sys/log: Add number of entries support in logs

- Add number of entries support in logs
- Add TLV for number of entries support
- Also update log_shell and add syscfgs to support the same.
- Added support in fcb2 and cbmem for number of entries
- This makes it such that log entries are backwards and forwards
  compatible.
- Number of entries can be read using the console or newtmgr
- This is an optional feature enabled only if
  LOG_FLAGS_TLV_SUPPORT: 1 and LOG_TLV_NUM_ENTRIES: 1

sys/log/full/include/log/log.h

@@ -97,6 +97,7 @@ typedef int (*lh_append_mbuf_body_func_t)(struct log *log,
 typedef int (*lh_walk_func_t)(struct log *,
         log_walk_func_t walk_func, struct log_offset *log_offset);
 typedef int (*lh_flush_func_t)(struct log *);
+typedef uint16_t (*lh_read_entry_len_func_t)(struct log *, const void *dptr);
 #if MYNEWT_VAL(LOG_STORAGE_INFO)
 typedef int (*lh_storage_info_func_t)(struct log *, struct log_storage_info *);
 #endif
@@ -116,6 +117,7 @@ struct log_handler {
     lh_walk_func_t log_walk;
     lh_walk_func_t log_walk_sector;
     lh_flush_func_t log_flush;
+    lh_read_entry_len_func_t log_read_entry_len;
 #if MYNEWT_VAL(LOG_STORAGE_INFO)
     lh_storage_info_func_t log_storage_info;
 #endif
@@ -129,25 +131,40 @@ struct log_handler {
 /* Image hash length to be looged */
 #define LOG_IMG_HASHLEN 4
 
-/* Flags used to indicate type of data in reserved payload*/
-#define LOG_FLAGS_IMG_HASH (1 << 0)
+/* Flags used to indicate type of data in reserved payload */
+#define LOG_FLAGS_IMG_HASH    (1 << 0)
+#define LOG_FLAGS_TLV_SUPPORT (1 << 1)
+
+#define LOG_TLV_NUM_ENTRIES   (1 << 0)
 
 #if MYNEWT_VAL(LOG_VERSION) == 3
 struct log_entry_hdr {
     int64_t ue_ts;
     uint32_t ue_index;
     uint8_t ue_module;
     uint8_t ue_level;
-    uint8_t ue_etype:4;
-    uint8_t ue_flags:4;
+    uint8_t ue_etype : 4;
+    uint8_t ue_flags : 4;
     uint8_t ue_imghash[4];
-}__attribute__((__packed__));
+    uint32_t ue_num_entries;
+} __attribute__((__packed__));
+
+struct log_tlv {
+    uint8_t tag;
+    uint8_t len;
+    /* Value is of variable size appended based on len,
+     * val is logged after the tag and len are logged
+     */
+} __attribute__((__packed__));
+
 #else
 #error "Unsupported log version"
 #endif
 
 #define LOG_BASE_ENTRY_HDR_SIZE (15)
 
+#define LOG_NUM_ENTRIES_SIZE (sizeof(((struct log *)0)->l_num_entries))
+
 #define LOG_MODULE_STR(module)      log_module_get_name(module)
 
 #if MYNEWT_VAL(LOG_LEVEL) <= LOG_LEVEL_DEBUG
@@ -213,6 +230,7 @@ struct log {
 #if !MYNEWT_VAL(LOG_GLOBAL_IDX)
     uint32_t l_idx;
 #endif
+    uint32_t l_num_entries;
 #if MYNEWT_VAL(LOG_STATS)
     STATS_SECT_DECL(logs) l_stats;
 #endif
@@ -511,6 +529,14 @@ void log_printf(struct log *log, uint8_t module, uint8_t level,
 int log_read(struct log *log, const void *dptr, void *buf, uint16_t off,
         uint16_t len);
 
+/**
+ * Reads entry length from the specified log.
+ *
+ * @return                      The number of bytes of entry length; 0 on failure.
+ */
+uint16_t
+log_read_entry_len(struct log *log, const void *dptr);
+
 /**
  * @brief Reads a single log entry header.
  *
@@ -524,15 +550,37 @@ int log_read(struct log *log, const void *dptr, void *buf, uint16_t off,
  */
 int log_read_hdr(struct log *log, const void *dptr, struct log_entry_hdr *hdr);
 
+/**
+ * @brief Reads a single log entry trailer.
+ *
+ * @param log                   The log to read from.
+ * @param dptr                  Medium-specific data describing the area to
+ *                                  read from; typically obtained by a call to
+ *                                  `log_walk`.
+ * @param tlv                   tlv type
+ * @param buf                   Value buffer
+ *
+ * @return                      0 on success; nonzero on failure.
+ */
+int log_read_trailer(struct log *log, const void *dptr, uint16_t tlv, void *buf);
+
 /**
  * @brief Reads the header length
  *
  * @param hdr Ptr to the header
- * 
+ *
  * @return Length of the header
  */
-uint16_t
-log_hdr_len(const struct log_entry_hdr *hdr);
+uint16_t log_hdr_len(const struct log_entry_hdr *hdr);
+
+/**
+ * @brief Reads the trailer length
+ *
+ * @param hdr Ptr to the header
+ *
+ * @return Length of the trailer
+ */
+uint16_t log_trailer_len(const struct log_entry_hdr *hdr);
 
 /**
  * @brief Reads data from the body of a log entry into a flat buffer.
@@ -725,6 +773,19 @@ log_set_rotate_notify_cb(struct log *log, log_notify_rotate_cb *cb);
 int log_set_watermark(struct log *log, uint32_t index);
 #endif
 
+/**
+ * Fill number of entries
+ *
+ * @param log Ptr to log structure
+ * @param dptr Ptr to data to be read
+ * @param hdr Ptr to the header
+ * @param offset Offset of the num of entries in the log entry
+ *
+ * @return 0 on success, non-zero on failure
+ */
+int log_fill_num_entries(struct log *log, const void *dptr,
+                         struct log_entry_hdr *hdr, uint16_t offset);
+
 /**
  * Fill log current image hash
  *
@@ -735,6 +796,29 @@ int log_set_watermark(struct log *log, uint32_t index);
 int
 log_fill_current_img_hash(struct log_entry_hdr *hdr);
 
+/**
+ * Reads the log entry's header from the specified log and log index
+ *
+ * @param log                   The log to read from.
+ * @param idx                   Index of the log entry to read header from
+ * @param out_hdr               On success, the last entry header gets written
+ *                                  here.
+ *
+ * @return                      0 on success; nonzero on failure.
+ */
+int
+log_read_hdr_by_idx(struct log *log, uint32_t idx, struct log_entry_hdr *out_hdr);
+
+/**
+ * Get number of entries in log
+ *
+ * @param log The log to get number of entries for
+ * @param idx The log index to read number of entries from
+ * @param num_entries Ptr to fill up number of entries in log
+ */
+int
+log_get_entries(struct log *log, uint32_t idx, uint32_t *entries);
+
 /* Handler exports */
 #if MYNEWT_VAL(LOG_CONSOLE)
 extern const struct log_handler log_console_handler;