kbuild: deb-pkg: improve the usability of source package

Improve the source package support in case the dpkg-buildpackage is
directly used to build binary packages.

For cross-compiling, you can set CROSS_COMPILE via the environment
variable, but it is better to set it automatically - set it to
${DEB_HOST_GNU_TYPE}- if we are cross-compiling but not from the top
Makefile.

The generated source package may be carried to a different build
environment, which may have a different compiler installed.
Run olddefconfig first to set new CONFIG options to their default
values without prompting.

Take KERNELRELEASE and KBUILD_BUILD_VERSION from the version field of
debian/changelog in case it is updated afterwards.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

1 files changed, 16 insertions, 0 deletions

diff --git a/scripts/package/deb-build-option b/scripts/package/deb-build-option
new file mode 100755
index 000000000000..b079b0d121d4
--- /dev/null
+++ b/scripts/package/deb-build-option
@@ -0,0 +1,16 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0-only
+
+# Set up CROSS_COMPILE if we are cross-compiling, but not called from the
+# kernel toplevel Makefile
+if [ -z "${CROSS_COMPILE}${cross_compiling}" -a "${DEB_HOST_ARCH}" != "${DEB_BUILD_ARCH}" ]; then
+	echo CROSS_COMPILE=${DEB_HOST_GNU_TYPE}-
+fi
+
+version=$(dpkg-parsechangelog -S Version)
+version_upstream="${version%-*}"
+debian_revision="${version#${version_upstream}}"
+debian_revision="${debian_revision#*-}"
+
+echo KERNELRELEASE=${version_upstream}
+echo KBUILD_BUILD_VERSION=${debian_revision}