[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>

3 files changed, 110 insertions, 57 deletions

diff --git a/net/tipc/core.h b/net/tipc/core.h
index 762aac2572be..47504ec15d89 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 @@ void tipc_dump(struct print_buf*,const char *fmt, ...);
  * 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 @@ void tipc_dump(struct print_buf*,const char *fmt, ...);
 #endif
 
 #ifndef DBG_OUTPUT
-#define DBG_OUTPUT NULL
+#define DBG_OUTPUT TIPC_NULL
 #endif
 
 #else
@@ -136,7 +136,7 @@ void tipc_dump(struct print_buf*,const char *fmt, ...);
 #define TIPC_OUTPUT TIPC_CONS
 
 #undef  DBG_OUTPUT
-#define DBG_OUTPUT NULL
+#define DBG_OUTPUT TIPC_NULL
 
 #endif                    
 
diff --git a/net/tipc/dbg.c b/net/tipc/dbg.c
index 55130655e1ed..d8af4c28695d 100644
--- a/net/tipc/dbg.c
+++ b/net/tipc/dbg.c
@@ -1,8 +1,8 @@
 /*
- * net/tipc/dbg.c: TIPC print buffer routines for debuggign
+ * net/tipc/dbg.c: TIPC print buffer routines for debugging
  * 
  * Copyright (c) 1996-2006, Ericsson AB
- * Copyright (c) 2005, Wind River Systems
+ * Copyright (c) 2005-2006, Wind River Systems
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -38,11 +38,12 @@
 #include "config.h"
 #include "dbg.h"
 
-#define MAX_STRING 512
-
-static char print_string[MAX_STRING];
+static char print_string[TIPC_PB_MAX_STR];
 static DEFINE_SPINLOCK(print_lock);
 
+static struct print_buf null_buf = { NULL, 0, NULL, NULL };
+struct print_buf *TIPC_NULL = &null_buf;
+
 static struct print_buf cons_buf = { NULL, 0, NULL, NULL };
 struct print_buf *TIPC_CONS = &cons_buf;
 
@@ -62,68 +63,83 @@ struct print_buf *TIPC_LOG = &log_buf;
 /*
  * Locking policy when using print buffers.
  *
- * 1) Routines of the form printbuf_XXX() rely on the caller to prevent
- *    simultaneous use of the print buffer(s) being manipulated.
- * 2) tipc_printf() uses 'print_lock' to prevent simultaneous use of
- *    'print_string' and to protect its print buffer(s).
- * 3) TIPC_TEE() uses 'print_lock' to protect its print buffer(s).
- * 4) Routines of the form log_XXX() uses 'print_lock' to protect TIPC_LOG.
+ * The following routines use 'print_lock' for protection:
+ * 1) tipc_printf()  - to protect its print buffer(s) and 'print_string'
+ * 2) TIPC_TEE()     - to protect its print buffer(s)
+ * 3) tipc_dump()    - to protect its print buffer(s) and 'print_string'
+ * 4) tipc_log_XXX() - to protect TIPC_LOG
+ *
+ * All routines of the form tipc_printbuf_XXX() rely on the caller to prevent
+ * simultaneous use of the print buffer(s) being manipulated.
  */
 
 /**
  * tipc_printbuf_init - initialize print buffer to empty
+ * @pb: pointer to print buffer structure
+ * @raw: pointer to character array used by print buffer
+ * @size: size of character array
+ *
+ * Makes the print buffer a null device that discards anything written to it
+ * if the character array is too small (or absent).
  */
 
