Re: [PATCH] scsi : set target can_queue from devinfo flags

[Mike Christie <michaelc@cs.wisc.edu>]

James Smart wrote:
> This sounds reasonable, but I wouldn't eliminate this can_queue limit. 

I was not going to elimitate it. It is all muddled in the one mail, so 
it is confusing.

I was just going to set it based on target vendor info table in 
userspace from a scsi daemon that was going to handle this issue and 
handle ramp ups due to QUEUE_FULL ramp downs and other scsi issues like 
the handling of sense that indicates disks changes size or report lun 
data changes.

Hannes had mentioned he was making some event infrastructure to handle 
the sense, and I thought I could extend his userspce code to handle the 
ramp up issue and handle setting this value. So for just the 
starget->can_queue issue, the daemon would listen for target hotplug 
events, then it would do sg io to device on it and get the vendor info 
and look up the target in a table and then if found would write to a 
starget->can_queue sysfs file to set the value.

The same daemon could also handle the sense handling and handle other 
errors like when to ramp up from when we ramp down due to QUEUE_FULLs. 
So it is basically a scsi-ml/lib in userpsace that could be easily 
packaged for distros to carry.