On Fri, 2017-01-27 at 12:32 -0800, Tyrel Datwyler wrote: > Its possible being the end of the week I'm just a little dense, but > wouldn't be64_to_cpu() imply that we are byte-swapping something that is > already, or supposedly already, in BE format to cpu endianness? Which on > a BE cpu I would expect a no-op, and on a LE cpu the 64bit word to have > been swapped from BE --> LE?
It's in BE format in memory. In LE mode, loading it into a register will get it the wrong way around, thus we have to swap it again. Once in a register it has no "endianness" per-se, what matters is that the act of loading from memory to a register would have loaded it the wrong way around in LE. > In my eyes the code does seem to support what I've argued. The same > thing is done in the scsi VIO drivers. The CRQ structure is laid out and > annotated BE. We use cpu_to_be() calls to load any non 8bit field. > Finally, each word is swapped to cpu endian when we hand it off for the > hcall. > > from ibmvfc_send_event(): > > __be64 *crq_as_u64 = (__be64 *) &evt->crq; > > <..snip..> > > if ((rc = ibmvfc_send_crq(vhost, be64_to_cpu(crq_as_u64[0]), > be64_to_cpu(crq_as_u64[1])))) { > > Again, maybe I'm missing something.