diff options
Diffstat (limited to 'kernel/Documentation/DMA-API-HOWTO.txt')
| -rw-r--r-- | kernel/Documentation/DMA-API-HOWTO.txt | 9 |
1 files changed, 7 insertions, 2 deletions
diff --git a/kernel/Documentation/DMA-API-HOWTO.txt b/kernel/Documentation/DMA-API-HOWTO.txt index aef8cc5a6..d69b3fc64 100644 --- a/kernel/Documentation/DMA-API-HOWTO.txt +++ b/kernel/Documentation/DMA-API-HOWTO.txt @@ -245,7 +245,7 @@ the case would look like this: if (!dma_set_mask_and_coherent(dev, DMA_BIT_MASK(64))) { using_dac = 1; - consistent_using_dac = 1; + consistent_using_dac = 1; } else if (!dma_set_mask_and_coherent(dev, DMA_BIT_MASK(32))) { using_dac = 0; consistent_using_dac = 0; @@ -358,7 +358,7 @@ There are two types of DMA mappings: transfer, unmapped right after it (unless you use dma_sync_* below) and for which hardware can optimize for sequential accesses. - This of "streaming" as "asynchronous" or "outside the coherency + Think of "streaming" as "asynchronous" or "outside the coherency domain". Good examples of what to use streaming mappings for are: @@ -681,6 +681,11 @@ or: as appropriate. +PLEASE NOTE: The 'nents' argument to dma_sync_sg_for_cpu() and + dma_sync_sg_for_device() must be the same passed to + dma_map_sg(). It is _NOT_ the count returned by + dma_map_sg(). + After the last DMA transfer call one of the DMA unmap routines dma_unmap_{single,sg}(). If you don't touch the data from the first dma_map_*() call till dma_unmap_*(), then you don't have to call the |