This message is from the T13 list server.
(please read my reply timestamped 00:48am EST, before this one)
Curtis Stevens wrote:
One thing to keep in mind is that we do not want the bridge to look at the command code or any other register. We want SCSI to be a blind tunnel to the ATA device. The bridge should not look at the command code, sector count, or any other part of the register set. This is what makes it work for standard and vendor specific commands. It also makes it so new commands can be implemented without changing the bridge. This is why length is also important.
I do agree 100% with this.
I thought of an additional point, relating to this, while I was driving through the rain tonight (hello Hurricane Bonnie):
One of the key values of SAT to my user base is the leverage of _existing_ SCSI application software. Particularly, I wish to use this ATA passthru CDB via pre-existing SCSI system call methods (ioctl).
As such, there is no opportunity for me to add an ATA-specific command-protocol field to Linux's submit-a-SCSI-command system call. I have only the SCSI CDB, transfer length, and transfer direction to work with. Any ATA specifics _must_ be encapsulated within the ATA passthru CDB.
I think my need fits nicely with your "blind SCSI tunnel to ATA device" bridge model.
Jeff
