64 allyesconfig minus OF, with W=1.
>>
> 
> x86_64 allyesconfig minus OF minus results in SENSORS_GPIO_FAN being
> deselected (it doesn't show up in the configuration anymore at all
> after "make olddefconfig").
> 
> $ make allyesconfig
> $ grep SENSORS_GPIO_FAN .config
> CONFIG_SENSORS_GPIO_FAN=y
> $ sed -i -e 's/CONFIG_OF=y/# CONFIG_OF is not set/' .config
> $ make olddefconfig
> #
> # configuration written to .config
> #
> $ grep SENSORS_GPIO_FAN .config
> $
> 
> I suspect what you did is to disable CONFIG_OF, and then you built
> the driver without realizing that is was deselected.

The driver would not built. I mean, I did not cheat here to built it
with incorrect config.

I rather suspect that config is broken due to:
WARNING: unmet direct dependencies detected for OF_GPIO
WARNING: unmet direct dependencies detected for GPIO_SYSCON
WARNING: unmet direct dependencies detected for MFD_STMFX

This was next-20230308

> 
>> Do you want to me to drop of_match_ptr?
>>
> 
> Yes, sure, that makes more sense. The reason though is that the
> driver depends on CONFIG_OF=y, not because of the build failure.

I'll send v2 of both patches because anyway dropping of_match_ptr is
preferred.

Best regards,
Krzysztof