USB: switch struct urb to use a kref instead of it's own atomic_t

drivers/usb/core/urb.c

@@ -13,6 +13,14 @@
 #include <linux/usb.h>
 #include "hcd.h"
 
+#define to_urb(d) container_of(d, struct urb, kref)
+
+static void urb_destroy(struct kref *kref)
+{
+	struct urb *urb = to_urb(kref);
+	kfree(urb);
+}
+
 /**
  * usb_init_urb - initializes a urb so that it can be used by a USB driver
  * @urb: pointer to the urb to initialize
@@ -31,7 +39,7 @@ void usb_init_urb(struct urb *urb)
 {
 	if (urb) {
 		memset(urb, 0, sizeof(*urb));
-		urb->count = (atomic_t)ATOMIC_INIT(1);
+		kref_init(&urb->kref, urb_destroy);
 		spin_lock_init(&urb->lock);
 	}
 }
@@ -80,8 +88,7 @@ struct urb *usb_alloc_urb(int iso_packets, int mem_flags)
 void usb_free_urb(struct urb *urb)
 {
 	if (urb)
-		if (atomic_dec_and_test(&urb->count))
-			kfree(urb);
+		kref_put(&urb->kref);
 }
 
 /**
@@ -96,11 +103,9 @@ void usb_free_urb(struct urb *urb)
  */
 struct urb * usb_get_urb(struct urb *urb)
 {
-	if (urb) {
-		atomic_inc(&urb->count);
+	if (urb)
+		kref_get(&urb->kref);
 	return urb;
-	} else
-		return NULL;
 }
 		
 		

include/linux/usb.h

@@ -14,6 +14,7 @@
 #include <linux/delay.h>	/* for mdelay() */
 #include <linux/interrupt.h>	/* for in_interrupt() */
 #include <linux/list.h>		/* for struct list_head */
+#include <linux/kref.h>		/* for struct kref */
 #include <linux/device.h>	/* for struct device */
 #include <linux/fs.h>		/* for struct file_operations */
 #include <linux/completion.h>	/* for struct completion */
@@ -731,8 +732,8 @@ typedef void (*usb_complete_t)(struct urb *, struct pt_regs *);
 struct urb
 {
 	/* private, usb core and host controller only fields in the urb */
+	struct kref kref;		/* reference count of the URB */
 	spinlock_t lock;		/* lock for the URB */
-	atomic_t count;			/* reference count of the URB */
 	void *hcpriv;			/* private data for host controller */
 	struct list_head urb_list;	/* list pointer to all active urbs */
 	int bandwidth;			/* bandwidth for INT/ISO request */