From 6b01d40bfedb42323a1324e1b5624f192a4c91de Mon Sep 17 00:00:00 2001
From: Daniel Golle <daniel@makrotopia.org>
Date: Sun, 4 Jun 2023 15:57:25 +0100
Subject: [PATCH] image: improve uImage.FIT device tree overlay support

Instead of generating full config nodes incl. kernel, generate minimal
config nodes for device tree overlays to be applied to the main config.
In this way, multiple device tree overlays can be applied more easily.
While at it change filenames to upstream style, ie. use dtso and dtbo
suffix for device tree overlays.

Signed-off-by: Daniel Golle <daniel@makrotopia.org>
---
 include/image-commands.mk |  2 +-
 include/image.mk          | 19 ++++++++++++++++++-
 scripts/mkits.sh          |  9 +++------
 3 files changed, 22 insertions(+), 8 deletions(-)

diff --git a/include/image-commands.mk b/include/image-commands.mk
index ea602662a5..1d69485019 100644
--- a/include/image-commands.mk
+++ b/include/image-commands.mk
@@ -307,7 +307,7 @@ define Build/fit
 		$(if $(DEVICE_FDT_NUM),-n $(DEVICE_FDT_NUM)) \
 		$(if $(DEVICE_DTS_DELIMITER),-l $(DEVICE_DTS_DELIMITER)) \
 		$(if $(DEVICE_DTS_LOADADDR),-s $(DEVICE_DTS_LOADADDR)) \
-		$(if $(DEVICE_DTS_OVERLAY),$(foreach dtso,$(DEVICE_DTS_OVERLAY), -O $(dtso):$(KERNEL_BUILD_DIR)/image-$(dtso).dtb)) \
+		$(if $(DEVICE_DTS_OVERLAY),$(foreach dtso,$(DEVICE_DTS_OVERLAY), -O $(dtso):$(KERNEL_BUILD_DIR)/image-$(dtso).dtbo)) \
 		-c $(if $(DEVICE_DTS_CONFIG),$(DEVICE_DTS_CONFIG),"config-1") \
 		-A $(LINUX_KARCH) -v $(LINUX_VERSION)
 	PATH=$(LINUX_DIR)/scripts/dtc:$(PATH) mkimage $(if $(findstring external,$(word 3,$(1))),\
diff --git a/include/image.mk b/include/image.mk
index 0eae216ded..0cf110df93 100644
--- a/include/image.mk
+++ b/include/image.mk
@@ -554,16 +554,33 @@ define Device/Build/dtb
   image_prepare: $(KDIR)/image-$(1).dtb
   endif
 
+endef
+
+define Device/Build/dtbo
+  ifndef BUILD_DTS_$(1)
+  BUILD_DTS_$(1) := 1
+  $(KDIR)/image-$(1).dtbo: FORCE
+	$(call Image/BuildDTB,$(strip $(2))/$(strip $(3)).dtso,$$@)
+
+  image_prepare: $(KDIR)/image-$(1).dtbo
+  endif
+
 endef
 endif
 
 define Device/Build/kernel
-  $$(eval $$(foreach dts,$$(DEVICE_DTS) $$(DEVICE_DTS_OVERLAY), \
+  $$(eval $$(foreach dts,$$(DEVICE_DTS), \
 	$$(call Device/Build/dtb,$$(notdir $$(dts)), \
 		$$(if $$(DEVICE_DTS_DIR),$$(DEVICE_DTS_DIR),$$(DTS_DIR)), \
 		$$(dts) \
 	) \
   ))
+  $$(eval $$(foreach dtso,$$(DEVICE_DTS_OVERLAY), \
+	$$(call Device/Build/dtbo,$$(notdir $$(dtso)), \
+		$$(if $$(DEVICE_DTS_DIR),$$(DEVICE_DTS_DIR),$$(DTS_DIR)), \
+		$$(dtso) \
+	) \
+  ))
 
   $(KDIR)/$$(KERNEL_NAME):: image_prepare
   $$(_TARGET): $$(if $$(KERNEL_INSTALL),$(BIN_DIR)/$$(KERNEL_IMAGE))
diff --git a/scripts/mkits.sh b/scripts/mkits.sh
index bf75d69f09..b1c6f98867 100755
--- a/scripts/mkits.sh
+++ b/scripts/mkits.sh
@@ -191,13 +191,10 @@ OVCONFIGS=""
 "
 	OVCONFIGS="$OVCONFIGS
 
-		config-$ovname {
-			description = \"OpenWrt ${DEVICE} with $ovname\";
-			kernel = \"kernel${REFERENCE_CHAR}1\";
-			fdt = \"fdt${REFERENCE_CHAR}$FDTNUM\", \"$ovnode\";
-			${LOADABLES:+loadables = ${LOADABLES};}
+		$ovname {
+			description = \"OpenWrt ${DEVICE} overlay $ovname\";
+			fdt = \"$ovnode\";
 			${COMPATIBLE_PROP}
-			${INITRD_PROP}
 		};
 	"
 done