-void tipc_printbuf_init(struct print_buf *pb, char *raw, u32 sz)
+void tipc_printbuf_init(struct print_buf *pb, char *raw, u32 size)
 {
-        if (!pb || !raw || (sz < (MAX_STRING + 1)))
-                return;
-
-        pb->crs = pb->buf = raw;
-        pb->size = sz;
+        pb->buf = raw;
+        pb->crs = raw;
+        pb->size = size;
         pb->next = NULL;
-        pb->buf[0] = 0;
-        pb->buf[sz-1] = ~0;
+
+        if (size < TIPC_PB_MIN_SIZE) {
+                pb->buf = NULL;
+        } else if (raw) {
+                pb->buf[0] = 0;
+                pb->buf[size-1] = ~0;
+        }
 }
 
 /**
  * tipc_printbuf_reset - reinitialize print buffer to empty state
+ * @pb: pointer to print buffer structure
  */
 
 void tipc_printbuf_reset(struct print_buf *pb)
 {
-        if (pb && pb->buf)
-                tipc_printbuf_init(pb, pb->buf, pb->size);
+        tipc_printbuf_init(pb, pb->buf, pb->size);
 }
 
 /**
  * tipc_printbuf_empty - test if print buffer is in empty state
+ * @pb: pointer to print buffer structure
+ *
+ * Returns non-zero if print buffer is empty.
  */
 
 int tipc_printbuf_empty(struct print_buf *pb)
 {
-        return (!pb || !pb->buf || (pb->crs == pb->buf));
+        return (!pb->buf || (pb->crs == pb->buf));
 }
 
 /**
  * tipc_printbuf_validate - check for print buffer overflow
+ * @pb: pointer to print buffer structure
  * 
  * Verifies that a print buffer has captured all data written to it. 
  * If data has been lost, linearize buffer and prepend an error message
  * 
- * Returns length of print buffer data string (including trailing NULL)
+ * Returns length of print buffer data string (including trailing NUL)
  */
 
 int tipc_printbuf_validate(struct print_buf *pb)
 {
-        char *err = "             *** PRINT BUFFER WRAPPED AROUND ***\n";
+        char *err = "\n\n*** PRINT BUFFER OVERFLOW ***\n\n";
         char *cp_buf;
         struct print_buf cb;
 
-        if (!pb || !pb->buf)
+        if (!pb->buf)
                 return 0;
 
-        if (pb->buf[pb->size - 1] == '\0') {
+        if (pb->buf[pb->size - 1] == 0) {
                 cp_buf = kmalloc(pb->size, GFP_ATOMIC);
                 if (cp_buf != NULL){
                         tipc_printbuf_init(&cb, cp_buf, pb->size);
@@ -141,6 +157,8 @@ int tipc_printbuf_validate(struct print_buf *pb)
 
 /**
  * tipc_printbuf_move - move print buffer contents to another print buffer
+ * @pb_to: pointer to destination print buffer structure
+ * @pb_from: pointer to source print buffer structure
  * 
  * Current contents of destination print buffer (if any) are discarded.
  * Source print buffer becomes empty if a successful move occurs.
@@ -152,21 +170,22 @@ void tipc_printbuf_move(struct print_buf *pb_to, struct print_buf *pb_from)
 
         /* Handle the cases where contents can't be moved */
 
-        if (!pb_to || !pb_to->buf)
+        if (!pb_to->buf)
                 return;
 
-        if (!pb_from || !pb_from->buf) {
+        if (!pb_from->buf) {
                 tipc_printbuf_reset(pb_to);
                 return;
         }
 
         if (pb_to->size < pb_from->size) {
                 tipc_printbuf_reset(pb_to);
-                tipc_printf(pb_to, "*** PRINT BUFFER OVERFLOW ***");
+                tipc_printf(pb_to, "*** PRINT BUFFER MOVE ERROR ***");
                 return;
         }
 
         /* Copy data from char after cursor to end (if used) */
+
         len = pb_from->buf + pb_from->size - pb_from->crs - 2;
         if ((pb_from->buf[pb_from->size-1] == 0) && (len > 0)) {
                 strcpy(pb_to->buf, pb_from->crs + 1);
@@ -175,6 +194,7 @@ void tipc_printbuf_move(struct print_buf *pb_to, struct print_buf *pb_from)
                 pb_to->crs = pb_to->buf;
 
