linux: add option to enable support for Device Tree overlays

Add an option to compile device trees in Linux with symbol generation
such that device tree overlays can be loaded on the target system

Signed-off-by: Titouan Christophe <titouan.christophe@railnova.eu>
[Arnout: remove "default n" and move setting of LINUX_MAKE_ENV to the
 place where the rest is set.]
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>

diff --git a/linux/Config.in b/linux/Config.in
index 4f6ae2e9ee58cca7c5223f00c2e9fd5ce572c136..8b04471008adfa6c5d4209fe7f4779da1a7b0eb1 100644 (file)
--- a/linux/Config.in
+++ b/linux/Config.in
@@ -394,6 +394,14 @@ config BR2_LINUX_KERNEL_CUSTOM_DTS_PATH
          You can provide a list of dts paths to copy and
          build, separated by spaces.
 
+config BR2_LINUX_KERNEL_DTB_OVERLAY_SUPPORT
+       bool "Build Device Tree with overlay support"
+       help
+         If enabled, pass the "-@" option to dtc, such that
+         symbols are generated in the compiled Device Tree.
+         Choose this option to support Device Tree overlays
+         on the target system.
+
 endif
 
 config BR2_LINUX_KERNEL_INSTALL_TARGET

diff --git a/linux/linux.mk b/linux/linux.mk
index 02def89113f06c1ced8c818c3f366543a95304d4..62068106e048a84e5d2f5c76600c9c259535acd9 100644 (file)
--- a/linux/linux.mk
+++ b/linux/linux.mk
@@ -143,6 +143,10 @@ ifeq ($(BR2_TOOLCHAIN_GCC_AT_LEAST_8),y)
 LINUX_MAKE_ENV += KCFLAGS=-Wno-attribute-alias
 endif
 
+ifeq ($(BR2_LINUX_KERNEL_DTB_OVERLAY_SUPPORT),y)
+LINUX_MAKE_ENV += DTC_FLAGS=-@
+endif
+
 # Get the real Linux version, which tells us where kernel modules are
 # going to be installed in the target filesystem.
 LINUX_VERSION_PROBED = `$(MAKE) $(LINUX_MAKE_FLAGS) -C $(LINUX_DIR) --no-print-directory -s kernelrelease 2>/dev/null`