Hi Sebastien, I think we don't need these three functions for each CRC, just one like in the Linux kernel is enough:
https://www.kernel.org/doc/htmldocs/kernel-api/API-crc-ccitt.html BR, Alan On 7/15/22, Sebastien Lorquet <sebast...@lorquet.fr> wrote: > Hi, > > Sorry to throw a rock in the pond but having a single function named > "crc32" is very wrong and is not sufficient. > > As you have discussed the polynomial length is just not enough to > describe a crc, the initial value, bit orders of input and output, and > bit inversion on input and output are all used to derive actual crc > functions. > > A proper API for an evolved project like nuttx should have a set of > functions like crc_init, crc_update and crc_final, all acting on a crc > context, just like sha and md5. > > This would also allow specific implementations to use the hardware crc > resources provided by specific circuits. > > This would allow each use of the crc routines to define and use its own > version of the crc, without interfering on other uses. > > For example I agree it would be very unwise to change the CRC kind used > by file systems as it would break so many systems. > > Sebastien > > On 7/15/22 18:54, Karel Kočí wrote: >> Excerpts from Nathan Hartman's message of July 15, 2022 6:47 pm: >>> On Fri, Jul 15, 2022 at 12:45 PM Karel Kočí <cyn...@email.cz> wrote: >>>> The impact might be pretty significant from my search and that is also >>>> why I >>>> rather discuss instead of suggesting changes. >>>> >>>> The significant place where the current crc32 implementation is used is >>>> in >>>> file systems (such as smartfs or nxffs). The change would break any >>>> existing >>>> formating of those FSs. Thus I also do not think it should be done. >>> >>> Are these file systems readable by other operating systems besides >>> NuttX? >> Those are NuttX only up to my knowledge. The change would break old >> formated >> device on NuttX version update which sounds bad to me and "fix" (or rather >> let's >> say change to some other crc32 algorithm) won't fix compatibility with >> some >> other systems... >
