[openwrt/openwrt] image: add recipe for legacy multiple images

[LEDE Commits]

robimarko pushed a commit to openwrt/openwrt.git, branch main:
https://git.openwrt.org/905338ad609467e1117635a49c5f0c002f9ae237

commit 905338ad609467e1117635a49c5f0c002f9ae237
Author: Robert Marko <robimarko at gmail.com>
AuthorDate: Wed Jun 26 18:52:29 2024 +0200

    image: add recipe for legacy multiple images
    
    Asus RT-AX89X has modded U-Boot that boots FIT images fine when manually
    using bootm command, however once the image is flashed and device boots via
    the default bootcmd it only supports booting via legacy images.
    
    More precisely, it requires the "multi" image format with:
    1. kernel
    2. ramdisk
    3. DTB
    
    So, lets add a recipe based on the existing uImage one.
    
    Link: https://github.com/openwrt/openwrt/pull/15840
    Signed-off-by: Robert Marko <robimarko at gmail.com>
---
 include/image-commands.mk | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/include/image-commands.mk b/include/image-commands.mk
index 04213a3be8..cb899a2f30 100644
--- a/include/image-commands.mk
+++ b/include/image-commands.mk
@@ -701,6 +701,23 @@ define Build/uImage
 	mv $@.new $@
 endef
 
+define Build/multiImage
+	$(if $(UIMAGE_TIME),SOURCE_DATE_EPOCH="$(UIMAGE_TIME)") \
+	mkimage \
+		-A $(LINUX_KARCH) \
+		-O linux \
+		-T multi \
+		-C $(word 1,$(1)) \
+		-a $(KERNEL_LOADADDR) \
+		-e $(if $(KERNEL_ENTRY),$(KERNEL_ENTRY),$(KERNEL_LOADADDR)) \
+		-n '$(if $(UIMAGE_NAME),$(UIMAGE_NAME),$(call toupper,$(LINUX_KARCH)) $(VERSION_DIST) Linux-$(LINUX_VERSION))' \
+		$(if $(UIMAGE_MAGIC),-M $(UIMAGE_MAGIC)) \
+		-d $@:$(word 2,$(1)):$(word 3,$(1)) \
+		$(wordlist 4,$(words $(1)),$(1)) \
+		$@.new
+	mv $@.new $@
+endef
+
 define Build/xor-image
 	$(STAGING_DIR_HOST)/bin/xorimage -i $@ -o $@.xor $(1)
 	mv $@.xor $@