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Documentation: DMA API: Be more explicit that nents is always the same 

The nents argument to the DMA API functions operating on scatterlists is
always the same. The documentation used different argument names and the
matter was not mentioned in Documentation/DMA-API-HOWTO.txt at all. Fix
these.

Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
This commit is contained in:
Sakari Ailus 2015-09-23 14:41:09 +03:00 committed by Jonathan Corbet
parent c604503192
commit 7bc590b2fc
2 changed files with 8 additions and 3 deletions
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5
Documentation/DMA-API-HOWTO.txt
View File

@ -681,6 +681,11 @@ or:
as appropriate. 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 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_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 dma_map_*() call till dma_unmap_*(), then you don't have to call the

6
Documentation/DMA-API.txt
View File

@ -340,7 +340,7 @@ accessed sg->address and sg->length as shown above.
void void
dma_unmap_sg(struct device *dev, struct scatterlist *sg, dma_unmap_sg(struct device *dev, struct scatterlist *sg,
int nhwentries, enum dma_data_direction direction) int nents, enum dma_data_direction direction)
Unmap the previously mapped scatter/gather list. All the parameters Unmap the previously mapped scatter/gather list. All the parameters
must be the same as those and passed in to the scatter/gather mapping must be the same as those and passed in to the scatter/gather mapping
@ -356,10 +356,10 @@ void
dma_sync_single_for_device(struct device *dev, dma_addr_t dma_handle, size_t size, dma_sync_single_for_device(struct device *dev, dma_addr_t dma_handle, size_t size,
enum dma_data_direction direction) enum dma_data_direction direction)
void void
dma_sync_sg_for_cpu(struct device *dev, struct scatterlist *sg, int nelems, dma_sync_sg_for_cpu(struct device *dev, struct scatterlist *sg, int nents,
enum dma_data_direction direction) enum dma_data_direction direction)
void void
dma_sync_sg_for_device(struct device *dev, struct scatterlist *sg, int nelems, dma_sync_sg_for_device(struct device *dev, struct scatterlist *sg, int nents,
enum dma_data_direction direction) enum dma_data_direction direction)
Synchronise a single contiguous or scatter/gather mapping for the CPU Synchronise a single contiguous or scatter/gather mapping for the CPU