add usb_probe tool and improve compatibility (#33)

* add usb_probe tool and improve compatibility with older/non-compliant devices

* fix logic test

* add doc

README.md

@@ -9,7 +9,7 @@
 Bluetooth Stack for Apps, Emulation, Test and Experimentation
 =============================================================
 
-<img src="docs/mkdocs/src/images/logo_framed.png" alt="drawing" width="200" height="200"/>
+<img src="docs/mkdocs/src/images/logo_framed.png" alt="Logo" width="200" height="200"/>
 
 Bumble is a full-featured Bluetooth stack written entirely in Python. It supports most of the common Bluetooth Low Energy (BLE) and Bluetooth Classic (BR/EDR) protocols and profiles, including GAP, L2CAP, ATT, GATT, SMP, SDP, RFCOMM, HFP, HID and A2DP. The stack can be used with physical radios via HCI over USB, UART, or the Linux VHCI, as well as virtual radios, including the virtual Bluetooth support of the Android emulator.
 
@@ -38,12 +38,20 @@ python -m pip install ".[test,development,documentation]"
 
 ### Examples
 
-Refer to the [Example Documentation](examples/README.md) for details on the included example scripts and how to run them.
+Refer to the [Examples Documentation](examples/README.md) for details on the included example scripts and how to run them.
 
 The complete [list of Examples](/docs/mkdocs/src/examples/index.md), and what they are designed to do is here.
 
 There are also a set of [Apps and Tools](docs/mkdocs/src/apps_and_tools/index.md) that show the utility of Bumble.
 
+### Using Bumble With a USB Dongle
+
+Bumble is easiest to use with a dedicated USB dongle.
+This is because internal Bluetooth interfaces tend to be locked down by the operating system.
+You can use the [usb_probe](/docs/mkdocs/src/apps_and_tools/usb_probe.md) tool (all platforms) or `lsusb` (Linux or macOS) to list the available USB devices on your system.
+
+See the [USB Transport](/docs/mkdocs/src/transports/usb.md) page for details on how to refer to USB devices.
+
 ## License
 
 Licensed under the [Apache 2.0](LICENSE) License.

