Re: [PATCH 10/10] ACPI: IORT: Allow COMPILE_TEST of IORT

From: Jason Gunthorpe <jgg@nvidia.com>
To: Lorenzo Pieralisi <lpieralisi@kernel.org>
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Subject: Re: [PATCH 10/10] ACPI: IORT: Allow COMPILE_TEST of IORT
Date: Wed, 29 Nov 2023 15:12:40 -0400	[thread overview]
Message-ID: <20231129191240.GZ436702@nvidia.com> (raw)
In-Reply-To: <ZWc0qPWzNWPkL8vt@lpieralisi>

On Wed, Nov 29, 2023 at 01:55:04PM +0100, Lorenzo Pieralisi wrote:

> I don't think it should be done this way. Is the goal compile testing
> IORT code ? 

Yes

> If so, why are we forcing it through the SMMU (only because
> it can be compile tested while eg SMMUv3 driver can't ?) menu entry ?

Because something needs to select it, and SMMU is one of the places
that are implicitly using it.

It isn't (and shouldn't be) a user selectable kconfig. Currently the
only thing that selects it is the ARM64 master kconfig.

> This looks a bit artificial (and it is unclear from the Kconfig
> file why only that driver selects IORT, it looks like eg the SMMUv3
> does not have the same dependency - there is also the SMMUv3 perf
> driver to consider).

SMMUv3 doesn't COMPILE_TEST so it picks up the dependency transitivity
through ARM64. I'm not sure why IORT was put as a global ARM64 kconfig
dependency and not put in the places that directly need it.

"perf driver" ? There is a bunch of GIC stuff that uses this too but I
don't know if it compile tests.

> Maybe we can move IORT code into drivers/acpi and add a silent config
> option there with a dependency on ARM64 || COMPILE_TEST.

That seems pretty weird to me, this is the right way to approach it,
IMHO. Making an entire directory condition is pretty incompatible with
COMPILE_TEST as a philosophy.

> Don't know but at least it is clearer. As for the benefits of compile
> testing IORT code - yes the previous patch is a warning to fix but
> I am not so sure about the actual benefits.

IMHO COMPILE_TEST is an inherently good thing. It makes development
easier for everyone because you have a less fractured code base to
work with.

Jason