usbd: Call _inst directly rather than singleton function.

Margin throughput improvement by removing one function call.

Setting USBInterface.submit_xfer = USBDevice._submit_xfer would
seem like the next natural step, but this didn't seem to change
performance above the noise level.

Signed-off-by: Angus Gratton <angus@redyak.com.au>

Author: projectgus

micropython/usbd/device.py

@@ -584,7 +584,7 @@ def xfer_pending(self, ep_addr):
         # Return True if a transfer is already pending on ep_addr.
         #
         # Only one transfer can be submitted at a time.
-        return bool(get_usbdevice()._ep_cbs[ep_addr])
+        return bool(_inst._ep_cbs[ep_addr])
 
     def submit_xfer(self, ep_addr, data, done_cb=None):
         # Submit a USB transfer (of any type except control)
@@ -623,17 +623,17 @@ def submit_xfer(self, ep_addr, data, done_cb=None):
         # function has returned to the caller.
         if not self._open:
             raise RuntimeError("Not open")
-        get_usbdevice()._submit_xfer(ep_addr, data, done_cb)
+        _inst._submit_xfer(ep_addr, data, done_cb)
 
     def set_ep_stall(self, ep_addr, stall):
         # Set or clear endpoint STALL state, according to the bool "stall" parameter.
         #
         # Generally endpoint STALL is handled automatically by TinyUSB, but
         # there are some device classes that need to explicitly stall or unstall
         # an endpoint under certain conditions.
-        if not self._open or ep_addr not in get_usbdevice()._eps:
+        if not self._open or ep_addr not in _inst._eps:
             raise RuntimeError
-        get_usbdevice()._usbd.set_ep_stall(ep_addr, stall)
+        _inst._usbd.set_ep_stall(ep_addr, stall)
 
     def get_ep_stall(self, ep_addr):
         # Get the current endpoint STALL state.
@@ -642,4 +642,4 @@ def get_ep_stall(self, ep_addr):
         # set_ep_stall().
         if not self._open or ep_addr not in get_usbdevice()._eps:
             raise RuntimeError
-        return get_usbdevice()._usbd.get_ep_stall(ep_addr)
+        return _inst._usbd.get_ep_stall(ep_addr)