syslog: Added separator in file logs.

drivers/syslog/Kconfig

@@ -273,6 +273,19 @@ menuconfig SYSLOG_FILE
 
 if SYSLOG_FILE
 
+config SYSLOG_FILE_SEPARATE
+	bool "Log file separation"
+	default n
+	depends on SYSLOG_FILE
+	---help---
+		If enabled, every time the file logger is re-attached, a separator
+		will be printed in the file.
+		
+		This can be useful to easily distinguish between log entries that
+		belong to different log sessions (e.g. system reboot), and to 
+		indicate that between the separated lines there may be more logs
+		that were lost.
+
 config SYSLOG_FILE_ROTATIONS
 	int "Log file rotations"
 	default 0

drivers/syslog/syslog_filechannel.c

@@ -36,6 +36,7 @@
 
 #include <nuttx/syslog/syslog.h>
 #include <nuttx/kmalloc.h>
+#include <nuttx/fs/fs.h>
 
 #include "syslog.h"
 
@@ -60,6 +61,22 @@ FAR static struct syslog_channel_s *g_syslog_file_channel;
  * Private Functions
  ****************************************************************************/
 
+#ifdef CONFIG_SYSLOG_FILE_SEPARATE
+static void log_separate(FAR const char *log_file)
+{
+  struct file fp;
+
+  if (file_open(&fp, log_file, O_WRONLY) < 0)
+    {
+      return;
+    }
+
+  file_write(&fp, "\n\n", 2);
+
+  file_close(&fp);
+}
+#endif
+
 #if CONFIG_SYSLOG_FILE_ROTATIONS > 0
 static void log_rotate(FAR const char *log_file)
 {
@@ -181,6 +198,12 @@ FAR struct syslog_channel_s *syslog_file_channel(FAR const char *devpath)
   log_rotate(devpath);
 #endif
 
+  /* Separate the old log entries. */
+
+#ifdef CONFIG_SYSLOG_FILE_SEPARATE
+  log_separate(devpath);
+#endif
+
   /* Then initialize the file interface */
 
   g_syslog_file_channel = syslog_dev_initialize(devpath, OPEN_FLAGS,