On Sat, May 17, 2014 at 9:51 PM, David Matlack <matlackda...@gmail.com> wrote: > On Sat, May 17, 2014 at 9:12 PM, Joe Perches <j...@perches.com> wrote: >> The if seems unnecessary. >> >> Perhaps declare a u16 return var or use >> >> return lower_16 + upper_16; > > I agree it's fishy... but using overflow doesn't produce the same result: > > (u16) 65536 == 0 > 65536 - 65535 == 1 > > Now which is the correct result, I have no idea.
I think the checksum algorithm being used here is RFC 1071 [1]. Which means the if is correct and just accounting for double overflow. > The eeprom on this device is > small (0x80 bytes max, not enough to trigger overflow) and I have no Sorry, I was wrong about this. I was thinking in terms of summing bytes, but the checksum is summing words. Overflow _does_ get triggered. I think I'll go over this patch again while looking at the RFC to make sure everything is ok. Thanks! [1] http://tools.ietf.org/html/rfc1071 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
