dahdi-base: Enable DAHDI to manage the reference counts for the board drivers.

Adds a struct module 'owner' member to the dahdi_span structure and updates
all the board drivers to set this member before registering the span.  This
allows the core of dahdi to maintain the reference counts on the channels
itself.

(closes issue #10601)
Reported by: Matti

git-svn-id: http://svn.asterisk.org/svn/dahdi/linux/trunk@6794 a0bf4364-ded3-4de4-8d8a-66a801d63aff

1 files changed, 40 insertions, 27 deletions

diff --git a/drivers/dahdi/dahdi-base.c b/drivers/dahdi/dahdi-base.c
index b29e645..71b2063 100644
--- a/drivers/dahdi/dahdi-base.c
+++ b/drivers/dahdi/dahdi-base.c
@@ -15,7 +15,7 @@
  * from Cisco 3620 to IBM x305 here in F1 Group
  *
  * Copyright (C) 2001 Jim Dixon / Zapata Telephony.
- * Copyright (C) 2001 - 2008 Digium, Inc.
+ * Copyright (C) 2001 - 2009 Digium, Inc.
  *
  * All rights reserved.
  *
@@ -2649,39 +2649,44 @@ static int dahdi_timer_release(struct inode *inode, struct file *file)
 static int dahdi_specchan_open(struct inode *inode, struct file *file, int unit)
 {
 	int res = 0;
+	struct dahdi_chan *const chan = chans[unit];
 
-	if (chans[unit] && chans[unit]->sig) {
+	if (chan && chan->sig) {
 		/* Make sure we're not already open, a net device, or a slave device */
-		if (chans[unit]->flags & DAHDI_FLAG_NETDEV)
+		if (chan->flags & DAHDI_FLAG_NETDEV)
 			res = -EBUSY;
-		else if (chans[unit]->master != chans[unit])
+		else if (chan->master != chan)
 			res = -EBUSY;
-		else if ((chans[unit]->sig & __DAHDI_SIG_DACS) == __DAHDI_SIG_DACS)
+		else if ((chan->sig & __DAHDI_SIG_DACS) == __DAHDI_SIG_DACS)
 			res = -EBUSY;
-		else if (!test_and_set_bit(DAHDI_FLAGBIT_OPEN, &chans[unit]->flags)) {
+		else if (!test_and_set_bit(DAHDI_FLAGBIT_OPEN, &chan->flags)) {
 			unsigned long flags;
-			res = initialize_channel(chans[unit]);
+			res = initialize_channel(chan);
 			if (res) {
 				/* Reallocbufs must have failed */
-				clear_bit(DAHDI_FLAGBIT_OPEN, &chans[unit]->flags);
+				clear_bit(DAHDI_FLAGBIT_OPEN, &chan->flags);
 				return res;
 			}
-			spin_lock_irqsave(&chans[unit]->lock, flags);
-			if (chans[unit]->flags & DAHDI_FLAG_PSEUDO)
-				chans[unit]->flags |= DAHDI_FLAG_AUDIO;
-			if (chans[unit]->span && chans[unit]->span->open) {
-				res = chans[unit]->span->open(chans[unit]);
+			spin_lock_irqsave(&chan->lock, flags);
+			if (chan->flags & DAHDI_FLAG_PSEUDO)
+				chan->flags |= DAHDI_FLAG_AUDIO;
+			if (chan->span) {
+				if (!try_module_get(chan->span->owner))
+					res = -ENXIO;
+				else if (chan->span->open)
+					res = chan->span->open(chan);
 			}
 			if (!res) {
-				chans[unit]->file = file;
-				spin_unlock_irqrestore(&chans[unit]->lock, flags);
+				chan->file = file;
+				spin_unlock_irqrestore(&chan->lock, flags);
 			} else {
-				spin_unlock_irqrestore(&chans[unit]->lock, flags);
-				close_channel(chans[unit]);
-				clear_bit(DAHDI_FLAGBIT_OPEN, &chans[unit]->flags);
+				spin_unlock_irqrestore(&chan->lock, flags);
+				close_channel(chan);
+				clear_bit(DAHDI_FLAGBIT_OPEN, &chan->flags);
 			}
-		} else
+		} else {
 			res = -EBUSY;
+		}
 	} else
 		res = -ENXIO;
 	return res;
@@ -2691,18 +2696,22 @@ static int dahdi_specchan_release(struct inode *node, struct file *file, int uni
 {
 	int res=0;
 	unsigned long flags;
+	struct dahdi_chan *const chan = chans[unit];
 
-	if (chans[unit]) {
+	if (chan) {
 		/* Chan lock protects contents against potentially non atomic accesses.
 		 * So if the pointer setting is not atomic, we should protect */
-		spin_lock_irqsave(&chans[unit]->lock, flags);
-		chans[unit]->file = NULL;
-		spin_unlock_irqrestore(&chans[unit]->lock, flags);
-		close_channel(chans[unit]);
-		if (chans[unit]->span && chans[unit]->span->close)
-			res = chans[unit]->span->close(chans[unit]);
+		spin_lock_irqsave(&chan->lock, flags);
+		chan->file = NULL;
+		spin_unlock_irqrestore(&chan->lock, flags);
+		close_channel(chan);
+		if (chan->span) {
+			if (chan->span->close)
+				res = chan->span->close(chan);
+			module_put(chan->span->owner);
+		}
 		/* The channel might be destroyed by low-level driver span->close() */
-		if(chans[unit])
+		if (chans[unit])
 			clear_bit(DAHDI_FLAGBIT_OPEN, &chans[unit]->flags);
 	} else
 		res = -ENXIO;
@@ -3851,8 +3860,10 @@ static int dahdi_ctl_ioctl(struct inode *inode, struct file *file, unsigned int
 		CHECK_VALID_SPAN(j);
 		if (spans[j]->flags & DAHDI_FLAG_RUNNING)
 			return 0;
+
 		if (spans[j]->startup)
 			res = spans[j]->startup(spans[j]);
+
 		if (!res) {
 			/* Mark as running and hangup any channels */
 			spans[j]->flags |= DAHDI_FLAG_RUNNING;
@@ -5499,6 +5510,8 @@ int dahdi_register(struct dahdi_span *span, int prefmaster)
 	if (!span)
 		return -EINVAL;
 
+	WARN_ON(!span->owner);
+
 	if (test_bit(DAHDI_FLAGBIT_REGISTERED, &span->flags)) {
 		module_printk(KERN_ERR, "Span %s already appears to be registered\n", span->name);
 		return -EBUSY;