Index: docs/kernel/index.xml
===================================================================
RCS file: /cvsroot/htdocs/docs/kernel/index.xml,v
retrieving revision 1.5
diff -u -p -r1.5 index.xml
--- docs/kernel/index.xml	5 Mar 2015 08:45:30 -0000	1.5
+++ docs/kernel/index.xml	23 Jun 2015 06:45:26 -0000
@@ -791,6 +791,35 @@ sd*             at scsibus? target ? lun
 	  Plug something in and type <code>continue</code>. 
 	</listitem>
       </itemizedlist>
+
+      <para>
+        USB debugging code has been changed in NetBSD 7.99 and later. The
+        changes mean that the core and host controller debug output
+        can be controlled by &man.sysctl.8; and read using &man.vmstat.1;.
+      </para>
+
+      <para>
+        Device drivers are being converted to this new method.
+      </para>
+
+      <itemizedlist>
+        <listitem>
+	  Compile a kernel with <code>USB_DEBUG</code> and/or
+          <code>[EOUX]HCI_DEBUG</code> defined.  Each device driver has
+          its own define.  The host controller and device defines implicitly
+          define <code>USB_DEBUG</code>.
+	</listitem>
+	<listitem>
+	  Boot the kernel and using sysctl(8) set the hw.usb.debug variable
+          to a non-zero value (higher values give more output).  Other variables
+          that can be set are hw.[eoux]hci.debug.
+	</listitem>
+	<listitem>
+	  Plug something in and use <code>vmstat -u usbhist</code> to dump
+          the debug output. 
+	</listitem>
+      </itemizedlist>
+
     </sect3>
 
     <sect3 id="new_pnp_device">