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From: Will Deacon <will@kernel.org>
To: John Stultz <john.stultz@linaro.org>
Cc: Maulik Shah <mkshah@codeaurora.org>,
	Jason Cooper <jason@lakedaemon.net>,
	Saravana Kannan <saravanak@google.com>,
	Marc Zyngier <maz@kernel.org>,
	lkml <linux-kernel@vger.kernel.org>,
	Lina Iyer <ilina@codeaurora.org>,
	linux-gpio@vger.kernel.org, iommu@lists.linux-foundation.org,
	Andy Gross <agross@kernel.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Linus Walleij <linus.walleij@linaro.org>,
	linux-arm-msm <linux-arm-msm@vger.kernel.org>,
	Todd Kjos <tkjos@google.com>
Subject: Re: [PATCH v2 5/5] firmware: QCOM_SCM: Allow qcom_scm driver to be loadable as a permenent module
Date: Fri, 10 Jul 2020 08:54:12 +0100	[thread overview]
Message-ID: <20200710075411.GA30011@willie-the-truck> (raw)
In-Reply-To: <CALAqxLVZ2EhutYjOt7Be1RgnYwHT6-4m6DxA-t1wuxuSy=6yDQ@mail.gmail.com>

On Thu, Jul 09, 2020 at 08:28:45PM -0700, John Stultz wrote:
> On Thu, Jul 2, 2020 at 7:18 AM Will Deacon <will@kernel.org> wrote:
> > On Thu, Jun 25, 2020 at 12:10:39AM +0000, John Stultz wrote:
> > > diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
> > > index b510f67dfa49..714893535dd2 100644
> > > --- a/drivers/iommu/Kconfig
> > > +++ b/drivers/iommu/Kconfig
> > > @@ -381,6 +381,7 @@ config SPAPR_TCE_IOMMU
> > >  config ARM_SMMU
> > >       tristate "ARM Ltd. System MMU (SMMU) Support"
> > >       depends on (ARM64 || ARM || (COMPILE_TEST && !GENERIC_ATOMIC64)) && MMU
> > > +     depends on QCOM_SCM || !QCOM_SCM #if QCOM_SCM=m this can't be =y
> > >       select IOMMU_API
> > >       select IOMMU_IO_PGTABLE_LPAE
> > >       select ARM_DMA_USE_IOMMU if ARM
> >
> > This looks like a giant hack. Is there another way to handle this?
> 
> Sorry for the slow response here.
> 
> So, I agree the syntax looks strange (requiring a comment obviously
> isn't a good sign), but it's a fairly common way to ensure drivers
> don't get built in if they optionally depend on another driver that
> can be built as a module.
>   See "RFKILL || !RFKILL", "EXTCON || !EXTCON", or "USB_GADGET ||
> !USB_GADGET" in various Kconfig files.
> 
> I'm open to using a different method, and in a different thread you
> suggested using something like symbol_get(). I need to look into it
> more, but that approach looks even more messy and prone to runtime
> failures. Blocking the unwanted case at build time seems a bit cleaner
> to me, even if the syntax is odd.

Maybe just split it out then, so that the ARM_SMMU entry doesn't have this,
as that driver _really_ doesn't care about SoC details like this. In other
words, add a new entry along the lines of:

	config ARM_SMMU_QCOM_IMPL
	default y
	#if QCOM_SCM=m this can't be =y
	depends on ARM_SMMU & (QCOM_SCM || !QCOM_SCM)

and then have arm-smmu.h provide a static inline qcom_smmu_impl_init()
which returns -ENODEV if CONFIG_ARM_SMMU_QCOM_IMPL=n and hack the Makefile
so that we don't bother to compile arm-smmu-qcom.o in that case.

Would that work?

Will
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  reply	other threads:[~2020-07-10  7:54 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-25  0:10 [PATCH v2 0/5] Allow for qcom-pdc, pinctrl-msm and qcom-scm drivers to be loadable as modules John Stultz
2020-06-25  0:10 ` [PATCH v2 1/5] irq: irqdomain: Export irq_domain_update_bus_token John Stultz
2020-06-25  0:10 ` [PATCH v2 2/5] irq: irqchip: Export irq_chip_retrigger_hierarchy and irq_chip_set_vcpu_affinity_parent John Stultz
2020-06-25  0:10 ` [PATCH v2 3/5] irqchip: Allow QCOM_PDC to be loadable as a permanent module John Stultz
2020-06-26  7:42   ` Stephen Boyd
2020-06-27  1:34     ` John Stultz
2020-06-27  9:37       ` Marc Zyngier
2020-07-10  6:02         ` Stephen Boyd
2020-07-10 22:44           ` John Stultz
2020-07-10 23:27             ` Stephen Boyd
2020-07-12  9:27               ` Marc Zyngier
2020-06-25  0:10 ` [PATCH v2 4/5] pinctrl: qcom: Allow pinctrl-msm code to be loadable as a module John Stultz
2020-06-25  0:10 ` [PATCH v2 5/5] firmware: QCOM_SCM: Allow qcom_scm driver to be loadable as a permenent module John Stultz
2020-07-02 12:47   ` Greg Kroah-Hartman
2020-07-02 14:18   ` Will Deacon
2020-07-10  3:28     ` John Stultz
2020-07-10  7:54       ` Will Deacon [this message]
2020-07-10 22:21         ` John Stultz
2020-07-13 20:41           ` Will Deacon
2020-07-13 20:48             ` John Stultz
2020-07-14  7:56               ` Will Deacon
2020-10-28  5:53             ` John Stultz
2020-10-28 13:51               ` Will Deacon
2020-10-28 14:51                 ` Robin Murphy
2020-10-30  1:02                   ` John Stultz
2020-10-30 14:12                     ` Robin Murphy
2020-10-31  0:12                       ` John Stultz
2020-10-30  6:09                 ` John Stultz

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