Re: [PATCH 1/3 v3] dma: document dma_{un}map_{single|sg}_attrs() interface

Jesse Barnes
2008-03-05T19:02:45Z

On Wednesday, March 05, 2008 10:13 am akepner@sgi.com wrote:
> On Fri, Feb 29, 2008 at 12:37:56PM -0600, James Bottomley wrote:
> > ....
> > To be honest, I still don't like the name. SYNC_ON_WRITE is the SN2
> > implementation. What it's actually doing is implementing strict
> > ordering semantics. I think it should really be
> > DMA_ATTR_STRICT_ORDERING (with a corresponding
> > DMA_ATTR_RELAXED_ORDERING)....
>
> I've been thinking about a new name, but don't like
> DMA_ATTR_STRICT_ORDERING.
>
> What I'm trying to do is to establish order (across
> a NUMA fabric) of DMA to different memory regions, i.e.,
> DMA to memory region A forces all outstanding DMA (to
> memory regions B, C,....) to complete first.
>
> DMA_ATTR_STRICT_ORDERING sounds like a PCI thing to me,
> and this is a NUMA interconnect thing.

Well, we used to call it a DMA barrier back in the old days, so
DMA_ATTR_BARRIER might work (or DMA_ATTR_INTERCONNECT_BARRIER if you want to
be extra clear about what it's doing).

Jesse