apps/usb_probe.py

@@ -0,0 +1,157 @@
+# Copyright 2021-2022 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# -----------------------------------------------------------------------------
+# This tool lists all the USB devices, with details about each device.
+# For each device, the different possible Bumble transport strings that can
+# refer to it are listed. If the device is known to be a Bluetooth HCI device,
+# its identifier is printed in reverse colors, and the transport names in cyan color.
+# For other devices, regardless of their type, the transport names are printed
+# in red. Whether that device is actually a Bluetooth device or not depends on
+# whether it is a Bluetooth device that uses a non-standard Class, or some other
+# type of device (there's no way to tell).
+# -----------------------------------------------------------------------------
+
+# -----------------------------------------------------------------------------
+# Imports
+# -----------------------------------------------------------------------------
+import os
+import logging
+import usb1
+from colors import color
+
+
+# -----------------------------------------------------------------------------
+# Constants
+# -----------------------------------------------------------------------------
+USB_DEVICE_CLASS_WIRELESS_CONTROLLER             = 0xE0
+USB_DEVICE_SUBCLASS_RF_CONTROLLER                = 0x01
+USB_DEVICE_PROTOCOL_BLUETOOTH_PRIMARY_CONTROLLER = 0x01
+
+USB_DEVICE_CLASSES = {
+    0x00: 'Device',
+    0x01: 'Audio',
+    0x02: 'Communications and CDC Control',
+    0x03: 'Human Interface Device',
+    0x05: 'Physical',
+    0x06: 'Still Imaging',
+    0x07: 'Printer',
+    0x08: 'Mass Storage',
+    0x09: 'Hub',
+    0x0A: 'CDC Data',
+    0x0B: 'Smart Card',
+    0x0D: 'Content Security',
+    0x0E: 'Video',
+    0x0F: 'Personal Healthcare',
+    0x10: 'Audio/Video',
+    0x11: 'Billboard',
+    0x12: 'USB Type-C Bridge',
+    0x3C: 'I3C',
+    0xDC: 'Diagnostic',
+    USB_DEVICE_CLASS_WIRELESS_CONTROLLER: (
+        'Wireless Controller',
+        {
+            0x01: {
+                0x01: 'Bluetooth',
+                0x02: 'UWB',
+                0x03: 'Remote NDIS',
+                0x04: 'Bluetooth AMP'
+            }
+        }
+    ),
+    0xEF: 'Miscellaneous',
+    0xFE: 'Application Specific',
+    0xFF: 'Vendor Specific'
+}
+
+
+# -----------------------------------------------------------------------------
+def main():
+    logging.basicConfig(level = os.environ.get('BUMBLE_LOGLEVEL', 'WARNING').upper())
+
+    with usb1.USBContext() as context:
+        bluetooth_device_count = 0
+        devices = {}
+
+        for device in context.getDeviceIterator(skip_on_error=True):
+            device_class    = device.getDeviceClass()
+            device_subclass = device.getDeviceSubClass()
+            device_protocol = device.getDeviceProtocol()
+
+            device_id = (device.getVendorID(), device.getProductID())
+
+            device_is_bluetooth_hci = (
+                device_class    == USB_DEVICE_CLASS_WIRELESS_CONTROLLER and
+                device_subclass == USB_DEVICE_SUBCLASS_RF_CONTROLLER and
+                device_protocol == USB_DEVICE_PROTOCOL_BLUETOOTH_PRIMARY_CONTROLLER
+            )
+
+            device_class_details = ''
+            device_class_info    = USB_DEVICE_CLASSES.get(device_class)
+            if device_class_info is not None:
+                if type(device_class_info) is tuple:
+                    device_class = device_class_info[0]
+                    device_subclass_info = device_class_info[1].get(device_subclass)
+                    if device_subclass_info:
+                        device_class_details = f' [{device_subclass_info.get(device_protocol)}]'
+                else:
+                    device_class = device_class_info
+
+            if device_is_bluetooth_hci:
+                bluetooth_device_count += 1
+                fg_color = 'black'
+                bg_color = 'yellow'
+            else:
+                fg_color = 'yellow'
+                bg_color = 'black'
+
+            # Compute the different ways this can be referenced as a Bumble transport
+            bumble_transport_names = []
+            basic_transport_name = f'usb:{device.getVendorID():04X}:{device.getProductID():04X}'
+
+            if device_is_bluetooth_hci:
+                bumble_transport_names.append(f'usb:{bluetooth_device_count - 1}')
+
+            serial_number_collision = False
+            if device_id in devices:
+                for device_serial in devices[device_id]:
+                    if device_serial == device.getSerialNumber():
+                        serial_number_collision = True
+
+            if device_id not in devices:
+                bumble_transport_names.append(basic_transport_name)
+            else:
+                bumble_transport_names.append(f'{basic_transport_name}#{len(devices[device_id])}')
+
+            if device.getSerialNumber() and not serial_number_collision:
+                bumble_transport_names.append(f'{basic_transport_name}/{device.getSerialNumber()}')
+
+            print(color(f'ID {device.getVendorID():04X}:{device.getProductID():04X}', fg=fg_color, bg=bg_color))
+            if bumble_transport_names:
+                print(color('  Bumble Transport Names:', 'blue'), ' or '.join(color(x, 'cyan' if device_is_bluetooth_hci else 'red') for x in bumble_transport_names))
+            print(color('  Bus/Device:            ', 'green'), f'{device.getBusNumber():03}/{device.getDeviceAddress():03}')
+            if device.getSerialNumber():
+                print(color('  Serial:                ', 'green'), device.getSerialNumber())
+            print(color('  Class:                 ', 'green'), device_class)
+            print(color('  Subclass/Protocol:     ', 'green'), f'{device_subclass}/{device_protocol}{device_class_details}')
+            print(color('  Manufacturer:          ', 'green'), device.getManufacturer())
+            print(color('  Product:               ', 'green'), device.getProduct())
+            print()
+
+            devices.setdefault(device_id, []).append(device.getSerialNumber())
+
+
+# -----------------------------------------------------------------------------
+if __name__ == '__main__':
+    main()

bumble/device.py

@@ -315,6 +315,8 @@ class DeviceConfiguration:
         self.le_simultaneous_enabled  = True
         self.classic_sc_enabled       = True
         self.classic_ssp_enabled      = True
+        self.connectable              = True
+        self.discoverable             = True
         self.advertising_data = bytes(
             AdvertisingData([(AdvertisingData.COMPLETE_LOCAL_NAME, bytes(self.name, 'utf-8'))])
         )
@@ -333,6 +335,8 @@ class DeviceConfiguration:
         self.le_simultaneous_enabled  = config.get('le_simultaneous_enabled', self.le_simultaneous_enabled)
         self.classic_sc_enabled       = config.get('classic_sc_enabled', self.classic_sc_enabled)
         self.classic_ssp_enabled      = config.get('classic_ssp_enabled', self.classic_ssp_enabled)
+        self.connectable              = config.get('connectable', self.connectable)
+        self.discoverable             = config.get('discoverable', self.discoverable)
 
         # Load or synthesize an IRK
         irk = config.get('irk')
@@ -446,7 +450,8 @@ class Device(CompositeEventEmitter):
         self.command_timeout          = 10  # seconds
         self.gatt_server              = gatt_server.Server(self)
         self.sdp_server               = sdp.Server(self)
-        self.l2cap_channel_manager    = l2cap.ChannelManager()
+        self.l2cap_channel_manager    = l2cap.ChannelManager(
+            [l2cap.L2CAP_Information_Request.EXTENDED_FEATURE_FIXED_CHANNELS])
         self.advertisement_data       = {}
         self.scanning                 = False
         self.discovering              = False
@@ -454,8 +459,6 @@ class Device(CompositeEventEmitter):
         self.disconnecting            = False
         self.connections              = {}  # Connections, by connection handle
         self.classic_enabled          = False
-        self.discoverable             = False
-        self.connectable              = False
         self.inquiry_response         = None
         self.address_resolver         = None
 
