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Subject: Re: Licensing of include/linux/hash.h
To:     Martin Steigerwald <Martin.Steigerwald@proact.de>,
        Domenico Andreoli <cavok@debian.org>
Cc:     Kristian Fiskerstrand <k_f@gentoo.org>,
        Ben Finney <bignose@debian.org>,
        Nadia Yvette Chambers <nyc@holomorphy.com>,
        Arnaldo Carvalho de Melo <acme@redhat.com>,
        "919356@bugs.debian.org" <919356@bugs.debian.org>,
        "debian-legal@lists.debian.org" <debian-legal@lists.debian.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Jens Axboe <jens.axboe@oracle.com>
References: <20190115170017.5gxarqxzfezgr5ld@dumbo>
 <c3aa1b37-60bb-aceb-10ba-9768157a2a5a@gentoo.org>
 <20190211072259.GA19224@nouveau> <2977287.v5rPGuGa1n@merkaba>
From:   Jens Axboe <axboe@kernel.dk>
Message-ID: <2f9f7dd8-3d47-d463-6322-c6d9865cd545@kernel.dk>
Date:   Mon, 11 Feb 2019 15:55:22 -0700
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On 2/11/19 3:50 AM, Martin Steigerwald wrote:
> Adding in axboe@kernel.dk, as I am not sure whether the oracle.com address
> from Jens is actually valid / up to date.
> 
> Domenico Andreoli - 11.02.19, 08:22:
>> On Mon, Feb 11, 2019 at 12:08:32AM +0100, Kristian Fiskerstrand wrote:
>> >
> Mit freundlichen Grüßen / With kind regards​
> 
> Martin Steigerwald	 • 
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> On 1/23/19 9:50 AM, Domenico Andreoli wrote:
>> > > Ben Finney <bignose@debian.org> writes:
>> > >> Domenico Andreoli <cavok@debian.org> writes:
>> [...]
>>
>> > >>> the only knot left is now the license of hash.h
>> > >>>
>> > >>> This file is also present in the kernel [0] with an updated copyright
>> > >>> but still without license.
>>
>> [...]
>>
>> > >> To know that work (that file) is free software, we need a clear grant
>> > >> of
>> > >> some specific license, for that work.
>> > >>
>> > >> If the work is not free, it would be incorrect to have the work in
>> > >> Debian.
>> > >
>> > > Is it possible that for the kernel it is instead correct because it is,
>> > > as whole, covered by its COPYING?
>> > >
>> > >> Alternatives, for complying with the Debian Free Software Guidelines
>> > >> with
>> > >> this package, include:
>> > >>
>> > >> * Find a credible grant of license under some GPL-compatible free
>> > >>
>> > >> license to that exact file. Document that explicit grant in the
>> > >> Debian
>> > >> package. This demonstrates the work is DFSG-free.
>> > >>
>> > >> * Convince ???dwarves-dfsg??? upstream to replace that file with a
>> > >> different> >>
>> > >> implementation (I don't know whether such an implementation exists)
>> > >> under a license compatible with the same version of GNU GPL. Document
>> > >> that explicit grant in the Debian package. This demonstrates the
>> > >> modified work is DFSG-free.
>> > >>
>> > >> * Replace that file in Debian only, with a different implementation as
>> > >>
>> > >> above. Document that explicit grant in the Debian package. This
>> > >> demonstrates the modified Debian package is DFSG-free.
>> > >>
>> > >> * Move the work to the ???non-free??? area.
>> > >>
>> > >> * Remove the work altogether.
>> > >>
>> > >> Those are in descending order of (my recommended) preference.
>>
>> [...]
>>
>> > It was [pointed out] by one of our license group that [hash.h] is the
>> > same that has a GPL-2+ in [fio] which has a signed-off-by.
>> >
>> > References:
>> > [pointed out]
>> > https://bugs.gentoo.org/677586#c1
>> >
>> > [hash.h]
>> > https://git.kernel.org/pub/scm/linux/kernel/git/axboe/fio.git/commit/hash.
>> > h?id=bdc7211e190482f0c17c109a0d90834a6611be1c
>> Yes, the Signed-off-by is from Jens Axboe (in CC) but he's not the
>> original author, I guess he just copied the file as Arnaldo did. The
>> file he committed has not any reference to the license.
>>
>> > [fio]
>> > https://metadata.ftp-master.debian.org/changelogs/main/f/fio/fio_3.12-2_co
>> > pyright
>> I'm afraid that this entry in wrong. I'll seek confirmation with Martin
>> Steigerwald.
> 
> Which entry to you refer to? I assume the one about hash.h.
> 
> Well the file has in its header:
> 
> /* Fast hashing routine for a long.
> (C) 2002 William Lee Irwin III, IBM */
> 
> /*
> * Knuth recommends primes in approximately golden ratio to the maximum
> * integer representable by a machine word for multiplicative hashing.
> * Chuck Lever verified the effectiveness of this technique:
> * http://www.citi.umich.edu/techreports/reports/citi-tr-00-1.pdf
> *
> * These primes are chosen to be bit-sparse, that is operations on
> * them can use shifts and additions instead of multiplications for
> * machines where multiplications are slow.
> */
> 
> It has been quite a while ago. I bet back then I did not regard this as
> license information since it does not specify a license. Thus I assumed it to
> be GPL-2 as the other files which have no license boiler plate. I.e.: Check file
> is it has different license, if not, then assume it has license as specified in
> COPYING.
> 
> Not specifying a license can however also mean in this context that it has no
> license as the file contains copyright information from another author.
> 
> Of course I can update copyright file in case my conclusion from a long time
> ago was wrong.
> 
> Jens?

Right, if nothing else is noted, it's GPL v2.

-- 
Jens Axboe