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

From: Saravana Kannan <saravanak@google.com>
To: John Stultz <john.stultz@linaro.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	lkml <linux-kernel@vger.kernel.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>, Andy Gross <agross@kernel.org>,
	Bjorn Andersson <bjorn.andersson@linaro.org>,
	Joerg Roedel <joro@8bytes.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Marc Zyngier <maz@kernel.org>,
	Linus Walleij <linus.walleij@linaro.org>,
	Vinod Koul <vkoul@kernel.org>, Kalle Valo <kvalo@codeaurora.org>,
	Maulik Shah <mkshah@codeaurora.org>, Todd Kjos <tkjos@google.com>,
	linux-arm-msm <linux-arm-msm@vger.kernel.org>,
	"list@263.net:IOMMU DRIVERS <iommu@lists.linux-foundation.org>,
	Joerg Roedel <joro@8bytes.org>,"
	<iommu@lists.linux-foundation.org>,
	"open list:GPIO SUBSYSTEM" <linux-gpio@vger.kernel.org>
Subject: Re: [PATCH] firmware: QCOM_SCM: Allow qcom_scm driver to be loadable as a permenent module
Date: Wed, 21 Jul 2021 11:00:15 -0700	[thread overview]
Message-ID: <CAGETcx91URbHCYMoGt_cCgvMXNkVyJb4Ek-ng8jwR+eQhvZN1A@mail.gmail.com> (raw)
In-Reply-To: <CALAqxLUVgUT+1DyDGsFbF0138S0OYzpKADk__PsYbR4B4mbMhw@mail.gmail.com>

On Wed, Jul 21, 2021 at 10:24 AM John Stultz <john.stultz@linaro.org> wrote:
>
> On Wed, Jul 21, 2021 at 4:54 AM Greg Kroah-Hartman
> <gregkh@linuxfoundation.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