linux-kernel - Re: [PATCH] firmware: QCOM_SCM: Allow qcom_scm driver to be loadable as a permenent module

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Message-ID: <CAGETcx91URbHCYMoGt_cCgvMXNkVyJb4Ek-ng8jwR+eQhvZN1A@mail.gmail.com>
Date:   Wed, 21 Jul 2021 11:00:15 -0700
From:   Saravana Kannan <saravanak@...gle.com>
To:     John Stultz <john.stultz@...aro.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Joerg Roedel <joro@...tes.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Marc Zyngier <maz@...nel.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Vinod Koul <vkoul@...nel.org>,
        Kalle Valo <kvalo@...eaurora.org>,
        Maulik Shah <mkshah@...eaurora.org>,
        Todd Kjos <tkjos@...gle.com>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        "list@....net:IOMMU DRIVERS <iommu@...ts.linux-foundation.org>, Joerg
        Roedel <joro@...tes.org>," <iommu@...ts.linux-foundation.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>
Subject: Re: [PATCH] firmware: QCOM_SCM: Allow qcom_scm driver to be loadable
 as a permenent module

On Wed, Jul 21, 2021 at 10:24 AM John Stultz <john.stultz@...aro.org> wrote:
>
> On Wed, Jul 21, 2021 at 4:54 AM Greg Kroah-Hartman
> <gregkh@...uxfoundation.org> wrote:
> >
> > On Wed, Jul 07, 2021 at 04:53:20AM +0000, John Stultz wrote:
> > > Allow the qcom_scm driver to be loadable as a permenent module.
> >
> > This feels like a regression, it should be allowed to be a module.
>
> I'm sorry, I'm not sure I'm following you, Greg.  This patch is trying
> to enable the driver to be able to be loaded as a module.

I think the mix up might be that Greg mentally read "permanent module"
as "builtin"?

"permanent module" is just something that can't be unloaded once it's
loaded. It's not "builtin".

-Saravana

>
> > > This still uses the "depends on QCOM_SCM || !QCOM_SCM" bit to
> > > ensure that drivers that call into the qcom_scm driver are
> > > also built as modules. While not ideal in some cases its the
> > > only safe way I can find to avoid build errors without having
> > > those drivers select QCOM_SCM and have to force it on (as
> > > QCOM_SCM=n can be valid for those drivers).
> > >
> > > Reviving this now that Saravana's fw_devlink defaults to on,
> > > which should avoid loading troubles seen before.
> >
> > fw_devlink was supposed to resolve these issues and _allow_ code to be
> > built as modules and not forced to be built into the kernel.
>
> Right. I'm re-submitting this patch to enable a driver to work as a
> module, because earlier attempts to submit it ran into boot trouble
> because fw_devlink wasn't yet enabled.
>
> I worry something in my description made it seem otherwise, so let me
> know how you read it and I'll try to avoid such confusion in the
> future.
>
> thanks
> -john