From fb505709943fc1049aa6e135312ddd2eb663d0cd Mon Sep 17 00:00:00 2001
From: Kevin O'Connor <kevin@koconnor.net>
Date: Thu, 28 Jul 2022 10:59:55 -0400
Subject: [PATCH] buildbinary: Add support for building lpc176x checksum

The lpc176x internal rom checks that the first 8 words of the flash
sum to zero.  Many flash writing tools for the lpc176x will
automatically add the appropriate checksum.  However, it can be useful
to build the checksum locally so that the image supports direct flash
writing.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
---
 scripts/buildbinary.py | 13 ++++++++++++-
 src/lpc176x/Makefile   |  4 ++--
 src/stm32/Makefile     |  2 +-
 3 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/scripts/buildbinary.py b/scripts/buildbinary.py
index bb2f49c..6660349 100644
--- a/scripts/buildbinary.py
+++ b/scripts/buildbinary.py
@@ -4,7 +4,7 @@
 # Copyright (C) 2022  Kevin O'Connor <kevin@koconnor.net>
 #
 # This file may be distributed under the terms of the GNU GPLv3 license.
-import sys, argparse
+import sys, argparse, struct
 
 ERR_MSG = """
 The CanBoot binary is too large for the configured APPLICATION_START.
@@ -13,10 +13,18 @@ Rerun "make menuconfig" and either increase the APPLICATION_START or
 disable features to reduce the final binary size.
 """
 
+def update_lpc176x_checksum(data):
+    data28 = data[:28]
+    words = struct.unpack('<IIIIIII', data28)
+    csum = (-sum(words)) & 0xffffffff
+    return data28 + struct.pack('<I', csum) + data[32:]
+
 def main():
     parser = argparse.ArgumentParser(description="Build CanBoot binary")
     parser.add_argument("-b", "--base", help="Address of flash start")
     parser.add_argument("-s", "--start", help="Address of application start")
+    parser.add_argument("-l", "--lpc176x", action='store_true',
+                        help="Perform lpc176x checksum")
     parser.add_argument("input_file", help="Raw binary filename")
     parser.add_argument("output_file", help="Final binary filename")
     args = parser.parse_args()
@@ -34,6 +42,9 @@ def main():
         sys.stderr.write(ERR_MSG + msg)
         sys.exit(-1)
 
+    if args.lpc176x:
+        data = update_lpc176x_checksum(data)
+
     f = open(args.output_file, 'wb')
     f.write(data)
     f.close()
diff --git a/src/lpc176x/Makefile b/src/lpc176x/Makefile
index 45e9fcc..d72b54a 100644
--- a/src/lpc176x/Makefile
+++ b/src/lpc176x/Makefile
@@ -25,7 +25,7 @@ src-$(CONFIG_SERIAL) += lpc176x/serial.c generic/serial_irq.c
 # Build the additional bin output file
 target-y += $(OUT)canboot.bin
 
-$(OUT)canboot.bin: $(OUT)canboot.elf
+$(OUT)canboot.bin: $(OUT)canboot.elf ./scripts/buildbinary.py
 	@echo "  Creating hex file $@"
 	$(Q)$(OBJCOPY) -O binary $< $(OUT)canboot.work
-	$(Q)$(PYTHON) ./scripts/buildbinary.py -b $(CONFIG_FLASH_START) -s $(CONFIG_APPLICATION_START) $(OUT)canboot.work $@
+	$(Q)$(PYTHON) ./scripts/buildbinary.py -b $(CONFIG_FLASH_START) -s $(CONFIG_APPLICATION_START) -l $(OUT)canboot.work $@
diff --git a/src/stm32/Makefile b/src/stm32/Makefile
index 37dd8a5..06ad2c1 100644
--- a/src/stm32/Makefile
+++ b/src/stm32/Makefile
@@ -61,7 +61,7 @@ src-$(CONFIG_CANSERIAL) += $(canbus-src-y) generic/canbus.c stm32/chipid.c
 # Binary output file rules
 target-y += $(OUT)canboot.bin
 
-$(OUT)canboot.bin: $(OUT)canboot.elf
+$(OUT)canboot.bin: $(OUT)canboot.elf ./scripts/buildbinary.py
 	@echo "  Creating hex file $@"
 	$(Q)$(OBJCOPY) -O binary $< $(OUT)canboot.work
 	$(Q)$(PYTHON) ./scripts/buildbinary.py -b $(CONFIG_FLASH_START) -s $(CONFIG_APPLICATION_START) $(OUT)canboot.work $@