usbdump: fix interval retrieval for endpoint

Signed-off-by: Peter Wu <peter@lekensteyn.nl>

1 files changed, 4 insertions, 2 deletions

diff --git a/hw/usb/dump.c b/hw/usb/dump.c
index bff9bcd601..4c6445e379 100644
--- a/hw/usb/dump.c
+++ b/hw/usb/dump.c
@@ -157,8 +157,10 @@ static uint8_t get_ep_interval(USBEndpoint *ep)
     assert(ep->ifnum < dev->ninterfaces);
     const USBDescIface *iface = dev->ifaces[ep->ifnum];
 
-    assert(ep->nr < iface->bNumEndpoints);
-    const USBDescEndpoint *uep = iface->eps + ep->nr;
+    /* EP0 is defined as the Default control pipe */
+    assert(ep->nr > 0);
+    assert(ep->nr <= iface->bNumEndpoints);
+    const USBDescEndpoint *uep = iface->eps + ep->nr - 1;
 
     return uep->bInterval;
 }