Replace sound tri-state with playback/capture booleans

Instead of passing raw crosvm attrsets, sound is now configured
with two booleans: sound.playback (default true) and sound.capture
(default false, implies playback).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

CLAUDE.md

@@ -94,7 +94,7 @@ See README.md for full usage details and options.
 
 ### Key Patterns
 
-- **Option tri-state**: `gpu`, `sound`, and similar options accept `false` (disabled), `true` (default config), or an attrset (custom config). Built into crosvm args via `lib/helpers.nix`.
+- **Option tri-state**: `gpu` and similar options accept `false` (disabled), `true` (default config), or an attrset (custom config). Built into crosvm args via `lib/helpers.nix`. Note: `sound` uses a submodule with `playback` and `capture` booleans instead.
 - **Socket activation chain**: command socket → proxy template service → VM service → crosvm
 - **Offline-by-default networking**: VMs have no network unless `network.interfaces` is configured with TAP interfaces.
 - **Root overlay**: qcow2-backed (default) or tmpfs-backed overlayfs upper layer. Ephemeral — created at VM start, deleted at stop.

README.md

@@ -197,7 +197,8 @@ For mpv, make sure you use `--vo=wlshm`. Other backends probably won't work.
 | `copyChannel` | bool | `false` | Include NixOS channel in rootfs (same nixpkgs rev used to build the VM) |
 | `kernelParams` | list of strings | `[]` | Extra kernel command line parameters |
 | `gpu` | bool or attrset | `true` | GPU config (false=disabled, true=default, attrset=custom) |
-| `sound` | bool or attrset | `true` | Sound config (false=disabled, true=default PulseAudio, attrset=custom) |
+| `sound.playback` | bool | `true` | Enable sound playback |
+| `sound.capture` | bool | `false` | Enable sound capture (implies playback) |
 | `sharedDirectories` | attrsOf submodule | `{}` | Shared directories via virtiofsd (keys are fs tags, see below) |
 | `pciDevices` | list of attrsets | `[]` | PCI devices to passthrough (path + optional kv pairs) |
 | `guestPrograms` | list of packages | `[]` | VM-specific packages |
@@ -312,9 +313,8 @@ VMs with `gpu = false` do not connect to the host Wayland socket and are unaffec
 ### Sound Configuration
 
 ```nix
-sound = false;  # Disabled
-sound = true;   # Default PulseAudio config
-sound = { backend = "pulse"; capture = true; };  # Custom
+sound.playback = false;  # Disabled
+sound.capture = true;    # Playback + capture
 ```
 
 ### PCI Passthrough Configuration

example/configuration.nix

@@ -79,7 +79,7 @@
           memory = 512;
           cpus = 2;
           gpu = false;
-          sound = false;
+          sound.playback = false;
           sharedHome = false;
           network = {
             nameservers = [ "8.8.8.8" ];

modules/options.nix

@@ -347,19 +347,17 @@ let
         '';
       };
 
-      sound = lib.mkOption {
-        type = lib.types.either lib.types.bool crosvmAttrsetType;
-        default = true;
-        description = ''
-          Sound configuration. Set to false to disable, true for default PulseAudio config,
-          or an attrset for custom --virtio-snd options.
-        '';
-        example = lib.literalExpression ''
-          {
-            backend = "pulse";
-            capture = true;
-          }
-        '';
+      sound = {
+        playback = lib.mkOption {
+          type = lib.types.bool;
+          default = true;
+          description = "Enable sound playback.";
+        };
+        capture = lib.mkOption {
+          type = lib.types.bool;
+          default = false;
+          description = "Enable sound capture. Implies playback.";
+        };
       };
 
       sharedDirectories = lib.mkOption {

modules/scripts.nix

@@ -35,13 +35,18 @@ let
   userGid = config.users.groups.${config.users.users.${cfg.user}.group}.gid;
   userRuntimeDir = "/run/user/${toString userUid}";
 
-  # Default PulseAudio sound configuration
-  defaultSoundConfig = {
-    backend = "pulse";
-    capture = false;
-    pulse_socket_path = "${userRuntimeDir}/pulse/native";
-    pulse_cookie_path = "/home/${cfg.user}/.config/pulse/cookie";
-  };
+  # Build effective sound config from sound options
+  mkSoundConfig =
+    sound:
+    if sound.playback || sound.capture then
+      {
+        backend = "pulse";
+        capture = sound.capture;
+        pulse_socket_path = "${userRuntimeDir}/pulse/native";
+        pulse_cookie_path = "/home/${cfg.user}/.config/pulse/cookie";
+      }
+    else
+      null;
 
   # Default GPU configuration
   defaultGpuConfig = {
@@ -58,7 +63,7 @@ let
     vm:
     let
       # Enable pipewire in guest when sound is enabled
-      soundConfig = lib.optionalAttrs (vm.sound != false) {
+      soundConfig = lib.optionalAttrs (vm.sound.playback || vm.sound.capture) {
         services.pipewire = {
           enable = lib.mkDefault true;
           pulse.enable = lib.mkDefault true;
@@ -170,8 +175,8 @@ let
       # GPU config: false = disabled, true = default config, attrset = custom config
       effectiveGpu = resolveOptionalConfig defaultGpuConfig vm.gpu;
 
-      # Sound config: false = disabled, true = default pulse config, attrset = custom config
-      effectiveSound = resolveOptionalConfig defaultSoundConfig vm.sound;
+      # Sound config from playback/capture booleans
+      effectiveSound = mkSoundConfig vm.sound;
 
       # Convert BDF to sysfs path
       bdfToSysfs = bdf: "/sys/bus/pci/devices/${normalizeBdf bdf}";