[PATCH] parport fixes (1/6)

	Current tree has all allocated ports on portlist.  However,
most of the portlist users assume that we only have announced ports
there and break badly if they happen to see the list after port driver
has created a port (parport_register_port()) but before it finishes
the setup (and calls parport_announce_port()).
	The only place that wants to see all allocated port is
parport_register_port() itself and only to pick the first unused
port number.
	We add a new list (all_ports) and put ports there when allocated;
that list is kept ordered by port->number.  Ports are placed on portlist
only by parport_announce_port().
	Gobs of shite in parport_register_port() removed, pile of races
closed...

drivers/parport/share.c

@@ -44,6 +44,10 @@ int parport_default_spintime =  DEFAULT_SPIN_TIME;
 static struct parport *portlist = NULL, *portlist_tail = NULL;
 static spinlock_t parportlist_lock = SPIN_LOCK_UNLOCKED;
 
+/* list of all allocated ports, sorted by ->number */
+static LIST_HEAD(all_ports);
+static spinlock_t full_list_lock = SPIN_LOCK_UNLOCKED;
+
 static struct parport_driver *driver_chain = NULL;
 static spinlock_t driverlist_lock = SPIN_LOCK_UNLOCKED;
 
@@ -284,6 +288,9 @@ void parport_unregister_driver (struct parport_driver *arg)
 static void free_port (struct parport *port)
 {
 	int d;
+	spin_lock(&full_list_lock);
+	list_del(&port->full_list);
+	spin_unlock(&full_list_lock);
 	for (d = 0; d < 5; d++) {
 		if (port->probe_info[d].class_name)
 			kfree (port->probe_info[d].class_name);
@@ -386,8 +393,9 @@ struct parport *parport_enumerate(void)
 struct parport *parport_register_port(unsigned long base, int irq, int dma,
 				      struct parport_operations *ops)
 {
+	struct list_head *l;
 	struct parport *tmp;
-	int portnum;
+	int num;
 	int device;
 	char *name;
 
@@ -418,6 +426,7 @@ struct parport *parport_register_port(unsigned long base, int irq, int dma,
 	init_MUTEX_LOCKED (&tmp->ieee1284.irq); /* actually a semaphore at 0 */
 	tmp->spintime = parport_default_spintime;
 	atomic_set (&tmp->ref_count, 1);
+	INIT_LIST_HEAD(&tmp->full_list);
 
 	name = kmalloc(15, GFP_KERNEL);
 	if (!name) {
@@ -427,53 +436,22 @@ struct parport *parport_register_port(unsigned long base, int irq, int dma,
 	}
 	/* Search for the lowest free parport number. */
 
-	spin_lock_irq (&parportlist_lock);
-	for (portnum = 0; ; portnum++) {
-		struct parport *itr = portlist;
-		while (itr) {
-			if (itr->number == portnum)
-				/* No good, already used. */
-				break;
-			else
-				itr = itr->next;
-		}
-
-		if (itr == NULL)
-			/* Got to the end of the list. */
+	spin_lock(&full_list_lock);
+	for (l = all_ports.next, num = 0; l != &all_ports; l = l->next, num++) {
+		struct parport *p = list_entry(l, struct parport, full_list);
+		if (p->number != num)
 			break;
 	}
+	tmp->portnum = tmp->number = num;
+	list_add_tail(&tmp->full_list, l);
+	spin_unlock(&full_list_lock);
 
 	/*
 	 * Now that the portnum is known finish doing the Init.
 	 */
-	tmp->portnum = tmp->number = portnum;
-	sprintf(name, "parport%d", portnum);
+	sprintf(name, "parport%d", tmp->portnum = tmp->number);
 	tmp->name = name;
 
-	
-	/*
-	 * Chain the entry to our list.
-	 *
-	 * This function must not run from an irq handler so we don' t need
-	 * to clear irq on the local CPU. -arca
-	 */
-
-	/* We are locked against anyone else performing alterations, but
-	 * because of parport_enumerate people can still _read_ the list
-	 * while we are changing it; so be careful..
-	 *
-	 * It's okay to have portlist_tail a little bit out of sync
-	 * since it's only used for changing the list, not for reading
-	 * from it.
-	 */
-
-	if (portlist_tail)
-		portlist_tail->next = tmp;
-	portlist_tail = tmp;
-	if (!portlist)
-		portlist = tmp;
-	spin_unlock_irq(&parportlist_lock);
-
 	for (device = 0; device < 5; device++)
 		/* assume the worst */
 		tmp->probe_info[device].class = PARPORT_CLASS_LEGACY;
@@ -497,6 +475,23 @@ struct parport *parport_register_port(unsigned long base, int irq, int dma,
 
 void parport_announce_port (struct parport *port)
 {
+
+	/* We are locked against anyone else performing alterations, but
+	 * because of parport_enumerate people can still _read_ the list
+	 * while we are changing it; so be careful..
+	 *
+	 * It's okay to have portlist_tail a little bit out of sync
+	 * since it's only used for changing the list, not for reading
+	 * from it.
+	 */
+
+	spin_lock_irq(&parportlist_lock);
+	if (portlist_tail)
+		portlist_tail->next = port;
+	portlist_tail = port;
+	if (!portlist)
+		portlist = port;
+	spin_unlock_irq(&parportlist_lock);
 #ifdef CONFIG_PARPORT_1284
 	/* Analyse the IEEE1284.3 topology of the port. */
 	if (parport_daisy_init (port) == 0) {

include/linux/parport.h

@@ -311,6 +311,8 @@ struct parport {
 
 	int spintime;
 	atomic_t ref_count;
+
+	struct list_head full_list;
 };
 
 #define DEFAULT_SPIN_TIME 500 /* us */