[TIPC]: Debug print buffer enhancements and fixes

This change modifies TIPC's print buffer code as follows:
1) Now supports small print buffers (min. size reduced from 512 bytes to 64)
2) Now uses TIPC_NULL print buffer structure to indicate null device
   instead of NULL pointer (this simplified error handling)
3) Fixed misuse of console buffer structure by tipc_dump()
4) Added and corrected comments in various places

Signed-off-by: Allan Stephens <allan.stephens@windriver.com>
Signed-off-by: Per Liden <per.liden@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/tipc/core.h b/net/tipc/core.h
index 762aac2..47504ec 100644
--- a/net/tipc/core.h
+++ b/net/tipc/core.h
@@ -65,7 +65,7 @@
 #define assert(i)  BUG_ON(!(i))
 
 struct tipc_msg;
-extern struct print_buf *TIPC_CONS, *TIPC_LOG;
+extern struct print_buf *TIPC_NULL, *TIPC_CONS, *TIPC_LOG;
 extern struct print_buf *TIPC_TEE(struct print_buf *, struct print_buf *);
 void tipc_msg_print(struct print_buf*,struct tipc_msg *,const char*);
 void tipc_printf(struct print_buf *, const char *fmt, ...);
@@ -94,11 +94,11 @@
  * here, or on a per .c file basis, by redefining these symbols.  The following
  * print buffer options are available:
  *
- * NULL				: Output to null print buffer (i.e. print nowhere)
- * TIPC_CONS			: Output to system console
- * TIPC_LOG			: Output to TIPC log buffer 
- * &buf				: Output to user-defined buffer (struct print_buf *)
- * TIPC_TEE(&buf_a,&buf_b)	: Output to two print buffers (eg. TIPC_TEE(TIPC_CONS,TIPC_LOG) )
+ * TIPC_NULL		   : null buffer (i.e. print nowhere)
+ * TIPC_CONS		   : system console
+ * TIPC_LOG		   : TIPC log buffer
+ * &buf			   : user-defined buffer (struct print_buf *)
+ * TIPC_TEE(&buf_a,&buf_b) : list of buffers (eg. TIPC_TEE(TIPC_CONS,TIPC_LOG))
  */
 
 #ifndef TIPC_OUTPUT
@@ -106,7 +106,7 @@
 #endif
 
 #ifndef DBG_OUTPUT
-#define DBG_OUTPUT NULL
+#define DBG_OUTPUT TIPC_NULL
 #endif
 
 #else
@@ -136,7 +136,7 @@
 #define TIPC_OUTPUT TIPC_CONS
 
 #undef  DBG_OUTPUT
-#define DBG_OUTPUT NULL
+#define DBG_OUTPUT TIPC_NULL
 
 #endif