Re: [PATCH v8 3/7] mux: add help text for MULTIPLEXER config option

[Geert Uytterhoeven]

Hi Josua,

On Mon, 9 Feb 2026 at 11:47, Josua Mayer <josua@xxxxxxxxxxxxx> wrote:
> On 09/02/2026 12:17, Geert Uytterhoeven wrote:
> > On Mon, 9 Feb 2026 at 11:12, Josua Mayer <josua@xxxxxxxxxxxxx> wrote:
> >> On 09/02/2026 10:06, Geert Uytterhoeven wrote:
> >>> On Sun, 8 Feb 2026 at 16:16, Josua Mayer <josua@xxxxxxxxxxxxx> wrote:
> >>>> On 03/02/2026 15:01, Josua Mayer wrote:
> >>>>> Add prompt and help text for CONFIG_MULTIPLEXER to allow enabling this
> >>>>> option thorugh the kernel configuration without explicit "select" driver
> >>>>> dependencies.
> >>>>>
> >>>>> Select it by default when COMPILE_TEST is set for better coverage.
> >>>>>
> >>>>> Signed-off-by: Josua Mayer <josua@xxxxxxxxxxxxx>
> >>>>> ---
> >>>>>     drivers/mux/Kconfig | 8 +++++++-
> >>>>>     1 file changed, 7 insertions(+), 1 deletion(-)
> >>>>>
> >>>>> diff --git a/drivers/mux/Kconfig b/drivers/mux/Kconfig
> >>>>> index c68132e38138..e31c46820bdf 100644
> >>>>> --- a/drivers/mux/Kconfig
> >>>>> +++ b/drivers/mux/Kconfig
> >>>>> @@ -4,7 +4,13 @@
> >>>>>     #
> >>>>>
> >>>>>     config MULTIPLEXER
> >>>>> -     tristate
> >>>>> +     tristate "Generic Multiplexer Support" if COMPILE_TEST
> >>>> This didn't do what I thought it would.
> >>>> It was my intention to allow enabling this through menuconfig / .config.
> >>>>
> >>>> With the syntax above menuconfig shows:
> >>>>
> >>>> │ Symbol: MULTIPLEXER [=n]
> >>>> │ Type  : tristate
> >>>> │ Defined at drivers/mux/Kconfig:6
> >>>> │   Prompt: Generic Multiplexer Support
> >>>> │   Visible if: COMPILE_TEST [=n]
> >>>>
> >>>> This means it cannot be selected.
> >>> Looks like you haven't enabled COMPILE_TEST first?
> >> Correct.
> >> But CONFIG_MULTIPLEXER should be visible always,
> >> not just when COMPILE_TEST is set.
> > Why should it always be visible? All users select it?
>
> This is not relevant for v7 now and can be handled later.
>
> It was discussed previously that drivers supporting optional muxes
> do not need to "select" MULTIPLEXER through Kconfig,
> E.g. the renesas sdhi driver.
>
> However other drivers are already selecting it even though the mux
> is optional, see e.g. phy-can-transceiver.
>
> In order to support muxes in renesas sdhi driver e.g., users must choose to
> enable both the renesas driver, and multiplexer subsystem via the
> configuration.
>
> The mux core standalone also supports a limited use-case without other
> driver
> interactions, setting idle-state e.g.:
>
> mux-controller {
>      compatible = "gpio-mux";
>      #mux-control-cells = <0>;
>      mux-gpios = <&tca6416_u20 0 GPIO_ACTIVE_HIGH>;
>      idle-state = <0>;
> };
>
> So it can be generally useful for a user to enable CONFIG_MULTIPLEXER.

Then please say so in the patch description.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds