The SCSI to ATA Translation 2 (SAT-2) project is in the technical review stage pending standardization at www.t10.org. In the last month a change has been added which will break existing user space code (e.g. smartmontools). The area of concern is the ATA return descriptor and the newly introduced "Fixed format sense data" (sat2r08b.pdf section 12.2.7). SAT code has been in the kernel (libata) since 2005 and roughly complies the original SAT standard (ANSI INCITS 431-2007). There has been an anomaly between the way DSENSE in the control mode page of SPC-3 is defined and the fact that parts of SAT-1 act as if it was always set. So no matter that libata-scsi.c actually sets the DSENSE bit to 0 (line 101 libata-scsi.c in lk 2.6.30), the ATA PASS-THROUGH COMMANDs will yield descriptor sense format if requested (e.g. by the CK_COND bit). The non backwardly compatible SAT-2 change is that when DSENSE=0, the newly introduced "Fixed format sense data" should be generated by the SAT layer (SATL). *** The code in libata-scsi.c is a SATL which we control. However there are lots of other SATLs out there that are not controlled by the kernel (e.g. a SATA disk in an external USB, SAS, FC or iSCSI enclosure). That leaves a bit of a mess in the hands of applications like smartmontools that is fixable. Existing versions of smartmontools will break if a SATL complying with SAT-2 sets DSENSE=0 (and my guess is most do). I was thinking of sending a patch to change libata's setting of DSENSE to 1 but that implies that all "normal" SCSI commands (e.g. READ, WRITE and READ CAPACITY) would also return descriptor sense data. So the patch would need to include generation of descriptor format sense data where required. That might upset some applications. As a side note, sooner or later SCSI block devices (including SATA devices behind libata's SATL) will need to use descriptor sense format because the Information field in the fixed sense data format is only 32 bits. As an example: the Information field is used for the first failed LBA of a medium error. For 512 byte sectors 32 bits gets as far as 2 TB. *** If libata complies with SAT-2 DSENSE=0 handling it should probably also handle PROTOCOL="Return response information" properly as well. [It ignores it currently.] Doug Gilbert -- To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html