From: Herbert Xu <herbert@gondor.apana.org.au>
Subject: Re: [PATCH v5 05/14] crypto: marvell/CESA: add TDMA support
Date: Wed, 17 Jun 2015 13:56:33 +0800
Message-ID: <20150617055633.GA9123@gondor.apana.org.au>
References: <1434448748-10828-1-git-send-email-boris.brezillon@free-electrons.com>
 <1434448748-10828-6-git-send-email-boris.brezillon@free-electrons.com>
 <20150617050527.GA8807@gondor.apana.org.au>
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Cc: "David S. Miller" <davem@davemloft.net>,
	linux-crypto@vger.kernel.org, Arnaud Ebalard <arno@natisbad.org>,
	Tawfik Bayouk <tawfik@marvell.com>,
	Lior Amsalem <alior@marvell.com>,
	Nadav Haklai <nadavh@marvell.com>,
	Eran Ben-Avi <benavi@marvell.com>,
	Thomas Petazzoni <thomas.petazzoni@free-electrons.com>,
	Gregory CLEMENT <gregory.clement@free-electrons.com>,
	Jason Cooper <jason@lakedaemon.net>,
	Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>,
	Andrew Lunn <andrew@lunn.ch>, Rob Herring <robh+dt@kernel.org>,
	Pawel Moll <pawel.moll@arm.com>,
	Mark Rutland <mark.rutland@arm.com>,
	Ian Campbell <ijc+devicetree@hellion.org.uk>,
	Kumar Gala <galak@codeaurora.org>, devicetree@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
	Jason Gunthorpe <jgunthorpe@obsidianresearch.com>,
	Imre Kaloz <kaloz@openwrt.org>
To: Boris Brezillon <boris.brezillon@free-electrons.com>
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In-Reply-To: <20150617050527.GA8807@gondor.apana.org.au>
Sender: linux-crypto-owner@vger.kernel.org

On Wed, Jun 17, 2015 at 01:05:27PM +0800, Herbert Xu wrote:
> On Tue, Jun 16, 2015 at 11:58:59AM +0200, Boris Brezillon wrote:
> >
> > +	ret = dma_map_sg(cesa_dev->dev, req->src, creq->src_nents,
> > +			 DMA_TO_DEVICE);
> > +	if (ret != creq->src_nents)
> > +		return -ENOMEM;
> 
> Hmm it doesn't quite work like that.  It returns zero on error,
> otherwise it returns the number (n) of mapped entries which may be
> less than what you gave it due to merging.  You're then supposed
> to use only the first n entries which should contain everything.

Please take a look at Documentation/DMA-API-HOWTO.txt, it has
everything you need to know about the dma_map_sg interface.

Cheers,
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt