On 09/13/05 18:25, Patrick Mansfield wrote: > On Tue, Sep 13, 2005 at 05:02:36PM -0400, Luben Tuikov wrote: > >>On 09/13/05 16:36, Matthew Wilcox wrote: >> >>>On Tue, Sep 13, 2005 at 04:23:42PM -0400, Luben Tuikov wrote: >>> >>> >>>>A SCSI LUN is not "u64 lun", it has never been and it will >>>>never be. >>>> >>>>A SCSI LUN is "u8 LUN[8]" -- it is this from the Application >>>>Layer down to the _transport layer_ (if you cared to look at >>>>_any_ LL transport). > > > Not all HBA drivers implement a mapping to a SCSI transport, we have > raid drivers and even an FC driver that has its own lun definition that > does not fit any SAM or SCSI spec. Us too. Especially RAID. > I think the only HBA's today that can handle an 8 byte lun are lpfc and > iscsi (plus new SAS ones). > > So, we can't have one "LUN" that fits all, and it makes no sense to call > it a LUN when it is really a wtf. "u64 lun" is a lot worse than "u8 LUN[8]". you can work with the latter but the former raises questions like "How was this translated from the "u8 LUN[8]" which I use in the application client and in the transport?" Etc. Then, if your lun is 16 bits, there is no question where it is in "u8 LUN[8]" -- SAM is _clear_ on that. Second, as I said before a Logical Unit Number _is_ "u8 LUN[8]", there is _no_ MSB or LSB, and there will never be. Thus, you cannot stuff it into "u64". Yes, we _can_ have _one_ LUN that fits all, _because_ we would copy it _as_ is from the LLDD, be it 16 bits or 32 bits or whatever, in SCSI order format: Big endian. Again, SAM is clear on that. Luben - : send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
