DMA-API.txt: fix description of pci_map_sg/dma_map_sg scatterlists handling

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

diff --git a/Documentation/DMA-API.txt b/Documentation/DMA-API.txt
index d8b63d164e41193927af2c7fb41dcb0893f57878..b462bb1495438b4854564151cdddb9b3c98e91a2 100644 (file)
--- 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).
        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.
@@ -337,7 +335,7 @@ With scatterlists, you use the resulting mapping like this:
        int i, count = dma_map_sg(dev, sglist, nents, direction);
        struct scatterlist *sg;
 
-       for (i = 0, sg = sglist; i < count; i++, sg++) {
+       for_each_sg(sglist, sg, count, i) {
                hw_address[i] = sg_dma_address(sg);
                hw_len[i] = sg_dma_len(sg);
        }