avr: introduce reference counter for network buffers.

avr/modules/network/buffer.asm

@@ -62,7 +62,7 @@ NET_Buffer_Alloc_noIrq:
   ldi xh, HIGH(netBuffers)
   m_fixedbuf_reserve NET_BUFFERS_SIZE, NET_BUFFERS_NUM
   brcc NET_Buffer_Alloc_end
-  ldi r17, (1<<NET_IFACE_BUFFER_INUSE_BIT)
+  ldi r17, (1<<NET_IFACE_BUFFER_INUSE_BIT0)            ; set refcounter to 1
   st X, r17
 NET_Buffer_Alloc_end:
   ret
@@ -80,7 +80,54 @@ NET_Buffer_ReleaseByAddr:
   push r15
     in r15, SREG
     cli
+    ld r16, X
+    swap r16
+    andi r16, 0x0f                      ; ref counter now in lower nibble
+    breq NET_Buffer_ReleaseByAddr_done  ; refcounter 0? -> not in use
+    dec r16
+    breq NET_Buffer_ReleaseByAddr_release
+    swap r16
+    push r17
+      ld r17, X
+      andi r17, 0x0f
+      or r16, r17
+      st X, r16
+    pop r17
+    rjmp NET_Buffer_ReleaseByAddr_done
+NET_Buffer_ReleaseByAddr_release:
     m_fixedbuf_release
+NET_Buffer_ReleaseByAddr_done:
+    out SREG, r15
+  pop r15
+  ret
+; @end
+
+
+
+; ---------------------------------------------------------------------------
+; @routine NET_Buffer_IncRef @global
+;
+; @param X pointer to start of buffer
+; @clobbers R16
+
+NET_Buffer_IncRef:
+  push r15
+    in r15, SREG
+    cli
+    ld r16, X
+    swap r16                            ; ref counter now in lower nibble
+    andi r16, 0x0f                      
+    breq NET_Buffer_IncRef_done         ; refcounter 0? -> not in use
+    inc r16
+    breq NET_Buffer_IncRef_done         ; don't increment if refcounter at max!!!
+    swap r16                            ; ref counter now in high nibble again
+    push r17
+      ld r17, X
+      andi r17, 0x0f                    ; clear ref counter in r17
+      or r16, r17                       ; or new ref counter into r17
+      st X, r16                         ; store new header byte
+    pop r17
+NET_Buffer_IncRef_done:
     out SREG, r15
   pop r15
   ret