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Re: Thinking about NCQ support for NetBSD
On Tue, May 21, 2013 at 11:14:03PM -0700, Brian Buhrow wrote:
> 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.
Yeah, you need something with more than just wdc(4)/pciide(4)-style
registers. ahcisata(4), siisata(4), and mvsata(4) would be capable of
> 2. Does anyone have any preliminary patches for NCQ support that the never
> got into the system?
The first issue is the ata(4) layer, which doesn't currently support
multiple outstanding commands per drive. What little work I did on it
I probably swept away, as nothing useful came of it last I tried.
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