netdev - Re: [EXT] Re: [PATCH] qed: Enable RDMA relaxed ordering

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Date:   Tue, 24 Aug 2021 16:42:23 -0300
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     Ariel Elior <aelior@...vell.com>
Cc:     Leon Romanovsky <leon@...nel.org>, Shai Malin <smalin@...vell.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "malin1024@...il.com" <malin1024@...il.com>,
        RDMA mailing list <linux-rdma@...r.kernel.org>
Subject: Re: [EXT] Re: [PATCH] qed: Enable RDMA relaxed ordering

On Tue, Aug 24, 2021 at 07:16:41PM +0000, Ariel Elior wrote:

> In our view the qed/qede/qedr/qedi/qedf are separate drivers, hence we used
> function pointer structures for the communication between them. We use
> hierarchies of structures of function pointers to group toghether those which
> have common purposes (dcbx, ll2, Ethernet, rdma). Changing that to flat exported
> functions for the RDMA protocol is no problem if it is preferred by you.

I wouldn't twist the driver into knots, but you definately should not
be using function pointers when there is only one implementation,
eliminating that would be a fine start and looks straightforward.

Many of the functions in the rdma ops do not look complicated to move,
yes, it moves around the layering a bit, but that is OK and probably
more maintainable in the end. eg modify_qp seems fairly disconnected
at the first couple layers of function calls.

> In summary - we got the message and will work on it, but this is no small task
> and may take some time, and will likely not result in total removal of any
> mention whatsoever of rdma from the core module (but will reduce it
> considerably).

I wouldn't go for complete removal, you just need to have a core
driver with an exported API that makes some sense for the device.

eg looking at a random op

qed_iwarp_set_engine_affin()

Is an "rdma" function but all it does is call
qed_llh_set_ppfid_affinity()

So export qed_llh and move the qed_iwarp to the rdma driver

etc

Jason