On Monday 15 October 2007 8:10:49 am James Bottomley wrote: > OK, so could we get back to the original discussion? The question I > think you meant to ask is "does SCSI use the block layer, and if so; > how?" > > The answer is yes (just do an ls /sys/block on any scsi machine). The > how is that it bascially uses the block layer as a service library (i.e. > most SCSI services are built on top of those already provided by block). > The email you cited was basically from our one area of confusion: SCSI > and block both provide services to decode the SG_IO ioctl. This is > partly historical; block and SCSI are very much intertwined; so much so > that they both tend to drive each other's development. The programme > over the last few years has been to identify features in SCSI that > should be more generic (and hence moved to block). SG_IO is one of > these, so we end up with the situation where Block provides this as a > service (and sr, st and sd make use of it) while the sg driver still > doesn't use what the block layer provides but rolls its own. I think > the layout of how all this works is illustrated at a reasonably high > level here on slide 15: > > http://licensing.steeleye.com/support/papers/ols_2005_slides.pdf Thanks, that's exactly what I wanted to know. > > However, the response to my attempts to express this dissatisfaction on > > the SCSI list a few months ago came too close to a flamewar for me to > > consider continuing it productive. I'd still love to update the "2.4 > > scsi howto" and corresponding sg howto, but lack the expertise. The SCSI > > layer really isn't my area, and I was much happier back when I could > > avoid using it at all. > > That was because your initial inquiry came across as "I'm trying to > document this, and by the way it's rubbish". Sorry about that. Not my intent. I was aiming more at "I'm trying to document this and I don't understand how it works at all, or why it does things this way. It seems backwards from what I would expect." Rob -- "One of my most productive days was throwing away 1000 lines of code." - Ken Thompson. - 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
