"David S. Miller" writes: > From: Ed L Cashin > Date: Mon, 19 Sep 2005 10:24:00 -0400 > >> 1) Passing le64_to_cpup an unaligned pointer is "OK" and within the >> intended use of the function. I'm having trouble finding whether >> this is documented somewhere. >> >> 2) These new changes to the sparc64 unaligned access fault handling >> will make it OK to leave the aoe driver the way it is in the >> mainline kernel. > > Both #1 and #2 are true. > > Although it's very much discouraged to dereference unaligned pointers, > especially in performance critical code (which this AOE case is not, > thankfully), because performance will be really bad as the trap > handler has to fix up the access on RISC platforms. Roland Dreier writes: > David> Although it's very much discouraged to dereference > David> unaligned pointers, especially in performance critical code > David> (which this AOE case is not, thankfully), because > David> performance will be really bad as the trap handler has to > David> fix up the access on RISC platforms. > > Also, ia64 has a tendency to print an ugly message in the kernel log > for unaligned accesses. Has anyone tried AoE on ia64? > > It might be better to change the AoE code to use get_unaligned(), just > to document what's going on. Although clearly the sparc64 patch is > correct as well -- we should never silently return the wrong data. This patch comments the fact that although passing le64_to_cpup et al. is within the intended use of the byteorder macros, using get_unaligned is the recommended way to go. Please speak up if there's a better place for this documentation to go or a better way to say it. document alignment and byteorder macros Signed-off-by: Ed L. Cashin