From 784c83d23ae0307345004e18abf11d09f5d07d36 Mon Sep 17 00:00:00 2001
From: Stefan Rueger <stefan.rueger@urclocks.com>
Date: Thu, 1 Jun 2023 21:18:55 +0100
Subject: [PATCH] Prevent terminal write error in r/o region when memory
 unchanged

---
 src/avrcache.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/src/avrcache.c b/src/avrcache.c
index da40c7a7..6df68d51 100644
--- a/src/avrcache.c
+++ b/src/avrcache.c
@@ -625,9 +625,6 @@ int avr_read_byte_cached(const PROGRAMMER *pgm, const AVRPART *p, const AVRMEM *
 int avr_write_byte_cached(const PROGRAMMER *pgm, const AVRPART *p, const AVRMEM *mem,
   unsigned long addr, unsigned char data) {
 
-  if(pgm->readonly && pgm->readonly(pgm, p, mem, addr))
-    return LIBAVRDUDE_SOFTFAIL;
-
   // Use pgm->write_byte() if not EEPROM/flash or no paged access
   if(!avr_has_paged_access(pgm, mem))
     return fallback_write_byte(pgm, p, mem, addr, data);
@@ -650,6 +647,12 @@ int avr_write_byte_cached(const PROGRAMMER *pgm, const AVRPART *p, const AVRMEM
   if(loadCachePage(cp, pgm, p, mem, addr, cacheaddr, 0) < 0)
     return LIBAVRDUDE_GENERAL_FAILURE;
 
+  if(cp->cont[cacheaddr] == data)
+    return LIBAVRDUDE_SUCCESS;
+
+  if(pgm->readonly && pgm->readonly(pgm, p, mem, addr))
+    return LIBAVRDUDE_SOFTFAIL;
+
   cp->cont[cacheaddr] = data;
 
   return LIBAVRDUDE_SUCCESS;