Adds alsa config for loopback recording.

.gitignore

@@ -1,3 +1,3 @@
 result
-sd-card.img
-clementine.qcow2
+*.img
+*.qcow2

asound.conf

@@ -0,0 +1,43 @@
+pcm.multi {
+	type route;
+	slave.pcm {
+		type multi;
+		slaves.a.pcm "output";
+		slaves.b.pcm "loopin";
+		slaves.a.channels 2;
+		slaves.b.channels 2;
+		bindings.0.slave a;
+		bindings.0.channel 0;
+		bindings.1.slave a;
+		bindings.1.channel 1;
+		bindings.2.slave b;
+		bindings.2.channel 0;
+		bindings.3.slave b;
+		bindings.3.channel 1;
+	}
+
+	ttable.0.0 1;
+	ttable.1.1 1;
+	ttable.0.2 1;
+	ttable.1.3 1;
+}
+
+pcm.!default {
+	type plug
+	slave.pcm "multi"
+}
+
+pcm.output {
+	type hw
+	card 0
+}
+
+pcm.loopin {
+	type plug
+	slave.pcm "hw:Loopback,0,0"
+}
+
+pcm.loopout {
+	type plug
+	slave.pcm "hw:Loopback,1,0"
+}

citrus.nix

@@ -2,6 +2,11 @@
 {
   system.stateVersion = "23.05";
 
+  boot.kernelModules = [ "snd-aloop" ];
+  boot.extraModprobeConfig = ''
+    options snd-aloop index=8
+  '';
+
   # Enables flakes and the updated `nix` command
   nix.settings.experimental-features = [ "nix-command" "flakes" ];
 
@@ -9,6 +14,7 @@
   hardware.opengl.enable = true;
 
   sound.enable = true;
+  sound.extraConfig = (builtins.readFile ./asound.conf);
 
   # Includes packages needed for startx
   services.xserver = {

platforms/melodypond.nix

@@ -9,8 +9,11 @@
   hardware.raspberry-pi."4" = {
     fkms-3d.enable = true;
     apply-overlays-dtmerge.enable = true;
+    audio.enable = false;
   };
 
+  boot.blacklistedKernelModules = [ "snd_bcm2835" ];
+
   console.enable = false;
   environment.systemPackages = with pkgs; [
     libraspberrypi