Jeff,
Here is another shot at adding MODE SELECT to
libata. I have used sat-r06, sbc-3 and spc-4 as
a guide. Compliance on the ATA side has some issues:
- no mechanism to issue 2 or more ATA commands
when translating a single SCSI command [in the
upstream branch, there have been patches ...]
- relies on the dev->id array (IDENTIFY DEVICE response)
always being up to date. Despite assurances I cannot
see how that is the case when multiple hosts
(initiators) can access a SATA disk.
This patch is broken into two parts and is against
libata-dev's upstream branch:
1) strengthen MODE SENSE processing and make
default mode pages visible within libata-scsi.c
2) add MODE SELECT SCSI command support.
Two attributes can be changed with these patches:
- WCE: write cache enable [cache mode page]
- DRA: disable read ahead [cache mode page]
Testing: upstream branch seems to be broken wrt SG_IO
as the largest amount of data that can be sent per
command is 4 KB. A 50 MB write (segmented to 4 KB per
command) slowed down from 14 seconds with WCE=1 to
107 seconds with WCE=0. sg_dd was used for the transfer
and sdparm to change WCE. ST380013AS disk and
sata_sil LLD.
The attachments are mime text because I wasn't able
to do otherwise.
Signed-off-by: Douglas Gilbert <dougg@xxxxxxxxxx>
Doug Gilbert
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