linux-kernel - Re: [PATCH v4 03/38] iommu: add generic helper for mapping sgtable objects

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Message-ID: <20200512121849.GC20393@lst.de>
Date:   Tue, 12 May 2020 14:18:49 +0200
From:   Christoph Hellwig <hch@....de>
To:     Marek Szyprowski <m.szyprowski@...sung.com>
Cc:     dri-devel@...ts.freedesktop.org, iommu@...ts.linux-foundation.org,
        linaro-mm-sig@...ts.linaro.org, linux-kernel@...r.kernel.org,
        Christoph Hellwig <hch@....de>,
        Robin Murphy <robin.murphy@....com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        linux-arm-kernel@...ts.infradead.org,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>, Joerg Roedel <joro@...tes.org>
Subject: Re: [PATCH v4 03/38] iommu: add generic helper for mapping sgtable
 objects

On Tue, May 12, 2020 at 11:00:23AM +0200, Marek Szyprowski wrote:
> struct sg_table is a common structure used for describing a memory
> buffer. It consists of a scatterlist with memory pages and DMA addresses
> (sgl entry), as well as the number of scatterlist entries: CPU pages
> (orig_nents entry) and DMA mapped pages (nents entry).
> 
> It turned out that it was a common mistake to misuse nents and orig_nents
> entries, calling mapping functions with a wrong number of entries.
> 
> To avoid such issues, lets introduce a common wrapper operating directly
> on the struct sg_table objects, which take care of the proper use of
> the nents and orig_nents entries.
> 
> Signed-off-by: Marek Szyprowski <m.szyprowski@...sung.com>

Looks good,

Reviewed-by: Christoph Hellwig <hch@....de>