On Wed, 21 Apr 2010, Luben Tuikov wrote: > Well BOT is the exception. In general transports aren't concerned > with the size, etc of the command. They just transport the CDB. UAS > for example, being in SAM-spirit transport and in this sense being > mature over BOT. > > The transfer length is part of the CDB, if the command is expected to > transfer data and ATA PT CDBs are no exception. The transport bridge > would "convert" from one transport protocol into another and it thus > need to know the transfer size if any to prep the next protocol for > the command. In this case this is visualized as > UAS(SCSI)<-->SATA(ATA). Use BOT, wlg. > > This is really the function of SAT. Unknown CDBs are treated as > bi-directional to let the target determine data transfer direction if > any. This is somewhat off-topic, but perhaps you can help. In reading through the UAS draft specification, I didn't see any description of how disagreements over transfer lengths should be handled. Suppose the initiator thinks the CDB for a particular IN command asks for N bytes, but the target thinks the CDB asks for M bytes. What should happen if N < M or N > M? And likewise for OUT commands. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
