On Monday 20 June 2011, Marek Szyprowski wrote:
This patch modifies dma-mapping implementation on ARM architecture to use common dma_map_ops structure and asm-generic/dma-mapping-common.h helpers.
Signed-off-by: Marek Szyprowski m.szyprowski@samsung.com Signed-off-by: Kyungmin Park kyungmin.park@samsung.com
This is a good idea in general, but I have a few concerns about details:
First of all, should we only allow using dma_map_ops on ARM, or do we also want to support a case where these are all inlined as before?
I suppose for the majority of the cases, the overhead of the indirect function call is near-zero, compared to the overhead of the cache management operation, so it would only make a difference for coherent systems without an IOMMU. Do we care about micro-optimizing those?
diff --git a/arch/arm/include/asm/dma-mapping.h b/arch/arm/include/asm/dma-mapping.h index 799669d..f4e4968 100644 --- a/arch/arm/include/asm/dma-mapping.h +++ b/arch/arm/include/asm/dma-mapping.h @@ -10,6 +10,27 @@ #include <asm-generic/dma-coherent.h> #include <asm/memory.h> +extern struct dma_map_ops dma_ops;
+static inline struct dma_map_ops *get_dma_ops(struct device *dev) +{
- if (dev->archdata.dma_ops)
return dev->archdata.dma_ops;- return &dma_ops;
+}
I would not name the global structure just 'dma_ops', the identifier could too easily conflict with a local variable in some driver. How about arm_dma_ops or linear_dma_ops instead?
/*
- The scatter list versions of the above methods.
*/ -extern int dma_map_sg(struct device *, struct scatterlist *, int,
enum dma_data_direction);-extern void dma_unmap_sg(struct device *, struct scatterlist *, int, +extern int arm_dma_map_sg(struct device *, struct scatterlist *, int,
enum dma_data_direction, struct dma_attrs *attrs);+extern void arm_dma_unmap_sg(struct device *, struct scatterlist *, int,
enum dma_data_direction, struct dma_attrs *attrs);+extern void arm_dma_sync_sg_for_cpu(struct device *, struct scatterlist *, int, enum dma_data_direction); -extern void dma_sync_sg_for_cpu(struct device *, struct scatterlist *, int, +extern void arm_dma_sync_sg_for_device(struct device *, struct scatterlist *, int, enum dma_data_direction); -extern void dma_sync_sg_for_device(struct device *, struct scatterlist *, int,
enum dma_data_direction);
You should not need to make these symbols visible in the header file any more unless they are used outside of the main file later.
Arnd