On 30/11/2018 13:22, Christoph Hellwig wrote:
Error handling of the dma_map_single and dma_map_page APIs is a little
problematic at the moment, in that we use different encodings in the
returned dma_addr_t to indicate an error. That means we require an
additional indirect call to figure out if a dma mapping call returned
an error, and a lot of boilerplate code to implement these semantics.
Instead return the maximum addressable value as the error. As long
as we don't allow mapping single-byte ranges with single-byte alignment
this value can never be a valid return. Additionaly if drivers do
not check the return value from the dma_map* routines this values means
they will generally not be pointed to actual memory.
Once the default value is added here we can start removing the
various mapping_error methods and just rely on this generic check.
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
include/linux/dma-mapping.h | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index 0f81c713f6e9..46bd612d929e 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -133,6 +133,8 @@ struct dma_map_ops {
u64 (*get_required_mask)(struct device *dev);
};
+#define DMA_MAPPING_ERROR (~(dma_addr_t)0)
+
extern const struct dma_map_ops dma_direct_ops;
extern const struct dma_map_ops dma_virt_ops;
@@ -576,6 +578,10 @@ static inline int dma_mapping_error(struct device *dev, dma_addr_t dma_addr)
const struct dma_map_ops *ops = get_dma_ops(dev);
debug_dma_mapping_error(dev, dma_addr);
+
+ if (dma_addr == DMA_MAPPING_ERROR)
+ return 1;
+
if (ops->mapping_error)
return ops->mapping_error(dev, dma_addr);
return 0;
I'd have been inclined to put the default check here, i.e.
- return 0
+ return dma_addr == DMA_MAPPING_ERROR
such that the callback retains full precedence and we don't have to deal
with the non-trivial removals immediately if it comes to it. Not that it
makes a vast difference though, so either way,
Reviewed-by: Robin Murphy <robin.murphy@xxxxxxx>
