[v2,15/21] drm: xen: fix sg_table nents vs. orig_nents misuse

Message ID 20200504125359.5678-15-m.szyprowski@samsung.com
State New
Headers show
  • DRM: fix struct sg_table nents vs. orig_nents misuse
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Commit Message

Marek Szyprowski May 4, 2020, 12:53 p.m.
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 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. Adapt the code to obey those rules.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>

For more information, see '[PATCH v2 00/21] DRM: fix struct sg_table nents
vs. orig_nents misuse' thread: https://lkml.org/lkml/2020/5/4/373
 drivers/gpu/drm/xen/xen_drm_front_gem.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)


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diff --git a/drivers/gpu/drm/xen/xen_drm_front_gem.c b/drivers/gpu/drm/xen/xen_drm_front_gem.c
index f0b85e0..ba4bdc5 100644
--- a/drivers/gpu/drm/xen/xen_drm_front_gem.c
+++ b/drivers/gpu/drm/xen/xen_drm_front_gem.c
@@ -215,7 +215,7 @@  struct drm_gem_object *
 		return ERR_PTR(ret);
 	DRM_DEBUG("Imported buffer of size %zu with nents %u\n",
-		  size, sgt->nents);
+		  size, sgt->orig_nents);
 	return &xen_obj->base;