On Mon, 2006-12-18 at 17:12 -0500, Ming Zhang wrote: > See this code piece > > http://lxr.linux.no/source/drivers/scsi/libata-scsi.c?v=2.6.18#L1049 > > 1056 lba |= ((u64)scsicmd[2]) << 24; > 1057 lba |= ((u64)scsicmd[3]) << 16; > 1058 lba |= ((u64)scsicmd[4]) << 8; > 1059 lba |= ((u64)scsicmd[5]); > > it can also be written as > > lba = be32_to_cpu(*(u32 *)(&scsicmd[2]) > > > i wrote a simple code to test this and i found second one is several > time faster than first one. > > if there any pitfall with 2nd way? personally I find the original code a lot more clear in what the intent of it is. The device/command give you a set of BYTES, and they get pieced together into a meaning here... -- if you want to mail me at work (you don't), use arjan (at) linux.intel.com Test the interaction between Linux and your BIOS via http://www.linuxfirmwarekit.org -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
