specify what controller u wanna use, instead of all

src/main/java/dev/isxander/controlify/controllermanager/SDLControllerManager.java

@@ -18,6 +18,7 @@
 import dev.isxander.controlify.driver.steamdeck.SteamDeckDriver;
 import dev.isxander.controlify.driver.steamdeck.SteamDeckUtil;
 import dev.isxander.controlify.hid.ControllerHIDService;
+import dev.isxander.controlify.hid.ControllerSpecify;
 import dev.isxander.controlify.hid.HIDDevice;
 import dev.isxander.controlify.hid.HIDID;
 import dev.isxander.controlify.utils.CUtil;
@@ -78,6 +79,11 @@ public void tick(boolean outOfFocus) {
                     SDL_JoystickID jid = event.jdevice.which;
                     logger.validateIsTrue(jid != null, "event.jdevice.which was null during SDL_EVENT_JOYSTICK_ADDED event");
 
+                    if (!isAssignedToThisInstance(jid)) {
+                        logger.debugLog("Ignoring hotplugged joystick {} - not assigned to this instance", jid.intValue());
+                        break;
+                    }
+
                     logger.debugLog("SDL event: Joystick added: {}", jid.intValue());
 
                     UniqueControllerID ucid = new SDLUniqueControllerID(jid);
@@ -111,12 +117,39 @@ public void tick(boolean outOfFocus) {
         super.tick(outOfFocus);
     }
 
+    private boolean isAssignedToThisInstance(SDL_JoystickID jid) {
+        ControllerSpecify cfg = ControllerSpecify.get();
+        if (!cfg.isFilteringEnabled()) return true;
+
+        SDL_Joystick tempHandle = SDL_OpenJoystick(jid);
+        if (tempHandle == null) {
+            logger.warn("Could not open joystick {} to check serial: {}", jid.intValue(), SDL_GetError());
+            return false;
+        }
+
+        try {
+            String serial = SDL_GetJoystickSerial(tempHandle);
+            if (serial == null) {
+                logger.warn("Joystick {} reported no serial number - cannot filter by MAC for this device", jid.intValue());
+                return false;
+            }
+            return ControllerSpecify.normalizeMac(serial).equals(ControllerSpecify.normalizeMac(cfg.getAssignedControllerMac()));
+        } finally {
+            SDL_CloseJoystick(tempHandle);
+        }
+    }
+
     @Override
     public void discoverControllers() {
         logger.debugLog("Discovering controllers...");
 
         SDL_JoystickID[] joysticks = SDL_GetJoysticks();
         for (SDL_JoystickID jid : joysticks) {
+            if (!isAssignedToThisInstance(jid)) {
+                logger.debugLog("Skipping joystick {} - not assigned to this instance", jid.intValue());
+                continue;
+            }
+
             Optional<ControllerEntity> controllerOpt = tryCreate(
                     new SDLUniqueControllerID(jid),
                     fetchTypeFromSDL(jid)

src/main/java/dev/isxander/controlify/hid/ControllerSpecify.java

@@ -0,0 +1,73 @@
+package dev.isxander.controlify.hid;
+
+import com.google.gson.Gson;
+import com.google.gson.GsonBuilder;
+import dev.isxander.controlify.platform.main.PlatformMainUtil;
+import dev.isxander.controlify.utils.CUtil;
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.Locale;
+
+public class ControllerSpecify {
+    private static final Gson GSON = new GsonBuilder().setPrettyPrinting().create();
+    private static final Path CONFIG_PATH = PlatformMainUtil.getConfigDir().resolve("controlify-controllerspecify.json");
+
+    private static ControllerSpecify instance;
+
+    private String assignedControllerMac = "";
+
+    public static ControllerSpecify get() {
+        if (instance == null) {
+            instance = load();
+        }
+        return instance;
+    }
+
+    private static ControllerSpecify load() {
+        if (Files.exists(CONFIG_PATH)) {
+            try {
+                String json = Files.readString(CONFIG_PATH);
+                ControllerSpecify loaded = GSON.fromJson(json, ControllerSpecify.class);
+                if (loaded != null) {
+                    CUtil.LOGGER.log("Loaded ControllerSpecify config: assignedControllerMac='{}'", loaded.assignedControllerMac);
+                    return loaded;
+                }
+            } catch (IOException e) {
+                CUtil.LOGGER.error("Failed to read controlify-controllerspecify.json, using default", e);
+            }
+        }
+
+        ControllerSpecify fresh = new ControllerSpecify();
+        fresh.save();
+        CUtil.LOGGER.log("Created default controlify-controllerspecify.json at {} - set assignedControllerMac to restrict this instance to one controller", CONFIG_PATH);
+        return fresh;
+    }
+
+    public void save() {
+        try {
+            Files.writeString(CONFIG_PATH, GSON.toJson(this));
+        } catch (IOException e) {
+            CUtil.LOGGER.error("Failed to write controlify-controllerspecify.json", e);
+        }
+    }
+
+    public boolean isFilteringEnabled() {
+        return assignedControllerMac != null && !assignedControllerMac.isBlank();
+    }
+
+    public String getAssignedControllerMac() {
+        return assignedControllerMac;
+    }
+
+    public void setAssignedControllerMac(String mac) {
+        this.assignedControllerMac = mac;
+        save();
+    }
+
+    public static String normalizeMac(String mac) {
+        if (mac == null) return "";
+        return mac.replace(":", "").replace("-", "").trim().toLowerCase(Locale.ROOT);
+    }
+}