linux-kernel - Re: [PATCH 0/3] Support timer drivers as loadable modules

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Message-ID: <20230210085157.GA175687@linaro.org>
Date:   Fri, 10 Feb 2023 09:51:57 +0100
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     John Stultz <jstultz@...gle.com>
Cc:     walter.chang@...iatek.com, Thomas Gleixner <tglx@...utronix.de>,
        Matthias Brugger <matthias.bgg@...il.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        "Maciej W . Rozycki" <macro@...am.me.uk>,
        wsd_upstream@...iatek.com, stanley.chu@...iatek.com,
        Chun-hung.Wu@...iatek.com, Freddy.Hsin@...iatek.com,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH 0/3] Support timer drivers as loadable modules

On Thu, Feb 09, 2023 at 11:50:49AM -0800, John Stultz wrote:
> On Thu, Feb 9, 2023 at 7:36 AM Daniel Lezcano <daniel.lezcano@...aro.org> wrote:
> >
> > On 08/02/2023 10:48, walter.chang@...iatek.com wrote:
> > > From: Walter Chang <walter.chang@...iatek.com>
> > >
> > > This patch exports functions in kernel so that timer drivers,
> > > such as timer-mediatek.c can become loadable modules in GKI.
> >
> > What for ?
> 
> In general, it's the same reason why modules exist: We want to be able
> to support a wide array of devices with a single kernel, but we don't
> want all devices to pay the memory cost of code that will never be
> used there. So being able to support loading device-specific bits like
> clocksources (along with other device specific logic) helps.

Agree, that is why modules are for.

> Obviously it still has to make sense, and others have raised concerns
> of stability issues if the hardware support is needed before we can
> get to module loading, but I think if this allows drivers (such as
> timer-mediatek) to be loadable safely, I see it as beneficial.

>From a technical point of view, it is arguable.

But my main concern is the real reason of changing this to the module
format. I see that as a way to overcome the effort to upstream the
drivers. And the GKI is an alibi to justify the module conversion.

Given the timers is a base brick of the core subsystems, without
proper support of the timer (eg. bug fixes), the platform support will
be wobbly.

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