Re: [PATCH 0/19] clean ups on the drivers

[James Bottomley <James.Bottomley@SteelEye.com>]

On Tue, 2007-05-15 at 12:57 +0100, Christoph Hellwig wrote:
> On Tue, May 15, 2007 at 06:54:16AM -0500, James Bottomley wrote:
> > Er ... I really hope not ... that's exactly how the parisc iommu
> > platform code works ... and why I designed the generic dma mapping this
> > way.  The key thing parisc needed was the ability to walk up different
> > busses until it found the iommu (for example the pci bus -> dino -> GSC
> > -> IOMMU) which it does by traversing the dev->parent; However, I didn't
> > mandate working this way for other architectures.
> 
> Well, the NACK was not for the implementation details but rather the
> exported and documented interface.  IIRC the rationale was that Dave wants
> to keep the sparc implementation super-optimized and avoid indirection.

Well, actually, I do understand that.  How about the weaker requirement
that you be able to call the dma_ functions on any dev (provided it's
properly parented) and leave the implementation up to the platform?

> If it was up to me I'd have something like the parisc implementation in
> generic code.

It might make sense to put it in lib ... however, I don't think many
architectures have the problems we have ... specifically certain boxes
can have >1 IOMMU, then you really have to know *which* iommu you're
programming.

James