linux-kernel - Question about ARM FASTFPE

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Message-ID: <CAK7LNASSCvLSXVikR7GenXyb8KywpWKVc1Z=5v3c93rxJ+G73w@mail.gmail.com>
Date:   Wed, 10 Jul 2019 13:30:24 +0900
From:   Masahiro Yamada <yamada.masahiro@...ionext.com>
To:     Russell King <linux@...linux.org.uk>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        Olof Johansson <olof@...om.net>, Arnd Bergmann <arnd@...db.de>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        masahiroy@...nel.org
Subject: Question about ARM FASTFPE

Hi.

I have a question about the following code
in arch/arm/Makefile:

# Do we have FASTFPE?
FASTFPE :=arch/arm/fastfpe
ifeq ($(FASTFPE),$(wildcard $(FASTFPE)))
FASTFPE_OBJ :=$(FASTFPE)/
endif

Since arch/arm/fastfpe does not exist in the upstream tree,
I guess this is a hook to compile downstream source code.

If a user puts arch/arm/fastfpe/ into their local source tree,
Kbuild is supposed to compile the files in it.

Is this correct?

If so, I am afraid this would not work for O= building.

$(wildcard ...) checks if this directory exists in the *objtree*,
while scripts/Makefile.build needs to include
arch/arm/fastfpe/Makefile from *srctree*.

I think the correct code should be like follows:

# Do we have FASTFPE?
FASTFPE :=arch/arm/fastfpe
ifneq ($(wildcard $(srctree)/$(FASTFPE)),)
FASTFPE_OBJ :=$(FASTFPE)/
endif

Having said that, I am not sure this code is worth fixing.

This code was added around v2.5.1.9,
and the actual source code for arch/arm/fastfpe/
was never upstreamed.

In general, we do not care much about the downstream code support.

What should we do about this?
Fix and keep maintaining? Delete?

-- 
Best Regards
Masahiro Yamada