linux-kernel - Re: [PATCH v3 1/4] crypto: Add Allwinner Security System crypto accelerator

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Date:	Sun, 22 Jun 2014 13:33:35 +0100
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Marek Vasut <marex@...x.de>
Cc:	Corentin LABBE <clabbe.montjoie@...il.com>, robh+dt@...nel.org,
	pawel.moll@....com, mark.rutland@....com,
	ijc+devicetree@...lion.org.uk, galak@...eaurora.org,
	rdunlap@...radead.org, maxime.ripard@...e-electrons.com,
	herbert@...dor.apana.org.au, davem@...emloft.net,
	grant.likely@...aro.org, devicetree@...r.kernel.org,
	linux-doc@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org, linux-crypto@...r.kernel.org,
	linux-sunxi@...glegroups.com
Subject: Re: [PATCH v3 1/4] crypto: Add Allwinner Security System crypto
	accelerator

On Sun, Jun 22, 2014 at 02:23:15PM +0200, Marek Vasut wrote:
> On Sunday, June 22, 2014 at 01:58:08 PM, Corentin LABBE wrote:
> [...]
> > >> + * This program is free software; you can redistribute it and/or modify
> > >> + * it under the terms of the GNU General Public License as published by
> > >> + * the Free Software Foundation version 2 of the License
> > > 
> > > The license text seems incomplete.
> > > [...]
> > 
> > I will replace it with a simplier line "Licensed under the GPL-2."
> 
> I'd suggest you to use the SPDX license identifiers then, but that's not 
> something the kernel crowd agreed upon yet IIRC.Therefore , just make the text 
> complete please.

Marek,

The full text of the first paragraph (in COPYING) is:

    This program is free software; you can redistribute it and/or modify
    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.

which is deemed to be entirely sufficient; quoting the full text is
discouraged, especially when it includes the FSF address.  It is also
acceptable to restrict it to version 2 only, in which case something
like this can be used:

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License version 2 as
   published by the Free Software Foundation.

Of course, it's up to the author to make up their own mind at the end
of the day.

> Oh, ok, good question -- dear list, shall one use sg_page()+kmap or sg_virt()?

sg_page() + kmap() is preferred, because sg_virt() fails with highmem.
Using sg_virt() means you restrict the driver to non-highmem memory,
and if the kernel wants to place the data into a highmem page, it will
have to use bounce buffers (so it's inefficient).

What's even better is to use the scatterlist iterator, which will handle
this for you.  See the sg_miter_*() functions.

-- 
FTTC broadband for 0.8mile line: now at 9.7Mbps down 460kbps up... slowly
improving, and getting towards what was expected from it.
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