Add usb-endpoint-count checking

.. however, the number of endpoints is only set for SAMD (8).
Other ports need to set the value.  Otherwise, the build will show
the message
```
Unable to check whether maximum number of endpoints is respected
```

1 files changed, 11 insertions, 0 deletions

diff --git a/tools/gen_usb_descriptor.py b/tools/gen_usb_descriptor.py
index fb91fd334..baee8cad7 100644
--- a/tools/gen_usb_descriptor.py
+++ b/tools/gen_usb_descriptor.py
@@ -62,6 +62,8 @@ parser.add_argument('--midi_ep_num_out', type=int, default=0,
                     help='endpoint number of MIDI OUT')
 parser.add_argument('--midi_ep_num_in', type=int, default=0,
                     help='endpoint number of MIDI IN')
+parser.add_argument('--max_ep', type=int, default=0,
+                    help='total number of endpoints available')
 parser.add_argument('--output_c_file', type=argparse.FileType('w', encoding='UTF-8'), required=True)
 parser.add_argument('--output_h_file', type=argparse.FileType('w', encoding='UTF-8'), required=True)
 
@@ -376,6 +378,15 @@ if 'AUDIO' in args.devices:
 # interface cross-references.
 interfaces = util.join_interfaces(interfaces_to_join, renumber_endpoints=args.renumber_endpoints)
 
+if args.max_ep != 0:
+    for interface in interfaces:
+        for subdescriptor in interface.subdescriptors:
+            endpoint_address = getattr(subdescriptor, 'bEndpointAddress', 0) & 0x7f
+            if endpoint_address > args.max_ep:
+                raise ValueError("Endpoint address %d of %s may not exceed %d" % (endpoint_address & 0x7f, interface.description, args.max_ep))
+else:
+    print("Unable to check whether maximum number of endpoints is respected", file=sys.stderr)
+
 # Now adjust the CDC interface cross-references.
 
 cdc_union.bMasterInterface = cdc_comm_interface.bInterfaceNumber