Add support for alternate interface settings

facedancer/configuration.py

@@ -64,21 +64,22 @@ def from_binary_descriptor(cls, data):
         descriptor_type, total_length, num_interfaces, index, string_index, \
             attributes, max_power = struct.unpack_from('<xBHBBBBB', data[0:length])
 
-        # Extract the subordinate descriptors, and parse them.
-        interfaces = cls._parse_subordinate_descriptors(data[length:total_length])
-
-        # TODO _parse_subordinate_descriptors should handle this
-        interfaces = {interface.number:interface for interface in interfaces}
-
-        return cls(
+        configuration = cls(
             number=index,
             configuration_string=string_index,
             max_power=max_power,
             self_powered=(attributes >> 6) & 1,
             supports_remote_wakeup=(attributes >> 5) & 1,
-            interfaces=interfaces,
         )
 
+        # Extract the subordinate descriptors, and parse them.
+        interfaces = cls._parse_subordinate_descriptors(data[length:total_length])
+
+        for interface in interfaces:
+            configuration.add_interface(interface)
+
+        return configuration
+
 
     @classmethod
     def _parse_subordinate_descriptors(cls, data):
@@ -144,7 +145,7 @@ def get_device(self):
 
     def add_interface(self, interface: USBInterface):
         """ Adds an interface to the configuration. """
-        self.interfaces[interface.number] = interface
+        self.interfaces[interface.get_identifier()] = interface
         interface.parent = self
 
 
@@ -157,7 +158,7 @@ def get_endpoint(self, number: int, direction: USBDirection) -> USBEndpoint:
         """
 
         # Search each of our interfaces for the relevant endpoint.
-        for interface in self.interfaces.values():
+        for interface in self.active_interfaces.values():
             endpoint = interface.get_endpoint(number, direction)
             if endpoint is not None:
                 return endpoint
@@ -184,7 +185,7 @@ def handle_data_received(self, endpoint: USBEndpoint, data: bytes):
             data     : The raw bytes received on the relevant endpoint.
         """
 
-        for interface in self.interfaces.values():
+        for interface in self.active_interfaces.values():
             if interface.has_endpoint(endpoint.number, direction=USBDirection.OUT):
                 interface.handle_data_received(endpoint, data)
                 return
@@ -204,7 +205,7 @@ def handle_data_requested(self, endpoint: USBEndpoint):
             endpoint : The endpoint on which the host requested data.
         """
 
-        for interface in self.interfaces.values():
+        for interface in self.active_interfaces.values():
             if interface.has_endpoint(endpoint.number, direction=USBDirection.IN):
                 interface.handle_data_requested(endpoint)
                 return
@@ -223,7 +224,7 @@ def handle_buffer_empty(self, endpoint: USBEndpoint):
         This function is called only once per buffer.
         """
 
-        for interface in self.interfaces.values():
+        for interface in self.active_interfaces.values():
             if interface.has_endpoint(endpoint.number, direction=USBDirection.IN):
                 interface.handle_buffer_empty(endpoint)
                 return
@@ -246,7 +247,7 @@ def get_descriptor(self) -> bytes:
         # FIXME: use construct
 
         # All all subordinate descriptors together to create a big subordinate descriptor.
-        interfaces = sorted(self.interfaces.values(), key=lambda item: item.number)
+        interfaces = sorted(self.interfaces.values(), key=lambda item: item.get_identifier())
         for interface in interfaces:
             interface_descriptors += interface.get_descriptor()
 

facedancer/device.py

@@ -887,6 +887,15 @@ def handle_set_configuration_request(self, request):
         else:
             try:
                 self.configuration = self.configurations[request.value]
+
+                # On a configuration change, all interfaces revert
+                # to alternate setting 0.
+                self.configuration.active_interfaces = {
+                    interface.number: interface
+                        for interface in self.configuration.get_interfaces()
+                            if interface.alternate == 0
+                }
+
                 request.acknowledge()
             except KeyError:
                 request.stall()
@@ -902,11 +911,13 @@ def handle_get_interface_request(self, request):
         """ Handle GET_INTERFACE requests; per USB2 [9.4.4] """
         log.debug("received GET_INTERFACE request")
 
-        # TODO: support alternate interfaces.
-        # Since we don't support alternate interfaces [yet], we'll always
-        # indicate use of interface zero.
-        if self.configuration and (request.index_low in self.configuration.interfaces):
-            request.reply(b'\x00')
+        if self.configuration:
+            try:
+                number = request.index_low
+                interface = self.configuration.active_interfaces[number]
+                request.reply(bytes([interface.alternate]))
+            except KeyError:
+                request.stall()
         else:
             request.stall()
 
@@ -917,10 +928,17 @@ def handle_set_interface_request(self, request):
         """ Handle SET_INTERFACE requests; per USB2 [9.4.10] """
         log.debug(f"f{self.name} received SET_INTERFACE request")
 
-        # We don't support alternate interface settings; so ACK
-        # alternate setting zero, and stall all others.
-        if request.value == 0:
-            request.acknowledge()
+        if self.configuration:
+            try:
+                # Find this alternate setting and switch to it.
+                number = request.index_low
+                alternate = request.value
+                identifier = (number, alternate)
+                interface = self.configuration.interfaces[identifier]
+                self.configuration.active_interfaces[number] = interface
+                request.acknowledge()
+            except KeyError:
+                request.stall()
         else:
             request.stall()
 

facedancer/interface.py

@@ -243,17 +243,23 @@ def get_descriptor(self) -> bytes:
     # Alternate interface support.
     #
 
-    # TODO: support these!
-
     @standard_request_handler(number=USBStandardRequests.SET_INTERFACE)
     @to_this_interface
     def handle_set_interface_request(self, request: USBControlRequest):
         """ Handle SET_INTERFACE requests; per USB2 [9.4.10] """
         log.debug(f"f{self.name} received SET_INTERFACE request")
-        # We don't support alternate interface settings; so ACK
-        # alternate setting zero, and stall all others.
-        if request.value == 0:
-            request.acknowledge()
+
+        if self.parent:
+            try:
+                # Find this alternate setting and switch to it.
+                number = request.index_low
+                alternate = request.value
+                identifier = (number, alternate)
+                interface = self.parent.interfaces[identifier]
+                self.parent.active_interfaces[number] = interface
+                request.acknowledge()
+            except KeyError:
+                request.stall()
         else:
             request.stall()
 
@@ -262,8 +268,17 @@ def handle_set_interface_request(self, request: USBControlRequest):
     # Automatic instantiation support.
     #
 
-    def get_identifier(self) -> int:
-        return self.number
+    def get_identifier(self) -> (int, int):
+        return (self.number, self.alternate)
+
+
+    # Although we identify interfaces by (number, alternate), this helper
+    # is called from the request handling code, where we only want to
+    # match by interface number. The correct alternate interface should have
+    # been selected earlier in the request handling process.
+    def matches_identifier(self, other: int) -> bool:
+        return (other == self.number)
+
 
     #
     # Request handler functions.