Replacing boot logos on Anbernic RG DS stock Linux

rgds-bootlogos.txt

on device
	
	dd if=/dev/block/by-name/boot of=/tmp/boot.img

then download boot.img locally and run

	dtc -I dtb -O dts boot.img > boot.dts
	
prep
	
	mkdir bootwork
	cd bootwork
	cp ../boot.img .

confirm partition numbers
	
	dumpimage -l boot.img 

but should be	
	
	dumpimage -T flat_dt -p 2 -o resource.img boot.img

if necessary

	apt update
	apt install golang
	git clone https://github.com/Evsio0n/rsce-go
	cd rsce-go
	go mod download
	go mod tidy
	go build -o rsce_tool
	cp rsce_tool /usr/local/bin/

extract
	mkdir resource
	cd resource
	rsce_tool -u ../resource.img

modify bitmaps

	logo.bmp - top screen
	logo_kernel.bmp - bottom

repack modified bitmaps into resource-mod.img

	rsce_tool \
	  -p rk-kernel.dtb \
	  -p battery_1.bmp \
	  -p battery_2.bmp \
	  -p battery_3.bmp \
	  -p battery_4.bmp \
	  -p battery_5.bmp \
	  -p battery_fail.bmp \
	  -p logo.bmp \
	  -p logo_kernel.bmp \
	  -p battery_0.bmp
	mv boot-second ../resource-mod.img
	cd ../

pad to original size
	
	ORIGINAL_SIZE=$(wc -c < resource.img)
	cp resource-mod.img resource-pad.img
	truncate -s $ORIGINAL_SIZE resource-pad.img

patch original boot.img (note that the seek offset comes from data-position in boot.dts)

	cp boot.img boot-mod.img
	dd if=resource-pad.img of=boot-mod.img bs=512 seek=$((0x2580800 / 512)) conv=notrunc

then update the hash
	
	OLD_HASH=$(sha256sum resource.img | cut -d' ' -f1)
	NEW_HASH=$(sha256sum resource-pad.img | cut -d' ' -f1)
	OFFSET=$(xxd -p boot-mod.img | tr -d '\n' | grep -abo "$OLD_HASH" | cut -d: -f1)
	printf '%s' "$NEW_HASH" | xxd -r -p | dd of=boot-mod.img bs=1 seek=$((OFFSET / 2)) conv=notrunc

--

write back

	dd if=/tmp/boot-mod.img of=/dev/block/by-name/boot