AvalonPkts empty handling does not support all symbol sizes

[Eirikalb]

I have an application where I want to use 16 bit symbol size and a 128 bit wide bus. This should in theory result in 8 symbols and thus a 3 bit empty signal. This is also what I assume is configured when configuring if I set ``dataBitsPerSymbol:16`.

from cocotb_bus.drivers.avalon import AvalonSTPkts
self.stream_in = AvalonSTPkts(
       dut, "streamin", dut.clk, config={"dataBitsPerSymbol": 16, "firstSymbolInHighOrderBits": True}
)

So I believe that my empty signal is correctly sized to 3 bits. When trying to send packets of lets say 64 bits, so that would be 4 symbols, giving 4 empty, cocotb tries to set empty to 12.

INFO:cocotb: 20290.00ns INFO     random_big_range_small_size_test failed
INFO:cocotb:                     Traceback (most recent call last):
INFO:cocotb:                       File "/home/eirikalb/GitHub/zivid-sdk/fpga/m017_image_compressor/tb/test_m017_image_compressor.py", line 94, in random_big_range_small_size_test
INFO:cocotb:                         await test_bench.send_packet(test_input)
INFO:cocotb:                       File "/usr/local/lib/python3.9/dist-packages/cocotb/decorators.py", line 255, in __await__
INFO:cocotb:                         return (yield self)
INFO:cocotb:                       File "/home/eirikalb/GitHub/zivid-sdk/fpga/m017_image_compressor/tb/m017_image_compressor_testbench.py", line 45, in send_packet
INFO:cocotb:                         await self.stream_in._driver_send(self._array_to_binstr(pixels, 16))  # pylint: disable=protected-access
INFO:cocotb:                       File "/usr/local/lib/python3.9/dist-packages/cocotb_bus/drivers/avalon.py", line 794, in _driver_send
INFO:cocotb:                         await self._send_string(pkt, sync=sync, channel=channel)
INFO:cocotb:                       File "/usr/local/lib/python3.9/dist-packages/cocotb_bus/drivers/avalon.py", line 708, in _send_string
INFO:cocotb:                         self.bus.empty.value = bus_width - len(string)
INFO:cocotb:                       File "/usr/local/lib/python3.9/dist-packages/cocotb/handle.py", line 196, in __setattr__
INFO:cocotb:                         return object.__setattr__(self, name, value)
INFO:cocotb:                       File "/usr/local/lib/python3.9/dist-packages/cocotb/handle.py", line 458, in value
INFO:cocotb:                         self._set_value(value, cocotb.scheduler._schedule_write)
INFO:cocotb:                       File "/usr/local/lib/python3.9/dist-packages/cocotb/handle.py", line 767, in _set_value
INFO:cocotb:                         raise OverflowError(
INFO:cocotb:                     OverflowError: Int value (12) out of range for assignment of 3-bit signal ('streamin_empty')
INFO:cocotb: 20290.00ns INFO     **********************************************************************************************

The error occurs on line 708, but it seems that the issue is that when sending, the symbol size is not fully taken into consideration giving a bus length of 128 / 8 bits =16 symbols rather than 128 / 16 bits = 8 symbols. Which would then obvisouly give 16-4 instead of 4.

cocotb-bus/src/cocotb_bus/drivers/avalon.py

Line 645 in ac55515

bus_width = int(len(self.bus.data) / 8)