-----Original Message-----
From: Bruce Richardson <redacted>
Sent: Friday, January 29, 2021 10:46 AM
To: Juraj Linkeš <redacted>
Cc: Andrew Boyer <redacted>; Honnappa Nagarahalli
[off-list ref]; thomas@monjalon.net; Ruifeng Wang
[off-list ref]; Phil Yang [off-list ref];
vcchunga@amazon.com; Dharmik Thakkar [off-list ref];
jerinjacobk@gmail.com; hemant.agrawal@nxp.com; Ajit Khaparde
(ajit.khaparde@broadcom.com) [off-list ref];
ferruh.yigit@intel.com; dev@dpdk.org; nd [off-list ref]
Subject: Re: [dpdk-dev] [PATCH v14 00/12] Arm build options rework

On Fri, Jan 29, 2021 at 08:41:45AM +0000, Juraj Linkeš wrote:

quoted

quoted

quoted

3) We need to build kni against the aarch64 kernel headers, but it
fails. It appears that kernel/linux/kni/meson.build doesn’t pass
any cross-compile flags in the make command it creates. The diff
below shows how I hardcoded it to get it to work for now. Thoughts
on how to do this right? meson has the path (in $PATH) and the
binary prefixs (in ‘[binaries]’ in the cross file). It must know
the arch, too.

--- a/kernel/linux/kni/meson.build +++

b/kernel/linux/kni/meson.build @@ -14,6 +14,8 @@
custom_target('rte_kni', input: kni_sources,
output: 'rte_kni.ko', command: ['make', '-j4', '-C', kernel_dir +
'/build', + +
'CROSS_COMPILE=/tool/toolchain/aarch64-1.1/bin/aarch64-linux-
gnu-',
+               'ARCH=aarch64', 'M=' + meson.current_build_dir(),
'src=' + meson.current_source_dir(), 'MODULE_CFLAGS=-include ' +
meson.source_root() + '/config/rte_config.h' +

Yes, Meson should know these. I'll submit this separately (in a new
series), as this series is getting pretty big and this fix is
actually unrelated.

I tried to figure out how to implement this and I've ran into a brick
wall - there's no way to figure out the full name of the cross-compiler.
I found only one way to get the cross compiler:
meson.get_compiler('c',
native:false).get_id()

But that only retuns 'gcc', not the full binary name (c =
'aarch64-linux-gnu-gcc' in cross file).

Bruce, any ideas on how to get the full name? If I understand the
sources right, we aren't able to access arbitrary object attributes,
just those, which are specifically exposed.

Maybe we could do a workaround? Either if cross compiling and the
compiler is gcc, use the 'aarch64-linux-gnu-' prefix or just put the
prefix into the cross file as an additional property?

According to the cross-file/native-file documentation[1], the files in the binaries
section can be queried using the "find_program()" call. That then returns an
external program object rather than a compiler one, so the full path can be got.
Unfortunately, find_program('c') doesn't seem to work for the non-cross-
compiled case, so it will need to be conditional on cross-compilation.

Thanks, this is great, I'll use this.
We don't need it for native builds. But it's strange that it doesn't work for those - the docs say it does.

Example I tested:

<code change added>
+myc = find_program('c')
+message('find_program(\'c\') = ' + myc.full_path())
+

<output when run>
~/dpdk.org/__BUILDS/build-arm64-host-clang$ ninja [0/1] Regenerating build
files.
....
Target machine cpu family: aarch64
Target machine cpu: armv8-a
Program aarch64-linux-gnu-gcc found: YES
WARNING: Project targeting '>= 0.47.1' but tried to use feature introduced in
'0.55.0': ExternalProgram.full_path.
Message: find_program('c') = /home/bruce/Downloads/gcc-arm-8.3-2019.03-
x86_64-aarch64-linux-gnu/bin/aarch64-linux-gnu-gcc
...

/Bruce


[1] https://mesonbuild.com/Machine-files.html#binaries