Split the software endstop capability by axis.

Marlin/Configuration.h

@@ -785,10 +785,30 @@
 #define Y_MAX_POS Y_BED_SIZE
 #define Z_MAX_POS 200
 
-// If enabled, axes won't move below MIN_POS in response to movement commands.
+/**
+ * Software Endstops
+ *
+ * - Prevent moves outside the set machine bounds.
+ * - Individual axes can be disabled, if desired.
+ * - X and Y only apply to Cartesian robots.
+ * - Use 'M211' to set software endstops on/off or report current state
+ */
+
+// Min software endstops constrain movement within minimum coordinate bounds
 #define MIN_SOFTWARE_ENDSTOPS
-// If enabled, axes won't move above MAX_POS in response to movement commands.
+#if ENABLED(MIN_SOFTWARE_ENDSTOPS)
+  #define MIN_SOFTWARE_ENDSTOP_X
+  #define MIN_SOFTWARE_ENDSTOP_Y
+  #define MIN_SOFTWARE_ENDSTOP_Z
+#endif
+
+// Max software endstops constrain movement within maximum coordinate bounds
 #define MAX_SOFTWARE_ENDSTOPS
+#if ENABLED(MAX_SOFTWARE_ENDSTOPS)
+  #define MAX_SOFTWARE_ENDSTOP_X
+  #define MAX_SOFTWARE_ENDSTOP_Y
+  #define MAX_SOFTWARE_ENDSTOP_Z
+#endif
 
 /**
  * Filament Runout Sensor

Marlin/src/inc/Conditionals_post.h

@@ -793,7 +793,17 @@
   #define HEATER_IDLE_HANDLER (ENABLED(ADVANCED_PAUSE_FEATURE) || ENABLED(PROBING_HEATERS_OFF))
 
   /**
-   * Delta radius/rod trimmers/angle trimmers
+   * Only constrain Z on DELTA / SCARA machines
+   */
+  #if IS_KINEMATIC
+    #undef MIN_SOFTWARE_ENDSTOP_X
+    #undef MIN_SOFTWARE_ENDSTOP_Y
+    #undef MAX_SOFTWARE_ENDSTOP_X
+    #undef MAX_SOFTWARE_ENDSTOP_Y
+  #endif
+
+  /**
+   * Delta endstops, radius/rod trimmers, angle trimmers
    */
   #if ENABLED(DELTA)
     #ifndef DELTA_CALIBRATION_RADIUS

Marlin/src/inc/SanityCheck.h

@@ -254,6 +254,25 @@
 static_assert(X_MAX_LENGTH >= X_BED_SIZE && Y_MAX_LENGTH >= Y_BED_SIZE,
   "Movement bounds ([XY]_MIN_POS, [XY]_MAX_POS) are too narrow to contain [XY]_BED_SIZE.");
 
+/**
+ * Granular software endstops (Marlin >= 1.1.7)
+ */
+#if ENABLED(MIN_SOFTWARE_ENDSTOPS) && DISABLED(MIN_SOFTWARE_ENDSTOP_Z)
+  #if IS_KINEMATIC
+    #error "MIN_SOFTWARE_ENDSTOPS on DELTA/SCARA also requires MIN_SOFTWARE_ENDSTOP_Z."
+  #elif DISABLED(MIN_SOFTWARE_ENDSTOP_X) && DISABLED(MIN_SOFTWARE_ENDSTOP_Y)
+    #error "MIN_SOFTWARE_ENDSTOPS requires at least one of the MIN_SOFTWARE_ENDSTOP_[XYZ] options."
+  #endif
+#endif
+
+#if ENABLED(MAX_SOFTWARE_ENDSTOPS) && DISABLED(MAX_SOFTWARE_ENDSTOP_Z)
+  #if IS_KINEMATIC
+    #error "MAX_SOFTWARE_ENDSTOPS on DELTA/SCARA also requires MAX_SOFTWARE_ENDSTOP_Z."
+  #elif DISABLED(MAX_SOFTWARE_ENDSTOP_X) && DISABLED(MAX_SOFTWARE_ENDSTOP_Y)
+    #error "MAX_SOFTWARE_ENDSTOPS requires at least one of the MAX_SOFTWARE_ENDSTOP_[XYZ] options."
+  #endif
+#endif
+
 /**
  * Progress Bar
  */

