Re: [PATCH v5] scripts: use pkg-config to locate libcrypto

From: Masahiro Yamada <masahiroy@kernel.org>
To: Rolf Eike Beer <eb@emlix.com>
Cc: David Woodhouse <dwmw2@infradead.org>,
	Linux Kernel Developers List <linux-kernel@vger.kernel.org>,
	David Howells <dhowells@redhat.com>,
	keyrings@vger.kernel.org,
	Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>
Subject: Re: [PATCH v5] scripts: use pkg-config to locate libcrypto
Date: Wed, 27 Jan 2021 01:02:32 +0900	[thread overview]
Message-ID: <CAK7LNAT8-jpAbkjA-pvy4nM+QX9uxVpnjnjW0n+hyyqwX09=7Q@mail.gmail.com> (raw)
In-Reply-To: <2384276.IbH9z7ADXJ@devpool47>

On Tue, Jan 26, 2021 at 5:01 PM Rolf Eike Beer <eb@emlix.com> wrote:
>
> Am Dienstag, 26. Januar 2021, 07:30:03 CET schrieb Masahiro Yamada:
> > On Tue, Jan 26, 2021 at 2:42 PM Rolf Eike Beer <eb@emlix.com> wrote:
> > > Am Mittwoch, 13. Januar 2021, 13:49:12 CET schrieb Rolf Eike Beer:
> > > > Otherwise build fails if the headers are not in the default location.
> > > > While
> > > > at it also ask pkg-config for the libs, with fallback to the existing
> > > > value.
> > >
> > > Can someone please take this through the kbuild-tree? Noone seems to be
> > > interested in picking this up so far.
>
> > Is 'PKG_CONFIG' necessary?
> >
> > I see many Makefiles hard-coding 'pkg-config'.
>
> Well, it depends ;)
>
> When people use pkgconf then this usually installs a pkg-config alias, too, so
> that would be no problem. The problem comes when other places in the kernel
> start copying that code over, and then hardcode pkg-config for stuff that
> needs a prefixed pkg-config because it is about target code.
>
> Given that I would prefer it this way, but YMMV. If it is that variable that
> blocks integrating I'll change it.
>
> Eike
> --
> Rolf Eike Beer, emlix GmbH, http://www.emlix.com
> Fon +49 551 30664-0, Fax +49 551 30664-11
> Gothaer Platz 3, 37083 Göttingen, Germany
> Sitz der Gesellschaft: Göttingen, Amtsgericht Göttingen HR B 3160
> Geschäftsführung: Heike Jordan, Dr. Uwe Kracke – Ust-IdNr.: DE 205 198 055
>
> emlix - smart embedded open source

What I understood from commit a8a5cd8b472c is
the cross-compile prefix is needed
only for the target CC.

$(CC)      ->  $(CROSS_COMPILE)pkg-config  (i.e. $(PKG_CONFIG))
$(HOSTCC)  ->  pkg-config

For cross-compiling, the prefixing makes sense
because $(CC) != $(HOSTCC)

In this case, scripts/extract-cert is a host tool
compiled by $(HOSTCC), so I do not see
a good reason to use $(PKG_CONFIG).

If somebody copy-pastes the code without understanding it,
that is their problem.

Let's do proper engineering. :-)

--
Best Regards
Masahiro Yamada