linux-kernel - Re: [RFC PATCH] kbuild: only prompt for compressors that are actually usable

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Message-ID: <adfb38d7-8ce5-3266-df5a-e38e3597d994@infradead.org>
Date:   Tue, 12 Oct 2021 12:44:58 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Vegard Nossum <vegard.nossum@...cle.com>,
        Masahiro Yamada <masahiroy@...nel.org>
Cc:     linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH] kbuild: only prompt for compressors that are actually
 usable

On 10/12/21 10:01 AM, Vegard Nossum wrote:
> If a given compression algorithm for the kernel image is not usable on
> the host system, there is no point prompting for it.
> 
> We can use the kconfig preprocessing feature to check if the command is
> available or not. I've chosen to test this using "which", which exits
> with success if the given command exists in PATH (or it is an absolute
> path), which mimics exactly how it would be found in the kernel's
> Makefiles.

Hi Vegard,

I have made a few patches that used "which", but I was always told
that the POSIX spelling of that command is "command -v", so that is
preferable.

> This uses the make variables that are set in Makefile and/or the
> command line, so you can do e.g.
> 
>    make KGZIP=pigz menuconfig
> 
> and it will test for the correct program.
> 
> I am intentionally adding these dependencies to e.g. KERNEL_LZ4, as
> opposed to HAVE_KERNEL_LZ4, since the latter are "select"-ed
> unconditionally by the architectures that use them, so they are not
> suitable for depending on anything else.
> 
> I've put RFC in the subject as maybe there are downsides to this that
> I'm not aware of.
> 
> Signed-off-by: Vegard Nossum <vegard.nossum@...cle.com>
> ---
>   init/Kconfig | 7 +++++++
>   1 file changed, 7 insertions(+)


-- 
~Randy