nixpkgs/upstart-jobs/udev.nix

{pkgs, config, ...}:

###### interface
let
  inherit (pkgs.lib) mkOption mkIf;

  options = {
    services = {
      udev = {

        addFirmware = mkOption {
          default = [];
          example = ["/mnt/big-storage/firmware/"];
          description = "
            To specify firmware that is not too spread to ensure 
            a package, or have an interactive process of extraction
            and cannot be redistributed.
          ";
          merge = pkgs.lib.mergeListOption;
        };

        addUdevPkgs = mkOption {
          default = [];
          description = "
            List of packages containing udev rules.
          ";
          merge = pkgs.lib.mergeListOption;
        };
        
        sndMode = mkOption {
          default = "0600";
          example = "0666";
          description = "
            Permissions for /dev/snd/*, in case you have multiple 
            logged in users or if the devices belong to root for 
            some reason.
          ";
        };
      };
    };
  };
in

###### implementation

let

  inherit (pkgs) substituteAll stdenv writeText udev procps;

  cfg = config.services.udev;


  firmwareLoader = substituteAll {
    src = ./udev-firmware-loader.sh;
    path = "${stdenv.coreutils}/bin";
    isExecutable = true;
    inherit firmwareDirs;
  };

  firmwareDirs = config.services.udev.addFirmware;
  extraUdevPkgs = config.services.udev.addUdevPkgs;

  modprobe = config.system.sbin.modprobe;
    
  nixRules = writeText "90-nix.rules" ''
  
    # Miscellaneous devices.
    KERNEL=="sonypi",               MODE="0666"
    KERNEL=="kvm",                  MODE="0666"
    KERNEL=="kqemu",                NAME="%k", MODE="0666"

    # Create symlinks for CD/DVD devices.
    ACTION=="add", SUBSYSTEM=="block", ENV{ID_CDROM}=="?*", SYMLINK+="cdrom cdrom-%k"
    ACTION=="add", SUBSYSTEM=="block", ENV{ID_CDROM_CD_RW}=="?*", SYMLINK+="cdrw cdrw-%k"
    ACTION=="add", SUBSYSTEM=="block", ENV{ID_CDROM_DVD}=="?*", SYMLINK+="dvd dvd-%k"
    ACTION=="add", SUBSYSTEM=="block", ENV{ID_CDROM_DVD_RW}=="?*", SYMLINK+="dvdrw dvdrw-%k"
    
    # ALSA sound devices.
    KERNEL=="controlC[0-9]*",       NAME="snd/%k", MODE="${cfg.sndMode}"
    KERNEL=="hwC[D0-9]*",           NAME="snd/%k", MODE="${cfg.sndMode}"
    KERNEL=="pcmC[D0-9cp]*",        NAME="snd/%k", MODE="${cfg.sndMode}"
    KERNEL=="midiC[D0-9]*",         NAME="snd/%k", MODE="${cfg.sndMode}"
    KERNEL=="timer",                NAME="snd/%k", MODE="${cfg.sndMode}"
    KERNEL=="seq",                  NAME="snd/%k", MODE="${cfg.sndMode}"

    # Firmware loading.
    SUBSYSTEM=="firmware",          ACTION=="add", RUN+="${firmwareLoader}"
    
  '';
  
  # Perform substitutions in all udev rules files.
  udevRules = stdenv.mkDerivation {
    name = "udev-rules";
    #src = cleanSource ./udev-rules;
    buildCommand = ''
      ensureDir $out
      ln -s ${nixRules} $out/${nixRules.name}
      shopt -s nullglob
      cp ${udev}/*/udev/rules.d/*.rules $out/
      
      ${if config.boot.hardwareScan then
        ''
          substituteInPlace $out/80-drivers.rules \
            --replace /sbin/modprobe ${modprobe}/sbin/modprobe
        ''
        else
        ''
          rm $out/80-drivers.rules
        ''
      }
      for i in ${toString extraUdevPkgs}; do
        for j in $i/*/udev/rules.d/*; do
          ln -s $j $out/$(basename $j)
        done
      done
    ''; # */
  };

  # The udev configuration file.
  conf = writeText "udev.conf" ''
    udev_rules="${udevRules}"
    #udev_log="debug"
  '';

  # Dummy file indicating whether we've run udevtrigger/udevsettle.
  # Since that *recreates* all device nodes with default permissions,
  # it's not nice to do that when a user is logged in (it messes up
  # the permissions set by pam_devperm).
  # !!! Actually, this makes the udev configuration less declarative;
  # changes may not take effect until the user reboots.  We should
  # find a better way to preserve the permissions of logged-in users.
  devicesCreated = "/var/run/devices-created";

in

{

  require = [
    options
  ];

  services = {
    extraJobs = [{
      name = "udev";
      
      job = ''
        start on startup
        stop on shutdown

        env UDEV_CONFIG_FILE=${conf}

        start script
            echo "" > /proc/sys/kernel/hotplug

            # Get rid of possible old udev processes.
            ${procps}/bin/pkill -u root "^udevd$" || true

            # Do the loading of additional stage 2 kernel modules.
            # Maybe this isn't the best place...
            for i in ${toString config.boot.kernelModules}; do
                echo "Loading kernel module $i..."
                ${modprobe}/sbin/modprobe $i || true
            done

            # Start udev.
            ${udev}/sbin/udevd --daemon

            # Let udev create device nodes for all modules that have already
            # been loaded into the kernel (or for which support is built into
            # the kernel).
            if ! test -e ${devicesCreated}; then
                ${udev}/sbin/udevadm trigger
                ${udev}/sbin/udevadm settle # wait for udev to finish
                touch ${devicesCreated}
            fi

            # Kill udev, let Upstart restart and monitor it.  (This is nasty,
            # but we have to run `udevadm trigger' first.  Maybe we can use
            # Upstart's `binary' keyword, but it isn't implemented yet.)
            if ! ${procps}/bin/pkill -u root "^udevd$"; then
                echo "couldn't stop udevd"
            fi

            while ${procps}/bin/pgrep -u root "^udevd$"; do
                sleep 1
            done

            initctl emit new-devices
        end script

        respawn ${udev}/sbin/udevd
      '';

      passthru = {inherit udevRules;};
    }];
  };
}