         /* Copy data from start to cursor (always) */
+
         len = pb_from->crs - pb_from->buf;
         strcpy(pb_to->crs, pb_from->buf);
         pb_to->crs += len;
@@ -184,6 +204,8 @@ void tipc_printbuf_move(struct print_buf *pb_to, struct print_buf *pb_from)
 
 /**
  * tipc_printf - append formatted output to print buffer chain
+ * @pb: pointer to chain of print buffers (may be NULL)
+ * @fmt: formatted info to be printed
  */
 
 void tipc_printf(struct print_buf *pb, const char *fmt, ...)
@@ -195,8 +217,8 @@ void tipc_printf(struct print_buf *pb, const char *fmt, ...)
 
         spin_lock_bh(&print_lock);
         FORMAT(print_string, chars_to_add, fmt);
-        if (chars_to_add >= MAX_STRING)
-                strcpy(print_string, "*** STRING TOO LONG ***");
+        if (chars_to_add >= TIPC_PB_MAX_STR)
+                strcpy(print_string, "*** PRINT BUFFER STRING TOO LONG ***");
 
         while (pb) {
                 if (pb == TIPC_CONS)
@@ -206,6 +228,10 @@ void tipc_printf(struct print_buf *pb, const char *fmt, ...)
                         if (chars_to_add <= chars_left) {
                                 strcpy(pb->crs, print_string);
                                 pb->crs += chars_to_add;
+                        } else if (chars_to_add >= (pb->size - 1)) {
+                                strcpy(pb->buf, print_string + chars_to_add + 1
+                                       - pb->size);
+                                pb->crs = pb->buf + pb->size - 1;
                         } else {
                                 strcpy(pb->buf, print_string + chars_left);
                                 save_char = print_string[chars_left];
@@ -224,6 +250,10 @@ void tipc_printf(struct print_buf *pb, const char *fmt, ...)
 
 /**
  * TIPC_TEE - perform next output operation on both print buffers  
+ * @b0: pointer to chain of print buffers (may be NULL)
+ * @b1: pointer to print buffer to add to chain
+ *
+ * Returns pointer to print buffer chain.
  */
 
 struct print_buf *TIPC_TEE(struct print_buf *b0, struct print_buf *b1)
@@ -232,8 +262,6 @@ struct print_buf *TIPC_TEE(struct print_buf *b0, struct print_buf *b1)
 
         if (!b0 || (b0 == b1))
                 return b1;
-        if (!b1)
-                return b0;
 
         spin_lock_bh(&print_lock);
         while (pb->next) {
@@ -256,7 +284,7 @@ static void print_to_console(char *crs, int len)
         int rest = len;
 
         while (rest > 0) {
-                int sz = rest < MAX_STRING ? rest : MAX_STRING;
+                int sz = rest < TIPC_PB_MAX_STR ? rest : TIPC_PB_MAX_STR;
                 char c = crs[sz];
 
                 crs[sz] = 0;
@@ -275,36 +303,48 @@ static void printbuf_dump(struct print_buf *pb)
 {
         int len;
 
+        if (!pb->buf) {
+                printk("*** PRINT BUFFER NOT ALLOCATED ***");
+                return;
+        }
+
         /* Dump print buffer from char after cursor to end (if used) */
+
         len = pb->buf + pb->size - pb->crs - 2;
         if ((pb->buf[pb->size - 1] == 0) && (len > 0))
                 print_to_console(pb->crs + 1, len);
 
         /* Dump print buffer from start to cursor (always) */
+
         len = pb->crs - pb->buf;
         print_to_console(pb->buf, len);
 }
 
