On Wed, 2007-12-19 at 17:31 +1100, Rusty Russell wrote: > This patch series is the start of my attempt to simplify and make explicit > the chained scatterlist logic. > > It's not complete: my SATA box boots and seems happy, but all the other > users of SCSI need to be updated and checked. But I've gotten far enough > to believe it's worth persuing. Sorry for the delay in looking at this, I was busy with Holidays and things. When I compare sg_ring with the current sg_chain (and later sg_table) implementations, I'm actually struck by how similar they are. The other thing I note is that the problem you're claiming to solve with sg_ring (the ability to add extra scatterlists to the front or the back of an existing one) is already solved with sg_chain, so the only real advantage of sg_ring was that it contains explicit counts, which sg_table (in -mm) also introduces. The other differences are that sg_ring only allows adding at the front or back of an existing sg_ring, it doesn't allow splicing at any point like sg_chain does, so I'd say it's less functional (not that I actually want anyone ever to do this, of course ...) The final point is that sg_ring requires a two level traversal: ring list then scatterlist, whereas sg_chain only requires a single level traversal. I grant that we can abstract out the traversal into something that would make users think they're only doing a single level, but I don't see what the extra level really buys us. The above analysis seems to suggest that sg_chain is simpler and has more functionality than sg_ring, unless I've missed anything? The only thing missing from sg_chain perhaps is an accessor function that does the splicing, which I can easily construct if you want to try it out in virtio. James - To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
