build: Add an option for debug-output

Signed-off-by: Rahix <rahix@rahix.de>

Documentation/how-to-build.rst

@@ -58,6 +58,19 @@ can build with *ninja*.
 
 .. note::
 
+   If you intend to work on the firmware, you might want to enable debug output
+   in the firmware version you build.  You can do this by calling ``meson``
+   with additional arguments.  To do so, add you meson arguments to the
+   bootstrap call like this:
+
+   .. code-block:: shell-session
+
+      ./bootstrap.sh -Ddebug_prints=true
+
+   (``debug_prints`` is an option provided by our firmware)
+
+.. warning::
+
    Our build-system contains a few workarounds around short-comings in meson.
    These workarounds might break on some setups which we did not yet test.  If
    this is the case for you, please open an issue in our `issue tracker`_!

bootstrap.sh

@@ -5,7 +5,7 @@ cd "$(dirname "$0")"
 test -d build/ && rm -r build/
 
 git submodule update --init ./lib/micropython
-meson --cross-file card10-cross.ini build/
+meson --cross-file card10-cross.ini build/ "$@"
 
 set +x
 

meson.build

@@ -21,6 +21,13 @@ add_global_arguments(
   language: 'c',
 )
 
+if get_option('debug_prints')
+  add_global_arguments(
+    ['-DLOG_ENABLE_DEBUG=1'],
+    language: 'c',
+  )
+endif
+
 add_global_link_arguments(
   '-Wl,--gc-sections',
   '-lm',

meson_options.txt

+option(
+  'debug_prints',
+  type: 'boolean',
+  value: false,
+
+  description: 'Whether to print debug messages on the serial console'
+)