When debugging a SCSI miniport driver, there are three routines in which it is useful to set a breakpoint:
The routine scsiport!scsiportnotification is called right after a request is sent to the miniport. Thus, if you set a breakpoint in scsiport!scsiportnotification and then run a stack backtrace using kb 3, you can determine whether the miniport is receiving and completing requests. If the first parameter is zero, the request has been completed. If the first parameter is nonzero, the third parameter is the address of the SCSI request block (SRB) that is not being completed, and you can use the !minipkd.srb extension to further analyze the situation.
Placing a breakpoint in either scsiport!spstartiosynchronized or miniport!HwStartIo will cause a break just prior to sending a request to the miniport.