Re: CCITT-CRC16 in kernel

[Kyle Moffett]

On Aug 11, 2005, at 13:08:56, linux-os (Dick Johnson) wrote:
> Okay. Thanks. This means that hardware somehow swapped bits
> before doing a CRC. I wasn't aware that this was even possible
> as it would require additional storage, well I guess anything
> is now possible in a FPGA.
>
> The "Bible" has been:
>      http://www.joegeluso.com/software/articles/ccitt.htm
>
> Note that on the very first page, reference, is made to
> the 0x1021 poly. Then there is source-code that is entirely
> incompatible with anything in the kernel, but is supposed to
> work (it does work on my hardware).
>
> I have spent over a week grabbing everything on the Web that
> could help decipher the CCITT CRC and they all show this
> same kind of code and same kind of organization. Nothing
> I could find on the Web is like the linux kernel ccitt_crc.
> Go figure.
>
> Do you suppose it was bit-swapped to bypass a patent?

It could be that, or it could be some kernel genius figured
out that one method is faster or better or more magical than
the other on most platforms.  Since the code works well, I
would be disinclined to tinker with it. :-D.

Cheers,
Kyle Moffett

--
Q: Why do programmers confuse Halloween and Christmas?
A: Because OCT 31 == DEC 25.



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