linux-kernel - [PATCH v3 21/25] staging: tegra-vde: fix common struct sg

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Date:   Tue,  5 May 2020 10:46:10 +0200
From:   Marek Szyprowski <m.szyprowski@...sung.com>
To:     dri-devel@...ts.freedesktop.org, iommu@...ts.linux-foundation.org,
        linaro-mm-sig@...ts.linaro.org, linux-kernel@...r.kernel.org
Cc:     Marek Szyprowski <m.szyprowski@...sung.com>,
        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>,
        Dmitry Osipenko <digetx@...il.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        linux-media@...r.kernel.org, linux-tegra@...r.kernel.org,
        devel@...verdev.osuosl.org
Subject: [PATCH v3 21/25] staging: tegra-vde: fix common struct sg_table
 related issues

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@...sung.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/staging/media/tegra-vde/iommu.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/staging/media/tegra-vde/iommu.c b/drivers/staging/media/tegra-vde/iommu.c
index 6af863d..adf8dc7 100644
--- a/drivers/staging/media/tegra-vde/iommu.c
+++ b/drivers/staging/media/tegra-vde/iommu.c
@@ -36,8 +36,8 @@ int tegra_vde_iommu_map(struct tegra_vde *vde,
 
 	addr = iova_dma_addr(&vde->iova, iova);
 
-	size = iommu_map_sg(vde->domain, addr, sgt->sgl, sgt->nents,
-			    IOMMU_READ | IOMMU_WRITE);
+	size = iommu_map_sgtable(vde->domain, addr, sgt,
+				 IOMMU_READ | IOMMU_WRITE);
 	if (!size) {
 		__free_iova(&vde->iova, iova);
 		return -ENXIO;
-- 
1.9.1