HID: asus: add support for the asus-wmi brightness handler

If the asus-wmi brightness handler is available, send the
keyboard brightness events to it instead of passing them
to userspace. If it is not, fall back to sending them to it.

Reviewed-by: Luke D. Jones <luke@ljones.dev>
Tested-by: Luke D. Jones <luke@ljones.dev>
Reviewed-by: Denis Benato <benato.denis96@gmail.com>
Acked-by: Benjamin Tissoires <bentiss@kernel.org>
Signed-off-by: Antheas Kapenekakis <lkml@antheas.dev>
Link: https://patch.msgid.link/20260122075044.5070-12-lkml@antheas.dev
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>

Author: antheas

drivers/hid/hid-asus.c

@@ -324,6 +324,17 @@ static int asus_event(struct hid_device *hdev, struct hid_field *field,
 			 usage->hid & HID_USAGE);
 	}
 
+	if (usage->type == EV_KEY && value) {
+		switch (usage->code) {
+		case KEY_KBDILLUMUP:
+			return !asus_hid_event(ASUS_EV_BRTUP);
+		case KEY_KBDILLUMDOWN:
+			return !asus_hid_event(ASUS_EV_BRTDOWN);
+		case KEY_KBDILLUMTOGGLE:
+			return !asus_hid_event(ASUS_EV_BRTTOGGLE);
+		}
+	}
+
 	return 0;
 }