Tweaks to planner.h

Marlin/planner.h

@@ -130,15 +130,24 @@ typedef struct {
 #define BLOCK_MOD(n) ((n)&(BLOCK_BUFFER_SIZE-1))
 
 class Planner {
-
   public:
 
     /**
-     * A ring buffer of moves described in steps
+     * The move buffer, calculated in stepper steps
+     *
+     * block_buffer is a ring buffer...
+     *
+     *             head,tail : indexes for write,read
+     *            head==tail : the buffer is empty
+     *            head!=tail : blocks are in the buffer
+     *   head==(tail-1)%size : the buffer is full
+     *
+     *  Writer of head is Planner::_buffer_line().
+     *  Reader of tail is Stepper::isr(). Always consider tail busy / read-only
      */
     static block_t block_buffer[BLOCK_BUFFER_SIZE];
     static volatile uint8_t block_buffer_head,      // Index of the next block to be pushed
-                            block_buffer_tail;
+                            block_buffer_tail;      // Index of the busy block, if any
 
     #if ENABLED(DISTINCT_E_FACTORS)
       static uint8_t last_extruder;                 // Respond to extruder change
@@ -273,9 +282,9 @@ class Planner {
     /**
      * Number of moves currently in the planner
      */
-    static uint8_t movesplanned() { return BLOCK_MOD(block_buffer_head - block_buffer_tail + BLOCK_BUFFER_SIZE); }
+    FORCE_INLINE static uint8_t movesplanned() { return BLOCK_MOD(block_buffer_head - block_buffer_tail + BLOCK_BUFFER_SIZE); }
 
-    static bool is_full() { return (block_buffer_tail == BLOCK_MOD(block_buffer_head + 1)); }
+    FORCE_INLINE static bool is_full() { return block_buffer_tail == next_block_index(block_buffer_head); }
 
     // Update multipliers based on new diameter measurements
     static void calculate_volumetric_multipliers();
@@ -529,8 +538,8 @@ class Planner {
     /**
      * Get the index of the next / previous block in the ring buffer
      */
-    static int8_t next_block_index(const int8_t block_index) { return BLOCK_MOD(block_index + 1); }
-    static int8_t prev_block_index(const int8_t block_index) { return BLOCK_MOD(block_index - 1); }
+    static constexpr int8_t next_block_index(const int8_t block_index) { return BLOCK_MOD(block_index + 1); }
+    static constexpr int8_t prev_block_index(const int8_t block_index) { return BLOCK_MOD(block_index - 1); }
 
     /**
      * Calculate the distance (not time) it takes to accelerate