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Date:   Fri, 16 Dec 2022 05:08:53 +0100
From:   Nicolas Schier <nicolas@fjasle.eu>
To:     Luis Chamberlain <mcgrof@kernel.org>
Cc:     masahiroy@kernel.org, nathan@kernel.org, ndesaulniers@google.com,
        linux-kbuild@vger.kernel.org, alison.schofield@intel.com,
        dan.j.williams@intel.com, dave@stgolabs.net,
        a.manzanares@samsung.com, lucas.de.marchi@gmail.com,
        linux-cxl@vger.kernel.org, linux-modules@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH] kbuild: Modify default INSTALL_MOD_DIR from extra to
 updates
Message-ID: <Y5vvVTwt+FfxTUke@bergen.fjasle.eu>
References: <20221214231718.1002194-1-mcgrof@kernel.org>
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On Wed 14 Dec 2022 15:17:18 GMT, Luis Chamberlain wrote:
> The default INSTALL_MOD_DIR of using the /lib/modules/$(uname -r)/extra
> directory for external modules assumes distributions will have something
> like  /etc/depmod.d/dist.conf with:
>=20
> search updates extra built-in
>=20
> However, only some Red Hat release have and use the extra stuff for
> years now. Meanwhile, the depmod.c tool in kmod has *forever* used
> the "updates" directory as part of the search path by default *if*
> your distribution does not have any depmod.d configuration.
>=20
> If you compile and install an external module today, even upstream
> kernel mock drivers (tools/testing/cxl) the modules_install target
> will pick up the new drivers but will not allow override of drivers
> from updates to override built-in ones.
>=20
> Since module-init-tools was deprecated over 11 years ago and now kmod
> has since its inception used the "updates" directory as part of its
> default search path to allow overrides, and since the "extra" stuff
> was in practice only used by Red Hat stuff, use the more distro
> agnostic override path "updates" to allow external modules to
> also override proper production kernel modules.
>=20
> This would allow mocking drivers tools to not have to muck with
> depmod.d config files or assume that your distro will have extra
> on a configuration file over built-in.
>=20
> With today's default you end up actually *crashing* Linux when
> trying to load cxl_test with the default "extra" [0] directory being
> used. This fixes that and allows other mocking drivers to do
> less work.
>=20
> [0] https://lkml.kernel.org/r/20221209062919.1096779-1-mcgrof@kernel.org
> Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
> ---
>  scripts/Makefile.modinst | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>=20

Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>


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