Hello Martin, On Tue, Jan 28, 2025 at 10:09:35PM -0500, Martin K. Petersen wrote: > > Niklas, > > Sorry about the delay, was out for a few days. > > > I was kind of expecting some upper layer, SCSI or block, to have rejected > > an operation that is not a multiple of the sector size. > > > > Is that a silly assumption? > > Not all SCSI commands operate on logical blocks. Plus even if they do > the actual data transfer could still be larger than one block due to PI > or long writes. > > That's all a bit theoretical in the context of the archaic > sg_scsi_ioctl() call since that only takes a single page and has little > practical use. But in general we can't assume that everything is a > multiple of 512 bytes. Thank you. I basically came to the same conclusion. (We can't assume that everything is a multiple of 512 bytes.) Looking at ACS-6, Table A.2 — Command codes (sorted by command code) and looking at all commands that are of type: PIO Data-In and PIO Data-Out. Most commands use the COUNT field to mean a unit in either sectors or log page count (which is also a multiple of sectors), but some commands, e.g. TRUSTED RECEIVE 5Ch and TRUSTED SEND 5Eh, it means TRANSFER LENGTH, which is security protocol specific. Looking at TCG (SIIS), TRANSFER LENGTH is a multiple of sectors. I don't know about other security protocols (if any). It is probably quite safe to make the assumption that the COUNT field in ACS will always be a multiple of sectors for PIO Data-In and PIO Data-Out commands, so we probably could add a check in generic libata code somewhere... but by adding such a check in generic libata code, for it to be simple, it would probably need to apply to more than just PIO Data-In and PIO Data-Out commands, and I'm not sure if we can make such an assumption. Thus, I'm happy with the fix: https://lore.kernel.org/linux-ide/20250127154303.15567-2-cassel@xxxxxxxxxx/ for now. Kind regards, Niklas
