The comments are spot on and should be near the central API, not just near a single implementation. Signed-off-by: Christoph Hellwig <hch@xxxxxx> --- arch/arm/mm/dma-mapping.c | 11 ----------- kernel/dma/mapping.c | 11 +++++++++++ 2 files changed, 11 insertions(+), 11 deletions(-) diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c index ad64d32fb39a..b4d65da76393 100644 --- a/arch/arm/mm/dma-mapping.c +++ b/arch/arm/mm/dma-mapping.c @@ -880,17 +880,6 @@ static void arm_coherent_dma_free(struct device *dev, size_t size, void *cpu_add __arm_dma_free(dev, size, cpu_addr, handle, attrs, true); } -/* - * The whole dma_get_sgtable() idea is fundamentally unsafe - it seems - * that the intention is to allow exporting memory allocated via the - * coherent DMA APIs through the dma_buf API, which only accepts a - * scattertable. This presents a couple of problems: - * 1. Not all memory allocated via the coherent DMA APIs is backed by - * a struct page - * 2. Passing coherent DMA memory into the streaming APIs is not allowed - * as we will try to flush the memory through a different alias to that - * actually being used (and the flushes are redundant.) - */ int arm_dma_get_sgtable(struct device *dev, struct sg_table *sgt, void *cpu_addr, dma_addr_t handle, size_t size, unsigned long attrs) diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c index 9c0f6a8eb5cb..41590d003465 100644 --- a/kernel/dma/mapping.c +++ b/kernel/dma/mapping.c @@ -136,6 +136,17 @@ int dma_common_get_sgtable(struct device *dev, struct sg_table *sgt, return ret; } +/* + * The whole dma_get_sgtable() idea is fundamentally unsafe - it seems + * that the intention is to allow exporting memory allocated via the + * coherent DMA APIs through the dma_buf API, which only accepts a + * scattertable. This presents a couple of problems: + * 1. Not all memory allocated via the coherent DMA APIs is backed by + * a struct page + * 2. Passing coherent DMA memory into the streaming APIs is not allowed + * as we will try to flush the memory through a different alias to that + * actually being used (and the flushes are redundant.) + */ int dma_get_sgtable_attrs(struct device *dev, struct sg_table *sgt, void *cpu_addr, dma_addr_t dma_addr, size_t size, unsigned long attrs) -- 2.20.1
