diff options
author | FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp> | 2008-12-01 16:14:01 -0500 |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2008-12-01 22:55:24 -0500 |
commit | 1d678f365dae28420fa7329a2a35390b3582678d (patch) | |
tree | 84b6e574a4d913dd2abe59f052b5848424e4ce38 | |
parent | 4280e3126f641898f0ed1a931645373d3489e2a6 (diff) |
DMA-API.txt: fix description of pci_map_sg/dma_map_sg scatterlists handling
- pci_map_sg/dma_map_sg are used with a scatter gather list that doesn't
come from the block layer (e.g. some network drivers do).
- how IOMMUs merge adjacent elements of the scatter/gather list is
independent of how the block layer determines sees elements.
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: Tejun Heo <htejun@gmail.com>
Cc: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r-- | Documentation/DMA-API.txt | 8 |
1 files changed, 3 insertions, 5 deletions
diff --git a/Documentation/DMA-API.txt b/Documentation/DMA-API.txt index b8e86460046e..b462bb149543 100644 --- a/Documentation/DMA-API.txt +++ b/Documentation/DMA-API.txt | |||
@@ -316,12 +316,10 @@ reduce current DMA mapping usage or delay and try again later). | |||
316 | pci_map_sg(struct pci_dev *hwdev, struct scatterlist *sg, | 316 | pci_map_sg(struct pci_dev *hwdev, struct scatterlist *sg, |
317 | int nents, int direction) | 317 | int nents, int direction) |
318 | 318 | ||
319 | Maps a scatter gather list from the block layer. | ||
320 | |||
321 | Returns: the number of physical segments mapped (this may be shorter | 319 | Returns: the number of physical segments mapped (this may be shorter |
322 | than <nents> passed in if the block layer determines that some | 320 | than <nents> passed in if some elements of the scatter/gather list are |
323 | elements of the scatter/gather list are physically adjacent and thus | 321 | physically or virtually adjacent and an IOMMU maps them with a single |
324 | may be mapped with a single entry). | 322 | entry). |
325 | 323 | ||
326 | Please note that the sg cannot be mapped again if it has been mapped once. | 324 | Please note that the sg cannot be mapped again if it has been mapped once. |
327 | The mapping process is allowed to destroy information in the sg. | 325 | The mapping process is allowed to destroy information in the sg. |