[PATCH v5 06/12] cross-compilation: Introduce variable switch

[Alexander Smirnov <asmirnov@ilbers.de>]

Add variable to switch from native to cross compilation.

Signed-off-by: Alexander Smirnov <asmirnov@ilbers.de>
---
 meta-isar/conf/local.conf.sample                      |  5 +++++
 .../recipes-kernel/example-module/example-module.bb   |  7 +++++++
 meta/classes/dpkg-base.bbclass                        | 19 ++++++++++++++++---
 meta/classes/dpkg-raw.bbclass                         |  1 -
 meta/classes/dpkg.bbclass                             |  4 +---
 5 files changed, 29 insertions(+), 7 deletions(-)

diff --git a/meta-isar/conf/local.conf.sample b/meta-isar/conf/local.conf.sample
index 16ef488..27b43d1 100644
--- a/meta-isar/conf/local.conf.sample
+++ b/meta-isar/conf/local.conf.sample
@@ -156,3 +156,8 @@ CONF_VERSION = "1"
 #
 # The default list of extra packages to be installed.
 IMAGE_INSTALL = "example-hello example-raw example-module"
+
+#
+# Enable cross-compilation support
+# NOTE: this works only for stretch-armhf and stretch-amd64 targets for now.
+ISAR_CROSS_COMPILE ?= "0"
diff --git a/meta-isar/recipes-kernel/example-module/example-module.bb b/meta-isar/recipes-kernel/example-module/example-module.bb
index 98d0aaa..6b63ae3 100644
--- a/meta-isar/recipes-kernel/example-module/example-module.bb
+++ b/meta-isar/recipes-kernel/example-module/example-module.bb
@@ -12,3 +12,10 @@ SRC_URI += "file://src"
 S = "${WORKDIR}/src"
 
 AUTOLOAD = "1"
+
+# Cross-compilation is not supported for the default Debian kernels.
+# For example, package with kernel headers for ARM:
+#   linux-headers-armmp
+# has hard dependencies from linux-compiler-gcc-4.8-arm, what
+# conflicts with the host binaries.
+ISAR_CROSS_COMPILE = "0"
diff --git a/meta/classes/dpkg-base.bbclass b/meta/classes/dpkg-base.bbclass
index 3234234..674c0b5 100644
--- a/meta/classes/dpkg-base.bbclass
+++ b/meta/classes/dpkg-base.bbclass
@@ -1,6 +1,22 @@
 # This software is a part of ISAR.
 # Copyright (C) 2017 Siemens AG
 
+ISAR_CROSS_COMPILE ??= "0"
+
+# Add dependency from the correct buildchroot: host or target
+python __anonymous() {
+    mode = d.getVar('ISAR_CROSS_COMPILE', True)
+    if mode == "0":
+        dep = "buildchroot-target:do_build"
+        rootfs = d.getVar('BUILDCHROOT_TARGET_DIR', True)
+    else:
+        dep = "buildchroot-host:do_build"
+        rootfs = d.getVar('BUILDCHROOT_HOST_DIR', True)
+
+    d.setVarFlag('do_build', 'depends', dep)
+    d.setVar('BUILDCHROOT_DIR', rootfs)
+}
+
 do_adjust_git() {
     if [ -f ${S}/.git/objects/info/alternates ]; then
         sed -i ${S}/.git/objects/info/alternates \
@@ -14,9 +30,6 @@ do_adjust_git[stamp-extra-info] = "${DISTRO}-${DISTRO_ARCH}"
 inherit patch
 addtask patch after do_adjust_git before do_build
 
-# Add dependency from buildchroot creation
-do_build[depends] = "buildchroot-target:do_build"
-
 # Add dependency between Isar recipes
 DEPENDS ?= ""
 do_build[deptask] = "do_deploy_deb"
diff --git a/meta/classes/dpkg-raw.bbclass b/meta/classes/dpkg-raw.bbclass
index 2f23eb7..28233ac 100644
--- a/meta/classes/dpkg-raw.bbclass
+++ b/meta/classes/dpkg-raw.bbclass
@@ -7,7 +7,6 @@ DEBIAN_DEPENDS ?= ""
 MAINTAINER ?= "FIXME Unknown maintainer"
 
 D = "${WORKDIR}/image/"
-BUILDCHROOT_DIR = "${BUILDCHROOT_TARGET_DIR}"
 
 # Populate folder that will be picked up as package
 do_install() {
diff --git a/meta/classes/dpkg.bbclass b/meta/classes/dpkg.bbclass
index 563b63c..ab70645 100644
--- a/meta/classes/dpkg.bbclass
+++ b/meta/classes/dpkg.bbclass
@@ -3,10 +3,8 @@
 
 inherit dpkg-base
 
-BUILDCHROOT_DIR = "${BUILDCHROOT_TARGET_DIR}"
-
 # Build package from sources using build script
 dpkg_runbuild() {
     E="${@ bb.utils.export_proxies(d)}"
-    sudo -E chroot ${BUILDCHROOT_DIR} /build.sh ${PP}/${PPS}
+    sudo -E chroot ${BUILDCHROOT_DIR} /build.sh ${PP}/${PPS} ${DISTRO_ARCH}
 }
-- 
2.11.0