From 9b1badb3100dfc3952a46a9ca69be9e362c6c6fb Mon Sep 17 00:00:00 2001
From: Martin Preuss <martin@aquamaniac.de>
Date: Mon, 18 Aug 2025 18:03:24 +0200
Subject: [PATCH] avr: introduce reference counter for network buffers.

---
 avr/common/m_fixedbuffers.asm  |  2 +-
 avr/modules/network/buffer.asm | 49 +++++++++++++++++++++++++++++++++-
 avr/modules/network/defs.asm   | 12 ++++++---
 3 files changed, 57 insertions(+), 6 deletions(-)

diff --git a/avr/common/m_fixedbuffers.asm b/avr/common/m_fixedbuffers.asm
index b2831e1..9ad97a3 100644
--- a/avr/common/m_fixedbuffers.asm
+++ b/avr/common/m_fixedbuffers.asm
@@ -52,7 +52,7 @@ l_loop:
   brcs l_loop
   rjmp l_end           ; use cleared CFLAG
 l_foundfree:
-  ldi r16, 0x80        ; mark as used
+  ldi r16, 0x10        ; mark as used
   st X, r16
   mov r16, r17
   sec                  ; set CFLAG, return bufnum in r16, pointre in X
diff --git a/avr/modules/network/buffer.asm b/avr/modules/network/buffer.asm
index 5404450..c8e54e9 100644
--- a/avr/modules/network/buffer.asm
+++ b/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
diff --git a/avr/modules/network/defs.asm b/avr/modules/network/defs.asm
index ac409a7..b670706 100644
--- a/avr/modules/network/defs.asm
+++ b/avr/modules/network/defs.asm
@@ -12,12 +12,16 @@
 
 .equ NET_BUFFERS_SIZE                   = 28 ; CAVE: need to adapt routine NET_Buffer_Locate when changing this value!!
 
-.equ NET_MSGNUMINBUF_SIZE               =  8 ; max buffer nums in ringbuffer (global incoming)
-
-.equ NET_IFACE_OUTMSGBUF_SIZE           =  8 ; max buffer nums in ringbuffer (per interface outbound)
+;.equ NET_MSGNUMINBUF_SIZE               =  8 ; max buffer nums in ringbuffer (global incoming)
+;.equ NET_IFACE_OUTMSGBUF_SIZE           =  8 ; max buffer nums in ringbuffer (per interface outbound)
 
 
-.equ NET_IFACE_BUFFER_INUSE_BIT         = 7
+.equ NET_IFACE_BUFFER_INUSE_BIT3        = 7
+.equ NET_IFACE_BUFFER_INUSE_BIT2        = 6
+.equ NET_IFACE_BUFFER_INUSE_BIT1        = 5
+.equ NET_IFACE_BUFFER_INUSE_BIT0        = 4
+.equ NET_IFACE_BUFFER_IFACENUM3_BIT     = 3
+.equ NET_IFACE_BUFFER_IFACENUM2_BIT     = 2
 .equ NET_IFACE_BUFFER_IFACENUM1_BIT     = 1
 .equ NET_IFACE_BUFFER_IFACENUM0_BIT     = 0