 /**
  * tipc_dump - dump non-console print buffer(s) to console
+ * @pb: pointer to chain of print buffers
  */
 
 void tipc_dump(struct print_buf *pb, const char *fmt, ...)
 {
+        struct print_buf *pb_next;
         int len;
 
         spin_lock_bh(&print_lock);
-        FORMAT(TIPC_CONS->buf, len, fmt);
-        printk(TIPC_CONS->buf);
+        FORMAT(print_string, len, fmt);
+        printk(print_string);
 
         for (; pb; pb = pb->next) {
-                if (pb == TIPC_CONS)
-                        continue;
-                printk("\n---- Start of dump,%s log ----\n\n", 
-                       (pb == TIPC_LOG) ? "global" : "local");
-                printbuf_dump(pb);
-                tipc_printbuf_reset(pb);
-                printk("\n-------- End of dump --------\n");
+                if (pb != TIPC_CONS) {
+                        printk("\n---- Start of %s log dump ----\n\n",
+                               (pb == TIPC_LOG) ? "global" : "local");
+                        printbuf_dump(pb);
+                        tipc_printbuf_reset(pb);
+                        printk("\n---- End of dump ----\n");
+                }
+                pb_next = pb->next;
+                pb->next = NULL;
+                pb = pb_next;
         }
         spin_unlock_bh(&print_lock);
 }
@@ -324,7 +364,8 @@ void tipc_log_stop(void)
 }
 
 /**
- * tipc_log_reinit - set TIPC log print buffer to specified size
+ * tipc_log_reinit - (re)initialize TIPC log print buffer
+ * @log_size: print buffer size to use
  */
 
 void tipc_log_reinit(int log_size)
@@ -332,10 +373,11 @@ void tipc_log_reinit(int log_size)
         tipc_log_stop();
 
         if (log_size) {
-                if (log_size <= MAX_STRING)
-                        log_size = MAX_STRING + 1;
+                if (log_size < TIPC_PB_MIN_SIZE)
+                        log_size = TIPC_PB_MIN_SIZE;
                 spin_lock_bh(&print_lock);
-                tipc_printbuf_init(TIPC_LOG, kmalloc(log_size, GFP_ATOMIC), log_size);
+                tipc_printbuf_init(TIPC_LOG, kmalloc(log_size, GFP_ATOMIC),
+                                   log_size);
                 spin_unlock_bh(&print_lock);
         }
 }
diff --git a/net/tipc/dbg.h b/net/tipc/dbg.h
index 227f050d2a52..467c0bc78a79 100644
--- a/net/tipc/dbg.h
+++ b/net/tipc/dbg.h
@@ -2,7 +2,7 @@
  * net/tipc/dbg.h: Include file for TIPC print buffer routines
  * 
  * Copyright (c) 1997-2006, Ericsson AB
- * Copyright (c) 2005, Wind River Systems
+ * Copyright (c) 2005-2006, Wind River Systems
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -37,6 +37,14 @@
 #ifndef _TIPC_DBG_H
 #define _TIPC_DBG_H
 
+/**
+ * struct print_buf - TIPC print buffer structure
+ * @buf: pointer to character array containing print buffer contents
+ * @size: size of character array
+ * @crs: pointer to first unused space in character array (i.e. final NUL)
+ * @next: used to link print buffers when printing to more than one at a time
+ */
+
 struct print_buf {
         char *buf;
         u32 size;
@@ -44,7 +52,10 @@ struct print_buf {
         struct print_buf *next;
 };
 
-void tipc_printbuf_init(struct print_buf *pb, char *buf, u32 sz);
+#define TIPC_PB_MIN_SIZE 64     /* minimum size for a print buffer's array */
+#define TIPC_PB_MAX_STR 512     /* max printable string (with trailing NUL) */
+
+void tipc_printbuf_init(struct print_buf *pb, char *buf, u32 size);
 void tipc_printbuf_reset(struct print_buf *pb);
 int  tipc_printbuf_empty(struct print_buf *pb);
 int  tipc_printbuf_validate(struct print_buf *pb);