add cargo features for each of the arm/ar interrupt controllers

Cargo.toml

@@ -35,6 +35,11 @@ panic = "abort"
 lto = "on"
 debug = true
 
+[features]
+hercules = []
+sitara-vim = []
+sitara-intc = []
+
 [[example]]
 name = "donate"
 path = "rust/examples/donate.rs"

rust/build.rs

@@ -31,10 +31,34 @@ static PTHREAD_ARCH: Arch = Arch {
 static ARM_ARCH: Arch = Arch {
     name: "arm",
     sources: &["arm.c", "syscall.S", "task_entry.S"],
-    flags: &["-fshort-enums"], // arm-none-eabi-gcc uses this by default, but clang/bindgen don't
+    flags: &["-fshort-enums"], // arm-none-eabi-gcc and rustc use this by default, but clang/bindgen don't
     defs: &[],
 };
 
+struct ArmArFeature<'a> {
+    name: &'a str,
+    path: &'a str,
+    arch_patterns: &'a [&'a str],
+}
+
+static ARM_AR_FEATURES: &[ArmArFeature] = &[
+    ArmArFeature {
+        name: "HERCULES",
+        path: "hercules",
+        arch_patterns: &["armebv7r", "armv7r"],
+    },
+    ArmArFeature {
+        name: "SITARA_VIM",
+        path: "sitara/vim",
+        arch_patterns: &["armv7r"],
+    },
+    ArmArFeature {
+        name: "SITARA_INTC",
+        path: "sitara/intc",
+        arch_patterns: &["armv7a"],
+    },
+];
+
 fn main() {
     let root_dir = PathBuf::from(env::var("CARGO_MANIFEST_DIR").unwrap());
     let target_arch = env::var("CARGO_CFG_TARGET_ARCH").unwrap();
@@ -78,16 +102,16 @@ fn main() {
         }
     }
 
-    // TODO: Provide a better way to specify Cortex-A/R variants.
-    if target.contains("armebv7r") {
-        // Assume a big-endian armv7r is a Hercules.
-        cc.include(arch_dir.join("ar/hercules"));
-    } else if target.contains("armv7r") {
-        // Assume a little-endian armv7r is a Sitara w/VIM.
-        cc.include(arch_dir.join("ar/sitara/vim"));
-    } else if target.contains("armv7a") {
-        // Assume a little-endian armv7a is a Sitara w/INTC.
-        cc.include(arch_dir.join("ar/sitara/intc"));
+    let mut arm_ar_feature_already_set = false;
+    for feat in ARM_AR_FEATURES {
+        if env::var(format!("CARGO_FEATURE_{}", feat.name)).is_ok() {
+            // Prevent multiple arm/ar features from being enabled.
+            assert!(!arm_ar_feature_already_set);
+            // Check that the architecture matches what the feature expects.
+            assert!(feat.arch_patterns.iter().any(|pat| target.contains(pat)));
+            cc.include(arch_dir.join("ar").join(feat.path));
+            arm_ar_feature_already_set = true;
+        }
     }
 
     cc.compile("rt");