@@ -476,6 +479,8 @@ class Device(CompositeEventEmitter):
         self.le_simultaneous_enabled  = config.le_simultaneous_enabled
         self.classic_ssp_enabled      = config.classic_ssp_enabled
         self.classic_sc_enabled       = config.classic_sc_enabled
+        self.discoverable             = config.discoverable
+        self.connectable              = config.connectable
 
         # If a name is passed, override the name from the config
         if name:
@@ -490,6 +495,8 @@ class Device(CompositeEventEmitter):
         # Setup SMP
         # TODO: allow using a public address
         self.smp_manager = smp.Manager(self, self.random_address)
+        self.l2cap_channel_manager.register_fixed_channel(
+            smp.SMP_CID, self.on_smp_pdu)
 
         # Register the SDP server with the L2CAP Channel Manager
         self.sdp_server.register(self.l2cap_channel_manager)
@@ -497,6 +504,7 @@ class Device(CompositeEventEmitter):
         # Add a GAP Service if requested
         if generic_access_service:
             self.gatt_server.add_service(GenericAccessService(self.name))
+        self.l2cap_channel_manager.register_fixed_channel(ATT_CID, self.on_gatt_pdu)
 
         # Forward some events
         setup_event_forwarding(self.gatt_server, self, 'characteristic_subscription')
@@ -574,11 +582,12 @@ class Device(CompositeEventEmitter):
             logger.debug(color(f'BD_ADDR: {response.return_parameters.bd_addr}', 'yellow'))
             self.public_address = response.return_parameters.bd_addr
 
+        if self.host.supports_command(HCI_WRITE_LE_HOST_SUPPORT_COMMAND):
+            await self.send_command(HCI_Write_LE_Host_Support_Command(
+                le_supported_host    = int(self.le_enabled),
+                simultaneous_le_host = int(self.le_simultaneous_enabled),
+            ))
 
-        await self.send_command(HCI_Write_LE_Host_Support_Command(
-            le_supported_host = int(self.le_enabled),
-            simultaneous_le_host = int(self.le_simultaneous_enabled),
-        ))
         if self.le_enabled:
             # Set the controller address
             await self.send_command(HCI_LE_Set_Random_Address_Command(
@@ -623,6 +632,8 @@ class Device(CompositeEventEmitter):
                 HCI_Write_Secure_Connections_Host_Support_Command(
                     secure_connections_host_support=int(self.classic_sc_enabled))
             )
+            await self.set_connectable(self.connectable)
+            await self.set_discoverable(self.discoverable)
 
         # Let the SMP manager know about the address
         # TODO: allow using a public address
@@ -1497,7 +1508,6 @@ class Device(CompositeEventEmitter):
     def on_pairing_failure(self, connection, reason):
         connection.emit('pairing_failure', reason)
 
-    @host_event_handler
     @with_connection_from_handle
     def on_gatt_pdu(self, connection, pdu):
         # Parse the L2CAP payload into an ATT PDU object
@@ -1516,7 +1526,6 @@ class Device(CompositeEventEmitter):
                 return
             connection.gatt_server.on_gatt_pdu(connection, att_pdu)
 
-    @host_event_handler
     @with_connection_from_handle
     def on_smp_pdu(self, connection, pdu):
         self.smp_manager.on_smp_pdu(connection, pdu)

bumble/host.py

@@ -56,13 +56,7 @@ class Connection:
 
     def on_acl_pdu(self, pdu):
         l2cap_pdu = L2CAP_PDU.from_bytes(pdu)
-
-        if l2cap_pdu.cid == ATT_CID:
-            self.host.on_gatt_pdu(self, l2cap_pdu.payload)
-        elif l2cap_pdu.cid == SMP_CID:
-            self.host.on_smp_pdu(self, l2cap_pdu.payload)
-        else:
-            self.host.on_l2cap_pdu(self, l2cap_pdu.cid, l2cap_pdu.payload)
+        self.host.on_l2cap_pdu(self, l2cap_pdu.cid, l2cap_pdu.payload)
 
 
 # -----------------------------------------------------------------------------
@@ -81,7 +75,7 @@ class Host(EventEmitter):
         self.hc_total_num_acl_data_packets    = HOST_HC_TOTAL_NUM_ACL_DATA_PACKETS
         self.acl_packet_queue                 = collections.deque()
         self.acl_packets_in_flight            = 0
-        self.local_version                    = None
+        self.local_version                    = HCI_VERSION_BLUETOOTH_CORE_4_0
         self.local_supported_commands         = bytes(64)
         self.local_le_features                = 0
         self.command_semaphore                = asyncio.Semaphore(1)
@@ -99,17 +93,18 @@ class Host(EventEmitter):
         await self.send_command(HCI_Reset_Command())
         self.ready = True
 
