USB enumeration timeouts due to missing ZLPs about arduinocore-avr

[tlyu]

No. #112 is a related issue with receiving ZLPs in non-control transactions, very likely fixed by the combination of arduino/Arduino#6886 and keyboardio/Kaleidoscope-Bundle-Keyboardio#51. Note that arduino/Arduino#6886 seems to have been stalled for years due to lack of a signed CLA.

[per1234]

Hi @tlyu. Thanks for your report! Is this the same bug that was previously reported here: #112 ?

[tlyu]

Minimal test case: With an Arduino Micro, edit the USB product string in boards.txt to be

Arduino Micro f0123456789abcdef

which is 31 ASCII characters long, and produces a string descriptor exactly 64 bytes long. Compile and upload any sketch that enables the CDC interface (it's enabled by default, I think). That will demonstrate the bug.

I've tested the above case via manual control read on macOS of more bytes than are in the descriptor. On Windows, there is a 5-second timeout on an initial attempt to fetch the string descriptor by requesting 255 bytes. Subsequent requests for the string descriptor do provide correct lengths, and succeed.

(For a HID report descriptor, a timeout will cause Windows to ignore that HID interface, but that's harder to produce a minimal test case for.)

[tlyu]

Demo script, using the Python usb1 module (requires libusb):

import usb1

with usb1.USBContext() as uc:
    # uc.setDebug(usb1.LOG_LEVEL_DEBUG)
    dh = uc.openByVendorIDAndProductID(0x2341, 0x8037)
    b1 = dh.controlRead(0x80, 6, 0x0302, 0, 64, 100)
    print(f"requested 64 bytes, got {len(b1)}")
    b2 = dh.controlRead(0x80, 6, 0x0302, 0, 255, 100)
    print(f"requested 255 bytes, got {len(b2)}")

Failure output:

requested 64 bytes, got 64
Traceback (most recent call last):
  File "/Users/tlyu/src/py-hid-utils/avrdesc-demo.py", line 8, in <module>
    b2 = dh.controlRead(0x80, 6, 0x0302, 0, 255, 100)
  File "/Users/tlyu/src/keyboardio/.venv/lib/python3.10/site-packages/usb1/__init__.py", line 1350, in controlRead
    transferred = self._controlTransfer(
  File "/Users/tlyu/src/keyboardio/.venv/lib/python3.10/site-packages/usb1/__init__.py", line 1307, in _controlTransfer
    mayRaiseUSBError(result)
  File "/Users/tlyu/src/keyboardio/.venv/lib/python3.10/site-packages/usb1/__init__.py", line 127, in mayRaiseUSBError
    __raiseUSBError(value)
  File "/Users/tlyu/src/keyboardio/.venv/lib/python3.10/site-packages/usb1/__init__.py", line 119, in raiseUSBError
    raise __STATUS_TO_EXCEPTION_DICT.get(value, __USBError)(value)
usb1.USBErrorTimeout: LIBUSB_ERROR_TIMEOUT [-7]

Verbose fail log (debug logging): avrdesc-fail-long.txt