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From:   Marek Szyprowski <m.szyprowski@samsung.com>
To:     dri-devel@lists.freedesktop.org, iommu@lists.linux-foundation.org,
        linaro-mm-sig@lists.linaro.org, linux-kernel@vger.kernel.org
Cc:     Marek Szyprowski <m.szyprowski@samsung.com>,
        Christoph Hellwig <hch@lst.de>,
        Robin Murphy <robin.murphy@arm.com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
        linux-arm-kernel@lists.infradead.org,
        David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>, Arnd Bergmann <arnd@arndb.de>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Subject: [PATCH v3 22/25] misc: fastrpc: fix common struct sg_table related
 issues
Date:   Tue,  5 May 2020 10:46:11 +0200
Message-Id: <20200505084614.30424-22-m.szyprowski@samsung.com>
In-Reply-To: <20200505084614.30424-1-m.szyprowski@samsung.com>
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References: <20200505083926.28503-1-m.szyprowski@samsung.com>
        <20200505084614.30424-1-m.szyprowski@samsung.com>
        <CGME20200505084637eucas1p20390fa3c010bde00e438cce1b48d209c@eucas1p2.samsung.com>
Sender: linux-kernel-owner@vger.kernel.org
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The Documentation/DMA-API-HOWTO.txt states that dma_map_sg returns the
numer of the created entries in the DMA address space. However the
subsequent calls to dma_sync_sg_for_{device,cpu} and dma_unmap_sg must be
called with the original number of the entries passed to dma_map_sg. The
sg_table->nents in turn holds the result of the dma_map_sg call as stated
in include/linux/scatterlist.h. A common mistake was to ignore a result
of the dma_map_sg function and don't use the sg_table->orig_nents at all.

To avoid such issues, lets use common dma-mapping wrappers operating
directly on the struct sg_table objects and adjust references to the
nents and orig_nents respectively.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
---
For more information, see '[PATCH v3 00/25] DRM: fix struct sg_table nents
vs. orig_nents misuse' thread: https://lkml.org/lkml/2020/5/5/187
---
 drivers/misc/fastrpc.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
index e3e085e..0a3e02aa 100644
--- a/drivers/misc/fastrpc.c
+++ b/drivers/misc/fastrpc.c
@@ -518,7 +518,7 @@ static struct fastrpc_invoke_ctx *fastrpc_context_alloc(
 
 	table = &a->sgt;
 
-	if (!dma_map_sg(attachment->dev, table->sgl, table->nents, dir))
+	if (!dma_map_sgtable(attachment->dev, table, dir))
 		return ERR_PTR(-ENOMEM);
 
 	return table;
@@ -528,7 +528,7 @@ static void fastrpc_unmap_dma_buf(struct dma_buf_attachment *attach,
 				  struct sg_table *table,
 				  enum dma_data_direction dir)
 {
-	dma_unmap_sg(attach->dev, table->sgl, table->nents, dir);
+	dma_unmap_sgtable(attach->dev, table, dir);
 }
 
 static void fastrpc_release(struct dma_buf *dmabuf)
-- 
1.9.1