Removed the DISABLE from HOST_KEEPALIVE_FEATURE option

Marlin/Conditionals.h

@@ -395,10 +395,10 @@
   #endif
 
   /**
-   * Avoid double-negatives for enabling features
+   * Host keep alive
    */
-  #if DISABLED(DISABLE_HOST_KEEPALIVE)
+  #ifndef HOST_KEEPALIVE_INTERVAL
-    #define HOST_KEEPALIVE_FEATURE
+    #define HOST_KEEPALIVE_INTERVAL 2
   #endif
 
   /**

Marlin/Configuration.h

@@ -733,13 +733,11 @@ const bool Z_MIN_PROBE_ENDSTOP_INVERTING = false; // set to true to invert the l
 //
 // Host Keepalive
 //
-// By default Marlin will send a busy status message to the host
+// When enabled Marlin will send a busy status message to the host
 // every couple of seconds when it can't accept commands.
 //
-//#define DISABLE_HOST_KEEPALIVE // Enable this option if your host doesn't like keepalive messages.
+#define HOST_KEEPALIVE_FEATURE    // Disable this if your host doesn't like keepalive messages
-#if DISABLED(DISABLE_HOST_KEEPALIVE)
+#define HOST_KEEPALIVE_INTERVAL 2 // Number of seconds between "busy" messages. Set with M113.
-  #define DEFAULT_KEEPALIVE_INTERVAL 2 // Number of seconds between "busy" messages. Set with M113.
-#endif
 
 //
 // M100 Free Memory Watcher

Marlin/Marlin_main.cpp

@@ -488,7 +488,7 @@ static bool send_ok[BUFSIZE];
 
   static MarlinBusyState busy_state = NOT_BUSY;
   static millis_t next_busy_signal_ms = 0;
-  uint8_t host_keepalive_interval = DEFAULT_KEEPALIVE_INTERVAL;
+  uint8_t host_keepalive_interval = HOST_KEEPALIVE_INTERVAL;
   #define KEEPALIVE_STATE(n) do{ busy_state = n; }while(0)
 #else
   #define host_keepalive() ;