pinwheel: Give the webcam v4l2loopback device more buffers

hosts/pinwheel/modules/webcam/default.nix

@@ -1,4 +1,4 @@
-{ ... }:
+{ config, lib, ... }:
 {
   nixpkgs.overlays = [
     (final: prev: {
@@ -11,7 +11,8 @@
       });
 
       gst_all_1 = prev.gst_all_1 // {
-        icamerasrc-ipu6epmtl = (prev.gst_all_1.icamerasrc-ipu6epmtl.override {
+        icamerasrc-ipu6epmtl =
+          (prev.gst_all_1.icamerasrc-ipu6epmtl.override {
             ipu6-camera-hal = final.ipu6epmtl-camera-hal;
           }).overrideAttrs
             (old: {
@@ -31,4 +32,14 @@
     enable = true;
     platform = "ipu6epmtl";
   };
+
+  systemd.services.v4l2-relayd-ipu6 = {
+    preStart = lib.mkOverride 40 ''
+      mkdir -p "$(dirname "$V4L2_DEVICE_FILE")"
+      ${config.boot.kernelPackages.v4l2loopback.bin}/bin/v4l2loopback-ctl \
+        add --name "Intel MIPI Camera" --exclusive-caps=1 --buffers 8 \
+        ${toString config.hardware.ipu6.videoDeviceNumber} || [ $? -eq 17 ]
+      echo /dev/video${toString config.hardware.ipu6.videoDeviceNumber} > "$V4L2_DEVICE_FILE"
+    '';
+  };
 }