Re: [PATCH v2 04/19] powerpc: Create pci_controller_ops.dma_dev_setup and shim

[Michael Ellerman <mpe@ellerman.id.au>]

On Tue, 2015-04-07 at 09:44 +0200, Arnd Bergmann wrote:
> On Tuesday 07 April 2015 10:31:36 Daniel Axtens wrote:
> > > Please see https://patchwork.ozlabs.org/patch/431333/ for related work.
> > > 
> > I'm familiar with that patch series - I've been helping Yijing get it up
> > to speed on PowerPC.
> > 
> > 
> > > I think it would be better not to introduce another architecture-specific
> > > pci host bridge operations structure, but instead consolidate into
> > > the one that is already there. We are also adding a generic way to set up
> > > PCI DMA, so it would seems reasonable to hook into that place.
> > I see what you're getting at, and I agree that we want to move towards
> > generic operations. 
> > 
> > However, I think this should go in as is at this point, for two main
> > reasons:
> > 
> > 1) This is a good midpoint that makes it easier to move to a generic
> > structure. Our arch specific stuff is quirky and difficult. This patch
> > series does a lot to reduce the complexity, and would make it very easy
> > to move these ops into a generic structure at some future point. 
> > 
> > 2) Trying to go generic at this point risks making the change set so
> > complex and wide ranging that it will really struggle to get in. For
> > example, Yijing's patch set, despite not changing any of the quirky
> > stuff in PowerPC, is already quite long, and will require agreement from
> > a lot of people before it can go in.
> > 
> > Much as I would like to have everything as generic as possible, if we
> > were to try to do the whole job in one go, it'd become a big, difficult,
> > messy patch set, and would be less likely to happen than if we were to
> > do it in two steps.
> 
> Ok, fair enough. Let's do this one first then.

Thanks Arnd.

cheers