linux-kernel - Re: [PATCH 0/2] crypto: add new driver for Marvell CESA

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Date:	Fri, 17 Apr 2015 16:19:22 +0200
From:	Boris Brezillon <boris.brezillon@...e-electrons.com>
To:	Gregory CLEMENT <gregory.clement@...e-electrons.com>
Cc:	Jason Cooper <jason@...edaemon.net>,
	Arnaud Ebalard <arno@...isbad.org>,
	Mark Rutland <mark.rutland@....com>,
	Thomas Petazzoni <info@...e-electrons.com>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	Pawel Moll <pawel.moll@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Eran Ben-Avi <benavi@...vell.com>,
	Nadav Haklai <nadavh@...vell.com>, devicetree@...r.kernel.org,
	Rob Herring <robh+dt@...nel.org>, Andrew Lunn <andrew@...n.ch>,
	linux-crypto@...r.kernel.org, Kumar Gala <galak@...eaurora.org>,
	Tawfik Bayouk <tawfik@...vell.com>,
	"David S. Miller" <davem@...emloft.net>,
	Lior Amsalem <alior@...vell.com>,
	Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>
Subject: Re: [PATCH 0/2] crypto: add new driver for Marvell CESA

Hi Gregory,

On Fri, 17 Apr 2015 15:01:01 +0200
Gregory CLEMENT <gregory.clement@...e-electrons.com> wrote:

> Hi Boris,
> 
> On 17/04/2015 10:39, Boris Brezillon wrote:
> > On Fri, 17 Apr 2015 10:33:56 +0200
> > Boris Brezillon <boris.brezillon@...e-electrons.com> wrote:
> > 
> >> Hi Jason,
> >>
> >> On Mon, 13 Apr 2015 20:11:46 +0000
> >> Jason Cooper <jason@...edaemon.net> wrote:
> >>
> >>>>
> >>>>> I'd appreciate if we'd look into it.  I understand from on-list and
> >>>>> off-list discussion that the rewrite was unavoidable.  So I'm willing to
> >>>>> concede that.  Giving people time to migrate from old to new while still
> >>>>> being able to update for other security fixes seems reasonable.
> >>>>
> >>>> Jason, what do you think of the approach above? 
> >>>
> >>> I say keep it simple.  We shouldn't use the DT changes to trigger one
> >>> vice the other.  We need to be able to build both, but only load one at
> >>> a time.  If that's anything other than simple to do, then we make it a
> >>> Kconfig binary choice and move on.
> >>
> >> Actually I was planning to handle it with a Kconfig dependency rule
> >> (NEW_DRIVER depends on !OLD_DRIVER and OLD_DRIVER depends
> >> on !NEW_DRIVER).
> >> I don't know how to make it a runtime check without adding new
> >> compatible strings for the kirkwood, dove and orion platforms, and I'm
> >> sure sure this is a good idea.
> >   ^ not
> > 
> >> Do you have any ideas ?
> 
> You use devm_ioremap_resource() in the new driver, so if the old one
> is already loaded the memory region will be already hold and the new
> driver will simply fail during the probe. So for this part it is OK.

I like the idea :-).

> 
> However, the old driver doesn't try to reserve the region, it directly
> uses an ioremap(). So if the new driver is loaded first, then the old
> one will manage to be loaded too. I think that just adding a
> request_region()/release_region() (or converting the ioremap in a
> devm_ioremap_resource() in the old driver would be enough.

Absolutely. Unless someone is opposed to this solution I think I'll
choose this solution.

Thanks,

Boris


-- 
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com
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