From 1f1d7082a59755d5ba1d28619d4dcf078f902762 Mon Sep 17 00:00:00 2001
From: Benjamin Valentin <benpicco@beuth-hochschule.de>
Date: Mon, 24 Apr 2023 14:14:56 +0200
Subject: [PATCH] sys/slot_aux: add build system integration for AUX slot

---
 sys/Makefile.include          |  3 +++
 sys/riotboot/Makefile.include |  2 +-
 sys/slot_aux/Makefile.include | 15 +++++++++++++++
 3 files changed, 19 insertions(+), 1 deletion(-)
 create mode 100644 sys/slot_aux/Makefile.include

diff --git a/sys/Makefile.include b/sys/Makefile.include
index 9464ca2df7..617f62fce9 100644
--- a/sys/Makefile.include
+++ b/sys/Makefile.include
@@ -110,6 +110,9 @@ ifneq (,$(filter scanf_float,$(USEMODULE)))
   endif
 endif
 
+# we need to include this before the riotboot include
+include $(RIOTBASE)/sys/slot_aux/Makefile.include
+
 ifneq (,$(filter riotboot,$(FEATURES_USED)))
   include $(RIOTBASE)/sys/riotboot/Makefile.include
 endif
diff --git a/sys/riotboot/Makefile.include b/sys/riotboot/Makefile.include
index b81e69716b..d0182d3812 100644
--- a/sys/riotboot/Makefile.include
+++ b/sys/riotboot/Makefile.include
@@ -9,7 +9,7 @@ RIOTBOOT_HDR_LEN ?= 0x100
 NUM_SLOTS ?= 2
 
 # Take the whole flash minus RIOTBOOT_LEN and divide it by NUM_SLOTS
-SLOT0_LEN ?= $(shell printf "0x%x" $$((($(ROM_LEN:%K=%*1024)-$(RIOTBOOT_LEN)) / $(NUM_SLOTS))))
+SLOT0_LEN ?= $(shell printf "0x%x" $$((($(ROM_LEN:%K=%*1024)-$(RIOTBOOT_LEN)-$(SLOT_AUX_LEN)) / $(NUM_SLOTS))))
 SLOT1_LEN ?= $(SLOT0_LEN)
 SLOT0_LEN := $(SLOT0_LEN)
 SLOT1_LEN := $(SLOT1_LEN)
diff --git a/sys/slot_aux/Makefile.include b/sys/slot_aux/Makefile.include
new file mode 100644
index 0000000000..729d0d0c2d
--- /dev/null
+++ b/sys/slot_aux/Makefile.include
@@ -0,0 +1,15 @@
+# This adds an optional AUX slot to flash that can be used to store persistent data.
+# It will work with and without riotboot, but the size of the slot must remain fixed across
+# firmware versions.
+
+# Size of the AUX slot in Bytes - must align with flash page size
+SLOT_AUX_LEN ?= 0
+SLOT_AUX_OFFSET ?= $(shell echo $$(($(ROM_LEN:%K=%*1024)-$(SLOT_AUX_LEN))))
+
+LINKFLAGS += $(LINKFLAGPREFIX)--defsym=_slot_aux_offset=$(SLOT_AUX_OFFSET)
+LINKFLAGS += $(LINKFLAGPREFIX)--defsym=_slot_aux_len=$(SLOT_AUX_LEN)
+
+ifneq (0, $(SLOT_AUX_LEN))
+  CFLAGS += -DCONFIG_SLOT_AUX_OFFSET=$(SLOT_AUX_OFFSET)
+  CFLAGS += -DCONFIG_SLOT_AUX_LEN=$(SLOT_AUX_LEN)
+endif