Re: [PATCH for-next v7 10/12] RDMA/erdma: Add the erdma module

[Jason Gunthorpe <jgg@nvidia.com>]

On Wed, May 18, 2022 at 04:30:33PM +0800, Cheng Xu wrote:
> 
> 
> On 5/10/22 9:17 PM, Jason Gunthorpe wrote:
> > On Thu, Apr 21, 2022 at 03:17:45PM +0800, Cheng Xu wrote:
> > 
> > > +static struct rdma_link_ops erdma_link_ops = {
> > > +	.type = "erdma",
> > > +	.newlink = erdma_newlink,
> > > +};
> > 
> > Why is there still a newlink?
> > 
> 
> Hello, Jason,
> 
> About this issue, I have another idea, more simple and reasonable.
> 
> Maybe erdma driver doesn't need to link to a net device in kernel. In
> the core code, the ib_device_get_netdev has several use cases:
> 
>   1). query port info in netlink
>   2). get eth speed for IB (ib_get_eth_speed)
>   3). enumerate all RoCE ports (ib_enum_roce_netdev)
>   4). iw_query_port
> 
> The cases related to erdma is 4). But we change it in our patch 02/12.
> So, it seems all right that we do not link erdma to a net device.
> 
> * I also test this solution, it works for both perftest and NoF. *
> 
> Another issue is how to get the port state and attributes without
> net device. For this, erdma can get it from HW directly.
> 
> So, I think this may be the final solution. (BTW, I have gone over
> the rdma drivers, EFA does in this way, it also has two separated
> devices for net and rdma. It inspired me).

I'm not sure this works for an iWarp device - various things expect to
know the netdevice to know how to relate IP addresses to the iWarp
stuff - but then I don't really know iWarp.

If it works at all it is not a great idea.

EFA gets by because it doesn't use IP addressing at all.

Jason