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/rapidio/devices/rio_mport_cdev.c | 8 +++-----
1 file changed, 3 insertions(+), 5 deletions(-)
diff --git a/drivers/rapidio/devices/rio_mport_cdev.c b/drivers/rapidio/devices/rio_mport_cdev.c
index 4029637..df7dba8 100644
--- a/drivers/rapidio/devices/rio_mport_cdev.c
+++ b/drivers/rapidio/devices/rio_mport_cdev.c
@@ -574,8 +574,7 @@ static void dma_req_free(struct kref *ref)
struct mport_cdev_priv *priv = req->priv;
unsigned int i;
- dma_unmap_sg(req->dmach->device->dev,
- req->sgt.sgl, req->sgt.nents, req->dir);
+ dma_unmap_sgtable(req->dmach->device->dev, req->sgt, req->dir);
sg_free_table(&req->sgt);
if (req->page_list) {
for (i = 0; i < req->nr_pages; i++)
@@ -927,9 +926,8 @@ static int do_dma_request(struct mport_dma_req *req,
xfer->offset, xfer->length);
}
- nents = dma_map_sg(chan->device->dev,
- req->sgt.sgl, req->sgt.nents, dir);
- if (nents == 0) {
+ ret = dma_map_sgtable(chan->device->dev, req->sgt, dir);
+ if (ret) {
rmcd_error("Failed to map SG list");
ret = -EFAULT;
goto err_pg;
--
1.9.1
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