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asm/dma-mapping-common: Clarify output of dma_map_sg_attrs

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Although dma_map_sg_attrs returns 0 on error and it cannot return a
value < 0, the function returns a signed integer.

Most of the time, this function is used with a scatterlist structure.
This structure uses an unsigned integer for the number of memory.

A dma developer that has not read in detail DMA-API.txt, can wrongly
return a value < 0 on error.

The comment will help the driver developer, and the WARN_ON the dma
developer.

Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
This commit is contained in:
Ricardo Ribalda Delgado 2015-02-11 13:53:14 +01:00 committed by Marek Szyprowski
parent 9eccca0843
commit 8582e267e9
1 changed files with 5 additions and 0 deletions
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5
include/asm-generic/dma-mapping-common.h
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@ -39,6 +39,10 @@ static inline void dma_unmap_single_attrs(struct device *dev, dma_addr_t addr,
debug_dma_unmap_page(dev, addr, size, dir, true);
}
/*
* dma_maps_sg_attrs returns 0 on error and > 0 on success.
* It should never return a value < 0.
*/
static inline int dma_map_sg_attrs(struct device *dev, struct scatterlist *sg,
int nents, enum dma_data_direction dir,
struct dma_attrs *attrs)
@ -51,6 +55,7 @@ static inline int dma_map_sg_attrs(struct device *dev, struct scatterlist *sg,
kmemcheck_mark_initialized(sg_virt(s), s->length);
BUG_ON(!valid_dma_direction(dir));
ents = ops->map_sg(dev, sg, nents, dir, attrs);
BUG_ON(ents < 0);
debug_dma_map_sg(dev, sg, nents, ents, dir);
return ents;