Re: [PATCH 2.6.13 5/14] sas-class: sas_discover.c Discover process (end devices)

Luben Tuikov
2005-09-12T20:20:44Z

On 09/12/05 13:21, James Bottomley wrote:
>>So some storage devices that want to use addressing methods other than 00b
>>don't because we do not have 8 byte LUN support in linux, and then we have
>>other problems because of this.
>
> Well, as long as we represent the u32 (or u64) as
>
> scsilun[1] | (scsilun[0] << 8) | (scsilun[3] << 16) | (scsilun[2] << 24)
>
> I think we cover all 2 level lun bases, don't we (obviously we ignore
> levels 3 and 4 [and 6 and 8 byte extended luns])?

I fail to see why do you want to interpret LUNs? If you want
to be "future-proof", SCSI Core should use it transparently,
a la, memcpy().

If you want to print it you can use "%016llx", be64_to_cpu(*(u64 *)...),
just like WWN. _That_ will have a meaning to the application client/user,
but SCSI Core should treat it as a transparent token.

> That representation works transparently for type 00b which is what SPI
> and other legacy expects, since our lun variable is equal to the actual
> numeric lun. Although SAM allows type 01b for arrays with < 256 LUNs it
> does strongly suggest you use type 00b which hopefully will cover us for
> a while longer...

Why do you care about any of this if you support 64 bit luns?

Luben

> fc already uses int_to_scsilun and 8 byte LUN addressing, so it will
> work even in the 01b case (the numbers that the mid-layer prints will
> look odd, but at least the driver will work).