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| author | Christoph Hellwig <hch@lst.de> | 2019-03-15 17:56:43 +0100 |
|---|---|---|
| committer | Christoph Hellwig <hch@lst.de> | 2019-09-04 11:13:17 +0200 |
| commit | 14451467014b4c8aff6570b44b6d0ee68cd49bc0 (patch) | |
| tree | 66eec34dfcf1db31d85ebc9b1387e4ec43fe8a58 /kernel/dma/mapping.c | |
| parent | dma-mapping: fix filename references (diff) | |
| download | linux-14451467014b4c8aff6570b44b6d0ee68cd49bc0.tar.xz linux-14451467014b4c8aff6570b44b6d0ee68cd49bc0.zip | |
dma-mapping: move the dma_get_sgtable API comments from arm to common code
The comments are spot on and should be near the central API, not just
near a single implementation.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Diffstat (limited to 'kernel/dma/mapping.c')
| -rw-r--r-- | kernel/dma/mapping.c | 11 |
1 files changed, 11 insertions, 0 deletions
diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c index 72c825c1788e..a136932b8e6d 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) |