From ee25a62df6df4bd268f469acaba2a832c28611dd Mon Sep 17 00:00:00 2001
From: Stefan Rueger <stefan.rueger@urclocks.com>
Date: Sat, 19 Nov 2022 23:09:18 +0000
Subject: [PATCH] Emulate chip erase in terminal when pgm->chip_erase() soft
 fails

---
 src/main.c    |  5 ++++-
 src/term.c    | 41 ++++++++++++++++++++++++++++++++++++++++-
 src/urclock.c |  3 +--
 3 files changed, 45 insertions(+), 4 deletions(-)

diff --git a/src/main.c b/src/main.c
index 40f40c36..3e87019f 100644
--- a/src/main.c
+++ b/src/main.c
@@ -1395,7 +1395,10 @@ int main(int argc, char * argv [])
     } else {
       pmsg_info("erasing chip\n");
       exitrc = avr_chip_erase(pgm, p);
-      if(exitrc)
+      if(exitrc == LIBAVRDUDE_SOFTFAIL) {
+        imsg_info("delaying chip erase until first -U upload to flash\n");
+        exitrc = 1;
+      } else if(exitrc)
         goto main_exit;
     }
   }
diff --git a/src/term.c b/src/term.c
index edd6c8e3..78f37216 100644
--- a/src/term.c
+++ b/src/term.c
@@ -755,8 +755,47 @@ static int cmd_send(PROGRAMMER *pgm, AVRPART *p, int argc, char *argv[]) {
 
 static int cmd_erase(PROGRAMMER *pgm, AVRPART *p, int argc, char *argv[]) {
   term_out("erasing chip ...\n");
+
   // Erase chip and clear cache
-  pgm->chip_erase_cached(pgm, p);
+  int rc = pgm->chip_erase_cached(pgm, p);
+
+  if(rc == LIBAVRDUDE_SOFTFAIL) {
+    pmsg_info("(erase) emulating chip erase by writing 0xff to flash ");
+    AVRMEM *flm = avr_locate_mem(p, "flash");
+    if(!flm) {
+      msg_error("but flash not defined for part %s?\n", p->desc);
+      return -1;
+    }
+    int addr, beg = 0, end = flm->size-1;
+    if(pgm->readonly) {
+      for(addr=beg; addr < flm->size; addr++)
+        if(!pgm->readonly(pgm, p, flm, addr)) {
+          beg = addr;
+          break;
+        }
+      if(addr >= flm->size) {
+        msg_info("but all flash is write protected\n");
+        return 0;
+      }
+      for(addr=end; addr >= 0; addr--)
+        if(!pgm->readonly(pgm, p, flm, addr)) {
+          end = addr;
+          break;
+        }
+    }
+
+    msg_info("[0x%04x, 0x%04x]; undo with abort\n", beg, end);
+    for(int addr=beg; addr <= end; addr++)
+      if(!pgm->readonly || !pgm->readonly(pgm, p, flm, addr))
+        if(pgm->write_byte_cached(pgm, p, flm, addr, 0xff) == -1)
+          return -1;
+    return 0;
+  }
+
+  if(rc) {
+    pmsg_error("(erase) programmer %s failed erasing the chip\n", (char *) ldata(lfirst(pgm->id)));
+    return -1;
+  }
 
   return 0;
 }
diff --git a/src/urclock.c b/src/urclock.c
index c2e6ef70..d828c24f 100644
--- a/src/urclock.c
+++ b/src/urclock.c
@@ -1898,7 +1898,6 @@ static int urclock_chip_erase(const PROGRAMMER *pgm, const AVRPART *p) {
     (ur.urprotocol && !(ur.urfeatures & UB_CHIP_ERASE)) ||
     ur.bloptiversion || (ur.blurversion && ur.blurversion < 076)) {
 
-    pmsg_info("delaying chip erase to first -U upload to flash\n");
     // Bootloader does not implement chip erase: don't send command to bootloader
     ur.emulate_ce = 1;
     emulated = 1;
@@ -1953,7 +1952,7 @@ static int urclock_chip_erase(const PROGRAMMER *pgm, const AVRPART *p) {
     }
   }
 
-  return 0;
+  return emulated? LIBAVRDUDE_SOFTFAIL: 0;
 }