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From:   Logan Gunthorpe <logang@deltatee.com>
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Date:   Fri, 31 Aug 2018 13:11:48 -0600
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Subject: Re: [PATCH v5 06/13] PCI/P2PDMA: Add P2P DMA driver writer's
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On 31/08/18 11:38 AM, Christian König wrote:
> If you can separate out adding the detection I can take a look adding 
> this with my DMA-buf P2P efforts.

Oh, maybe my previous email wasn't clear, but I'd say that detection is
already separate from ZONE_DEVICE. Nothing really needs to be changed.
I just think you'll probably want to write you're own function similar
to pci_p2pdma_distance that perhaps just takes two pci_devs instead of
the list of clients as is needed by nvme-of-like users.

To enable a whitelist we just have to handle the case where
upstream_bridge_distance() returns -1 and check if the devices are in
the same root complex with supported root ports before deciding the
transaction is not supported.

Logan