--- xnu/xnu-124.13/bsd/miscfs/devfs/devfs_tree.c
+++ xnu/xnu-344/bsd/miscfs/devfs/devfs_tree.c
@@ -126,6 +126,11 @@
 	MALLOC(devfs_hidden_mount, struct mount *, sizeof(struct mount),
 	       M_MOUNT, M_WAITOK);
 	bzero(devfs_hidden_mount,sizeof(struct mount));
+
+    /* Initialize the default IO constraints */
+    mp->mnt_maxreadcnt = mp->mnt_maxwritecnt = MAXPHYS;
+    mp->mnt_segreadcnt = mp->mnt_segwritecnt = 32;
+
 	devfs_mount(devfs_hidden_mount,"dummy",NULL,NULL,NULL);
 	dev_root->de_dnp->dn_dvm 
 	    = (struct devfsmount *)devfs_hidden_mount->mnt_data;
@@ -1046,8 +1051,6 @@
 	return error;
 }
 
-#include <sys/subr_prf.h>
-
 /*
  * Function: devfs_make_node
  *
@@ -1072,7 +1075,6 @@
 	devnode_type_t	typeinfo;
 
 	char *name, *path, buf[256]; /* XXX */
-	char * b_ptr = buf;
 	boolean_t   funnel_state;
 	int i;
 	va_list ap;
@@ -1088,9 +1090,8 @@
 		goto out;
 
 	va_start(ap, fmt);
-	prf(fmt, ap, TOSTR, (struct tty *)&b_ptr);
+	vsnprintf(buf, sizeof(buf), fmt, ap);
 	va_end(ap);
-	*b_ptr = 0;
 
 	name = NULL;
 
@@ -1147,7 +1148,6 @@
 
 	va_list ap;
 	char *p, buf[256]; /* XXX */
-	char * b_ptr = buf;
 	int i;
 	boolean_t   funnel_state;
 
@@ -1159,9 +1159,8 @@
 	}
 
 	va_start(ap, fmt);
-	prf(fmt, ap, TOSTR, (struct tty *)&b_ptr);
+	vsnprintf(buf, sizeof(buf), fmt, ap);
 	va_end(ap);
-	*b_ptr = 0;
 
 	p = NULL;