--- zaptel-1.4.9.2.oslec/kernel/zaptel-base.c	2008-06-16 18:09:27.719196772 +0700
+++ zaptel/kernel/zaptel-base.c	2008-06-16 17:41:30.554380521 +0700
@@ -34,6 +34,12 @@
  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. 
  */
 
+/*
+ 2008.03.28, pavel[AT]parabel.ru
+
+ Implemented: correct master arbitrage
+ Implemented: export to procfs, who is the current master for zaptel
+ */
 
 #include "zconfig.h"
 #include "../version.h"
@@ -251,7 +257,8 @@
 static sumtype *conf_sums;
 static sumtype *conf_sums_prev;
 
-static struct zt_span *master;
+static struct zt_span *master = NULL;
+static struct zt_span *pref_master = NULL;
 static struct file_operations zt_fops;
 struct file_operations *zt_transcode_fops = NULL;
 
@@ -2960,6 +2967,43 @@
 	spin_unlock_irqrestore(&chan->lock, flags);
 }
 
+static inline int __can_be_master (struct zt_span *span) {
+	if (span && !span->alarms && (span->flags & ZT_FLAG_RUNNING)) return 1;
+        return 0;
+}
+
+/*
+ 1. trying preffered master SPAN
+ 2. trying non-zero channel SPANS
+ 3. trying zero-channel SPANS (ztdummy,...)
+ */
+void zt_checkmaster (void) {
+	int x;
+	struct zt_span *dummy = NULL;
+	struct zt_span *newmaster = NULL;
+	struct zt_span *curmaster = master;
+
+	if (__can_be_master(pref_master)) {
+		newmaster = pref_master;
+	} else {
+		/* Switch to other master if current master in alarm */
+		for (x=1; x<maxspans; x++) {
+			if (__can_be_master(spans[x])) {
+				if (spans[x]->channels > 0) {
+					newmaster = spans[x];
+					break; //We're happy now.
+				} else
+					if (!dummy) dummy = spans[x];
+
+			}
+		}
+	}
+
+	master = (newmaster) ? newmaster : dummy;
+	if (master != curmaster)
+		printk("Zaptel: Master changed to %s\n", (master)? master->name: "no master");
+}
+
 void zt_alarm_notify(struct zt_span *span)
 {
 	int x;
@@ -2976,16 +3020,8 @@
 		span->lastalarms = span->alarms;
 		for (x = 0; x < span->channels; x++)
 			zt_alarm_channel(&span->chans[x], span->alarms);
-		/* Switch to other master if current master in alarm */
-		for (x=1; x<maxspans; x++) {
-			if (spans[x] && !spans[x]->alarms && (spans[x]->flags & ZT_FLAG_RUNNING)) {
-				if(master != spans[x])
-					printk("Zaptel: Master changed to %s\n", spans[x]->name);
-				master = spans[x];
-				break;
-			}
-		}
 	}
+	zt_checkmaster ();
 }
 
 #define VALID_SPAN(j) do { \
@@ -3474,6 +3510,7 @@
 				spin_unlock_irqrestore(&spans[j]->chans[x].lock, flags);
 				spans[j]->chans[x].rxhooksig = ZT_RXSIG_INITIAL;
 			}
+			zt_checkmaster ();
 		}
 		return 0;
 	case ZT_SHUTDOWN:
@@ -4950,11 +4987,9 @@
 
 	if (debug)
 		printk("Registered Span %d ('%s') with %d channels\n", span->spanno, span->name, span->channels);
-	if (!master || prefmaster) {
-		master = span;
-		if (debug)
-			printk("Span ('%s') is new master\n", span->name);
-	}
+	if (prefmaster) {
+		pref_master = span;
+ 	}
 	return 0;
 }
 
@@ -4962,7 +4997,6 @@
 {
 	int x;
 	int new_maxspans;
-	static struct zt_span *new_master;
 
 #ifdef CONFIG_PROC_FS
 	char tempfile[17];
@@ -5008,22 +5042,17 @@
 	for (x=0;x<span->channels;x++)
 		zt_chan_unreg(&span->chans[x]);
 	new_maxspans = 0;
-	new_master = master; /* FIXME: locking */
 	if (master == span)
-		new_master = NULL;
+		master = NULL;
+	if (pref_master == span)
+		pref_master = NULL;
 	for (x=1;x<ZT_MAX_SPANS;x++) {
 		if (spans[x]) {
 			new_maxspans = x+1;
-			if (!new_master)
-				new_master = spans[x];
 		}
 	}
 	maxspans = new_maxspans;
-	if (master != new_master)
-		if (debug)
-			printk("%s: Span ('%s') is new master\n", __FUNCTION__, 
-				(new_master)? new_master->name: "no master");
-	master = new_master;
+        zt_checkmaster ();
 
 	return 0;
 }