feat: define macros for const config from env vars

Cargo.toml

@@ -50,6 +50,8 @@ riot-wrappers = { version = "^0.8", default-features = false, features = [
 
 static_cell = { version = "2.0.0", features = [ "nightly" ] }
 ld-memory = { version = "0.2.9" }
+konst = { version = "0.3.8", default_features = false }
+const_panic = { version = "0.2.8", default_features = false }
 
 [profile.dev]
 incremental = false

src/riot-rs-embassy/Cargo.toml

@@ -18,6 +18,8 @@ embassy-time = { workspace = true, optional = true }
 embassy-usb = { workspace = true, optional = true }
 embassy-net = { workspace = true, optional = true, features = [ "dhcpv4", "medium-ethernet" ] }
 heapless = "0.8.0"
+konst = { workspace = true, features = ["parsing"] }
+const_panic = { workspace = true }
 
 [target.'cfg(context = "cortex-m")'.dependencies]
 embassy-executor = { workspace = true, features = [

src/riot-rs-embassy/src/env_utils.rs

@@ -0,0 +1,27 @@
+macro_rules! define_env_with_default_macro {
+    ($macro_name:ident, $parse_fn_name:ident, $output_type_name:literal) => {
+        #[macro_export]
+        macro_rules! $macro_name {
+            ($env_var:literal, $default:expr) => {
+                if let Some(str_value) = option_env!($env_var) {
+                    if let Ok(value) = konst::primitive::$parse_fn_name(str_value) {
+                        value
+                    } else {
+                        const_panic::concat_panic!(
+                            "Could not parse environment variable `",
+                            $env_var,
+                            "=",
+                            str_value,
+                            "` as ",
+                            $output_type_name,
+                        );
+                    }
+                } else {
+                    $default
+                }
+            };
+        }
+    };
+}
+
+define_env_with_default_macro!(usize_env_or, parse_usize, "a usize");

src/riot-rs-embassy/src/lib.rs

@@ -14,6 +14,7 @@
 #![feature(used_with_arg)]
 
 pub mod define_peripherals;
+mod env_utils;
 
 #[cfg_attr(context = "nrf52", path = "arch/nrf52.rs")]
 #[cfg_attr(context = "rp2040", path = "arch/rp2040.rs")]