-        await self.send_command(HCI_Set_Event_Mask_Command(event_mask = bytes.fromhex('FFFFFFFFFFFFFFFF')))
-        await self.send_command(HCI_LE_Set_Event_Mask_Command(le_event_mask = bytes.fromhex('FFFFF00000000000')))
-
         response = await self.send_command(HCI_Read_Local_Supported_Commands_Command())
         if response.return_parameters.status == HCI_SUCCESS:
             self.local_supported_commands = response.return_parameters.supported_commands
         else:
             logger.warn(f'HCI_Read_Local_Supported_Commands_Command failed: {response.return_parameters.status}')
 
-        if self.supports_command(HCI_WRITE_LE_HOST_SUPPORT_COMMAND):
-            await self.send_command(HCI_Write_LE_Host_Support_Command(le_supported_host = 1, simultaneous_le_host = 0))
+        if self.supports_command(HCI_LE_READ_LOCAL_SUPPORTED_FEATURES_COMMAND):
+            response = await self.send_command(HCI_LE_Read_Local_Supported_Features_Command())
+            if response.return_parameters.status == HCI_SUCCESS:
+                self.local_le_features = struct.unpack('<Q', response.return_parameters.le_features)[0]
+            else:
+                logger.warn(f'HCI_LE_Read_Supported_Features_Command failed: {response.return_parameters.status}')
 
         if self.supports_command(HCI_READ_LOCAL_VERSION_INFORMATION_COMMAND):
             response = await self.send_command(HCI_Read_Local_Version_Information_Command())
@@ -118,32 +113,44 @@ class Host(EventEmitter):
             else:
                 logger.warn(f'HCI_Read_Local_Version_Information_Command failed: {response.return_parameters.status}')
 
+        await self.send_command(HCI_Set_Event_Mask_Command(event_mask = bytes.fromhex('FFFFFFFFFFFFFF3F')))
+
+        if self.local_version.hci_version <= HCI_VERSION_BLUETOOTH_CORE_4_0:
+            # Some older controllers don't like event masks with bits they don't understand
+            le_event_mask = bytes.fromhex('1F00000000000000')
+        else:
+            le_event_mask = bytes.fromhex('FFFFF00000000000')
+        await self.send_command(HCI_LE_Set_Event_Mask_Command(le_event_mask = le_event_mask))
+
+        if self.supports_command(HCI_READ_BUFFER_SIZE_COMMAND):
+            response = await self.send_command(HCI_Read_Buffer_Size_Command())
+            if response.return_parameters.status == HCI_SUCCESS:
+                self.hc_acl_data_packet_length     = response.return_parameters.hc_acl_data_packet_length
+                self.hc_total_num_acl_data_packets = response.return_parameters.hc_total_num_acl_data_packets
+            else:
+                logger.warn(f'HCI_Read_Buffer_Size_Command failed: {response.return_parameters.status}')
+
         if self.supports_command(HCI_LE_READ_BUFFER_SIZE_COMMAND):
             response = await self.send_command(HCI_LE_Read_Buffer_Size_Command())
             if response.return_parameters.status == HCI_SUCCESS:
-                self.hc_le_acl_data_packet_length = response.return_parameters.hc_le_acl_data_packet_length
+                self.hc_le_acl_data_packet_length     = response.return_parameters.hc_le_acl_data_packet_length
                 self.hc_total_num_le_acl_data_packets = response.return_parameters.hc_total_num_le_acl_data_packets
-                logger.debug(f'HCI LE ACL flow control: hc_le_acl_data_packet_length={response.return_parameters.hc_le_acl_data_packet_length}, hc_total_num_le_acl_data_packets={response.return_parameters.hc_total_num_le_acl_data_packets}')
             else:
                 logger.warn(f'HCI_LE_Read_Buffer_Size_Command failed: {response.return_parameters.status}')
-            if response.return_parameters.hc_le_acl_data_packet_length == 0 or response.return_parameters.hc_total_num_le_acl_data_packets == 0:
-                # Read the non-LE-specific values
-                response = await self.send_command(HCI_Read_Buffer_Size_Command())
-                if response.return_parameters.status == HCI_SUCCESS:
-                    self.hc_acl_data_packet_length        = response.return_parameters.hc_le_acl_data_packet_length
-                    self.hc_le_acl_data_packet_length     = self.hc_le_acl_data_packet_length or self.hc_acl_data_packet_length
-                    self.hc_total_num_acl_data_packets    = response.return_parameters.hc_total_num_le_acl_data_packets
-                    self.hc_total_num_le_acl_data_packets = self.hc_total_num_le_acl_data_packets or self.hc_total_num_acl_data_packets
-                    logger.debug(f'HCI LE ACL flow control: hc_le_acl_data_packet_length={self.hc_le_acl_data_packet_length}, hc_total_num_le_acl_data_packets={self.hc_total_num_le_acl_data_packets}')
-                else:
-                    logger.warn(f'HCI_Read_Buffer_Size_Command failed: {response.return_parameters.status}')
 
