AxiStreamSink cannot handle tdata X-bytes for bytes to ignore (tkeep=0)

[svsi]

The AxiStreamSink reads and converts tdata without respecting the tkeep bits. This can be a problem as some developers are driving tdata bits and bytes to X or U if the respective tkeep bits are low (0). This is for instance done by the Xilinx AXI4-Stream Data Width Converter when downsizing the bus and the ratio is NOT an integer multiple.

One work-around would be to set the COCOTB_RESOLVE_X environment variable to a value different from VALUE_ERROR (default). I do not like the solution though as in general I would like to see the exception if any output of a DUT that has no validity qualifier returns something else than 0 or 1.
Therefore, I convert tdata manually to 0,1 inside the top VHDL file (in my case the testbench). However, I would prefer to have this issue fixed in a future release of cocotbext-axi.

[alexforencich]

This is really related to the crappy BinaryValue type in cocotb that has totally screwed up indexing. When that gets fixed, then I'm definitely going to properly utilize it when extracting byte lanes.