On 15 Jan, Kristian Høgsberg wrote: > On 1/14/07, Stefan Richter <stefanr@xxxxxxxxxxxxxxxxx> wrote: >> 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. SBP-2 clause 5.2. It's also in SBP-3 even though there is no obvious benefit for this rule. > 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. Yes, after the discussion this occurred to me too but my energy reserves were already too low to wrap this up. > 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. Douglas has a very informative text on this: http://sg.torque.net/sg/sg_io.html#mozTocId154063 | [...] since lk 2.6.16 another limit comes into play: the | MAX_SEGMENT_SIZE define which is set to 64 KB. MAX_SEGMENT_SIZE is a | default and can be overridden by the LLD calling | blk_queue_max_segment_size(). Looks like we can yank out some cruft off sbp2. -- Stefan Richter -=====-=-=== ---= -==== http://arcgraph.de/sr/ - To unsubscribe from this list: 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
