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@xxxxxxxxxxx>
---
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/gpu/drm/armada/armada_gem.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)
diff --git a/drivers/gpu/drm/armada/armada_gem.c b/drivers/gpu/drm/armada/armada_gem.c
index 976685f..5b4f48c 100644
--- a/drivers/gpu/drm/armada/armada_gem.c
+++ b/drivers/gpu/drm/armada/armada_gem.c
@@ -407,8 +407,8 @@ int armada_gem_pwrite_ioctl(struct drm_device *dev, void *data,
sg_set_page(sg, page, PAGE_SIZE, 0);
}
- if (dma_map_sg(attach->dev, sgt->sgl, sgt->nents, dir) == 0) {
- num = sgt->nents;
+ if (dma_map_sgtable(attach->dev, sgt, dir)) {
+ num = count;
goto release;
}
} else if (dobj->page) {
@@ -418,7 +418,7 @@ int armada_gem_pwrite_ioctl(struct drm_device *dev, void *data,
sg_set_page(sgt->sgl, dobj->page, dobj->obj.size, 0);
- if (dma_map_sg(attach->dev, sgt->sgl, sgt->nents, dir) == 0)
+ if (dma_map_sgtable(attach->dev, sgt, dir))
goto free_table;
} else if (dobj->linear) {
/* Single contiguous physical region - no struct page */
@@ -449,11 +449,11 @@ static void armada_gem_prime_unmap_dma_buf(struct dma_buf_attachment *attach,
int i;
if (!dobj->linear)
- dma_unmap_sg(attach->dev, sgt->sgl, sgt->nents, dir);
+ dma_unmap_sgtable(attach->dev, sgt, dir);
if (dobj->obj.filp) {
struct scatterlist *sg;
- for_each_sg(sgt->sgl, sg, sgt->nents, i)
+ for_each_sg(sgt->sgl, sg, sgt->orig_nents, i)
put_page(sg_page(sg));
}
--
1.9.1
_______________________________________________
dri-devel mailing list
dri-devel@xxxxxxxxxxxxxxxxxxxxx
https://lists.freedesktop.org/mailman/listinfo/dri-devel
