David S. Miller writes: > It is real requirement, x86 works because unaligned > access is handled transparently by cpu. > > But on every non-x86 csum_partial I have examined, worse than > 2-byte aligned data start is totally not handled. It is not difficult > to figure out why this is the case, everyone has copied by example. :-) PPC and PPC64 are OK, I believe, since the CPU handles (almost) all unaligned accesses in hardware. (Some PowerPC implementations trap if the access crosses a page boundary but the newer ones even handle that case in hardware, and if we do get the trap we fix it up.) I notice though that if the length is odd, we (PPC) put the last byte in the left-hand (most significant) byte of a 16-bit halfword, with zero in the other byte, and add it in, whereas i386 puts the last byte in the least-significant position. Hmmm... should be OK though since I presume the result will be reduced and then converted to network byte order before being put in the packet. And since there is an end-around carry we should end up with the same bytes that i386 does. Paul. - : send the line "unsubscribe linux-net" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