Marlin/src/lcd/ultralcd.cpp

@@ -2834,17 +2834,35 @@ void kill_screen(const char* lcd_msg) {
       float min = current_position[axis] - 1000,
             max = current_position[axis] + 1000;
 
-      #if HAS_SOFTWARE_ENDSTOPS
       // Limit to software endstops, if enabled
-        if (soft_endstops_enabled) {
+      #if ENABLED(MIN_SOFTWARE_ENDSTOPS) || ENABLED(MAX_SOFTWARE_ENDSTOPS)
-          #if ENABLED(MIN_SOFTWARE_ENDSTOPS)
+        if (soft_endstops_enabled) switch (axis) {
-            min = soft_endstop_min[axis];
+          case X_AXIS:
+            #if ENABLED(MIN_SOFTWARE_ENDSTOP_X)
+              min = soft_endstop_min[X_AXIS];
             #endif
-          #if ENABLED(MAX_SOFTWARE_ENDSTOPS)
+            #if ENABLED(MAX_SOFTWARE_ENDSTOP_X)
-            max = soft_endstop_max[axis];
+              max = soft_endstop_max[X_AXIS];
             #endif
+            break;
+          case Y_AXIS:
+            #if ENABLED(MIN_SOFTWARE_ENDSTOP_Y)
+              min = soft_endstop_min[Y_AXIS];
+            #endif
+            #if ENABLED(MAX_SOFTWARE_ENDSTOP_Y)
+              max = soft_endstop_max[Y_AXIS];
+            #endif
+            break;
+          case Z_AXIS:
+            #if ENABLED(MIN_SOFTWARE_ENDSTOP_Z)
+              min = soft_endstop_min[Z_AXIS];
+            #endif
+            #if ENABLED(MAX_SOFTWARE_ENDSTOP_Z)
+              max = soft_endstop_max[Z_AXIS];
+            #endif
+            break;
         }
-      #endif
+      #endif // MIN_SOFTWARE_ENDSTOPS || MAX_SOFTWARE_ENDSTOPS
 
       // Delta limits XY based on the current offset from center
       // This assumes the center is 0,0

Marlin/src/module/motion.cpp

@@ -456,29 +456,28 @@ float soft_endstop_min[XYZ] = { X_MIN_BED, Y_MIN_BED, Z_MIN_POS },
 
   /**
    * Constrain the given coordinates to the software endstops.
+   *
+   * NOTE: This will only apply to Z on DELTA and SCARA. XY is
+   *       constrained to a circle on these kinematic systems.
    */
-
-  // NOTE: This makes no sense for delta beds other than Z-axis.
-  //       For delta the X/Y would need to be clamped at
-  //       DELTA_PRINTABLE_RADIUS from center of bed, but delta
-  //       now enforces is_position_reachable for X/Y regardless
-  //       of HAS_SOFTWARE_ENDSTOPS, so that enforcement would be
-  //       redundant here.
-
   void clamp_to_software_endstops(float target[XYZ]) {
     if (!soft_endstops_enabled) return;
-    #if ENABLED(MIN_SOFTWARE_ENDSTOPS)
+    #if ENABLED(MIN_SOFTWARE_ENDSTOP_X)
-      #if DISABLED(DELTA)
       NOLESS(target[X_AXIS], soft_endstop_min[X_AXIS]);
+    #endif
+    #if ENABLED(MIN_SOFTWARE_ENDSTOP_Y)
       NOLESS(target[Y_AXIS], soft_endstop_min[Y_AXIS]);
     #endif
+    #if ENABLED(MIN_SOFTWARE_ENDSTOP_Z)
       NOLESS(target[Z_AXIS], soft_endstop_min[Z_AXIS]);
     #endif
-    #if ENABLED(MAX_SOFTWARE_ENDSTOPS)
+    #if ENABLED(MAX_SOFTWARE_ENDSTOP_X)
-      #if DISABLED(DELTA)
       NOMORE(target[X_AXIS], soft_endstop_max[X_AXIS]);
+    #endif
+    #if ENABLED(MAX_SOFTWARE_ENDSTOP_Y)
       NOMORE(target[Y_AXIS], soft_endstop_max[Y_AXIS]);
     #endif
+    #if ENABLED(MAX_SOFTWARE_ENDSTOP_Z)
       NOMORE(target[Z_AXIS], soft_endstop_max[Z_AXIS]);
     #endif
   }