build firmware with Nix

derivations.nix

@@ -17,4 +17,6 @@ rec {
 
   binutils-riscv = pkgs.callPackage ./compilers/binutils.nix { platform = "riscv32"; };
   rust-riscv32imc-crates = pkgs.callPackage ./compilers/rust-riscv32imc-crates.nix { };
+
+  helloworld = pkgs.callPackage ./firmware { inherit rust-riscv32imc-crates binutils-riscv; };
 }

firmware/.cargo/config

@@ -1,2 +0,0 @@
-[build]
-target = "riscv32imc-unknown-none-elf"

firmware/default.nix

@@ -0,0 +1,21 @@
+{ rustPlatform, rust-riscv32imc-crates, binutils-riscv }:
+
+rustPlatform.buildRustPackage rec {
+  name = "helloworld";
+  version = "0.0.0";
+
+  src = ./.;
+  cargoSha256 = "1j8ipk7mwf6jqjnddpvkdydhgl7lfddxkv6p1vhzlfhqlf8am42j";
+
+  buildPhase = ''
+    export CARGO_HOME=$(mktemp -d cargo-home.XXX)
+    export RUSTFLAGS="-L ${rust-riscv32imc-crates}/lib/rustlib/riscv32imc-unknown-none-elf/lib -C linker=${binutils-riscv}/bin/riscv32-unknown-elf-ld -C link-arg=-Tlink.x"
+    cargo build --release --target riscv32imc-unknown-none-elf
+  '';
+
+  doCheck = false;
+  installPhase = ''
+    mkdir -p $out
+    cp target/riscv32imc-unknown-none-elf/release/helloworld $out
+  '';
+}

shell-firmware.nix

@@ -1,9 +0,0 @@
-{ }:
-let
-  pkgs = import <nixpkgs> { overlays = [ import ./overlay.nix ]; };
-  hx = import ./derivations.nix { inherit pkgs; };
-in
-  pkgs.mkShell {
-    buildInputs = [ hx.rustc hx.rust-riscv32imc-crates hx.binutils-riscv hx.cargo ];
-    RUSTFLAGS="-L ${hx.rust-riscv32imc-crates}/lib/rustlib/riscv32imc-unknown-none-elf/lib -C linker=riscv32-unknown-elf-ld -C link-arg=-Tlink.x";
-  }