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    SubjectRe: [PATCH v2] gpio: winbond: add driver
    On Wed, Dec 27, 2017 at 1:24 AM, William Breathitt Gray
    <vilhelm.gray@gmail.com> wrote:

    > Here are the error messages printed on my system when I add a select
    > ISA_BUS_API line to the GPIO_WINBOND Kconfig option in the version 2 of
    > your patch:
    >
    > drivers/gpio/Kconfig:13:error: recursive dependency detected!
    > For a resolution refer to Documentation/kbuild/kconfig-language.txt
    > subsection "Kconfig recursive dependency limitations"
    > drivers/gpio/Kconfig:13: symbol GPIOLIB is selected by STX104
    > For a resolution refer to Documentation/kbuild/kconfig-language.txt
    > subsection "Kconfig recursive dependency limitations"
    > drivers/iio/adc/Kconfig:659: symbol STX104 depends on ISA_BUS_API
    > For a resolution refer to Documentation/kbuild/kconfig-language.txt
    > subsection "Kconfig recursive dependency limitations"
    > arch/Kconfig:818: symbol ISA_BUS_API is selected by GPIO_WINBOND
    > For a resolution refer to Documentation/kbuild/kconfig-language.txt
    > subsection "Kconfig recursive dependency limitations"
    > drivers/gpio/Kconfig:701: symbol GPIO_WINBOND depends on GPIOLIB

    So STX104 depends on ISA_BUS_API which in turn is
    selected by GPIO_WINBOND which also depends on GPIOLIB.

    > The issue seems to relate to the select GPIOLIB line for the STX104
    > Kconfig option (which has a ISA_BUS_API dependency). Switching GPIOLIB
    > to be a dependency, or alternatively selecting ISA_BUS_API, alleviates
    > the recursion.
    >
    > Linus, is my use of select GPIOLIB for the STX104 Kconfig option
    > appropriate in this context -- or should it instead be part of the
    > depends on line? The STX104 driver includes linux/gpio/driver.h and
    > makes use of the devm_gpiochip_add_data function to add support for some
    > minor auxililary GPIO lines on the STX104 device.

    In the STX104 case, it seems to be appropriate to
    select GPIOLIB, as it is a GPIO provider, not consumer.

    Usually I prefer that drivers just select what they need so I don't
    have to run around in the whole kernel tree and turn things on
    to the left and right before I can finally select my driver, but
    maybe that is just me.

    The other ISA GPIO drivers depends on ISA_BUS_API, I guess
    in difference from the symbol GPIOLIB it cannot be universally
    selected, so shouldn't this driver also just depends on ISA_BUS_API
    and select it from the machine or wherever?

    Yours,
    Linus Walleij

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