Luben Tuikov wrote:
I request inclusion of the SAS Transport Layer
and the AIC-94xx SAS LLDD into the Linux kernel.
Overall, I see the following major issues. My recommendation is that
this driver live in -mm, or outside the kernel tree, for a while to let
things shake out.
Background
----------
* There is no question that Adaptec's aic94xx and SAS code is correct
WRT the SCSI specifications. The maintainer eats, sleeps, and breathes
SAS specs. :)
* aic94xx hardware supports both SAS and SATA connections. Since SAS
and SATA are intentionally similar electrically, other vendors are
coming out with SATA+SAS hardware too.
* Acronym: "HCIL" Stands for Host/Channel/ID/LUN. Pre-SAS legacy
addressing method.
Issues
------
* Avoids existing SAS code, rather than working with it.
* Avoids existing SATA code, rather than working with it.
* Avoids (rather than fix) several SCSI core false dependencies on HCIL.
Results in code duplication and/or avoidance of needed code.
* So far, it's an Adaptec-only solution. Since it pointedly avoids the
existing SAS transport code, this results in two SAS solutions in Linux:
one for Adaptec, one for {everyone else}.
* Maintainer reminds me of my ATA mentor, Andre Hedrick: knows his
shit, but has difficulties working with the community. May need a
filter if we want long term maintenance to continue.
Resolution
----------
AFAICS, there are two paths:
Easy path: make Adaptec's solution a block driver, which allows it to
sidestep all the "doesn't play well with others" issues. Still an
Adaptec-only solution, but at least its in a separate playpen.
Hard path: Update the SCSI core and libata to work with SATA+SAS
hardware such as Adaptec's.
The hard path takes time, and won't be solved simply by shoving it in.
Jeff
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