On Fri, Apr 27, 2007 at 01:28:38PM -0700, David Miller wrote: > From: Christoph Hellwig <hch@xxxxxxxxxxxxx> > Date: Fri, 27 Apr 2007 16:16:58 +0100 > > > aic7xxx might not be the best driver to look at either :) In practice > > a softirq has short enough latency so this doesn't matter, but you > > should probably benchmark it on your hardware. 53x700.c which is > > the most modern scsi driver and is in about the same hardware class > > as the esp gets away without using internal queues, but it also > > has a nice internal buffer where commands can just be put into slots > > for later execution. > > This driver runs on machines with 10MHz cpus (sun4c), the delay to the > softirq surely matters for those guys :-) Hmm, okay. I still hate having the queues in the driver so we should think about a nice mid-layer helper for this. E.g. having a return value from ->queuecommand that means "prepared but not issued the command" and then an irq-safe API to grab these commands from the irq handler. This would mean all the list managment and especially the EH related code could move to the midlayer. > > Btw, using the block layer tcq code and the scsi wrappers for it > > would be nice aswell. > > Hmm, I though I was doing so by using the interfaces found in > include/scsi/scsi_tcq.h which I am doing. > > Oh, you're suggesting to use scsi_find_tag() for reconnect handling? > > Do I have to do anything special for that to work or can I just > add calls to it right now? You don't need to anything too special. You'll need calls to scsi_set_tag_type and scsi_activate_tcq in ->slave_configure, scsi_deactivate_tcq in case you need to deactivate tcq support on a device and make sure to call scsi_populate_tag_msg when starting a command. All these have nice kerneldoc descriptions in include/scsi/scsi_tcq.h. - 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
