cdc_acm: Fix ACM handler.

Author: zyp

orbtrace/cdc_acm.py

@@ -50,6 +50,7 @@ def elaborate(self, platform):
         interface         = self.interface
         setup             = self.interface.setup
 
+        m.d.comb += interface.claim.eq((setup.recipient == USBRequestRecipient.INTERFACE) & (setup.index == self.if_num))
         m.d.usb += self.new_request.eq(0)
 
         with m.FSM(domain = 'usb'):