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/dma-buf/heaps/heap-helpers.c | 13 ++++++------- drivers/dma-buf/udmabuf.c | 7 +++---- 2 files changed, 9 insertions(+), 11 deletions(-)
diff --git a/drivers/dma-buf/heaps/heap-helpers.c b/drivers/dma-buf/heaps/heap-helpers.c index 9f964ca..be9523a 100644 --- a/drivers/dma-buf/heaps/heap-helpers.c +++ b/drivers/dma-buf/heaps/heap-helpers.c @@ -140,13 +140,12 @@ struct sg_table *dma_heap_map_dma_buf(struct dma_buf_attachment *attachment, enum dma_data_direction direction) { struct dma_heaps_attachment *a = attachment->priv; - struct sg_table *table; - - table = &a->table; + struct sg_table *table = &a->table; + int ret;
- if (!dma_map_sg(attachment->dev, table->sgl, table->nents, - direction)) - table = ERR_PTR(-ENOMEM); + ret = dma_map_sgtable(attachment->dev, table, direction); + if (ret) + table = ERR_PTR(ret); return table; }
@@ -154,7 +153,7 @@ static void dma_heap_unmap_dma_buf(struct dma_buf_attachment *attachment, struct sg_table *table, enum dma_data_direction direction) { - dma_unmap_sg(attachment->dev, table->sgl, table->nents, direction); + dma_unmap_sgtable(attachment->dev, table, direction); }
static vm_fault_t dma_heap_vm_fault(struct vm_fault *vmf) diff --git a/drivers/dma-buf/udmabuf.c b/drivers/dma-buf/udmabuf.c index acb26c6..5bcbf7a 100644 --- a/drivers/dma-buf/udmabuf.c +++ b/drivers/dma-buf/udmabuf.c @@ -63,10 +63,9 @@ static struct sg_table *get_sg_table(struct device *dev, struct dma_buf *buf, GFP_KERNEL); if (ret < 0) goto err; - if (!dma_map_sg(dev, sg->sgl, sg->nents, direction)) { - ret = -EINVAL; + ret = dma_map_sgtable(dev, sg, direction); + if (ret < 0) goto err; - } return sg;
err: @@ -78,7 +77,7 @@ static struct sg_table *get_sg_table(struct device *dev, struct dma_buf *buf, static void put_sg_table(struct device *dev, struct sg_table *sg, enum dma_data_direction direction) { - dma_unmap_sg(dev, sg->sgl, sg->nents, direction); + dma_unmap_sgtable(dev, sg, direction); sg_free_table(sg); kfree(sg); }