On 1/14/07, Stefan Richter <[EMAIL PROTECTED]> wrote:
On 14 Jan, James Bottomley wrote:
> The block layer currently provides sector (512) byte alignment
> guarantees. However, there has been talk in SCSI of reducing that to
> word (4) since that's what most intelligent PCI controllers can cope
> with. If you have any alignment constraints, they should be expressed
> in the slave configure.
OK, thanks. I will keep the explicit setting of the mask then.
I actually think that everything should work just fine with 4 bytes
alignment, but the SBP-2 spec mentiones 8 bytes alignment for the S/G
tables. So maybe device firmwares will expect it that way even though
IEEE 1394 doesn't impose such a restriction even on transfers with a
payload of a multiple of 8 bytes.
Do you have a reference to this 8 byte alignment requirement? I
couldn't find it browsing through the standard. Also, since the SBP-2
driver has to convert the scatterlist to an SBP-2 page table, it can
just allocate the page table on a 8-byte boundary if that is required.
The entries in the scatter table have no alignment restrictions from
the SBP-2 side.
By the way, is there a way to ask the SCSI stack to limit the size of
the entries in the scatterlist to 64k? This would greatly simplify
the conversion to SBP-2 page tables, since this is the maximum size
these can hold.
cheers,
Kristian
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