linux-kernel - Re: [PATCH] iio: adc: bd79124: Add GPIOLIB dependency

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Message-ID: <CAMRc=Mf75cangdeg7T4E0nAhJs_BTdLyCu6GcrCL8vJzzAkFWg@mail.gmail.com>
Date: Wed, 13 Aug 2025 05:40:19 -0400
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Matti Vaittinen <mazziesaccount@...il.com>
Cc: Jonathan Cameron <jic23@...nel.org>, David Lechner <dlechner@...libre.com>, 
	Nuno Sá <nuno.sa@...log.com>, 
	Andy Shevchenko <andy@...nel.org>, Marcelo Schmitt <marcelo.schmitt@...log.com>, 
	Javier Carrasco <javier.carrasco.cruz@...il.com>, 
	Tobias Sperling <tobias.sperling@...ting.com>, Antoniu Miclaus <antoniu.miclaus@...log.com>, 
	Trevor Gamblin <tgamblin@...libre.com>, Esteban Blanc <eblanc@...libre.com>, 
	Linus Walleij <linus.walleij@...aro.org>, Bartosz Golaszewski <brgl@...ev.pl>, linux-gpio@...r.kernel.org, 
	linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Matti Vaittinen <matti.vaittinen@...rohmeurope.com>
Subject: Re: [PATCH] iio: adc: bd79124: Add GPIOLIB dependency

On Wed, 13 Aug 2025 11:16:06 +0200, Matti Vaittinen
<mazziesaccount@...il.com> said:
> The bd79124 has ADC inputs which can be muxed to be GPIOs. The driver
> supports this by registering a GPIO-chip for channels which aren't used
> as ADC.
>
> The Kconfig entry does not handle the dependency to GPIOLIB, which
> causes errors:
>
> ERROR: modpost: "devm_gpiochip_add_data_with_key" [drivers/iio/adc/rohm-bd79124.ko] undefined!
> ERROR: modpost: "gpiochip_get_data" [drivers/iio/adc/rohm-bd79124.ko] undefined!
>
> at linking phase if GPIOLIB is not configured to be used.
>
> Fix this by adding dependency to the GPIOLIB.
>
> Reported-by: kernel test robot <lkp@...el.com>
> Closes: https://lore.kernel.org/oe-kbuild-all/202508131533.5sSkq80B-lkp@intel.com/
> Fixes: 3f57a3b9ab74 ("iio: adc: Support ROHM BD79124 ADC")
> Signed-off-by: Matti Vaittinen <mazziesaccount@...il.com>
>

Reviewed-by: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>

> ---
>
> I am somewhat curious why the failure occurs only at the linking phase?
> Wouldn't it either be better to have these functions
> devm_gpiochip_add_data_with_key() and gpiochip_get_data() only declared
> when the CONFIG_GPIOLIB is y/m, to get errors already during
> compilation, or provide stubs?

Providing stubs is not correct for sure - a GPIO provider must always pull
in the relevant infrastructure over Kconfig. As for the former: it seems it's
a common pattern for the headers containing the "provider" part of the
subystem API, you'd get the same issue with regulators or pinctrl.

I don't have a good answer, I'd just apply this as it's not a common issue
from what I can tell.

Bartosz

> ---
>  drivers/iio/adc/Kconfig | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
> index 6de2abad0197..24f2572c487e 100644
> --- a/drivers/iio/adc/Kconfig
> +++ b/drivers/iio/adc/Kconfig
> @@ -1300,7 +1300,7 @@ config RN5T618_ADC
>
>  config ROHM_BD79124
>  	tristate "Rohm BD79124 ADC driver"
> -	depends on I2C
> +	depends on I2C && GPIOLIB
>  	select REGMAP_I2C
>  	select IIO_ADC_HELPER
>  	help
> --
> 2.50.1
>
>