Re: [PATCH rdma-next] IB/mlx5: Use ib_dma APIs instead of open access to parent device

[Leon Romanovsky <leon@kernel.org>]

On Tue, Nov 24, 2020 at 03:34:56AM +0000, Parav Pandit wrote:
>
>
> > From: Jason Gunthorpe <jgg@nvidia.com>
> > Sent: Monday, November 23, 2020 7:30 PM
> >
> > On Mon, Nov 23, 2020 at 10:24:00AM +0200, Leon Romanovsky wrote:
> > > From: Parav Pandit <parav@nvidia.com>
> > >
> > > DMA operation of the IB device is done using ib_device->dma_device.
> > > This is well abstracted using ib_dma APIs.
> > >
> > > Hence, instead of doing open access to parent device, use IB core
> > > provided dma mapping APIs.
> >
> > Why?
> >
> > The ib DMA APIs are for people using verbs, they are only needed to pack things
> > into the ib_sge
> >
> > If you are inside a driver, not using the verbs API, or not using ib_sge, then you
> > should not be using the ib_dma API
> >
> Thanks for clarifying this. Using ib_dma apis make the code clear for dma device access clear and explicit.
>
> > It is an abberation, we should minimize its use.
> Alright. In that case will use the pci_dev as mlx5 driver internally has the knowledge of it and avoid using ib_dma APIs.

Yeah, let's do v2, although I don't understand the purpose of ib_dma
helpers if ib drivers can't use it.

Thanks