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From:   Ard Biesheuvel <ardb@kernel.org>
Date:   Fri, 23 Jun 2023 20:37:58 +0200
Message-ID: <CAMj1kXH=oJMO-j=rdbGuEu2ntz1DeXu2cYL8utm25OUhnrpm2Q@mail.gmail.com>
Subject: Re: [PATCH 2/3] crypto: arm - add some missing SPDX headers
To:     Richard Fontana <rfontana@redhat.com>
Cc:     Bagas Sanjaya <bagasdotme@gmail.com>, linux-crypto@vger.kernel.org,
        herbert@gondor.apana.org.au, ebiggers@kernel.org
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On Tue, 20 Jun 2023 at 05:50, Richard Fontana <rfontana@redhat.com> wrote:
>
> On Sat, Jun 10, 2023 at 3:31=E2=80=AFAM Bagas Sanjaya <bagasdotme@gmail.c=
om> wrote:
> >
> > [also Cc'ing Richard]
> >
> > On Tue, Jun 06, 2023 at 07:31:26PM +0200, Ard Biesheuvel wrote:
> > > Add some missing SPDX headers, and drop the associated boilerplate
> > > license text to/from the ARM implementations of ChaCha, CRC-32 and
> > > CRC-T10DIF.
> > >
> > > Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> > > ---
> > >  arch/arm/crypto/chacha-neon-core.S  | 10 +----
> > >  arch/arm/crypto/crc32-ce-core.S     | 30 ++-------------
> > >  arch/arm/crypto/crct10dif-ce-core.S | 40 +-------------------
> > >  3 files changed, 5 insertions(+), 75 deletions(-)
> > >
> > > diff --git a/arch/arm/crypto/chacha-neon-core.S b/arch/arm/crypto/cha=
cha-neon-core.S
> > > index 13d12f672656bb8d..46d708118ef948ec 100644
> > > --- a/arch/arm/crypto/chacha-neon-core.S
> > > +++ b/arch/arm/crypto/chacha-neon-core.S
> > > @@ -1,21 +1,13 @@
> > > +/* SPDX-License-Identifier: GPL-2.0-only */
> > >  /*
> > >   * ChaCha/XChaCha NEON helper functions
> > >   *
> > >   * Copyright (C) 2016 Linaro, Ltd. <ard.biesheuvel@linaro.org>
> > >   *
> > > - * This program is free software; you can redistribute it and/or mod=
ify
> > > - * it under the terms of the GNU General Public License version 2 as
> > > - * published by the Free Software Foundation.
> > > - *
> > >   * Based on:
> > >   * ChaCha20 256-bit cipher algorithm, RFC7539, x64 SSE3 functions
> > >   *
> > >   * Copyright (C) 2015 Martin Willi
> > > - *
> > > - * This program is free software; you can redistribute it and/or mod=
ify
> > > - * it under the terms of the GNU General Public License as published=
 by
> > > - * the Free Software Foundation; either version 2 of the License, or
> > > - * (at your option) any later version.
> > >   */
> >
> > I think above makes sense, since I had to pick the most restrictive one
> > to satisfy both license option (GPL-2.0+ or GPL-2.0-only).
>
> I am not sure "had to pick the most restrictive one" is necessarily
> correct - the kernel could adopt that approach but I don't think
> there's any reason why you can't have multiple
> SPDX-License-Identifier: lines in a single source file, and it is also
> syntactically valid to use
> SPDX-License-Identifier: GPL-2.0-only AND GPL-2.0-or-later
>

For the record, my reasoning was that my code (which is a rewrite of
the algorithm using a completely different ISA) is the derived work,
and I am permitted to exercise my right granted by the original work
to redistribute it under the GPLv2. So this is why the 'outer' license
(as well a the SPDX header) is GPLv2 only.

I didn't expect there to be a requirement for SPDX to describe the
original licenses of all the constituent parts.

In any case, I am going to take Greg's advice and not pursue this any
further - if anyone needs this cleaned up, they can do it themselves.

Thanks for the education on this topic, I'll know better next time :-)