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[linux-2.6-omap-h63xx.git] / Documentation / DMA-API.txt

diff --git a/Documentation/DMA-API.txt b/Documentation/DMA-API.txt
index b8e86460046e7ee3dba003c12de57ae2d6f7fb36..52441694fe039abca40fd83217a82fa88aca4176 100644 (file)
--- a/Documentation/DMA-API.txt
+++ b/Documentation/DMA-API.txt
@@ -170,16 +170,15 @@ Returns: 0 if successful and a negative error if not.
 u64
 dma_get_required_mask(struct device *dev)
 
-After setting the mask with dma_set_mask(), this API returns the
-actual mask (within that already set) that the platform actually
-requires to operate efficiently.  Usually this means the returned mask
+This API returns the mask that the platform requires to
+operate efficiently.  Usually this means the returned mask
 is the minimum required to cover all of memory.  Examining the
 required mask gives drivers with variable descriptor sizes the
 opportunity to use smaller descriptors as necessary.
 
 Requesting the required mask does not alter the current mask.  If you
-wish to take advantage of it, you should issue another dma_set_mask()
-call to lower the mask again.
+wish to take advantage of it, you should issue a dma_set_mask()
+call to set the mask to the value returned.
 
 
 Part Id - Streaming DMA mappings
@@ -316,12 +315,10 @@ reduce current DMA mapping usage or delay and try again later).
        pci_map_sg(struct pci_dev *hwdev, struct scatterlist *sg,
                int nents, int direction)
 
-Maps a scatter gather list from the block layer.
-
 Returns: the number of physical segments mapped (this may be shorter
-than <nents> passed in if the block layer determines that some
-elements of the scatter/gather list are physically adjacent and thus
-may be mapped with a single entry).
+than <nents> passed in if some elements of the scatter/gather list are
+physically or virtually adjacent and an IOMMU maps them with a single
+entry).
 
 Please note that the sg cannot be mapped again if it has been mapped once.
 The mapping process is allowed to destroy information in the sg.