Re: [PATCH] ARC: build: Try to guess CROSS_COMPILE with cc-cross-prefix

[Vineet Gupta]

On 6/2/19 11:31 PM, Alexey Brodkin wrote:
> For a long time we used to hard-code CROSS_COMPILE prefix
> for ARC until it started to cause problems, so we decided to
> solely rely on CROSS_COMPILE externally set by a user:
> commit 40660f1fcee8 ("ARC: build: Don't set CROSS_COMPILE in arch's Makefile").
>
> While it works perfectly fine for build-systems where the prefix
> gets defined anyways for us human beings it's quite an annoying
> requirement especially given most of time the same one prefix
> "arc-linux-" is all what we need.
>
> It looks like finally we're getting the best of both worlds:
>  1. W/o cross-toolchain we still may install headers, build .dtb etc
>  2. W/ cross-toolchain get the kerne built with only ARCH=arc
>
> Inspired by [1] & [2].
>
> [1] http://lists.infradead.org/pipermail/linux-snps-arc/2019-May/005788.html
> [2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=fc2b47b55f17
>
> A side note: even though "cc-cross-prefix" does its job it pollutes
> console with output of "which" for all the prefixes it didn't manage to find
> a matching cross-compiler for like that:
> | # ARCH=arc make defconfig
> | which: no arceb-linux-gcc in (~/.local/bin:~/bin:/usr/bin:/usr/sbin)
> | *** Default configuration is based on 'nsim_hs_defconfig'
>
> Signed-off-by: Alexey Brodkin <abrodkin@xxxxxxxxxxxx>
> Cc: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx>
> Cc: Vineet Gupta <vgupta@xxxxxxxxxxxx>

Not a big deal but I'd propose we add "Suggested-by: vgupta" since that is where
it came from.

@Masahiro san I suppose you are OK with this, so perhaps an Ack etc would be nice
to have.

Thx,
-Vineet

> ---
>  arch/arc/Makefile | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/arch/arc/Makefile b/arch/arc/Makefile
> index e2b991f75bc5..9cfd2ba7a12d 100644
> --- a/arch/arc/Makefile
> +++ b/arch/arc/Makefile
> @@ -8,6 +8,10 @@
>  
>  KBUILD_DEFCONFIG := nsim_hs_defconfig
>  
> +ifeq ($(CROSS_COMPILE),)
> +CROSS_COMPILE := $(call cc-cross-prefix, arc-linux- arceb-linux-)
> +endif
> +
>  cflags-y	+= -fno-common -pipe -fno-builtin -mmedium-calls -D__linux__
>  cflags-$(CONFIG_ISA_ARCOMPACT)	+= -mA7
>  cflags-$(CONFIG_ISA_ARCV2)	+= -mcpu=hs38