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From: Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>
Date: Fri, 13 Feb 2015 16:47:36 +0100
Message-ID: <CAPybu_1fw6qEmeXPrJVsTAoiY5=athE6FaakXznnbzd7fE7shw@mail.gmail.com>
Subject: Re: [PATCH v2 1/3] media/videobuf2-dma-sg: Fix handling of sg_table structure
To: Hans Verkuil <hverkuil@xs4all.nl>
Cc: Pawel Osciak <pawel@osciak.com>,
        Marek Szyprowski <m.szyprowski@samsung.com>,
        Kyungmin Park <kyungmin.park@samsung.com>,
        Mauro Carvalho Chehab <mchehab@osg.samsung.com>,
        linux-media <linux-media@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Hans Verkuil <hans.verkuil@cisco.com>, martin.petersen@oracle.com,
        hch@lst.de, tonyb@cybernetics.com, axboe@fb.com,
        Stephen Rothwell <sfr@canb.auug.org.au>, lauraa@codeaurora.org,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>, webbnh@hp.com,
        hare@suse.de, Andrew Morton <akpm@linux-foundation.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Hello all

On Fri, Feb 13, 2015 at 4:32 PM, Hans Verkuil <hverkuil@xs4all.nl> wrote:

> Yes please. And if Ricardo is correct, then someone (janitor job?) should do
> a review of dma_unmap_sg in particular.

Perhaps a code snippet inside scatterlist.h will clarify even more.

Would any of the maintainers accept a patch to include a comment like:

struct sg_table *sgt;

sgt = kzalloc(sizeof(*sgt);
if (!sgt){
return -ENOMEM;
}

ret = sg_alloc_table(sgt, N_NENTS, GPF_KERNEL);
if (ret){
  kfree(sgt);
  return ret;
}

//Fill sgt using orig_nents or nents  as index

sgt->nents = dma_map_sg(dev, sgt->sgl, sgt->orig_nents, DIR);
if (!sgt->nents){
  sg_free_table(sgt);
  kfree(sgt);
  return -EIO;
}

//Use nent  as index

dma_unmap_sg(dev, sgt->sgl, sgt->orig_nents, DIR);
sg_free_table(sgt);
kfree(sgt);
return 0


Thanks!


-- 
Ricardo Ribalda
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