diff --git a/README b/README
index 51a8fb3..6985f2b 100644
--- a/README
+++ b/README
@@ -989,6 +989,12 @@ A very short type string.
 ===== /sys/bus/dahdi_spans/devices/span-N/syncsrc
 Current sync source.
 
+==== sys/bus/dahdi_spans/drivers/generic_lowlevel/master_span
+All spans in the bus are handled by a single driver. The driver has one
+non-standard attribute: master_span. printing it shows the current DAHDI
+master span writing a number to it forces setting this span as the master
+span.
+
 
 Channels Bus
 ^^^^^^^^^^^^
diff --git a/drivers/dahdi/dahdi-base.c b/drivers/dahdi/dahdi-base.c
index 5a2ec49..74d46f3 100644
--- a/drivers/dahdi/dahdi-base.c
+++ b/drivers/dahdi/dahdi-base.c
@@ -3840,6 +3840,31 @@ void dahdi_alarm_channel(struct dahdi_chan *chan, int alarms)
 	spin_unlock_irqrestore(&chan->lock, flags);
 }
 
+struct dahdi_span *get_master_span(void)
+{
+	return master_span;
+}
+
+void set_master_span(int spanno)
+{
+	struct dahdi_span *s;
+	unsigned long flags;
+	struct dahdi_span *old_master;
+
+	spin_lock_irqsave(&chan_lock, flags);
+	old_master = master_span;
+	list_for_each_entry(s, &span_list, spans_node) {
+		if (spanno == s->spanno) {
+			master_span = s;
+			break;
+		}
+	}
+	spin_unlock_irqrestore(&chan_lock, flags);
+	if ((debug & DEBUG_MAIN) && (old_master != master_span))
+		module_printk(KERN_NOTICE, "Master span is set to %d (%s)\n",
+			master_span->spanno, master_span->name);
+}
+
 static void __dahdi_find_master_span(void)
 {
 	struct dahdi_span *s;
diff --git a/drivers/dahdi/dahdi-sysfs.c b/drivers/dahdi/dahdi-sysfs.c
index 3de37d5..6b1962c 100644
--- a/drivers/dahdi/dahdi-sysfs.c
+++ b/drivers/dahdi/dahdi-sysfs.c
@@ -231,7 +231,30 @@ static struct device_attribute span_dev_attrs[] = {
 	__ATTR_NULL,
 };
 
+static ssize_t master_span_show(struct device_driver *driver, char *buf)
+{
+	struct dahdi_span *s = get_master_span();
+
+	return snprintf(buf, PAGE_SIZE, "%d\n", (s) ? s->spanno : 0);
+}
+
+static ssize_t master_span_store(struct device_driver *driver, const char *buf,
+			  size_t count)
+{
+	int spanno;
+
+	if (sscanf(buf, "%d", &spanno) != 1) {
+		module_printk(KERN_ERR, "non-numeric input '%s'\n", buf);
+		return -EINVAL;
+	}
+	set_master_span(spanno);
+	return count;
+}
+
+
 static struct driver_attribute dahdi_attrs[] = {
+	__ATTR(master_span, S_IRUGO | S_IWUSR, master_span_show,
+			master_span_store),
 	__ATTR_NULL,
 };
 
diff --git a/include/dahdi/kernel.h b/include/dahdi/kernel.h
index ac70e1a..c71e909 100644
--- a/include/dahdi/kernel.h
+++ b/include/dahdi/kernel.h
@@ -1003,6 +1003,8 @@ struct dahdi_transcoder_channel {
 };
 
 int dahdi_is_sync_master(const struct dahdi_span *span);
+struct dahdi_span *get_master_span(void);
+void set_master_span(int spanno);
 
 static inline int 
 dahdi_tc_is_built(struct dahdi_transcoder_channel *dtc) {