nixos/ipu6: Fix device persistence and pipewire integration

  inherit (lib)

    mkDefault

    mkEnableOption

    mkForce

    mkIf

    mkOption

    optional

      '';

    };

    videoDeviceNumber = mkOption {

      type = types.int;

      default = 50;

      description = ''

        v4l2loopback device number for the relay output (`/dev/videoN`).

        Must be fixed so application camera permission grants, which are keyed to

        the PipeWire node name (derived from the sysfs device path), survive

        reboots. Choose a number above the IPU6 raw node range (typically 3-34)

        and any other v4l2loopback devices on the system.

      '';

    };

  };

  config = mkIf cfg.enable {

      ivsc-firmware

    ];

    # Restrict IPU6 raw nodes and media controller to root. DRIVERS== matches the

    # parent PCI device. TAG-="uaccess" blocks logind ACL grants at login.

    services.udev.extraRules = ''

      SUBSYSTEM=="intel-ipu6-psys", MODE="0660", GROUP="video"

      SUBSYSTEM=="media", DRIVERS=="intel-ipu6", MODE="0600", GROUP="root", TAG-="uaccess"

      SUBSYSTEM=="video4linux", DRIVERS=="intel-ipu6", MODE="0600", GROUP="root", TAG-="uaccess"

    '';

    # ipu6-camera-hal writes AIQ tuning data and debug logs here.

    systemd.tmpfiles.rules = [ "d /run/camera 0755 root video -" ];

    # Disable raw IPU6 nodes in WirePlumber. Matched via udev ID_V4L_PRODUCT=ipu6,

    # set by the kernel at device registration without requiring a device open.

    services.pipewire.wireplumber.extraConfig."ipu6-v4l2-rules" = {

      "monitor.v4l2.rules" = [

        {

          matches = [ { "device.product.name" = "ipu6"; } ];

          actions = {

            "update-props" = {

              "device.disabled" = true;

            };

          };

        }

      ];

    };

    services.v4l2-relayd.instances.ipu6 = {

      enable = mkDefault true;

        format = mkIf (cfg.platform != "ipu6") (mkDefault "NV12");

      };

    };

    # Override preStart/postStop from the v4l2-relayd module:

    # - Use a fixed device number so PipeWire node names (and application permission

    #   grants) are stable across reboots. Exit 17 (EEXIST) is success.

    # - Keep the device alive on stop so apps survive relay restarts via

    #   VIDIOC_DQBUF blocking rather than receiving errors.

    systemd.services.v4l2-relayd-ipu6 = {

      preStart = mkForce ''

        mkdir -p "$(dirname "$V4L2_DEVICE_FILE")"

        ${config.boot.kernelPackages.v4l2loopback.bin}/bin/v4l2loopback-ctl \

          add --name "Intel MIPI Camera" --exclusive-caps=1 ${toString cfg.videoDeviceNumber} || [ $? -eq 17 ]

        echo /dev/video${toString cfg.videoDeviceNumber} > "$V4L2_DEVICE_FILE"

      '';

      postStop = mkForce ''

        rm -rf "$(dirname "$V4L2_DEVICE_FILE")"

      '';

    };

  };

}