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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,
Cc: Marek Szyprowski <m.szyprowski@samsung.com>,
	Christoph Hellwig <hch@lst.de>,
	Robin Murphy <robin.murphy@arm.com>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
	David Airlie <airlied@linux.ie>, Daniel Vetter <daniel@ffwll.ch>,
	Dmitry Osipenko <digetx@gmail.com>,
	Mauro Carvalho Chehab <mchehab@kernel.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Thierry Reding <thierry.reding@gmail.com>,
	Jonathan Hunter <jonathanh@nvidia.com>,
	linux-media@vger.kernel.org, linux-tegra@vger.kernel.org,
Subject: [PATCH v7 31/36] staging: tegra-vde: fix common struct sg_table related issues
Date: Fri, 19 Jun 2020 12:36:31 +0200
Message-ID: <20200619103636.11974-32-m.szyprowski@samsung.com> (raw)
In-Reply-To: <20200619103636.11974-1-m.szyprowski@samsung.com>

The Documentation/DMA-API-HOWTO.txt states that the dma_map_sg() function
returns the number of the created entries in the DMA address space.
However the subsequent calls to the dma_sync_sg_for_{device,cpu}() and
dma_unmap_sg must be called with the original number of the entries
passed to the dma_map_sg().

struct sg_table is a common structure used for describing a non-contiguous
memory buffer, used commonly in the DRM and graphics subsystems. 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 DMA-mapping functions with a wrong number of entries or
ignoring the number of mapped entries returned by the dma_map_sg()

To avoid such issues, lets use a common dma-mapping wrappers operating
directly on the struct sg_table objects and use scatterlist page
iterators where possible. This, almost always, hides references to the
nents and orig_nents entries, making the code robust, easier to follow
and copy/paste safe.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Dmitry Osipenko <digetx@gmail.com>
 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 6af863d92123..adf8dc7ee25c 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,
+	size = iommu_map_sgtable(vde->domain, addr, sgt,
 	if (!size) {
 		__free_iova(&vde->iova, iova);
 		return -ENXIO;

  parent reply	other threads:[~2020-06-19 10:42 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20200619103636.11974-1-m.szyprowski@samsung.com>
     [not found] ` <CGME20200619103711eucas1p188e07cb9aaad13d39238aac4fe84b10c@eucas1p1.samsung.com>
2020-06-19 10:36   ` [PATCH v7 27/36] drm: rcar-du: " Marek Szyprowski
     [not found] ` <CGME20200619103714eucas1p18db6efd1a380fc0bdb16174ee85036fa@eucas1p1.samsung.com>
2020-06-19 10:36   ` Marek Szyprowski [this message]
2020-06-20 21:10     ` [PATCH v7 31/36] staging: tegra-vde: " kernel test robot
2020-06-21  4:00     ` Dmitry Osipenko
2020-06-30 10:07       ` Marek Szyprowski
2020-07-01  1:45         ` Dmitry Osipenko
     [not found] ` <CGME20200619103717eucas1p23b82366794c92cc70c0492e4ca29c4a1@eucas1p2.samsung.com>
2020-06-19 10:36   ` [PATCH v7 35/36] media: pci: fix common ALSA DMA-mapping related codes Marek Szyprowski
     [not found] ` <CGME20200619103718eucas1p11cd577b435672197f48bfcba2d06bc18@eucas1p1.samsung.com>
2020-06-19 10:36   ` [PATCH v7 36/36] videobuf2: use sgtable-based scatterlist wrappers Marek Szyprowski
     [not found]     ` <CGME20200630104527eucas1p13f19c24ff053556fb1fa7dc72be14c77@eucas1p1.samsung.com>
2020-06-30 10:45       ` [PATCH v8] " Marek Szyprowski

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