Re: [rdma 14/16] RDMA/irdma: Add ABI definitions

[Jason Gunthorpe <jgg@mellanox.com>]

On Sat, Jul 06, 2019 at 04:15:20PM +0000, Saleem, Shiraz wrote:
> > Subject: Re: [rdma 14/16] RDMA/irdma: Add ABI definitions
> > 
> > On Fri, Jul 05, 2019 at 04:42:19PM +0000, Saleem, Shiraz wrote:
> > > > Subject: Re: [rdma 14/16] RDMA/irdma: Add ABI definitions
> > > >
> > > > On Thu, Jul 04, 2019 at 10:40:21AM +0300, Leon Romanovsky wrote:
> > > > > On Wed, Jul 03, 2019 at 07:12:57PM -0700, Jeff Kirsher wrote:
> > > > > > From: Mustafa Ismail <mustafa.ismail@intel.com>
> > > > > >
> > > > > > Add ABI definitions for irdma.
> > > > > >
> > > > > > Signed-off-by: Mustafa Ismail <mustafa.ismail@intel.com>
> > > > > > Signed-off-by: Shiraz Saleem <shiraz.saleem@intel.com>
> > > > > > include/uapi/rdma/irdma-abi.h | 130
> > > > > > ++++++++++++++++++++++++++++++++++
> > > > > >  1 file changed, 130 insertions(+)  create mode 100644
> > > > > > include/uapi/rdma/irdma-abi.h
> > > > > >
> > > > > > diff --git a/include/uapi/rdma/irdma-abi.h
> > > > > > b/include/uapi/rdma/irdma-abi.h new file mode 100644 index
> > > > > > 000000000000..bdfbda4c829e
> > > > > > +++ b/include/uapi/rdma/irdma-abi.h
> > > > > > @@ -0,0 +1,130 @@
> > > > > > +/* SPDX-License-Identifier: GPL-2.0 OR BSD-2-Clause */
> > > > > > +/* Copyright (c) 2006 - 2019 Intel Corporation.  All rights reserved.
> > > > > > + * Copyright (c) 2005 Topspin Communications.  All rights reserved.
> > > > > > + * Copyright (c) 2005 Cisco Systems.  All rights reserved.
> > > > > > + * Copyright (c) 2005 Open Grid Computing, Inc. All rights reserved.
> > > > > > + */
> > > > > > +
> > > > > > +#ifndef IRDMA_ABI_H
> > > > > > +#define IRDMA_ABI_H
> > > > > > +
> > > > > > +#include <linux/types.h>
> > > > > > +
> > > > > > +/* irdma must support legacy GEN_1 i40iw kernel
> > > > > > + * and user-space whose last ABI ver is 5  */ #define
> > > > > > +IRDMA_ABI_VER
> > > > > > +6
> > > > >
> > > > > Can you please elaborate about it more?
> > > > > There is no irdma code in RDMA yet, so it makes me wonder why new
> > > > > define shouldn't start from 1.
> > > >
> > > > It is because they are ABI compatible with the current user space,
> > > > which raises the question why we even have this confusing header file..
> > >
> > > It is because we need to support current providers/i40iw user-space.
> > > Our user-space patch series will introduce a new provider (irdma)
> > > whose ABI ver. is also 6 (capable of supporting X722 and which will
> > > work with i40iw driver on older kernels) and removes providers/i40iw from rdma-
> > core.
> > 
> > Why on earth would we do that?
> > 
> A unified library providers/irdma to go in hand with the driver irdma and uses the ABI header.
> It can support the new network device e810 and existing x722 iWARP device. It obsoletes
> providers/i40iw and extends its ABI. So why keep providers/i40iw around in rdma-core?

Why rewrite a perfectly good userspace that is compatible with the
future and past kernels?

Is there something so wrong with the userspace provider to need this?

Jason