>I should add that the USB 2.0 spec includes the following text (from section 
>        Test mode of a downstream facing port can only be used in
>        a well defined sequence of hub states. This sequence is
>        defined as follows:
>        1)  All enabled downstream facing ports of the hub containing
>            the port to be tested must be (selectively) suspended via
>            the SetPortFeature(PORT_SUSPEND) request.  Each downstream
>            facing port of the hub must be in the disabled,
>            disconnected, or suspended state (see Figure 11-9).
>So you can see the hub probably failed the request because a non-suspended 
>device was connected to port 3.  (And who knows what was attached to the other 
>ports -- the usbmon trace doesn't say.)
>Alan Stern

This was very helpful.

I was able to get the USB3503 to generate test packets by adding a 
SetPortFeature(PORT_SUSPEND) request to suspend the port before setting the 
PORT_TEST feature. Is there a way to tell that a device is a hub but not a root 
hub so ports on root hub ports aren't suspended prior to calling 

I tried to use hub_udev->maxchild to determine if something was a hub but this 
appears misguided since root hubs can have multiple children, nothing else in 
the usb_device structure jumped out as being directly related to a hub.

--- a/drivers/usb/misc/ehset.c
+++ b/drivers/usb/misc/ehset.c
@@ -62,6 +62,16 @@ static int ehset_probe(struct usb_interface *intf,
                                        NULL, 0, 1000);
        case TEST_PACKET_PID:
+               if(hub_udev->maxchild)
+               {
+                       ret = usb_control_msg(hub_udev, 
usb_sndctrlpipe(hub_udev, 0),
+                                               USB_REQ_SET_FEATURE, 
+                                               USB_PORT_FEAT_SUSPEND, portnum,
+                                               NULL, 0, 1000);
+                       if (ret < 0)
+                               break;
+               }
                ret = usb_control_msg(hub_udev, usb_sndctrlpipe(hub_udev, 0),
                                        USB_REQ_SET_FEATURE, USB_RT_PORT,

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