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    SubjectRe: [PATCH 03/25] dma-direct: take dma-ranges/offsets into account in resource mapping
    I can't really comment on the dma-ranges exlcusion for P2P mappings,
    as that predates my involvedment, however:

    On Wed, Apr 20, 2022 at 11:32:07AM +0300, Serge Semin wrote:
    > See, if I get to map a virtual memory address to be accessible by any
    > PCIe peripheral device, then the dma_map_sg/dma_map_page/etc
    > procedures will take the PCIe host controller dma-ranges into account.
    > It will work as expected and the PCIe devices will see the memory what
    > I specified. But if I get to pass the physical address of the same
    > page or a physical address of some device of the DEVs space to the
    > dma_map_resource(), then the PCIe dma-ranges won't be taken into
    > account, and the result mapping will be incorrect. That's why the
    > current dma_map_resource() implementation seems very confusing to me.
    > As I see it phys_addr_t is the type of the Interconnect address space,
    > meanwhile dma_addr_t describes the PCIe, DEVs address spaces.
    >
    > Based on what I said here and in my previous email could you explain
    > what do I get wrong?

    You simply must not use dma_map_resource for normal kernel memory.
    So while the exclusion might be somewhat confusing, that confusion
    really should not matter for any proper use of the API.

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