staging: unisys: Fix visorchannel.c block comments

[deliverable/linux.git] / Documentation / DMA-API-HOWTO.txt

diff --git a/Documentation/DMA-API-HOWTO.txt b/Documentation/DMA-API-HOWTO.txt
index 55b70b903ead2e95ce1226ef0fec3612bea67189..d69b3fc64e14e0427717efc5c505231c78acb5a6 100644 (file)
--- a/Documentation/DMA-API-HOWTO.txt
+++ b/Documentation/DMA-API-HOWTO.txt
@@ -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