--- src/sys/kern/kern_conf.c	2006/06/20 19:56:26	1.186.2.6
+++ src/sys/kern/kern_conf.c	2006/10/30 15:43:56	1.186.2.7
@@ -125,6 +125,24 @@ dev_refthread(struct cdev *dev)
 	return (csw);
 }
 
+struct cdevsw *
+devvn_refthread(struct vnode *vp, struct cdev **devp)
+{
+	struct cdevsw *csw;
+
+	mtx_assert(&devmtx, MA_NOTOWNED);
+	csw = NULL;
+	dev_lock();
+	*devp = vp->v_rdev;
+	if (*devp != NULL) {
+		csw = (*devp)->si_devsw;
+		if (csw != NULL)
+			(*devp)->si_threadcount++;
+	}
+	dev_unlock();
+	return (csw);
+}
+
 void	
 dev_relthread(struct cdev *dev)
 {
--- src/sys/sys/conf.h	2005/09/26 14:36:54	1.222.2.3
+++ src/sys/sys/conf.h	2006/10/30 15:43:56	1.222.2.4
@@ -105,6 +105,7 @@ struct thread;
 struct uio;
 struct knote;
 struct clonedevs;
+struct vnode;
 
 /*
  * Note: d_thread_t is provided as a transition aid for those drivers
@@ -245,6 +246,7 @@ int clone_create(struct clonedevs **, st
 int	count_dev(struct cdev *_dev);
 void	destroy_dev(struct cdev *_dev);
 struct cdevsw *dev_refthread(struct cdev *_dev);
+struct cdevsw *devvn_refthread(struct vnode *vp, struct cdev **devp);
 void	dev_relthread(struct cdev *_dev);
 void	dev_depends(struct cdev *_pdev, struct cdev *_cdev);
 void	dev_ref(struct cdev *dev);