Re: [PATCH v6 3/4] SCT Write Same / DSM Trim

Tom Yan
2016-08-22T20:57:52Z

On 22 August 2016 at 18:52, Tom Yan <tom.ty89@gmail.com> wrote:
>
> For the "payload block size" that is "always" 512-byte as per the same
> spec, I don't think we need to concern about it. I think it only
> matters if we want to enable multi-block TRIM payload according to the
> reported limit in IDENTIFY DEVICE data. Probably it merely means that
> the "each of the blocks" in the reported limit will always mean 64
> TRIM entries, even on 4Kn drives, instead of 512.
>

Actually that's what we assumed in our current code that forms the DSM
command as well. See how (hob_)feature for queued TRIM and how
(hob_)nsect for non-queued TRIM are set in ata_scsi_write_same_xlat in
libata-scsi ('size / 512').

So if you are going to increase the payload block size per logical
sector size (in other word, you assume that the payload block size is
_expected_ to be the logical block size, in spite of what ACS told,
you'll need to adjust how the aforementioned fields in the ATA
taskfile are set as well.