linux-kernel - Re: [PATCH V2 1/4] gpio: mxc: Support module build

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Message-ID: <CACRpkdb4CCNYtMpPOAB6hF8gSCHa4NtpO8TzH0pVEuh-Spe44w@mail.gmail.com>
Date:   Tue, 28 Jul 2020 10:09:33 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Anson Huang <anson.huang@....com>,
        Russell King - ARM Linux <linux@...linux.org.uk>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Sascha Hauer <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Peter Chen <peter.chen@....com>,
        "oleksandr.suvorov@...adex.com" <oleksandr.suvorov@...adex.com>,
        Andreas Kemnade <andreas@...nade.info>,
        Peng Fan <peng.fan@....com>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        Olof Johansson <olof@...om.net>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Alexandre Torgue <alexandre.torgue@...com>,
        Patrice Chotard <patrice.chotard@...com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Joel Stanley <joel@....id.au>, Lubomir Rintel <lkundrak@...sk>,
        Christian Gmeiner <christian.gmeiner@...il.com>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Leo Li <leoyang.li@....com>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        "michael@...le.cc" <michael@...le.cc>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        dl-linux-imx <linux-imx@....com>
Subject: Re: [PATCH V2 1/4] gpio: mxc: Support module build

On Mon, Jul 27, 2020 at 1:57 PM Arnd Bergmann <arnd@...db.de> wrote:

> Overall, my feeling is that making sure all drivers that depend on the pinctrl
> driver can deal with deferred probing is a prerequisite before this can be
> made a loadable module itself (same for clk, irqchip, etc drivers that others
> may rely on).
>
> I understand that your primary motivation is to fit into Google's GKI framework,
> but I think that doing the conversion only partially would neither serve to
> improve the kernel nor actually meet the GKI requirements.

This has been my worry as well when it comes to these GKI-initiated
patches that are flying right now.

> Most pinctrl drivers are currently always built-in to work around the
> load order dependencies. This of course is a bit of a hack and we'd be
> better off if all drivers managed to avoid the dependencies, but this
> can also require a lot of work.

Several people have argued that it is reasonable to cut corners to
achieve the "greater good" of GKI.

I try to handle it on a "does the kernel look better after than
before" basis, while pushing gently for at least trying to
properly modularize the whole thing. It can become pretty hard
to test I think. If it is things like GPIO expanders on I2C
that can be used by several SoCs I would be more hard on
this, on a single SoC not as much.

One discussion thread got inflamed because of ARM vs x86
discussions "x86 is better modularized" which is something I want
to avoid, it is easy to be modularized when your irqs, clocks,
regulators and pins are handled by the BIOS. This is a SoC
problem and x86 SoCs with no BIOS, RISCV, ARM and whatever
doesn't have a fix-it-all-BIOS have this problem. :/

Yours,
Linus Walleij