build: uf2: Flexible UF2 offset selection.

UF2 offset configurable to be either flash base reg + offset,
or simply the flash bare reg if the offset is configured
to be ignored.

Signed-off-by: Peter Johanson <peter@peterjohanson.com>

CMakeLists.txt

@@ -1454,12 +1454,27 @@ if(CONFIG_BUILD_OUTPUT_BIN)
 endif()
 
 if(CONFIG_BUILD_OUTPUT_BIN AND CONFIG_BUILD_OUTPUT_UF2)
+  if(CONFIG_BUILD_OUTPUT_UF2_USE_FLASH_BASE)
+    set(flash_addr "${CONFIG_FLASH_BASE_ADDRESS}")
+  else()
+    set(flash_addr "${CONFIG_FLASH_LOAD_OFFSET}")
+  endif()
+
+  if(CONFIG_BUILD_OUTPUT_UF2_USE_FLASH_OFFSET)
+    # Note, the `+ 0` in formula below avoids errors in cases where a Kconfig
+    #       variable is undefined and thus expands to nothing.
+    math(EXPR flash_addr
+        "${flash_addr} + ${CONFIG_FLASH_LOAD_OFFSET} + 0"
+         OUTPUT_FORMAT HEXADECIMAL
+    )
+  endif()
+
   list(APPEND
     post_build_commands
     COMMAND ${PYTHON_EXECUTABLE} ${ZEPHYR_BASE}/scripts/uf2conv.py
             -c
             -f ${CONFIG_BUILD_OUTPUT_UF2_FAMILY_ID}
-            -b ${CONFIG_FLASH_LOAD_OFFSET}
+            -b ${flash_addr}
             -o ${KERNEL_UF2_NAME}
             ${KERNEL_BIN_NAME}
   )

Kconfig.zephyr

@@ -486,6 +486,14 @@ config BUILD_OUTPUT_UF2_FAMILY_ID
 	  name string. If the SoC in use is known by UF2, the Family ID will
 	  be pre-filled with the known value.
 
+config BUILD_OUTPUT_UF2_USE_FLASH_BASE
+	bool
+	default n
+
+config BUILD_OUTPUT_UF2_USE_FLASH_OFFSET
+	bool
+	default n
+
 endif # BUILD_OUTPUT_UF2
 
 config BUILD_OUTPUT_STRIPPED