-        if self.supports_command(HCI_LE_READ_LOCAL_SUPPORTED_FEATURES_COMMAND):
-            response = await self.send_command(HCI_LE_Read_Local_Supported_Features_Command())
-            if response.return_parameters.status == HCI_SUCCESS:
-                self.local_le_features = struct.unpack('<Q', response.return_parameters.le_features)[0]
-            else:
-                logger.warn(f'HCI_LE_Read_Supported_Features_Command failed: {response.return_parameters.status}')
+        if response.return_parameters.hc_le_acl_data_packet_length == 0 or response.return_parameters.hc_total_num_le_acl_data_packets == 0:
+            # LE and Classic share the same values
+            self.hc_le_acl_data_packet_length     = self.hc_acl_data_packet_length
+            self.hc_total_num_le_acl_data_packets = self.hc_total_num_acl_data_packets
+
+        logger.debug(
+            f'HCI ACL flow control: hc_acl_data_packet_length={self.hc_acl_data_packet_length},'
+            f'hc_total_num_acl_data_packets={self.hc_total_num_acl_data_packets}'
+        )
+        logger.debug(
+            f'HCI LE ACL flow control: hc_le_acl_data_packet_length={self.hc_le_acl_data_packet_length},'
+            f'hc_total_num_le_acl_data_packets={self.hc_total_num_le_acl_data_packets}'
+        )
 
         self.reset_done = True
 
@@ -168,8 +175,8 @@ class Host(EventEmitter):
 
         # Wait until we can send (only one pending command at a time)
         async with self.command_semaphore:
-            assert(self.pending_command is None)
-            assert(self.pending_response is None)
+            assert self.pending_command is None
+            assert self.pending_response is None
 
             # Create a future value to hold the eventual response
             self.pending_response = asyncio.get_running_loop().create_future()
@@ -202,6 +209,7 @@ class Host(EventEmitter):
         offset = 0
         pb_flag = 0
         while bytes_remaining:
+            # TODO: support different LE/Classic lengths
             data_total_length = min(bytes_remaining, self.hc_le_acl_data_packet_length)
             acl_packet = HCI_AclDataPacket(
                 connection_handle  = connection_handle,
@@ -224,7 +232,7 @@ class Host(EventEmitter):
             logger.debug(f'{self.acl_packets_in_flight} ACL packets in flight, {len(self.acl_packet_queue)} in queue')
 
     def check_acl_packet_queue(self):
-        # Send all we can
+        # Send all we can (TODO: support different LE/Classic limits)
         while len(self.acl_packet_queue) > 0 and self.acl_packets_in_flight < self.hc_total_num_le_acl_data_packets:
             packet = self.acl_packet_queue.pop()
             self.send_hci_packet(packet)
@@ -299,12 +307,6 @@ class Host(EventEmitter):
         if connection := self.connections.get(packet.connection_handle):
             connection.on_hci_acl_data_packet(packet)
 
-    def on_gatt_pdu(self, connection, pdu):
-        self.emit('gatt_pdu', connection.handle, pdu)
-
-    def on_smp_pdu(self, connection, pdu):
-        self.emit('smp_pdu', connection.handle, pdu)
-
     def on_l2cap_pdu(self, connection, cid, pdu):
         self.emit('l2cap_pdu', connection.handle, cid, pdu)
 

bumble/l2cap.py

@@ -414,6 +414,18 @@ class L2CAP_Information_Request(L2CAP_Control_Frame):
     EXTENDED_FEATURES_SUPPORTED = 0x0002
     FIXED_CHANNELS_SUPPORTED    = 0x0003
 
+    EXTENDED_FEATURE_FLOW_MODE_CONTROL                 = 0x0001
+    EXTENDED_FEATURE_RETRANSMISSION_MODE               = 0x0002
+    EXTENDED_FEATURE_BIDIRECTIONAL_QOS                 = 0x0004
+    EXTENDED_FEATURE_ENHANCED_RETRANSMISSION_MODE      = 0x0008
+    EXTENDED_FEATURE_STREAMING_MODE                    = 0x0010
+    EXTENDED_FEATURE_FCS_OPTION                        = 0x0020
+    EXTENDED_FEATURE_EXTENDED_FLOW_SPEC                = 0x0040
+    EXTENDED_FEATURE_FIXED_CHANNELS                    = 0x0080
+    EXTENDED_FEATURE_EXTENDED_WINDOW_SIZE              = 0x0100
+    EXTENDED_FEATURE_UNICAST_CONNECTIONLESS_DATA       = 0x0200
+    EXTENDED_FEATURE_ENHANCED_CREDIT_BASE_FLOW_CONTROL = 0x0400
+
     INFO_TYPE_NAMES = {
         CONNECTIONLESS_MTU:          'CONNECTIONLESS_MTU',
         EXTENDED_FEATURES_SUPPORTED: 'EXTENDED_FEATURES_SUPPORTED',
@@ -817,11 +829,16 @@ class Channel(EventEmitter):
 
