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

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Message-ID: <732fb772-2f21-3ac9-a35a-aa4383734df5@redhat.com>
Date:	Tue, 17 May 2016 13:32:21 -0400
From:	Doug Ledford <dledford@...hat.com>
To:	Bart Van Assche <bart.vanassche@...disk.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 05/17/2016 01:29 PM, Bart Van Assche wrote:
> 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

Nice catch there Bart.  That was well before my role as maintainer and
so settles things well enough for me.  IOW, I don't feel I need to worry
about trying to maintain the dual license nature of the RDMA stack as it
was broken long before I took over.  Thanks for pointing that out.


-- 
Doug Ledford <dledford@...hat.com>
              GPG KeyID: 0E572FDD



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