feat(ble): Always overwrite the oldest pairing

Goal is to always overwrite the oldest pairing if there are no slots available anymore. Previously the device would always after power up start overwriting at the first pairing.

epicardium/ble/bondings.c

@@ -70,6 +70,8 @@
 #define APP_DB_NVM_HDL_LIST_ID                19
 #define APP_DB_NVM_DISC_STATUS_ID             20
 
+#define APP_DB_NVM_SEQUENCE_NUMBER_ID         100
+
 /**************************************************************************************************
   Data Types
 **************************************************************************************************/
@@ -104,6 +106,8 @@ typedef struct
   /*! for ATT client */
   uint16_t    hdlList[APP_DB_HDL_LIST_LEN]; /*! Cached handle list */
   uint8_t     discStatus;                   /*! Service discovery and configuration status */
+
+  uint32_t    sequenceNumber;
 } appDbRec_t;
 
 
@@ -114,9 +118,6 @@ typedef struct
 /*! Database */
 static appDbRec_t records[APP_DB_NUM_RECS];
 
-/*! When all records are allocated use this index to determine which to overwrite */
-static appDbRec_t *pAppDbNewRec = records;
-
 /* clang-format on */
 /* Translate a pointer to a record into the filename to be used for it. */
 static int record_to_filename(appDbRec_t *record, char *buf, size_t buf_size)
@@ -129,6 +130,28 @@ static int record_to_filename(appDbRec_t *record, char *buf, size_t buf_size)
 	return ret;
 }
 
+static appDbRec_t *record_with_highest_seq_number()
+{
+	appDbRec_t *r = &records[0];
+	for (int i = 0; i < APP_DB_NUM_RECS; i++) {
+		if (records[i].sequenceNumber > r->sequenceNumber) {
+			r = &records[i];
+		}
+	}
+	return r;
+}
+
+static appDbRec_t *record_with_lowest_seq_number()
+{
+	appDbRec_t *r = &records[0];
+	for (int i = 0; i < APP_DB_NUM_RECS; i++) {
+		if (records[i].sequenceNumber < r->sequenceNumber) {
+			r = &records[i];
+		}
+	}
+	return r;
+}
+
 /* Write a TLV to a file. */
 static int write_tlv(int fd, uint32_t t, uint32_t l, void *v)
 {
@@ -218,6 +241,7 @@ static int write_bond_to_file(appDbRec_t *r, char *filename)
 	write_element(APP_DB_NVM_PEER_SIGN_CTR_ID, peerSignCounter);
 	write_element(APP_DB_NVM_HDL_LIST_ID, hdlList);
 	write_element(APP_DB_NVM_DISC_STATUS_ID, discStatus);
+	write_element(APP_DB_NVM_SEQUENCE_NUMBER_ID, sequenceNumber);
 	write_element(APP_DB_NVM_VALID_ID, valid);
 
 #undef write_element
@@ -265,6 +289,7 @@ static int read_bond_from_file(appDbRec_t *r, char *filename)
 	read_element(APP_DB_NVM_PEER_SIGN_CTR_ID, peerSignCounter);
 	read_element(APP_DB_NVM_HDL_LIST_ID, hdlList);
 	read_element(APP_DB_NVM_DISC_STATUS_ID, discStatus);
+	read_element(APP_DB_NVM_SEQUENCE_NUMBER_ID, sequenceNumber);
 	read_element(APP_DB_NVM_VALID_ID, valid);
 
 #undef read_element
@@ -337,15 +362,8 @@ appDbHdl_t AppDbNewRecord(uint8_t addrType, uint8_t *pAddr)
   /* if all records were allocated */
   if (i == 0)
   {
-    /* overwrite a record */
-    pRec = pAppDbNewRec;
-
-    /* get next record to overwrite */
-    pAppDbNewRec++;
-    if (pAppDbNewRec == &records[APP_DB_NUM_RECS])
-    {
-      pAppDbNewRec = records;
-    }
+    /* overwrite the oldest record */
+    pRec = record_with_lowest_seq_number();
   }
 
   /* initialize record */
@@ -355,6 +373,7 @@ appDbHdl_t AppDbNewRecord(uint8_t addrType, uint8_t *pAddr)
   BdaCpy(pRec->peerAddr, pAddr);
   pRec->peerAddedToRl = FALSE;
   pRec->peerRpao = FALSE;
+  pRec->sequenceNumber = record_with_highest_seq_number()->sequenceNumber + 1;
 
   return (appDbHdl_t) pRec;
 }