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

[Daniel Axtens <dja@axtens.net>]

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> 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.

Regards,
Daniel



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