[PATCH v2] linux-module: Simplify interface to module makefiles

[Jan Kiszka <jan.kiszka@siemens.com>]

From: Jan Kiszka <jan.kiszka@siemens.com>

Not all module makefile respect DESTDIR nor even have build targets
which take KDIR as input. So call the kernel makefile ourselves, just
requiring the module makefile to provide Kbuild rules.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
---

Changes in v2:
 - update RECIPE-API-CHANGELOG

 RECIPE-API-CHANGELOG.md                             | 5 +++++
 meta/recipes-kernel/linux-module/files/debian/rules | 6 ++++++
 meta/recipes-kernel/linux-module/module.inc         | 1 +
 3 files changed, 12 insertions(+)

diff --git a/RECIPE-API-CHANGELOG.md b/RECIPE-API-CHANGELOG.md
index 06a01e3..832f0ed 100644
--- a/RECIPE-API-CHANGELOG.md
+++ b/RECIPE-API-CHANGELOG.md
@@ -124,3 +124,8 @@ updated hence recipes using them shouldn't be impacted per se.
 
 These packages depend on a specific kernel. Its identification is now appended
 to the binary package names in the form "-${KERNEL_NAME}".
+
+### Reduce requirements on custom module makefiles
+
+It's now sufficient to provide only kbuild rules. Makefile targets like modules
+or modules_install as well as KDIR and DESTDIR evaluation are no longer needed.
diff --git a/meta/recipes-kernel/linux-module/files/debian/rules b/meta/recipes-kernel/linux-module/files/debian/rules
index 5c1d8be..7a89e41 100755
--- a/meta/recipes-kernel/linux-module/files/debian/rules
+++ b/meta/recipes-kernel/linux-module/files/debian/rules
@@ -21,5 +21,11 @@ ifneq (,$(findstring 86,$(DEB_HOST_GNU_CPU)))
 export ARCH=x86
 endif
 
+override_dh_auto_build:
+	$(MAKE) -C $(KDIR) M=$(PWD) modules
+
+override_dh_auto_install:
+	$(MAKE) -C $(KDIR) M=$(PWD) INSTALL_MOD_PATH=$(PWD)/debian/$(PN) modules_install
+
 %:
 	CFLAGS= LDFLAGS= dh $@ --parallel
diff --git a/meta/recipes-kernel/linux-module/module.inc b/meta/recipes-kernel/linux-module/module.inc
index 5d85200..cb7b8ad 100644
--- a/meta/recipes-kernel/linux-module/module.inc
+++ b/meta/recipes-kernel/linux-module/module.inc
@@ -43,4 +43,5 @@ dpkg_runbuild_prepend() {
         export KDIR=$(dpkg -L --root=${BUILDCHROOT_DIR} ${KERNEL_DEP} | \
                       grep "/lib/modules/.*/build")
     fi
+    export PN=${PN}
 }
-- 
2.16.4