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 11:48:02 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
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 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.

> 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.

Thanks,
Guenter