Re: [dpdk-dev] [RFC PATCH v1] build: kni gcc cross-compilation support

The kni linux module is using a custom target for building, which
doesn't take into account any cross compilation arguments. The arguments
in question are ARCH and CROSS_COMPILE. Get those from the cross file
and pass them to the custom target.

The user supplied path may not contain the 'build' directory, such as
when using cross-compiled headers, so only append that in the default
case (when no path is supplied in native builds) and use the unmodified
path from the user otherwise.

Signed-off-by: Juraj Linkeš <redacted>
---
 kernel/linux/kni/meson.build |  4 ++--
 kernel/linux/meson.build     | 33 +++++++++++++++++++++++++++++----
 2 files changed, 31 insertions(+), 6 deletions(-)

diff --git a/kernel/linux/kni/meson.build b/kernel/linux/kni/meson.build
index 07e0c9dae..0fbf52c93 100644
--- a/kernel/linux/kni/meson.build
+++ b/kernel/linux/kni/meson.build

@@ -13,7 +13,7 @@ kni_sources = files(
 custom_target('rte_kni',
 	input: kni_sources,
 	output: 'rte_kni.ko',
-	command: ['make', '-j4', '-C', kernel_dir + '/build',
+	command: ['make', '-j4', '-C', kernel_dir,
 		'M=' + meson.current_build_dir(),
 		'src=' + meson.current_source_dir(),
 		'MODULE_CFLAGS=-include ' + meson.source_root() + '/config/rte_config.h' +

@@ -21,7 +21,7 @@ custom_target('rte_kni',
 		' -I' + meson.source_root() + '/lib/librte_kni' +
 		' -I' + meson.build_root() +
 		' -I' + meson.current_source_dir(),
-		'modules'],
+		'modules'] + cross_args,
 	depends: kni_mkfile,
 	install: true,
 	install_dir: kernel_dir + '/extra/dpdk',

diff --git a/kernel/linux/meson.build b/kernel/linux/meson.build
index 5c864a465..57ed9bc48 100644
--- a/kernel/linux/meson.build
+++ b/kernel/linux/meson.build

@@ -3,20 +3,45 @@
 
 subdirs = ['kni']
 
+cross_args = []
 # if we are cross-compiling we need kernel_dir specified
-if get_option('kernel_dir') == '' and meson.is_cross_build()
-	error('Need "kernel_dir" option for kmod compilation when cross-compiling')
+if meson.is_cross_build()
+	if get_option('kernel_dir') == ''
+		error('Need "kernel_dir" option for kmod compilation when cross-compiling')
+	else
+		cross_compiler = find_program('c').path()
+		if cross_compiler.endswith('gcc')
+			cross_prefix = ''
+			# remove the 'gcc' suffix
+			# meson doesn't support removing elements from an array
+			# nor does it support slicing, so do it on our own
+			foreach element : cross_compiler.split('-')
+				if element != 'gcc'
+					cross_prefix += '@0@-'.format(element)
+				endif
+			endforeach
+		else
+			error('Unsupported cross compiler: @0@'.format(cross_compiler))
+		endif