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

[Christoph Hellwig]

On Wed, Sep 08, 2021 at 04:01:14PM +0900, Shunsuke Mie wrote:
> Thank you for your comment.
> >
> > 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.
> As described in the dma-buf api guide [1], the dma_device is used by dma-buf
> exporter to know the device buffer constraints of importer.
> [1] https://lwn.net/Articles/489703/

Which means for rxe you'd also have to pass the one for the underlying
net device.