Parametrize LA limits and threshold values

Allow the LA 1.5 MAX value to be configured in Configuration_adv.h.

Define a customizable LA10<>15 detection threshold in function of the
above limit.

Clamp the result of of the LA10->15 return value to always
respect the new LA_K_MAX.

Firmware/Configuration_adv.h

@@ -285,11 +285,13 @@
 #define LIN_ADVANCE
 
 #ifdef LIN_ADVANCE
-  #define LIN_ADVANCE_K 0  // Unit: mm compression per 1mm/s extruder speed
-  //#define LA_NOCOMPAT    // Disable Linear Advance 1.0 compatibility
-  //#define LA_LIVE_K      // Allow adjusting K in the Tune menu
-  //#define LA_DEBUG       // If enabled, this will generate debug information output over USB.
-  //#define LA_DEBUG_LOGIC // @wavexx: setup logic channels for isr debugging
+  #define LA_K_DEF    0        // Default K factor (Unit: mm compression per 1mm/s extruder speed)
+  #define LA_K_MAX    10       // Maximum acceptable K factor (exclusive, see notes in planner.cpp:plan_buffer_line)
+  #define LA_LA10_MIN LA_K_MAX // Lin. Advance 1.0 threshold value (inclusive)
+  //#define LA_NOCOMPAT        // Disable Linear Advance 1.0 compatibility
+  //#define LA_LIVE_K          // Allow adjusting K in the Tune menu
+  //#define LA_DEBUG           // If enabled, this will generate debug information output over USB.
+  //#define LA_DEBUG_LOGIC     // @wavexx: setup logic channels for isr debugging
 #endif
 
 // Arc interpretation settings:

Firmware/Marlin_main.cpp

@@ -2066,7 +2066,7 @@ static float probe_pt(float x, float y, float z_before) {
 inline void gcode_M900() {
     float newK = code_seen('K') ? code_value_float() : -2;
 #ifdef LA_NOCOMPAT
-    if (newK >= 0 && newK < 10)
+    if (newK >= 0 && newK < LA_K_MAX)
         extruder_advance_K = newK;
     else
         SERIAL_ECHOLNPGM("K out of allowed range!");

Firmware/la10compat.cpp

@@ -1,5 +1,6 @@
 #include "la10compat.h"
 #include "Marlin.h"
+#include <float.h>
 
 
 static LA10C_MODE la10c_mode = LA10C_UNKNOWN; // Current LA compatibility mode
@@ -38,7 +39,9 @@ void la10c_mode_change(LA10C_MODE mode)
 static float la10c_convert(float k)
 {
     float new_K = k * 0.004 - 0.05;
-    return (new_K < 0? 0: new_K);
+    return new_K < 0? 0:
+           new_K > (LA_K_MAX - FLT_EPSILON)? (LA_K_MAX - FLT_EPSILON):
+           new_K;
 }
 
 
@@ -52,11 +55,11 @@ float la10c_value(float k)
         else if(k < 0)
             return -1;
 
-        la10c_mode_change(k < 10? LA10C_LA15: LA10C_LA10);
+        la10c_mode_change(k < LA_LA10_MIN? LA10C_LA15: LA10C_LA10);
     }
 
     if(la10c_mode == LA10C_LA15)
-        return (k >= 0 && k < 10? k: -1);
+        return (k >= 0 && k < LA_K_MAX? k: -1);
     else
         return (k >= 0? la10c_convert(k): -1);
 }

Firmware/planner.cpp

@@ -126,7 +126,7 @@ float extrude_min_temp=EXTRUDE_MINTEMP;
 #endif
 
 #ifdef LIN_ADVANCE
-float extruder_advance_K = LIN_ADVANCE_K;
+float extruder_advance_K = LA_K_DEF;
 float position_float[NUM_AXIS];
 #endif