> From: James Bottomley [mailto:jbottomley@xxxxxxxxxxxxx] > > On Fri, 2014-07-18 at 00:51 +0000, Elliott, Robert (Server Storage) > wrote: ... > > > > Also, in both sd_setup_flush_cmnd and sd_sync_cache: > > cmd->cmnd[0] = SYNCHRONIZE_CACHE; > > cmd->cmd_len = 10; > > > > SYNCHRONIZE CACHE (16) should be favored over SYNCHRONIZE > > CACHE (10) unless SYNCHRONIZE CACHE (10) is not supported. (sorry - meant "unless ... 16 is not supported") > For what reason. We usually go for the safe alternatives, which is 10 > byte commands because they have the widest testing and greatest level of > support. We don't do range flushes currently, so there doesn't seem to > be a practical different. If we did support range flushes, we'd likely > only use SC(16) on >2TB devices. > > James A goal of the simplified SCSI feature set idea is to drop all the short CDBs that have larger, more capable equivalents - don't carry READ 6/10/12/16 and SYNCHRONIZE CACHE 10/16, just keep the 16-byte versions. With modern serial IU-based protocols, short CDBs don't save any transfer time. This will simplify design and testing on both initiator and target sides. Competing command sets like NVMe rightly point out that SCSI has too much legacy baggage - all you need for IO is one READ, one WRITE, and one FLUSH command. That's why SBC-3 ended up with these warning notes for all the non-16 byte CDBs: NOTE 15 - Migration from the SYNCHRONIZE CACHE (10) command to the SYNCHRONIZE CACHE (16) command is recommended for all implementations. If the LBA field in SYNCHRONIZE CACHE went obsolete, then maybe SYNCHRONIZE CACHE (10) would be kept instead of (16), but that field is still present. So, (16) is the likely survivor. --- Rob Elliott HP Server Storage _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
