linux-kernel - Re: CQ and RDMA READ/WRITE APIs

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Date:	Tue, 17 May 2016 10:29:49 -0700
From:	Bart Van Assche <bart.vanassche@...disk.com>
To:	Doug Ledford <dledford@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>
CC:	Christoph Hellwig <hch@....de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Sagi Grimberg <sagi@...mberg.me>,
	"linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>
Subject: Re: CQ and RDMA READ/WRITE APIs

On 05/16/2016 11:23 AM, Doug Ledford wrote:
> In this particular case, the dual license is used by the OpenFabrics
> Alliance.  They strip the RDMA stack in the kernel down to just the RDMA
> stack files and ship those separate from the rest of the kernel, along
> with the necessary user space stuff, and put the entire compilation
> under the same dual GPL/BSD license.  That's what their OFED product is.
>
> As I understand it, members of the OFA (Intel, Mellanox, Chelsio, etc.)
> actually signed an agreement as part of their membership entry into OFA
> that they would preserve that dual license when submitting code
> upstream.  This was originally intended to make sure that the stack as a
> whole could be used upstream, in distros, on switches, etc.  The idea
> being that a unified stack that could be copied around would enhance
> interoperability or something like that.
>
> I can't speak to how actively used it is any more.  I think maybe on
> switches or some other dedicated devices.  But, I was asked by the OFA
> to try and preserve it.
>
> In this particular case, Christoph wrote his code from scratch.  I'm not
> concerned with it.  It was never dual licensed and need not be.  But he
> did submit patches that modified existing dual license drivers to use
> his new code and removed their own implementation of the same thing in
> the process.  What used to be more or less functional drivers that could
> be copied and used elsewhere will no longer be able to be copied in the
> same way.  I'm just waiting for Sagi Grimberg to speak for iSER and for
> Bart van Assche to speak for SRP and let me know that they are OK with
> the change.  I think a patch set that will essentially change the
> licensing nature of their code should carry their explicit approval of
> the license change.

(+linux-rdma)

Hello Doug,

As far as I know SanDisk, a Western Digital Company, is fine with 
changing the license of the code under drivers/infiniband/ulp/srpt from 
dual licensed into GPL-only. However, if OFA members want that the 
entire RDMA core is dual licensed I think we will have to talk to Tejun:

$ PAGER= git grep EXPORT_SYMBOL_GPL drivers/infiniband/
drivers/infiniband/core/device.c:EXPORT_SYMBOL_GPL(ib_wq);

$ git show f06267104dd9112f11586830d22501d0e26245ea
commit f06267104dd9112f11586830d22501d0e26245ea
Author: Tejun Heo <tj@...nel.org>
Date:   Tue Oct 19 15:24:36 2010 +0000

     RDMA: Update workqueue usage

[ ... ]
+struct workqueue_struct *ib_wq;
+EXPORT_SYMBOL_GPL(ib_wq);
[ ... ]

$ PAGER= git grep -lw ib_wq drivers/infiniband/
drivers/infiniband/core/cache.c
drivers/infiniband/core/device.c
drivers/infiniband/core/roce_gid_mgmt.c
drivers/infiniband/core/sa_query.c
drivers/infiniband/core/umem.c
drivers/infiniband/hw/qib/qib_iba7220.c
drivers/infiniband/hw/qib/qib_iba7322.c
drivers/infiniband/hw/qib/qib_init.c

Bart.