On 09/14/05 14:43, James Bottomley wrote: > On Wed, 2005-09-14 at 00:57 -0400, Sergey Panov wrote: > >>Because set of valid LUN id represented by 8 byte combinations is not >>isomorphic to the set of unsigned int values from 0 to UINT64_MAX. While > > > The transformation we're using is an isomorphism that happens to have > the important property that single level type 00b LUNs are numerically > equal to the legacy uses of the lun value. > > >>scsilun_to_int() will convert legal LUN id into some integer, the >>int_to_scsilun() function will not produce legal LUN id for any >>arbitrary integer lun value. > > > No that's what I said. We limit the integer scanned luns to < 256 and > use representation 00b > > >>For example, sequential LUN scanning should be stopped at int lun = 255 >>because result of converting value 256 by int_to_scsilun() will be >>either illegal(best case) or equivalent to int lun = 0. > > > It is. That's this bit of the code: > > @@ -965,6 +964,13 @@ static void scsi_sequential_lun_scan(str > max_dev_lun = min(8U, max_dev_lun); > > /* > + * regardless of what parameters we derived above, on no > + * account scan further than SCSI_SCAN_LIMIT_LUNS > + */ > + if (max_dev_lun > SCSI_SCAN_LIMIT_LUNS + 1) > + max_dev_lun = SCSI_SCAN_LIMIT_LUNS + 1; > + > > > >>LUN id should be presented to the management layers in a way similar to >>MAC addresses or FC/SAS/... WWN . E.g. the usual LUN 4 on some FC >>device will be identified by something like (in 00b, or "Peripheral >>device addressing"): >> >>WWPN = 22:00:00:0c:50:05:df:6d >>LUN = 00:04:00:00:00:00:00:00 >> >> >>Interestingly enough, the following is also LUN = 4 device, but in a >>different addressing mode (01b, AKA "Logical unit addressing"): >> >>WWPN = 22:00:00:0c:50:05:df:6d >>LUN = 40:04:00:00:00:00:00:00 > > > Firstly, those two LUNs are actually not equivalent (according to SAM-3 > section 4.9.1) because two luns are defined to be different if expressed > in different representations. > > Secondly, The idea of using u64 is that all transports that don't use > hierarchical LUNs can simply copy the number as they do today. This > idea rests on the assumption that arrays responding to REPORT_LUNS on > these transports always reply with type 00b. This assumption is > suggested (but not mandated) in SAM. If they violate this assumption, > we'll just reject all the LUNs and I'll get a bug report. I was actually going to reply to this email and write something sensible, but on second thought I see that it would be a _complete_ waste of time, effort and keystrokes. "If they violate this assumption, we'll just reject all the LUNs" and "I'll get a bug report" tops it all off. 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