 # -----------------------------------------------------------------------------
 class ChannelManager:
-    def __init__(self):
-        self.host        = None
-        self.channels    = {}  # Channels, mapped by connection and cid
-        self.identifiers = {}  # Incrementing identifier values by connection
-        self.servers     = {}  # Servers accepting connections, by PSM
+    def __init__(self, extended_features=None, connectionless_mtu=1024):
+        self.host               = None
+        self.channels           = {}  # Channels, mapped by connection and cid
+        # Fixed channel handlers, mapped by cid
+        self.fixed_channels     = {
+            L2CAP_SIGNALING_CID: None, L2CAP_LE_SIGNALING_CID: None}
+        self.identifiers        = {}  # Incrementing identifier values by connection
+        self.servers            = {}  # Servers accepting connections, by PSM
+        self.extended_features  = [] if extended_features is None else extended_features
+        self.connectionless_mtu = connectionless_mtu
 
     def find_channel(self, connection_handle, cid):
         if connection_channels := self.channels.get(connection_handle):
@@ -840,6 +857,13 @@ class ChannelManager:
         identifier = (self.identifiers.setdefault(connection.handle, 0) + 1) % 256
         self.identifiers[connection.handle] = identifier
         return identifier
+    
+    def register_fixed_channel(self, cid, handler):
+        self.fixed_channels[cid] = handler
+    
+    def deregister_fixed_channel(self, cid):
+        if cid in self.fixed_channels:
+            del self.fixed_channels[cid]
 
     def register_server(self, psm, server):
         self.servers[psm] = server
@@ -855,6 +879,8 @@ class ChannelManager:
             control_frame = L2CAP_Control_Frame.from_bytes(pdu)
 
             self.on_control_frame(connection, cid, control_frame)
+        elif cid in self.fixed_channels:
+            self.fixed_channels[cid](connection.handle, pdu)
         else:
             if (channel := self.find_channel(connection.handle, cid)) is None:
                 logger.warn(color(f'channel not found for 0x{connection.handle:04X}:{cid}', 'red'))
@@ -999,13 +1025,13 @@ class ChannelManager:
     def on_l2cap_information_request(self, connection, cid, request):
         if request.info_type == L2CAP_Information_Request.CONNECTIONLESS_MTU:
             result = L2CAP_Information_Response.SUCCESS
-            data = struct.pack('<H', 1024)  # TODO: don't use a fixed value
+            data = self.connectionless_mtu.to_bytes(2, 'little')
         elif request.info_type == L2CAP_Information_Request.EXTENDED_FEATURES_SUPPORTED:
             result = L2CAP_Information_Response.SUCCESS
-            data = bytes.fromhex('00000000')  # TODO: don't use a fixed value
+            data = sum(self.extended_features).to_bytes(4, 'little')
         elif request.info_type == L2CAP_Information_Request.FIXED_CHANNELS_SUPPORTED:
             result = L2CAP_Information_Response.SUCCESS
-            data = bytes.fromhex('FFFFFFFFFFFFFFFF')  # TODO: don't use a fixed value
+            data = sum(1 << cid for cid in self.fixed_channels).to_bytes(8, 'little')
         else:
             result = L2CAP_Information_Request.NO_SUPPORTED
 

bumble/transport/usb.py

@@ -37,16 +37,20 @@ async def open_usb_transport(spec):
     '''
     Open a USB transport.
     The parameter string has this syntax:
-    either <index> or <vendor>:<product>[/<serial-number>]
+    either <index> or
+    <vendor>:<product> or
+    <vendor>:<product>/<serial-number>] or
+    <vendor>:<product>#<index>
     With <index> as the 0-based index to select amongst all the devices that appear
     to be supporting Bluetooth HCI (0 being the first one), or
     Where <vendor> and <product> are the vendor ID and product ID in hexadecimal. The
-    /<serial-number> suffix max be specified when more than one device with the same
-    vendor and product identifiers are present.
+    /<serial-number> suffix or #<index> suffix max be specified when more than one device with
+    the same vendor and product identifiers are present.
 
