Thinking about NCQ support for NetBSD

[Brian Buhrow <buhrow%nfbcal.org@localhost>]

        hello.  Recently I've been working on some fixes for the mpt(4)
driver.  In the process of getting those fixes working, I began thinking
about how hard it would be to get NCQ tag queueing working for NetBSD.  In
the process of getting my head around what is involved, I find I have
questions.  If someone wants to share what they know here or privately,
I'd be interested in reading.

1.  I read a document that discussed ahcisata and its advantages over
traditional IDE mode.  One of the advantages it touted was that ahcisata
would support NCQ tag queueing.  Is it a requirement in order for NCQ
tag queueing to work that the interface card support it as well?  For
example, the viaide(4) driver supports SATA controllers, but says nothing
about NCQ support or the potential for it.

2.  Does anyone have any preliminary patches for NCQ support that the never
got into the system?

-thanks
-Brian