Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
From:   Toke =?utf-8?Q?H=C3=B8iland-J=C3=B8rgensen?= <toke@redhat.com>
To:     Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc:     Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Martin KaFai Lau <kafai@fb.com>,
        Song Liu <songliubraving@fb.com>, Yonghong Song <yhs@fb.com>,
        Andrii Nakryiko <andriin@fb.com>,
        Doug Ledford <dledford@redhat.com>,
        Jason Gunthorpe <jgg@ziepe.ca>,
        "David S. Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        Jesper Dangaard Brouer <brouer@redhat.com>,
        John Fastabend <john.fastabend@gmail.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Jiri Olsa <jolsa@redhat.com>,
        Namhyung Kim <namhyung@kernel.org>,
        Shuah Khan <shuah@kernel.org>,
        Networking <netdev@vger.kernel.org>, bpf <bpf@vger.kernel.org>,
        open list <linux-kernel@vger.kernel.org>,
        linux-rdma@vger.kernel.org,
        "open list\:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@vger.kernel.org>,
        clang-built-linux@googlegroups.com
Subject: Re: [PATCH bpf-next v4 09/10] selftests: Remove tools/lib/bpf from include path
In-Reply-To: <CAEf4Bzb9zUmhxTyYahJqySJzgfyB-zMEd+o4ybv=a8-t+iZS4w@mail.gmail.com>
References: <157926819690.1555735.10756593211671752826.stgit@toke.dk> <157926820677.1555735.5437255599683298212.stgit@toke.dk> <CAEf4Bzb9zUmhxTyYahJqySJzgfyB-zMEd+o4ybv=a8-t+iZS4w@mail.gmail.com>
Date:   Mon, 20 Jan 2020 12:06:44 +0100
Message-ID: <878sm2pet7.fsf@toke.dk>
MIME-Version: 1.0
Content-Type: text/plain
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

[...]
> I really-really didn't like this alternating dependency on directory
> or a set of file, depending on current state of those temporary
> directories. Then also this ugly check to avoid circular dependency.
> All that seemed wrong. So I played a bit with how to achieve the same
> differently, and here's what I came up with, which I like a bit
> better. What do you think?
>
> $(BPFOBJ): $(wildcard $(BPFDIR)/*.c $(BPFDIR)/*.h $(BPFDIR)/Makefile)          \
>            ../../../include/uapi/linux/bpf.h                                   \
>            | $(INCLUDE_DIR) $(BUILD_DIR)/libbpf
>         $(Q)$(MAKE) $(submake_extras) -C $(BPFDIR) OUTPUT=$(BUILD_DIR)/libbpf/ \
>                     DESTDIR=$(SCRATCH_DIR) prefix= all install_headers
>
> So, essentially, just make sure that we install local copies of
> headers whenever libbpf.a needs to be re-built.
> ../../../include/uapi/linux/bpf.h ensures we don't miss uapi header
> changes as well. Now anything that uses libbpf headers will need to
> depend on $(BPFOBJ) and will automatically get up-to-date local copies
> of headers.
>
> This seems much simpler. Please give it a try, thanks!

Yes, this is a good idea! It did actually occur to me that the $(BPFOBJ)
rule could just include the install_headers make arg, but only after I
sent out this latest version. Thank you for taking the time to work out
the details, I'll fold this in :)

-Toke