     Examples:
     0 --> the first BT USB dongle
     04b4:f901 --> the BT USB dongle with vendor=04b4 and product=f901
+    04b4:f901#2 --> the third USB device with vendor=04b4 and product=f901
     04b4:f901/00E04C239987 --> the BT USB dongle with vendor=04b4 and product=f901 and serial number 00E04C239987
     '''
 
@@ -190,7 +194,7 @@ async def open_usb_transport(spec):
         def on_packet_received(self, transfer):
             packet_type = transfer.getUserData()
             status = transfer.getStatus()
-            # logger.debug(f'<<< USB IN transfer callback: status={status} packet_type={packet_type}')
+            # logger.debug(f'<<< USB IN transfer callback: status={status} packet_type={packet_type} length={transfer.getActualLength()}')
 
             if status == usb1.TRANSFER_COMPLETED:
                 packet = bytes([packet_type]) + transfer.getBuffer()[:transfer.getActualLength()]
@@ -271,19 +275,25 @@ async def open_usb_transport(spec):
         found = None
         if ':' in spec:
             vendor_id, product_id = spec.split(':')
+            serial_number = None
+            device_index = 0
             if '/' in product_id:
                 product_id, serial_number = product_id.split('/')
-                for device in context.getDeviceIterator(skip_on_error=True):
-                    if (
-                        device.getVendorID() == int(vendor_id, 16) and
-                        device.getProductID() == int(product_id, 16) and
-                        device.getSerialNumber() == serial_number
-                    ):
+            elif '#' in product_id:
+                product_id, device_index_str = product_id.split('#')
+                device_index = int(device_index_str)
+
+            for device in context.getDeviceIterator(skip_on_error=True):
+                if (
+                    device.getVendorID() == int(vendor_id, 16) and
+                    device.getProductID() == int(product_id, 16) and
+                    (serial_number is None or device.getSerialNumber() == serial_number)
+                ):
+                    if device_index == 0:
                         found = device
                         break
-                    device.close()
-            else:
-                found = context.getByVendorIDAndProductID(int(vendor_id, 16), int(product_id, 16), skip_on_error=True)
+                    device_index -= 1
+                device.close()
         else:
             device_index = int(spec)
             for device in context.getDeviceIterator(skip_on_error=True):
@@ -305,17 +315,6 @@ async def open_usb_transport(spec):
         logger.debug(f'USB Device: {found}')
         device = found.open()
 
-        # Set the configuration if needed
-        try:
-            configuration = device.getConfiguration()
-            logger.debug(f'current configuration = {configuration}')
-        except usb1.USBError:
-            try:
-                logger.debug('setting configuration 1')
-                device.setConfiguration(1)
-            except usb1.USBError:
-                logger.debug('failed to set configuration 1')
-
         # Use the first interface
         interface = 0
 
@@ -328,6 +327,20 @@ async def open_usb_transport(spec):
             except usb1.USBError:
                 pass
 
+        # Set the configuration if needed
+        try:
+            configuration = device.getConfiguration()
+            logger.debug(f'current configuration = {configuration}')
+        except usb1.USBError:
+            configuration = 0
+
+        if configuration != 1:
+            try:
+                logger.debug('setting configuration 1')
+                device.setConfiguration(1)
+            except usb1.USBError:
+                logger.warning('failed to set configuration 1')
+
         source = UsbPacketSource(context, device)
         sink   = UsbPacketSink(device)
         return UsbTransport(context, device, interface, source, sink)

docs/mkdocs/src/apps_and_tools/usb_probe.md

@@ -0,0 +1,38 @@
+USB PROBE TOOL
+==============
+
+This tool lists all the USB devices, with details about each device.
+For each device, the different possible Bumble transport strings that can
+refer to it are listed. 
+If the device is known to be a Bluetooth HCI device, its identifier is printed 
+in reverse colors, and the transport names in cyan color.
+For other devices, regardless of their type, the transport names are printed
+in red. Whether that device is actually a Bluetooth device or not depends on
+whether it is a Bluetooth device that uses a non-standard Class, or some other
+type of device (there's no way to tell).
+
+## Usage
+
+This command line tool takes no arguments.
+When installed from PyPI, run as
+```
+$ bumble-usb-probe
+```
+
+When running from the source distribution:
+```
+$ python3 apps/usb-probe.py
+```
+
+!!! example
+    ```
+    $ python3 apps/usb_probe.py 
+
+    ID 0A12:0001
+    Bumble Transport Names: usb:0 or usb:0A12:0001
+    Bus/Device:             020/034
+    Class:                  Wireless Controller
+    Subclass/Protocol:      1/1 [Bluetooth]
+    Manufacturer:           None
+    Product:                USB2.0-BT
+    ```

docs/mkdocs/src/transports/usb.md

@@ -4,16 +4,56 @@ USB TRANSPORT
 The USB transport interfaces with a local Bluetooth USB dongle.
 
