Re: [RFC PATCH 1/3] RDMA/umem: Change for rdma devices has not dma device

[Christoph Hellwig]

On Wed, Sep 08, 2021 at 03:16:09PM +0900, Shunsuke Mie wrote:
> To share memory space using dma-buf, a API of the dma-buf requires dma
> device, but devices such as rxe do not have a dma device. For those case,
> change to specify a device of struct ib instead of the dma device.

So if dma-buf doesn't actually need a device to dma map why do we ever
pass the dma_device here?  Something does not add up.