linux-kernel - Re: [PATCH v2 3/5] gpio: msc313: MStar MSC313 GPIO driver

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Date:   Thu, 5 Nov 2020 10:30:28 +0100
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Daniel Palmer <daniel@...f.com>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        arm-kernel@...ts.infradead.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 3/5] gpio: msc313: MStar MSC313 GPIO driver

On Tue, Oct 20, 2020 at 1:59 PM Andy Shevchenko
<andy.shevchenko@...il.com> wrote:
> On Mon, Oct 19, 2020 at 5:11 PM Daniel Palmer <daniel@...f.com> wrote:

> > +config GPIO_MSC313
> > +       bool "MStar MSC313 GPIO support"

> > +       default y if ARCH_MSTARV7

I think it is possible to write:

default ARCH_MSTARV7

For this.

> Why boolean?

I answered this question in some other mail but there is usually somewhat
a good reason for this but let's discuss it a bit.

The following usecase:

- You have a generic distribution such as Android

- The generic distribution does not use initramfs to support basic
  drivers (does Android? Nowadays?)

- So all modules would need to load from actual storage media.

- The storage media is an SD card.

- The SD card reader has a card detect line connected to one
  of the GPIO lines.

- Now we have catch-22 because there is no way to load the
  GPIO driver modules from the storage media because the
  driver is needed to mount the storage media.

I do not know if this "never happens" because every generic
distribution "should" be using initramfs for their drivers. But it
provides a convenient way for users to shoot themselves in the
foot and be frustrated about that their root filesystem is not
mounting.

I do not think this is limited to GPIO card detects but it is a very
immediate example.

What is the consensus here?

Yours,
Linus Walleij