stream: make use of reverse parameter for changing byte endianness - #2346
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ozel wants to merge 2 commits into
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stream: make use of reverse parameter for changing byte endianness#2346ozel wants to merge 2 commits into
ozel wants to merge 2 commits into
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| if reverse: | ||
| # reverse order/endianness of bytes | ||
| if nbits_from % 8: | ||
| raise ValueError("When reversing ratio=1 streams, data width must be a multiple of 8 bits") | ||
| self.comb += source.data.eq(reverse_bytes(sink.data)), |
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you could put this after sink.connect(source)
that way it overwrites the source.data.eq(sink.data) of sink.connect(source), just like in verilog
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ah sure, yes of course! Do you think enabling reversal of byte order in streams this way is generally acceptable?
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When
stream.Convert()operates on equal data widths (nbits_from = nbits_to) thereverseparameter wasn't used so far in_IdentityConverter(). Only in case of up/down conversion, e.g. from 8 to 32 bit width and vice versa,reversecould be used to swap byte endianness.With this PR,
Convert(...,reverse=True)can be used to reverse byte order of equally-sized LiteX streams. I have not seen an alternative LiteX stream module that could do this. This is handy for dealing with UDP streams as the etherbone/UDP core of LiteEth converts Ethernet payloads to little endian already on reception and independently of downstream processing in a CPU core (see enjoy-digital/liteeth#82).There should be a built-in LiteX feature to convert a streams' byte order like this commit. Please let me know if there is a more canonical way that I've missed.