linux-kernel - Re: [PATCH v6 05/14] crypto: marvell/CESA: add TDMA support

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Message-ID: <20150617133324.1ee6ad55@bbrezillon>
Date:	Wed, 17 Jun 2015 13:33:24 +0200
From:	Boris Brezillon <boris.brezillon@...e-electrons.com>
To:	Herbert Xu <herbert@...dor.apana.org.au>
Cc:	"David S. Miller" <davem@...emloft.net>,
	linux-crypto@...r.kernel.org, Arnaud Ebalard <arno@...isbad.org>,
	Tawfik Bayouk <tawfik@...vell.com>,
	Lior Amsalem <alior@...vell.com>,
	Nadav Haklai <nadavh@...vell.com>,
	Eran Ben-Avi <benavi@...vell.com>,
	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
	Gregory CLEMENT <gregory.clement@...e-electrons.com>,
	Jason Cooper <jason@...edaemon.net>,
	Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>,
	Andrew Lunn <andrew@...n.ch>, Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>, devicetree@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Jason Gunthorpe <jgunthorpe@...idianresearch.com>,
	Imre Kaloz <kaloz@...nwrt.org>
Subject: Re: [PATCH v6 05/14] crypto: marvell/CESA: add TDMA support

On Wed, 17 Jun 2015 17:50:01 +0800
Herbert Xu <herbert@...dor.apana.org.au> wrote:

> On Wed, Jun 17, 2015 at 09:45:33AM +0200, Boris Brezillon wrote:
> >
> > +	ret = dma_map_sg(cesa_dev->dev, req->src, creq->src_nents,
> > +			 DMA_TO_DEVICE);
> > +	if (!ret)
> > +		return -ENOMEM;
> > +
> > +	creq->src_nents = ret;
> 
> DMA-API-HOWTO says that you must retain the original nents and
> use it when you call dma_unmap_sg.  So I'm afraid one more repost
> is needed :)

My bad (again :-/).
Actually, I think I don't need to save the dma_map_sg return val, since
I'm using the sg_next function to iterate over the scatterlist. Am I
right ?
IOW, is the ->map_sg() function (in dma_map_ops) supposed to merge the
contiguous entries and then flag the unused entries with the is_chain
flag ?
If that's not the case, and the ->map_sg() just marks the merged entries
as empty (length = 0), then I'll have to rework my iterator algorithm.

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