linux-kernel - Re: [PATCH v1 3/3] mmc: Add driver for LiteX's LiteSDCard interface

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Message-ID: <CAMuHMdXvHYB++NDCxgBkyhvxu57pGYVGUN4rcr=g+pXoUK+ZQw@mail.gmail.com>
Date:   Tue, 7 Dec 2021 09:01:41 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Joel Stanley <joel@....id.au>
Cc:     Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        Gabriel Somlo <gsomlo@...il.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Rob Herring <robh+dt@...nel.org>,
        devicetree <devicetree@...r.kernel.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        linux-mmc <linux-mmc@...r.kernel.org>,
        Karol Gugala <kgugala@...micro.com>,
        Mateusz Holenko <mholenko@...micro.com>,
        Kamil Rakoczy <krakoczy@...micro.com>,
        mdudek@...ernships.antmicro.com,
        Paul Mackerras <paulus@...abs.org>,
        Stafford Horne <shorne@...il.com>,
        david.abdurachmanov@...ive.com,
        Florent Kermarrec <florent@...oy-digital.fr>
Subject: Re: [PATCH v1 3/3] mmc: Add driver for LiteX's LiteSDCard interface

Hi Joel,

On Tue, Dec 7, 2021 at 12:51 AM Joel Stanley <joel@....id.au> wrote:
> On Mon, 6 Dec 2021 at 12:16, Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
> > > > +       depends on OF && LITEX
> > >
> > > I don't like having litex drivers depend on the LITEX kconfig. The
> > > symbol is not user visible, and to enable it we need to build in the
> > > litex controller driver, which platforms may or may not have.
> > >
> > > The microwatt platform is an example of a SoC that embeds some LITEX
> > > IP, but may or may not be a litex SoC.
> >
> > I do like the LITEX dependency, as it allows us to gate off a bunch of
> > related drivers, and avoid annoying users with questions about them,
> > using a single symbol.
>
> I appreciate your concern.
>
> We could do this:
>
>         depends on PPC_MICROWATT || LITEX || COMPILE_TEST
>
> It's unfortunate that kconfig doesn't let us describe the difference
> between "this driver requires this symbol" as it won't build and "this
> driver is only useful when this symbol is enabled". Traditionally I
> write kconfig to represent only the former, whereas you prefer both.

The former is expressed using:

    depends on FOO

The latter using:

    depends on BAR || COMPILE_TEST

Traditionally we only had the former. But with the introduction of
more and more dummy symbols for the !CONFIG_BAR case, the amount of
questions asked during configuration has become overwhelming.  At the
current pace, we'll reach 20K config symbols by v5.24 or so...

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

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