fix(nb): resolve keyboard/touchpad and btrfs read-only issues after suspend

This commit addresses two critical suspend/resume issues on the nb host:

1. Keyboard and touchpad not working after suspend
   - Added i2c_hid_acpi kernel module
   - Created systemd service to reload the module after resume
   - Excluded input devices from TLP USB autosuspend

2. /nix/persist becoming read-only after suspend
   - Moved swap from /nix/persist to dedicated @swap subvolume
   - Added systemd service to remount /nix/persist if needed
   - Separated swap from persistent data to prevent btrfs corruption

Changes:
- Created hosts/nb/modules/suspend-fixes.nix with resume hooks
- Updated swap path from /nix/persist/swapfile to /swap/swapfile
- Added /swap filesystem mount for @swap btrfs subvolume
- Added USB_EXCLUDE_INPUT=1 to TLP configuration

Note: Manual step required before deployment - create @swap subvolume.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

hosts/nb/configuration.nix

@@ -30,6 +30,7 @@ in {
       ./modules/ollama.nix
       ./modules/qdrant.nix
       ./modules/battery-brightness.nix
+      ./modules/suspend-fixes.nix
 
       ./cachix.nix
       ./users
@@ -79,7 +80,7 @@ in {
   services.irqbalance.enable = false;
 
   swapDevices = [ {
-    device = "/nix/persist/swapfile";
+    device = "/swap/swapfile";
     size = 96 * 1024;  # Size is in megabytes (96GB for full hibernation with 92GB RAM)
   } ];
 

hosts/nb/hardware-configuration.nix

@@ -92,6 +92,16 @@
     ];
   };
 
+  fileSystems."/swap" = {
+    device = "/dev/mapper/root";
+    fsType = "btrfs";
+    neededForBoot = true;
+    options = [
+      "subvol=@swap"
+      "noatime"
+    ];
+  };
+
   swapDevices = [ ];
 
   # Enables DHCP on each ethernet and wireless interface. In case of scripted networking

hosts/nb/modules/desktop/default.nix

@@ -159,6 +159,7 @@ in {
     USB_EXCLUDE_PHONE = 0;
     USB_EXCLUDE_PRINTER = 1;
     USB_EXCLUDE_WWAN = 0;
+    USB_EXCLUDE_INPUT = 1;  # Exclude keyboard/touchpad to prevent suspend issues
 
     # Audio power saving
     SOUND_POWER_SAVE_ON_AC = 0;

hosts/nb/modules/suspend-fixes.nix

@@ -0,0 +1,32 @@
+{ config, pkgs, lib, ... }:
+
+{
+  # Add i2c_hid_acpi kernel module for proper input device support
+  boot.kernelModules = [ "i2c_hid_acpi" ];
+
+  # Systemd service to reload i2c_hid_acpi module after resume
+  # This fixes keyboard and touchpad not working after suspend
+  systemd.services.reload-i2c-hid-after-resume = {
+    description = "Reload i2c_hid_acpi module after resume to fix keyboard/touchpad";
+    after = [ "suspend.target" "hibernate.target" "hybrid-sleep.target" ];
+    wantedBy = [ "suspend.target" "hibernate.target" "hybrid-sleep.target" ];
+    serviceConfig = {
+      Type = "oneshot";
+      ExecStart = "${pkgs.bash}/bin/bash -c '${pkgs.kmod}/bin/rmmod i2c_hid_acpi; ${pkgs.kmod}/bin/modprobe i2c_hid_acpi'";
+    };
+  };
+
+  # Systemd service to remount /nix/persist if it becomes read-only after resume
+  # This fixes the btrfs read-only issue that can occur with LUKS + btrfs on suspend/resume
+  systemd.services.remount-persist-after-resume = {
+    description = "Remount /nix/persist read-write if needed after resume";
+    after = [ "suspend.target" "hibernate.target" "hybrid-sleep.target" ];
+    wantedBy = [ "suspend.target" "hibernate.target" "hybrid-sleep.target" ];
+    serviceConfig = {
+      Type = "oneshot";
+      ExecStart = "${pkgs.util-linux}/bin/mount -o remount,rw /nix/persist";
+      # Don't fail if already mounted rw
+      SuccessExitStatus = [ 0 32 ];
+    };
+  };
+}