有谁能指点一下，在不用SCSI_PASS_THROUGH等结构的情况下，怎么调用无驱USB设备读取数据？

  我是一个新手，现在写一个程序想向无驱USB设备读取数据。参考了ddk的例子spti，已经满足了用SCSI_PASS_THROUGH等方式读取数据。但是性能不是很高感觉不理想。看了spti.html说明，上面好像说如果要提高性能等等就最好不用SCSI_PASS_THROUGH等等的方式，不知道有什么方法没有，难道真要同上面所说的写一个SCSI的类驱动吗？
IOCTL_SCSI_PASS_THROUGH and IOCTL_SCSI_PASS_THROUGH_DIRECT are not substitutes for a SCSI class driver and should only be used for infrequent I/O processing.  For situations in which frequent SCSI commands need to be sent to a device, with strict error processing and high performance requirements, the best solution is to write a SCSI class driver that will send these CDBs to the respective devices.

没有人知道吗？