 ## Moniker
-The moniker for a USB transport is either `usb:<index>` or `usb:<vendor>:<product>`
-with `<index>` as the 0-based index to select amongst all the devices that appear to be supporting Bluetooth HCI (0 being the first one), or where `<vendor>` and `<product>` are a vendor ID and product ID in hexadecimal.
+The moniker for a USB transport is either:
+  * `usb:<index>`
+  * `usb:<vendor>:<product>`
+  * `usb:<vendor>:<product>/<serial-number>`
+  * `usb:<vendor>:<product>#<index>`
 
-!!! example
+with `<index>` as a 0-based index (0 being the first one) to select amongst all the matching devices when there are more than one.
+In the `usb:<index>` form, matching devices are the ones supporting Bluetooth HCI, as declared by their Class, Subclass and Protocol.
+In the `usb:<vendor>:<product>#<index>` form, matching devices are the ones with the specified `<vendor>` and `<product>` identification.
+
+`<vendor>` and `<product>` are a vendor ID and product ID in hexadecimal.
+
+!!! examples
     `usb:04b4:f901`  
-    Use the USB dongle with `vendor` equal to `04b4` and `product` equal to `f901`
+    The USB dongle with `<vendor>` equal to `04b4` and `<product>` equal to `f901`
 
     `usb:0`  
-    Use the first Bluetooth dongle
+    The first Bluetooth HCI dongle that's declared as such by Class/Subclass/Protocol
+
+    `usb:04b4:f901/0016A45B05D8`
+    The USB dongle with `<vendor>` equal to `04b4`, `<product>` equal to `f901` and `<serial>` equal to `0016A45B05D8`
+
+    `usb:04b4:f901/#1`
+    The second USB dongle with `<vendor>` equal to `04b4` and `<product>` equal to `f901`
 
 ## Alternative
 The library includes two different implementations of the USB transport, implemented using different python bindings for `libusb`.
 Using the transport prefix `pyusb:` instead of `usb:` selects the implementation based on  [PyUSB](https://pypi.org/project/pyusb/), using the synchronous API of `libusb`, whereas the default implementation is based on [libusb1](https://pypi.org/project/libusb1/), using the asynchronous API of `libusb`. In order to use the alternative PyUSB-based implementation, you need to ensure that you have installed that python module, as it isn't installed by default as a dependency of Bumble.
+
+## Listing Available USB Devices
+
+### With `usb_probe`
+You can use the [`usb_probe`](../apps_and_tools/usb_probe.md) tool to list all the USB devices attached to your host computer.
+The tool will also show the `usb:XXX` transport name(s) you can use to reference each device.
+
+
+### With `lsusb`
+On Linux and macOS, the `lsusb` tool serves a similar purpose to Bumble's own `usb_probe` tool (without the Bumble specifics)
+
+#### Installing lsusb
+
+On Mac: `brew install lsusb`
+On Linux: `sudo apt-get install usbutils`
+
+#### Using lsusb
+
+```
+$ lsusb
+Bus 004 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
+Bus 003 Device 014: ID 0b05:17cb ASUSTek Computer, Inc. Broadcom BCM20702A0 Bluetooth
+```
+
+The device id for the Bluetooth interface in this case is `0b05:17cb`.

setup.cfg

@@ -54,10 +54,11 @@ console_scripts =
     bumble-scan = bumble.apps.scan:main
     bumble-show = bumble.apps.show:main
     bumble-unbond = bumble.apps.unbond:main
+    bumble-usb-probe = bumble.apps.usb_probe:main
     bumble-link-relay = bumble.apps.link_relay.link_relay:main
 
 [options.extras_require]
-build = 
+build =
     build >= 0.7
 test =
     pytest >= 6.2

tasks.py

@@ -23,43 +23,41 @@ ROOT_DIR = os.path.dirname(os.path.realpath(__file__))
 
 ns = Collection()
 
+# Building
 build_tasks = Collection()
 ns.add_collection(build_tasks, name="build")
 
-
 @task
-def build(ctx):
+def build(ctx, install=False):
+    if install:
+        ctx.run('python -m pip install .[build]')
+
     ctx.run("python -m build")
 
-
-build_tasks.add_task(build, default=True, name="build")
-
+build_tasks.add_task(build, default=True)
 
 @task
 def release_build(ctx):
-    ctx.run('python -m pip install .[build]')
-    build(ctx)
-
+    build(ctx, install=True)
 
 build_tasks.add_task(release_build, name="release")
 
-
 @task
 def mkdocs(ctx):
     ctx.run("mkdocs build -f docs/mkdocs/mkdocs.yml")
 
-
 build_tasks.add_task(mkdocs, name="mkdocs")
 
+# Testing
 test_tasks = Collection()
 ns.add_collection(test_tasks, name="test")
 
-
 @task
 def test(ctx, filter=None, junit=False, install=False):
     # Install the package before running the tests
     if install:
         ctx.run("python -m pip install .[test]")
+
     args = ""
     if junit:
         args += "--junit-xml test-results.xml"
@@ -67,5 +65,10 @@ def test(ctx, filter=None, junit=False, install=False):
         args += " -k '{}'".format(filter)
     ctx.run("python -m pytest {} {}".format(os.path.join(ROOT_DIR, "tests"), args))
 
+test_tasks.add_task(test, default=True)
 
-test_tasks.add_task(test, name="test", default=True)
+@task
+def release_test(ctx):
+    test(ctx, install=True)
+
+test_tasks.add_task(release_test, name="release")