linux-kernel - Re: Kconfig rules (depends, imply)

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Date:   Wed, 1 Jun 2022 12:03:11 +0530
From:   Muni Sekhar <munisekharrms@...il.com>
To:     Randy Dunlap <rdunlap@...radead.org>
Cc:     kernelnewbies <kernelnewbies@...nelnewbies.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: Kconfig rules (depends, imply)

Thank you for the clarification.

On Wed, Jun 1, 2022 at 1:55 AM Randy Dunlap <rdunlap@...radead.org> wrote:
>
> Hi--
>
> On 5/31/22 05:14, Muni Sekhar wrote:
> > Hi all,
> >
> > menuconfig SOUNDWIRE
> >         tristate "SoundWire support"
> >         depends on ACPI || OF
> >
> > "depends on ACPI || OF" mean, SOUNDWIRE depends on both ACPI and OF modules?
> >
>
> "||" is logical OR, so SOUNDWIRE depends on either ACPI or OF (or both
> of them can be enabled).
>
>
> >
> > config SOUNDWIRE_QCOM
> >         tristate "Qualcomm SoundWire Master driver"
> >         imply SLIMBUS
> >
> > What does "imply SLIMBUS" mean?
>
> See Documentation/kbuild/kconfig-language.rst:
>
> - weak reverse dependencies: "imply" <symbol> ["if" <expr>]
>
>   This is similar to "select" as it enforces a lower limit on another
>   symbol except that the "implied" symbol's value may still be set to n
>   from a direct dependency or with a visible prompt.
>
> So (in your example) SLIMBUS is desired but not required.
> That means that the code that is built for SOUNDWIRE_QCOM
> probably needs to use IS_REACHABLE(CONFIG_SLIMBUS) to
> see if that SLIMBUS code is available at build time.
>
> HTH.
> --
> ~Randy



-- 
Thanks,
Sekhar